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Sample records for aco rapido aisi

  1. Comparative study of AISI M3:2 high speed steel produced through different techniques of manufacturing; Estudo comparativo de acos rapidos AISI M3:2 produzidos por diferentes processos de fabricacao

    Araujo Filho, Oscar Olimpio de

    2006-07-01

    In this work AISI M3:2 high speed steels obtained through different techniques of manufacturing, submitted to the same heat treatment procedure were evaluated by measuring their mechanical properties of transverse rupture strength and hardness. Sinter 23 obtained by hot isostatic pressing (HIP), VWM3C obtained by the conventional route and a M3:2 high speed steel obtained by cold compaction of water atomized powders and vacuum sintered with and without the addition of a small quantity of carbon were evaluated after the same heat treatment procedure. The vacuum sintered M3:2 high speed steel can be an alternative to the more expensive high speed steel produced by hot isostatic pressing and with similar properties presented by the conventional one. The characterization of the vacuum sintered M3:2 high speed steel was performed by measuring the densities of the green compacts and after the sintering cycle. The sintering produced an acceptable microstructure and densities near to the theoretical. The transverse rupture strength was evaluated by means of three point bending tests and the hardness by means of Rockwell C and Vickers tests. The technique of scanning electronic microscopy (SEM) was used to evaluate the microstructure and to establish a relation with the property of transverse rupture strength. The structure was determined by means of X-ray diffraction (XRD) patterns and the retained austenite was detected to all the conditions of heat treatment. The main contribution of this work is to establish a relation between the microstructure and the mechanical property of transverse rupture strength and to evaluate the AISI M3:2 vacuum sintered high speed steel as an alternative to the similar commercial high speed steels. (author)

  2. Machining tools in AISI M2 high-speed steel obtained by spray forming process; Ferramentas de usinagem em aco rapido AISI M2 obtido por conformacao por 'spray'

    Jesus, Edilson Rosa Barbosa de. E-mail: erbjesus@usp.br

    2004-07-01

    The aim of the present work was the obtention of AISI M2 high-speed steel by spray forming technique and the material evaluation when used as machining tool. The obtained material was hot rolled at 50% and 72% reduction ratios, and from which it was manufactured inserts for machining tests. The performance of inserts made of the spray formed material was compared to inserts obtained from conventional and powder metallurgy (MP) processed materials. The spray formed material was chemical, physical, mechanical and microstructural characterised. For further characterisation, the materials were submitted to machining tests for performance evaluation under real work condition. The results of material characterisation highlight the potential of the spray forming technique, in the obtention of materials with good characteristics and properties. Under the current processing, hot rolling and heat treatments condition, the analysis of the results of the machining tests revealed a very similar behaviour among the tested materials. Proceeding a criterious analysis of the machining results tests, it was verified that the performance presented by the powder metallurgy material (MP) was slight superior, followed by conventional obtained material (MConv), which presented a insignificant advantage over the spray formed and hot rolled (72% reduction ratio) material. The worst result was encountered for the spray forming and hot rolled (50% reduction ratio) material that presented the highest wear values. (author)

  3. Modification and characterization of the AISI 410 martensitic stainless steels surface; Modificacao e caracterizacao da superficie do aco inoxidavel martensitico AISI 410

    Bincoleto, A.V.L. [Universidade Federal de Sao Carlos (PPG-CEM/UFSCar), SP (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Nascente, P.A.P. [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    Steam turbines are used in the generation of more than half the electric energy produced in the world nowadays. It is important the study which aims to improve the efficiency by means of the optimization of leaks and of the aerodynamic profiles, as well as to maintain the integrity of the components. The martensitic stainless steels are widely employed due to the combination of their good mechanical properties with higher corrosion resistance. However, their lower wear resistance and their poor tribological behavior limit their use, since they decrease the component life time. In order to evaluate the improvement in the performance of the AISI 410 stainless steel, several process of surface modification were employed. Five samples were produced: the first one was not treated, the second one received liquid nitriding, the third, gas nitriding, the forth, thermal aspersion of tungsten carbide, and the fifth, boronizing. The samples were characterized by optical microscopy, surface microhardness, and X-ray diffractometry. (author)

  4. Evaluation of performance of AISI 444 steel for application in distillation towers; Avaliacao do desempenho do aco AISI 444 para aplicacao como 'lining' em torres de destilacao

    Guimaraes, R.F.; Miranda, H.C. de; Farias, J.P. [Universidade Federal do Ceara (DEMM/UFC), Fortaleza, CE (Brazil). Dept. de Engenharia Metalurgica e de Materiais. Lab. de Caracterizacao de Materiais], e-mail: rf.guimaraes@yahoo.com.br

    2008-07-01

    In this work, the behavior of the AISI 444 ferritic stainless steel submitted to thermal fatigue test and their corrosion resistance in heavy crude oil was evaluated. The AWS E309MoL-16 and E316L-17 weld metal was employed as filler metal. Plates of the AISI 444 were welded on ASTM A-516 Gr. 60 plates and submitted to fatigue thermal cycle. Samples were extracted from plates welded and heat treated immersed in heavy crude oil at 300 deg C. Optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive of X-ray analysis (EDX) were used to characterize the microstructure and the corroded surface. The results show that the AISI 444 stainless steels did not present cracks after the thermal fatigue cycle and the heat treated immerse in heavy crude oil. The electrode AWS E309MoL-16 show better corrosion resistance than the AWS E316L-17. (author)

  5. Study of corrosion resistance of AISI 444 ferritic stainless steel for application as a biomaterial; Estudo da resistencia a corrosao do aco inoxidavel ferritico AISI 444 para aplicacao como biomaterial

    Marques, Rogerio Albuquerque

    2014-09-01

    Ferritic stainless steels are ferromagnetic materials. This property does not allow their use in orthopedic prosthesis. Nevertheless, in some specific applications, this characteristic is very useful, such as, for fixing dental and facial prostheses by using magnetic attachments. In this study, the corrosion resistance and cytotoxicity of the AISI 444 ferritic stainless steel, with low nickel content, extra-low interstitial levels (C and N) and Ti and Nb stabilizers, were investigated for magnetic dental attachments application. The ISO 5832-1 (ASTM F-139) austenitic stainless steel and a commercial universal keeper for dental attachment (Neo-magnet System) were evaluated for comparison reasons. The first stainless steel is the most used metallic material for prostheses, and the second one, is a ferromagnetic keeper for dental prostheses (NeoM). In vitro cytotoxicity analysis was performed by the red neutral incorporation method. The results showed that the AISI 444 stainless steel is non cytotoxic. The corrosion resistance was studied by anodic polarization methods and electrochemical impedance spectroscopy (EIS), in a saline phosphate buffered solution (PBS) at 37 °C. The electronic properties of the passive film formed on AISI 444 SS were evaluated by the Mott-Schottky approach. All tested materials showed passivity in the PBS medium and the passive oxide film presented a duplex nature. The highest susceptibility to pitting corrosion was associated to the NeoM SS. This steel was also associated to the highest dopant concentration. The comparatively low levels of chromium (nearly 12.5%) and molybdenum (0.3%) of NeoM relatively to the other studied stainless steels are the probable cause of its lower corrosion resistance. The NeoM chemical composition does not match that of the SUS444 standards. The AISI 444 SS pitting resistance was equivalent to the ISO 5832-1 pointing out that it is a potential candidate for replacement of commercial ferromagnetic alloys used

  6. Study of carbonitriding thermochemical treatment by plasma screen in active with pressures main austenitic stainless steels AISI 409 and AISI 316L; Estudo do tratamento termoquimico de carbonitretacao por plasma em tela ativa com pressoes variaveis nos acos inoxidaveis austenitico AISI 316L e ferririco AISI 409

    Melo, M.S.; Oliveira, A.M.; Leal, V.S.; Sousa, R.R.M. de; Alves Junior, C. [Centro Federal de Educacao Tecnologica do Maranhao (CEFET/MA), Sao Luis, MA (Brazil); Centro Federal de Educacao Tecnologica do Piaui (CEFET/PI), Teresina, PI (Brazil); Universidade Federal do Rio Grande do Norte (DF/UFRN), Natal, RN (Brazil). Dept. de Fisica. Labplasma

    2010-07-01

    The technique called Active Screen Plasma Nitriding (ASPN) is being used as an alternative once it offers several advantages with respect to conventional DC plasma. In this method, the plasma does not form directly in the sample's surface but on a screen, in such a way that undesired effects such as the edge effect is minimized. Stainless steels present not very satisfactory wearing characteristics. However, plasma carbonitriding has been used as to improve its resistance to wearing due to the formation of a fine surface layer with good properties. In this work, samples of stainless steel AISI 316L and AISI 409 were treated at pressures of 2.5 and 5 mbar. After the treatments they were characterized by microhardness, microscopy and Xray diffraction. Microscopy and hardness analysis showed satisfactory layers and toughness in those steels. (author)

  7. Pioneer ACO PUF

    U.S. Department of Health & Human Services — Pioneer ACO PUF - To address the increasing number of requests for Pioneer ACO data, the Centers for Medicare and Medicaid Services (CMS) has created a standard...

  8. Development of Nb{sub 2}O{sub 5}|Cu composite as AISI 1020 steel thermal spray coating for protection against corrosion by soil in buried structures; Desenvolvimento e uso do composito de Nb{sub 2}O{sub 5}|Cu como revestimento aplicado por aspersao termica sobre o aco AISI 1020 para protecao contra a corrosao pelo solo em estruturas enterradas

    Regis Junior, Oscar [Universidade Tecnologica Federal do Parana, Ponta Grossa, PR (Brazil). Dept. de Mecanica; Silva, Jose Maurilio da; Portella, Kleber Franke [Instituto de Tecnologia para o Desenvolvimento, Curitiba, PR (Brazil). Dept. de Pesquisa em Engenharia Civil; Paredes, Ramon Sigifredo Cortes, E-mail: regis@utfpr.edu.br [Universidade Federal do Parana, Curitiba, PR (Brazil). Dept. de Mecanica

    2012-07-01

    An Nb{sub 2}O|Cu corrosion-resistant coating was developed and applied onto AISI 1020 steel substrate by Powder Flame Spray. A galvanostatic electrochemical technique was employed, with and without ohmic drop, in four different soils (two corrosively aggressive and two less aggressive). Behavior of coatings in different soils was compared using a cathodic hydrogen reduction reaction (equilibrium potential, overvoltage and exchange current density) focusing on the effect of ohmic drop. Results allow recommendation of Nb{sub 2}O{sub 5}|Cu composite for use in buried structure protection. (author)

  9. Pioneer ACO Model

    U.S. Department of Health & Human Services — The Pioneer ACO Model is designed for health care organizations and providers that are already experienced in coordinating care for patients across care settings....

  10. Fluorescent lighting system of modified fast starting system; Sistema de alumbrado fluorescente de arranque rapido modificado

    Mendoza E, Ernesto J. [Manufacturera De Reactores, S. A., Mexico, D. F. (Mexico)

    1993-12-31

    This paper puts into perspective the possible energy saving in using hybrid ballasts for the operation of fast starting lamps. It presents in summarized form some fundamentals of the fluorescent lamps operation, as well as the fast starting modified systems. Also the results of field operation are shown, as well as the effects on the useful life of the lamp T12 as well as the T8. [Espanol] Este trabajo pone en perspectiva el ahorro de energia posible, al emplear balastros hibridos para operar lamparas de arranque rapido. Presenta en forma resumida algunos fundamentos de la operacion de lamparas fluorescentes, asi como de los sistemas de arranque rapido modificado. Se muestran tambien resultados de operacion de campo, asi como los efectos sobre la vida util de las lamparas, tanto T12 como T8.

  11. ASSESSMENT OF STOCK AND SPATIAL DISTRIBUTION OF SOLE (SOLEA SOLEA, L. IN ALBANIAN COAST USING RAPIDO TRAWL

    Enton Spaho

    2012-06-01

    Full Text Available Common sole (Solea solea Linnaeus, 1758 is still not a specific target of fishery in Albania, but it represents an important target of the mixed-species catches of bottom trawlers and set netters operating in the coastal areas in the upper part of Albanian Adriatic Sea. Sole landings are low, amounting very few tonnes, but the demand will likely increase in the next future, because of the high quality of the fish fillet and the increase of consumers demand for wild sea fish. In order to identify the spawning areas and assess the spatial distribution and biomass of this species a rapido trawl survey was performed in year 2007. The smallest specimens were mostly concentrated in the shallowest stratum and the largest ones between 30 and 100 m depth. Solea Stock Biomass (SSB was 354 t, corresponding to 64% of the overall population recorded at sea at that time. In the context of fisheries, the Albanian fishing fleet involve a number of different fishing gears, while rapido trawl is introduced recently. The special technical and operating characteristics of rapido trawl makes it very effective in sole fishery and less harmful for the sea benthos and the species inhabiting it. This study aimed the estimation of spatial distribution of common sole and its biomass in the Albanian coast using rapido trawl gear.

  12. The RAPIDOS project—European and Chinese collaborative research on biomaterials

    David Eglin

    2015-04-01

    Full Text Available The research project entitled “rapid prototyping of custom-made bone-forming tissue engineering constructs” (RAPIDOS is one of the three unique projects that are the result of the first coordinated call for research proposals in biomaterials launched by the European Union Commission and the National Natural Science Foundation of China in 2013 for facilitating bilateral translational research. We formed the RAPIDOS European and Chinese consortium with the aim of applying technologies creating custom-made tissue engineered constructs made of resorbable polymer and calcium phosphate ceramic composites specifically designed by integrating the following: (1 imaging and information technologies, (2 biomaterials and process engineering, and (3 biological and biomedical engineering for novel and truly translational bone repair solutions. Advanced solid free form fabrication technologies, precise stereolithography, and low-temperature rapid prototyping provide the necessary control to create innovative high-resolution medical implants. The use of Chinese medicine extracts, such as the bone anabolic factor icaritin, which has been shown to promote osteogenic differentiation of stem cells and enhance bone healing in vivo, is a safe and technologically relevant alternative to the intensely debated growth factors delivery strategies. This unique initiative driven by a global consortium is expected to accelerate scientific progress in the important field of biomaterials and to foster strong scientific cooperation between China and Europe.

  13. Including Language Access into Medicaid ACO Design.

    Gershon, Rachel; Morris, Lisa; Ferguson, Warren

    2016-09-01

    Quality health care relies upon communication in a patient's preferred language. Language access in health care occurs when individuals are: (1) Welcomed by providers regardless of language ability; and (2) Offered quality language services as part of their care. Federal law generally requires access to health care and quality language services for deaf and Limited English Proficient (LEP) patients in health care settings, but these patients still find it hard to access health care and quality language services.Meanwhile, several states are implementing Medicaid Accountable Care Organization (ACO) initiatives to reduce health care costs and improve health care quality. Alternative payment methods used in these initiatives can give Accountable Care Organizations more flexibility to design linguistically accessible care, but they can also put ACOs at increased financial risk for the cost of care. If these new payment methods do not account for differences in patient language needs, ACO initiatives could have the unintended consequence of rewarding ACOs who do not reach out to deaf and LEP communities or offer quality language services.We reviewed public documents related to Medicaid ACO initiatives in six states. Some of these documents address language access. More could be done, however, to pay for language access efforts. This article describes Medicaid ACO initiatives and explores how different payment tools could be leveraged to reward ACOs for increased access to care and quality language services. We find that a combination of payment tools might be helpful to encourage both access and quality. PMID:27587453

  14. Integrating III-V, Si, and polymer waveguides for optical interconnects: RAPIDO

    Aalto, Timo; Harjanne, Mikko; Offrein, Bert-Jan; Caër, Charles; Neumeyr, Christian; Malacarne, Antonio; Guina, Mircea; Sheehan, Robert N.; Peters, Frank H.; Melanen, Petri

    2016-03-01

    We present a vision for the hybrid integration of advanced transceivers at 1.3 μm wavelength, and the progress done towards this vision in the EU-funded RAPIDO project. The final goal of the project is to make five demonstrators that show the feasibility of the proposed concepts to make optical interconnects and packet-switched optical networks that are scalable to Pb/s systems in data centers and high performance computing. Simplest transceivers are to be made by combining directly modulated InP VCSELs with 12 μm SOI multiplexers to launch, for example, 200 Gbps data into a single polymer waveguide with 4 channels to connect processors on a single line card. For more advanced transceivers we develop novel dilute nitride amplifiers and modulators that are expected to be more power-efficient and temperatureinsensitive than InP devices. These edge-emitting III-V chips are flip-chip bonded on 3 μm SOI chips that also have polarization and temperature independent multiplexers and low-loss coupling to the 12 μm SOI interposers, enabling to launch up to 640 Gbps data into a standard single mode (SM) fiber. In this paper we present a number of experimental results, including low-loss multiplexers on SOI, zero-birefringence Si waveguides, micron-scale mirrors and bends with 0.1 dB loss, direct modulation of VCSELs up to 40 Gbps, +/-0.25μm length control for dilute nitride SOA, strong band edge shifts in dilute nitride EAMs and SM polymer waveguides with 0.4 dB/cm loss.

  15. Recent results of the ACO storage ring

    A permanent magnet undulator has been built and installed on the ACO Storage Ring. The undulator design, the spontaneous emission and gain of the system, as well as the laser induced bunch lengthening of the electron bunch, are presented. A low-loss optical cavity has been also recently built and operated on the ring. Its performance and the degradation problems of the mirrors are discussed. Amplification of the spontaneous emission stored in the optical cavity has been observed. Also, preliminary results on the operation of an optical klystron are reported and interpreted

  16. ALOHA Cabled Observatory (ACO): Acoustic Doppler Current Profiler (ADCP): Temperature

    National Oceanic and Atmospheric Administration, Department of Commerce — The University of Hawaii's ALOHA ("A Long-term Oligotrophic Habitat Assessment") Cabled Observatory (ACO) is located 100 km north of the island of Oahu, Hawaii (22...

  17. ALOHA Cabled Observatory (ACO): Acoustic Doppler Current Profiler (ADCP): Velocity

    National Oceanic and Atmospheric Administration, Department of Commerce — The University of Hawaii's ALOHA ("A Long-term Oligotrophic Habitat Assessment") Cabled Observatory (ACO) is located 100 km north of the island of Oahu, Hawaii (22...

  18. ACO-AFSA Algorithm in Function Optimization and Its Application

    Wang Shi Gang

    2016-01-01

    Full Text Available ACO and AFSA as two kinds of new intelligent bionic algorithm, has better robustness, and the design method is simple and easy to understand. At present, in many engineering fields, they have been a pivotal position, but there are some defects in solving function optimization problems. Because of the lack of pheromone in the initial stage of ACO, the speed of the solution is relatively slow, and AFSA has the advantages of strong global convergence ability and fast speed. In this paper, based on the advantages and disadvantages of ACO and AFSA, two kinds of algorithms are integrated, and the advantage is enhanced, a better optimization algorithm is put forward: ACO-AFSA. The initial solution and improved state transition probabilities are obtained by AFSA, and the basic ACO is improved, the congestion degree of AFSA is introduced in the algorithm, makes most of ants’ initial optimization will not be randomly selected at a strong crowding restrictions. Experimental results show that the new algorithm can get the optimal solution with less number of iterations, which greatly saves computation time, and has higher accuracy and better convergence performance. Engineering, computing the shortest distance between the surface and plane of the problem has also been good results, the experimental results are satisfactory.

  19. Improving Network Performance using ACO Based Redundant Link Avoidance Algorithm

    B. Chandra Mohan

    2010-05-01

    Full Text Available In the wide spread internet, response time and pocket loss are inappropriate due to network traffic, as a result the network efficiency becomes worst and the system provides poor Quality of Service (QoS. An optimal routing protocol, especially multipath may avoid such traffic in the network. But existing routing protocols, both single path and multi path, concentrates only on finding the routes based on any one or some set of metrics, that not always suitable for dynamic, cloud natured network environment. Ant Colony Optimization (ACO based multipath routing protocol was suggested as an alternate to this problem by many researchers. The multipath ACO also provides same set of link(s for the source to destination, so that traffic merging again becomes a critical problem. This paper proposes an optimal solution to avoid the problem of traffic merging in the network by removing redundant link in the route. The Proposed algorithm, called 'Redundant Link Avoidance (RLA algorithm', is an ACO based multi path routing methodology, avoiding copious link in the suggested routes of ACO multipath protocol.

  20. Characterization of AISI 4140 borided steels

    The present study characterizes the surface of AISI 4140 steels exposed to the paste-boriding process. The formation of Fe2B hard coatings was obtained in the temperature range 1123-1273 K with different exposure times, using a 4 mm thick layer of boron carbide paste over the material surface. First, the growth kinetics of boride layers at the surface of AISI 4140 steels was evaluated. Second, the presence and distribution of alloying elements on the Fe2B phase was measured using the Glow Discharge Optical Emission Spectrometry (GDOES) technique. Further, thermal residual stresses produced on the borided phase were evaluated by X-ray diffraction (XRD) analysis. The fracture toughness of the iron boride layer of the AISI 4140 borided steels was estimated using a Vickers microindentation induced-fracture testing at a constant distance of 25 μm from the surface. The force criterion of fracture toughness was determined from the extent of brittle cracks, both parallel and perpendicular to the surface, originating at the tips of an indenter impression. The fracture toughness values obtained by the Palmqvist crack model are expressed in the form KC(π/2) > KC > KC(0) for the different applied loads and experimental parameters of the boriding process.

  1. Corrosion of AISI 316 and AISI 304 stainless steel with iodine vapor

    The weight loss of stainless steel in corrosion with iodine vapor was studied at 500 to 10000C and an iodine vapor pressure range of 0.05 to 0.5 mm Hg, using a thermobalance. In the initial stage of corrosion, the weight loss rate is largely influenced by solution treatment or surface treatment; the induction period, observed for solution-treated samples, is shortened or eliminated by fission-fragment irradiation, ion-bombardment or mechanical polishing, and in some cases corrosion is even accelerated by the surface treatments. A constant weight loss region follows the initial stage of corrosion. In this region, the weight loss rate is not dependent on treatment to the samples, and has a linear relationship with the vapor pressure of iodine. The rate is the largest at about 800 and 7500C for AISI 316 s. s. and AISI 304 s. s. The rates in general are larger for AISI 304 s. s. than for AISI 316 s. s. below 7000C but almost the same above 8000C. Corrosion product layer is observed on the surface of the sample below 7000C. Based on these findings, the corrosion process is discussed. The deposition of corrosion product in a temperature gradient tube is also described

  2. An ACO approach for the Parallel Machines Scheduling Problem

    Gatica, Claudia R.; Esquivel, Susana Cecilia; Leguizamón, Guillermo

    2008-01-01

    The parallel machines scheduling problem (Pm) comprises the allocation of jobs on the system’s resources, i.e., a group of machines in parallel. The basic model consists of m identical machines and n jobs. The jobs are assigned according to resource availability following some allocation rule. In this work, we apply the Ant Colony Optimization (ACO) metaheuristic which includes in the construction solution process different specific heuristic to solve Pm for the minimization Maximum Tardiness...

  3. ACO in e-Learning: Towards an adaptive learning path

    Pushpa. M

    2012-03-01

    Full Text Available Today we are in an era where drastic advancements in networking and information technology are in action. The learning process has also taken these advancements, as a result of which e-learning came to thescene. Personalization in e-learning will improve the performance of the system. Recent researches are concentrating on providing adaptability to the learning management systems, depending upon the varying user needs and contexts. Adaptability can be provided at different levels .Providing an adaptive learning path according to the context of the learners’ is an important issue. An optimal adaptive learning path will help the learners in reducing the cognitive overload and disorientation, and thereby improving the efficiency of the Learning Management System (LMS. Ant Colony Optimization (ACO is a widely accepted technique since it provides an adaptive learning path to the learners. Meta-heuristic which is used in intelligent tutoring systems provides the learning path in an adaptive way. The most interesting feature of ACO is its adaptation and robustness in an environment where the learning materials and learners are changing frequently. In this paper we can have a look through the existing ACO approaches towards providing an adaptive learning path and an introduction towards an enhanced attribute ant for making the e-learning system more adaptive.

  4. ACO a Metaheuristic Technique for solving Network Problems and a Precise of Network Models

    Manila Pahwa

    2013-09-01

    Full Text Available With the growing importance of telecommunication and internet, more complex networked systems are being designed and developed. The challenges of dealing with vast complexity of networking problems such as load balancing, routing and network congestion accentuate the need of more sophisticated technique to solve these problems. Ant colony optimisation (ACO is one of the best and efficient solutions to cope up with these problems. This paper presents the following:- Theoretical study of Metaheuristic technique commonly named as Ant Colony Optimisation (ACO and how it is better than conventional algorithms, An Overview of ACO models and the reason behind being ACO better than other Conventional algorithms?

  5. Dolor mandibular de origen cardíaco

    MR Sáez Yuguero; A Bermejo Fenoll; JL Calvo Guirado; E. Álvarez Martínez

    2003-01-01

    En las complejas estructuras anatómicas orofaciales, asientan muchos procesos dolorosos. Las algias orofaciales más comunes tienen su origen a nivel dental, periodontal o en estructuras musculoesqueleticas. Sin embargo, el paciente puede manifestar dolor en esta región, bien en dientes o estructuras musculoesqueleticas, y la fuente originaria localizarse a distancia. A este tipo de dolor se le llama dolor heterotópico. Una posible fuente de dolor heterotópico es el dolor de origen cardíaco. E...

  6. A comparative study of mechanical and tribological properties of AISI-304 and AISI-316 submitted to glow discharge nitriding

    Fabiana Cristina Nascimento; Carlos Eugênio Foerster; Silvio Luiz Rutz da Silva; Carlos Mauricio Lepienski; Carlos José de Mesquita Siqueira; Clodomiro Alves Junior

    2009-01-01

    Mechanical and tribological properties os AISI 304 and AISI 316 stainless steels submited to glow discharge ion nitriding are reported.The atmosphere was 20:80 - N2:H2 with substrate temperatures ranging from 300 to 500 °C. Treatment at 300 °C produced expanded austenite (γN) in both steels. Increasing the temperature, the phases γ´-Fe4N and - Fe2+xN were present and the latter is the major phase for AISI 304. At 500 °C, the CrN phase was also identified in both steels. Hardnesses o...

  7. MODELO ACO PARA LA RECOLECCIÓN DE RESIDUOS POR CONTENEDORES ACO MODEL APPLIED TO THE WASTE COLLECTION BY CONTAINERS

    Eduardo Salazar Hornig

    2009-08-01

    Full Text Available ACO es una metaheurística inspirada en el comportamiento de las colonias de hormigas para solucionar problemas de optimización combinatoria, por medio de la utilización de agentes computacionales simples que trabajan de manera cooperativa y se comunican mediante rastros de feromona artificiales. En este trabajo se presenta un modelo para resolver el Problema de Recolección de Residuos Domiciliarios por Contenedores, el que aplica un concepto de secuencias parciales de recolección que deben ser unidas para minimizar la distancia total de recolección. El problema de unir las secuencias parciales se representa como un TSP, el que es resuelto mediante un algoritmo ACO. En base a recomendaciones de la literatura, se calibran experimentalmente los parámetros del algoritmo y se recomiendan rangos de valores que representan buenos rendimientos promedio. El modelo se aplica a un sector de recolección de la comuna de San Pedro de la Paz, Chile, obteniéndose rutas de recolección que reducen la distancia total recorrida respecto de la actual ruta utilizada y de la solución obtenida con otro modelo desarrollado previamente.ACO is a metaheuristic inspired in the behavior of natural ant colonies to solve combinatorial optimization problems, based on simple agents that work cooperatively communicating by artificial pheromone trails. In this paper a model to solve the municipal waste collection problem by containers is presented, which applies a concept of partial collection sequences that must be joined to minimize the total collection distance. The problem to join the partial collection sequences is represented as a TSP, which is solved by an ACO algorithm. Based on the literature, algorithm parameters are experimentally calibrated and range of variations that represents good average solutions are recommended. The model is applied to a waste collection sector of the San Pedro de la Paz commune in Chile, obtaining recollection routes with less total

  8. Effect of temperature on the level of corrosion caused by heavy petroleum on AISI 304 and AISI 444 stainless steel

    João Paulo Sampaio Eufrásio Machado; Cleiton Carvalho Silva; Ana Vládia Cabral Sobral-Santiago; Hosiberto Batista de Sant'Ana; Jesualdo Pereira Farias

    2006-01-01

    This work presents a study on the influence of national heavy petroleum in the corrosion of the AISI 444 and AISI 304 stainless steels in simulated refining operation conditions. The petroleum was first characterized through physicochemical analysis (density, fluidity point, viscosity, sulfur concentration). In an attempt to understand the corrosion effect of temperature and of the type of heating the referred types of steel thermal treatments were carried out at three levels of temperature (...

  9. Process Parameter Optimization of WEDM for AISI M2 & AISI H13 by Anova & Analytic Hierarchy Process

    Rajkamal Singh Banga; Mukesh Verma

    2014-01-01

    WEDM is a widely recognized unconventional material cutting process used to manufacture components with complex shapes and profiles of hard materials. In this thermal erosion process, there is no physical contact between the wire tool and work materials. AISI M2 and AISI H13 materials are taken for studyand molybdenum wire electrode diameter (0.18mm); experiment is conducted according to Taguchi‟s L16 OA, with input parameters as Peak current, Pulse on, Pulse off their respons...

  10. Physicians' Participation In ACOs Is Lower In Places With Vulnerable Populations Than In More Affluent Communities.

    Yasaitis, Laura C; Pajerowski, William; Polsky, Daniel; Werner, Rachel M

    2016-08-01

    Early evidence suggested that accountable care organizations (ACOs) could improve health care quality while constraining costs, and ACOs are expanding throughout the United States. However, if disadvantaged patients have unequal access to physicians who participate in ACOs, that expansion may exacerbate health care disparities. We examined the relationship between physicians' participation in both Medicare and commercial ACOs across the country and the sociodemographic characteristics of their likely patient populations. Physicians' participation in ACOs varied widely across hospital referral regions, from nearly 0 percent to over 85 percent. After we adjusted for individual physician and practice characteristics, we found that physicians who practiced in ZIP Code Tabulation Areas where a higher percentage of the population was black, living in poverty, uninsured, or disabled or had less than a high school education-compared to other areas-had significantly lower rates of ACO participation than other physicians. Our findings suggest that vulnerable populations' access to physicians participating in ACOs may not be as great as access for other groups, which could exacerbate existing disparities in health care quality. PMID:27503961

  11. Hospitals Participating In ACOs Tend To Be Large And Urban, Allowing Access To Capital And Data.

    Colla, Carrie H; Lewis, Valerie A; Tierney, Emily; Muhlestein, David B

    2016-03-01

    Relationships between physicians and hospitals have changed considerably over the past decade, as hospitals and physician groups have integrated and new public and private payment policies have created financial interdependence. The extent to which accountable care organizations (ACOs) involve hospitals in their operations may prove to be vitally important, because managing hospital care is a key part of improving health care quality and lowering cost growth. Using primary data on ACO composition and capabilities paired with hospital characteristics, we found that 20 percent of US hospitals were part of an ACO in 2014. Hospitals that were in urban areas, were nonprofit, or had a smaller share of Medicare patients were more likely to participate in ACOs, compared to hospitals that were in more rural areas, were for-profit or government owned, or had a larger share of Medicare patients, respectively. Qualitative data identified the following advantages of including a hospital in an ACO: the availability of start-up capital, advanced data sharing, and engagement of providers across the care continuum. Although the 63 percent of ACOs that included hospitals offered more comprehensive services compared to ACOs without hospitals, we found no differences between the two groups in their ability to manage hospital-related aspects of patient care. PMID:26953297

  12. MOEA/D-ACO: a multiobjective evolutionary algorithm using decomposition and AntColony.

    Ke, Liangjun; Zhang, Qingfu; Battiti, Roberto

    2013-12-01

    Combining ant colony optimization (ACO) and the multiobjective evolutionary algorithm (EA) based on decomposition (MOEA/D), this paper proposes a multiobjective EA, i.e., MOEA/D-ACO. Following other MOEA/D-like algorithms, MOEA/D-ACO decomposes a multiobjective optimization problem into a number of single-objective optimization problems. Each ant (i.e., agent) is responsible for solving one subproblem. All the ants are divided into a few groups, and each ant has several neighboring ants. An ant group maintains a pheromone matrix, and an individual ant has a heuristic information matrix. During the search, each ant also records the best solution found so far for its subproblem. To construct a new solution, an ant combines information from its group's pheromone matrix, its own heuristic information matrix, and its current solution. An ant checks the new solutions constructed by itself and its neighbors, and updates its current solution if it has found a better one in terms of its own objective. Extensive experiments have been conducted in this paper to study and compare MOEA/D-ACO with other algorithms on two sets of test problems. On the multiobjective 0-1 knapsack problem,MOEA/D-ACO outperforms the MOEA/D with conventional genetic operators and local search on all the nine test instances. We also demonstrate that the heuristic information matrices in MOEA/D-ACO are crucial to the good performance of MOEA/D-ACO for the knapsack problem. On the biobjective traveling salesman problem, MOEA/D-ACO performs much better than the BicriterionAnt on all the 12 test instances. We also evaluate the effects of grouping, neighborhood, and the location information of current solutions on the performance of MOEA/D-ACO. The work in this paper shows that reactive search optimization scheme, i.e., the "learning while optimizing" principle, is effective in improving multiobjective optimization algorithms. PMID:23757576

  13. Casting AISI 316 steel by gel cast

    The feasibility of producing AISI 316 steel components from their powders and avoiding their compaction is analyzed. A casting technique is tested that is similar to gel casting, used for ceramic materials. In the initial stage, the process consists of the formulation of a concentrated barbotine of powdered metal in a solution of water soluble organic monomers, which is cast in a mold and polymerized in situ to form a raw piece in the shape of the cavity. The process can be performed under controlled conditions using barbotines with a high monomer content from the acrylimide family. Then, the molded piece is slowly heated until the polymer is eliminated, and it is sintered at temperatures of 1160oC to 1300oC under a dry hydrogen atmosphere, until the desired densities are attained. The density and micro structure of the materials obtained are compared with those for the materials compacted and synthesized by the conventional processes. The preliminary results show the feasibility of the process for the production of certain kinds of structural components (CW)

  14. Optimization of tensile strength of friction welded AISI 1040 and AISI 304L steels according to statistics analysis (ANOVA)

    Kirik, Ihsan [Batman Univ. (Turkey); Ozdemir, Niyazi; Firat, Emrah Hanifi; Caligulu, Ugur [Firat Univ., Elazig (Turkey)

    2013-06-01

    Materials difficult to weld by fusion welding processes can be successfully welded by friction welding. The strength of the friction welded joints is extremely affected by process parameters (rotation speed, friction time, friction pressure, forging time, and forging pressure). In this study, statistical values of tensile strength were investigated in terms of rotation speed, friction time, and friction pressure on the strength behaviours of friction welded AISI 1040 and AISI 304L alloys. Then, the tensile test results were analyzed by analysis of variance (ANOVA) with a confidence level of 95 % to find out whether a statistically significant difference occurs. As a result of this study, the maximum tensile strength is very close, which that of AISI 1040 parent metal of 637 MPa to could be obtained for the joints fabricated under the welding conditions of rotation speed of 1700 rpm, friction pressure of 50 MPa, forging pressure of 100 MPa, friction time of 4 s, and forging time of 2 s. Rotation speed, friction time, and friction pressure on the friction welding of AISI 1040 and AISI 304L alloys were statistically significant regarding tensile strength test values. (orig.)

  15. Asthma-COPD Overlap Syndrome (ACOS): Single disease entity or not? Could exhaled nitric oxide be a useful biomarker for the differentiation of ACOS, asthma and COPD?

    Karampitsakos, Theodoros; Gourgoulianis, Konstantinos I

    2016-06-01

    Asthma and chronic obstructive pulmonary disease (COPD) represent two major public health problems. However, there is a significant proportion of patients with a mixed asthma-COPD phenotype. This condition is defined as asthma-COPD overlap syndrome (ACOS). Since there are no internationally accepted criteria for the diagnosis of that syndrome, its management remains difficult. Given the fact that patients with ACOS have an increased risk of exacerbation and hospitalization, there is a pressing need for a more targeted approach and better management. We propose that fractional exhaled nitric oxide (FeNO), a marker of eosinophilic inflammation, could help clinicians differentiate ACOS from asthma and COPD. We evaluate this hypothesis, using data derived from the existing literature. PMID:27142135

  16. The Impact Of Medicare ACOs On Improving Integration And Coordination Of Physical And Behavioral Health Care.

    Fullerton, Catherine A; Henke, Rachel M; Crable, Erica; Hohlbauch, Andriana; Cummings, Nicholas

    2016-07-01

    The accountable care organization (ACO) model holds the promise of reducing costs and improving the quality of care by realigning payment incentives to focus on health outcomes instead of service volume. One key to managing the total cost of care is improving care coordination for and treatment of people with behavioral health disorders. We examined qualitative data from ninety organizations participating in Medicare ACO demonstration programs from 2012 through 2015 to determine whether and how they focused on behavioral health care. These ACOs had mixed degrees of engagement in improving behavioral health care for their populations. The biggest challenges included a lack of behavioral health care providers, data availability, and sustainable financing models. Nonetheless, we found substantial interest in integrating behavioral health care into primary care across a majority of the ACOs. PMID:27385242

  17. Methodology to Optimize Manufacturing Time for a CNC Using a High Performance Implementation of ACO

    Oscar Montiel-Ross

    2012-10-01

    Full Text Available In this paper, an efficient methodology to generate optimal and/or quasi‐optimal sequences of G commands to minimize the manufacturing time is presented. Our solution starts from original G codes provided by application CAD/CAM software. Here, first we tackled the problem of reducing the time of the travel path for drilling of an industrial robotic manufacturing machine. The methodology can be easily implemented for free distribution or commercial CAD/CAM software without achieving any modification to it. Several experiments that demonstrate how this proposal can help to outperform solutions provided by application software are presented, consistent improvements around 62% were obtained. Moreover, for optimizing the time along the travel path, we present a high performance implementation of Ant Colonies (ACO known as Parallel ACO (P‐ACO that allows achieving the optimization task efficiently by speeding up the original ACO. A Graphical User Interface that integrates the whole process is shown.

  18. An ACO model for a non-stationary formulation of the single elevator problem

    Molina, Silvia; Leguizamón, Mario Guillermo; Alba Torres, Enrique

    2007-01-01

    The Ant Colony Optimization (ACO) metaheuristic is a bio-inspired approach for hard combinatorial optimization problems for stationary and non-stationary environments. In the ACO metaheuristic, a colony of artificial ants cooperate for finding high quality solutions in a reasonable time. An interesting example of a non-stationary combinatorial optimization problem is the Multiple Elevators Problem (MEP) which consists in finding a sequence of movements for each elevator to perform in a buildi...

  19. Comparative electrochemical study of 08H18N10T, AISI 304 and AISI 316L stainless steels

    The aim of this work was to determine the main characteristics of the passivation and surface oxidation of 08H18N10T, AISI304 and AISI316L stainless steels, which serve as structural materials of VVER and PWR nuclear reactors. With the help of electrochemical experiments these materials were ranked according to their resistance against uniform corrosion. The measurements were done as a function of temperature in the range between room temperature and 80 deg. C. A sample of 08H18N10T steel was irradiated in the Budapest research reactor. With cyclic voltammetry we found that AISI 304 exhibits a very large passivation peak as a classical example for passivation. The peak is much smaller for AISI 316L and it is very small for 08H18N10T. This implies that the native oxide layer on AISI 316L and 08H18N10T is more protective than on AISI 304. The 08H18N10T steel has the best protective passive oxide layer which forms already in air and it is very difficult to remove it even at negative potentials. By comparing impedance spectra of the various stainless steels results lead to the same conclusions we obtained from cyclic voltammetry. Our experimental results of the irradiated steel are in accord with the fact that neutron irradiation increases the number of defect sites within the oxide layer. We found that irradiation has no considerable effect on the active-to-passive transition process. The small variations in the alloy composition do not alter the transition process significantly, as well

  20. Comparative electrochemical study of 08H18N10T, AISI 304 and AISI 316L stainless steels

    Kerner, Zsolt; Horvath, Akos [KFKI Atomic Energy Research Institute, H-1525 Budapest 114, P.O. Box 49 (Hungary); Nagy, Gabor [KFKI Atomic Energy Research Institute, H-1525 Budapest 114, P.O. Box 49 (Hungary)], E-mail: nagyg@sunserv.kfki.hu

    2007-10-10

    The aim of this work was to determine the main characteristics of the passivation and surface oxidation of 08H18N10T, AISI304 and AISI316L stainless steels, which serve as structural materials of VVER and PWR nuclear reactors. With the help of electrochemical experiments these materials were ranked according to their resistance against uniform corrosion. The measurements were done as a function of temperature in the range between room temperature and 80 deg. C. A sample of 08H18N10T steel was irradiated in the Budapest research reactor. With cyclic voltammetry we found that AISI 304 exhibits a very large passivation peak as a classical example for passivation. The peak is much smaller for AISI 316L and it is very small for 08H18N10T. This implies that the native oxide layer on AISI 316L and 08H18N10T is more protective than on AISI 304. The 08H18N10T steel has the best protective passive oxide layer which forms already in air and it is very difficult to remove it even at negative potentials. By comparing impedance spectra of the various stainless steels results lead to the same conclusions we obtained from cyclic voltammetry. Our experimental results of the irradiated steel are in accord with the fact that neutron irradiation increases the number of defect sites within the oxide layer. We found that irradiation has no considerable effect on the active-to-passive transition process. The small variations in the alloy composition do not alter the transition process significantly, as well.

  1. The study on the properties of AISI 4140 and AISI 1040 steel rods welded by friction welding

    Thanee Toomprasen; Chawalit Thinvongpituk; Sukangkana Talangkun

    2014-01-01

    This paper is aimed to investigate the properties of joint between AISI 4140 and AISI 1040 welded by friction welding. The specimens were prepared in round shape of 13 mm diameter and 100 mm long. They were welded by friction welding method under the following conditions; friction pressure of 183 MPa, friction time of 12 sec, upset pressure of 428 MPa, upset time of 7 sec. and rotational speed of 1400 rpm. The strength and hardness were tested on the welded area. The result showed finer grain...

  2. Investigation of residual stress in laser welding between carbon steel AISI 1010 and stainless AISI 304

    The dissimilar materials union has the residual stress formation as one of the most critical problems, which occurs mainly because these materials have both different thermal expansion coefficients and thermal conductivities. In this study, it was investigated the laser welding technique between steels, AISI 1010 and AISI 304. The materials were joined by butt autogenous welding with a continuous Nd:YAG laser. The main objective was to identify the welding parameters influence by the residual stresses analysis in the heat affected zone (HAZ). It was executed a factorial design with three-factor at two levels with a replica, which were varied power, welding speed and focal position of the laser beam. Residual stress measurements by the diffraction of X-rays were performed on the sample surface, to study their variation as a function of the parameters investigated. The blind hole method was also used to evaluate the residual stress along the samples depth, up to depth of 1mm. Besides residual stress measurement, weld seams were evaluated by optical and scanned electron microscopy, which were aimed to determine the weld geometry and changes in the microstructure. It was also made Vickers hardness measurements to evaluate the extent of HAZ. To evaluate the mechanical properties of the union were performed tensile and fatigue test. The MINITAB 15 software was used to analyze the residual stresses obtained by the blind hole method at different depths of the HAZ. It was also used statistical regression based on both the influences different and the combination of this input factors, in the residual stress of union. The results indicate that the models can satisfactorily predict the responses and provide users a guide to better define the welding parameters. (author)

  3. CACONET: Ant Colony Optimization (ACO) Based Clustering Algorithm for VANET

    Bajwa, Khalid Bashir; Khan, Salabat; Chaudary, Nadeem Majeed; Akram, Adeel

    2016-01-01

    A vehicular ad hoc network (VANET) is a wirelessly connected network of vehicular nodes. A number of techniques, such as message ferrying, data aggregation, and vehicular node clustering aim to improve communication efficiency in VANETs. Cluster heads (CHs), selected in the process of clustering, manage inter-cluster and intra-cluster communication. The lifetime of clusters and number of CHs determines the efficiency of network. In this paper a Clustering algorithm based on Ant Colony Optimization (ACO) for VANETs (CACONET) is proposed. CACONET forms optimized clusters for robust communication. CACONET is compared empirically with state-of-the-art baseline techniques like Multi-Objective Particle Swarm Optimization (MOPSO) and Comprehensive Learning Particle Swarm Optimization (CLPSO). Experiments varying the grid size of the network, the transmission range of nodes, and number of nodes in the network were performed to evaluate the comparative effectiveness of these algorithms. For optimized clustering, the parameters considered are the transmission range, direction and speed of the nodes. The results indicate that CACONET significantly outperforms MOPSO and CLPSO. PMID:27149517

  4. Dolor mandibular de origen cardíaco

    MR Sáez Yuguero

    2003-10-01

    Full Text Available En las complejas estructuras anatómicas orofaciales, asientan muchos procesos dolorosos. Las algias orofaciales más comunes tienen su origen a nivel dental, periodontal o en estructuras musculoesqueleticas. Sin embargo, el paciente puede manifestar dolor en esta región, bien en dientes o estructuras musculoesqueleticas, y la fuente originaria localizarse a distancia. A este tipo de dolor se le llama dolor heterotópico. Una posible fuente de dolor heterotópico es el dolor de origen cardíaco. Este articulo presenta un caso clínico en el que el dolor mandibular bilateral fue el síntoma inicial de una cardiopatía isquémica que fue erróneamente etiquetada de artrosis de la articulación temporomandibular.In the complex orofacial anatomic structures, many painful processes are felt. The most common orofacial pains have their origin at dental or periodontal level, or in muscle -skeletical structures. However, the patient can have pain in this area- either in teeth or muscle-eskeletical structures- and the originating source can be located at a distance. This type of pain is called heterotopic pain. A possible source of heterotopic pain is the pain of cardiac origin. This paper presents a clinical case in which the bilateral mandibular pain is the initial symptom of an ischemic cardiopathy that was erroneously labeled as temporomandibular arthrosis.

  5. CACONET: Ant Colony Optimization (ACO) Based Clustering Algorithm for VANET.

    Aadil, Farhan; Bajwa, Khalid Bashir; Khan, Salabat; Chaudary, Nadeem Majeed; Akram, Adeel

    2016-01-01

    A vehicular ad hoc network (VANET) is a wirelessly connected network of vehicular nodes. A number of techniques, such as message ferrying, data aggregation, and vehicular node clustering aim to improve communication efficiency in VANETs. Cluster heads (CHs), selected in the process of clustering, manage inter-cluster and intra-cluster communication. The lifetime of clusters and number of CHs determines the efficiency of network. In this paper a Clustering algorithm based on Ant Colony Optimization (ACO) for VANETs (CACONET) is proposed. CACONET forms optimized clusters for robust communication. CACONET is compared empirically with state-of-the-art baseline techniques like Multi-Objective Particle Swarm Optimization (MOPSO) and Comprehensive Learning Particle Swarm Optimization (CLPSO). Experiments varying the grid size of the network, the transmission range of nodes, and number of nodes in the network were performed to evaluate the comparative effectiveness of these algorithms. For optimized clustering, the parameters considered are the transmission range, direction and speed of the nodes. The results indicate that CACONET significantly outperforms MOPSO and CLPSO. PMID:27149517

  6. Colloquium on Large Scale Improvement: Implications for AISI

    McEwen, Nelly, Ed.

    2008-01-01

    The Alberta Initiative for School Improvement (AISI) is a province-wide partnership program whose goal is to improve student learning and performance by fostering initiatives that reflect the unique needs and circumstances of each school authority. It is currently ending its third cycle and ninth year of implementation. "The Colloquium on Large…

  7. RNA Interference of 1-Aminocyclopropane-1-carboxylic Acid Oxidase (ACO1 and ACO2 Genes Expression Prolongs the Shelf Life of Eksotika (Carica papaya L. Papaya Fruit

    Rogayah Sekeli

    2014-06-01

    Full Text Available The purpose of this study was to evaluate the effectiveness of using RNA interference in down regulating the expression of 1-aminocyclopropane-1-carboxylic acid oxidase gene in Eksotika papaya. One-month old embryogenic calli were separately transformed with Agrobacterium strain LBA 4404 harbouring the three different RNAi pOpOff2 constructs bearing the 1-aminocyclopropane-1-carboxylic acid oxidase gene. A total of 176 putative transformed lines were produced from 15,000 calli transformed, selected, then regenerated on medium supplemented with kanamycin. Integration and expression of the targeted gene in putatively transformed lines were verified by PCR and real-time RT-PCR. Confined field evaluation of a total of 31 putative transgenic lines planted showed a knockdown expression of the targeted ACO1 and ACO2 genes in 13 lines, which required more than 8 days to achieve the full yellow colour (Index 6. Fruits harvested from lines pRNAiACO2 L2-9 and pRNAiACO1 L2 exhibited about 20 and 14 days extended post-harvest shelf life to reach Index 6, respectively. The total soluble solids contents of the fruits ranged from 11 to 14° Brix, a range similar to fruits from non-transformed, wild type seed-derived plants.

  8. The study on the properties of AISI 4140 and AISI 1040 steel rods welded by friction welding

    Thanee Toomprasen

    2014-06-01

    Full Text Available This paper is aimed to investigate the properties of joint between AISI 4140 and AISI 1040 welded by friction welding. The specimens were prepared in round shape of 13 mm diameter and 100 mm long. They were welded by friction welding method under the following conditions; friction pressure of 183 MPa, friction time of 12 sec, upset pressure of 428 MPa, upset time of 7 sec. and rotational speed of 1400 rpm. The strength and hardness were tested on the welded area. The result showed finer grains. in the welded area. This is the result of friction pressure and upset pressure in the welding process. In addition, the observation result indicated some changes of Ferrite and Pearlite in welded zone. This phase change resulted in the increment of hardness in AISI 4140 at the contact area and adjacent. In part of AISI 1040, the portion of Pearlite and Ferrite are not significantly changed, therefore the value of hardness is almost constant.

  9. A comparative study of mechanical and tribological properties of AISI-304 and AISI-316 submitted to glow discharge nitriding

    Fabiana Cristina Nascimento

    2009-06-01

    Full Text Available Mechanical and tribological properties os AISI 304 and AISI 316 stainless steels submited to glow discharge ion nitriding are reported.The atmosphere was 20:80 - N2:H2 with substrate temperatures ranging from 300 to 500 °C. Treatment at 300 °C produced expanded austenite (γN in both steels. Increasing the temperature, the phases γ´-Fe4N and - Fe2+xN were present and the latter is the major phase for AISI 304. At 500 °C, the CrN phase was also identified in both steels. Hardnesses of about 13-14 GPa at near surface regions were obtained in both steels. Moreover, AISI 316 nitrided at 500 °C has the deepest hard layer. Tribological tests showed that wear can be reduced by up to a factor of six after the nitriding processes, even for a working temperature of 300 °C. The profiles during and after nanoscratch tests did not reveal significant differences after nitriding processes in both steels.

  10. Process Parameter Optimization of WEDM for AISI M2 & AISI H13 by Anova & Analytic Hierarchy Process

    Rajkamal Singh Banga

    2014-10-01

    Full Text Available WEDM is a widely recognized unconventional material cutting process used to manufacture components with complex shapes and profiles of hard materials. In this thermal erosion process, there is no physical contact between the wire tool and work materials. AISI M2 and AISI H13 materials are taken for studyand molybdenum wire electrode diameter (0.18mm; experiment is conducted according to Taguchi‟s L16 OA, with input parameters as Peak current, Pulse on, Pulse off their response on MRR, Surface Roughness, Kerf width & Spark Gap is analysed to check the significance of each using ANOVA. Process parameter optimization is done by Analytic Hierarchy Process with the criteria Maximum MRR, minimum kerf and surface roughness. It is observed that for material AISI M2 at low value of peak current (1 A, pulse off (20µs and pulse on (30µs we can minimize surface roughness (3.30µm, kerf width (0.195 mm and maximize MRR (0.022 g/min,from the selected levels whereas for material AISI H13 Peak current (1A, Pulse On (40µs and high Pulse Off (30µs we get better Surface roughness (3.71 µm, kerf width (0.196mm and maximum MRR (0.020g/min, from the selected levels.

  11. MGA trajectory planning with an ACO-inspired algorithm

    Ceriotti, Matteo; Vasile, Massimiliano

    2010-11-01

    Given a set of celestial bodies, the problem of finding an optimal sequence of swing-bys, deep space manoeuvres (DSM) and transfer arcs connecting the elements of the set is combinatorial in nature. The number of possible paths grows exponentially with the number of celestial bodies. Therefore, the design of an optimal multiple gravity assist (MGA) trajectory is a NP-hard mixed combinatorial-continuous problem. Its automated solution would greatly improve the design of future space missions, allowing the assessment of a large number of alternative mission options in a short time. This work proposes to formulate the complete automated design of a multiple gravity assist trajectory as an autonomous planning and scheduling problem. The resulting scheduled plan will provide the optimal planetary sequence and a good estimation of the set of associated optimal trajectories. The trajectory model consists of a sequence of celestial bodies connected by two-dimensional transfer arcs containing one DSM. For each transfer arc, the position of the planet and the spacecraft, at the time of arrival, are matched by varying the pericentre of the preceding swing-by, or the magnitude of the launch excess velocity, for the first arc. For each departure date, this model generates a full tree of possible transfers from the departure to the destination planet. Each leaf of the tree represents a planetary encounter and a possible way to reach that planet. An algorithm inspired by ant colony optimization (ACO) is devised to explore the space of possible plans. The ants explore the tree from departure to destination adding one node at the time: every time an ant is at a node, a probability function is used to select a feasible direction. This approach to automatic trajectory planning is applied to the design of optimal transfers to Saturn and among the Galilean moons of Jupiter. Solutions are compared to those found through more traditional genetic-algorithm techniques.

  12. Relative Study of CGS with ACO and BCO Swarm Intelligence Techniques

    T.Hashni

    2012-09-01

    Full Text Available Swarm intelligence is the collective-level, problem-solving behavior of groups of relatively simple agents.Local interactions among agents, either direct or indirect through the environment, are fundamental for theemergence of swarm intelligence. Ant Colony Optimization (ACO is a swarm based meta-heuristic method that isinspired by the behavior of real ant colonies. Bee Colony Optimization (BCO meta-heuristic belongs to the groupof Swarm Intelligence techniques. Consultant Guided Search (CGS is a new hybrid meta heuristic, which combinesnew ideas with concepts found in Ant colony Optimization (ACO, Bee Colony Optimization (BCO technique. Thispaper presents comparative study of CGS, ACO, BCO techniques and the flexibility of CGS.

  13. Experimental evaluation of mechanical properties of friction welded AISI steels

    Amit Handa

    2014-12-01

    Full Text Available In the present study, an experimental setup was designed and fabricated in order to accomplish friction welded joints between austenitic stainless steel and low-alloy steel. Thereafter, the effect of axial pressures on the mechanical properties of friction welded AISI 304 with AISI 1021 steels, produced by mechanical joining, have been investigated. Samples were welded under different axial pressures ranging from 75 to 135 MPa, at constant speed of 1250 rpm. The tensile strength, impact strength, and micro-hardness values of the weldments were determined and evaluated. Simultaneously, the fractrography of the tensile-tested specimens were carried out, so as to understand the failure analysis.

  14. Weldability of AISI 304 to copper by friction welding

    Kirik, Ihsan [Batman Univ. (Turkey); Balalan, Zulkuf [Firat Univ., Elazig (Turkey)

    2013-06-01

    Friction welding is a solid-state welding method, which can join different materials smoothly and is excessively used in manufacturing industry. Friction welding method is commonly used in welding applications of especially cylindrical components, pipes and materials with different properties, for which other welding methods remain incapable. AISI 304 stainless steel and a copper alloy of 99.6 % purity were used in this study. This couple was welded in the friction welding machine. After the welding process, samples were analyzed macroscopically and microscopically, and their microhardness was measured. Tensile test was used to determine the bond strength of materials that were joined using the friction welding method. At the end of the study, it was observed that AISI 304 stainless steel and copper could be welded smoothly using the friction welding method and the bond strength is close to the tensile strength of copper. (orig.)

  15. Magnetic Barkhausen emission in lightly deformed AISI 1070 steel

    Capo Sanchez, J., E-mail: jcapo@cnt.uo.edu.cu [Departamento de Fisica, Facultad de Ciencias Naturales, Universidad de Oriente, Av. Patricio Lumumba s/n, 90500 Santiago de Cuba (Cuba); Campos, M.F. de [EEIMVR-Universidade Federal Fluminense, Av. dos Trabalhadores 420, Vila Santa Cecilia, 27255-125 Volta Redonda, RJ (Brazil); Padovese, L.R. [Departamento de Engenharia Mecanica, Escola Politecnica, Universidade de Sao Paulo, Av. Prof. Mello Moraes, 2231, 05508-900 Sao Paulo (Brazil)

    2012-01-15

    The Magnetic Barkhausen Noise (MBN) technique can evaluate both micro- and macro-residual stresses, and provides indication about the relevance of contribution of these different stress components. MBN measurements were performed in AISI 1070 steel sheet samples, where different strains were applied. The Barkhausen emission is also analyzed when two different sheets, deformed and non-deformed, are evaluated together. This study is useful to understand the effect of a deformed region near the surface on MBN. The low permeability of the deformed region affects MBN, and if the deformed region is below the surface the magnetic Barkhausen signal increases. - Highlights: > Evaluated residual stresses by the magnetic Barkhausen technique. > Indication about the relevance of micro-and macro-stress components. > Magnetic Barkhausen measurements were carried out in AISI 1070 steel sheet samples. > Two different sheets, deformed and non-deformed, are evaluated together. > Magnetic Barkhausen signal increases when deformed region is below the surface.

  16. Low temperature plasma carburizing of AISI 316L austenitic stainless steel and AISI F51 duplex stainless steel Cementação sob plasma à baixa temperatura do aço inoxidável austenítico AISI 316L e do aço inoxidável duplex AISI F51

    Carlos Eduardo Pinedo; André Paulo Tschiptschin

    2013-01-01

    In this work an austenitic AISI 316L and a duplex AISI F51 (EN 1.4462) stainless steel were DC-Plasma carburized at 480ºC, using CH4 as carbon carrier gas. For the austenitic AISI 316L stainless steel, low temperature plasma carburizing induced a strong carbon supersaturation in the austenitic lattice and the formation of carbon expanded austenite (γC) without any precipitation of carbides. The hardness of the carburized AISI 316L steel reached a maximum of 1000 HV due to ∼13 at% c...

  17. Hot forming of AISI A2 tool steel

    Večko Pirtovšek, T.; Peruš, I.; Kugler, G.; Turk, R.; M. Terčelj

    2008-01-01

    For further increase of economy of production of AISI A2 tool steel a study of possibility of expanding the hot working range and better prediction of flow stress has been carried out. By employing hot compression tests it was proved, that initial microstructures have influence on the lower limit and chemical composition on upper limit of hot working range. A CAE Neural Networks was applied to predict the flow stresses for intermediate values of strain rates and temperatures. For optimization...

  18. Corrosion under stress of AISI 304 steel in thiocyanate solutions

    Corrosion susceptibility under stress of AISI 304 steel sensitized in a sodium thiocyanate solution has been studied and results were compared with those obtained with solutions of thiosulfate and tetrathionate. Sensitized steel type 304 is highly susceptible to corrosion when under intergranular stress (IGSCC) in thiocyanate solutions but the aggressiveness of this anion is less than that of the other sulphur anions studied (thiosulfate and tetrathionate). This work has been partly carried out in the Chemistry Department. (Author)

  19. An investigation on fatigue life of borided AISI 1010 steel

    O.N. Celik

    2009-01-01

    Full Text Available Purpose: This study aims to investigate the fatigue life of box borided AISI 1010 steel materials.Design/methodology/approach: Fatigue specimens firstly have been prepared according to ASTM E466-96 standard and normalized. Then their surfaces have been cleaned by polishing. Boriding heat treatment has been applied in solid media with the help of Ekabor2 powder. Specimens have been borided at 1173-1223-1273 and 1323 K temperatures for 2-4 and 6 hours respectively. Fatigue tests have been made in rotating-bend test device. Separate S-N diagram has been formed for each boriding condition and then their results were compared with the results of the specimens on which any heat treatment has not been made.Findings: As a result it has been seen that boriding has no positive effect on fatigue life of AISI 1010 steel materials. And also it has been determined that fatigue life of the materials on which boriding heat treatment applied, decreases in between 14 %-55 %.Research limitations/implications: It can be noted that the reasons of short fatigue life determination are the boride layer’s much higher hardness than the substrate material’s, and the micro cracks existed between boride phases formed onto the surface.Originality/value: The investigations on fatigue life of borided AISI 1010 steel were made.

  20. An improved adaptive ACO meta heuristic for scheduling multimedia traffic across the 802.11e EDCA

    Ditze, Michael; Becker, Markus

    2008-01-01

    This paper presents an adaptive near-optimal scheduler for multimedia traffic for the 802.11e Enhanced Distributed Channel Access (EDCA) medium access control scheme. The scheduler exploits the ant colony optimization (ACO) meta heuristic to tackle the challenge of packet scheduling. ACO is a biologically inspired algorithm that is known to find near-optimal solutions for combinatorial optimization problems. Thus, we expect that ACO scheduling produces more efficient schedules than comparable deterministic scheduling approaches at the expenses of a computational overhead it introduces. We compare ACO scheduling relevant deterministic scheduling approaches, and in particular the MLLF scheduler that is specifically designed for the needs of compressed multimedia applications. The purpose of the evaluation is twofold. It allows to draw conclusions on the feasibility of ACO scheduling for multimedia traffic while it serves as a benchmark to determine to what extent deterministic schedulers fall short of a near-optimal solution.

  1. Effect of temperature on the level of corrosion caused by heavy petroleum on AISI 304 and AISI 444 stainless steel

    João Paulo Sampaio Eufrásio Machado

    2006-06-01

    Full Text Available This work presents a study on the influence of national heavy petroleum in the corrosion of the AISI 444 and AISI 304 stainless steels in simulated refining operation conditions. The petroleum was first characterized through physicochemical analysis (density, fluidity point, viscosity, sulfur concentration. In an attempt to understand the corrosion effect of temperature and of the type of heating the referred types of steel thermal treatments were carried out at three levels of temperature (200, 300 and 400 °C. The procedure was done in conditions close to those in the distillation column. Heat was gradually increased from room temperature, and directly heated to working temperature. Each treatment took 4 hours to be completed. Scanning electronic microscopy (SEM and the analysis of X rays dispersive energy (EDX were used after the trials to characterize the samples. The results show that treatment temperature, as well as the type of heating, has distinct influences on each type of steel.

  2. Postharvest Analysis of Lowland Transgenic Tomato Fruits Harboring hpRNAi-ACO1 Construct

    Bita Behboodian

    2012-01-01

    Full Text Available The plant hormone, ethylene, is an important regulator which involved in regulating fruit ripening and flower senescence. In this study, RNA interference (RNAi technology was employed to silence the genes involved in ethylene biosynthetic pathway. This was achieved by blocking the expression of specific gene encoding the ACC oxidase. Initially, cDNA corresponding to ACO1 of lowland tomato cultivar (MT1, which has high identity with ACO1 of Solanum lycopersicum in GenBank, was cloned through RT-PCR. Using a partial coding region of ACO1, one hpRNAi transformation vector was constructed and expressed ectopically under the 35S promoter. Results showed that transgenic lines harboring the hpRNA-ACO1 construct had lower ethylene production and a longer shelf life of 32 days as compared to 10 days for wild-type fruits. Changes in cell wall degrading enzyme activities were also investigated in cases where the transgenic fruits exhibited reduced rates of firmness loss, which can be associated with a decrease in pectin methylesterase (PME and polygalacturonase (PG activities. However, no significant change was detected in both transgenic and wild-type fruits in terms of β-galactosidase (β-Gal activity and levels of total soluble solid, titratable acid and ascorbic acid.

  3. ACO Based Feature Subset Selection for Multiple k-Nearest Neighbor Classifiers

    Shailendra Kumar Shrivastava

    2011-05-01

    Full Text Available The k-nearest neighbor (k-NN is one of the most popular algorithms used for classification in various fields of pattern recognition & data mining problems. In k-nearest neighbor classification, theresult of a new instance query is classified based on the majority of k-nearest neighbors. Recently researchers have begun paying attention to combining a set of individual k-NN classifiers, each using adifferent subset of features, with the hope of improving the overall classification accuracy. In this paper we proposed Ant Colony Optimization (ACO based feature subset selection for multiple k-nearest neighbor classifiers. The ACO is an iterative meta-heuristic search technique, which inspired by the foraging food behavior of real ant colonies. In ACO, real ants become artificial ants with the particular abilities such as distance determination & tour memory. The solution is constructed in a probabilistic waybased on pheromone model in the form of numerical values. The concept of this approach is selecting the best possible subsets of feature from the original set with the help of ACO and combines the outputs from multiple k-NN classifiers. The experimental results show that this proposed method improves the average classification accuracy of k-NN classifier.

  4. Squeeze Casting Method Of AI-Si Alloy For Piston Material

    The AI-Si alloy is an alloy used as piston material. This alloys could be as AI-Si hypereutectic alloy (Si content more than 12.5 % wt.), as AI-Si eutectic alloy (Si cuntent 12.5 % wt, and as AI-Si hypoeutectic alloy (Si content less than 12.5 % wt.). The synthesize of AI-Si alloy piston generally using the technique of gravity casting in a dies. This method is causing high porousity. By using the squeeze technique, amount ofporousity in AI-Si alloy is possibly reduced and the density of this alloy should be higher. The other factors such as alloying elements of AI-Si alloy (Mg. Cu, Zn) would increase the mechanical properties especially the hardness. The focuses of this research are the microstructure and the maximum hardness during the heat treatment of AI-Si alloy which was added by alloying elments. The result of hardness at test shows the maximum hardness at 94.7 kg/mm2 obtained at aging temperature of 210oC for hours with homogenous dendritic microstructure

  5. Plasma nitriding of AISI 304L and AISI 316L stainless steels: effect of time in the formation of S phase and the chromium nitrides

    Plasma nitriding can improve hardness and wear resistance of austenitic stainless steels without losses in corrosion resistance. This fact relies on a nitrided layer constituted only by S phase, without chromium nitrides precipitation. In this work, the effect of nitriding time on phases formed on nitrided layer was investigated in two austenitic stainless steels: AISI 304L e AISI 316L. The samples were nitrided at 420 deg C, using a mixture of 60 % N2 and 40% H2, during 5, 7 and 9 hours. It was noted that chromium nitrides were formed on samples of AISI 304L, nitrided for 7 e 9 hours, while all nitrided samples of AISI 316L showed only formation of S phase. The nitrided layers were characterized using optical microscope and x-ray diffraction. (author)

  6. Microstructural Characteristic of Dissimilar Welded Components (AISI 430 Ferritic-AISI 304 Austenitic Stainless Steels) by CO2 Laser Beam Welding (LBW)

    Caligulu, Ugur; Dikbas, Halil; Taskin, Mustafa

    2012-01-01

    In this study, microstructural characteristic of dissimilar welded components (AISI 430 ferritic-AISI 304 austenitic stainless steels) by CO2 laser beam welding (LBW) was investigated. Laser beam welding experiments were carried out under argon and helium atmospheres at 2000 and 2500 W heat inputs and 100-200-300 cm/min. welding speeds. The microstructures of the welded joints and the heat affected zones (HAZ) were examined by optical microscopy, SEM, EDS and XRD analysis. The tensile strengt...

  7. Effects of X-rays Radiation on AISI 304 Stainless Steel Weldings with AISI 316L Filler Material: A Study of Resistance and Pitting Corrosion Behavior

    Francisco Javier Cárcel-Carrasco; Manuel Pascual-Guillamón; Miguel Angel Pérez-Puig

    2016-01-01

    This article investigates the effect of low-level ionizing radiation, namely X-rays, on the micro structural characteristics, resistance, and corrosion resistance of TIG-welded joints of AISI 304 austenitic stainless steel made using AISI 316L filler rods. The welds were made in two different environments: natural atmospheric conditions and a closed chamber filled with inert argon gas. The influence of different doses of radiation on the resistance and corrosion characteristics of the welds i...

  8. Mössbauer studies on an AISI 1137 type steel

    E Güler; H Akta

    2006-06-01

    An AISI 1137 type medium carbon steel was studied by means of scanning electron microscopy and Mössbauer spectroscopy. This steel in as received state at room temperature was ferritic. Different heat treatments on related steel exhibited different microstructures such as pearlite and bainite. Also magnetism of these product phases was determined as 32.7 T and 32.6 T relatively where ferromagnetism of ferritic phase in as received state was 33.05 T. Mössbauer parameters such as isomer shifts and % volumes were also determined before and after transformations.

  9. Aluminum coating by fluidized bed chemical vapor deposition on austenitic stainless steels AISI 304 and AISI 316

    Jose Luddey Marulanda-Arevalo

    2015-01-01

    Full Text Available Los revestimientos de aluminio f ueron depositados sobre aceros inoxidables AISI 304 y AISI 316 en el rango de temperatura de 5 60 a 600 °C por deposición química de vapor en lecho fluidizado(CVD – FBR. Se utilizó un lecho que consistía en 10 % de aluminio en polvo y 90 % de lecho inerte (alúmina, el cual fue fluidizado con Ar y como ga ses activadores se utilizó una mezcla de ácido clorhídrico con hidrógeno (HCl/H 2 . En el recubrimiento si n tratamiento térmico están las siguiente s especies: Al 13 Fe 4 , Fe 2 Al 5 , FeAl 2 y Al 5 FeNi, las cuales están presentes para ambos aceros. Además, el tratamiento térmico provoca la difusa de alu minio hacia el sustrato y la difusa de hierro del sustrato haci a la superficie del recubrimiento, haciendo la trans formación de los compuestos ant eriores a FeAl, Fe 2 Al 5 , FeAl 2 , Al 0.99 Fe 0.99 Ni 0.02 , AlNi y el Fe 2 AlCr. Se realizó la simulación termodinámica con el s oftware Thermo Calc para obt ener información de la posible composición y la cantidad de mat erial depositado, para condiciones seleccionadas. Las muestras recubi ertas y sin recubrir, se expus ieron a 750 ºC en una atmósfera d onde el vapor agua se transporta a las muestras usando un flujo de N 2 de 40 ml/min, más 100 % vapor de agua (H 2 O. Los dos sustratos sin revestir se comportaron de manera diferente, ya que el acero AISI 304 soportó bien el a taque y ganó poco peso (0.49 mg/cm 2 , en comparación con el acero AISI 316 que perdió mucho peso (25.4 mg/cm 2 . Los aceros recubiertos ganaron poco de peso durante las mil horas de exposición (0.26 mg/cm 2 y soportaron muy bien el ataque corrosivo en c omparación con sustratos sin r ecubrimiento.

  10. Fiber laser welding of AISI 304 stainless steel plates

    Compared with conventional lasers, fiber laser welding is characterized by high melting efficiency, deferent keyhole modes and power density characteristics, which could affect the heat and melt flow of the molten pool during welding. The objective of the present work was to study the fiber laser weldability of 5 mm thick AISI 304 austenitic stainless steel plates; therefore, bead-on-plate welding was exploited on AISI 304 stainless steel plates with different laser powers, welding speeds, defocused distances with different types of shielding gas and their effects on the weld zone geometry and properties and final solidification microstructure at room temperature. Laser power, welding speed and defocused distance have a great effect on the bead appearance and weld zone shape while almost no significant effect on both the type of microstructure and mechanical properties of welds. The microstructure of all laser welds was always austenitic including about 3-5 % ferrite. However, the lower the laser power and/or the higher the welding speed, the finer solidification structure, primary ferrite or mixed-mode solidification resulted in crack-free welds. (author)

  11. In pile AISI 316L. Low cycle fatigue. Final report

    In pile testing of the effect of neutron irradiation on the fatigue life of the reference material AISI 316L was performed in the framework of the European fusion technology program. The overall programme, carried out at SCK CEN (Mol,Belgium), exists of two instrumented rigs for low cycle fatigue testing, which were consecutively loaded in the BR-2 reactor during periods Jan (94) June (94) and Aug (94)-Dec(94). In each experiment, two identical samples were loaded by means of a pneumatically driven system. The samples were instrumented with thermocouples, strain gages, linear variable displacement transducers, and activation monitors. The experimental conditions are given. Type of fatigue test: load controlled, symmetric, uniaxial, triangular wave shape; stress range: about 580 MPa; sample shape: hourglass, diameter 3.2 mm, radius 12.5 mm; environment: NaK (peritectic); temperature: 250 C; maximum dpa value up to fracture: 1.7. Two of four samples were broken (one in each experiment) after having experienced 17 419 respectively 11 870 stress cycles. These new data points confirm earlier results from pile fatigue tests: irradiation causes no degradation of fatigue life of AISI 316L steel, at least for the parameters corresponding to these experiments

  12. New data association technique based on ACO with directional information considered

    2008-01-01

    Due to the advantages of ant colony optimization (ACO) in solving complex problems, a new data association algorithm based on ACO in a cluttered environment called DACDA is proposed. In the proposed method, the concept for tour and the length of tour are redefined. Additionally, the directional information is incorporated into the proposed method because it is one of the most important factors that affects the performance of data association. Kalraan filter is employed to estimate target states. Computer simulation results show that the proposed method could carry out data association in an acceptable CPU time, and the correct data association rate is higher than that obtained by the data association (DA) algorithm not combined with directional information.

  13. A Novel Framework Based on ACO and PSO for RNA Secondary Structure Prediction

    Gang Wang

    2013-01-01

    Full Text Available Prediction of RNA structure is a useful process for creating new drugs and understanding genetic diseases. In this paper, we proposed a particle swarm optimization (PSO and ant colony optimization (ACO based framework (PAF for RNA secondary structure prediction. PAF consists of crucial stem searching (CSS and global sequence building (GSB. In CSS, a modified ACO (MACO is used to search the crucial stems, and then a set of stems are generated. In GSB, we used a modified PSO (MPSO to construct all the stems in one sequence. We evaluated the performance of PAF on ten sequences, which have length from 122 to 1494. We also compared the performance of PAF with the results obtained from six existing well-known methods, SARNA-Predict, RnaPredict, ACRNA, PSOfold, IPSO, and mfold. The comparison results show that PAF could not only predict structures with higher accuracy rate but also find crucial stems.

  14. Experimental evaluation of a R134a/CO2 cascade refrigeration plant

    Sanz Kock, Carlos; Llopis Doménech, Rodrigo; Sánchez García-Vacas, Daniel; Cabello López, Ramón; Torrella Alcaraz, Enrique

    2014-01-01

    We present the experimental evaluation of a R134a/CO2 cascade refrigeration plant designed for low evaporation temperature in commercial refrigeration applications. The test bench incorporates two single- stage vapour compression cycles driven by semi hermetic compressors coupled thermally through two brazed plate cascade heat exchangers working in parallel and controlled by electronic expansion valves. The experimental evaluation (45 steady-states) covers evaporating temperatures from -40 to...

  15. Relative Study of CGS with ACO and BCO Swarm Intelligence Techniques

    T.Hashni; T Amudha

    2012-01-01

    Swarm intelligence is the collective-level, problem-solving behavior of groups of relatively simple agents.Local interactions among agents, either direct or indirect through the environment, are fundamental for theemergence of swarm intelligence. Ant Colony Optimization (ACO) is a swarm based meta-heuristic method that isinspired by the behavior of real ant colonies. Bee Colony Optimization (BCO) meta-heuristic belongs to the groupof Swarm Intelligence techniques. Consultant Guided Search (CG...

  16. Ant Colony Optimization ACO For The Traveling Salesman Problem TSP Using Partitioning

    Alok Bajpai; Raghav Yadav

    2015-01-01

    Abstract An ant colony optimization is a technique which was introduced in 1990s and which can be applied to a variety of discrete combinatorial optimization problem and to continuous optimization. The ACO algorithm is simulated with the foraging behavior of the real ants to find the incremental solution constructions and to realize a pheromone laying-and-following mechanism. This pheromone is the indirect communication among the ants. In this paper we introduces the partitioning technique ba...

  17. Tailoring Systems Engineering Processes in a Conceptual Design Environment: A Case Study at NASA Marshall Spaceflight Center's ACO

    Mulqueen, John; Maples, C. Dauphne; Fabisinski, Leo, III

    2012-01-01

    This paper provides an overview of Systems Engineering as it is applied in a conceptual design space systems department at the National Aeronautics and Space Administration (NASA) Marshall Spaceflight Center (MSFC) Advanced Concepts Office (ACO). Engineering work performed in the NASA MFSC's ACO is targeted toward the Exploratory Research and Concepts Development life cycle stages, as defined in the International Council on Systems Engineering (INCOSE) System Engineering Handbook. This paper addresses three ACO Systems Engineering tools that correspond to three INCOSE Technical Processes: Stakeholder Requirements Definition, Requirements Analysis, and Integration, as well as one Project Process Risk Management. These processes are used to facilitate, streamline, and manage systems engineering processes tailored for the earliest two life cycle stages, which is the environment in which ACO engineers work. The role of systems engineers and systems engineering as performed in ACO is explored in this paper. The need for tailoring Systems Engineering processes, tools, and products in the ever-changing engineering services ACO provides to its customers is addressed.

  18. PERFORMANCE STUDY ON AISI316 AND AISI410 USING DIFFERENT LAYERED COATED CUTTING TOOLS IN CNC TURNING

    K. RAJA

    2015-01-01

    Full Text Available Stainless steel (SS is used for many commercial and industrial applications owing to its high resistance to corrosion. It is too hard to machine due to its high strength and high work hardening property. A surface property such as surface roughness (SR is critical to the function-ability of machined components. SS is generally regarded as more difficult to machine material and poor SR is obtained during machining. In this paper an attempt has been made to investigate the SR produced by CNC turning on austenitic stainless steel (AISI316 and martensitic stainless steel (AISI410 by different cases of coated cutting tool used at dry conditions. Multilayered coated with TiCN/Al2O3, multilayered coated with Ti(C, N, B and single layered coated with TiAlN coated cutting tools are used. Experiments were carried out by using Taguchi’s L27 orthogonal array. The effect of cutting parameters on SR is evaluated and optimum cutting conditions for minimizing the SR are determined. Analysis of variance (ANOVA is used for identifying the significant parameters affecting the responses. Confirmation experiments are conducted to validate the results obtained from optimization.

  19. De la Locura de doble forma a la Psicosis maníaco-depresiva.

    - Consejo de Redacción

    1995-01-01

    Full Text Available Sin entrar en polémicas sobre a quién atribuir la primera descripción de lo que actualmente llamamos Psicosis maníaco-depresiva, es decir, sin tomar partido por Baillarger o J.-P. Falret, lo cierto es que a mediados del pasado siglo los alienistas franceses orquestaron un saber nosológico en el que se reunían en una única categoría dos manifestaciones extremas del humor: la manía y la melancolía. Tras las descripciones fundacionales de Baillarger y de Falret, fechadas ambas en el mismo año, 1854, se abrió un espacio nosológico opuesto al terreno de los delirios crónicos: las psicosis del humor frente a las psicosis de la razón, o bien psicosis maníaco-depresiva frente a esquizofrenia-paranoia. De la última cosecha del nosógrafo por excelencia, Emil Kraepelin, proviene la descripción clínica más completa y matizada de la locura maníaco-depresiva (das manisch-depressive Irresein. Dos años después, en 1915, S. Freud mostró en Duelo y Melancolía la infraestructura metapsicológica de la manía y de la melancolía.

  20. Predicting coal ash fusion temperature based on its chemical composition using ACO-BP neural network

    Coal ash fusion temperature is important to boiler designers and operators of power plants. Fusion temperature is determined by the chemical composition of coal ash, however, their relationships are not precisely known. A novel neural network, ACO-BP neural network, is used to model coal ash fusion temperature based on its chemical composition. Ant colony optimization (ACO) is an ecological system algorithm, which draws its inspiration from the foraging behavior of real ants. A three-layer network is designed with 10 hidden nodes. The oxide contents consist of the inputs of the network and the fusion temperature is the output. Data on 80 typical Chinese coal ash samples were used for training and testing. Results show that ACO-BP neural network can obtain better performance compared with empirical formulas and BP neural network. The well-trained neural network can be used as a useful tool to predict coal ash fusion temperature according to the oxide contents of the coal ash

  1. Solving optimum operation of single pump unit problem with ant colony optimization (ACO) algorithm

    For pumping stations, the effective scheduling of daily pump operations from solutions to the optimum design operation problem is one of the greatest potential areas for energy cost-savings, there are some difficulties in solving this problem with traditional optimization methods due to the multimodality of the solution region. In this case, an ACO model for optimum operation of pumping unit is proposed and the solution method by ants searching is presented by rationally setting the object function and constrained conditions. A weighted directed graph was constructed and feasible solutions may be found by iteratively searching of artificial ants, and then the optimal solution can be obtained by applying the rule of state transition and the pheromone updating. An example calculation was conducted and the minimum cost was found as 4.9979. The result of ant colony algorithm was compared with the result from dynamic programming or evolutionary solving method in commercial software under the same discrete condition. The result of ACO is better and the computing time is shorter which indicates that ACO algorithm can provide a high application value to the field of optimal operation of pumping stations and related fields.

  2. Enfermedad inflamatoria intestinal en pacientes celíacos Inflammatory bowel disease in celiac patients

    M. Masachs

    2007-08-01

    Full Text Available Introducción: se ha sugerido una potencial asociación entre la enfermedad celíaca y la enfermedad inflamatoria intestinal, que puede justificar que ambas enfermedades puedan presentarse en un mismo enfermo o en sus familiares de primer orden con mayor frecuencia de lo esperado. Objetivo: determinar la prevalencia de la enfermedad de Crohn y la colitis ulcerosa en los enfermos celíacos y en sus familiares. Método: estudio epidemiológico prospectivo transversal en un grupo de pacientes celíacos, sus familiares de primer grado y un grupo control de características epidemiológicas similares, constituido por familiares de pacientes que acuden al Servicio de Urgencias por un problema agudo. Para detectar la existencia de colitis ulcerosa y enfermedad de Crohn en los celíacos y sus familiares, se realizó una entrevista semiestructurada. Resultados: se han incluido 86 celíacos y 432 familiares, que se han comparado con 809 controles (129 pacientes con una enfermedad aguda y 680 familiares de primer grado suyos. Se han detectado 3 casos de enfermedad de Crohn en el grupo de los enfermos celíacos y 4 casos de enfermedad de Crohn en sus familiares. Sólo se ha detectado 1 caso de enfermedad de Crohn en el grupo control (p Introduction: a potential association between celic disease and inflammatory bowel disease hs been suggested, which may explain the fact that both disorders occasionally present in one patient or in his/her first-degree relatives more frequently than expected. Objective: to establish the prevalence of Crohn's disease and ulcerative colitis in celiac patients and their relatives. Method: a cross-sectional, prospective epidemiological study in a group of celiac patients, their first-degree relatives, and a control group with similar epidemiological characteristics including the relatives of patients presenting at the ER for acute conditions. A semistructured interview was used to identify the presence of Crohn's disease and

  3. Computer Aided Design of Heat Treatment for AISI P20+Ni Mold Steel with Good Machinability

    HU Xin-bin; GAO Wen; HE Yan-lin; LI Lin

    2004-01-01

    Computer aided design of heat treatment for AISI P20 mold steel with good machinability is attempted to proceed by the commercial software package Thermo-Calc (TCP+DICTRA). Through experimental and theoretical analysis of phase transformation during heat treatment, further knowledge of designing proper heat treatment is obtained. Then the machinability of AISI P20+Ni steel under given heat treatment condition is studied and the influencing factors to their machinability are analyzed. It is shown that heat treatment designed by computer simulation of carbide transformation is applicable to AISI P20+Ni steel with good machinability; AISI P20+Ni steel with tempered sorbite treated by quenching &tempering has optimal machinability; normalizing at the temperature of 910℃ & tempering can avoid cracking and result in acceptable machinability in small thickness module.

  4. Fractographic studies of hydrogen embrittlement of AISI 316L austenitic stainless steel

    This paper concerns a fractographic examination of hydrogen embrittlement of a stable AISI 316L type austenitic stainless steel. The objective is a better understanding of the possible role of hydrogen in stress corrosion cracking processes. (author)

  5. Hot forming of AISI A2 tool steel

    T. Večko Pirtovšek

    2008-10-01

    Full Text Available For further increase of economy of production of AISI A2 tool steel a study of possibility of expanding the hot working range and better prediction of flow stress has been carried out. By employing hot compression tests it was proved, that initial microstructures have influence on the lower limit and chemical composition on upper limit of hot working range. A CAE Neural Networks was applied to predict the flow stresses for intermediate values of strain rates and temperatures. For optimization purposes the activation energies and constants of the hyperbolic sine function for two temperatures ranges (850-1000°C and 1000-1150°C were calculated.

  6. CO2 laser welding of AISI 321stainless steel

    CO2 laser welding of AISI 321austenitic stainless steel has been carried out. Bead on plate welds on 2 mm thick steel were performed with 450W CO2 laser at speeds ranging from 200 to 900 mm/min. It was observed that weld depth and width was decreased with increasing the speed at constant laser power. Butt welds on different sheet thickness of 1, 2 and 2.5 mm were performed with laser power of 450 W and at speed 750, 275 and 175 mm/min, respectively. The microstructures of the welded joints and the heat affected zones (HAZ) were examined by optical microscopy and SEM. The austenite/delta ferrite microstructure was reported in the welded zone. The microhardness and tensile strength of the welded joints were measured and found almost similar to base metal due to austenitic nature of steel

  7. Radiation-induced phase development in AISI 316

    During irradiation at temperatures between 460 and 6500C, the alloy AISI 316 decomposes into an austenite matrix of altered composition and some mixture of six possible precipitate phases. These phases are γ', G, eta-silicide, M23C6, M6C, and Laves. The balance of phases developed is exceptionally sensitive to a large number of material and environmental variables and frequently varies within a single grain. All of these phases are found to be either naturally rich in nickel and silicon or to become progressively enriched in these elements as the irradiation proceeds. The precipitates can be considered to be classified as thermally stable but modified, irradiation-enhanced, irradiation-induced, and irradiation-transformed

  8. Simulation of Thermo-viscoplastic Behaviors for AISI 4140 Steel

    Li, Hong-Bin; Feng, Yun-Li

    2016-04-01

    The thermo-viscoplastic behaviors of AISI 4140 steel are investigated over wide ranges of strain rate and deformation temperature by isothermal compression tests. Based on the experimental results, a unified viscoplastic constitutive model is proposed to describe the hot compressive deformation behaviors of the studied steel. In order to reasonably evaluate the work hardening behaviors, a strain hardening material constant (h0) is expressed as a function of deformation temperature and strain rate in the proposed constitutive model. Also, the sensitivity of initial value of internal variable s to the deformation temperature is discussed. Furthermore, it is found that the initial value of internal variable s can be expressed as a linear function of deformation temperature. Comparisons between the measured and predicted results confirm that the proposed constitutive model can give an accurate and precise estimate of the inelastic stress-strain relationships for the studied high-strength steel.

  9. Corrosion of AISI 304 stainless steel in polluted seawater

    The sequence of microbiofouling settlement on AISI 304 stain steel samples exposed to polluted harbor sea water of a power cooling water intake is studied. The firts sates of bacterial colonization are followed by means of scanning electron microscopy during two weeks of exposure. The relation between microbiofouling and corrosion is also followed by scanning electron microscopy and evaluated through electrochemical polarization experiments. The results obtained show that microbial colonization and extracellular polimeric substances forming the biofilms have a marked influence on the electrochemical behaviour of stainless steel in sea water. Laboratory experiments using inorganic chloride solutions or artificial sea water show a considerably lesser attack of the metal than those performed 'in situ' with natural sea water. Passivity breadown is highly facilitated when complex biological and inorganic deposits (fouling) have settled on the metal surface. (Author)

  10. Pileup Behavior in Sharp Nanoindentation of AISI 1045 Steel

    Zhu, L. N.; Xu, B. S.; Wang, H. D.; Wang, C. B.

    Experimental measurements have been used to investigate the pileup behavior during nanoindentation with a sharp indenter. The AISI 1045 steels treated by quenching and annealing were examined. The results show that during sharp nanoindentation process, the amount of pileup is related to the residual stress state, the indentation depth and the work hardening. The quenched steel with compressive residual stress will tend to pile up, and the stress-free annealed steel can decrease the pileup height. It is found that the pileup height gradually increases for the two steels as the indentation depth becomes larger. It is also shown that the low work hardening of the two steels can also result in the pileup deformation.

  11. Stress Ratio Effect on Ratcheting Behavior of AISI 4340 Steel

    Divya Bharathi, K.; Dutta, K.

    2016-02-01

    Ratcheting is known as accumulation of plastic strain during asymmetric cyclic loading of metallic materials under non-zero mean stress. This phenomenon reduces fatigue life of engineering materials and thus limits the life prediction capacity of Coffin-Manson relationship. This study intends to investigate the ratcheting behavior in AISI 4340 steel which is mainly used for designing of railway wheel sets, axles, shafts, aircraft components and other machinery parts. The effect of stress ratio on the ratcheting behaviour in both annealed and normalised conditions were investigated for investigated steel. Ratcheting tests were done at different stress ratios of -0.4, -0.6 and -0.8. The results showed that the material responds to hardening behavior and nature of strain accumulation is dependent on the magnitude of stress ratio. The post ratcheted samples showed increase in tensile strength and hardness which increases with increasing stress ratio and these variations in tensile properties are correlated with the induced cyclic hardening.

  12. Study of discordancy mobility in the AISI 304 steel

    Internal Friction (IF), measurements were carried out in a type AISI 304 austenitic stainless steels at approximately 1HZ of frequency in the temperature interval from 120 to 573K. The IF spectra and the vibration frequency were obtained in samples were submitted to specific heat treatments. The results showed IF spectra with a well defined peak at 260K. The intensity dependes on the amount of plastic deformation previously introduced in the sample. Another broad peak was detected between 300 and 400K. Both peaks could only be detected after plastic deformation in uniaxial tension or torsion. In torsionably deformed samples at liquid nitrogen temperature, 77 K, the IF spectrum is observed only after linear annealing at 400K. This apparently results from a high damping due to a possible phase transformation which occurs around room temperature. The broad peak at higher temperature is sensitive to recovery induced by linear annealings. (Author)

  13. Comportamiento termomecánico de aceros AISI 304

    El Wahabi, M.

    2001-04-01

    Full Text Available The hot deformation behaviour of three AISI 304 (H, L and HP austenitic stainless steel with different carbon contents has been studied. An analysis of the parameters describing their hot flow curves was carried out. No heavy effect of the carbon content was found on most of the latter parameters. However, the work hardening and dynamic recovery behaviour showed clear differences depending on the given alloy, especially at high temperatures and low strain rates where the high carbon steel displayed larger work hardening and dynamic recovery rates than the other steels. The high purity steel (interstitial free displayed the lower stress levels as its hardening rate was slower than in the other two steels.

    Se llevó a cabo un estudio del comportamiento termomecánico de tres aceros inoxidables austeníticos tipo AISI 304 (H, L y HP con diferentes contenido en carbono, mediante la determinación de los parámetros que describen las etapas de deformación en caliente. No se notó un fuerte efecto del carbono en dichos parámetros, excepto en los que describen los procesos de endurecimiento y de restauración dinámica que muestran una cierta dependencia con la composición química, especialmente a bajos valores del parámetro de Zener-Hollomon, donde el acero de alto carbono (304H endurece y restaura más rápido que el de bajo carbono (304L, alcanzándose valores de tensión de pico similares en ambos casos. El material de alta pureza (libre de intersticiales toma valores de tensión de pico más bajos que los otros aceros, endureciendo más lentamente y con una velocidad de restauración similar a la del 304H.

  14. Linear friction welding of AISI 316L stainless steel

    Research highlights: → Linear friction welding is a feasible process for joining AISI316L. → Most welds had tensile strengths superior to the parent material. → Welding parameters had a significant impact on weld microstructure. → Control of microstructure by controlling welding parameters is a process benefit. - Abstract: Linear friction welding is a solid state joining process established as a niche technology for the joining of aeroengine bladed disks. However, the process is not limited to this application, and therefore the feasibility of joining a common engineering austenitic steel, AISI 316L, has been explored. It was found that mechanically sound linear friction welds could be produced in 316L, with tensile properties in most welds exceeding those of the parent material. The mechanical properties of the welds were also found to be insensitive to relatively large changes in welding parameters. Texture was investigated in one weld using high energy synchrotron X-ray diffraction. Results showed a strong {1 1 1} type texture at the centre of the weld, which is a typical shear texture in face centre cubic materials. Variations in welding parameters were seen to have a significant impact on the microstructures of welds. This was particularly evident in the variation of the fraction of delta ferrite, in the thermo-mechanically affected zone of the welds, with different process parameters. Analysis of the variation in delta ferrite, with different welding parameters, has produced some interesting insights into heat generation and dissipation during the process. It is hoped that a greater understanding of the process could help to make the parameter optimisation process, when welding 316L as well as other materials, more efficient.

  15. Kepekaan Retak Korosi Tegangan Baja Tahan Karat Austenitik AISI 304 Dalam Lingkungan Air Laut Buatan

    Daud, Marzuki

    2012-01-01

    The component of AISI 304 stainless steel construction is used as a prop of linking up the ropes on the boat on the sea, such as socket swaged, chain plate, turnbuckle, and so on. This component usually has a failure problem of Stress Corrosion Cracking (SCC) although the stress which operates mechanically is far from its yield strength. The aim of this research is to analyze the SCC susceptibility of AISI 304 austenite stainless steel in artificial sea water which is represent...

  16. Texture evolution in thin-sheets on AISI 301 metastable stainless steel under dynamic loading

    Kim, K.Y. [Posco Steels, Pohan, South Korea (Korea, Republic of); Kozaczek, K. [Oak Ridge National Lab., TN (United States); Kulkarni, S.M. [TRW Vehicle Safety Systems, Mesa, AZ (United States); Bastias, P.C.; Hahn, G.T. [Vanderbilt Univ., Nashville, TN (United States)

    1995-05-08

    The evolution of texture in thin sheets of metastable austenitic stainless steel AISI 301 is affected by external conditions such as loading rate and temperature, by inhomogeneous deformation phenomena such as twinning and shear band formation, and by the concurent strain induced phase transformation of the retained austenitc ({gamma}) into martensite ({alpha}). The present paper describes texture measurements on different gauges of AISI 301 prior and after uniaxial stretching under different conditions.

  17. Resistencia al desgaste de recubrimientos Fe-Nb-Cr-W, Nb, AISI 1020 y AISI 420 producidos por proyección térmica por arco eléctrico

    López-Covaleda, E. A.; Mercado-Velandia, J. L.; Olaya-Flórez, J. J.

    2013-01-01

    The commercial materials 140MXC (with iron, tungsten, chrome, niobium), 530AS (AISI 1015 steel) and 560AS (AISI 420 steel) on AISI 4340 steel were deposited using thermal spray with arc. The aim of work was to evaluate the best strategy abrasive wear resistance of the system coating-substrate using the following combinations: (1) homogeneous coatings and (2) coatings depositing simultaneously 140MXC + 530AS and 140MXC + 560AS. The coatings microstructure was characterized using Optical micros...

  18. Study on residual stress of AISI304 TIG welding line with laser shock processing by x-ray stress analyzer

    Zhang, Y. K.; Kong, D. J.; Yin, S. M.; Feng, A. X.; Lu, J. Z.; Ge, T.

    2006-02-01

    The surface of AISI304 TIG welding line was processed by LSP (laser shock processing). The effects on the microstructure, hardness and residual stress of AISI304 welding line by LSP were observed, and its mechanical properties were researched by SEM (scanning electron microscope) and test device of mechanical property. Residual stresses of AISI304 TIG welding line by LSP were measured with Model X-350A X ray analyzer. The test results show that compressive residual stress values of AISI304 TIG welding line by LSP are about 110MPa. Strengthening effects of AISI304 TIG welding line by LSP is very obvious, and fatigue properties of welding line is improved, and tensile residual stresses of welding line are obviously reduced, the distribution of residual stress tends to equality, and service life of AISI304 TIG welding line is improved.

  19. Breakdown and evolution of the protective oxide scales of AISI 304 and AISI 316 stainless steels under high-temperature oxidation

    Habib, K. A.; Damra, M. S.; Saura, J. J.; Cervera, I.; Bellés, J.

    2011-01-01

    The failure of the protective oxide scales of AISI 304 and AISI 316 stainless steels has been studied and compared at 1,000°C in synthetic air. First, the isothermal thermogravimetric curves of both stainless steels were plotted to determine the time needed to reach the breakdown point. The different resistance of each stainless steel was interpreted on the basis of the nature of the crystalline phases formed, the morphology, and the surface structure as well as the cross-section structure of...

  20. Corrosion and microstructural analysis data for AISI 316L and AISI 347H stainless steels after exposure to a supercritical water environment

    Ruiz, A.; Timke, T.; van de Sande, A.; Heftrich, T.; Novotny, R.; Austin, T.

    2016-01-01

    This article presents corrosion data and microstructural analysis data of austenitic stainless steels AISI 316L and AISI 347H exposed to supercritical water (25 MPa, 550 °C) with 2000 ppb of dissolved oxygen. The corrosion tests lasted a total of 1200 h but were interrupted at 600 h to allow measurements to be made. The microstructural data have been collected in the grain interior and at grain boundaries of the bulk of the materials and at the superficial oxide layer developed during the corrosion exposure. PMID:27158647

  1. Corrosion and microstructural analysis data for AISI 316L and AISI 347H stainless steels after exposure to a supercritical water environment.

    Ruiz, A; Timke, T; van de Sande, A; Heftrich, T; Novotny, R; Austin, T

    2016-06-01

    This article presents corrosion data and microstructural analysis data of austenitic stainless steels AISI 316L and AISI 347H exposed to supercritical water (25 MPa, 550 °C) with 2000 ppb of dissolved oxygen. The corrosion tests lasted a total of 1200 h but were interrupted at 600 h to allow measurements to be made. The microstructural data have been collected in the grain interior and at grain boundaries of the bulk of the materials and at the superficial oxide layer developed during the corrosion exposure. PMID:27158647

  2. Taponamiento cardíaco por hipotiroidismo: descripción de 2 casos

    José Rafael Rojas-Solano

    2005-07-01

    Full Text Available Rara vez el derrame pericárdico en el hipotiroidismo evoluciona al taponamiento cardíaco, complicación que es mortal si no se diagnostica y trata a tiempo. En este artículo describimos dos singulares casos y discutimos aspectos importantes de la fisiopatología, diagnóstico y manejo de esta enfermedad.Pericardial effusion in hypothyroidism seldom evolves to cardiac tamponade, a fatal complication if diagnosis and treatment are delayed. In this article, we describe 2 singular cases and discuss important facts about the pathophysiology, diagnosis and management of this disease.

  3. Actualización en legislación de alimentos para celíacos

    Pellicer, K.; Huber, Bárbara; Benítez, F.; Bigeon, G.; Barbero, R.; Salum, L.; Copes, Julio

    2014-01-01

    Se realizó un análisis de la normativa sanitaria sobre alimentos para celíacos y su impacto en la población celíaca, mediante la investigación y comparación de las normativas sanitarias argentina e internacional sobre alimentos libres de gluten y el análisis de las consultas realizadas al listado oficial argentino de productos libres de gluten. La norma CODEX STAN 118/1979 y la normativa de la Comunidad Europea reconocen como alimentos “exentos de gluten” a los que contienen hasta 20 mg/kg y ...

  4. Blastocystis hominis en pacientes celíacos sintomáticos

    Oscar Manuel Villa Jiménez; Ángel Escobedo Carbonell; Olga Marina Hano García; Lisette Wood Rodríguez; Frank Pérez Triana; Licet González Fabián

    2012-01-01

    Introducción. La enfermedad celíaca (EC) no diagnosticada o no tratada compromete histológica, inmunológica y nutricionalmente a quienes la sufren. Estas alteraciones permitirían la infección por parásitos que no causarían síntomas en pacientes inmunocompetentes, como por ejemplo el Blastocystis hominis (Bh). Objetivo. Analizar la presencia de Bh en celíacos sintomáticos y describir el cuadro clínico, estado histológico, inmunológico y nutricional en dichos pacientes. Material y métodos. E...

  5. Domainwise Web Page Optimization Based On Clustered Query Sessions Using Hybrid Of Trust And ACO For Effective Information Retrieval

    Dr. Suruchi Chawla

    2015-08-01

    Full Text Available Abstract In this paper hybrid of Ant Colony OptimizationACO and trust has been used for domainwise web page optimization in clustered query sessions for effective Information retrieval. The trust of the web page identifies its degree of relevance in satisfying specific information need of the user. The trusted web pages when optimized using pheromone updates in ACO will identify the trusted colonies of web pages which will be relevant to users information need in a given domain. Hence in this paper the hybrid of Trust and ACO has been used on clustered query sessions for identifying more and more relevant number of documents in a given domain in order to better satisfy the information need of the user. Experiment was conducted on the data set of web query sessions to test the effectiveness of the proposed approach in selected three domains Academics Entertainment and Sports and the results confirm the improvement in the precision of search results.

  6. Study on tempering behaviour of AISI 410 stainless steel

    Martensitic stainless steels find extensive applications due to their optimum combination of strength, hardness and wear-resistance in tempered condition. However, this class of steels is susceptible to embrittlement during tempering if it is carried out in a specific temperature range resulting in significant reduction in toughness. Embrittlement of as-normalised AISI 410 martensitic stainless steel, subjected to tempering treatment in the temperature range of 673–923 K was studied using Charpy impact tests followed by metallurgical investigations using field emission scanning electron and transmission electron microscopes. Carbides precipitated during tempering were extracted by electrochemical dissolution of the matrix and identified by X-ray diffraction. Studies indicated that temper embrittlement is highest when the steel is tempered at 823 K. Mostly iron rich carbides are present in the steel subjected to tempering at low temperatures of around 723 K, whereas chromium rich carbides (M23C6) dominate precipitation at high temperature tempering. The range 773–823 K is the transition temperature range for the precipitates, with both Fe2C and M23C6 types of carbides coexisting in the material. The nucleation of Fe2C within the martensite lath, during low temperature tempering, has a definite role in the embrittlement of this steel. Embrittlement is not observed at high temperature tempering because of precipitation of M23C6 carbides, instead of Fe2C, preferentially along the lath and prior austenite boundaries. Segregation of S and P, which is widely reported as one of the causes for temper embrittlement, could not be detected in the material even through Auger electron spectroscopy studies. - Highlights: • Tempering behaviour of AISI 410 steel is studied within 673–923 K temperature range. • Temperature regime of maximum embrittlement is identified as 773–848 K. • Results show that type of carbide precipitation varies with temperature of tempering

  7. Studies on Pumice Lightweight Aggregate Concrete with Quarry Dust Using Mathematical Modeling Aid of ACO Techniques

    J. Rex

    2016-01-01

    Full Text Available The lightweight aggregate is an aggregate that weighs less than the usual rock aggregate and the quarry dust is a rock particle used in the concrete for the experimentation. The significant intention of the proposed technique is to frame a mathematical modeling with the aid of the optimization techniques. The mathematical modeling is done by minimizing the cost and time consumed in the case of extension of the real time experiment. The proposed mathematical modeling is utilized to predict four output parameters such as compressive strength (Mpa, split tensile strength (Mpa, flexural strength (Mpa, and deflection (in mm. Here, the modeling is carried out with three different optimization techniques like genetic algorithm (GA, particle swarm optimization (PSO, and ant colony optimization (ACO with 80% of data from experiment utilized for the training and the remaining 20% for the validation. Finally, while testing, the error value is minimized and the performance obtained in the ACO for the parameters such as compressive strength, split tensile strength, flexural strength, and deflection is 91%, 98%, 87%, and 94% of predicted values, respectively, in the mathematical modeling.

  8. Marcadores cardíacos na medicina veterinária Cardiac markers in veterinary medicine

    Letícia Andreza Yonezawa

    2010-02-01

    Full Text Available Os marcadores cardíacos são utilizados com o intuito de auxiliar no diagnóstico clínico de animais com doença cardíaca com maior acurácia e em menor tempo possível, possibilitando o estabelecimento do prognóstico e a terapia precocemente. Entretanto, em medicina veterinária, no Brasil, sua aplicabilidade ainda é, em geral, restrita a pesquisas. Esta revisão tem como objetivo abordar os principais marcadores cardíacos para que futuramente estes possam se tornar índices essenciais na avaliação cardíaca.Cardiac markers have been used in order to assist clinical diagnosis of animals with heart disease, more accurately, enabling the establishment of earlier prognosis and therapy. However, in Brazilian veterinary medicine, these markers are generally still restricted to researches. This review aims to approach the major cardiac markers, which further may become essential indexes in heart assessment.

  9. Application of GA, PSO, and ACO Algorithms to Path Planning of Autonomous Underwater Vehicles

    Mohammad Pourmahmood Aghababa; Mohammad Hossein Amrollahi; Mehdi Borjkhani

    2012-01-01

    In this paper,an underwater vehicle was modeled with six dimensional nonlinear equations of motion,controlled by DC motors in all degrees of freedom.Near-optimal trajectories in an energetic environment for underwater vehicles were computed using a numerical solution of a nonlinear optimal control problem (NOCP).An energy performance index as a cost function,which should be minimized,was defined.The resulting problem was a two-point boundary value problem (TPBVP).A genetic algorithm (GA),particle swarm optimization (PSO),and ant colony optimization (ACO) algorithms were applied to solve the resulting TPBVP.Applying an Euler-Lagrange equation to the NOCE a conjugate gradient penalty method was also adopted to solve the TPBVP.The problem of energetic environments,involving some energy sources,was discussed.Some near-optimal paths were found using a GA,PSO,and ACO algorithms.Finally,the problem of collision avoidance in an energetic environment was also taken into account.

  10. Optimization of Vibration Reduction Ability of Ladder Tracks by FEM Coupled with ACO

    Hao Jin

    2015-01-01

    Full Text Available Ladder track, which has drawn increased attention in scientific communities, is an effective method for reducing vibrations from underground railways. In order to optimize the vibration reduction ability of ladder track, a new method, that is, the finite element method (FEM coupled with ant colony optimization (ACO, has been proposed in this paper. We describe how to build the FEM model verified by the vibration tests in the Track Vibration Abatement and Control Laboratory and how to couple the FEM with ACO. The density and elasticity modulus of the sleeper pad are optimized using this method. After optimization, the vibration acceleration level of the supporting platform in the 1–200 Hz range was reduced from 102.8 dB to 94.4 dB. The optimized density of the sleeper pad is 620 kg/m3, and the optimized elasticity modulus of the sleeper pad is 6.25 × 106 N/m2.

  11. AISI waste oxide recycling program. Final technical report

    Aukrust, E.; Downing, K.B.; Sarma, B.

    1995-08-01

    In March 1995 AISI completed a five-year, $60 million collaborative development program on Direct Steelmaking cost-shared by DOE under the Metals Initiative. This program defined an energy-efficient and environmentally-friendly technology to produce hot metal for steelmaking directly from coal and iron ore pellets without incurring the high capital costs and environmental problems associated with traditional coke oven and blast furnace technology. As it becomes necessary to replace present capacity, this new technology will be favored because of reduced capital costs, higher energy efficiency, and lower operating costs. In April 1994, having failed to move forward with a demonstration plant for direct ironmaking, despite substantial efforts by both Stelco and Geneva Steel, an alternative opportunity was sought to commercialize this new technology without waiting until existing ironmaking capacity needed to be replaced. Recycling and resource recovery of steel plant waste oxides was considered an attractive possibility. This led to approval of a ten-month, $8.3 million joint program with DOE on recycling steel plant waste oxides utilizing this new smelting technology. This highly successful trial program was completed in December 1994. The results of the pilot plant work and a feasibility study for a recycling demonstration plant are presented in this final technical report.

  12. Qualification criteria verification for aisi-4340 steel suspension lug

    All external loads carried underneath an aircraft are mounted onto it through mechanism generally known as suspension system. The externally mounted attachments like bombs, missiles and fuel tanks etc. experience enormous aerodynamic and inertial forces in the flights. These forces are transferred to the interface point of suspension system, known as 'Suspension Lug'. Thus lugs are considered critical component and have extremely stringent qualification criteria standards used in the aviation industry in USA, Europe, Russia, etc. Different standards prevail in different parts of the world about qualification and testing of these lugs. As Pakistan is entering into aviation industry, therefore there is a need to fulfill the requirements of these standards, to suit Pakistani environment. The suspension lug under study is 2000 Ibs. load class made from AISI-4340 Steel having good mechanical properties as per required standard. The manufacturing processes included forging, machining and vacuum heat treatment. The prototypes of suspension lugs were manufactured in the local industry and subjected to the required mechanical tests such as tensile testing at 5 to 35 degree angles. Impact testing at cryogenic temperatures of -50 to -70 degree C, and breaking load testing were performed. The acceptable results were obtained and mechanical testing for qualification of lugs was finalized and standardized. The options were compared with practical viability, utilization of product and cost effectiveness. (author)

  13. High-temperature oxidation behavior of aluminized AISI 4130 steel

    Badaruddin, Mohammad; Wang, Chaur Jeng; Wardono, Herry; Tarkono, Asmi, Dwi

    2016-02-01

    AISI 4130 steel was dipped into a molten aluminum bath at 700°C for 16 s to produce an aluminide coating on the steel substrate. The coating, which consisted of an Al-rich layer and an FeAl3 and Fe2Al5 intermetallic layer, strongly adhered to the steel substrate. High-temperature oxidation of the bare steel and aluminized steel was performed by thermogravimetry at 850°C for 49 h in static air. The oxidation products were characterized by scanning electron microscopy and energy-dispersive spectroscopy. The aluminide coating could increase the oxidation resistance of the bare steel by a factor of ˜19. The increase in high-temperature oxidation resistance of the aluminized steel is attributed to the formation of protective alumina scale (α-Al2O3). Although iron oxide nodules grew on the aluminide coating surface, the oxidation rate of the aluminide coatings was very low. After 49 h of oxidation, agglomerates of α-Al2O3 fine grains grew on the rod-shaped FeAl phases.

  14. Deformation induced martensite in AISI 316 stainless steel

    The forming process leads to a considerable differentiation of the strain field within the billet, and finally causes the non-uniform distribution of the total strain, microstructure and properties of the material over the product cross-section. This paper focus on the influence of stress states on the deformation-induced a martensitic transformation in AISI Type 316 austenitic stainless steel. The formation of deformation-induced martensite is related to the austenite (g) instability at temperatures close or below room temperature. The structural transformation susceptibility is correlated to the stacking fault energy (SFE), which is a function not only of the chemical composition, but also of the testing temperature. Austenitic stainless steels possess high plasticity and can be easily cold formed. However, during cold processing the hardening phenomena always occurs. Nevertheless, the deformation-induced martensite transformation may enhance the rate of work-hardening and it may or may not be in favour of further material processing. Due to their high corrosion resistance and versatile mechanical properties the austenitic stainless steels are used in pressing of heat exchanger plates. However, this corrosion resistance is influenced by the amount of martensite formed during processing. In order to establish the links between total plastic strain, and martensitic transformation, the experimental tests were followed by numerical simulation. (Author) 21 refs.

  15. Plasma post oxidation of nitrocarburized AISI 4140 steel

    LEE Insup

    2006-01-01

    Plasma nitrocarburizing and plasma oxidizing treatments were performed to improve the wear and corrosion resistance of AISI 4140 steel.Plasma nitrocarburizing was conducted for 3 h at 570 ℃ in the nitrogen, hydrogen and methane atmosphere to produce the ε-Fe2-3(N,C) phase.It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of ε-phase, with a small proportion of γ'-Fe4(N,C) phase.The thickness of the compound layer was about 10 μm and the diffusion layer was about 300 μm in thickness, respectively.Plasma post oxidation was performed on the nitrocarburized samples with various oxygen/hydrogen ratio at a constant temperature of 500 ℃ for 1 h.The very thin magnetite (Fe3O4) layer 1-2 μm in thickness on top of the compound layer was obtained by plasma post oxidation.It was confirmed that the corrosion characteristics of the nitrocarburized compound layer can be further improved by the application of the superficial magnetite layer.

  16. Environment-tensile property relationship in AISI 1018 steel

    Environment-material interaction depends on several concurrent and mutually competitive variables ranging from nature of the environment to composition of the steel and including: the test temperature; the time of exposure of the material to the environment; the deformation rate; and intrinsic microstructural effects; The present work is a characterization of strain rate and environment influences on the tensile properties of a steel, AISI 1018, having a fully spheroidized microstructure. Tensile tests were performed at ambient temperature (300 K) in environments which are mildly aggressive (moist laboratory air-relative humidity 50%) and inert (dry gaseous nitrogen). The specimens were deformed to failure at strain rates of 10-4sec-1 and 10-5sec-1. No appreciable increase in yield and tensile strengths was observed at the strain rate of 10-4sec-1. However, the increase in both was of the order of 10 to 12% at the strain rate of 10-5sec-1. Ductility showed no variation with strain rate, but increased in the inert environment at both strain rates. Both environment and strain rate were found to have little to no influence on reduction in area of the test specimens. The true fracture stress followed a similar trend to the yield strength and ultimate tensile strength. (author)

  17. Characterization of AISI 1005 corrosion films grown under cyclic voltammetry of low sulfide ion concentrations

    Highlights: •The corrosion of AISI 1005 in sulfide solutions was investigated. •The mechanism of film growth on carbon steel in sulfide solutions was studied. •Film growth was characterized using SEM, EDX, XRD and Mössbauer spectroscopy. •Growth of AISI 1005 corrosion films under cyclic voltammetry. -- Abstract: The mechanism of AISI 1005 corrosion in sulfide ion solutions has been investigated using cyclic voltammetry, electrochemical impedance spectroscopy, X-ray diffraction (XRD) and Mössbauer spectroscopy (MS). The proposed mechanism occurs with the initial formation of oxygenated ferrous species followed by adsorption of HS− species, precipitation of iron monosulfides and their partial conversion to bisulfide iron. This mechanism was demonstrated by XRD results that revealed Fe-O and Fe-S phases and by MS results that detected pyrite as the major proportion (94%) of the iron species in the corrosion product

  18. NHETS - Estudo de Necrópsias de Pacientes Submetidos a Transplante Cardíaco

    Thiago Ninck Valette

    2014-06-01

    Full Text Available Fundamento: Discordâncias entre diagnóstico pre e post-mortem são relatadas na literatura, podendo variar de 4,1 a 49,8% dentre os casos encaminhados para exame necroscópico, com importante repercussão no tratamento dos pacientes. Objetivo: Analisar pacientes com óbito após o transplante cardíaco e confrontar os diagnósticos pre e post-mortem. Métodos: Por meio da revisão de prontuários, foram analisados dados clínicos, presença de comorbidades, esquema de imunossupressão, exames laboratoriais, causa clínica do óbito e causa do óbito à necrópsia. Foram confrontadas, então, a causa clínica e a causa necroscópica do óbito de cada paciente. Resultados: Foram analisados 48 óbitos submetidos à necrópsia no período de 2000 a 2010; 29 (60,4% tiveram diagnósticos clínico e necroscópico concordantes, 16 (33,3% tiveram diagnósticos discordantes e três (6,3% tiveram diagnóstico não esclarecido. Entre os discordantes, 15 (31,3% apresentaram possível impacto na sobrevida e um (2,1% não apresentou impacto na sobrevida. O principal diagnóstico clínico feito equivocadamente foi o de infecção, com cinco casos (26,7% dos discordantes, seguido por rejeição hiperaguda, com quatro casos (20% dos discordantes, e tromboembolismo pulmonar, com três casos (13,3% dos discordantes. Conclusão: Discordâncias entre o diagnóstico clínico e achados da necrópsia são comumente encontradas no transplante cardíaco. Novas estratégias no aperfeiçoamento do diagnóstico clínico devem ser introduzidas, considerando-se os resultados da necrópsia para melhoria do tratamento da insuficiência cardíaca por meio do transplante cardíaco.

  19. Low temperature plasma carburizing of AISI 316L austenitic stainless steel and AISI F51 duplex stainless steel Cementação sob plasma à baixa temperatura do aço inoxidável austenítico AISI 316L e do aço inoxidável duplex AISI F51

    Carlos Eduardo Pinedo

    2013-06-01

    Full Text Available In this work an austenitic AISI 316L and a duplex AISI F51 (EN 1.4462 stainless steel were DC-Plasma carburized at 480ºC, using CH4 as carbon carrier gas. For the austenitic AISI 316L stainless steel, low temperature plasma carburizing induced a strong carbon supersaturation in the austenitic lattice and the formation of carbon expanded austenite (γC without any precipitation of carbides. The hardness of the carburized AISI 316L steel reached a maximum of 1000 HV due to ∼13 at% carbon supersaturation and expansion of the FCC lattice. For the duplex stainless steel AISI F51, the austenitic grains transformed to carbon expanded austenite (γC, the ferritic grains transformed to carbon expanded ferrite (αC and M23C6 type carbides precipitated in the nitrided case. Hardness of the carburized case of the F51 duplex steel reached 1600 HV due to the combined effects of austenite and ferrite lattice expansion with a fine and dispersed precipitation of M23C6 carbides.O aço inoxidável austenítico AISI 316L e o aço inoxidável duplex AISI F51 (EN 1.4462 foram cementados sob plasma-DC na temperatura de 480ºC, utilizando-se CH4 como gás de arraste. A cementação sob plasma à baixa temperatura conduziu a uma elevada supersaturação do reticulado cristalino em carbono com a formação de austenita expandida(γC, sem a precipitação de carbonetos. A dureza do aço 316L, após a cementação, atingiu um valor máximo de 1000 HV, devido à supersaturação de ∼ 13 at% de carbono e à expansão do reticulado cristalino CFC. Para o aço inoxidável duplex AISI F51, os grãos de austenita se transformaram em austenita expandida pelo carbono e os grãos de ferrita se transformaram para ferrita expandida com a precipitação de carbonetos do tipo M23C6, na camada cementada. A dureza da camada cementada, no aço F51, atingiu 1600HV, devido ao efeito combinado da expansão dos reticulados cristalinos da austenita e da ferrita com a precipitação fina e

  20. Laser gas assisted treatment of AISI H12 tool steel and corrosion properties

    Yilbas, B. S.; Toor, Ihsan-ul-Haq; Malik, Jahanzaib; Patel, F.

    2014-03-01

    Laser gas assisted treatment of AISI H12 tool steel surface is carried out and the electrochemical response of the laser treated surface is investigated. Morphological and metallurgical changes in the treated layer are examined using a scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. Potentiodynamic polarization tests are carried out for untreated and laser treated specimen in 0.2 M NaCl solution at room temperature. It is found that the laser treated AISI H12 workpiece surfaces exhibit higher corrosion resistance as compared to untreated specimen as confirmed by lower corrosion rate, higher pitting potential, and lower passive current density.

  1. Corrosion Behavior of TiN Coated AISI D2 Steel

    ÇEĞİL, Özkan; Şen, Şaduman

    2014-01-01

    In this study, the corrosion behaviors of nitride and titanium nitride (TiN) layers deposited on AISI D2 steel samples are reported. Steel was at first nitrided in a nitrogen and ammonia atmosphere at 575 °C for 8 h and then titanium nitride coating treatment was performed in the powder mixture consisting of ferro-titanium, ammonium chloride and alumina at 1000°C for 2h by pack diffusion coating. TiN coating layer thickness realized on the AISI D2 steel is 6,71 ± 0,9 μm. The hardness of TiN l...

  2. Study of radiation damages in AISI 316 and 347 steels

    The CV-28 cyclotron at IEN (Nuclear Engineering Institute) has been used to simulated, in a short time scale, uniform He concentrations produced during neutron irradiation of metals by (n, α) reactions. Helium was implanted at concentrations of 1 to 300 ppm in 100 μm thick sheet samples of AISI 316 and 347 S S by degrading a 28 MeV alpha particle beam with a rotating energy degrader. The effects of He on the mechanical properties of the steels were studied by both non-destructive (positron annihilation) and destructive tests (tensile, creep, TEM and SEM). The positron lifetime measurements of irradiated and annealed samples were used as the base to discuss the He diffusion mechanism. Activation energies of 0.34±0.04 eV for 316 S S and 0.57±0.06 eV for 347 S S, characterized a dissociative process above 6500 C. TEM analyses have suggested the Ostwald ripening process for bubble growth over the full range of He concentrations studied. It was shown, in agreement with theoretical calculations that, by themselves the displacements produced during the helium implantation, at rate of 1.8 x 10-3 d pa/ppm, were not sufficient to cause significant changes in ductility. However, a strong ductility loss with increasing He concentration was observed for both types of steel for tensile tests at 250 C, as well as in creep at 7500 C over the range of strain (100 to 200 MPa). Finally, it was shown that charged particle simulation associated with positron annihilation techniques provides a fast, relatively low cost, and useful method to study different kinds of neutron damage in materials. (author)

  3. Biomaterial Studies on AISI 316L Stainless Steel after Magnetoelectropolishing

    Massimiliano Filippi

    2009-03-01

    Full Text Available The polarisation characteristics of the electropolishing process in a magnetic field (MEP – magnetoelectropolishing, in comparison with those obtained under standard/conventional process (EP conditions, have been obtained. The occurrence of an EP plateau has been observed in view of the optimization of MEP process. Up-to-date stainless steel surface studies always indicated some amount of free-metal atoms apart from the detected oxides and hydroxides. Such a morphology of the surface film usually affects the thermodynamic stability and corrosion resistance of surface oxide layer and is one of the most important features of stainless steels. With this new MEP process we can improve metal surface properties by making the stainless steel more resistant to halides encountered in a variety of environments. Furthermore, in this paper the stainless steel surface film study results have been presented. The results of the corrosion research carried out by the authors on the behaviour of the most commonly used material - medical grade AISI 316L stainless steel both in Ringer’s body fluid and in aqueous 3% NaCl solution have been investigated and presented earlier elsewhere, though some of these results, concerning the EIS Nyquist plots and polarization curves are also revealed herein. In this paper an attempt to explain this peculiar performance of 316L stainless steel has been undertaken. The SEM studies, Auger electron spectroscopy (AES and X-ray photoelectron spectroscopy (XPS were performed on 316L samples after three treatments: MP – abrasive polishing (800 grit size, EP – conventional electrolytic polishing, and MEP – magnetoelectropolishing. It has been found that the proposed magnetoelectropolishing (MEP process considerably modifies the morphology and the composition of the surface film, thus leading to improved corrosion resistance of the studied 316L SS.

  4. Transplante cardíaco humano: experiência inicial Human cardiac transplant: initial experience

    Noedir A. G Stolf; Edimar Bocchi; Pedro C. P Lemos; Fábio Biscegli Jatene; Pablo M. A. Pomerantzeff; Lourdes Higushi; Jorge Kalil; Alfredo I. FIORELLI; José Otávio C Auler Júnior; Giovanni Bellotti; Lélio A Silva; Fúlvio Pileggi; Adib D Jatene

    1986-01-01

    No Instituto do Coração, de março de 1985 a fevereiro de 1986,11 pacientes foram submetidos a transplante cardíaco ortotópico. Eram todos do sexo masculino, com idade variando de 39 a 54 anos; 6 com cardiopatia isquémica, 4 com cardiomiopatia dilatada e um com cardiomiopatia chagásica. Foi realizado estudo hemodinâmico através de catéter de Swan-Ganz, no pré-operatório, no pós-operatório, após estabilização na unidade de recuperação, e trinta ou mais dias após o transplante. Os dados mostram ...

  5. As Camélias Oitocentistas do Buçaco

    Cordeiro, Liliana Margarida Correia

    2014-01-01

    Durante séculos, o género Camellia desempenhou um papel importante como ornamental. Em Portugal, o fascínio por estas plantas teve o seu clímax no século XIX, principalmente no noroeste e na cidade de Sintra, onde as condições são particularmente favoráveis para o seu cultivo. A Mata do Buçaco, uma floresta no centro do país, é das áreas menos conhecidas de camélias. As suas camélias datam deste período, quando estas plantas eram itens de colecção para os nobres. Alfredo Allen, Visconde da Qu...

  6. A new VUV high resolution undulator-based beamline at Super-ACO

    The VUV undulator-based high resolution SU5 beamline, designed to operate in the 5-45 eV photon energy range, is under construction at Super-ACO. It is composed of three toroidal mirrors around a 6.65 m Eagle off-plane normal incidence monochromator, whose induced-astigmatism is negligible owing to an horizontal focusing onto the gratings. With an optical design minimizing the aberrations and optimizing the throughput through the entrance slit, and with a careful choice of the optical coatings, the SU5 beamline should provide in the near future more than 1010 ph/s at the sample level for a 1/50000 bandwidth in the 5-25 eV energy range. The ultimate resolving power should be higher than 105. (orig.)

  7. Experimental evaluation of a R134a/CO2 cascade refrigeration plant

    We present the experimental evaluation of a R134a/CO2 cascade refrigeration plant designed for low evaporation temperature in commercial refrigeration applications. The test bench incorporates two single-stage vapour compression cycles driven by semi hermetic compressors coupled thermally through two brazed plate cascade heat exchangers working in parallel and controlled by electronic expansion valves. The experimental evaluation (45 steady-states) covers evaporating temperatures from −40 to −30 °C and condensing from 30 to 50 °C. In each steady-state, we conducted a sweep of the condensing temperature of the low temperature cycle with speed variation of the high temperature compressor. Here, the energy performance of the plant is analysed, focussing on the compressors' performance, temperature difference in the cascade heat exchanger, cooling capacity, COP and compressors discharge temperatures. - Highlights: • The experimental evaluation of a R134a/CO2 cascade refrigeration plant is presented. • Temperature difference in cascade heat exchanger varied from 3.3 to 5.3 °C. • Variation of intermediate level produced maximum COP variations of 6%. • Cooling capacity ranged from 4.5 kW (−40 and 40 °C) to 7.5 kW (−30 and 30 °C). • COP ranged from 1.05 (−40 and 40 °C) to 1.65 (−30 and 30 °C)

  8. THE EFFECT OF SMALL AMOUNTS OF ELEMENTS ON SHAPES OF POTENTIODYNAMIC AND POTENTIOSTATIC CURVES OF AISI 304L AND AISI 316L STAINLESS STEELS IN CHLORIDE MEDIA

    D. Pulino-Sagradi

    1997-06-01

    Full Text Available Abstract - Samples of high purity grade and commercial purity grade type AISI 304L and AISI 316L steels were studied by the potentiodynamic and potentiostatic techniques in a naturally aerated 3.5% NaCl aqueous solution at a controlled temperature of (23±2°C. The anodic polarization curves of the potentiodynamic technique showed that not always is it possible to determine pitting potential: most of the curves of commercial purity grade steels displayed a smooth curvature in the region where the current density should increase sharply. The density current versus time potentiostatic curves also showed different shapes according to the purity grade steels: for the commercial purity grade steels, the current density showed large oscillations with time (related to unstable pits, whereas for the high purity grade steels, a regular behavior of current density as a function of time was found (related to stable pits

  9. Study of carbonitriding thermochemical treatment by plasma screen in active with pressures main austenitic stainless steels AISI 409 and AISI 316L

    The technique called Active Screen Plasma Nitriding (ASPN) is being used as an alternative once it offers several advantages with respect to conventional DC plasma. In this method, the plasma does not form directly in the sample's surface but on a screen, in such a way that undesired effects such as the edge effect is minimized. Stainless steels present not very satisfactory wearing characteristics. However, plasma carbonitriding has been used as to improve its resistance to wearing due to the formation of a fine surface layer with good properties. In this work, samples of stainless steel AISI 316L and AISI 409 were treated at pressures of 2.5 and 5 mbar. After the treatments they were characterized by microhardness, microscopy and Xray diffraction. Microscopy and hardness analysis showed satisfactory layers and toughness in those steels. (author)

  10. Evaluation of structural behaviour and corrosion resistant of austenitic AISI 304 and duplex AISI 2304 stainless steel reinforcements embedded in ordinary Portland cement mortars

    The mechanical and structural behaviour of two stainless steels reinforcements, with grades austenitic EN 1.4301 (AISI 304) and duplex EN 1.4362 (AISI 2304) have been studied, and compared with the conventional carbon steel B500SD rebar. The study was conducted at three levels: at rebar level, at section level and at structural element level. The different mechanical properties of stainless steel directly influence the behaviour at section level and structural element level. The study of the corrosion behaviour of the two stainless steels has been performed by electrochemical measurements, monitoring the corrosion potential and the lineal polarization resistance (LPR), of reinforcements embedded in ordinary Portland cement (OPC) mortar specimens contaminated with different amount of chloride over one year time exposure. Both stainless steels specimens embedded in OPC mortar remain in the passive state for all the chloride concentration range studied after one year exposure. (Author) 26 refs.

  11. Structure and properties of the Stainless steel AISI 316 nitrided with microwave plasma; Estructura y propiedades del acero inoxidable AISI 316 nitrurado con plasmas de microondas

    Becerril R, F

    1999-07-01

    In this work were presented the results obtained by nitridation on stainless steel AISI 316 using a plasma generated through a microwave discharge with an external magnetic field using several moistures hydrogen / nitrogen to form a plasma. The purpose of nitridation was to increase the surface hardness of stainless steel through a phase formation knew as {gamma}N which has been reported that produces such effect without affect the corrosion resistance proper of this material. (Author)

  12. Wear resistance of Fe-Nb-Cr-W, Nb, AISI 1020 and AISI 420 coatings produced by thermal spray wire arc

    The commercial materials 140MXC (with iron, tungsten, chrome, niobium), 530AS (AISI 1015 steel) and 560AS (AISI 420 steel) on AISI 4340 steel were deposited using thermal spray with arc. The aim of work was to evaluate the best strategy abrasive wear resistance of the system coating-substrate using the following combinations: (1) homogeneous coatings and (2) coatings depositing simultaneously 140MXC + 530AS and 140MXC + 560AS. The coatings microstructure was characterized using Optical microscopy, Scanning electron microscopy and Laser con focal microscopy. The wear resistance was evaluated through dry sand rubber wheel test (DSRW). We found that the wear resistance depends on the quantity of defects and the mechanical properties like hardness. For example, the softer coatings have the biggest wear rates and the failure mode was characterized by plastic deformation caused by particles indentation, and the other hand the failure mode at the harder materials was grooving. The details and wear mechanism of the coatings produced are described in this investigation. (Author)

  13. Microstructural characterization of an AISI-SAE 4140 steel without nitridation and nitrided

    It was micro structurally characterized an AISI-SAE 4140 steel before and after of nitridation through the nitridation process by plasma post-unloading microwaves through Optical microscopy (OM), Scanning electron microscopy (SEM) by means of secondary electrons and retrodispersed, X-ray diffraction (XRD), Energy dispersion spectra (EDS) and mapping of elements. (Author)

  14. Influence of plasma nitriding on the hardness of AISI 304 and low carbon steel

    Nitriding with plasma/ion nitriding technique for surface treatment of AISI 304 and low carbon steel as a machine component material has been done. Surface treatment is meant to improve the surface quality of metal especially its hardness. To reach the optimum condition it has been done a variation of nitriding pressure, while to analyse the result it has been done the hardness and microstructure test, and the nitrogen content. Result of the test indicates that: the optimum hardness obtained at 1.8 mbar of pressure that is 624.9 VHN or 2.98 times while the initial hardness is 210.3 VHN for AISI 304 and 581.6 VHN or 3.07 times compare with initial hardness 142.9 VHN for low carbon steel. The thickness of nitride layer for AISI 304 and low carbon steel is around 30 µm. Nitrogen contents after nitriding are 10.74% mass or 30.32% atom for AISI 304 and 6.81% mass or 21.76% atom for low carbon steel. (author)

  15. The adhesion of hot-filament CVD diamond films on AISI type 316 austenitic stainless steel

    Buijnsters, J.G.; Shankar, P.; Enckevort, W.J.P. van; Schermer, J.J.; Meulen, J.J. ter

    2004-01-01

    Steel ball indentation and scratch adhesion testing of hot filament chemical vapour deposited diamond films onto AISI type 316 austenitic stainless steel substrates using two different interlayer systems, namely chromium nitride and borided steel, have been investigated. In order to compare the adhe

  16. Influence of the surface finishing on electrochemical corrosion characteristics of AISI 316L stainless steel

    Dundeková, S.; Hadzima, B.; Fintová, Stanislava

    2015-01-01

    Roč. 22, č. 2 (2015), s. 77-84. ISSN 1335-0803 Institutional support: RVO:68081723 Keywords : AISI 316L stainless steel * EIS * Corrosion Subject RIV: JK - Corrosion ; Surface Treatment of Materials http://ojs.mateng.sk/index.php/Mateng/article/view/167/278

  17. Produção de amoníaco e sua optimização

    Roque, Marta de Jesus

    2008-01-01

    Com este trabalho pretendeu-se estudar o estado da arte de produção de amoníaco que é uma matéria-prima importante para a produção de fertilizantes nitrogenados e é usado frequentemente em sistemas de refrigeração industrial. A sua obtenção via reacção catalítica em meio gasoso baseado no processo Haber-Bosch é o método mais utilizado. Com base nos dados recolhidos e diagramas de processos relativos à produção de amoníaco foi desenvolvido uma folha de simulação que per...

  18. Taponamiento cardíaco secundario a carcinoma papilar esclerosante difuso de tiroides

    Verónica Riva

    2011-12-01

    Full Text Available El carcinoma papilar, variante esclerosante difusa, corresponde al 2% de todos los carcinomas papilares de la tiroides. Se caracteriza por comprometer de manera difusa y bilateral a la glándula tiroides. Clínicamente se manifiesta con metástasis ganglionares y pulmonares, afectando predominantemente a mujeres jóvenes. Se describe un caso de taponamiento cardíaco como presentación inicial de un carcinoma papilar de tiroides variante esclerosante difusa. Una mujer de 32 años concurrió al servicio de emergencias médicas refiriendo epigastralgia y tos seca. Durante el examen físico se constató hipotensión arterial, taquicardia y ruidos cardíacos disminuidos. Se realizó un ecocardiograma, observándose derrame pericárdico. Por medio de una pericardiocentesis se obtuvo líquido pericárdico, cuyo análisis mostró células neoplásicas. Durante la evolución la paciente presentó recurrencia del derrame pericárdico por lo que se realizó una ventana pleuropericárdica, detectándose durante la cirugía una lesión nodular subpleural, la cual fue biopsiada e informada posteriormente como una metástasis de carcinoma papilar vinculable a origen tiroideo. Se realizó una tiroidectomía total con linfadenectomía cervical bilateral. El diagnóstico final fue carcinoma papilar, variante esclerosante difusa. Esta variante infiltra el tejido conectivo de los espacios interfoliculares, simulando una tiroiditis y se caracteriza por una permeación vascular temprana. En oposición a la variante clásica, la esclerosante difusa presenta mayor agresividad y mayor tasa de recurrencia. El carcinoma papilar de tiroides debe tenerse presente como diagnóstico diferencial en nuestro medio, en todas aquellas lesiones neoplásicas papilares metastásicas, más aún si se trata de mujeres jóvenes.

  19. No ROI in ACO. Risk, expense of Medicare program has most for-profit groups shying away.

    Kutscher, Beth

    2012-04-23

    For-profit healthcare companies aren't beating down the door to get in on Medicare ACOs. Several of the big chains say there is too much uncertainty about the experiment, and they're waiting to see how the program evolves. One company on the sideline is Capella Healthcare. Chairman and CEO Daniel Slipkovich, left, says there is a potential for high patient dropout rates and risks in population management. PMID:22571000

  20. Effect of heat treatment on an AISI 304 austenitic stainless steel evaluated by the ultrasonic attenuation coefficient

    The properties of metals can be substantially changed by various methods, one of them is using heat treatment processes. Moreover, ultrasonic testing is the most preferred and effective, nondestructive testing technique for characterization of mechanical material properties. Austenitic stainless steel AISI 304 serves in many applications due to high strength and corrosion resistance. In certain applications, it is important to evaluate the mechanical properties of AISI 304 stainless steel. In this study, the ultrasonic method (attenuation measurement technique) is used to evaluate the hardness of AISI 304 stainless steel samples which were heat treated at different levels. Due to the heat treatment process, each sample has its specific microstructure and hardness which attenuate ultrasonic waves appropriately. The ultrasonic and hardness test show that it is possible to evaluate the hardness of AISI 304 stainless steel by ultrasonic attenuation coefficient. In addition, the relationship between ultrasonic attenuation coefficients and time of heat treatment is investigated.

  1. Effect of heat treatment on an AISI 304 austenitic stainless steel evaluated by the ultrasonic attenuation coefficient

    Moghanizadeh, Abbas; Farzi, Abolfazl [Islamic Azad Univ., Esfarayen (Iran, Islamic Republic of). Dept. of Civil Engineering

    2016-07-01

    The properties of metals can be substantially changed by various methods, one of them is using heat treatment processes. Moreover, ultrasonic testing is the most preferred and effective, nondestructive testing technique for characterization of mechanical material properties. Austenitic stainless steel AISI 304 serves in many applications due to high strength and corrosion resistance. In certain applications, it is important to evaluate the mechanical properties of AISI 304 stainless steel. In this study, the ultrasonic method (attenuation measurement technique) is used to evaluate the hardness of AISI 304 stainless steel samples which were heat treated at different levels. Due to the heat treatment process, each sample has its specific microstructure and hardness which attenuate ultrasonic waves appropriately. The ultrasonic and hardness test show that it is possible to evaluate the hardness of AISI 304 stainless steel by ultrasonic attenuation coefficient. In addition, the relationship between ultrasonic attenuation coefficients and time of heat treatment is investigated.

  2. Microstructural changes of AISI 316L due to structural sensitization and its influence on the fatigue properties

    Dundeková, S.; Nový, F.; Fintová, Stanislava

    2014-01-01

    Roč. 21, č. 4 (2014), s. 172-177. ISSN 1335-0803 Institutional support: RVO:68081723 Keywords : AISI 316L * Structural sensitization * Rotating bending fatigue test Subject RIV: JL - Materials Fatigue, Friction Mechanics

  3. Eight reasons payer interoperability and data sharing are essential in ACOs. Interoperability standards could be a prerequisite to measuring care.

    Mookencherry, Shefali

    2012-01-01

    It makes strategic and business sense for payers and providers to collaborate on how to take substantial cost out of the healthcare delivery system. Acting independently, neither medical groups, hospitals nor health plans have the optimal mix of resources and incentives to significantly reduce costs. Payers have core assets such as marketing, claims data, claims processing, reimbursement systems and capital. It would be cost prohibitive for all but the largest providers to develop these capabilities in order to compete directly with insurers. Likewise, medical groups and hospitals are positioned to foster financial interdependence among providers and coordinate the continuum of patient illnesses and care settings. Payers and providers should commit to reasonable clinical and cost goals, and share resources to minimize expenses and financial risks. It is in the interest of payers to work closely with providers on risk-management strategies because insurers need synergy with ACOs to remain cost competitive. It is in the interest of ACOs to work collaboratively with payers early on to develop reasonable and effective performance benchmarks. Hence, it is essential to have payer interoperability and data sharing integrated in an ACO model. PMID:22352172

  4. EFFECTS OF CARBURIZING AND NITRIDING PROCESSES ON THE COST AND QUALITY OF GEARS PRODUCED WITH AISI 4140 AND 8620 STEELS

    Claudio José Leitão; Paulo Roberto Mei; Rodolfo Libard

    2012-01-01

    This study compares the effects of nitriding and carburizing processes applied to gears subjected to contact stresses below 1300 MPa. The manufacturing cost, as well the depth of hardened layer and the distortion produced by two processes are analyzed. AISI 4140 gears quenched, tempered, liquid and gas nitriding and AISI 8620 gears after liquid carburizing, quenching and tempering are analyzed. The dimensional control of the gears was carried out before and after heat and thermoch...

  5. Corrosion behavior of stainless steel in bio diesel production; Comportamento quanto a corrosao de acos inoxidaveis na producao do biodiesel

    Miranda, E.F. de [ArcelorMittal Sao Paulo Servicos, SP (Brazil); Moreira, M.C.; Lebrao, S.M.G. [Centro Universitario do Instituto Maua de Tecnologia, Sao Paulo, SP (Brazil)], e-mail: susana.lebrao@maua.br

    2010-07-01

    Biodiesel has become more attractive due to the benefits to the environment, mainly because it is a renewable resource. However, the main barrier to biodiesel is it cost. One factor which is charged to marketing is the use of stainless steel throughout the production line, the most used is AISI 304. To evaluate more economical stainless steels, weight loss and stress corrosion tests were performed on samples of AISI 304 and 439 in methanol PS X30% sodium methylate solution, crude soybean oil, glycerol and biodiesel for about two hundred and fifty days. The mass loss was negligible, and there was complete absence of pitting and stress corrosion cracking in all media studied, showing that both alloys are suitable for the manufacture of such equipment. (author)

  6. 向日葵ACC氧化酶基因(HaACO1)的克隆及表达分析%Cloning and Expression Analysis of ACC Oxidase Gene (HaACO1) from Sunflower (Helianthus annuus L.)

    孙瑞芬; 张艳芳; 郭树春; 于海峰; 李素萍; 乔慧蕾; 聂惠; 安玉麟

    2015-01-01

    目的:克隆向日葵中的ACC氧化酶基因(HaACO1),并对其进行生物信息学分析及盐胁迫表达分析,为理解向日葵ACC氧化酶生理功能并加强对ACO基因的利用奠定基础.方法:以前期从盐胁迫的内葵杂4号根中获得的ACC氧化酶基因片段4-4-7TDF(KM823963)为基础,通过RT-PCR和5'/3' RACE技术克隆ACO基因的全长cDNA序列,利用生物信息学软件对获得的eDNA序列及编码的蛋白质序列进行分析.同时采用PCR方法克隆基因组DNA(genemic DNA,gDNA)序列,并对其进行结构分析.利用实时荧光定量PCR分析NaCl胁迫下向日葵根、下胚轴、叶中HaACO1的表达量和不同NaCl浓度及不同胁迫时间下根中HaACO1的表达量.结果:HaACO1的cDNA序列全长为1 135bp,其开放阅读框为942bp,编码313个氨基酸.预测其分子质量和等电点分别为35.84kDa和5.13,基因登录号为KP966508.HaACO1与已报道的多种植物的ACO基因核苷酸序列及其推导的氨基酸序列有较高的相似性,分别为76% ~ 83%和77% ~88%.gDNA起始密码子至终止密码子序列长1 018bp,包含2个外显子和1个内含子,基因登录号为KP988289.实时荧光定量PCR分析表明向日葵HaACO1在不同器官及不同NaCl浓度、不同时间诱导下存在特异性表达差异.结论:获得的向日葵HaACO1是植物ACO家族成员之一,该基因应答盐胁迫具有独特的表达模式.

  7. AISI 316L under electron radiolysis at high temperature and pressure in PWR modelling conditions

    temperature (HT), 280-320 deg. C, and high pressure (HP), 15.5 MPa. Very few data are available in the literature on the role of HTHP water radiolysis on the corrosion of metallic reactor components. The present approach use electron beam to control the production of radiolytic species at a AISI 316L/PWR solution interface in a high temperature and high pressure (HTHP) electrochemical cell working at the range [25 deg. C, 1 bar] - [300 deg. C, 90 bar]. The cell is designed to record the free corrosion potential of the AISI 316L/PWR solution interface mounted on line at the SIRIUS pelletron delivering the electron beam (LSI, Ecole Polytechnique, France). The PWR primary solutions are simulated by aqueous solutions prepared at room temperature by adding boric acid and lithium hydroxide to high purity water and, in some cases, purged with Ar/H2 flow. At the AISI 316L/PWR solution interfaces irradiated between 25 deg. C/ 1 bar and 300 deg. C/ 90 bar, electrons emerge at ∼0.6 MeV and the flux varies from ∼1010 to 1012 e-.cm-2.s-1. The results clearly show that the response of the free potential between the AISI316L/water interface and a pseudo-reference electrode, i.e. a platinum wire during the irradiation (from electron beam switch-on until cut-off) depends on many parameters: the energy of the electron beam, the temperature and pressure, the concentration of hydrogen in the solution, the ageing of the disc electrode, the growth conditions of the initial oxide passive layers, etc... These results can be compared with those which have obtained by using the proton beam (CEMHTI, CNRS Orleans, France). Surface characterization experiments (XPS, SEM, Raman spectroscopy, photoluminescence...) on the oxide layer of AISI316L which are formed under the irradiation could also bring new information about the irradiation influence on the AISI316L. (authors)

  8. Task Scheduling problem in distributed systems considering communication cost and precedence by population-based ACO

    Hossein Erfani

    2012-09-01

    Full Text Available With regard to the fact of the rapid growth of distributed systems and their large spectrum of usage of proposing and representing controlling solutions and optimization of task execution procedures is one of the most important issues. Task scheduling in distributed systems has determining role in improving efficiency in applications such as communication, routing, production plans and project management. The most important issues of good schedule are minimizing makespan and average of waiting time. However, the recent and previous effort usually focused on minimizing makespan. This article presents and analyze a new method based on Ant Colony Optimization (ACO algorithm with considerations to precedence and communication cost for task scheduling problem. In the mentioned method in addition to optimization of finish time, average of waiting time and number of needed processors are also optimized. In this method, by using of a new heuristic list, an algorithm based on ant colony is proposed. The results obtained in comparison with the latest similar models of random search algorithms, proves the higher efficiency of algorithm.

  9. The cluster lens ACO 1703: redshift contrast and the inner profile

    Saha, Prasenjit

    2008-01-01

    ACO 1703 is a cluster recently found to have a variety of strongly lensed objects: there is a quintuply-imaged system at z=0.888 and several other lensed objects from z=2.2 to 3.0 (the cluster itself is at z=0.28). It is not difficult to model the lens, as previous work has already done. However, lens models are generically non-unique. We generate ensembles of models to explore the non-uniqueness. When the full range of source redshifts is included, all models are close to \\rho \\propto r^{-1} out to 200 kpc. But if the quint is omitted, both shallower and steeper models (e.g., \\rho \\propto r^{-2}) are possible. The reason is that the redshift contrast between the quint and the other sources gives a good measurement of the enclosed mass at two different radii, thus providing a good estimate of the mass profile in between. This result supports universal profiles and explains why single-model approaches can give conflicting results. The mass map itself is elongated in the NW-SE direction, like the galaxy distrib...

  10. NASA GES DISC support of CO2 Data from OCO-2, ACOS, and AIRS

    Wei, Jennifer C; Vollmer, Bruce E.; Savtchenko, Andrey K.; Hearty, Thomas J; Albayrak, Rustem Arif; Deshong, Barbara E.

    2013-01-01

    NASA Goddard Earth Sciences Data and Information Services Centers (GES DISC) is the data center assigned to archive and distribute current AIRS, ACOS data and data from the upcoming OCO-2 mission. The GES DISC archives and supports data containing information on CO2 as well as other atmospheric composition, atmospheric dynamics, modeling and precipitation. Along with the data stewardship, an important mission of GES DISC is to facilitate access to and enhance the usability of data as well as to broaden the user base. GES DISC strives to promote the awareness of science content and novelty of the data by working with Science Team members and releasing news articles as appropriate. Analysis of events that are of interest to the general public, and that help in understanding the goals of NASA Earth Observing missions, have been among most popular practices.Users have unrestricted access to a user-friendly search interface, Mirador, that allows temporal, spatial, keyword and event searches, as well as an ontology-driven drill down. Variable subsetting, format conversion, quality screening, and quick browse, are among the services available in Mirador. The majority of the GES DISC data are also accessible through OPeNDAP (Open-source Project for a Network Data Access Protocol) and WMS (Web Map Service). These services add more options for specialized subsetting, format conversion, image viewing and contributing to data interoperability.

  11. REGISTRO DE PARO CARDÍACO EN EL ADULTO Registries of outer hospital cardiac arrest in Bogotta-Colombia

    Ricardo Navarro Vargas

    2005-07-01

    Full Text Available En nuestro país no hay un registro estandarizado de los eventos cardíacos que requieren reanimación cerebro-cardio-pulmonar (RCCP siguiendo los lineamientos "Utstein". El propósito de este estudio fue determinar la calidad de los registros extrahospitalarios de paro cardíaco en el adulto, en Bogotá-Colombia. Entre enero y marzo de 2005 se realizó un análisis retrospectivo de los casos que correspondieron a paro cardíaco en el adulto atendidos por el "Centro Regulador de Urgencias del Distrito (CRU". El estudio reveló un registro deficiente de los eventos que requirieron RCCP realizados a nivel prehospitalario, e identificó al trauma como causa de paro cardíaco en 22% de los casos, una cifra particularmente elevada si se compara con los reportes mundiales, que oscilan entre 5% y 8%. Recomienda la estandarización del registro de paro cardíaco en el adulto, para lo cual se sugiere utilizar el formato de registro que sigue los lineamientos "Utstein".There is not a standardized registry form of cardiac events requiring cardiopulmonary resuscitation (CPR in our country such as the Utstein style. The purpose of this study was to determine the quality of the registries of out-ofhospital cardiac arrests in Bogotá-Colombia. A retrospective survey of registries of cardiac events assisted by a regulatory center "Centro Regulador de Urgencias del Distrito (CRU" was conducted, between January and March, 2005. The study reveals a poor registry of outof-hospital cardiac arrest in Bogotá-Colombia, and identifies trauma as the cause of cardiac arrest in 22% of cases, a particularly high figure compared with 5-8% registered worldwide. Recommend the standardization of the registry form of out-of-hospital cardiac arrest and suggest to use the "uniform reporting of data following cardiac arrest - the Utstein style". The registry forms are shown in appendix 1-2. Suggestions are welcome.

  12. Hot rolling of the superaustenitic stainless steel AISI 904L: Vroče valjanje superavstenitnega nerjavnega jekla AISI 904L:

    Arh, Boštjan; Burja, Jaka; PODGORNIK, Bojan; Tehovnik, Franc; Žužek, Borut

    2014-01-01

    The AISI 904L superaustenitic stainless steel has a narrow processing window. In this work the hot rolling of steel, specifically the hot deformation behavior, is investigated. Specimens of steel were hot rolled at temperatures from 1000 °C to 1250 °C with 50 °C increments and the rolling loads were measured and recorded. Microstructural changes were examined, with the accent on the recrystallization. From changes of the hot-rolling loads and microstructure it is concluded that the recrystall...

  13. Análisis experimental del torneado de alta velocidad del acero AISI 1045 // Experimental analysis of high speed turning of AISI 1045 steel gears

    Luís Wilfredo Hernández‐González

    2012-01-01

    Full Text Available El objetivo de este trabajo es el estudio experimental de la evolución del desgaste del flanco de dosinsertos de carburo recubiertos y un cermet, durante el torneado en seco del acero AISI 1045 con 500 y600 m/min de velocidad de corte. Los resultados fueron comparados utilizando el análisis de varianza y deregresión. La investigación mostró un efecto significativo de la velocidad de corte y del tiempo demaquinado en el desgaste del flanco. El mejor desempeño fue para el carburo recubierto con tres capas,mientras que a elevada velocidad de corte el carburo con dos capas sufrió el mayor desgaste, lo cual sedebe a que cuando pierde sus recubrimientos el substrato del inserto queda desprotegido y el desgastecrece rápidamente por la extremas condiciones del mecanizado por alta velocidad. Además, se planteanrecomendaciones del tiempo de maquinado de los insertos dadas las condiciones de elaboración por altavelocidad.Palabras claves: torneado de alta velocidad, desgaste del flanco, acero AISI 1045, estudio experimental.__________________________________________________________________________AbstractThis work deals with the experimental study of the flank wear evolution of two coating carbide inserts and acermet insert during the dry turning of AISI 1045 steel with 500 and 600 m/min cutting speed. The resultswere compared using the variance and regression analysis. The investigation showed a significant effectof cutting speed and machining time on the flank wear in high speed machining. The three coating layersinsert showed the best performance while the two layers insert had the worst behaviour of the cutting toolwear at high cutting speed, this is because once the coating film is peeled off, the substrate of the insertbecomes uncovered and the wear grows rapidly due to the extreme machining conditions for high speed.Besides, the machining time recommendations of inserts for the cutting conditions at high speed areexposed.Key words: high

  14. Qualidade de vida de pacientes submetidos ao transplante cardíaco: aplicação da escala Whoqol-Bref Calidad de vida de pacientes sometidos a transplante cardíaco: aplicación de la escala Whoqol-Bref Quality of life of patients that had a heart transplant: application of Whoqol-Bref scale

    Maria Isis Freire de Aguiar; Deisiana Rios Farias; Mabel Leite Pinheiro; Emília Soares Chaves; Isaura Letícia Tavares Palmeira Rolim; Paulo César de Almeida

    2011-01-01

    FUNDAMENTO: O sucesso do transplante cardíaco significa garantir a sobrevida dos pacientes com cardiopatia e permitir-lhes desenvolver suas atividades diárias. O transplante cardíaco apresenta-se como a primeira opção de tratamento na falência cardíaca, representando um aumento de sobrevida e qualidade de vida dos transplantados. OBJETIVO: Avaliar a qualidade de vida de pacientes submetidos ao transplante cardíaco através da aplicação de uma escala padronizada (Whoqol-Bref). MÉTODOS: Estudo e...

  15. Behavior of AISI SAE 1020 steel implanted by titanium and exposed to bacteria sulphate deoxidizer

    A hybrid technology to treat solid surfaces with the pulse high voltage and electric arc discharges of low pressure with a three-dimensional ion implantation technique (3DII) is applied. This technology is used to protect AISI SAE 1020 steel against a microbiological corrosion. The titanium ion implanted steel samples (coupons) are subjected to a medium of bacteria sulphate deoxidizer (BSD) which are very typical of the hydrocarbon industry and are potentially harmful for structures when are in contact with petroleum and some of its derivatives. The used technology aims to find an effective hybrid procedure to minimize the harmful effects of bacteria on AISI SAE 1020 steel. The hybrid technology efficiency of superficial titanium implantation is estimated through the measurements of the point corrosion characteristics obtained after testing both the treated and non-treated coupons. The three-dimensional surface structures of the samples are reconstructed with help of a confocal microscope.

  16. Experimental study of mechanical properties of friction welded AISI 1021 steels

    Amit Handa; Vikas Chawla

    2013-12-01

    Friction welding is widely used as a mass production method in various industries. In the present study, an experimental set-up was designed in order to achieve friction welding of plastically deformed AISI 1021 steels. In this study, low alloy steel (AISI 1021) was welded under different welding parameters and afterwards the mechanical properties such as tensile strength, impact strength and hardness were experimentally determined. On the basis of the results obtained from the experimentation, the graphs were plotted. It is the strength of welded joints, which is fundamental property to the service reliability of the weldments and hence present work was undertaken to study the influence of axial pressure and rotational speed in friction welded joints. Axial pressure and rotational speed are the two major parameters which can influence the strength and hence the mechanical properties of the friction welded joints. Thus the axial pressure and rotational speed were taken as welding parameters, which reflect the mechanical properties.

  17. Evaluation of structural behaviour and corrosion resistant of austenitic AISI 304 and duplex AISI 2304 stainless steel reinforcements embedded in ordinary Portland cement mortars; Evaluacion del comportamiento estructural y de resistencia a la corrosion de armaduras de acero inoxidable austenitico AISI 304 y duplex AISI 2304 embebidas en morteros de cemento Portland

    Medina, E.; Cobo, A.; Bastidas, D. M.

    2012-07-01

    The mechanical and structural behaviour of two stainless steels reinforcements, with grades austenitic EN 1.4301 (AISI 304) and duplex EN 1.4362 (AISI 2304) have been studied, and compared with the conventional carbon steel B500SD rebar. The study was conducted at three levels: at rebar level, at section level and at structural element level. The different mechanical properties of stainless steel directly influence the behaviour at section level and structural element level. The study of the corrosion behaviour of the two stainless steels has been performed by electrochemical measurements, monitoring the corrosion potential and the lineal polarization resistance (LPR), of reinforcements embedded in ordinary Portland cement (OPC) mortar specimens contaminated with different amount of chloride over one year time exposure. Both stainless steels specimens embedded in OPC mortar remain in the passive state for all the chloride concentration range studied after one year exposure. (Author) 26 refs.

  18. AFM surface imaging of AISI D2 tool steel machined by the EDM process

    The surface morphology, surface roughness and micro-crack of AISI D2 tool steel machined by the electrical discharge machining (EDM) process were analyzed by means of the atomic force microscopy (AFM) technique. Experimental results indicate that the surface texture after EDM is determined by the discharge energy during processing. An excellent machined finish can be obtained by setting the machine parameters at a low pulse energy. The surface roughness and the depth of the micro-cracks were proportional to the power input. Furthermore, the AFM application yielded information about the depth of the micro-cracks is particularly important in the post treatment of AISI D2 tool steel machined by EDM

  19. AFM surface imaging of AISI D2 tool steel machined by the EDM process

    Guu, Y.H. [Department of Mechanical Engineering, National United University, 1 Lien Da, Kung-Ching Li, Miaoli 360, Taiwan (China)]. E-mail: yhorng@nuu.edu.tw

    2005-04-15

    The surface morphology, surface roughness and micro-crack of AISI D2 tool steel machined by the electrical discharge machining (EDM) process were analyzed by means of the atomic force microscopy (AFM) technique. Experimental results indicate that the surface texture after EDM is determined by the discharge energy during processing. An excellent machined finish can be obtained by setting the machine parameters at a low pulse energy. The surface roughness and the depth of the micro-cracks were proportional to the power input. Furthermore, the AFM application yielded information about the depth of the micro-cracks is particularly important in the post treatment of AISI D2 tool steel machined by EDM.

  20. Tool life and surface roughness of ceramic cutting tool when turning AISI D2 tool steel

    The tool life of physical vapor deposition (PVD) titanium nitride (TiN) coated ceramic when turning AISI D2 tool steel of hardness 54-55 HRC was investigated. The experiments were conducted at various cutting speed and feed rate combinations with constant depth of cut and under dry cutting condition. The tool life of the cutting tool for all cutting conditions was obtained. The tool failure mode and wear mechanism were also investigated. The wear mechanism that is responsible for the wear form is abrasion and diffusion. Flank wear and crater wear are the main wear form found when turning AISI D2 grade hardened steel with 54-55 HRC using KY 4400 ceramic cutting tool. Additionally catastrophic failure is observed at cutting speed of 183 m/min and feed rate of 0.16 mm/ rev. (author)

  1. Analysis of pulsed Nd:YAG laser welding of AISI 304 steel

    Pulsed laser welding of AISI 304 stainless steel plate was simulated using commercial finite element software to determine the optimal welding conditions. Due to geometric symmetry, only one plate was modeled to reduce the simulation computation time. User subroutines were created to account for a moving three-dimensional heat source and to apply boundary conditions. The material properties such as conductivity, specific heat, and mass density were determined as functions of temperature. The latent heat was considered within the given temperature range. The three-dimensional heat source model for pulsed laser beam butt welding was designed by comparing the finite element analysis results and experimental data. This successful simulation of pulsed Nd:YAG laser welding for AISI 304 stainless steel will prove useful for determining optimal welding conditions

  2. Radiation-induced evolution of austenite matrix in silicon-modified AISI 316 alloys

    The microstructures of a series of silicon-modified AISI 316 alloys irradiated to fast neutron fluences of about 2-3 and 10 x 1022 n/cm2 (E > 0.1 MeV at temperatures ranging from 4000C to 6000C have been examined. The irradiation of AISI 316 leads to an extensive repartition of several elements, particularly nickel and silicon, between the matrix and various precipitate phases. The segregation of nickel at void and grain boundary surfaces at the expense of other faster-diffusing elements is a clear indication that one of the mechanisms driving the microchemical evolution is the Inverse Kirkendall effect. There is evidence that at one sink this mechanism is in competition with the solute drag process associated with interstitial gradients

  3. Martensitic transformation on AISI 304 stainless steel produced by a coaxial plasma gun

    Full text: In a previous paper, a surface treatment of AISI 304 stainless steel irradiated by a Nitrogen ion beam generated in a coaxial plasma gun has been reported. The device is operated with a Titanium insert at the end of the inner electrode, producing a TiN coating on the surface of the sample. Because of the ion and plasma energy deposition, the sample surface is strongly heated during the treatment resulting in titanium diffusion. Preliminary X-ray diffraction (XRD) studies have shown the presence of a martensitic transformation on AISI 304 samples, probably induced by Ti atoms. In this work, the transformation depth is studied with grazing-incidence XRD on samples subjected to several superimposed shots. For this purpose, multiple low angles of incidence are used, allowing the analysis at different depths of the substrate

  4. Analysis of pulsed Nd:YAG laser welding of AISI 304 steel

    Kim, Kwan Woo; Lee, Jung Kil; Cho, Hae Yong [Chungbuk National University College of Medicine, Jeonju (Korea, Republic of)

    2010-11-15

    Pulsed laser welding of AISI 304 stainless steel plate was simulated using commercial finite element software to determine the optimal welding conditions. Due to geometric symmetry, only one plate was modeled to reduce the simulation computation time. User subroutines were created to account for a moving three-dimensional heat source and to apply boundary conditions. The material properties such as conductivity, specific heat, and mass density were determined as functions of temperature. The latent heat was considered within the given temperature range. The three-dimensional heat source model for pulsed laser beam butt welding was designed by comparing the finite element analysis results and experimental data. This successful simulation of pulsed Nd:YAG laser welding for AISI 304 stainless steel will prove useful for determining optimal welding conditions

  5. Experimental Investigation of the Effect of Burnishing Force on Service Properties of AISI 1010 Steel Plates

    Gharbi, F.; Sghaier, S.; Morel, F.; Benameur, T.

    2015-02-01

    This paper presents the results obtained with a new ball burnishing tool developed for the mechanical treatment of large flat surfaces. Several parameters can affect the mechanical behavior and fatigue of workpiece. Our study focused on the effect of the burnishing force on the surface quality and on the service properties (mechanical behavior, fatigue) of AISI 1010 steel hot-rolled plates. Experimental results assert that burnishing force not exceeding 300 N causes an increase in the ductility. In addition, results indicated that the effect of the burnishing force on the residual surface stress was greater in the direction of advance than in the cross-feed direction. Furthermore, the flat burnishing surfaces did not improve the fatigue strength of AISI 1010 steel flat specimens.

  6. INFLUENCE OF AISI 316Ti STAINLESS STELL SURFACE TREATMENT ON PITTING CORROSION IN VARIOUS SOLUTIONS

    Pavol Fajnor

    2010-12-01

    Full Text Available Investigation of the surface treatment effect on the resistance of AISI 316Ti stainless steel to pitting corrosion is presented in this paper. The grinded surfaces without additional chemical treatment, grinded and pickled, grinded, pickled and passivated surfaces are tested. The corrosion tests are carried out by exposition in solution which evoke pitting and by electrochemical cyclic potential - sweep method. According to the results the surface treatment has a great influence on the resistance of the tested material to pitting. It is not possible to estimate the best surface treatment because behavior of AISI 316Ti stainless steel with different surface state depends on the mechanism of corrosion processes which vary in the used experimental methods.

  7. Corrosion resistance of the welded AISI 316L after various surface treatments

    Tatiana Liptáková

    2014-01-01

    Full Text Available The main aim of this work is to monitor the surface treatment impact on the corrosion resistance of the welded stainless steel AISI 316L to local corrosion forms. The excellent corrosion resistance of austenitic stainless steel is caused by the existence of stable, thin and well adhering passive layer which quality is strongly influenced by welding. Therefore surface treatment of stainless steel is very important with regard to its local corrosion susceptibility Surfaces of welded stainless steel were treated by various mechanical methods (grinding, garnet blasting. Surface properties were studied by SEM, corrosion resistance was evaluated after exposition tests in chlorides environment using weight and metalographic analysis. The experimental outcomes confirmed that the mechanical finishing has a significant effect on the corrosion behavior of welded stainless steel AISI 316L.

  8. Embrittlement and strain hardining of the hydrogenated AISI 304 austenitic stainless steel

    The influence of hydrogen the mechanical properties of type AISI 304 austenitic stainless steel was analysed. Hydrogenation was performed cathodically, at room temperature, in a 1N H2SO4 solution. The variables controlled for analysis were current density and time. Uniaxial tensile tests were conducted with constant nominal strain rate. Fracture morphology was analysed by scanning electron microscopy and the kinetics of strain hardening by applying Ludwick's equation to the resulting stress-strain curves. It was verified that hydrogen embrittles markedly, the austenitic AISI 304 steel, leading to a significant loss of ductility and modifying the fracture made, from essentially ductile to a transgrannular fragile fracture, containing small regions of intergranular fracture. With increasing amounts of hydrogen there was also a decrease in the maximum uniform stress, the strength coefficient, the strain hardening exponent and in the range the deformation stages II and III extended. (Author)

  9. Microhardness measurement in AISI 321 stainless steel with niobium additions before and after fast neutron irradiation

    Data about influence of neutron irradiation on the microhardness of stainless steel of type AISI 321 with 0.05 and 0.1wt.% Nb additions are presented. The microhardness measurements were made in the range of 300 to 6500C, before and after fast neutron irradiation with fluences about 1017n/cm2. Our results indicate that radiation damage peaks occur around 4800C for the stainless steel of type AISI 321 without Nb addition, around 5000C for the composition with 0.05 wt.% Nb addition and around 5700C for the composition with 0.1 wt.% Nb addition. Microhardness data are in agreement with those obtained by means of electrical resistivity measurements, performed at the same conditions. (Author)

  10. Oxidation behavior of 26Cr-16Ni and AISI 309 austenitic stainless steels in air flow at 1,173 K

    Pipatnukun, Peeraya; Wangyao, Panyawat; Lothongkum, Gobboon [Chulalongkorn Univ., Bangkok (Thailand). Dept. of Metallurgical Engineering

    2015-11-01

    This work investigates the isothermal oxidation behavior of as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 at 1,173 K in air flow rate of 40 cm{sup 3} x min{sup -1} using thermogravimetric analysis (TGA). In 33 hours, the oxidation resistance declines from high to low are as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309, respectively. The oxidation kinetic results show that the exponential rate constant of the as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 are 8.79 x 10{sup -6}, 4.02 x 10{sup -5} and 4.35 x 10{sup -5} g x cm{sup -2} x s{sup -n}, respectively. The exponential growth rates of as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 are 0.42, 0.29 and 0.32, respectively. It indicates that the oxidation kinetic of as cast 26Cr-16Ni approaches a parabolic rate law, but those of as cold-rolled and as cast AISI 309 approach the cubic rate law. The sequence of oxide scale formations on the tested samples is also discussed.

  11. Oxidation behavior of 26Cr-16Ni and AISI 309 austenitic stainless steels in air flow at 1,173 K

    This work investigates the isothermal oxidation behavior of as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 at 1,173 K in air flow rate of 40 cm3 x min-1 using thermogravimetric analysis (TGA). In 33 hours, the oxidation resistance declines from high to low are as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309, respectively. The oxidation kinetic results show that the exponential rate constant of the as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 are 8.79 x 10-6, 4.02 x 10-5 and 4.35 x 10-5 g x cm-2 x s-n, respectively. The exponential growth rates of as cast 26Cr-16Ni, as cold-rolled AISI 309 and as cast AISI 309 are 0.42, 0.29 and 0.32, respectively. It indicates that the oxidation kinetic of as cast 26Cr-16Ni approaches a parabolic rate law, but those of as cold-rolled and as cast AISI 309 approach the cubic rate law. The sequence of oxide scale formations on the tested samples is also discussed.

  12. Cathodic cage nitriding of AISI 409 ferritic stainless steel with the addition of CH4

    Rômulo Ribeiro Magalhães de Sousa

    2012-04-01

    Full Text Available AISI 409 ferritic stainless steel samples were nitrided using the cathodic cage plasma nitriding technique (CCPN, with the addition of methane to reduce chromium precipitation, increase hardness and wear resistance and reduce the presence of nitrides when compared to plasma carbonitriding. Microhardness profiles and X-Ray analysis confirm the formation of a very hard layer containing mainly ε-Fe3N and expanded ferrite phases.

  13. Cathodic cage nitriding of AISI 409 ferritic stainless steel with the addition of CH4

    Rômulo Ribeiro Magalhães de Sousa; Francisco Odolberto de Araújo; José Alzamir Pereira da Costa; Antonio Maia de Oliveira; Mineia Sampaio Melo; Clodomiro Alves Junior

    2012-01-01

    AISI 409 ferritic stainless steel samples were nitrided using the cathodic cage plasma nitriding technique (CCPN), with the addition of methane to reduce chromium precipitation, increase hardness and wear resistance and reduce the presence of nitrides when compared to plasma carbonitriding. Microhardness profiles and X-Ray analysis confirm the formation of a very hard layer containing mainly ε-Fe3N and expanded ferrite phases.

  14. Multi-scale modelling of AISI H11 martensitic tool steel surface anisotropic mechanical behaviour

    Zouaghi Ahmed; Velay Vincent; Soveja Adriana; Rézaï-Aria Farhad

    2014-01-01

    In this work, a numerical investigation is carried out on the anisotropic and heterogeneous behaviour of the AISI H11 martensitic tool steel surface using finite element method and a multi-scale approach. An elasto-viscoplastic model that considers nonlinear isotropic and kinematic hardenings is implemented in the finite elements code ABAQUS using small strain assumption. The parameters of the constitutive equations are identified using macroscopic quasi-static and cyclic material responses b...

  15. Optimization of Machining Parameters for improved Surface Integrity of AISI H13 Tool Steel

    OUTEIRO, José

    2012-01-01

    The surface integrity plays a very important rule in this functional performance, being dependent of a large number of machining parameters. The major concern of the industry is to know which combination of machining parameters provides a better surface integrity of the machined components. AISI H13 tool steel has been applied widely to produce many different types of hot working dies due to its excellent mechanical properties, such as: good resistance to thermal softening, high hardenabil...

  16. Laser welding of butt joints of austenitic stainless steel AISI 321

    A. Klimpel

    2007-11-01

    Full Text Available Purpose: of this paper: A study of an automated laser autogenous welding process of butt joints of austenitic stainless steel AISI 321 sheets 0.5 [mm] and 1.0 [mm] thick using a high power diode laser HPDL has been carried out.Design/methodology/approach: Influence of basic parameters of laser welding on shape and quality of the butt joints and the range of optimal parameters of welding were determined.Findings: It was showed that there is a wide range of laser autogenous welding parameters which ensures high quality joints of mechanical strength not lower than the strength of the base material (BM. The butt joints of austenitic steel AISI 321 sheets welded by the HPDL diode laser at optimal parameters are very high quality, without any internal imperfections and the structure and grain size of weld metal and HAZ is very small and also the HAZ is very narrow and the fusion zone is very regular.Research limitations/implications: Studies of the weldability of stainless steels indicate that the basic influence on the quality of welded joints and reduction of thermal distortions has the heat input of welding, moreover the highest quality of welded joints of austenitic stainless steel sheets are ensured only by laser welding.Practical implications: The technology of laser welding can be directly applied for welding of butt joints of austenitic steel AISI 321 sheets 0.5 and 1.0 [mm] thick.Originality/value: Application of high power diode laser for welding of austenitic stainless steel AISI 321.

  17. Structure and properties of the Stainless steel AISI 316 nitrided with microwave plasma

    In this work were presented the results obtained by nitridation on stainless steel AISI 316 using a plasma generated through a microwave discharge with an external magnetic field using several moistures hydrogen / nitrogen to form a plasma. The purpose of nitridation was to increase the surface hardness of stainless steel through a phase formation knew as γN which has been reported that produces such effect without affect the corrosion resistance proper of this material. (Author)

  18. Martensitic Transformation in Ultrafine-Grained Stainless Steel AISI 304L Under Monotonic and Cyclic Loading

    Heinz Werner Höppel

    2012-02-01

    Full Text Available The monotonic and cyclic deformation behavior of ultrafine-grained metastable austenitic steel AISI 304L, produced by severe plastic deformation, was investigated. Under monotonic loading, the martensitic phase transformation in the ultrafine-grained state is strongly favored. Under cyclic loading, the martensitic transformation behavior is similar to the coarse-grained condition, but the cyclic stress response is three times larger for the ultrafine-grained condition.

  19. Sub-surface Fatigue Crack Growth at Alumina Inclusions in AISI 52100 Roller Bearings

    Cerullo, Michele

    2014-01-01

    damage factor is highest. Subsequently the stress history is imposed as boundary conditions in a periodic unit cell model, where an alumina inclusion is embedded in a AISI 52100 matrix. Cracks are assumed to grow radially from the inclusion under cyclic loading. The growth is predicted by means of...... irreversible fatigue cohesive elements. Different orientations of the cracks and different matrix-inclusion bonding conditions are analyzed and compared....

  20. Metallurgical response of an AISI 4140 steel to different plasma nitriding gas mixtures

    Adão Felipe Oliveira Skonieski; Giovanni Rocha dos Santos; Thomas Karl Hirsch; Alexandre da Silva Rocha

    2013-01-01

    Plasma nitriding is a surface modification process that uses glow discharge to diffuse nitrogen atoms into the metallic matrix of different materials. Among the many possible parameters of the process, the gas mixture composition plays an important role, as it impacts directly the formed layer's microstructure. In this work an AISI 4140 steel was plasma nitrided under five different gas compositions. The plasma nitriding samples were characterized using optical and scanning electron microscop...

  1. Deposition and characterization of duplex treated coating system applied on hot work steel AISI H13

    Bejarano Gait??n, Gilberto; Arroyave Franco, Mauricio; G??mez Botero, Maryori

    2015-01-01

    AISI H13 steel is widely used for extrusion moulds and other hot work tools fabrication, due to its high toughness, strength and hardness around 56 HRC (Rockwell C) -- However, this steel possesses a relatively low wear resistance, which reduces its life time under high loading conditions -- The aim of this work was to enhance the wear resistance of the steel H13 using the following surface treatments:austenitizing + quenching + tempering (further called ???tempering???), tempering and bath n...

  2. Corrosion behaviour of AISI 316L steel in artificial body fluids

    W. Kajzer

    2008-12-01

    Full Text Available Purpose: The paper presents the comparison of corrosion resistance of AISI 316L stainless steel in various corrosive media such as artificial urine, Tyrode’s physiological solution and artificial plasma.Design/methodology/approach: The tests were carried out on samples of the following surfaces: grinded – average roughness Ra = 0.31 μm and electropolished and chemically passivated average roughness Ra = 0.10 μm. The corrosion tests were realized by recording of anodic polarization curves with the use of the potentiodynamic method. The VoltaLab® PGP 201 system for electrochemical tests was applied. The tests were carried out in electrolyte simulating urine (pH = 6-6.4, Tyrode’s physiological solution (pH = 6.8-7.4 and plasma (pH = 7.2-7.6 at the temperature of 37±1°C.Findings: Surface condition of AISI 316L stainless steel determines its corrosion resistance. The highest values of breakdown potentials were recorded for all electropolished and chemically passivated samples in all simulated body fluids. The highest values of anodic current density were recorded for samples tested in artificial urine, the lowest values were recorded for samples tested in Tyrode’s physiological solution.Research limitations/implications: The obtained results are the basis for the optimization of physicochemical properties of the AISI 316L stainless steel.Practical implications: On the basis of the obtained results it can be stated that stainless steel meets the basic biocompatibility criteria and can be applied in reconstruction surgery, operative cardiology and urology.Originality/value: The paper presents the influence of various corrosive media simulating human body fluids on corrosion resistance of AISI 316L stainless steel.

  3. Study of corrosion resistance of AISI 444 ferritic stainless steel for application as a biomaterial

    Ferritic stainless steels are ferromagnetic materials. This property does not allow their use in orthopedic prosthesis. Nevertheless, in some specific applications, this characteristic is very useful, such as, for fixing dental and facial prostheses by using magnetic attachments. In this study, the corrosion resistance and cytotoxicity of the AISI 444 ferritic stainless steel, with low nickel content, extra-low interstitial levels (C and N) and Ti and Nb stabilizers, were investigated for magnetic dental attachments application. The ISO 5832-1 (ASTM F-139) austenitic stainless steel and a commercial universal keeper for dental attachment (Neo-magnet System) were evaluated for comparison reasons. The first stainless steel is the most used metallic material for prostheses, and the second one, is a ferromagnetic keeper for dental prostheses (NeoM). In vitro cytotoxicity analysis was performed by the red neutral incorporation method. The results showed that the AISI 444 stainless steel is non cytotoxic. The corrosion resistance was studied by anodic polarization methods and electrochemical impedance spectroscopy (EIS), in a saline phosphate buffered solution (PBS) at 37 °C. The electronic properties of the passive film formed on AISI 444 SS were evaluated by the Mott-Schottky approach. All tested materials showed passivity in the PBS medium and the passive oxide film presented a duplex nature. The highest susceptibility to pitting corrosion was associated to the NeoM SS. This steel was also associated to the highest dopant concentration. The comparatively low levels of chromium (nearly 12.5%) and molybdenum (0.3%) of NeoM relatively to the other studied stainless steels are the probable cause of its lower corrosion resistance. The NeoM chemical composition does not match that of the SUS444 standards. The AISI 444 SS pitting resistance was equivalent to the ISO 5832-1 pointing out that it is a potential candidate for replacement of commercial ferromagnetic alloys used

  4. The influence of microstruture on fracture toughness of vacuum heat treated HSS AISI M2

    Leskovšek, Vojteh; Ule, Boris; Liščić, Božidar

    2015-01-01

    The microstructure of AISI M2 high-speed can be substantially modified by vacuum heat treatment in order to optimize the ratio between hardness and fracture toughness, which is, however, significantly affected by the volume fractions of retained austenite and undissolved eutectic carbides, as well as the mean distance between these carbides. Calculated fracture toughness values, which were obtained using a newly developed semi-empirical equation, based on the stress-modified critical strain c...

  5. Influence of the surface finishing on the corrosion behaviour of AISI 316L stainless steel

    Dundeková, S.; Zatkalíková, V.; Fintová, Stanislava; Hadzima, B.; Škorík, Viktor

    2015-01-01

    Roč. 22, č. 1 (2015), s. 48-53. ISSN 1335-0803 R&D Projects: GA MŠk(CZ) EE2.3.30.0063 Institutional support: RVO:68081723 Keywords : AISI 316L stainless steel * Corrosion * Immersion test * Corrosion rate Subject RIV: JK - Corrosion ; Surface Treatment of Materials http://ojs.mateng.sk/index.php/Mateng/article/view/166/251

  6. AN ELECTROCHEMICAL PROCESSING STRATEGY FOR IMPROVING TRIBOLOGICAL PERFORMANCE OF AISI 316 STAINLESS STEEL UNDER GREASE LUBRICATION

    JIAOJUAN ZOU; MAOLIN LI; NAIMING LIN; XIANGYU ZHANG; LIN QIN; BIN TANG

    2014-01-01

    In order to improve the tribological performance of AISI 316 stainless steel (316 SS) under grease lubrication, electrochemical processing was conducted on it to obtain a rough (surface texturing-like) surface by making use of the high sensitivity of austenitic stainless steel to pitting corrosion in Cl--rich environment. Numerous corrosion pits or micro-ditches acted as micro-reservoirs on the obtained surface. While the grease could offer consistent lubrication, and then improve the tribolo...

  7. Carbides crystalline structure of AISI M2 high-speed steel

    The aim of this study was to identify the crystallographic structure of the extracted carbides of AISI M2 steel spray formed The structure determination of these carbides. The structure determination of these carbides is a very hard work. Since these structures were formed by atom migration it is not possible to reproduce them by a controlled process with a determined chemical composition. The solution of this problem is to obtain the carbide by chemical extraction from the steel. (Author)

  8. The structure of austenitic steel AISI 316 after ECAP and low-cycle fatigue

    L. Kander

    2008-06-01

    Full Text Available Purpose: The article presents results of investigation of structure and properties of austenitic steel grade AISI 316 after application of Equal Channel Angular Pressing (ECAP at the temperature of approx. 290ºC.Design/methodology/approach: The ECAP method led to significant improvement of strength of investigated material. Experiments were planned and realised at the temperature ranging from room temperature up to above mentioned temperature.Findings: It was established with use of the EBSD technique that after 8 passes through the ECAP die the sub-grains with an angle of disorientation smaller than 10º formed less than 20% of resulting structure. Average size of austenitic grains with high angle boundary after 8 passes was approx. 0.32 µm. It was proven that the ECAP method enables obtaining of ultra fine-grained austenitic structure formed by recrystallised grains with very low density of dislocations.Practical implications: The Technology ECAP was applied on austenitic steel AISI 316. It was verification of ECAP application possibility on steel AISI 316 importantly for following applying on similar kinds of steel, because ECAP technology influence on fatigue properties was confirmed.Originality/value: It can be predicted on the basis of obtained results that, contrary to low-cycle fatigue the ultra-fine grained material will manifest at fatigue load in the mode of constant amplitude of stress higher fatigue characteristics, particularly fatigue limit.

  9. Wear resistance of Fe-Nb-Cr-W, Nb, AISI 1020 and AISI 420 coatings produced by thermal spray wire arc; Resistencia al desgaste de recubrimientos Fe-Nb-Cr-W, Nb, AISI 1020 y AISI 420 producidos por proyeccion termica por arco electrico

    Lopez-Covaleda, E. A.; Mercado-Veladia, J. L.; Olaya-Florez, J. J.

    2013-07-01

    The commercial materials 140MXC (with iron, tungsten, chrome, niobium), 530AS (AISI 1015 steel) and 560AS (AISI 420 steel) on AISI 4340 steel were deposited using thermal spray with arc. The aim of work was to evaluate the best strategy abrasive wear resistance of the system coating-substrate using the following combinations: (1) homogeneous coatings and (2) coatings depositing simultaneously 140MXC + 530AS and 140MXC + 560AS. The coatings microstructure was characterized using Optical microscopy, Scanning electron microscopy and Laser con focal microscopy. The wear resistance was evaluated through dry sand rubber wheel test (DSRW). We found that the wear resistance depends on the quantity of defects and the mechanical properties like hardness. For example, the softer coatings have the biggest wear rates and the failure mode was characterized by plastic deformation caused by particles indentation, and the other hand the failure mode at the harder materials was grooving. The details and wear mechanism of the coatings produced are described in this investigation. (Author)

  10. Structure and low-cycle fatigue of steel AISI 316 after ECAP

    M. Greger

    2008-05-01

    Full Text Available Purpose: Main aim of this paper is to describe the plastic deformation executed by ECAP on low cycle fatigueof steel AISI 316. Among others was attention fixed on mechanical properties after this treatment.Design/methodology/approach: Experiments were planned and realised at the temperature ranging fromroom temperature up to 280 °C. After application of deformation the structure was investigated in dependence onaccumulation of deformation and deformation temperature as well as abovementioned final properties.Findings: Accumulated real (logarithmic deformation varied from the value 2 to 8. Investigation of structure byelectron microscopy was made with use of microscope JEOL JEM 2100. Mechanical properties were investigatedby conventional tensile test and penetration test. Selected samples were subjected to low-cycle fatigue. Statisticevaluation of angular disorientation and of size of grains/sub-grains was also made with use of electron diffraction(EBSD in combination with scanning electron microscope FEG SEM Philips.Practical implications: The Technology ECAP was applied on austenitic steel AISI 316. It was verificationof ECAP application possibility on steel AISI 316 importantly for following applying on similar kinds of steel,because ECap technology influence on fatigue properties was confirmed.Originality/value: It can be predicted on the basis of obtained results that, contrary to low-cycle fatigue theultra-fine grained material will manifest at fatigue load in the mode of constant amplitude of stress higher fatiguecharacteristics, particularly fatigue limit.

  11. Stoichiometric titanium dioxide ion implantation in AISI 304 stainless steel for corrosion protection

    Hartwig, A.; Decker, M.; Klein, O.; Karl, H.

    2015-12-01

    The aim of this study is to evaluate the applicability of highly chemically inert titanium dioxide synthesized by ion beam implantation for corrosion protection of AISI 304 stainless steel in sodium chloride solution. More specifically, the prevention of galvanic corrosion between carbon-fiber reinforced plastic (CFRP) and AISI 304 was investigated. Corrosion performance of TiO2 implanted AISI 304 - examined for different implantation and annealing parameters - is strongly influenced by implantation fluence. Experimental results show that a fluence of 5 × 1016 cm-2 (Ti+) and 1 × 1017 cm-2 (O+) is sufficient to prevent pitting corrosion significantly, while galvanic corrosion with CFRP can already be noticeably reduced by an implantation fluence of 5 × 1015 cm-2 (Ti+) and 1 × 1016 cm-2 (O+). Surface roughness, implantation energy and annealing at 200 °C and 400 °C show only little influence on the corrosion behavior. TEM analysis indicates the existence of stoichiometric TiO2 inside the steel matrix for medium fluences and the formation of a separated metal oxide layer for high fluences.

  12. Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy and magnetic measurements on thermally oxidized AISI 304 and AISI 316 stainless steels

    Maachi, B. [Universite d' Oran, Laboratoire de Physique des Couches Minces et Materiaux pour l' Electronique (LPC2ME), BP 1524, El M' Naouer, 31000 Oran (Algeria); Pirri, C.; Mehdaoui, A. [Universite de Haute Alsace (UHA), Institut de Science des Materiaux de Mulhouse (IS2M), LRC 7228 - CNRS, 4 rue des freres Lumiere, 68093 Mulhouse (France); Hakiki, N.E., E-mail: hakiki.nourredine@yahoo.f [Universite d' Oran, Laboratoire de Physique des Couches Minces et Materiaux pour l' Electronique (LPC2ME), BP 1524, El M' Naouer, 31000 Oran (Algeria); Bubendorff, J.L., E-mail: jean-luc.bubendorff@uha.f [Universite de Haute Alsace (UHA), Institut de Science des Materiaux de Mulhouse (IS2M), LRC 7228 - CNRS, 4 rue des freres Lumiere, 68093 Mulhouse (France)

    2011-03-15

    Research highlights: {yields} The surface roughness of the bare substrate influence the oxide layer growth. {yields} The oxide layer roughness follows power laws and belongs to universality class. {yields} At low growth temperature, the p-n heterojunction disappears in some places. {yields} SKPFM images allow the direct visualization of local corrosion sites. {yields} Presence of a magnetite phase in the outer iron rich layer of the oxide thin film. - Abstract: Thermally oxidized AISI304 and AISI316 stainless steels are studied by Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy (SKPFM) and Magneto-Optical Kerr effect as a function of their growth temperature. The surface roughness is a competition between the roughness of the bare substrate and the roughness resulting from the oxide layer growth. Cr oxide is present at some places on the surface at low growth temperature as shown by SKPFM. The observed decrease of surface potential with the oxide layer thickness indicates an effective protection against corrosion. Magnetic measurements demonstrate that the outer layer contains a magnetite phase (in-plane magnetization).

  13. Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy and magnetic measurements on thermally oxidized AISI 304 and AISI 316 stainless steels

    Research highlights: → The surface roughness of the bare substrate influence the oxide layer growth. → The oxide layer roughness follows power laws and belongs to universality class. → At low growth temperature, the p-n heterojunction disappears in some places. → SKPFM images allow the direct visualization of local corrosion sites. → Presence of a magnetite phase in the outer iron rich layer of the oxide thin film. - Abstract: Thermally oxidized AISI304 and AISI316 stainless steels are studied by Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy (SKPFM) and Magneto-Optical Kerr effect as a function of their growth temperature. The surface roughness is a competition between the roughness of the bare substrate and the roughness resulting from the oxide layer growth. Cr oxide is present at some places on the surface at low growth temperature as shown by SKPFM. The observed decrease of surface potential with the oxide layer thickness indicates an effective protection against corrosion. Magnetic measurements demonstrate that the outer layer contains a magnetite phase (in-plane magnetization).

  14. A study on the control of melting ratio to increase mechanical properties of laser welded joints between AISI 440C and AISI 430F

    Romoli, L.; Rashed, C. A. A.; Lovicu, G.; Ishak, R.

    2015-05-01

    Laser beam welding of dissimilar AISI 440C and AISI 430F stainless steels was investigated in a circular constrained configuration. The beam incidence angle and the offset of the focusing position respect to the contact point between the two materials were used as main control parameters to vary the melting ratio inside the seam. The objective of the study is twofold: to avoid surface microcracks related to the high percentage of carbon of the martensitic steel and to enhance the shear strength of the weld by making it less brittle. To reach this scope the effects of incidence angle and offset on weld bead geometry and melting ratio were studied by means of metallographic analyses, microstructure and microhardness characterization. As last step, the weld mechanical strength was tested by tensile-shear stress test on the whole seam. Experiments demonstrated that varying incidence angle and offsetting the focal position is a reliable method to modify the melting ratio and maintaining the expected resistance length at the material interface, as well. It was found that increasing the percentage of ferritic steel into the joint has beneficial effects on the weld quality and on the shear resistance. The critical carbon content determining the mechanical properties in the fusion zone can be calculated by taking into account the melting ratio.

  15. Transplante cardíaco humano: experiência inicial Human cardiac transplant: initial experience

    Noedir A. G Stolf

    1986-12-01

    Full Text Available No Instituto do Coração, de março de 1985 a fevereiro de 1986,11 pacientes foram submetidos a transplante cardíaco ortotópico. Eram todos do sexo masculino, com idade variando de 39 a 54 anos; 6 com cardiopatia isquémica, 4 com cardiomiopatia dilatada e um com cardiomiopatia chagásica. Foi realizado estudo hemodinâmico através de catéter de Swan-Ganz, no pré-operatório, no pós-operatório, após estabilização na unidade de recuperação, e trinta ou mais dias após o transplante. Os dados mostram melhora progressiva em relação ao índice cardíaco, pressão em artéria pulmonar, pressão de capilar pulmonar, resistência vascular pulmonar e resistência vascular sistêmica. Três dos 11 pacientes apresentaram disfunção renal transitória no pós-operatório imediato e que regrediram até o 15º dia, enquanto que 2 pacientes apresentaram aumento moderado da creatinina plasmática. Apenas 3 pacientes não apresentaram qualquer episódio de rejeição; nos demais, esses episódios foram um diagnóstico histológico sem repercussões clínicas. Complicações infecciosas ocorreram em 9 pacientes e foram de fácil controle clínico. No pós-operatório tardio, a hipertensão esteve presente em 8 pacientes, sendo mais acentuada em 2 deles. Não houve óbitos, nesta série de pacientes; todos estão assintomáticos e os 6 primeiros estão trabalhando.At the Instituto do Cora��ão, University of São Paulo Medical School, 11 patients were submitted to heart transplantation from march 1985 up to february 1986. All were male, with ages of 39-59 years, 6 with coronary heart disease, 4 with dilated cardiomyopathy and 1 with Chagas cardiomyopathy. The patients were studied hemodynamically with a Swan-Ganz catheter pre-operatively, at the arrival in the intensive care unit, in the first postoperative day and 30 or more days after the transplant. The data showed that there was a progressive increase of cardiac index and decreases of

  16. Changes in oxidative stress in transgenic RNAi ACO1 tomato fruit during ripening

    Eglous, Najat Mohamed; Ali, Zainon Mohd; Hassan, Maizom; Zainal, Zamri

    2013-11-01

    Tomato (Solanum Lycopersicum L.) is the second most cultivated vegetable in the world and widely used as a system for studying the role of ethylene during fruit ripening. Our objective was to study the oxidative stress and antioxidative metabolism during ripening of non transgenic tomato and transgenic line-21 tomato which reduced ethylene. The line-21 of transgenic tomato plants (RNAi ACO1) had lower ethylene production and longer shelf-life more than 32 days as compared to the wild-type fruits which have very short shelf-life. In this study, tomato fruit were divided into five different stages (MG: mature green 5%, B: breaker 25%, T: turning 50%, O: orange75%, RR: red ripe100%). The activity of lipoxygenase (LOX) and lipid peroxidation (MDA) were measured to assess changes in oxidative stress. The LOX activity and MDA content decreased significantly obtaining 2.6-fold and 1.2-fold, respectively, as compared to the wild type fruit. However, superoxide dismutase (SOD) and catalase (CAT) activities were increased to 1.9 and 1.2 folds from the mature green to the fully ripe stage in transgenic tomatoes. Furthermore, the wild type tomato increases 1.3 in SOD and 1.6 in CAT activities. The overall results indicate that the wild type tomato fruit showed a faster rate of ripening, parallel to decline in the rate of enzymatic antioxidative systems as compared to the transgenic line-21 tomato fruit. In addition, the results show that the antioxidant capacity is improved during the ripening process and is accompanied by an increase in the oxidative stress.

  17. Ultrasonic evaluation of friction stud welded AA 6063/AISI 1030 steel joints

    Highlights: • Friction stud welding of AA 6063 and AISI 1030 was done successfully. • Ultrasonic evaluation of interfacial properties. • EDX analysis confirms intermetallic compound (FeAl) in the interfacial region. - Abstract: Friction stud welding is a promising technique in many applications related to oil and gas industries. It is used to attach grating to offshore oil platforms in areas where arc welding is not permitted because of the risk of causing a fire or explosion. Attachment of anodes inside seawater discharge pipelines in a gas processing plant is performed by this process. This solid state joining process permits metal combinations such as welding of aluminum studs to steel which would be problematic with arc welding because of the formation of thick and brittle inter-metallic compounds. In the present work, AA 6063 is joined to AISI 1030 steel using friction stud welding machine. Properties that are of interest to manufacturing applications such as Young’s modulus, longitudinal velocity, bulk modulus and shear modulus are evaluated by means of an ultrasonic flaw detector. At the interface of the joint, there is an increase of 4.4%, 1.8%, 1.15% and 4.42% is observed for the properties Young’s modulus, longitudinal velocity, bulk modulus and shear modulus respectively. This is due to the formation of intermetallic compound and increase in hardness at the interfacial region. Energy Dispersive X-ray analysis confirms the presence of FeAl as the intermetallic compound. Scanning Electron Microscope evaluation shows the presence of an unbound zone at the center of the inner region which is due to the minimum rotational speed and low axial load experienced at that point. In the unbound zone, there is an incomplete bond between dissimilar metals and it is detrimental to joint strength. Optimum value of friction time and usage of pure aluminum interlayer during the friction stud welding process hinders the formation of unbound zone and enhances the

  18. SmartPATH: An Efficient Hybrid ACO-GA Algorithm for Solving the Global Path Planning Problem of Mobile Robots

    Imen Châari

    2014-07-01

    Full Text Available Path planning is a fundamental optimization problem that is crucial for the navigation of a mobile robot. Among the vast array of optimization approaches, we focus in this paper on Ant Colony Optimization (ACO and Genetic Algorithms (GA for solving the global path planning problem in a static environment, considering their effectiveness in solving such a problem. Our objective is to design an efficient hybrid algorithm that takes profit of the advantages of both ACO and GA approaches for the sake of maximizing the chance to find the optimal path even under real-time constraints. In this paper, we present smartPATH, a new hybrid ACO-GA algorithm that relies on the combination of an improved ACO algorithm (IACO for efficient and fast path selection, and a modified crossover operator to reduce the risk of falling into a local minimum. We demonstrate through extensive simulations that smartPATH outperforms classical ACO (CACO, GA algorithms. It also outperforms the Dijkstra exact method in solving the path planning problem for large graph environments. It improves the solution quality up to 57% in comparison with CACO and reduces the execution time up to 83% as compared to Dijkstra for large and dense graphs. In addition, the experimental results on a real robot shows that smartPATH finds the optimal path with a probability up to 80% with a small gap not exceeding 1m in 98%.

  19. Sedação com sufentanil e clonidina em pacientes submetidos a cateterismo cardíaco

    Anita Perpetua Carvalho Rocha

    2011-03-01

    Full Text Available FUNDAMENTO: A sedação para a realização de cateterismo cardíaco tem sido alvo de preocupação. Benzodiazepínicos, agonistas alfa-2 adrenérgicos e opioides são utilizados para esse fim, entretanto, cada um destes medicamentos possui vantagens e desvantagens. OBJETIVO: Avaliar a eficácia do sufentanil e da clonidina como sedativos em pacientes submetidos a cateterismo cardíaco, observando o impacto dos mesmos sobre os parâmetros hemodinâmicos e respiratórios, a presença de efeitos colaterais, além da satisfação do paciente e do hemodinamicista com o exame. MÉTODOS: Trata-se de um ensaio clínico prospectivo, duplo-cego, randomizado e controlado, que envolveu 60 pacientes que receberam 0,1 µg/kg de sufentanil ou 0,5 µg/kg de clonidina antes da realização do cateterismo cardíaco. O escore de sedação segundo a escala de Ramsay, a necessidade de utilização de midazolam, os efeitos colaterais, os parâmetros hemodinâmicos e respiratórios foram registrados, sendo os dados analisados em 06 diferentes momentos. RESULTADOS: O comportamento da pressão arterial, da frequência cardíaca e da frequência respiratória foi semelhante nos dois grupos, entretanto, no momento 2, os pacientes do grupo sufentanil (Grupo S apresentaram menor escore de sedação segundo a escala de Ramsay, e a saturação periférica da oxihemoglobina foi menor que o grupo clonidina (Grupo C no momento 6. Os pacientes do Grupo S apresentaram maior incidência de náusea e vômito pós-operatório que os pacientes do Grupo C. A satisfação dos pacientes foi maior no grupo clonidina. Os hemodinamicistas mostraram-se satisfeitos nos dois grupos. CONCLUSÃO: O sufentanil e a clonidina foram efetivos como sedativos em pacientes submetidos a cateterismo cardíaco.

  20. Acute Care of At-Risk Newborns (ACoRN): quantitative and qualitative educational evaluation of the program in a region of China

    Singhal Nalini; Lockyer Jocelyn; Fidler Herta; Aziz Khalid; McMillan Douglas; Qiu Xiangming; Ma Xiaolu; Du Lizhong; Lee Shoo K

    2012-01-01

    Abstract Background The Acute Care of at-Risk Newborns (ACoRN) program was developed in Canada for trained health care providers for the identification and management of newborns who are at-risk and/or become unwell in the first few hours or days after birth. The ACoRN process follows an 8-step framework that enables the evaluation and management of babies irrespective of the experience or expertise of the caregiving individual or team. This study assesses the applicability of the program to ...

  1. Influencia de los regímenes de lubricación en la vida de la herramienta y el acabado superficial del fresado de aceros endurecidos AISI D2 y AISI D6

    Maritza Mariño-Cala; Yanier Sánchez-Hechavarría

    2015-01-01

    Se realizó un análisis de la calidad superficial y la vida de la herramienta durante el mecanizado con altas velocidades de los aceros endurecidos AISI D2 y AISI D6, en dos regímenes de lubricación. Los ensayos fueron realizados en un centro de mecanizado MORI SEIKI SV 40 y se emplearon herramientas intercambiables de metal duro recubiertas. La evaluación de la calidad superficial se realizó mediante el monitoreo off-line de la rugosidad superficial media Ra en el sentido del avance y perpend...

  2. TIG AISI-316 welds using an inert gas welding chamber and different filler metals: Changes in mechanical properties and microstructure

    Pascual, M.; Salas, F.; Carcel, F.J.; Perales, M.; Sanchez, A.

    2010-07-01

    This report analyses the influence of the use of an inert gas welding chamber with a totally inert atmosphere on the microstructure and mechanical properties of austenitic AISI 316L stainless steel TIG welds, using AISI ER316L, AISI 308L and Inconel 625 as filler metals. When compared with the typical TIG process, the use of the inert gas chamber induced changes in the microstructure, mainly an increase in the presence of vermicular ferrite and ferrite stringers, what resulted in higher yield strengths and lower values of hardness. Its effect on other characteristics of the joins, such as tensile strength, depended on the filler metal. The best combination of mechanical characteristics was obtained when welding in the inert gas chamber using Inconel 625 as filler metal. (Author). 12 refs.

  3. Effect of aging at 700 deg. C on precipitation and toughness of AISI 321 and AISI 347 austenitic stainless steel welds

    A detailed knowledge of changes in microstructures and mechanical behaviour that occur in austenitic stainless steels with or without Nb/Ti-stabilized weld during heat treatment is of great interest, since the ductility and toughness of the material may change drastically after long aging times. Two kinds of materials, i.e. AISI 321 base and without Ti-stabilized weld steel and AISI 347 base with Nb-stabilized weld steel, were compared during aging at 700 deg. C up to 6000 h. Both materials present increased amount of precipitate and decreased impact energy as the aging time increases. The decreased extent of impact energy with aging is almost the same for both base materials. However, it presents differences for 347 and 321 weld samples. The latter shows a more drastic decrease of impact energy than the former due to the different amount of precipitates. 321 weld sample precipitates more numerously than 347 weld sample due to the absence of stabilized Ti/Nb on the former. Large amount of carbides is formed on 321 weld sample immediately after welding. The carbides are transformed to sigma phase, which is mainly responsible for the much more sigma phase precipitation compared with other samples, after high-temperature aging. The fractographs showed, in general, brittle fracture mode in 321 weld impact-fractured specimens after aging at 700 deg. C for 6000 h. However, other samples show ductile fracture mode in general. Several approaches should be employed to control sigma phase precipitation in weld material. These approaches include: decreasing content of ferrite and M23C6 carbide in weld and selecting Nb added weld wire during welding

  4. Numerical-experimental analysis of a rin AISI{sub 7}Mg Alloy; Analisis numerico experimental de un rin de aleacion AISi{sub 7}Mg

    Sauceda Mesa, Israel; Mata Lucero, Omar; Tirado Delgado, Luis; Ocampo Diaz, Juan de Dios [Universidad Autonoma de Baja California, Mexicali, Baja California (Mexico)

    2005-10-15

    The present work shows the results obtained from an investigation mode on the behaviour of a rin of alloy AISi{sub 7}Mg, which is used in compact Volkswagen's cars. Due to two kind of analysis were realized, firstly an experimental and numerical analysis was done, using a special machine for test the flexionante torque and material fatigue, besides was used an equipment of laser to scanner zone with strength concentrations and the maximum displacement amplitudes. The second analysis was done with the finite element technique, using the software ANSYS and CATIA. The difference between life fatigue cycles obtained from the two analyses was 0.6%. While the time optimize by MEF, was of 85% less than experimental analysis. [Spanish] En el presente trabajo se hicieron investigaciones del comportamiento de un rin de aleacion AISi{sub 7}Mg, el cual es usado en automoviles compactos de volkswagen (VW). Para esto, se realizo analisis experimental y numerico. En el primero se utilizo una maquina para prueba de fatiga de momento flexionante, un equipo de medicion de laser escaner donde se detectaron las zonas de concentraciones de esfuerzos y la maxima amplitud de desplazamiento en el rin. Mientras que en el segundo se obtuvieron los esfuerzos que ocasionaban la fatiga por el elemento finito, utilizando los paquetes de computo Ansys y Catia. La diferencia de los ciclos de vida de fatiga obtenidos entre ambos analisis fue del 0.6%. Mientras que el tiempo que se optimizo por el MEF, fue de un 85% menos que el analisis experimental.

  5. Manejo de las dislipidemias en pacientes cardíacos trasplantados. Hallazgos sobre nuevos factores de riesgo

    Walter Masson

    2008-01-01

    Full Text Available En pacientes cardíacos trasplantados, el desarrollo de enfermedad vascular coronaria es una complicación frecuente y la dislipidemia es uno de los predictores más importantes. Los inmunosupresores predisponen a las dislipidemias y dificultan la utilización de hipolipemiantes. En este grupo particular de pacientes se recomienda alcanzar las metas terapéuticas de prevención secundaria. Las estatinas son los hipolipemiantes de elección. No existen recomendaciones claras sobre nuevos factores de riesgo, como la homocisteína y la lipoproteína (a [Lp(a].Con el objetivo de conocer el perfil lipídico, la prevalencia de homocisteinemia y de Lp(a elevadas, el cumplimiento de las metas terapéuticas y la tolerancia a la medicación, se incluyeron en el estudio 23 pacientes cardíacos trasplantados. Los resultados mostraron que el cumplimiento de las metas lipídicas fue aceptable y que el 65% recibía tratamiento hipolipemiante. El uso de estatinas fue seguro. Se encontró una prevalencia alta de homocisteína y Lp(a elevadas. Su implicación en la modificación del tratamiento se desconoce.

  6. Transient absorption spectroscopy in biology using the Super-ACO storage ring FEL and the synchrotron radiation combination

    Renault, E; De Ninno, G; Garzella, D; Hirsch, M; Nahon, L; Nutarelli, D

    2001-01-01

    The Super-ACO storage ring FEL, covering the UV range down to 300 nm with a high average power (300 mW at 350 nm) together with a high stability and long lifetime, is a unique tool for the performance of users applications. We present here the first pump-probe two color experiments on biological species using a storage ring FEL coupled to the synchrotron radiation. The intense UV pulse of the Super-ACO FEL is used to prepare a high initial concentration of chromophores in their first singlet electronic excited state. The nearby bending magnet synchrotron radiation provides, on the other hand a pulsed, white light continuum (UV-IR), naturally synchronized with the FEL pulses and used to probe the photochemical subsequent events and the associated transient species. We have demonstrated the feasibility with a dye molecule (POPOP) observing a two-color effect, signature of excited state absorption and a temporal signature with Acridine. Applications on various chromophores of biological interest are carried out,...

  7. Interacciones entre dispositivos cardíacos implantables y modalidades fisioterapéuticas: ¿Mito o realidad?

    Genevieve C. Digby

    2011-04-01

    Full Text Available La fisioterapia se ha transformado en una especialidad que claramente incide en la calidad de vida de nuestros pacientes. En poblaciones añosas, el uso de fisioterapia incluye múltiples modalidades para un alto número de distintas enfermedades. Varios informes sobre posibles interacciones negativas entre las distintas modalidades de fisioterapia y los dispositivos cardíacos implantables (marcapasos y cardiodesfibriladores han sido publicados en los últimos aňos. A pesar de ello, existe muy poca evidencia y guías precisas para identificar cuáles son las modalidades de fisioterapia seguras a utilizar en esta población de pacientes. En la siguiente revisión, nos propusimos resumir las interacciones documentadas entre fisioterapia y dispositivos cardíacos implantables (DCI, discutir el estándar actual de estas prácticas e identificar las principales consideraciones que existen desde la perspectiva de un servicio de electrofisiología cardíaca, para el tratamiento adecuado en estos pacientes. Finalmente, abogamos por fortalecer la colaboración entre fisioterapeutas y electrofisiólogos, con el fin de asegurar una óptima y segura atención de este grupo de pacientes.

  8. A Web-Based Egg-Quality Expert Advisory System using Rule Based and Ant Colony (ACO Optimization Algorithms

    J. Anitha

    2010-10-01

    Full Text Available This paper deals with the development of Web based online expert systems using Evolutionary Algorithms. An expert system is a computer application that performs a task that would otherwise be performed by a human expert. Here one of the evolutionary algorithms (ACO Algorithm is considered to find a good match of symptoms in the database. In the present paper, Ant Colony Optimization1 (ACO algorithm has been taken as the base and the concept of optimization is included, so that the new algorithm mainly focuses on the determination of the quality of eggs in the poultry farms. At first, the symptoms provided by the user are processed by a rule based expert system for identifying the quality of the eggs. If the rules required for processing the data by the above are not present in the database, then the system automatically calls the machine learning algorithm technique. As a whole, the system results good optimized solution for recognizing the quality and viruses if any affected to eggs in poultry farms. And corresponding treatments to the viruses may also be suggested to the users. This expert system is designed with JSP as front end and MySQL as backend.

  9. Imunocitomonitorização em pacientes transplantados cardíacos Immunocytomonitorization in patients submitted to cardiac transplantation

    Ricardo Manrique

    1990-04-01

    Full Text Available A técnica de Imunocitomonitorização (CIM - Cytologrcal and Immunologic Monitoring, fundamenta-se na avaliação de mudanças nas subpopulações de linfócitos e seus precursores celulares, durante o processo rejeição aguda. O método avalia a ativação precoce pela contagem do número de: linfócitos ativados, linfoblastos e prolinfócitos (aqui chamados em conjunto de linfócitos ativos, quando esses se apresentam acima do limite superior normal. Utilizamos essa técnica para seguimento e controle da atividade da imunologia celular em 9 pacientes transplantados cardíacos. Também foram submetidos ao CIM para verificar a faixa de normalidade de ativação linfocítica 20 voluntários normais e cinco pacientes candidatos ao transplante cardíaco. Ambos os grupos não tinham antecedentes de quadro de infecção ou alteração imunológica. Para obtenção do controle positivo, testamos 10 pacientes com infecção bacteriana ou virai, previamente diagnosticados por exames bacterianos e/ou sorológicos. Foram observados valores de 1,8% de linfócitos ativos nos indivíduos normais e 3,2% nos candidatos ao transplante cardíaco. Dos 63 testes realizados nos transplantados cardíacos, quatro deles se mostraram positivos, onde três desses tratavam-se de casos de infecção e um confirmado como processo de rejeição aguda em evolução. O tempo médio necessário para a realização da CIM foi de aproximadamente duas horas. A técnica utiliza mostrou-se valiosa no reconhecimento imunológico dos pacientes transplantados cardíacos, pela sua sensibilidade diagnostica, baixo custo e rapidez.The immunocytomonitorization technique (CIM - Cytological and Immunologic Monitoring is based on assessment of changes in the subpopulations of lyphocyte and their precursor cells, while under the acute rejection. The method assesses the precocious activation by counting the number of the lymphocytes normal and actives, lymphoblasts and prolymphocytes (here

  10. TIG AISI-316 welds using an inert gas welding chamber and different filler metals: Changes in mechanical properties and microstructure

    Sánchez, A.

    2010-12-01

    Full Text Available This report analyses the influence of the use of an inert gas welding chamber with a totally inert atmosphere on the microstructure and mechanical properties of austenitic AISI 316L stainless steel TIG welds, using AISI ER316L, AISI 308L and Inconel 625 as filler metals. When compared with the typical TIG process, the use of the inert gas chamber induced changes in the microstructure, mainly an increase in the presence of vermicular ferrite and ferrite stringers, what resulted in higher yield strengths and lower values of hardness. Its effect on other characteristics of the joins, such as tensile strength, depended on the filler metal. The best combination of mechanical characteristics was obtained when welding in the inert gas chamber using Inconel 625 as filler metal.

    En este estudio se analiza la influencia que el uso de una cámara de soldadura de gas inerte tiene sobre la microestructura y las propiedades mecánicas de las soldaduras TIG en el acero inoxidable austenítico AISI-316L cuando se emplean AISI ER316L, AISI 308L e Inconel 625 como materiales de aporte. Cuando se compara con el típico proceso de TIG, el uso de una cámara de gas inerte induce cambios en la microestructura, incrementando la presencia de ferrita vermicular y de laminillas de ferrita, resultando en un aumento del límite elástico y una pérdida de dureza. Su influencia sobre otras características de las soldaduras como la carga de rotura depende de la composición del material de aporte. La mejor combinación de propiedades mecánicas se obtuvo usando el Inconel 625 como material de aporte y soldando en la cámara de gas inerte.

  11. Creep behaviour and microstructural evolution in AISI 316LN + Nb steels at 650 deg. C

    Research highlights: → We studied the effect of Nb additions to AISI 316LN steels on creep and microstructure at 650 deg. C. → Nb additions resulted in a reduction of secondary creep rate and shortening of the tertiary stage. → Two nitrogen rich minor phases were present in the niobium-bearing casts: Z-phase and M6X. → The dimensional stability of Z-phase during creep at 650 deg. C was much better than that of M6X. → Nb accelerated σ-phase and η-Laves formation and this surpassed the positive effect of Z-phase. - Abstract: The paper deals with the effect of niobium in the wrought AISI 316LN steels on the long-term creep characteristics at 650 deg. C. Casts B and C contained 0.1 and 0.3 wt.%Nb, respectively. As a reference material the niobium free Cast A was used. Small additions of niobium to the AISI 316LN steel resulted in a significant reduction of the minimum creep rate and shortening of the tertiary creep stage. At time to rupture exceeding 104 h the creep rupture strength of the niobium-bearing Casts B and C was slightly inferior to the Cast A. Two nitrides formed in the Casts B and C: Z-phase and M6X. The minimum creep rate in niobium-bearing casts was favourably affected by precipitation of the Z-phase. The dimensional stability of Z-phase particles was very high, but niobium additions also accelerated the formation and coarsening of η-Laves and σ-phase. Coarse σ-phase particles at grain boundaries contributed significantly to the shortening of the tertiary creep stage.

  12. Characterization Of Oxide Layers Produced On The AISI 321 Stainless Steel After Annealing

    Bochnowski W.

    2015-09-01

    Full Text Available In this study, the structure, chemical composition and topography of oxide layers produced on the surface of the AISI 321 austenitic steel in the annealing process were analyzed. Heat treatment was done at 980°C temperature for 1 hour time in different conditions. The annealing was done in a ceramic furnace in oxidation atmosphere and in vacuum furnaces with cylindrical molybdenum and graphite chambers. The analysis was carried out using the following methods: a scanning electron microscope (SEM equipped with an energy-dispersive X-ray spectrometer (EDX, a transmission electron microscope (TEM equipped with an energy-dispersive X-ray spectrometer (EDX, an X-ray diffractometer (XRD, a secondary ion mass spectrometer with time-of-flight mass analyzer (TOF SIMS and an atomic force microscope (AFM. The oxide layer formed during annealing of the AISI 321 steel at 980°C consisted of sub-layers, diversified in the chemical composition. The thickness of the oxidized layer is depended on the annealing conditions. In a ceramic furnace in oxidation atmosphere, the thickness of the oxide layer was of 300-500 nm, in a vacuum furnace with molybdenum and graphite heating chambers, it ranged from 40 to 300 nm and from a few to 50 nm, respectively. TOF SIMS method allows to get average (for the surface of 100 μm × 100 μm depth profiles of concentration of particular elements and elements combined with oxygen. In oxide layers formed in vacuum furnaces there are no iron oxides. Titanium, apart from being bounded with carbon in carbides, is a component of the oxide layer formed on the surface of the AISI 321 steel.

  13. Compatibility studies of AISI type 316 stainless steel with lead-lithium eutectic alloy

    Spent fuel subassemblies from the Fast Breeder Test Reactor (FBTR) are to be stored in leak tight cotainers until they are required to be sent for reprocessing. Use of advanced fuels like uranium carbides and plutonium carbides, which are known to be highly chemically active with oxygen and moisture demands adequate leak tightness during long term storage to avoid undesirable chemical reactions. Use of low melting alloys which acts as liquid/solid sealants in the storage containers in which fuel subassemblies are to be kept is being considered for this purpose. Lead-lithium (0.7 wt % lithium) eutectic alloy was chosen as one of the candidate alloys for the purpose on the basis of theoretical assessments. The candidate sealing alloy should have good compatibility with the structural materials of fuel subassemblies as well as the fuel and fission products. AISI type 316 stainless steel in solution annealed, ten and twenty percent cold worked condition is the clad and wrapper material used for the fabrication of fuel pins and subassemblies. Compatibility studies between eutectic Pb-Li alloy and AISI type 316 stainless steel material in the above conditions were undertaken at different temperatures and time durations. The studies indicate that the tensile properties of AISI type 316 stainless steel are not subject to any serious jeopardisation through contact with this molten Pb-Li eutectic alloy for periods extending even upto 7000 hours at 873 K. Thus use of Pb-Li eutectic alloy would be suitable for the storage of irradiated fuel. (author). 16 refs., 38 figs., 3 tabs

  14. Elastic-plastic fracture toughness characteristics of irradiated AISI 316 H stainless steel

    The objective of this research is the FM assessment of neutron damage to AISI 316 H steel commonly used in LMFBR's permanent primary circuit components. The material FM characteristics studied are the crack-initiation toughness and the crack-resistance curves. The AISI 316 H stainless steel has been considered in the base condition, the welded deposit and the HAZ material. The specimens tested are 3PB bars. The results presented cover the 0, 0.1 dpa and 0.3 dpa fluences at 350 deg. C and 550 deg. C. The crack-growth-resistance curves were obtained following the dimensional analysis approach together with the deformation theory of plasticity concepts. This method, using key curves has effectively shown trends in the above-mentioned fracture mechanics characteristics of the irradiated AISI 316 H steel. The results obtained so far indicate generally low degradation at both temperatures between the non-irradiated and the irradiated base material, one note-worthy exception being the significant lowering at 550 deg. C and 0.1 dpa of sup(dJ)/da by about 35% and of sup(J)Ic by about 50% with respect to those parameters values in the other conditions of fluences and temperatures. As far as the weld material is concerned, it exhibits significantly lower initiation toughness and tearing moduli in the pre and post irradiation conditions with respect to the base material but those FM parameters values are practically unaltered at both temperatures and all fluence levels. The HAZ material was studied too and it was found that all J values corresponding to various crack advances fell within the base material results at 350 deg. C as upper bound and the welded material at 550 deg. C as lower bound at corresponding fluence levels. (author)

  15. CRYOGENIC AND STRESS RELIEF THERMAL TREATMENTS IN AN AISI D2 STEEL

    Paula Fernanda da Silva Farina; Alexandre Bellegard Farina; Celso Antonio Barbosa; Helio Goldenstein

    2012-01-01

    The effects of cryogenic treatments on an AISI D2 cold work tool steel using X-ray diffraction from syncronton radiation are studied. The aim of this work is to verify the effects of: i) time at cryogenic temperatures (3, 10 and 30 hours); ii) cryogenic temperatures (–80°C and –196°C); iii) stress relief heat treatment (130°C) before cryogenic treatments; iv) effect of double tempering at 520°C for 2 hours each time, after cryogenic treatment at –196°C for 30 hours, with and witho...

  16. Effects of ageing on the ductile fracture of AISI type 316 stainless steel

    The micromechanisms of ductile fracture have been studied in a commercial AISI type 316 austenitic stainless steel. Tensile, Charpy impact and ductile fracture toughness testing has been performed on unaged material and samples aged at 7000C for times up to 4380 h. Examination of the specimens after testing has demonstrated that the microstructural changes occurring at grain boundaries are reponsible for the observed losses of ductility and crack growth resistance. The relative magnitude of the observed changes in mechanical properties has been accounted for using a simple model to describe the ductile fracture process. (author)

  17. 1020 AISI-SAE steel Austenitic Nitrocarburising with alcohol and triethanolamine

    Álvaro Castro P

    2010-04-01

    Full Text Available The present work shows AISI-SAE 1020 steel's nitrocarbide layer's microstructure and micro-hardness profile following 4 hours at 700ºC using methanol, isopropanol and triethanolamine. The steel was then hardened by quenching it in water and then tempered at 350ºC for 1 hour. Its surface had been partially oxidised by heating it at 400ºC for 1 hour. An example is given of other researchers analysing microstructure and propierties in steel having 0,5% C, using endothermic gas and different amounts of ammoniac.

  18. Thermo-mechanical and isothermal fatigue behavior of austenitic stainless steel AISI 316L

    Škorík, Viktor; Šulák, Ivo; Obrtlík, Karel; Polák, Jaroslav

    Ostrava: TANGER Ltd, 2015. ISBN 978-80-87294-58-1. [METAL 2015 - International Conference on Metallurgy and Materials /24./. Brno (CZ), 03.06.2015-05.06.2015] R&D Projects: GA MŠk(CZ) EE2.3.30.0063; GA ČR(CZ) GA15-20991S; GA ČR(CZ) GA13-23652S Institutional support: RVO:68081723 Keywords : Thermo-mechanical fatigue (TMF) * In-phase cycling (IP) * Isothermal fatigue (IF) * AISI 316L * Fatigue life Subject RIV: JL - Materials Fatigue, Friction Mechanics

  19. Study of Carbide Evolution During Thermo-Mechanical Processing of AISI D2 Tool Steel

    Bombac, D.; Fazarinc, M.; Podder, A. Saha; Kugler, G.

    2013-03-01

    The microstructure of a cold-worked tool steel (AISI D2) with various thermo-mechanical treatments was examined in the current study to identify the effects of these treatments on phases. X-ray diffraction was used to identify phases. Microstructural changes such as spheroidization and coarsening of carbides were studied. Thermodynamic calculations were used to verify the results of the differential thermal analysis. It was found that soaking temperature and time have a large influence on dissolution, precipitation, spheroidization, and coalescence of carbides present in the steel. This consequently influences the hot workability and final properties.

  20. Investigation into some tribological properties of plasma nitrided hot-worked tool steel AISI H11

    Yilbas, B.S.; Sahin, A.Z.; Said, S.A.M.; Nickel, J.; Coban, A. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia). Dept. of Mechanical Engineering

    1996-04-01

    Interest in the tribological properties of plasma nitriding has increased substantially over the past years because plasma nitriding provides a high nitride depth and improved hard facing. The present study examines the tribological properties of AISI H11 plasma nitrided, hot-worked steel. Different nitriding temperatures and durations were considered. Characterization of the composite structures was investigated with wear tests, x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and microhardness tests. The depth profile of the nitrided zone was measured using the nuclear reaction analysis (NRA) technique. Plasma nitriding affected the microhardness, wear properties, and morphology considerably. Increase in process temperature increased the nitride zone depth.

  1. Laser welding of butt joints of austenitic stainless steel AISI 321

    A. Klimpel; A. Lisiecki

    2007-01-01

    Purpose: of this paper: A study of an automated laser autogenous welding process of butt joints of austenitic stainless steel AISI 321 sheets 0.5 [mm] and 1.0 [mm] thick using a high power diode laser HPDL has been carried out.Design/methodology/approach: Influence of basic parameters of laser welding on shape and quality of the butt joints and the range of optimal parameters of welding were determined.Findings: It was showed that there is a wide range of laser autogenous welding parameters w...

  2. Microstructural Evolution and Wear Resistance of Friction Stir-Processed AISI 52100 Steel

    Seraj, R. A.; Abdollah-zadeh, A.; Hajian, M.; Kargar, F.; Soltanalizadeh, R.

    2016-07-01

    Friction stir processing (FSP) was successfully applied on AISI 52100 steel. The influence of process parameters on the microstructure and mechanical properties of the material was evaluated. It was observed that the initial ferritic-pearlitic microstructure of the base metal is transformed to the martensitic microstructure with retained austenite in the stir zone. The results also showed that microhardness and wear resistance of the FSP samples are, respectively, at least 2 and 15 times higher than those of the base metal. The improvement of the mechanical properties of FSP samples was attributed to their microstructural characteristics. The mechanisms controlling the wear behavior of the base metal and FSP samples were also discussed.

  3. The structural characterization of some biomaterials, type AISI 310, used in medicine

    Minciuna, M. G.; Vizureanu, P.; Hanganu, C.; Achitei, D. C.; Popescu, D. C.; Focsaneanu, S. C.

    2016-06-01

    Orthopedics biomaterials are intended for implantation in the human body and substituted or help to repair of bones, cartilage or organ transplant, and tendons. At the end of the 20th century, the availability of materials for the manufacture implants used in medicine has been the same as for other industrial applications. The most used metals for manufacturing the orthopedics implants are: stainless steels, cobalt-chrome-molybdenum alloys, titanium and his alloys. The structural researches which are made in this paper, offer a complete analysis of AISI310 stainless steels, using: optical spectrometry, X-ray diffraction and scanning electronic microscopy.

  4. Microstructure and corrosion behaviour of pulsed plasma-nitrided AISI H13 tool steel

    Basso, Rodrigo L.O. [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS (Brazil); Pastore, Heloise O. [Instituto de Quimica, Universidade Estadual de Campinas, 13084-862 Campinas, SP (Brazil); Schmidt, Vanessa [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS (Brazil); Baumvol, Israel J.R. [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS (Brazil); Instituto de Fisica, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, RS (Brazil); Abarca, Silvia A.C.; Souza, Fernando S. de; Spinelli, Almir [Departamento de Quimica, Universidade Federal de Santa Catarina, 88040-900 Florianopolis, SC (Brazil); Figueroa, Carlos A. [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS (Brazil); Giacomelli, Cristiano, E-mail: cgiacomelli@pq.cnpq.b [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, 95070-560 Caxias do Sul, RS (Brazil)

    2010-09-15

    The effect of pulsed plasma nitriding temperature and time on the pitting corrosion behaviour of AISI H13 tool steel in 0.9% NaCl solutions was investigated by cyclic polarization. The pitting potential (E{sub pit}) was found to be dependent on the composition, microstructure and morphology of the surface layers, whose properties were determined by X-ray diffraction and scanning electron microscopy techniques. The best corrosion protection was observed for samples nitrided at 480 {sup o}C and 520 {sup o}C. Under such experimental conditions the E{sub pit}-values shifted up to 1.25 V in the positive direction.

  5. Microstructure and corrosion behaviour of pulsed plasma-nitrided AISI H13 tool steel

    The effect of pulsed plasma nitriding temperature and time on the pitting corrosion behaviour of AISI H13 tool steel in 0.9% NaCl solutions was investigated by cyclic polarization. The pitting potential (Epit) was found to be dependent on the composition, microstructure and morphology of the surface layers, whose properties were determined by X-ray diffraction and scanning electron microscopy techniques. The best corrosion protection was observed for samples nitrided at 480 oC and 520 oC. Under such experimental conditions the Epit-values shifted up to 1.25 V in the positive direction.

  6. Anodic behaviour of the stainless steel AISI 430 in aqueous solutions of chloride and sulphate ions

    The kinetics of the dissolution of stainless steel AISI 430 in the presence of chloride and sulphate ions has been studied in terms of the ion concentration, the pH variation, and the velocity of the working electrode. The experimental method utilized was the potentiostatic anodic polarization, and the reactants used were NaCl and Na2 SO4 at room temperature. Atomic Absorption spectrophotometry and Auger Electrons spectroscopy (AES) analyses were made in order to support the interpretation of results obtained by means of the potentiostatic polarization method. (author)

  7. XPS Analysis of AISI 304L Stainless Steel Surface after Electropolishing

    Rokosz K.

    2015-03-01

    Full Text Available In the paper, the passive surface layers of AISI 304L after standard (EP50 and very-high-current density electropolishing (EP1000 in a mixture of orthophosphoric and sulfuric acids in a 1:4 ratio, are presented. The main finding of the presented studies is enrichment of the steel surface film in chromium: total chromium to total iron ratio was equal to 6.6 after EP50 and to 2.8 after EP1000; on the other hand, chromium compounds to iron compounds ratio was equal to 10.1 after EP50, and 3.9 after EP1000.

  8. Effects of the stress reduction tests in the creep of AISI-316 austenitic stainless steel

    Stress Reduction Tests were performed at the temperature of 1006 K (7330C) in AISI-316 stainless steel and the evolution of the microstructure was followed. After the stress reduction a rapid decrease in the dislocation density, a continuous increase in the average carbide size and a decrease in the mean particle spacing are observed. No change in the subgrain size occurs after the stress reduction. An increase in the creep resistance is observed after the stress reductions and is interpreted based on the microstructural modifications. (Author)

  9. Wear Properties of TiN Coating Formed on AISI D2 Surface

    ÇEĞİL, Özkan; KILINÇ, Bülent; Şen, Şaduman

    2014-01-01

    In this work, the wear test of uncoated and titanium nitride coated AISI D2 cold work tool steel against silicon nitride ball was realized at 0.3 m/s sliding speed and under the loads of 2.5N, 5N and 10N. Steel samples were nitrided at 575°C for 8 h in the first step of the coating process, and then titanium nitride coating was performed by pack diffusion coating in a powder mixture consisting of ferro-titanium, ammonium chloride and alumina at 1000°C for 2h. Nitro-titanized samples were char...

  10. Effect of Welding Current on Energy Absorption of AISI 304 Resistance Spot Welds

    M. Pouranvari

    2012-08-01

    Full Text Available In this study, the effect of welding current on the energy absorption capability of austenitic stainless steel AISI304 resistance spot welds during the quasi-static tensile-shear test is investigated. Results showed that there is a direct relationship between the fusion zone size and failure energy in expulsion free samples. However, when expulsion occurred, the energy absorption capability reduced significantly. Failure energy for samples experiencing expulsion is lower compared to expulsion free samples with identical or even smaller weld nugget size.

  11. Estimation of embrittlement during aging of AISI 316 stainless steel TIG welds

    J Nayak; K R Udupa; K R Hebbar; H V S Nayak

    2004-12-01

    Weldments of AISI grade 316 stainless steel, having a ferrite content of 4–6% and a variety of nitrogen concentrations were prepared using a modified element implant technique. Charpy impact specimens prepared from these weldments were subjected to a variety of aging treatments. Impact toughness decreases with aging time at all aging temperatures. Nitrogen is found to be beneficial to toughness. An empirical relation connecting the aging temperature, aging time and nitrogen content with toughness has been developed which can be used to estimate the time for embrittlement.

  12. Estudio de las fuerzas de corte en el fresado de AISI 316

    González López, Diego

    2015-01-01

    Este trabajo trata sobre el comportamiento que tiene un acero AISI 316-L ASS al ser fresado mediante dos tipos de procedimiento: fresado en concordancia y fresado en oposición. Para realizar este estudio se ha instalado un dinamómetro Kistler en la herramienta, con el objetivo de medir las fuerzas de corte que intervienen en el mecanizado.Estas fuerzas se procesan con el sistema de adquisición de datos " WaveBook-512" y se analizan posteriormente con el software " Dasylab 8.0", un sistema d...

  13. The influence of sulphate-reducing bacteria biofilm on the corrosion of stainless steel AISI 316

    This work investigates microbially-influenced corrosion (MIC) of stainless steel AISI 316 by two sulphate-reducing bacteria, Desulfovibrio desulfuricans and a local marine isolate. The biofilm and pit morphology that developed with time were analyzed using atomic force microscopy (AFM). Electrochemical impedance spectroscopy (EIS) results were interpreted with an equivalent circuit to model the physicoelectric characteristics of the electrode/biofilm/solution interface. D. desulfuricans formed one biofilm layer on the metal surface, while the marine isolate formed two layers: a biofilm layer and a ferrous sulfide deposit layer. AFM images corroborated results from the EIS modeling which showed biofilm attachment and subsequent detachment over time

  14. Microstructural changes due to laser surface melting of an AISI 304 stainless steel

    d?Oliveira A.S.C.M.

    2001-01-01

    Full Text Available Several techniques can be used to improve surface properties. These can involve changes on the surface chemical composition (such as alloying and surface welding processes or on the surface microstructure, such as hardening and melting. In the present work surface melting with a 3kW CO2 cw laser was done to alter surface features of an AISI 304 stainless steel. Microstructure characterisation was done by optical and scanning electron microscopy. Vickers and Knoop microhardness tests evaluated mechanical features after surface melting. Phase transformation during rapid solidification is analysed and discussed.

  15. Effect of Niobium on Microstructure of Cast AISI H13 Hot Work Tool Steel

    Shahram Kheirandish; Ahmad Noorian

    2008-01-01

    The effect of niobium addition on the microstructure of cast AISI H13 hot work tool steel was evaluated by using EDX analyzer attached to the scanning electron microscope.The volume percent of eutectic area and eutectic cell size and also volume percent of different carbides of new steel,which is heat treated under different conditions,are also determined.The results show that the a niobium addition modifies the cast structure of Nb-alloyed hot work tool steel,and reduces the size and volume of eutectic cells,and increases the maximum hardness of the steel.

  16. Comparative study of the microbiological corrosion among an AISI 304L and an API X65

    Metallic samples of AISI 304L sensitized and API X65, were subjected to the action of an inoculated media with reductive sulphate microorganisms (SBR), carrying out electrochemical evaluations by means of the techniques of Polarization Resistance (RP), Tafel extrapolation (ET) and Electrochemical Noise (RE). The generated information was complemented with the analysis and diagnostic of the present damage in the surfaces exposed in both metals. The used electrochemical techniques allow to determine the corrosion velocities associated to each system, establishing that the uniform corrosion is not affected by the effect of the microorganisms; however, electrochemical noise, evidenced the formation of stings associated to the presence of bacteria. (Author)

  17. Microstructural Evolution and Wear Resistance of Friction Stir-Processed AISI 52100 Steel

    Seraj, R. A.; Abdollah-zadeh, A.; Hajian, M.; Kargar, F.; Soltanalizadeh, R.

    2016-04-01

    Friction stir processing (FSP) was successfully applied on AISI 52100 steel. The influence of process parameters on the microstructure and mechanical properties of the material was evaluated. It was observed that the initial ferritic-pearlitic microstructure of the base metal is transformed to the martensitic microstructure with retained austenite in the stir zone. The results also showed that microhardness and wear resistance of the FSP samples are, respectively, at least 2 and 15 times higher than those of the base metal. The improvement of the mechanical properties of FSP samples was attributed to their microstructural characteristics. The mechanisms controlling the wear behavior of the base metal and FSP samples were also discussed.

  18. Aspects of plasma arc cutting process in the AISI 321 type stainless steel

    Some aspects of plasma arc cutting process in the AISI321 stainless steel, used in nuclear industry, are analysed. The maximum values of the velocity of cutting and, the minimum quantity of energy per unit of length necesary for the plasma were determined. The localization of irregularities in the cut surface in function of the velocity of cutting was investigated. The cut surfaces were evaluated by surface roughness, using as measurement parameter, the distance between the sharpest salience and the deepest reentrance of the sample profile. The width of layer from thermal action of the plasma was influenced by the velocity of cutting. (Author)

  19. Fatigue of welded joint in a stainless steel AISI 304 L

    The flexion fatigue behavior for the base metal and welded joint of an AISI 304 L stainless steel type, used in the Angra-1 reactor, was determined. An automatic welding process was used with improved procedures in order to assure better welding metallurgy. Fatigue tests samples reinforcements were done to allow the evaluation of metallurgical variables, specially the role played by delta ferrite. The resulting welded joint showed better fatigue life than the base metal. Delta ferrite was found to play an important role on the initiation and propagation processes of the fatigue cracks. (Author)

  20. Microstructural origins of yield strength changes in AISI 316 during fission or fusion irradiation

    The changes in yield strength of AISI 316 irradiated in breeder reactors have been successfully modeled in terms of concurrent changes in microstructural components. Two new insights involving the strength contributions of voids and Frank loops have been incorporated into the hardening models. Both the radiation-induced microstructure and the yield strength exhibit transients which are then followed by saturation at a level dependent on the irradiation temperature. Extrapolation to anticipated fusion behavior based on microstructural comparisons leads to the conclusion that the primary influence of transmutational differences is only to alter the transient behavior and not the saturation level of yield strength

  1. Numerical Simulation on Temperature and Microstructure during Quenching Process of Large-sized AISI P20 Steel Die Blocks

    SONGDong-li; GUJian-feng; ZHANGWei-min; LIUYang; PANJian-sheng

    2004-01-01

    In this paper, a model of coupled thermal and phase transformation is described. The temperature and microstructure during the quenching process for large-sized AISI P20 steel die blocks have been simulated using the finite element method (FEM). The optimum quenching technology of large-sized AISI P20 steel die blocks has been proposed based on the simulation results, which not only can effectively avoid quenching cracks and obtain deeper hardened depth, but also can improve the microstructure and properties of the large-sized die blocks.

  2. Numerical Simulation on Temperature and Microstructure during Quenching Process of Large-sized AISI P20 Steel Die Blocks

    SONG Dong-li; GU Jian-feng; ZHANG Wei-min; LIU Yang; PAN Jian-sheng

    2004-01-01

    In this paper, a model of coupled thermal and phase transformation is described. The temperature and microstructure during the quenching process for large-sized AISI P20 steel die blocks have been simulated using the finite element method (FEM). The optimum quenching technology of large-sized AISI P20 steel die blocks has been proposed based on the simulation results, which not only can effectively avoid quenching cracks and obtain deeper hardened depth,but also can improve the microstructure and properties of the large-sized die blocks.

  3. Optimization of the contact mechanical strength of magnetron-sputtered nitrogen-doped AISI 316L physically vapour deposited coatings

    The reactive magnetron sputtering technique adopted produces perfectly adhering nitrogen-doped AISI 316L coatings on construction and stainless steel substrates (AISI 316L and 4135). Surface mechanical testing was done by indentation and sclerometric, frictional, low cycle fatigue. The major damage parameters adopted were the critical coating cracking loads, track depression and lateral pile-up volumes. It is shown that the detrimental effect of growth defects on coating brittleness can be controlled to some extent by optimizing substrate surface treatment prior to and bias voltage during deposition. (orig.)

  4. Intelligent Search Method Based ACO Techniques for a Multistage Decision Problem EDP/LFP

    Mostefa RAHLI

    2006-07-01

    the algorithm getting to him a rate preferably more or less justifiable. In operational research, this subject is known under the name of CPO [14] (combinatory problem optimization.The choice of a numerical method to use for a merged case study and calculation of the LFP/Fitting/EDP what is [7, 8, 9, 10, 18, 19, 20] (in theoretical form of a problem compensates the final decision to adopt and a strategy of optimal production (which is a practical problem form and the final task most wanted.Each method is imposed by:· The algorithm complexity.· In an application gathering all calculations, the number of uses of method compared to the total number of later issues.· The maximum number of iterations for a given use.· The maximum iterations count allowed for this algorithm kind.· The limitations of the algorithm such as: applicability of a method (algorithm adapted or not to the problem; does the problem constrained or not; problem dimension or order N (N ≤ Nmax; the algorithm stability.It's well-known that for an approached calculation method, the propagation of errors strongly conditions the need of making its adequate choice and if it can be adopted compared to others for the same area.More is the number of the elementary operations is large more the final result misses precision and especially if the finality of the study is a responsible decision to make and a satisfaction of constraints and multiple conditions. Our study proposes an inference based solution (AI with the use of ACO technique (Ant colony Optimization2.

  5. Meta-heurística ACO (Ant Colony Optimization) para la resolución de problemas en líneas de producción

    Bautista Valhondo, Joaquín; Bretón Blas, Javier; Fernández Ros, José Antonio; De la Rosa Herrero, Marcela

    2000-01-01

    La meta-heurística ACO (Ant Colony Optimization) es un procedimiento heurístico para la resolución de problemas de optimización discreta basado en el comportamiento de las hormigas. Sus principales características son: (1) la utilización de

  6. Dynamic strain ageing of deformed nitrogen-alloyed AISI 316 stainless steels

    Intergranular stress corrosion cracking has occurred in BWR environment in non-sensitized, deformed austenitic stainless steel materials. The affecting parameters are so far not fully known, but deformation mechanisms may be decisive. The effect of deformation and nitrogen content on the behaviour of austenitic stainless steels was investigated. The materials were austenitic stainless steels of AISI 316L type with different amounts of nitrogen (0.03 - 0.18%) and they were mechanically deformed 0, 5 and 20%. The investigations are focused on the dynamic strain ageing (DSA) behaviour. A few crack growth rate measurements are performed on nuclear grade AISI 316NG material with different degrees of deformation (0, 5 and 20%). The effects of DSA on mechanical properties of these materials are evaluated based on peaks in ultimate tensile strength and strain hardening coefficient and minimum in ductility in the DSA temperature range. Additionally, internal friction measurements have been performed in the temperature range of -100 to 600 deg. C for determining nitrogen interactions with other alloying elements and dislocations (cold-worked samples). The results show an effect of nitrogen on the stainless steel behaviour, e.g. clear indications of dynamic strain ageing and changes in the internal friction peaks as a function of nitrogen content and amount of deformation. (authors)

  7. Microstructure, Mechanical and Corrosion Properties of Friction Stir-Processed AISI D2 Tool Steel

    Yasavol, Noushin; Jafari, Hassan

    2015-05-01

    In this study, AISI D2 tool steel underwent friction stir processing (FSP). The microstructure, mechanical properties, and corrosion resistance of the FSPed materials were then evaluated. A flat WC-Co tool was used; the rotation rate of the tool varied from 400 to 800 rpm, and the travel speed was maintained constant at 385 mm/s during the process. FSP improved mechanical properties and produced ultrafine-grained surface layers in the tool steel. Mechanical properties improvement is attributed to the homogenous distribution of two types of fine (0.2-0.3 μm) and coarse (1.6 μm) carbides in duplex ferrite-martensite matrix. In addition to the refinement of the carbides, the homogenous dispersion of the particles was found to be more effective in enhancing mechanical properties at 500 rpm tool rotation rate. The improved corrosion resistance was observed and is attributed to the volume fraction of low-angle grain boundaries produced after friction stir process of the AISI D2 steel.

  8. Modeling of the flow stress for AISI H13 Tool Steel during Hard Machining Processes

    In general, the flow stress models used in computer simulation of machining processes are a function of effective strain, effective strain rate and temperature developed during the cutting process. However, these models do not adequately describe the material behavior in hard machining, where a range of material hardness between 45 and 60 HRC are used. Thus, depending on the specific material hardness different material models must be used in modeling the cutting process. This paper describes the development of a hardness-based flow stress and fracture models for the AISI H13 tool steel, which can be applied for range of material hardness mentioned above. These models were implemented in a non-isothermal viscoplastic numerical model to simulate the machining process for AISI H13 with various hardness values and applying different cutting regime parameters. Predicted results are validated by comparing them with experimental results found in the literature. They are found to predict reasonably well the cutting forces as well as the change in chip morphology from continuous to segmented chip as the material hardness change

  9. Modelling of Tool Wear and Residual Stress during Machining of AISI H13 Tool Steel

    Residual stresses can enhance or impair the ability of a component to withstand loading conditions in service (fatigue, creep, stress corrosion cracking, etc.), depending on their nature: compressive or tensile, respectively. This poses enormous problems in structural assembly as this affects the structural integrity of the whole part. In addition, tool wear issues are of critical importance in manufacturing since these affect component quality, tool life and machining cost. Therefore, prediction and control of both tool wear and the residual stresses in machining are absolutely necessary. In this work, a two-dimensional Finite Element model using an implicit Lagrangian formulation with an automatic remeshing was applied to simulate the orthogonal cutting process of AISI H13 tool steel. To validate such model the predicted and experimentally measured chip geometry, cutting forces, temperatures, tool wear and residual stresses on the machined affected layers were compared. The proposed FE model allowed us to investigate the influence of tool geometry, cutting regime parameters and tool wear on residual stress distribution in the machined surface and subsurface of AISI H13 tool steel. The obtained results permit to conclude that in order to reduce the magnitude of surface residual stresses, the cutting speed should be increased, the uncut chip thickness (or feed) should be reduced and machining with honed tools having large cutting edge radii produce better results than chamfered tools. Moreover, increasing tool wear increases the magnitude of surface residual stresses

  10. OPTIMIZATION OF PROCESSING PARAMETERS IN ELECTROCHEMICAL MACHINING OF AISI 202 USING RESPONSE SURFACE METHODOLOGY

    V. SATHIYAMOORTHY

    2015-06-01

    Full Text Available This paper attempts to optimize the predominated machining parameters in Electro Chemical Machining (ECM of AISI 202 Austenitic stainless steel using Response Surface Methodology (RSM. The chosen material has been used in railway rolling stock. The selected influencing parameters are applied voltage, electrolyte discharge rate with three levels and tool feed rate with four levels. Thirty six experiments were conducted through design of experiments and central composite design in RSM was applied to identify the optimum conditions which turn into the best Material Removal Rate (MRR and Surface roughness (SR. The experimental analyses reveal that applied voltage of 16 V, tool feed rate of 0.54 mm/min and electrolyte discharge rate of 10 L/min would be the optimum values in ECM of AISI 202 under the selected conditions. For checking the optimality of the developed equation, MRR of 298.276 mm3/min and surface roughness Ra of 2.05 µm were predicted at applied voltage of 12.5 V, tool feed rate of 0.54 mm/min and electrolyte discharge rate of 11.8 L/min with composite desirability of 98.05%. Confirmatory tests showed that the actual performance at the optimum conditions were 291.351 mm3/min and 2.17 µm. The deviation from the predicted performance is less than 6% which proves the composite desirability of the developed models for MRR and surface roughness.

  11. Improving electrochemical properties of AISI 1045 steels by duplex surface treatment of plasma nitriding and aluminizing

    Highlights: • AlN coating was applied on AISI 1045 steel via plasma nitriding and aluminizing. • Plasma nitriding and post-aluminizing result in AlN single phase layer on the steel. • PN–Al coated steel had better corrosion resistance than Al–PN one. • Formation of oxide layer provided protection of PN–Al coated steel against corrosion. • Pitting and surface defects was the dominant corrosion mechanism in Al–PN coated steel. - Abstract: Improvement in electrochemical behavior of AISI 1045 steel after applying aluminum nitride coating was investigated in 3.5% NaCl solution, using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analyses. Aluminum nitride coating was applied on the steel surface by duplex treatment of pack aluminizing and plasma nitriding. Some specimens were plasma nitrided followed by aluminizing (PN–Al), while the others were pack aluminized followed by plasma nitriding (Al–PN). Topological and structural studies of the modified surfaces were conducted using scanning electron microscope (SEM) equipped by energy dispersive X-ray spectroscope (EDS), and X-ray diffractometer (XRD). The electrochemical measurements showed that the highest corrosion and polarization (Rp) resistances were obtained in PN–Al specimens, having single phase superficial layer of AlN. Pitting mechanism was dominant reason of lower corrosion resistance in the Al–PN specimens

  12. Improving electrochemical properties of AISI 1045 steels by duplex surface treatment of plasma nitriding and aluminizing

    Haftlang, Farahnaz, E-mail: f.haftlang@students.semnan.ac.ir [Department of Metallurgy and Materials Engineering, Faculty of Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Habibolahzadeh, Ali [Department of Metallurgy and Materials Engineering, Faculty of Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Sohi, Mahmoud Heydarzadeh [School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2015-02-28

    Highlights: • AlN coating was applied on AISI 1045 steel via plasma nitriding and aluminizing. • Plasma nitriding and post-aluminizing result in AlN single phase layer on the steel. • PN–Al coated steel had better corrosion resistance than Al–PN one. • Formation of oxide layer provided protection of PN–Al coated steel against corrosion. • Pitting and surface defects was the dominant corrosion mechanism in Al–PN coated steel. - Abstract: Improvement in electrochemical behavior of AISI 1045 steel after applying aluminum nitride coating was investigated in 3.5% NaCl solution, using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analyses. Aluminum nitride coating was applied on the steel surface by duplex treatment of pack aluminizing and plasma nitriding. Some specimens were plasma nitrided followed by aluminizing (PN–Al), while the others were pack aluminized followed by plasma nitriding (Al–PN). Topological and structural studies of the modified surfaces were conducted using scanning electron microscope (SEM) equipped by energy dispersive X-ray spectroscope (EDS), and X-ray diffractometer (XRD). The electrochemical measurements showed that the highest corrosion and polarization (R{sub p}) resistances were obtained in PN–Al specimens, having single phase superficial layer of AlN. Pitting mechanism was dominant reason of lower corrosion resistance in the Al–PN specimens.

  13. Characterization of a nitrurated coat in AISI 420 and SAE 1040 steels with different thermal treatments

    According to the results obtained in tribological tests, they are heavily influenced by the behavior of the tribosurfaces as well as by the substrate of the erosion couple. This work was undertaken in order to better understand these surface layers, by characterizing the layer of ionic nitruration compounds in test pieces of AISI 420 stainless steel with different thermal treatments and under the influence of the alloying elements while they are being formed. Circular test pieces of AISI 420 stainless steel and SAE 1040 steel were used. Samples of both groups were quenched and tempered at 673 K and 943 K. Then they were ionically nitrurated at 25% N2 and 75% H2, for 20 h at a pressure of 0.15 MPa. The qualitative determination of the present phases was carried out by X-ray diffraction (XRD) and with grade line X-ray diffraction. The thicknesses for the nitrurated layers were established by Vickers microhardness variation. The morphology, size, distribution and preferred site of carbide precipitation were analyzed by optic microscopy and scanning electron microscopy (SEM). The results show the influence of the alloying elements and of the prior microstructure, product of the different tempering temperatures, on the morphology of the nitrurated layer (CW)

  14. Improvement in cavitation erosion resistance of AISI 316L stainless steel by friction stir processing

    Commercial AISI 316L plates with the initial grain size of 14.8 μm were friction stir processed (FSP) with different processing parameters, resulting in two fine-grained microstructures with the grain sizes of 4.6 and 1.7 μm. The cavitation erosion behavior, before and after FSP, was evaluated in terms of incubation time, cumulative mass loss and mean depth of erosion. A separate cavitation erosion test was performed on the transverse cross section of a FSP sample to reveal the effect of grain structure. It was observed that FSP samples, depending on their grain size, are at least 3–6 times more resistant than the base material against cavitation erosion. The improvement in cavitation erosion resistance is attributed to smaller grain structure, lower fraction of twin boundaries, and favorable crystallographic orientation of grains in FSP samples. The finer the grain size, the more cavitation erosion resistance was achieved. Moreover, the microstructures of eroded surfaces were studied using a scanning electron microscope equipped with EBSD, and an atomic force microscope. The mechanisms controlling the cavitation erosion damage in friction stir processed AISI 316L are also discussed.

  15. Sintering, microstructure and properties of WC-AISI304 powder composites

    Highlights: ► Total replacement of Co binder by stainless steel AISI 304 in WC based composites. ► Processing conditions for WC–stainless steel composites. ► Mechanical behavior and oxidation resistance of WC–stainless steel composites. -- Abstract: Tungsten carbide–stainless steel (AISI 304) based composites were successfully prepared by powder metallurgy routes using vacuum sintering at a maximum temperature of 1500 °C. The effects of the binder amount (between 6 and 15 wt.%) on the phase composition, microstructure and mechanical properties, namely hardness and fracture toughness, were investigated. Appreciable amount of (M,W)6C up to 12 wt.% was detected, especially for the higher SS contents. However, a good compromise between toughness and hardness was observed. Besides that, improved oxidation resistance was noticed in WC–SS based composites compared with WC–Co composites. The results are discussed having in mind the correlation between chemical composition, phase composition, microstructure and mechanical behavior

  16. Microstructure evolution in nano/submicron grained AISI 301LN stainless steel

    The phase and microstructure evolution of a heavily cold-rolled AISI 301LN stainless steel (SS), before and after annealing is discussed. AISI 301LN SS has been cold-rolled to 63% rolling reduction and subsequently annealed from 600 to 1000 deg. C for short annealing durations (1-100 s). Phase analysis indicates that the cold-rolled sheet comprises almost 100% martensite, while transmission electron microscopy examination reveals its morphology to be of dislocation cell- and heavily deformed lath-type martensite. The martensite → austenite reversion upon annealing at 600 deg. C for 1 and 10 s is negligible, but nanoscale austenite grains are formed in the martensitic matrix. Partial reversion to nano/submicron austenite grains is observed for samples annealed at 600 deg. C for 100 s, and 700 deg. C for 1 s. Samples annealed at higher temperatures exhibit a complete reversion to submicron/nano-austenite grains with a large grain size variation, as well as secondary phase chromium nitride precipitates.

  17. Effects of biofilm formation on the electrochemical behavior of AISI 304 SS in board machine environment

    Carp, L.; Hakkarainen, T. [VTT Manufacturing Technology (Finland); Raaska, L. [VTT Biotechnology and Food Research (Finland)

    1999-11-01

    The electrochemical behavior of and biofilm formation on AISI 304 stainless steel were studied in board machine environment with natural bacteria population. Open circuit potentials, redox-potential as well as different electrochemical measurements were performed. The biofilms formed were analyzed by microbial cultivation and by epifluorescence microscopy. The results of the measurements were compared with those performed both in sterilized white water and in artificial white water. The anodic polarization behavior of just immersed specimens was very similar in biotic (real), artificial and abiotic (sterilized) white water. Pitting initiated at very low potentials and continued to very negative values. The initiation of pitting became more difficult when the immersion time increased to 7 or 8 days in real, artificial or sterilized water. When the immersion time further increased, the pitting nucleated more easily in sterilized white water as well as in artificial white water than in biotic white water. In the laboratory equipment it was possible to maintain the biofilm already formed in the board mill, but the amount of sulfate reducing bacteria decreased and the amount of biofilm did not further increase. The composition and structure of the biofilm formed in laboratory differed from that formed in board mill conditions. The preliminary results indicate that the formation of biofilm in biotic white water rather inhibits than enhances the pitting corrosion of type AISI 304 stainless steel.

  18. SIMS study on the surface elemental distribution in AISI type 304 steel

    Izawa, Chika; Wagner, Stefan; Burlaka, Vladimir; Pundt, Astrid [Institut fuer Materialphysik der Universitaet Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany); Martin, Mauro; Weber, Sebastian [Gemeinsame Forschergruppe, Helmholtz-Zentrum Berlin / Ruhr-Universitaet Bochum, Universitaetsstr. 150 - IA 2/44, D-44801 Bochum (Germany); Bourgeon, Anais; Pargeter, Richard [TWI Ltd., Granta Park, Great Abington, Cambridge CB21 6AL (United Kingdom); Michler, Thorsten [Adam Opel GmbH, IPC R2-50, GM Alternative Propulsion Center Europe 65423 Ruesselsheim (Germany)

    2011-07-01

    Hydrogen embrittlement of low-Ni austenitic stainless steels is suggested to occur due to strain-induced surface alpha -martensite, since the hydrogen diffusivity in bcc phases is expected to be much higher than in the austenitic phase. But, also the local surface chemistry might be responsible for the steel susceptibility. The surface chemistry on two different surface conditions of AISI 304 was investigated by Secondary Ion Mass Spectrometry: a. directly after the machining process and b. after solution annealing process. For both AISI 304 surfaces a layered stacking of Fe- and Cr-oxide was found. The oxide layer thickness was about 5 nm for sample a., and about 10 nm for sample b. The chemical mapping on sample a. shows relatively homogeneous elemental distributions due to the fine microstructure of martensite. For sample b, Fe, Ni, SiO2, FeO and NiO are segregated at the grain boundaries. In contrast, Cr and CrO are distributed in grains.

  19. Niobium boride layers deposition on the surface AISI D2 steel by a duplex treatment

    In this paper, we investigated the possibility of deposition of niobium boride layers on the surface of AISI D2 steel by a duplex treatment. At the first step of duplex treatment, boronizing was performed on AISI D2 steel samples at 1000oC for 2h and then pre-boronized samples niobized at 850°C, 900°C and 950°C using thermo-reactive deposition method for 1–4 h. The presence of the niobium boride layers such as NbB, NbB2 and Nb3B4 and also iron boride phases such as FeB, Fe2B were examined by X-ray diffraction analysis. Scanning electron microscope (SEM) and micro-hardness measurements were realized. Experimental studies showed that the depth of the coating layers increased with increasing temperature and times and also ranged from 0.42 µm to 2.43 µm, depending on treatment time and temperature. The hardness of the niobium boride layer was 2620±180 HV0.005

  20. Improvement in cavitation erosion resistance of AISI 316L stainless steel by friction stir processing

    Hajian, M.; Abdollah-zadeh, A.; Rezaei-Nejad, S. S.; Assadi, H.; Hadavi, S. M. M.; Chung, K.; Shokouhimehr, M.

    2014-07-01

    Commercial AISI 316L plates with the initial grain size of 14.8 μm were friction stir processed (FSP) with different processing parameters, resulting in two fine-grained microstructures with the grain sizes of 4.6 and 1.7 μm. The cavitation erosion behavior, before and after FSP, was evaluated in terms of incubation time, cumulative mass loss and mean depth of erosion. A separate cavitation erosion test was performed on the transverse cross section of a FSP sample to reveal the effect of grain structure. It was observed that FSP samples, depending on their grain size, are at least 3-6 times more resistant than the base material against cavitation erosion. The improvement in cavitation erosion resistance is attributed to smaller grain structure, lower fraction of twin boundaries, and favorable crystallographic orientation of grains in FSP samples. The finer the grain size, the more cavitation erosion resistance was achieved. Moreover, the microstructures of eroded surfaces were studied using a scanning electron microscope equipped with EBSD, and an atomic force microscope. The mechanisms controlling the cavitation erosion damage in friction stir processed AISI 316L are also discussed.

  1. Improvement in cavitation erosion resistance of AISI 316L stainless steel by friction stir processing

    Hajian, M. [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Abdollah-zadeh, A., E-mail: zadeh@modares.ac.ir [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Rezaei-Nejad, S.S.; Assadi, H. [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Hadavi, S.M.M. [Department of Materials Science and Engineering, MA University of Technology, Tehran (Iran, Islamic Republic of); Chung, K. [Department of Materials Science and Engineering, Research Institute of Advanced Materials, Engineering Research Institute, Seoul National University, Seoul (Korea, Republic of); Shokouhimehr, M. [Department of Chemical Engineering, College of Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)

    2014-07-01

    Commercial AISI 316L plates with the initial grain size of 14.8 μm were friction stir processed (FSP) with different processing parameters, resulting in two fine-grained microstructures with the grain sizes of 4.6 and 1.7 μm. The cavitation erosion behavior, before and after FSP, was evaluated in terms of incubation time, cumulative mass loss and mean depth of erosion. A separate cavitation erosion test was performed on the transverse cross section of a FSP sample to reveal the effect of grain structure. It was observed that FSP samples, depending on their grain size, are at least 3–6 times more resistant than the base material against cavitation erosion. The improvement in cavitation erosion resistance is attributed to smaller grain structure, lower fraction of twin boundaries, and favorable crystallographic orientation of grains in FSP samples. The finer the grain size, the more cavitation erosion resistance was achieved. Moreover, the microstructures of eroded surfaces were studied using a scanning electron microscope equipped with EBSD, and an atomic force microscope. The mechanisms controlling the cavitation erosion damage in friction stir processed AISI 316L are also discussed.

  2. Effects of processing on the transverse fatigue properties of low-sulfur AISI 4140 steel

    Collins, Sunniva R.; Michal, Gary M.

    1993-12-01

    The effects of inclusions due to steelmaking processes on the fatigue life of AISI 4140 have been investigated. The test matrix consisted of three commercially produced heats of AISI 4140 of comparable cleanliness: one was conventionally cast (CC), and two were inert gas-shielded/ bottom-poured (IGS). One of the IGS heats was calcium-treated to explore the effects of inclusion shape control (IGS/SC). All heats were hot-rolled and reduced over 95 pct to produce bar stock of 127 to 152 mm (5 to 6 in.) in diameter. Transverse axial specimens conforming to ASTM E466 were machined, quenched, and tempered to approximately 40 HRC, and they were fatigue tested in tension-tension cycling ( R = 0.1). Test results and statistical analyses of the stress-life data show that the IGS grade has several times the fatigue strength of the CC grade at 107 cycles. Lower-limit fatigue strengths calculated at a 99.9 pct probability were 518.5 MPa (75.2 ksi) for IGS vs 55.6 MPa (8.1 ksi) for the CC grade. The IGS/SC grade had the best performance at all stress and life levels. The results obtained indicate that fatigue performance can be improved by choosing a processing method that reduces the incidence of exogenous oxides and by controlling the shape of the sulfides.

  3. Niobium boride layers deposition on the surface AISI D2 steel by a duplex treatment

    Kon, O.; Pazarlioglu, S.; Sen, S.; Sen, U.

    2015-03-01

    In this paper, we investigated the possibility of deposition of niobium boride layers on the surface of AISI D2 steel by a duplex treatment. At the first step of duplex treatment, boronizing was performed on AISI D2 steel samples at 1000oC for 2h and then pre-boronized samples niobized at 850°C, 900°C and 950°C using thermo-reactive deposition method for 1-4 h. The presence of the niobium boride layers such as NbB, NbB2 and Nb3B4 and also iron boride phases such as FeB, Fe2B were examined by X-ray diffraction analysis. Scanning electron microscope (SEM) and micro-hardness measurements were realized. Experimental studies showed that the depth of the coating layers increased with increasing temperature and times and also ranged from 0.42 µm to 2.43 µm, depending on treatment time and temperature. The hardness of the niobium boride layer was 2620±180 HV0.005.

  4. Using Mather-Type Plasma focus Device for Surface Modification of AISI304 Steel

    A 8.8 kJ plasma focus device with a nitrogen gas filling and a copper anode capsulated by aluminum was used to modify the surface of AISI304 steel substrate, in order to improve its properties. The treatment was carried out using a various number of nitrogen plasma focus shots at a pressure of 0.5 mbar and at two steel sample distances (20 and 40 mm) from the anode. The plasma diagnostics was made using the voltage and current curves recorded by a voltage divider, Rogowski coil, accompanied with calculations using a five phase radiative Lee model (RADPF5.15a) to determine the temperature and plasma density. The surface hardness of AISI304 steel was increased by 175% after plasma treatment and the thickness of the treated layers was about 1-2 μ. Results show that the surface hardness is increased with increasing shot number and decreased with increasing distance from the anode. Changes in surface morphology and the elemental composition were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). (author)

  5. Dynamic strain ageing of deformed nitrogen-alloyed AISI 316 stainless steels

    Ehrnsten, U.; Toivonen, A. [Materials and Structural Integrity, VTT Technical Research Centre of Finland, Kemistintie 3, P.O. Box 1704, FIN-02044 VTT (Finland); Ivanchenko, M.; Nevdacha, V.; Yagozinskyy, Y.; Haenninen, H. [Department of Mechanical Engineering, Helsinki University of Technology Puumiehenkuja 3, P.O. Box 4200, FIN-02015 HUT (Finland)

    2004-07-01

    Intergranular stress corrosion cracking has occurred in BWR environment in non-sensitized, deformed austenitic stainless steel materials. The affecting parameters are so far not fully known, but deformation mechanisms may be decisive. The effect of deformation and nitrogen content on the behaviour of austenitic stainless steels was investigated. The materials were austenitic stainless steels of AISI 316L type with different amounts of nitrogen (0.03 - 0.18%) and they were mechanically deformed 0, 5 and 20%. The investigations are focused on the dynamic strain ageing (DSA) behaviour. A few crack growth rate measurements are performed on nuclear grade AISI 316NG material with different degrees of deformation (0, 5 and 20%). The effects of DSA on mechanical properties of these materials are evaluated based on peaks in ultimate tensile strength and strain hardening coefficient and minimum in ductility in the DSA temperature range. Additionally, internal friction measurements have been performed in the temperature range of -100 to 600 deg. C for determining nitrogen interactions with other alloying elements and dislocations (cold-worked samples). The results show an effect of nitrogen on the stainless steel behaviour, e.g. clear indications of dynamic strain ageing and changes in the internal friction peaks as a function of nitrogen content and amount of deformation. (authors)

  6. Hybridisations Of Simulated Annealing And Modified Simplex Algorithms On A Path Of Steepest Ascent With Multi-Response For Optimal Parameter Settings Of ACO

    Luangpaiboon, P.

    2009-10-01

    Many entrepreneurs face to extreme conditions for instances; costs, quality, sales and services. Moreover, technology has always been intertwined with our demands. Then almost manufacturers or assembling lines adopt it and come out with more complicated process inevitably. At this stage, products and service improvement need to be shifted from competitors with sustainability. So, a simulated process optimisation is an alternative way for solving huge and complex problems. Metaheuristics are sequential processes that perform exploration and exploitation in the solution space aiming to efficiently find near optimal solutions with natural intelligence as a source of inspiration. One of the most well-known metaheuristics is called Ant Colony Optimisation, ACO. This paper is conducted to give an aid in complicatedness of using ACO in terms of its parameters: number of iterations, ants and moves. Proper levels of these parameters are analysed on eight noisy continuous non-linear continuous response surfaces. Considering the solution space in a specified region, some surfaces contain global optimum and multiple local optimums and some are with a curved ridge. ACO parameters are determined through hybridisations of Modified Simplex and Simulated Annealing methods on the path of Steepest Ascent, SAM. SAM was introduced to recommend preferable levels of ACO parameters via statistically significant regression analysis and Taguchi's signal to noise ratio. Other performance achievements include minimax and mean squared error measures. A series of computational experiments using each algorithm were conducted. Experimental results were analysed in terms of mean, design points and best so far solutions. It was found that results obtained from a hybridisation with stochastic procedures of Simulated Annealing method were better than that using Modified Simplex algorithm. However, the average execution time of experimental runs and number of design points using hybridisations were

  7. Extended X-Ray Absorption Fine Structure Investigation of Carbon Stabilized Expanded Austenite and Carbides in Stainless Steel AISI 316

    Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny;

    2011-01-01

    Low temperature carburized AISI 316 stainless steel - carbon expanded austenite - was investigated with EXAFS and synchrotron diffraction together with synthesized carbides of the type M3C2, M7C3 and M23C6. It was found that the chemical environment of carbon expanded austenite is not associated...

  8. HIGH SPEED END MILLING OF HARDENED AISI D3 COLD WORK TOOL STEEL WITH CBN CUTTING TOOL

    Aslan, E; CAMUŞCU, N.

    2010-01-01

    ABSTRACTIn this work, high speed end milling of AISI D3 cold-work tool steel hardened to 35 HRC and 62 HRC was investigated using CBN cutting tools. Cutting tool performance was studied with respect to tool life and surface finish of the workpiece. The effect of material hardness on the tool wear and surface roughness was also discussed.

  9. X-Ray diffraction application in studying the nitrogen fixing and aging in stainless steel AISI 304

    Solid solutions of N in AISI-304 stainless steels were aged to different degrees. The aging was monitored through X-Ray difraction measurement of the lattice parameter 'a'. The increases in 'a', due to the increase of N in solid solution were determined experimentally

  10. Surface fatigue life and failure characteristics of EX-53, CBS 1000M, and AISI 9310 gear materials

    Townsend, D. P.

    1985-01-01

    Spur gear endurance tests and rolling-element surface fatigue tests are conducted to investigate EX-53 and CBS 1000M steels for use as advanced application gear materials, to determine their endurance characteristics, and to compare the results with the standard AISI 9310 gear material. The gear pitch diameter is 8.89 cm (3.50 in). Gear test conditions are an oil inlet temperature of 320 K (116 F), an oil outlet temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench-type rolling-element fatigue tests are conducted at ambient temperature with a bar specimen speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPa (700 ksi). The EX-53 test gears have a surface fatigue life of twice that of the AISI 9310 spur gears. The CBS 1000M test gears have a surface fatigue life of more than twice that of the AISI 9310 spur gears. However, the CBS 1000M gears experience a 30-percent tooth fracture failure which limits its use as a gear material. The rolling-contact fatigue lines of RC bar specimens of EX-53 and ASISI 9310 are approximately equal. However, the CBS 1000M RC specimens have a surface fatigue life of about 50 percent that of the AISI 9310.

  11. Certeza diagnóstica en la mortalidad de una población de pacientes con trasplante cardíaco

    Marcos Amuchástegui

    2008-01-01

    Full Text Available RESUMENIntroducciónA pesar de que la morbimortalidad en el trasplante cardíaco ha sido motivo de extensoanálisis, la mayoría de los estudios y registros de mortalidad en pacientes trasplantados sebasan sobre datos clínicos. En la bibliografía existen comunicaciones aisladas de autopsiasen pacientes con trasplante cardíaco.ObjetivoDeterminar la importancia de la realización de estudios anatomopatológicos para el diagnósticode causa de muerte en un programa de trasplante cardíaco.Material y métodosSe incluyeron todos los pacientes con trasplante cardíaco fallecidos entre enero 1990 y enero2005. El diagnóstico definitivo de la causa de muerte fue corroborado por autopsia obiopsia de órgano sólido. Las causas de muerte evaluadas fueron falla precoz del injerto,rechazo celular, infección, enfermedad vascular del injerto, neoplasia y otros.ResultadosDurante el período en estudio 73 pacientes fueron sometidos a trasplante cardíaco; de ellos,fallecieron 31. Se obtuvieron 12 autopsias y 7 biopsias de órgano sólido que certificaron lacausa de muerte (61%. La causa de muerte más frecuente fue el rechazo celular mayor degrado III. En el 12,9%, la anatomía patológica difirió de la sospecha clínica de la causa demuerte.ConclusiónLa información clinicopatológica derivada de estudios post mortem es un indicador de nuestrarealidad asistencial y se constituye en un pilar fundamental para el conocimiento y elmanejo futuro de los pacientes trasplantados, por lo que consideramos que la realización deautopsias en estos pacientes es de vital importancia.REV ARGENT CARDIOL 2008;76:292-294.

  12. Certeza diagnóstica en la mortalidad de una población de pacientes con trasplante cardíaco

    Marcos Amuchástegui (h,

    2006-01-01

    Full Text Available Introducción A pesar de que la morbimortalidad en el trasplante cardíaco ha sido motivo de extenso análisis, la mayoría de los estudios y registros de mortalidad en pacientes trasplantados se basan sobre datos clínicos. En la bibliografía existen comunicaciones aisladas de autopsias en pacientes con trasplante cardíaco.Objetivo Determinar la importancia de la realización de estudios anatomopatológicos para el diagnóstico de causa de muerte en un programa de trasplante cardíaco.Material y métodosSe incluyeron todos los pacientes con trasplante cardíaco fallecidos entre enero 1990 y enero 2005. El diagnóstico definitivo de la causa de muerte fue corroborado por autopsia o biopsia de órgano sólido. Las causas de muerte evaluadas fueron falla precoz del injerto, rechazo celular, infección, enfermedad vascular del injerto, neoplasia y otros.ResultadosDurante el período en estudio 73 pacientes fueron sometidos a trasplante cardíaco; de ellos, fallecieron 31. Se obtuvieron 12 autopsias y 7 biopsias de órgano sólido que certificaron la causa de muerte (61%. La causa de muerte más frecuente fue el rechazo celular mayor de grado III. En el 12,9%, la anatomía patológica difirió de la sospecha clínica de la causa de muerte.ConclusiónLa información clinicopatológica derivada de estudios post mortem es un indicador de nuestra realidad asistencial y se constituye en un pilar fundamental para el conocimiento y el manejo futuro de los pacientes trasplantados, por lo que consideramos que la realización de autopsias en estos pacientes es de vital importancia.

  13. El calcio en los miocitos cardíacos y su papel en las miocardiopatías.

    Guido Ulate Montero; Adriana Ulate Campos

    2006-01-01

    El papel que desempeña el calcio en los miocitos cardíacos abarca un gran número de funciones, desde su rol en el acoplamiento excitación-ccontracción hasta su papel de segundo mensajero en las diversas vías de señalización, algunas de las cuales se activan en procesos que afectan la integridad del tejido miocárdico y que tienen que ver con el crecimiento y la apoptosis de los miocitos y que al final, son los que determinan la evolución de la mayoría de las cardiomiopatías. En esta revisión s...

  14. CO2 Measurements from Space: Lessons Learned from the Collaboration between the ACOS/OCO-2 and GOSAT Teams

    Crisp, D.; Eldering, A.; Gunson, M. R.

    2012-12-01

    The NASA Orbiting Carbon Observatory (OCO) and the Japanese Greenhouse gases Observing SATellite (GOSAT) were the first two missions designed to collect space-based observations of the column-averaged CO2 dry air mole fraction, XCO2, with the sensitivity, coverage, and resolution needed to quantify CO2 fluxes on regional scales over the globe. The OCO and GOSAT teams formed a close collaboration during the development phases of these missions. After the loss of OCO, the GOSAT project team invited the OCO team to contribute to the analysis of measurements collected by the GOSAT Thermal And Near infrared Sensor for carbon Observations-Fourier Transform Spectrometer (TANSO-FTS). NASA responded by reformulating the OCO science team under the Atmospheric CO2 Observations from Space (ACOS) task to exploit this opportunity. This collaboration is providing an independent GOSAT XCO2 product, and valuable insights into the retrieval algorithms, calibration methods, and validation techniques that are being developed to analyze data anticipated the NASA Orbiting Carbon Observatory-2 (OCO-2). The ACOS/OCO-2 and GOSAT teams have conducted four, joint, vicarious calibration campaigns at Railroad Valley, Nevada to track the long-term radiometric performance of the TANSO-FTS instrument. The methods used in these campaigns evolved from those used to characterize the radiometric performance of high spatial resolution, imaging spectroradiometers. For TANSO-FTS, the conventional, surface based radiometric measurements have been augmented with surface and aircraft measurements of atmospheric temperature and trace gas profiles, as well as surface observations from MODIS and ASTER to characterize spatial variations of the surface reflectance within the (relatively large) sounding footprints. Similar methods will be needed for OCO-2. The ACOS/OCO-2 retrieval algorithm and associated data screening methods have been modified to estimate XCO2 from TANSO-FTS observations. Comparisons of TANSO

  15. Transplante cardíaco em portadora de endomiocardiofibrose Heart transplantation in a patient with endomyocardial fibrosis

    Humberto F.G. de Freitas

    2005-01-01

    Full Text Available A endomiocardiofibrose é uma doença comum em países tropicais, particularmente Uganda e Nigéria, e pode acometer tanto o ventrículo esquerdo como direito, gerando uma insuficiência cardíaca restritiva que, além dos sintomas clássicos, manifesta-se por ascite desproporcional ao edema periférico. Apresentamos o caso de uma portadora de endomiocardiofibrose refratária ao tratamento clínico, submetida ao tratamento cirúrgico com melhora clínica por curto período, voltando a apresentar sintomas incapacitantes três meses após a cirurgia de ressecção de fibrose endomiocárdica e plastia tricúspide. A paciente foi então submetida a transplante cardíaco ortotópico bicaval, com boa evolução clínica. É o primeiro caso de transplante cardíaco nesta doença, mostrando-se uma alternativa de tratamento promissora.Endomyocardial fibrosis is a common disease in tropical countries, particularly Uganda and Nigeria. It may affect the right and left ventricles, creating restrictive heart failure, which, in addition to the classical symptoms, manifests as ascites disproportional to peripheral edema. We report the case of a female patient with endomyocardial fibrosis refractory to clinical treatment, who underwent surgical treatment with clinical improvement for a short period. Three months after the surgery for resection of the endomyocardial fibrosis and tricuspid valvuloplasty, the disabling symptoms reappeared. Then the patient underwent bicaval orthotopic heart transplantation, which had a good clinical outcome. This was the first case of heart transplantation for the treatment of endomyocardial fibrosis, which proved to be a promising alternative.

  16. Wear measurements of stainless steel AISI 316 by thin layer activation in cyclotron

    Nuclear energy techniques have multiple applications in medicine, agriculture and industry. Among the industrial applications, thin layer activation shows as a promising quantitative analytic method for on-line wear measurements in machine components with many advantages when compared with the conventional methods. Some of these advantages are beside the on-line measurements the possibility to carry out these measurements in specific areas where the material is activated and also for a short time required in the wear analysis. The main objective of this work was to study the viability to develop an experimental method using proton irradiation in the thin layer activation technique for wear evaluation of machine metallic components. In this work wear measurements, in stainless steel AISI 316 irradiated with 8 MeV - protons using the CV-28 Cyclotron at IPEN-CNEN/SP, were carried out. The first task of this work was the proton beam characterization in both homogeneity and incident energy using specific nuclear reactions in samples of pure Cu. Two sets of stainless steel AISI 316 samples were used. The first set were formed by 12.5 μm foils which were used to obtain the calibration curves that give the induced activity as a function of thickness. The second set of samples was stainless steel AISI 316 blocks on which consecutive programmed wear processes were performed using an automatic polishing machine. After proton irradiation the foils activated were measured with a high purity Ge detector where 56Co, 57Co, 58Co and 52Mn were determined and selected as a function of the proton energy and the radioactive decay of the radionuclides of short half-life. From these radionuclides, 56Co had shown to be the worse suitable for the calibration curve determination. For on-line wear measurements a Nal(Tl)-detector with a portable probe was used. To simulate real conditions for the wear measurements, metallic capsules were used to separate the activated material and the

  17. Resistencia al desgaste de recubrimientos Fe-Nb-Cr-W, Nb, AISI 1020 y AISI 420 producidos por proyección térmica por arco eléctrico

    López-Covaleda, E. A.

    2013-10-01

    Full Text Available The commercial materials 140MXC (with iron, tungsten, chrome, niobium, 530AS (AISI 1015 steel and 560AS (AISI 420 steel on AISI 4340 steel were deposited using thermal spray with arc. The aim of work was to evaluate the best strategy abrasive wear resistance of the system coating-substrate using the following combinations: (1 homogeneous coatings and (2 coatings depositing simultaneously 140MXC + 530AS and 140MXC + 560AS. The coatings microstructure was characterized using Optical microscopy, Scanning electron microscopy and Laser confocal microscopy. The wear resistance was evaluated through dry sand rubber wheel test (DSRW. We found that the wear resistance depends on the quantity of defects and the mechanical properties like hardness. For example, the softer coatings have the biggest wear rates and the failure mode was characterized by plastic deformation caused by particles indentation, and the other hand the failure mode at the harder materials was grooving. The details and wear mechanism of the coatings produced are described in this investigation.Mediante proyección térmica de arco eléctrico fueron depositados tres materiales comercialmente conocidos como: 140MXC (a base de hierro, wolframio, cromo y niobio, 530AS (acero AISI 1020 y 560AS (acero AISI 420, sobre acero AISI 4340. Con el objetivo de evaluar la mejor estrategia para incrementar la resistencia al desgaste abrasivo, los recubrimientos fueron depositados de dos formas: (1 monocapas homogéneas de cada material y (2 recubrimientos depositando con alambres disimiles de 140MXC + 530AS y 140MXC + 560AS. Los recubrimientos fueron caracterizados microestructuralmente mediante Difracción de rayos X, Microscopía óptica, Microscopía láser confocal y Microscopía electrónica de barrido. La evaluación de la resistencia al desgaste abrasivo se realizó mediante ensayo con arena seca y rueda de caucho (DSRW. Se encontró que la resistencia al desgaste depende entre otras de las

  18. Effects of hydrogen charging methods on ductility and fracture characteristics of AISI 9840 steel

    Biggiero, G.; Borruto, A.; Taraschi, I. [Rome Univ. (Italy). Ist. di Metallurgia e Metallografia

    1995-06-01

    Two different methods were used in the tests: the premature fracture method and the tensile test under hydrogen charging method, on AISI 9840 steel corrosion specimens. The aim of this work was to reveal the hydrogen effects on plastic deformation in tensile tests with or without simultaneous hydrogen charging. True stress-true strain curves have clearly shown the material`s different behaviour in the two tests: in the case of premature fracture tests, during plastic deformation, dislocations glide and allow hydrogen to escape and the material to partially regain its properties more rapidly; on the contrary, in the case of tensile tests under hydrogen charging, the interaction between the penetrating hydrogen and the Cottrell clouds (pre-existing hydrogen) slackens dislocation glide, so that plastic deformation is greatly reduced, as is shown both from the diagrams and the SEM analyses. (author)

  19. Applications of the essay at slow deformation velocity in pipes of stainless steel AISI-304

    Nowadays is carried out research related with the degradation mechanisms of structures, systems and/or components in the nuclear power plants, since many of the involved processes are those responsible for the dependability of these, of the integrity of the components and of the aspects of safety. The purpose of this work, was to determine the grade of susceptibility to the corrosion of a pipe of Austenitic stainless steel AISI 304, in a solution of Na CI (3.5%) to the temperatures of 60 and 90 C, in two different thermal treatments - 1. - Sensitive 650 C by 4 hours and cooled in water. 2. Solubilized to 1050 C by 1 hour and cooled in water

  20. Influence of alumina and titanium dioxide coatings on abrasive wear resistance of AISI 1045 steel

    Santos, A.; Remolina, A.; Marulanda, J.

    2016-02-01

    This project aims to compare the behaviour of an AISI 1045 steel's abrasive wear resistance when is covered with aluminium oxide (Al2O3) or Titanium dioxide (TiO2), of nanometric size, using the technique of thermal hot spray, which allows to directly project the suspension particles on the used substrate. The tests are performed based on the ASTM G65-04 standard (Standard Test Method for Measuring Abrasion Using the Dry Sand/Rubber Apparatus). The results show that the amount of, lost material increases linearly with the travelled distance; also determined that the thermal treatment of hardening-tempering and the alumina and titanium dioxide coatings decrease in average a 12.9, 39.6 and 29.3% respectively the volume of released material during abrasive wear test.

  1. Surface Modification by Nitrogen Plasma Immersion Ion Implantation on Austenitic AISI 304 Stainless Steel

    Miguel CASTRO-COLIN; William DURRER; Jorge ALPEZ; Enrique RAMIREZ-HOMS

    2016-01-01

    Surfaces of AISI 304 austenitic stainless steel plates nitrided by plasma immersion ion implantation (PIII) technology were studied by means of Auger electron spectroscopy (AES)and X-ray photoelectron spectroscopy (XPS)to determine the effect of the nitriding process on the surface and subjacent layers.Elemental compositions obtained by AES and XPS at varying depths indicate that the saturation of N is relatively constant as a function of depth,indicating the reliability of PIII technology for subsurface saturation.It is concluded that the concentrations of both Cr and O increase with depth,the subjacent oxide is driven by the Ar+ sputtering process used to access the lower layers,and then N is bound to Cr.

  2. Acoustic Emission Methodology to Evaluate the Fracture Toughness in Heat Treated AISI D2 Tool Steel

    Mostafavi, Sajad; Fotouhi, Mohamad; Motasemi, Abed; Ahmadi, Mehdi; Sindi, Cevat Teymuri

    2012-10-01

    In this article, fracture toughness behavior of tool steel was investigated using Acoustic Emission (AE) monitoring. Fracture toughness ( K IC) values of a specific tool steel was determined by applying various approaches based on conventional AE parameters, such as Acoustic Emission Cumulative Count (AECC), Acoustic Emission Energy Rate (AEER), and the combination of mechanical characteristics and AE information called sentry function. The critical fracture toughness values during crack propagation were achieved by means of relationship between the integral of the sentry function and cumulative fracture toughness (KICUM). Specimens were selected from AISI D2 cold-work tool steel and were heat treated at four different tempering conditions (300, 450, 525, and 575 °C). The results achieved through AE approaches were then compared with a methodology proposed by compact specimen testing according to ASTM standard E399. It was concluded that AE information was an efficient method to investigate fracture characteristics.

  3. Microstructure evolution and texture development in a friction stir-processed AISI D2 tool steel

    Yasavol, N.; Abdollah-zadeh, A.; Vieira, M. T.; Jafarian, H. R.

    2014-02-01

    Crystallographic texture developments during friction stir processing (FSP) of AISI D2 tool were studied with respect to grain sizes in different tool rotation rates. Comparison of the grain sizes in various rotation rates confirmed that grain refinement occurred progressively in higher rotation rates by severe plastic deformation. It was found that the predominant mechanism during FSP should be dynamic recovery (DRV) happened concurrently with continuous dynamic recrystallization (CDRX) caused by particle-stimulated nucleation (PSN). The developed shear texture relates to the ideal shear textures of D1 and D2 in bcc metals. The prevalence of highly dense arrangement of close-packed planes of bcc and the lowest Taylor factor showed the lowest compressive residual stress which is responsible for better mechanical properties compared with the grain-precipitate refinement.

  4. Electromagnetic nondestructive evaluation of tempering process in AISI D2 tool steel

    Kahrobaee, Saeed; Kashefi, Mehrdad

    2015-05-01

    The present paper investigates the potential of using eddy current technique as a reliable nondestructive tool to detect microstructural changes during the different stages of tempering treatment in AISI D2 tool steel. Five stages occur in tempering of the steel: precipitation of ɛ carbides, formation of cementite, retained austenite decomposition, secondary hardening effect and spheroidization of carbides. These stages were characterized by destructive methods, including dilatometry, differential scanning calorimetry, X-ray diffraction, scanning electron microscopic observations, and hardness measurements. The microstructural changes alter the electrical resistivity/magnetic saturation, which, in turn, influence the eddy current signals. Two EC parameters, induced voltage sensed by pickup coil and impedance point detected by excitation coil, were evaluated as a function of tempering temperature to characterize the microstructural features, nondestructively. The study revealed that a good correlation exists between the EC parameters and the microstructural changes.

  5. Vruća prerada AISI A2 alatnog čelika

    Večko Pirtovšek, T.; Peruš, I.; Kugler, G.; Turk, R.; M. Terčelj

    2008-01-01

    Za postizanje više gospodarnosti proizvodnje AISI A2 alatnog čelika potrebni su koraci istraživanja vezani na postizanja tehnološke plastičnosti i uspješno predvidjanje krivulja tečenja. Sa metodom CAE neuralnih mreža bile su predviđene krivulje tečenja i za odgovarajuća temperaturna stanja i brzine deformacija. Pomoću pokusa vrućeg sabijanja utvrđeno je, da ulazna mikrostruktura utječe na donju temperaturnu granicu, a kemijski sastav na gornju temperaturnu granicu radnog područja s obzirom n...

  6. Microstructural characterization of laser surface melted AISI M2 tool steel.

    Arias, J; Cabeza, M; Castro, G; Feijoo, I; Merino, P; Pena, G

    2010-09-01

    We describe the microstructure of Nd:YAG continuous wave laser surface melted high-speed steel, namely AISI M2, treated with different laser scanning speeds and beam diameters on its surface. Microstructural characterization of the remelted surface layer was performed using light optical and scanning electron microscopy and X-ray diffraction. The combination of the three techniques provided new insights into the substantial changes induced by laser surface melting of the steel surface layer. The advantage of the method is that it avoids the difficult and tedious work of preparing samples of this hard material for transmission electron microscopy, which is the technique normally used to study these fine microstructures. A melted zone with a dendritic structure and a partially melted zone with a heterogeneous cellular structure were observed. M(2)C carbides with different morphologies were identified in the resolidified surface layer after laser melting. PMID:20701656

  7. Multi-scale modelling of AISI H11 martensitic tool steel surface anisotropic mechanical behaviour

    Zouaghi Ahmed

    2014-06-01

    Full Text Available In this work, a numerical investigation is carried out on the anisotropic and heterogeneous behaviour of the AISI H11 martensitic tool steel surface using finite element method and a multi-scale approach. An elasto-viscoplastic model that considers nonlinear isotropic and kinematic hardenings is implemented in the finite elements code ABAQUS using small strain assumption. The parameters of the constitutive equations are identified using macroscopic quasi-static and cyclic material responses by the mean of a localization rule. Virtual realistic microstructures, consisting of laths and grains, are generated using particular Voronoï tessellations. These microstructures consider the specific crystallographic orientations α’/γ. Finite element investigation is then performed. The local heterogeneous and anisotropic behaviour of the surface as well as the subsurface is shown under quasi-static and cyclic mechanical loadings. The laths morphology and crystallographic orientation have an important impact on the local mechanical fields.

  8. Determining Ms temperature on a AISI D2 cold work tool steel using magnetic Barkhausen noise

    Highlights: ► MBN was used to follow the martensite transformation in a tool steel. ► The results were compared with resistivity experiments. ► The Ms was estimated with Andrews equation coupled to ThermoCalc calculations. The experimental results showed good agreement. -- Abstract: The use of Magnetic Barkhausen Noise (MBN) as a experimental method for measuring the martensite start (Ms) temperature was explored, using as model system a cold-work tool steel (AISI D2) austenitized at a very high temperature (1473 K), so as to transform in sub-zero temperatures. The progress of the transformation was also followed with electrical resistance measurements, optical microscopy and scanning electron microscopy. Both MBN and resistivity measurements showed a change near 230 K during cooling, corresponding to the Ms temperature, as compared with 245 K, estimated with Andrews empirical equation applied to the austenite composition calculated using ThermoCalc

  9. Studies on corrosion protection of laser hybrid welded AISI 316 by laser remelting

    Olsen, Flemming Ove; Ambat, Rajan; Rasmussen, A.J.

    2005-01-01

    Unlike in autogenous laser welding, hybrid laser welding of stainless steel could introduce grain boundary carbides due to low cooling rates. Formation of grain boundary carbides leads to reduced corrosion properties. Studies have initially been carried out on hybrid laser welding and subsequent...... laser surface melting on microstructure and corrosion behaviour of AISI 316L welds. Welding and laser treatment parameters were varied. General corrosion behaviour of the weld and laser treated surface was characterised using a gel visualization test. The local electrochemistry of the weld and laser...... treated surface was investigated using a novel micro electrochemical technique with a tip resolution of ~1 mm. Results show that hybrid laser welding of 316L has increased corrosion susceptibility probably as a result of grain boundary carbide formation. However a suitable post laser treatment could...

  10. Effect of rare earth oxide additions on oxidation behavior of AISI 304L stainless steel

    Marina Fuser Pillis

    2006-12-01

    Full Text Available AISI 304L stainless steel powder compacts containing 2 vol% high purity rare earth oxides were prepared by mixing the different powders in a vibratory mill followed by pressing. The compacts thus obtained were sintered in a vacuum furnace and isothermal oxidation measurements were carried out in a muffle furnace, in air, up to 200 hours at 900 °C. The oxidized surfaces were examined in a scanning electron microscope and micro regions of the reaction products were studied using energy dispersive analysis. The addition of rare earth oxides decreased the oxidation rate of the stainless steel. Further evidence of predominant oxygen ion diffusion controlling the overall oxidation process in rare earth containing chromium oxide forming alloys has been observed.

  11. Studies on corrosion protection of laser hybrid welded AISI 316 by laser remelting

    Olsen, Flemming Ove; Ambat, Rajan; Rasmussen, A.J.

    2005-01-01

    laser surface melting on microstructure and corrosion behaviour of AISI 316L welds. Welding and laser treatment parameters were varied. General corrosion behaviour of the weld and laser treated surface was characterised using a gel visualization test. The local electrochemistry of the weld and laser......Unlike in autogenous laser welding, hybrid laser welding of stainless steel could introduce grain boundary carbides due to low cooling rates. Formation of grain boundary carbides leads to reduced corrosion properties. Studies have initially been carried out on hybrid laser welding and subsequent...... treated surface was investigated using a novel micro electrochemical technique with a tip resolution of ~1 mm. Results show that hybrid laser welding of 316L has increased corrosion susceptibility probably as a result of grain boundary carbide formation. However a suitable post laser treatment could...

  12. Influence of Laser Peening on Phase Transformation and Corrosion Resistance of AISI 321 steel

    Karthik, D.; Swaroop, S.

    2016-07-01

    The objective of this study is to investigate the influence of laser peening without coating (LPwC) on austenitic to martensitic (γ → α') phase transformation and corrosion behavior of austenitic stainless steel AISI 321 in 3.5% NaCl environment. Results indicate that LPwC induces a large compressive residual stresses of nearly -854 MPa and γ → α' phase transformation of about 18% (volume fraction). Microstructures of peened surface confirmed the γ → α' phase transformation and showed no grain refinement. Hardness increased slightly with a case depth of 900 μm. Despite the smaller surface roughness introduced, corrosion resistance improved after peening due to compressive residual stresses.

  13. The effect of internal hydrogen on surface slip localisation on polycrystalline AISI 316L stainless steel

    A statistical analysis of the effect of internal hydrogen on the surface slip morphology of relatively high nickel content AISI 316L type austenitic stainless steel was carried out on high resolution data obtained by atomic force microscopy. Surface plastic strain localisation was studied for different hydrogen contents, two grain sizes, and two plastic strain levels. The height and spacing of approximately 8000 slip bands, observed on 12 specimens, are shown to follow log-normal distributions. Hydrogen increased the mean slip-band height and the mean slip-band spacing for the two macroscopic plastic strain levels considered, and for the two hydrogen concentrations in coarse-grained specimens. The hydrogen effect was also observed for fine-grained specimens, but only for the highest hydrogen concentration. In addition, the emerging dislocation velocity increased by a factor 3 for high hydrogen content.

  14. Effect of constraint on fracture behavior of welded 17mn4 and AISI304 steels

    In this study, 17Mn4 (P295GH) pressure vessels steel and AISI304 stainless steel were welded with ER309L austenitic consumable. In experimental part of the study, tensile tests were conducted on welded plates and variation of hardness values along specimen was measured. J-integral fracture toughness values were investigated for different crack locations. In order to determine the regions where plastic deformation did not take place due to constraint, uni-axial tensile test was performed on welded tensile specimen after attaching strain gauges. In numerical part of the study, finite element (FE) analyses were conducted by fixing 2-D models precracked on different locations by using ANSYS software. In these models, stress triaxiality and plastic deformation characteristics around crack tip were determined for each crack locations after stress and strain analyses. The limitation on the extension of plastic deformation at diffusion line causes extra increase in stress triaxiality at crack tip

  15. Effect of the Surface Roughness on Galvanic Corrosion of AISI 316 Stainless Steel

    One of the major problems that can be raised in different mechanical designs in many different applications such as reactors, piping systems and production of hot cells, machine tools, is the galvanic corrosion. Many studies have been carried out concerning the dangerous effect of galvanic corrosion that usually occur between two mating components of dissimilar metals. So far limited attention has been paid to the effect of the surface roughness of two mating parts of two mating parts of same material on their mutual galvanic corrosion. The present work presents a practical study on galvanic corrosion concerning the remarkable effect of the use of two mating parts of same materials (AISI 316 St. St.) but having different values of surface roughness. From this investigation, it is concluded that designers must classify the surface roughness of the mating parts in their design to have the same value, to minimize galvanic corrosion

  16. Analysis of deformation induced martensite in AISI 316L stainless steel

    Jagarinec, Darko; Kirbis, Peter; Predan, Jozef; Vuherer, Tomaz; Gubeljak, Nenad [Maribor Univ. (Slovenia). Faculty of Mechanical Engineering

    2016-08-01

    Metastable austenite stainless steel AISI 316L is sensitive to cold deformation, where transformation from austenite to martensite occurred. The bending deformation as the formation process leads to tensile and compression throughout the thickness of the billet. Tensile testing of the specimen causes differences in the true stress-strain along the contraction neck prior to fracture as well. The aim of the paper is to find correlation between microhardness as brief inspection parameters and extension of martensitic transformation. The total equivalent plastic strain extend diagram obtained by numerical simulation of bending was compared with tensile true stress-strain diagram. Results show very good correlation between hardness, true strain and martesite content. Therefore, one can conclude that by hardness measurement, it is possible to measure the level of equivalent plastic strain until ultimate tensile stress as a linear correlation between hardness, true strain and martesite content.

  17. Corrosion behavior of low energy, high temperature nitrogen ion-implanted AISI 304 stainless steel

    M Ghorannevis; A Shokouhy; M M Larijani; S H Haji Hosseini; M Yari; A Anvari; M Gholipur Shahraki; A H Sari; M R Hantehzadeh

    2007-01-01

    This work presents the results of a low-energy nitrogen ion implantation of AISI 304 type stainless steel (SS) at a moderate temperature of about 500° C. The nitrogen ions are extracted from a Kauffman-type ion source at an energy of 30 keV, and ion current density of 100 A cm-2. Nitrogen ion concentration of 6 × 1017, 8 × 1017 and 1018 ions cm-2, were selected for our study. The X-ray diffraction results show the formation of CrN polycrystalline phase after nitrogen bombardment and a change of crystallinity due to the change in nitrogen ion concentration. The secondary ion mass spectrometry (SIMS) results show the formation of CrN phases too. Corrosion test has shown that corrosion resistance is enhanced by increasing nitrogen ion concentration.

  18. Influence Of Surface Roughness On Ultra-High-Cycle Fatigue Of Aisi 4140 Steel.

    Daniel Januário Cordeiro Gomes

    2015-04-01

    Full Text Available Low and high-cycle fatigue life regimes are well studied and are relatively well understood. However, recent fatigue studies on steels have shown that fatigue failures can occur at low amplitudes even below the conventional fatigue limit in the ultra-high-cycle fatigue range (life higher than 107 cycles. Fatigue life in the regime of 106 to 108 cycles-to-failure in terms of the influence of manufacturing processes on fatigue strength is examined. Specifically, the influence of surface roughness of turned surfaces of AISI 4140 steel specimens on fatigue strength in the giga cycle or ultra-high-cycle fatigue range is evaluated. The fatigue experiments were carried out at room temperature, with zero mean stress, on a rotating-bending fatigue testing machine of the constant bending moment type. The fatigue strength of the specimens were determined using the staircase (or up-and-down method.

  19. An investigation of the aseptic loosening of an AISI 316L stainless steel hip prosthesis

    The total replacement of joints by the implantation of permanently indwelling prosthetic components has been one of the major successes of modern surgery in terms of relieving pain and correcting deformity. However, the aseptic loosening of a prosthetic-joint component is the most common reason for joint-revision surgery. Furthermore, it is thought that wear particles are one of the major contributors to the development and perpetuation of aseptic loosening. The aim of the present study was to identify the factors related to the aseptic loosening of an AISI 316L stainless steel total hip prosthesis. The stem was evaluated by x-ray photoelectron spectroscopy, with polished and rough regions being analyzed in order to establish the differences in the chemical compositions of both regions. Specific areas were examined using scanning electron microscopy with energy dispersive x-ray spectroscopy and light microscopy.

  20. Effect of adhesive geometry on the tensile properties of AISI 1350 steel

    A. Yasar

    2011-01-01

    Full Text Available It is utilized increasingly to use adhesive bonding in automotive industry to join structural components of metallic materials. The aim of this experimental study is to extend the information available to the automotive design engineer and contribute the better understanding of how the various geometrical shaped of steel parts affect the adhesive bonding. In this study, different types of lap joints, such as butt, step butt, scarf, tubular lap, were used to determine the mechanical strength of SAE/AISI 1350 steel. It has been observed that the cylindrical geometries can be subject to more stress compared to square specimens generally and the geometries with both tensile and shear stress can stand more stress per unit compared with the specimens with only tensile stress.

  1. Microstructure and Hardness of High Temperature Gas Nitrided AISI 420 Martensitic Stainless Steel

    Ibrahim Nor Nurulhuda Md.

    2014-07-01

    Full Text Available This study examined the microstructure and hardness of as-received and nitrided AISI 420 martensitic stainless steels. High temperature gas nitriding was employed to treat the steels at 1200°C for one hour and four hours using nitrogen gas, followed by furnace cooled. Chromium nitride and iron nitride were formed and concentrated at the outmost surface area of the steels since this region contained the highest concentration of nitrogen. The grain size enlarged at the interior region of the nitrided steels due to nitriding at temperature above the recrystallization temperature of the steel and followed by slow cooling. The nitrided steels produced higher surface hardness compared to as-received steel due to the presence of nitrogen and the precipitation of nitrides. Harder steel was produced when nitriding at four hours compared to one hour since more nitrogen permeated into the steel.

  2. Diffusion characteristics of plasma nitrided hard chromium on AISI 1010 steel

    Danisman, Murat [Gedik Univ., Istanbul (Turkey). Electronic Engineering Dept.; Kocabas, Mustafa; Cansever, Nurhan [Yildiz Technical Univ., Istanbul (Turkey)

    2015-06-01

    In order to investigate the different Cr-N formation characteristics of plasma nitrided hard Cr coatings, Cr was electrodeposited on AISI 1010 steel and plasma nitrided at 600, 700 and 800 C for 3 h, 5 h and 7 h, respectively. Phase analyses of resulting Cr-N phases and grain size of Cr layer before and after nitriding process were calculated by X-ray diffraction analysis. Structure of nitride layer and its thickness were analyzed using scanning electron microscopy micrographs. The micrographs indicated that samples consisted of three distinctive layers. In order to distinguish these layers, scanning electron microscopy and energy dispersive spectroscopy (EDX) analysis were used as well as elemental distribution versus depth was plotted. The Cr-N diffusion was investigated by layer thickness measurements, and diffusion coefficient as well as activation energies were calculated.

  3. Effect of plasma nitriding time on surface properties of hard chromium electroplated AISI 1010 steel

    Kocabas, Mustafa [Yildiz Technical Univ., Istanbul (Turkey). Metallurgical and Materials Engineering Dept.; Danisman, Murat [Gedik Univ., Istanbul (Turkey). Electrical and Electronic Engineering Dept.; Cansever, Nurhan [Yildiz Technical Univ., Istanbul (Turkey); Uelker, Suekrue [Afyon Kocatepe Univ. (Turkey). Dept. of Mechanical Engineering

    2015-06-01

    Properties of steel can be enhanced by surface treatments such as coating. In some cases, further treatments such as nitriding can also be used in order to get even better results. In order to investigate the properties of nitride layer on hard Cr coated AISI 1010 steel, substrates were electroplated to form hard Cr coatings. Then hard Cr coatings were plasma nitrided at 700 C for 3 h, 5 h and 7 h and nitride phases on the coatings were investigated by X-ray diffraction analysis. The layer thickness and surface properties of nitride films were investigated by scanning electron microscopy. The hardness and adhesion properties of Cr-N phases were examined using nano indentation and Daimler-Benz Rockwell C adhesion tests. The highest measured hardness was 24.1 GPa and all the three samples exhibited poor adhesion.

  4. Experimental study of dual-beam laser welding of AISI 4140 steel

    Liu, Y.N.; Kannatey-Asibu, E. Jr. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Mechanical Engineering and Applied Mechanics

    1997-09-01

    Experiments were conducted to assess the impact of dual-beam laser welding on the cooling rates, and thus microstructure and hardness, of weldments. Temperature measurements were continuously recorded using K-type thermocouples. The results indicate that dual-beam laser welding reduces the hardness of a weldment when compared to the case of single-beam laser welding. For example, the hardness of the hot-rolled AISI 4140 steel used was about 283 HB before laser welding. After laser welding with a power of 800 W and a welding speed of 10 mm/s, the hardness became 552 HB; but with a preheating power of 800 W and an interbeam spacing of 10 mm, the hardness reduced to 477 HB for the same welding speed. The impacts of minor heat source power, welding speed and interbeam spacing on weldment hardness and weld shape for both preheating and postheating cases are discussed.

  5. Stress corrosion cracking of AISI 321 stainless steel in acidic chloride solution

    Yanliang Huang

    2002-02-01

    The stress corrosion cracking (SCC) of AISI 321 stainless steel in acidic chloride solution was studied by slow strain rate (SSR) technique and fracture mechanics method. The fractured surface was characterized by cleavage fracture. In order to clarify the SCC mechanism, the effects of inhibitor KI on SCC behaviour were also included in this paper. A study showed that the inhibition effects of KI on SCC were mainly attributed to the anodic reaction of the corrosion process. The results of strain distribution in front of the crack tip of the fatigue pre-cracked plate specimens in air, in the blank solution (acidic chloride solution without inhibitor KI) and in the solution added with KI measured by speckle interferometry (SPI) support the unified mechanism of SCC and corrosion fatigue cracking (CFC).

  6. Quantifying Cutting and Wearing Behaviors of TiN- and CrNCoated AISI 1070 Steel

    Ahmet Cakan

    2008-11-01

    Full Text Available Hard coatings such as titanium nitride (TiN and chromium nitride (CrN are widely used in cutting and forming tools against wear and corrosion. In the present study, hard coating films were deposited onto AISI 1070 steels by a cathodic arc evaporation plating (CAVP technique. These samples were subjected to wear in a conventional lathe for investigating the tribological behaviour of coating structure, and prenitrided subsurface composition was characterized using scanning electron microscopy (SEM, line scan analyses and X-ray diffraction (XRD. The wear properties of TiN- and CrNcoated samples were determined using an on-line monitoring system. The results show that TiN-coated samples demonstrate higher wear resistance than CrN-coated samples.

  7. Effect of constraint on fracture behavior of welded 17mn4 and AISI304 steels

    Uyulgan, Bahadir; Aksoy, Tevfik [Dokuz Eylul University, Izmir (Turkmenistan); Cetinel, Hakan [Celal Bayar University, Manisa (Turkmenistan)

    2011-09-15

    In this study, 17Mn4 (P295GH) pressure vessels steel and AISI304 stainless steel were welded with ER309L austenitic consumable. In experimental part of the study, tensile tests were conducted on welded plates and variation of hardness values along specimen was measured. J-integral fracture toughness values were investigated for different crack locations. In order to determine the regions where plastic deformation did not take place due to constraint, uni-axial tensile test was performed on welded tensile specimen after attaching strain gauges. In numerical part of the study, finite element (FE) analyses were conducted by fixing 2-D models precracked on different locations by using ANSYS software. In these models, stress triaxiality and plastic deformation characteristics around crack tip were determined for each crack locations after stress and strain analyses. The limitation on the extension of plastic deformation at diffusion line causes extra increase in stress triaxiality at crack tip.

  8. Correlation of substructure with time-dependent fatigue properties of aisi304 stainless steel

    Ermi, A. M.; Moteff, John

    1982-09-01

    Transmission electron microscopy was employed to study the substructure of AISI 304 stainless steel tested at 482, 593, and 650 °C in low-cycle fatigue with various hold times. Total strains investigated ranged from 0.5 to 2.0 pct, strain rates of 4 E-03 and 4 E-05 s-1. The cell size was found to be inversely related to the relaxed tensile saturation stress, but with different constants of proportionality for the two strain rates. At the lower strain rate, substructures tended to resemble those produced by pure creep. A modified work-hardening theory was used to relate the peak saturation stress to both plastic strain and cell size.

  9. Surface effects induced by cathodic hydrogenation in type AISI 304 stainless steel

    Cathodic hydrogen charging of type AISI 304 stainless steel modified its austenitic structure, giving rise to the formation of two new martensitic phases and the appearance of cracks, in most cases delayed. As electrolyte a 1 N H2 S O4 solution containing As2 O3 was employed. The cathodic hydrogenation was carries out at room temperature. The transformed phases were identified with black and white and coloured metallographic techniques, as well as by X-ray diffraction. The effect of cathodic hydrogenation in samples uniaxially tensile tested with constant nominal strain rate was investigated. It was concluded that the number of cracks per unit surface area changes with hydrogenation conditions and that hydrogen should be present for the embrittlement to occur. (author)

  10. Effect of Starch Binders in Alumina Coatings on Aisi 316 L Stainless Steel for Medical Application

    Ghazali, M. J.; Pauzi, A. A.; Azhari, C. H.; Ghani, J. A.; Sulong, A. B.; Mustafa, R.

    A slurry immersion technique of alumina coatings was carried out on several AISI 316 L stainless steels using two types of binding agents; commercial starch and Sarawakian starch (sago), which were also mixed with polyvinylchloride (PVA) for strengthening purposes. The sintering temperatures in this work were varied from 500 to 1000°C. Prior to sintering process, all stainless steels were metallographically ground and polished to approximately 0.6 µm of average roughness. Detailed characterisations on the sintered specimens were carried out with the aid of the secondary electron microscopy (SEM), microhardness and a profilometer. The results revealed that coated steels using sago binder showed improved adhesion and homogenous microstructures with greater hardness of 2642 HV than those found in coated steel with commercial starch after sintering process.

  11. Microstructure and Texture Evolutions in AISI 1050 Steel by Flow Forming

    Bedekar, Vikram [Timken Technology Center, Canton, OH; Pauskar, Praveen [Ohio State University, Columbus; Shivpuri, Rajiv [Ohio State University, Columbus; Howe, Jane Y [ORNL

    2014-01-01

    Hot rolled and annealed AISI 1050 steel cylindrical coupons were flow formed at different levels of deformation (66% and 90% wall thickness reduction). TEM studies revealed development of ultra fine (sub) grain cell structure due to severe plastic deformation. The transverse subgrain size changed from 10 m (beginning) to 300nm (66% deformation) to 40nm (90% deformation). EBSD study revealed decreased recrystallization fraction at 90% deformation compared with 66% deformation due to orientation pinning from preferred orientation along {002} planes. No evidence of dislocation pinning or cracking was observed on any samples. The aim of the present work is to study the deformation behaviour and microstructural evolution during conventional flow forming process. The study also sheds light on the strengthening behaviour and structural changes during severe straining.

  12. Adhesion of composite carbon/hydroxyapatite coatings on AISI 316L medical steel

    J. Gawroński

    2009-07-01

    Full Text Available In this paper are contains the results of studies concerning the problems associated with increased of hydroxyapatite (HAp adhesion, manufactured by using Pulse Laser Deposition (PLD method, to the austenitic steel (AISI 316L through the coating of carbon interlayer on it. Carbon coating was deposited by Radio Frequency Plasma Assisted Chemical Vapour Deposition (RF PACVD method.Test results unequivocally showed that the intermediate carbon layer in a determined manner increase the adhesion of hydroxyapatite to the metallic substrate. Obtained results give rise to deal with issues of manufacturing composite bilayer – carbon film/HAp – on ready implants, casted from austenitic cast steel by lost-wax process method as well as in gypsum forms.

  13. Effect of Nitridation Time on the Surface Hardness of Medium Carbon Steels (AISI 1045)

    It has been investigated the effect of nitridation time on the surface hardness of medium carbon steels (AISI 1045). Parameters determining to the results were flow rate of the nitrogen gas, temperature and time. In this experiments, sample having diameter of 15 mm, thick 2 mm placed in tube of glass with diameter 35 mm heated 550 oC, flow rate and temperature were kept constants, 100 cc/minutes and 550 oC respectively, while the time were varied from 5, 10, 20 and 30 hours. It was found, that for the nitridation time of 5, 10, 20, and 30 hours, the surface hardness increased from 145 VHN to, 23.7, 296.8, 382.4 and 426.1 VHN, respectively. (author)

  14. Irradiation creep in bending of cold-worked AISI 316 stainless steel at low neutron fluence

    The results from the first and second interim examinations of a test to measure irradiation creep in bending of 20 percent cold-worked AISI 316 stainless steel are presented. These low-fluence results indicate that irradiation creep in bending exhibits a larger primary creep component of the total strain as compared with creep in biaxial pressurized tubes of the same heat of material, but the secondary creep rates in the two cases appear to be similar. The data also indicate that the bending strains have a linear fluence and stress dependency, and strains measured on beams fabricated parallel to and transverse to the direction of cold work are similar, indicating that material texture anisotropy does not effect irradiation creep in bending. 6 refs

  15. Evaluation of the corrosion resistance of AISI 316 stainless steel filters

    Luzinete Pereira Barbosa

    2005-06-01

    Full Text Available In this investigation, the corrosion resistance of AISI 316 SS filters prepared with powders in the size ranges 74-44 µm and 210-105 µm and compacted with pressures of 300 MPa and 400 MPa has been evaluated in naturally aerated 0.5 M H2SO4 solution at 25 °C. Weight loss of filters manufactured with compacting pressure of 400 MPa were significantly higher than that of filters compacted at 300 MPa. The filter compacted at 400 MPa had higher carbon and nitrogen contents compared to those compacted at 300 MPa. The former also had chromium rich precipitates and oxides in the grain boundaries. The pores in filters compacted at 400 MPa were smaller than in filters compacted at 300 MPa. Smaller pores favor the formation of concentration cells and consequently, increased crevice corrosion.

  16. Determining Ms temperature on a AISI D2 cold work tool steel using magnetic Barkhausen noise

    Huallpa, Edgar Apaza, E-mail: gared1@gmail.com [Escola Politécnica da Universidade de São Paulo, Av. Prof. Mello Moraes 2463, 05508-030 SP (Brazil); Sánchez, J. Capó, E-mail: jcapo@usp.br [Departamento de Física, Facultad de Ciencias Naturales, Universidad de Oriente, Av. Patricio Lumumba s/n 90500, Santiago de Cuba (Cuba); Padovese, L.R., E-mail: lrpadove@usp.br [Escola Politécnica da Universidade de São Paulo, Av. Prof. Mello Moraes 2463, 05508-030 SP (Brazil); Goldenstein, Hélio, E-mail: hgoldens@usp.br [Escola Politécnica da Universidade de São Paulo, Av. Prof. Mello Moraes 2463, 05508-030 SP (Brazil)

    2013-11-15

    Highlights: ► MBN was used to follow the martensite transformation in a tool steel. ► The results were compared with resistivity experiments. ► The Ms was estimated with Andrews equation coupled to ThermoCalc calculations. The experimental results showed good agreement. -- Abstract: The use of Magnetic Barkhausen Noise (MBN) as a experimental method for measuring the martensite start (Ms) temperature was explored, using as model system a cold-work tool steel (AISI D2) austenitized at a very high temperature (1473 K), so as to transform in sub-zero temperatures. The progress of the transformation was also followed with electrical resistance measurements, optical microscopy and scanning electron microscopy. Both MBN and resistivity measurements showed a change near 230 K during cooling, corresponding to the Ms temperature, as compared with 245 K, estimated with Andrews empirical equation applied to the austenite composition calculated using ThermoCalc.

  17. Application of radionuclide techniques on AISI 316 stainless steel wear measurements

    In the last years a wide development in the area of surfaces treatment was observed in order to reduce the wear phenomena in machine components, motors, tools. In this work, sheets of stainless AISI 316 with thickness of 12,5 μm, which simulates successive and equal cuts in a block, were irradiated with 9 MeV protons at the CV-28 cyclotron. The induced activity in each foil was measured with a Ge(Li) detector, and the variation of this activity, as function of irradiated depth, was followed. In this activation with protons nominated thin layer activation has some advantages when compared to neutron activation. In the case the activation of foils of stainless steel 316 the peaks related to 52 Mn, 56 Co, 57 Co and 58 Co were clearly discriminated in the spectrum and this fact is used to establish a calibration curve for wear measurements. (author)

  18. 3DII implantation effect on corrosion properties of the AISI/SAE 1020 steel

    Dulce M., H.J.; Rueda V., Alejandro [Universidad Francisco de Paula Santander, A.A. 1055, Cucuta (Colombia); Dougar-Jabon, Valeri [Universidad Industrial de Santander, A.A. 678, Bucaramanga (Colombia)

    2005-08-01

    The three dimensional ion implantation technology (3DII) is one of the methods of improving the tribological characteristics and resistance to hydrogen embrittlement processes in metals. In this report, some results concerning the resistance effect of nitrogen ion implantation to oxidation of the sample, made of AISI/SAE 1020 steel, are given. The nitrogen ions were implanted in the discharge chamber of the JUPITER reactor. Both the treated and untreated samples were tested through potential-static measurements, which permitted to determine the corrosion current, the slopes that characterise the braking level of anode and cathode reactions. The polarization resistance near the corrosion potential is calculated. The results of the study encourage to consider the nitrogen ion implantation in high voltage and low pressure discharges as one of the methods of anticorrosive protection which do not change the geometric configuration of the treated steel pieces. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. ANALYSIS OF CUTTING FORCE AND CHIP MORPHOLOGY DURING HARD TURNING OF AISI D2 STEEL

    X. M. ANTHONY

    2015-03-01

    Full Text Available In this research work AISI D2 tool steel at a hardness of 55 HRC is being used for experimental investigation. Cutting speed, feed rate and depth of cut are the cutting parameters considered for the experimentation along with tool geometry namely, nose radius, clearance angle and rake angle. Three different cutting tool materials are used for experimentation namely multicoated carbide, cermet and ceramic inserts. The cutting force generated during the machining process is being measured using Kistler dynamometer and recorded for further evaluation. The chips produced during the machining process for every experimental trail is also collected for understanding the chip morphology. Based on the experimental data collected Analysis of Variance (ANOVA was conducted to understand the influence of all cutting parameters and tool geometry on cutting force.

  20. Stress corrosion cracking of stainless steel AISI 316L HAZ in PWR nuclear reactor environment

    In pressurized water reactors (PWRs), low alloy carbon steels and stainless steel are widely used in the primary water circuits. In most cases, Ni alloys are used to joint these materials and form dissimilar welds. These alloys are known to accommodate the differences in composition and thermal expansion of the two materials. Stress corrosion cracking of metals and alloys is caused by synergistic effects of environment, material condition and stress. Over the last thirty years, CST has been observed in dissimilar metal welds. This study presents a comparative work between the CST in the HAZ (Heat Affected Zone) of the AISI 316L in two different temperatures (303 deg C and 325 deg C). The susceptibility to stress corrosion cracking was assessed using the slow strain rate tensile (SSRT) test. The results of the SSRT tests indicated that CST is a thermally-activated mechanism and that brittle fracture caused by the corrosion process was observed at 325 deg C). (author)

  1. Corrosion and low-cycle fatigue properties of AISI 316L in flowing Pb-17Li

    Corrosion and low-cycle fatigue (LCF) tests were performed on AISI 316L steel specimens in a flowing lithium lead environment. The LCF and corrosion tests were conducted simultaneously in the ''LIFUS 2'' forced convection loop, at a temperature of 723 K and a flow velocity of approximately 0.01 m/s. The LCF tests, which had a strain amplitude ranging from 0.008 to 0.016, were compared with reference tests performed in an inert argon atmosphere. The results show that liquid Pb-17Li has no detrimental effect on the LCF behaviour of 316L at the test temperature of 723 K. The corrosion tests extended from 650 to 1600 h with intermediate steps. Metallographic and SEM-EDAX analyses indicated the presence of an irregular porous ferritic layer. The results are discussed in terms of ferrite growth rate and the effect of corrosion phenomena on LCF behaviour. ((orig.))

  2. Effect of the purging gas on properties of Ti stabilized AISI 321 stainless steel TIG welds

    Taban, Emel; Kaluc, Erdinc; Aykan, T. Serkan [Kocaeli Univ. (Turkey). Dept. of Mechanical Engineering

    2014-07-01

    Gas purging is necessary to provide a high quality of stainless steel pipe welding in order to prevent oxidation of the weld zone inside the pipe. AISI 321 stabilized austenitic stainless steel pipes commonly preferred in refinery applications have been welded by the TIG welding process both with and without the use of purging gas. As purging gases, Ar, N{sub 2}, Ar + N{sub 2} and N{sub 2} + 10% H{sub 2} were used, respectively. The aim of this investigation is to detect the effect of purging gas on the weld joint properties such as microstructure, corrosion, strength and impact toughness. Macro sections and microstructures of the welds were investigated. Chemical composition analysis to obtain the nitrogen, oxygen and hydrogen content of the weld root was done by Leco analysis. Ferrite content of the beads including root and cap passes were measured by a ferritscope. Vickers hardness (HV10) values were obtained. Intergranular and pitting corrosion tests were applied to determine the corrosion resistance of all welds. Type of the purging gas affected pitting corrosion properties as well as the ferrite content and nitrogen, oxygen and hydrogen contents at the roots of the welds. Any hot cracking problems are not predicted as the weld still solidifies with ferrite in the primary phase as confirmed by microstructural and ferrite content analysis. Mechanical testing showed no significant change according to the purge gas. AISI 321 steel and 347 consumable compositions would permit use of nitrogen rich gases for root shielding without a risk of hot cracking.

  3. Investigating the correlation between some of the properties of plasma nitrided AISI 316L stainless steel

    M. Olzon-Dionysio

    2013-01-01

    Full Text Available When AISI 316L stainless steels are submitted to the nitriding process at temperatures lower than 450 °C, a high nitrogen content expanded austenite phase is formed, which shows higher hardness and higher pitting corrosion resistance compared to the untreated material. As a result, this material becomes adequate for biomedical application. The conditions of the nitriding technique, such as gas mixture, pressure, time and temperature, play an important role in some properties of the modified layer, including: thickness, hardness and N concentration along the layer. This paper explores a set of six samples of AISI 316L, nitrided at different times and temperatures, whose properties show important differences. The aim of this research is to investigate the correlation between the nitrided layer thickness (in the range of 0.77 to 11 µm with both X-ray patterns characteristics and hardness measurements, which used two distinct loads. The results of this study show that: whereas the 3.6 gf load was suitable to measure the real hardness for four of the nitrided layers showing thickness ≥ 2.9 µm, the 50 gf load measured a substrate contribution, probably even for the highest thickness, 11 µm. Moreover, analyzing different reflections of the X-ray patterns showed evidence of the clear consistency between the X-Ray depths and the nitrided layer thicknesses: if the layer thickness is lower than the penetration depth of X-rays, two phases (austenite and expanded substrate are present. If the layer thickness is higher, only the austenite is observed. Finally, concerning the citotoxicity property, all the samples, nitrided or not, were approved in the test for biocompatibility, indicating their potential use for biomedical applications.

  4. On The Enhancement of Wear Resistance of Hardened Carbon Tool Steel (AISI 1095) With Cryogenic Quenching

    V.Soundararajan; N.Alagurmurthi; K.Palaniradja

    2004-01-01

    Many experimental investigations reveal that it is very difficult to have a completely martensitic structure by any hardening process. Some amount of austenite is generally present in the hardened steel. This austenite existing along with martensite is normally referred as the retained austenite. The presence of retained austenite greatly reduces the mechanical properties and such steels do not develop maximum hardness even after cooling at rates higher than the critical cooling rates.Strength can be improved in hardened steels containing retained austenite by a process known as cryogenic quenching.Untransformed austenite is converted into martensite by this treatment. This conversion of retained austenite into martensite results in increased hardness, wear resistance and dimensional stability of steel. Wear can be defined as the progressive loss of materials from the operating surface of a body occurring as a result of relative motion at the surface. Hardness, load,speed, surface roughness, temperature are the major factors which influences wear. Many studies on wear indicate that increasing hardness decreases the wear of a material. With this in mind, to study the surface wear on a surface modified(Cryogenic treated) steel material an attempt has been made in this paper. In this study as a Part -I Hardening was carried out on carbon tool steel (AISI 1095) of different L/D ratio with conventional quenchants like purified water, aqueous solution and Hot mineral oil. As a Part -Ⅱ hardening was followed by quenching was carried out as said in Part- I and the hardened specimen were quenched in liquid Nitrogen which is at sub zero condition. The specimens were tested for its microstructure, hardness and wear loss. The results were compared and analyzed. The alloying elements increases the content of retained austenite hence the material used was AISI1095 (Carbon 0.9%, Si 0.2%, Mn0.4% and the rest Iron)

  5. Improving the empirical model for plasma nitrided AISI 316L corrosion resistance based on Moessbauer spectroscopy

    Campos, M.; Souza, S. D. de [Universidade Federal de Sao Carlos, Departamento de Fisica (Brazil); Souza, S. de [Instituto de Pesquisas Energeticas e Nucleares, Centro de Ciencia e Tecnologia de Materiais (Brazil); Olzon-Dionysio, M., E-mail: dmod@df.ufscar.br [Universidade Federal de Sao Carlos, Departamento de Fisica (Brazil)

    2011-11-15

    Traditional plasma nitriding treatments using temperatures ranging from approximately 650 to 730 K can improve wear, corrosion resistance and surface hardness on stainless steels. The nitrided layer consists of some iron nitrides: the cubic {gamma}{sup Prime} phase (Fe{sub 4}N), the hexagonal phase {epsilon} (Fe{sub 2 - 3}N) and a nitrogen supersatured solid phase {gamma}{sub N}. An empirical model is proposed to explain the corrosion resistance of AISI 316L and ASTM F138 nitrided samples based on Moessbauer Spectroscopy results: the larger the ratio between {epsilon} and {gamma}{sup Prime} phase fractions of the sample, the better its resistance corrosion is. In this work, this model is examined using some new results of AISI 316L samples, nitrided under the same previous conditions of gas composition and temperature, but at different pressure, for 3, 4 and 5 h. The sample nitrided for 4 h, whose value for {epsilon}/{gamma}{sup Prime} is maximum (= 0.73), shows a slightly better response than the other two samples, nitrided for 5 and 3 h ({epsilon}/{gamma}{sup Prime} = 0.72 and 0.59, respectively). Moreover, these samples show very similar behavior. Therefore, this set of samples was not suitable to test the empirical model. However, the comparison between the present results of potentiodynamic polarization curves and those obtained previously at 4 and 4.5 torr, could indicated that the corrosion resistance of the sample which only presents the {gamma}{sub N} phase was the worst of them. Moreover, the empirical model seems not to be ready to explain the response to corrosion and it should be improved including the {gamma}{sub N} phase.

  6. Production of nano/submicron grained AISI 304L stainless steel through the martensite reversion process

    Research highlights: → At least 50% reduction is necessary to complete the transformation of austenite to martensite at 0 deg. C. → The parameters of Olsen-Cohen model were found as n = 4.5, α = 3.257 and β = 3.573. → The appropriate grain refining zone for annealing treatment was determined. → A diagram showing different zones for each level of grain sizes via annealing conditions is presented. → The hardness improves 2.5 times higher after the thermo-mechanical process. → Final structure exhibits not only high strength (above 1 GPa) but also good elongation (∼40%). - Abstract: Production of nano/submicron grained AISI 304L austenitic stainless steel through formation of strain-induced martensite and its reversion to austenite are studied in this paper. The effects of annealing parameters on the microstructural development and mechanical properties are also investigated. Heavily cold rolling at 0 deg. C is employed to induce the formation of martensite in the metastable austenitic material, followed by reversion treatment at the temperature range of 700-900 deg. C for 0.5-300 min. Microstructural evolutions are analyzed using Feritscope, X-ray diffraction, and scanning electron microscopy, whereas the mechanical properties are determined by hardness and tensile tests. The smallest grain size (about 135 nm) is obtained in the specimen annealed at 700 deg. C for 20 min. The resultant nano/submicron grained steel not only exhibits a high strength level (about 1010 MPa) but also a desirable elongation of about 40%. Moreover, an annealing map is developed which indicates the appropriate range of annealing parameters for grain refinement of AISI 304L stainless steel through the martensite reversion process.

  7. Production of nano/submicron grained AISI 304L stainless steel through the martensite reversion process

    Forouzan, Farnoosh, E-mail: forouzan.iut@gmail.com [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Najafizadeh, Abbas; Kermanpur, Ahmad; Hedayati, Ali; Surkialiabad, Roohallah [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2010-10-25

    Research highlights: {yields} At least 50% reduction is necessary to complete the transformation of austenite to martensite at 0 deg. C. {yields} The parameters of Olsen-Cohen model were found as n = 4.5, {alpha} = 3.257 and {beta} = 3.573. {yields} The appropriate grain refining zone for annealing treatment was determined. {yields} A diagram showing different zones for each level of grain sizes via annealing conditions is presented. {yields} The hardness improves 2.5 times higher after the thermo-mechanical process. {yields} Final structure exhibits not only high strength (above 1 GPa) but also good elongation ({approx}40%). - Abstract: Production of nano/submicron grained AISI 304L austenitic stainless steel through formation of strain-induced martensite and its reversion to austenite are studied in this paper. The effects of annealing parameters on the microstructural development and mechanical properties are also investigated. Heavily cold rolling at 0 deg. C is employed to induce the formation of martensite in the metastable austenitic material, followed by reversion treatment at the temperature range of 700-900 deg. C for 0.5-300 min. Microstructural evolutions are analyzed using Feritscope, X-ray diffraction, and scanning electron microscopy, whereas the mechanical properties are determined by hardness and tensile tests. The smallest grain size (about 135 nm) is obtained in the specimen annealed at 700 deg. C for 20 min. The resultant nano/submicron grained steel not only exhibits a high strength level (about 1010 MPa) but also a desirable elongation of about 40%. Moreover, an annealing map is developed which indicates the appropriate range of annealing parameters for grain refinement of AISI 304L stainless steel through the martensite reversion process.

  8. Wear of plasma nitrided and nitrocarburized AISI 316L austenitic stainless steel

    F.A.P. Fernandes

    2010-06-01

    Full Text Available Purpose: the purpose of the work is to compare the wear resistance, in dry and lubricated conditions, of AISI 316L austenitic stainless steel samples that were plasma nitrided or nitrocarburized at 450°C for 5 and 10 h, respectively.Design/methodology/approach: Hardness and wear resistance of austenitic stainless steel can be increased substantially, without losing corrosion resistance, by plasma nitriding or nitrocarburizing surface treatments. In this work, AISI 316L austenitic stainless steel was plasma nitrided and nitrocarburized at 450°C, for 5 and 10 h respectively.Findings: The obtained layers were characterized by optical microscopy, X-ray diffraction, microhardness and micro-wear tests in dry and lubricated conditions. Optical microscopy and X-ray diffraction analysis demonstrated that the nitrided layer is homogeneous and primarily composed of nitrogen rich expanded austenite with a thickness of about 15 µm. Nitrocarburized samples exhibited an external layer of chromium and iron compounds and a sub-layer of expanded austenite with a total thickness of 45 µm. Microhardness profiles showed that the hardness near to the surface was close to 1100 HV for nitriding and 1300 HV for nitrocarburizing. Plasma nitrided and nitrocarburized layers exhibited substantial wear reduction in dry and lubricated test conditions. The use of a lubricant oil reduces wear by a factor of approximately 200 compared to the dry test results.Research limitations/implications: The plasma nitrided layer yielded the best wear performance in both dry and lubricated conditions.Originality/value: Plasma nitriding resulted in the best wear performance when compared with nitrocarburizing in dry and lubricated sliding which is probably due to reduced layer fragility.

  9. Microstructure and mechanical properties of friction stir processed AISI 316L stainless steel

    Highlights: • FSP can be used to produce bulk ultrafine grained structures in AISI 316L SS. • The main mechanism for grain structure refinement of FSP 316L SS is DDRX. • However, some evidences of CDRX and SRX were also observed. • The material flow was found to be near simple shear deformation (A/A‾ and C). • FSP samples have an enhanced hardness and strength compared with the base metal. - Abstract: Friction stir processing was used to refine the grain structure in 2 mm thick AISI 316L stainless steel sheets, with a pinless tool, at a constant traverse speed of 63 mm/min and relatively low rotational speeds of 200 and 315 rpm. Depending on the processing conditions, the initial grain size of 14.8 μm in the base metal was subsequently decreased to 0.8–2.2 μm in the processed areas. The microstructural characterizations by orientation imaging and transmission electron microscopy revealed that the grain structure evolution in the stir zone is primarily dominated by discontinuous dynamic recrystallization. The material flow was found to be near simple shear deformation and the developed textures were composed of a mixture of A/A‾ and C components of ideal simple shear textures. The mechanical properties were also evaluated by the longitudinal tensile tests and microhardness measurements. The obtained results showed that, despite a 50% decrease in ductility, the highest yield and ultimate tensile strength of the friction stir processed samples are respectively about 1.6 and 1.2 times higher than those of the base metal. In good agreement with the tensile properties, the increased hardness of the stir zone was attributed to the grain structure refinement

  10. Action of an aerobic hydrogenotroph bacteria isolated from ultrapure water systems on AISI 304 stainless steel

    Several microbial studies have been recently performed in nuclear power stations. These studies concerned essentially the formation of bio-films on submerged metal coupons. Heterotrophic micro-organisms have been found in bulk water of nuclear fuel storage basins but the in situ nutrient sources for bacterial development in such highly oligo-trophic water was unknown. In nuclear environments, radiations lead to the production of molecular hydrogen, hydrogen peroxide and some radicals (OH, O2-) by radiolysis of water or embedding matrices. Bacterial oxidation of molecular H2 commonly occurs in nature, as molecular hydrogen represents a high-energy reductant. We investigated the microbiology of a ultra-pure water basin containing irradiating waste. The initial aim of this study was to determine if autotrophic bacterial growth was possible in this basin. A major bacteria was isolated (Ralstonia sp. GGLH002) which was able to grow autotrophically with hydrogen as the electron donor and oxygen as the electron acceptor, and heterotrophically with organic nutrients. Its hydrogenase activity has been characterized. We focused then our study on the effects of this strain on 304L AISI stainless steel depending on the nutrient source used for bacterial development, e.g hydrogen or organics. In conclusion, the mechanism of passivation enhanced by Ralstonia sp. GGLH002 on AISI 304L SS still remains unknown. Several techniques could give substantial information, including XPS and polarization curves. It seems for the moment that the major bacteria inhabiting an oxic environment containing hydrogen due to radiolysis is not aggressive to stainless steel in conditions near from its environment. Further investigations are needed to test this hypothesis, including a study of the molecular diversity of the bacteria using culture-independent techniques, as cultivatable bacterial populations represent in general only a fraction of the total bacteria. (authors)

  11. Dislocation structure evolution and its effects on cyclic deformation response of AISI 316L stainless steel

    Research highlights: → The cyclic deformation response of AISI 316L steel is investigated at 20 deg. C. → The corresponding microstructure evolution is characterised by electron microscopy. → A 3D representation of dislocation evolution is proposed based on the observation. → The 3D representation gives a good explanation of the microstructure complexity. → The cyclic deformation response is discussed based on the microstructure evolution. - Abstract: The cyclic deformation response of an austenitic stainless steel is characterised in terms of its cyclic peak tensile stress properties by three stages of behaviour: a hardening stage followed by a softening stage, and finally a stable stress response stage. A series of tests have been performed and interrupted at selected numbers of cycles in the different stages of mechanical response. At each interruption point, specimens have been examined by transmission electron microscopy (TEM) with different beam directions by means of the tilting function in order to investigate the formation and the development of dislocation structures from the as-received condition until the end of fatigue life. A new 3D representation of dislocation structure evolution during cyclic loading is proposed on the basis of the microstructural observations. The 3D representation provides a deeper insight into the development of dislocation structures in AISI 316L during low cycle fatigue loading at room temperature. By investigating the dislocation evolution, the study shows that the hardening response is mainly associated with an increase of total dislocation density, whereas the softening stage is a result of the formation of dislocation-free regions. Further development of the dislocation structure into a cellular structure is responsible for the stable stress response stage.

  12. Tribological Properties of Nanometric Atomic Layer Depositions Applied on AISI 420 Stainless Steel

    E. Marin

    2013-09-01

    Full Text Available Atomic Layer Deposition ( ALD is a modern technique that Allows to deposit nanometric, conformal coatings on almost any kind of substrates, from plastics to ceramic, metals or even composites. ALD coatings are not dependent on the morphology of the substrate and are only regulated by the composition of the precursors, the chamber temperature and the number of cycles. In this work, mono- and bi -layer nanometric, protective low-temperature ALD Coatings, based on Al2O3 and TiO2 were applied on AISI 420 Stainless Steel in orderto enhance its relatively low corrosion resistance in chloride containing environments. Tribological testing were also performed on the ALD coated AISI 420 in order to evaluate the wear and scratch resistance of these nanometric layers and thus evaluate their durability. Scratch tests were performed using a standard Rockwell C indenter, under a variable load condition, in order to evaluate the critical loading condition for each coating. Wear testing were performed using a stainless steel counterpart, in ball-on-discconfiguration, in order to measure the friction coefficient and wear to confront the resistance. All scratch tests scars and wear tracks were then observed by means of Scanning Electron Microscopy (SEM in order to understand the wear mechanisms that occurred on the sample surfaces. Corrosion testing, performed under immersion in 0.2 M NaCl solutions, clearly showed that the ALD coatings have a strong effect in protecting the Stainless Steel Substrate against corrosion, reducing the corrosion current density by two orders of magnitude.Tribological The preliminary results showed that ALD depositions obtained at low Temperatures have a brittle behavior caused by the amorphous nature of their structure, and thus undergo delamination phenomena during Scratch Testing at relatively low applied loads. During ball-on-disc testing, the coatings were removed from the substrate, in particular for monolayer ALD configurations

  13. Effective Duration of Gas Nitriding Process on AISI 316L for the Formation of a Desired Thickness of Surface Nitrided Layer

    Mahmoud Hassan R. S.; Yusoff Syafiq A.; Zainuddin Azman; Hussain Patthi; Ismail Mokhtar; Abidin Kamal

    2014-01-01

    High temperature gas nitriding performed on AISI 316L at the temperature of 1200°C. The microstructure of treated AISI 316L samples were observed to identify the formation of the microstructure of nitrided surface layer. The grain size of austenite tends to be enlarged when the nitriding time increases, but the austenite single phase structure is maintained even after the long-time solution nitriding. Using microhardness testing, the hardness values drop to the center of the samples. The incr...

  14. Achados oftalmológicos em pacientes que receberam transplante cardíaco Ophthalmologic findings in cardiac transplant recipients

    Cecília Sales Pires

    2007-10-01

    Full Text Available OBJETIVO: Avaliar os achados oculares, pelo exame oftalmológico, em indivíduos que receberam transplante cardíaco, buscando especialmente investigar possíveis alterações na camada de fibras nervosas da retina com polarímetro de varredura a laser. MÉTODOS: Foram estudados 15 indivíduos que receberam transplante cardíaco no período de setembro de 2003 a julho de 2004. Todos foram submetidos a exame que constava de acuidade visual para longe (AVL, biomicroscopia, tonometria e fundoscopia. Onze pacientes foram submetidos ao analisador de fibras nervosas GDx. Doze eram do sexo masculino e a média da idade foi de 55,0 ± 13,5 anos. O tempo decorrido desde o transplante variou de 3 a 74 meses, com média de 29,7 ± 20,8 meses. RESULTADOS: A AVL com melhor correção foi igual ou melhor do que 20/40 em todos os pacientes. Em um deles observou-se a presença de catarata subcapsular posterior; em outro, nubéculas na córnea secundárias a quadro de herpes zoster. À fundoscopia pôde-se observar lesão cicatrizada sugestiva de retinocoroidite em um paciente. As alterações observadas à biomicroscopia e à fundoscopia eram esperadas devido à imunossupressão subseqüente ao transplante. Ao GDx observou-se perda de fibras da camada de fibras nervosas da retina superior em 12 dos 22 olhos avaliados. CONCLUSÃO: Os resultados apóiam a suposição de que antes ou durante o transplante cardíaco tenha havido diminuição no aporte de oxigênio à circulação retiniana, levando a perda parcial de fibras da retina.PURPOSE: To evaluate findings of ophthalmologic examinations in cardiac transplant recipients, searching especially for changes in the retinal nerve fiber layer by means of Scanning Laser Polarimetry. METHODS: Fifteen cardiac transplant recipients were examined from September 2003 to July 2004. All of them underwent ophthalmologic examination, which consisted of visual acuity (VA, biomicroscopy, tonometry and fundoscopy. Fiber layer

  15. El calcio en los miocitos cardíacos y su papel en las miocardiopatías.

    Guido Ulate Montero

    2006-01-01

    Full Text Available El papel que desempeña el calcio en los miocitos cardíacos abarca un gran número de funciones, desde su rol en el acoplamiento excitación-ccontracción hasta su papel de segundo mensajero en las diversas vías de señalización, algunas de las cuales se activan en procesos que afectan la integridad del tejido miocárdico y que tienen que ver con el crecimiento y la apoptosis de los miocitos y que al final, son los que determinan la evolución de la mayoría de las cardiomiopatías. En esta revisión se abordan los mecanismos fisiológicos en las células de músculo cardíaco en los que este ión juega un papel determinante y los cambios que se presentan en ciertas cardiopatías como la miocardiopatía arritmogénica del ventrículo derecho, las miocardiopatías asociadas a alteraciones en el receptor de rianodina y la miocardiopatía dilatada. Se revisa también la farmacodinamia de los agentes inotrópicos positivos que actúan sensibilizando los miofilamentos del sarcómero al calcio.The rol played by calcium in cardiomyocytes includes a great number of functions like the excitation-contraction coupling as well as a second messenger in diverse signaling pathways. Some of these pathways are activated in processes that affect the cardiac tissue integrity and also participate in cell growth and apoptosis, determining the poor prognosis that characterize the majority of the cardiomyopathies. In this review,the mechanisms inside the cardiomyocytes in which participates calcium and the pathophysiological changes observed in some cardiac diseases like arrhythmogenic right ventricular cardiomyopathy, catecholaminergic polymorphic ventricular tachycardia, idiopathic dilated cardiomyopathy, and others, are described. The action mechanism of positive inotropic drugs that act as sarcomere myofilaments sensitizers is also reviewed.

  16. Sildenafil vs. Nitroprussiato de Sódio durante Teste de Reatividade Pulmonar pré-transplante cardíaco

    Aguinaldo Figueiredo Freitas Jr

    2012-09-01

    Full Text Available FUNDAMENTO: A hipertensão pulmonar é associada ao pior prognóstico no pós-transplante cardíaco. O teste de reatividade pulmonar com Nitroprussiato de Sódio (NPS está associado a elevados índices de hipotensão arterial sistêmica, disfunção ventricular do enxerto transplantado e elevadas taxas de desqualificação para o transplante. OBJETIVO: Neste estudo, objetivou-se comparar os efeitos do Sildenafil (SIL e NPS sobre variáveis hemodinâmicas, neuro-hormonais e ecocardiográficas durante teste de reatividade pulmonar. MÉTODOS: Os pacientes foram submetidos, simultaneamente, ao cateterismo cardíaco direito, ao ecocardiograma e à dosagem de BNP e gasometria venosa, antes e após administração de NPS (1 - 2 µg/Kg/min ou SIL (100 mg, dose única. RESULTADOS: Ambos reduziram a hipertensão pulmonar, porém o nitrato promoveu hipotensão sistêmica significativa (Pressão Arterial Média - PAM: 85,2 vs. 69,8 mmHg, p < 0,001. Ambos reduziram as dimensões cardíacas e melhoraram a função cardíaca esquerda (NPS: 23,5 vs. 24,8 %, p = 0,02; SIL: 23,8 vs. 26 %, p < 0,001 e direita (SIL: 6,57 ± 2,08 vs. 8,11 ± 1,81 cm/s, p = 0,002; NPS: 6,64 ± 1,51 vs. 7,72 ± 1,44 cm/s, p = 0,003, medidas pela fração de ejeção ventricular esquerda e Doppler tecidual, respectivamente. O SIL, ao contrário do NPS, apresentou melhora no índice de saturação venosa de oxigênio, medido pela gasometria venosa. CONCLUSÃO: Sildenafil e NPS são vasodilatadores que reduzem, de forma significativa, a hipertensão pulmonar e a geometria cardíaca, além de melhorar a função biventricular. O NPS, ao contrário do SIL, esteve associado a hipotensão arterial sistêmica e piora da saturação venosa de oxigênio.

  17. Determinación de tensiones por rayos x del acero AISI 1045 deformado por rodillo // Determination of stress for x‐ray of the steel AISI 1045 deformed for roller

    Tomás Fernández‐Columbié

    2012-01-01

    Full Text Available El objetivo del trabajo es realizar el análisis de las tensiones a muestras de acero AISI 1045 endurecidasen frío por rodillo. Con empleo del método de Willianson–Hall se determinó las macro ymicrodeformaciones; la deformación reticular del parámetro de red; el tamaño de las cristalitas; losesfuerzos en la red cristalina y la reducción del tamaño promedio de los granos, lo que permitió establecerlos mecanismos de endurecimiento del acero AISI 1045, deformado por rodadura. Fueron medidos yanalizados diferentes puntos teniendo en cuenta los índices de Miller para la fase ferrítica del acero. Losmodelos lineales obtenidos, son estadísticamente significativos, que muestran una tendencia creciente delas propiedades mecánicas y metalúrgicas, según se incrementan las variables independientes delproceso de experimentación.Palabras claves: rodillo, rodadura, deformación plástica.__________________________________________________________________AbstractThe objective of the paper is to carry out the analysis from the tensions to steel samples AISI 1045hardened cold for roller. With employment of the method of Willianson-Hall was determined the macro andmicro deformations; the reticular deformation of the net parameter; the size of the crystallites; the efforts inthe crystalline net and the reduction of the size average of the grains, what allowed to establish themechanisms of hardening of the steel AISI 1045, deformed by rolling. They were measured and analyzeddifferent points keeping in mind the indexes of Miller for the phase ferrite of the steel. The obtained linealmodels, they are statistically significant that they show a growing tendency of the mechanical estates andmetallurgical, as the independent variables of the experimentation process are increased.Key words: roller, rolling, plastic deformation.

  18. Evaluación del comportamiento a fatiga de una unión soldada a tope de acero AISI 1015//Evaluation of the fatigue behaviour of a butt welded joint of AISI 1015 steel

    Pavel Michel Almaguer‐Zaldivar

    2015-01-01

    Full Text Available Las uniones soldadas son un componente importante de una estructura, por lo que siempre es necesario conocer la respuesta de las mismas sometidas a cargas cíclicas. El objetivo de este trabajo es obtener la curva S-N de una unión soldada a tope de acero AISI 1015 y electrodo E6013 como material de aporte. Los ensayos a fatiga se realizaron de acuerdo a la norma ASTM en una máquina universal MTS810. Se utilizaron probetas de sección rectangular. El ciclo de carga fueasimétrico a tracción, con un coeficiente de asimetría de 0,1. Se obtuvo que la unión estudiada tiene un límite de resistencia a la fatiga de 178 MPa, a un punto de corte de 2 039 093 ciclos.Palabras claves: unión soldada, fatiga, curva S-N, AISI 1015, electrodo E6013._______________________________________________________________________________AbstractWelded joints are an important component in structures, by this reason is necessary to know the behaviour of these elements under cyclic loads. The objective of this work is to obtain the S-N curve of the butt welded joint of AISI 1015 steel and electrode E6013 as the contribution material. Fatiguetest was realized within the ASTM standard in the MTS810 testing machine. Rectangular cross section specimens was used. Cyclic loads was asymmetric tensile and the asymmetry ratio used was 0,1. In this study was obtained the fatigue limit equal to 178 MPa, at the cut point of 2 039 093 cycles.Key words: welded joint, fatigue, S-N curve, AISI 1015 steel, electrode E6013.

  19. L’intelligence collective dans un contexte de développement professionnel continu : ACoPé, l’exemple d’une communauté de pratique

    Pichon, Aude; Morel, Alexandre; Gassie, Brigitte; Vandenkoornhuyse, Christine; Delalande, Pascaline

    2015-01-01

    Cooperating with a view to furthering professional development, taking decisions and functioning interoperatively within a community implies working with participants committed to fostering strong relationships, reflective practice, and reaching shared understanding.The collaboration between the ACoPé educational advisors takes place within this context itself part of the wider framework of a higher education environment with intersectoral, interprofessional, interdisciplinary and inter-regio...

  20. Acute Care of At-Risk Newborns (ACoRN: quantitative and qualitative educational evaluation of the program in a region of China

    Singhal Nalini

    2012-06-01

    Full Text Available Abstract Background The Acute Care of at-Risk Newborns (ACoRN program was developed in Canada for trained health care providers for the identification and management of newborns who are at-risk and/or become unwell in the first few hours or days after birth. The ACoRN process follows an 8-step framework that enables the evaluation and management of babies irrespective of the experience or expertise of the caregiving individual or team. This study assesses the applicability of the program to Chinese pediatric practitioners. Methods Course content and educational materials were translated from English into Chinese by bilingual neonatal practitioners. Confidence and knowledge questionnaires were developed and reviewed for face and content validity by a team of ACoRN instructors. Bilingual Chinese instructors were trained at the tertiary perinatal centre in Hangzhou Zhejiang to deliver the course at 15 level II county hospitals. Participants completed pre- and post-course confidence and knowledge questionnaires and provided feedback through post-course focus groups. Results 216 physicians and nurses were trained. Confidence and knowledge relating to neonatal stabilization improved significantly following the courses. Participants rated course utility and function between 4.2 and 4.6/5 on all items. Pre/post measures of confidence were significantly correlated with post course knowledge. Focus group data supported the perceived value of the program and recommended course adjustments to include pre-course reading, and increased content related to simulation, communication skills, and management of respiratory illness and jaundice. Conclusions ACoRN, a Canadian educational program, appears to be well received by Chinese health care providers and results in improved knowledge and confidence. International program adaptation for use by health care professionals requires structured and systematic evaluation to ensure that the program meets the needs of

  1. Effect of cerium and lanthanum on the microstructure and mechanical properties of AISI D2 tool steel

    Hamidzadeh, Mohammad Ali, E-mail: mahamidzadeh@yahoo.com [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Meratian, Mahmood; Saatchi, Ahmad [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2013-06-01

    AISI D2 tool steel has excellent wear resistance with high dimensional stability. This type of steel is suitable for making molds. This paper describes investigations into the effect of adding Ce/La on microstructure of AISI D2 type cold work tool steels obtained by means of optical microscopy, scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectrometry (EDS) and image analyzer. The results showed that after modification with Ce/La, the morphology, size and distribution of M{sub 7}C{sub 3} carbides change greatly. The carbide network tends to break, and all carbides are refined and distributed homogeneously in the matrix, and also reduce the size of chromium carbides and increase the dissolution of carbides during heat treatment. The results of mechanical tests show that the toughness of the alloy increased about 75% without reducing the hardness of the alloy.

  2. Effect of cerium and lanthanum on the microstructure and mechanical properties of AISI D2 tool steel

    AISI D2 tool steel has excellent wear resistance with high dimensional stability. This type of steel is suitable for making molds. This paper describes investigations into the effect of adding Ce/La on microstructure of AISI D2 type cold work tool steels obtained by means of optical microscopy, scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectrometry (EDS) and image analyzer. The results showed that after modification with Ce/La, the morphology, size and distribution of M7C3 carbides change greatly. The carbide network tends to break, and all carbides are refined and distributed homogeneously in the matrix, and also reduce the size of chromium carbides and increase the dissolution of carbides during heat treatment. The results of mechanical tests show that the toughness of the alloy increased about 75% without reducing the hardness of the alloy

  3. EFFECTS OF CARBURIZING AND NITRIDING PROCESSES ON THE COST AND QUALITY OF GEARS PRODUCED WITH AISI 4140 AND 8620 STEELS

    Claudio José Leitão

    2012-09-01

    Full Text Available This study compares the effects of nitriding and carburizing processes applied to gears subjected to contact stresses below 1300 MPa. The manufacturing cost, as well the depth of hardened layer and the distortion produced by two processes are analyzed. AISI 4140 gears quenched, tempered, liquid and gas nitriding and AISI 8620 gears after liquid carburizing, quenching and tempering are analyzed. The dimensional control of the gears was carried out before and after heat and thermochemical treatments. It is concluded that liquid or gas nitriding processes are about 30% more economical than liquid carburizing an also they reduce the dimensional changes. By the other hand liquid carburizing achieves greater case depth. Liquid nitriding process presents the lowest cost, dimensional changes and case depth.

  4. Mathematical Modelling of Nitride Layer Growth of Low Temperature Gas and Plasma Nitriding of AISI 316L

    Triwiyanto A.

    2014-07-01

    Full Text Available This paper present mathematical model which developed to predict the nitrided layer thickness (case depth of gas nitrided and plasma nitrided austenitic stainless steel according to Fick’s first law for pure iron by adapting and manipulating the Hosseini’s model to fit the diffusion mechanism where nitrided structure formed by nitrided AISI 316L austenitic stainless steel. The mathematical model later tested against various actual gas nitriding and plasma nitriding experimental results with varying nitriding temperature and nitriding duration to see whether the model managed to successfully predict the nitrided layer thickness. This model predicted the coexistence of ε-Fe2-3N and γ΄-Fe4N under the present nitriding process parameters. After the validation process, it is proven that the mathematical model managed to predict the nitrided layer growth of the gas nitrided and plasma nitrided of AISI 316L SS up to high degree of accuracy.

  5. Analysis of a premature failure of welded AISI316L stainless steel pipes originated by microbial induced corrosion

    Otero, E.; Bastidas, J.M.; Lopez, V. [Centro Nacional de Investigaciones Metalurgicas, Madrid (Spain)

    1997-07-01

    This paper analyses the causes of the premature failure of welded AISI 316L stainless steel (ss) pipes which formed part of a sea water cooling circuit. The service time of the pipes was 8 months. The laboratory tests carried out consisted of metallography tests, {delta}-ferrite determination, intergranular corrosion susceptibility, cyclic anodic polarization curves, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray photo-electron spectroscopy (XPS). The study presents typical forms of microbial induced corrosion (MIC) in AISI 308L and 316L ss in contact with natural sea water. The research is completed with the performance of bacteriological tests which demonstrate that the bacteria which cause the localized corrosion are of the sulphate-reducing genus ``desulfovibrio`` and the sulphide-oxidizing genus ``thiocapsa``. (orig.) 17 refs.

  6. Study the influence of a new ball burnishing technique on the surface roughness of AISI 1018 low carbon steel

    Abd Alkader Ibrahim

    2015-02-01

    Full Text Available Hard roller burnishing with a ball tool is a surface-finishing where a free-rotating tool rolls over the machined surface under high pressures and flattens the surface roughness peaks by cold work. In the present work, a new burnishing technique has been applied which enables both single and double ball burnishing process in site after turning without releasing the specimen. Sets of experiments are conducted to investigate the influence of burnishing force, feed, speed and number of tool passes on surface roughness of AISI 1018 Low Carbon Steel specimens. Burnishing results showed significant effectiveness of the new burnishing technique in the process. The results revealed that minimum surface roughness are obtained by applying the double ball burnishing process on AISI 1018 Low Carbon Steel specimens. Improvement in surface finish can be achieved in both single and double ball burnishing by increasing the number of burnishing tool passes. The results are presented in this paper.

  7. Corrosion behavior of plasma sprayed hydroxyapatite and hydroxyapatite-silicon oxide coatings on AISI 304 for biomedical application

    The objective of this study is to evaluate corrosion resistance of plasma sprayed hydroxyapatite (HA) and HA-silicon oxide (SiO2) coated AISI 304 substrates. In HA-SiO2 coatings, 10 wt% SiO2 and 20 wt% SiO2 was mixed with HA. The feedstock and coatings were characterized by X-ray diffraction and scanning electron microscopy/energy dispersive X-ray spectroscopy. The corrosion resistance was determined for the uncoated and coated samples. The corrosion resistance of the AISI 304 was found more after the deposition of the HA-SiO2 coatings rather than HA coating and uncoated. All the coatings were crack free after 24 h dipping in Ringer's solution for electrochemical corrosion testing.

  8. LaCrO3 composite coatings for AISI 444 stainless steel solid oxide fuel cell interconnects

    Wilson Acchar

    2012-12-01

    Full Text Available Doped lanthanum chromite-based ceramics are the most widely used interconnector material in solid fuel cells (SOFC since they exhibit significant electrical and thermal conductivity, substantial corrosion resistance and adequate mechanical strength at ambient and high temperatures. The disadvantage of this material is its high cost and poor ductility. The aim of this study is to determine the mechanical and oxidation behavior of a stainless steel (AISI 444 with a LaCrO3 deposition on its surface obtained through spray pyrolisis. Coated and pure AISI 444 materials were characterized by mechanical properties, oxidation behavior, X-ray diffraction and scanning electronic microscopy. Results indicated that the coated material displays better oxidation behavior in comparison to pure stainless steel, but no improvement in mechanical strength. Both materials indicate that deformation behavior depends on testing temperatures.

  9. Corrosion behavior of plasma sprayed hydroxyapatite and hydroxyapatite-silicon oxide coatings on AISI 304 for biomedical application

    Singh, Gurpreet, E-mail: gurpreetsnabha@yahoo.com [University College of Engineering, Punjabi University, Patiala, Punjab (India); Singh, Hazoor [Yadavindra College of Engineering, Punjabi University G.K. Campus, Talwandi Sabo, Punjab (India); Sidhu, Buta Singh [Punjab Technical University, Jalandhar, Punjab (India)

    2013-11-01

    The objective of this study is to evaluate corrosion resistance of plasma sprayed hydroxyapatite (HA) and HA-silicon oxide (SiO{sub 2}) coated AISI 304 substrates. In HA-SiO{sub 2} coatings, 10 wt% SiO{sub 2} and 20 wt% SiO{sub 2} was mixed with HA. The feedstock and coatings were characterized by X-ray diffraction and scanning electron microscopy/energy dispersive X-ray spectroscopy. The corrosion resistance was determined for the uncoated and coated samples. The corrosion resistance of the AISI 304 was found more after the deposition of the HA-SiO{sub 2} coatings rather than HA coating and uncoated. All the coatings were crack free after 24 h dipping in Ringer's solution for electrochemical corrosion testing.

  10. Sliding wear of steels (used in polished rods of oil pump jack) against polyurethane; Desgaste de deslizamento de acos (usados em hastes de unidade de bombeio de petroleo) contra poliuretano

    Gois, Gelsoneide da Silva [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Engenharia de Materiais; Farias, Aline Cristina Mendes; Lima da Silva, Ruthilene Catarina; Medeiros, Joao Telesforo Nobrega [Universidade Federal do Rio Grande do Norte (PPGEM/UFRN), Natal, RN (Brazil). Programa de Pos-Graduacao em Engenharia de Materiais], e-mail: gelsoneidegg@yahoo.com.br, e-mail: alineastro@yahoo.com.br, e-mail: ruthilene@ufrnet.br, e-mail: medeirosj2@asme.org

    2008-07-01

    Accelerated sliding tests were carried out in the steels AISI 316, AISI 4140, AISI 1045 coated and AISI 4142 coated, in the dry and lubricated with contaminated oil with 10% SiO{sub 2} conditions. Each cylindrical counterbody with angular generatrix of polyurethane slid against a stationary metallic specimen. The contact pressure changed by increment of normal loads of 10,0 and 2,3 N, velocity of 0,91 m/s and distance of 12 km. The wear rates were calculated through of the mass variation from specimens after each test. The wear morphology was characterized by Optical and Scanning Electron Microscopy, where identified damages by abrasion at two and three bodies. The contaminated lubricant increase the wear rate due to action of the abrasive particles. (author)

  11. Kajian Sub – Permukaan Baja Paduan Kekerasan Tinggi AISI 4140 Hasil Pembubutan Laju Tinggi Dan Kering Menggunakan Pahat CBN

    Siahaan, Enzo Wiranta Battra

    2012-01-01

    The integrity of the sub - surface plays an important role in product quality. In this study, the impact of rate cuts, feed motion, depth of cut, cutting tool wear and tear on the sub - surface machining of steel AISI 4140 on the end for high speed machining, hard machining and dry machining studied experimentally using CBN cutting tool material. Four test parameters with three levels of cutting speed is low, medium and high. Conducted the data analysis of quantitative and qualitative. Quanti...

  12. Modifications on the behaviour of AISI 304 stainless steel submitted to creep caused by intermediate treatment of annealing

    Type AISI 304 austenitic stainless steel samples which have been previously creep deformed at 7500C, were annealed at 11000C. The effects of this heat treatment in the mechanical behavior of this material when retested in creep were investigated. The results were analysed by taking into account the structural modifications observed and the controlling mechanisms which operate during the deformation and fracture occurring in the creep process. (Author)

  13. The silica-titania layer deposited by sol-gel method on the AISI 316L for contact with blood

    W. Walke

    2013-02-01

    Full Text Available Purpose: The study analyses influence of surface modification of Si:Ti on physical and chemical properties of samples made from AISI 316L steel in solution simulating blood-vascular system.Design/methodology/approach: Sol-gel layer was selected on the ground of data from literature. TEOS and TET made the ground for initial solution. Application of the layer on the surface of samples made of AISI 316L steel was preceded by mechanical working - grinding (Ra = 0.40 µm and mechanical polishing (Ra = 0.12 µm. Corrosion resistance tests were performed on the ground of registered anodic polarisation curves and Stern method. In order to evaluate phenomena that take place on the surface of the tested alloys EIS was also applied. The tests were performed in artificial blood plasma at the temperature of T = 37.0±1°C and pH = 7.0±0.2.Findings: Obtained results on the ground of voltammetric and impedance tests showed differentiated electrochemical properties of AISI 316L steel depending on the type of surface treatment. Practical implications: Suggested subject matter of the article supports development of entrepreneurship sector due to high social demand for this type of technologies and relatively easy way of putting obtained laboratory tests data into inductrial and clinical practice.Originality/value: Suggestion of proper variants of surface treatment with application of sol-gel method is meaningful in future perspective and it shall promote determination of technological conditions with precise parameters of creation of oxide layers on metallic implants made of AISI 316L steel that come into contact with blood.

  14. In-situ investigation of martensite formation in AISI 52100 bearing steel at sub-zero Celsius temperature

    Villa, Matteo; Hansen, Mikkel Fougt; Pantleon, Karen;

    2013-01-01

    Martensite formation in AISI 52100 bearing steel at sub-zero Celsius temperature was investigated with Vibrating Sample Magnetometry. The investigation reports the stabilization of retained austenite in quenched samples during storage at room temperature and reveals the thermally activated nature...... of the martensitic transformation. The kinetics of the transformation is interpreted in terms of a-thermal nucleation and thermally activated growth of lenticular martensite....

  15. In-situ investigation of martensite formation in AISI 52100 bearing steel at sub-zero Celsius temperature

    Villa, Matteo; Hansen, Mikkel Fougt; Pantleon, Karen; Somers, Marcel A. J.

    2013-01-01

    Martensite formation in AISI 52100 bearing steel at sub-zero Celsius temperature was investigated with Vibrating Sample Magnetometry. The investigation reports the stabilization of retained austenite in quenched samples during storage at room temperature and reveals the thermally activated nature of the martensitic transformation. The kinetics of the transformation is interpreted in terms of a-thermal nucleation and thermally activated growth of lenticular martensite.

  16. Microstructure and Mechanical Properties of Laser Clad and Post-cladding Tempered AISI H13 Tool Steel

    Telasang, Gururaj; Dutta Majumdar, Jyotsna; Wasekar, Nitin; Padmanabham, G.; Manna, Indranil

    2015-05-01

    This study reports a detailed investigation of the microstructure and mechanical properties (wear resistance and tensile strength) of hardened and tempered AISI H13 tool steel substrate following laser cladding with AISI H13 tool steel powder in as-clad and after post-cladding conventional bulk isothermal tempering [at 823 K (550 °C) for 2 hours] heat treatment. Laser cladding was carried out on AISI H13 tool steel substrate using a 6 kW continuous wave diode laser coupled with fiber delivering an energy density of 133 J/mm2 and equipped with a co-axial powder feeding nozzle capable of feeding powder at the rate of 13.3 × 10-3 g/mm2. Laser clad zone comprises martensite, retained austenite, and carbides, and measures an average hardness of 600 to 650 VHN. Subsequent isothermal tempering converted the microstructure into one with tempered martensite and uniform dispersion of carbides with a hardness of 550 to 650 VHN. Interestingly, laser cladding introduced residual compressive stress of 670 ± 15 MPa, which reduces to 580 ± 20 MPa following isothermal tempering. Micro-tensile testing with specimens machined from the clad zone across or transverse to cladding direction showed high strength but failure in brittle mode. On the other hand, similar testing with samples sectioned from the clad zone parallel or longitudinal to the direction of laser cladding prior to and after post-cladding tempering recorded lower strength but ductile failure with 4.7 and 8 pct elongation, respectively. Wear resistance of the laser surface clad and post-cladding tempered samples (evaluated by fretting wear testing) registered superior performance as compared to that of conventional hardened and tempered AISI H13 tool steel.

  17. OPTIMIZATION OF SURFACE ROUGHNESS AND TOOL FLANK WEAR IN TURNING OF AISI 304 AUSTENITIC STAINLESS STEEL WITH CVD COATED TOOL

    M. Kaladhar; K. Venkata Subbaiah; CH. SRINIVASA RAO

    2013-01-01

    AISI 304 austenitic stainless steel is a popularly used grade in the various fields of manufacturing because of its high ductility, high durability and excellent corrosion resistance. High work hardening, low heat conductivity and high built up edge (BUE) formation made this as difficult-to- machine material. Poor surface quality and rapid tool wear are the common problems encountered while machining it. In the present work, an attempt has been made to explore the influence of machining para...

  18. Mathematical Modelling of Nitride Layer Growth of Low Temperature Gas and Plasma Nitriding of AISI 316L

    Triwiyanto A.; Zainuddin A.; Abidin K.A.Z; Billah M.A; Hussain P.

    2014-01-01

    This paper present mathematical model which developed to predict the nitrided layer thickness (case depth) of gas nitrided and plasma nitrided austenitic stainless steel according to Fick’s first law for pure iron by adapting and manipulating the Hosseini’s model to fit the diffusion mechanism where nitrided structure formed by nitrided AISI 316L austenitic stainless steel. The mathematical model later tested against various actual gas nitriding and plasma nitriding experimental results with ...

  19. Electrochemical deposition of black nickel solar absorber coatings on stainless steel AISI316L for thermal solar cells

    Lira-Cantú, Monica; Morales Sabio, Angel; Brustenga, Alex; Gómez-Romero, P.

    2005-01-01

    We report the electrochemical deposition of nanostructured nickel-based solar absorber coatings on stainless steel AISI type 316L. A sol–gel silica-based antireflection coating, from TEOS, was also applied to the solar surface by the dip-coating method. We report our initial results and analyze the influence of the stainless steel substrate on the final total reflectance properties of the solar absorber. The relation between surface morphology, observed by SEM and AFM, the comp...

  20. Quantifying Cutting and Wearing Behaviors of TiN- and CrN-Coated AISI 1070 Steel

    Ahmet Cakan; Yildirim, Mustafa M.; Vedat Ozkaner

    2008-01-01

    Hard coatings such as titanium nitride (TiN) and chromium nitride (CrN) are widely used in cutting and forming tools against wear and corrosion. In the present study, hard coating films were deposited onto AISI 1070 steels by a cathodic arc evaporation plating (CAVP) technique. These samples were subjected to wear in a conventional lathe for investigating the tribological behaviour of coating structure, and prenitrided subsurface composition was characterized using scanning electron microscop...

  1. Cavitation erosion resistance of AISI 316L stainless steel laser surface-modified with NiTi

    Chiu, K.Y. [Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Cheng, F.T. [Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China)]. E-mail: apaftche@polyu.edu.hk; Man, H.C. [Department of Industrial and Systems Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China)

    2005-02-15

    The present study is part of a project on the surface modification of AISI 316 stainless steel using various forms of NiTi for enhancing cavitation erosion resistance. In this study, NiTi powder was preplaced on the AISI 316L substrate and melted with a high-power CW Nd:YAG laser. With appropriate laser processing parameters, an alloyed layer of a few hundred micrometers thick was formed and fusion bonded to the substrate without the formation of a brittle interface. EDS analysis showed that the layer contained Fe as the major constituent element while the XRD patterns of the surface showed an austenitic structure, similar to that of 316 stainless steel. The cavitation erosion resistance of the modified layer (316-NiTi-Laser) could reach about 29 times that of AISI 316L stainless steel. The improvement could be attributed to a much higher surface hardness and elasticity as revealed by instrumented nanoindentation tests. Among various types of samples, the cavitation erosion resistance was ranked in descending order as: NiTi plate > 316-NiTi-Laser > 316-NiTi-TIG > AISI 316L, where 316-NiTi-TIG stands for samples surfaced with the tungsten inert gas (TIG) process using NiTi wire. Though the laser-surfaced samples and the TIG-surfaced samples had similar indentation properties, the former exhibited a higher erosion resistance mainly because of a more homogeneous alloyed layer with much less defects. In both the laser-surfaced and TIG-surfaced samples, the superelastic behavior typical of austenitic NiTi was only partially retained and the superior cavitation erosion resistance was thus still not fully attained.

  2. Cavitation erosion resistance of AISI 316L stainless steel laser surface-modified with NiTi

    The present study is part of a project on the surface modification of AISI 316 stainless steel using various forms of NiTi for enhancing cavitation erosion resistance. In this study, NiTi powder was preplaced on the AISI 316L substrate and melted with a high-power CW Nd:YAG laser. With appropriate laser processing parameters, an alloyed layer of a few hundred micrometers thick was formed and fusion bonded to the substrate without the formation of a brittle interface. EDS analysis showed that the layer contained Fe as the major constituent element while the XRD patterns of the surface showed an austenitic structure, similar to that of 316 stainless steel. The cavitation erosion resistance of the modified layer (316-NiTi-Laser) could reach about 29 times that of AISI 316L stainless steel. The improvement could be attributed to a much higher surface hardness and elasticity as revealed by instrumented nanoindentation tests. Among various types of samples, the cavitation erosion resistance was ranked in descending order as: NiTi plate > 316-NiTi-Laser > 316-NiTi-TIG > AISI 316L, where 316-NiTi-TIG stands for samples surfaced with the tungsten inert gas (TIG) process using NiTi wire. Though the laser-surfaced samples and the TIG-surfaced samples had similar indentation properties, the former exhibited a higher erosion resistance mainly because of a more homogeneous alloyed layer with much less defects. In both the laser-surfaced and TIG-surfaced samples, the superelastic behavior typical of austenitic NiTi was only partially retained and the superior cavitation erosion resistance was thus still not fully attained

  3. IMPACT OF QUENCH SEVERITY AND HARDNESS ON AISI 4137 USING ECO-FRIENDLY QUENCHANTS AS INDUSTRIAL HEAT TREATMENT

    Adekunle, A. S.; K. A. Adebiyi; Durowoju, M.O

    2013-01-01

    The rate of heat extraction, hardness, and severity of quenching of both edible and non-edible bioquenchants for industrial heat treatment was investigated using AISI 4137 medium carbon steel. Results showed that both the maximum and minimum cooling rates occurred in the nucleate boiling stage and were strongly dependent on the viscosity and saponification number. The peak cooling rates of Jatropha oil, groundnut oil, melon oil, sheabutter oil, palmkernel oil, and palm oil were greater than t...

  4. Effect of fast neutron irradiation on tensile properties of AISI 304 stainless steel and alloy Ti-6Al-4V

    Highlights: → The σy and σUTS of AISI 304 steel increased with fluence and markedly at 4.8 x 1018 n cm-2. → Ductility of the AISI 304 steel is reduced slightly even up to highest fluence. → Marked decrease in σy and relatively less decrease in σUTS occur in the alloy Ti-6Al-4V. → Reduction in ductility occurs in Ti-6Al-4V even at low fluence of 1.2 x 1018 n cm-2. → Both the materials are shown phase instability resulting from neutron irradiation. - Abstract: Effect of fast neutron irradiation at low fluence level of ∼1018 ncm-2, on tensile properties of AISI 304 stainless steel and titanium alloy Ti-6Al-4V, was studied at ambient temperature. Flat tensile specimens, subjected to fast neutron irradiation to three different fluences of 0.6 x 1018, 1.2 x 1018 and 4.8 x 1018 ncm-2, in a reactor, were tested at ambient temperature. It was observed that yield strength and tensile strength of the AISI 304 stainless steel increased marginally, upto the fluence level of 1.2 x 1018 ncm-2, but significantly at the highest fluence of 4.8 x 1018 ncm-2. However there was only nominal decrease in ductility due to neutron irradiation. On the other hand, in the alloy Ti-6Al-4V there was fall both in strength as well as ductility with increase in neutron fluence. Ductility was found to decrease upto the fluence of 1.2 x 1018 ncm-2 and remained constant at higher fluences. Phase instability was revealed by X-ray diffraction in both the neutron irradiated materials.

  5. Swarm Intelligence Based Ant Colony Optimization (ACO Approach for Maximizing the Lifetime of Heterogeneous Wireless Sensor Networks

    LingaRaj.K

    2013-11-01

    Full Text Available This paper attempts to undertake the study of maximizing the lifetime of Heterogeneous wireless sensor networks (WSNs. In wireless sensor networks, sensor nodes are typically power-constrained with limited lifetime, and thus it is necessary to know how long the network sustains its networking operations. Heterogeneous WSNs consists of different sensor devices with different capabilities. We can enhance the quality of monitoring in wireless sensor networks by increasing the coverage area. One of major issue in WSNs is finding maximum number of connected coverage. This paper proposed a Swarm Intelligence, Ant Colony Optimization (ACO based approach. Ant colony optimization algorithm provides a natural and intrinsic way of exploration of search space of coverage area. Ants communicate with their nest- mates using chemical scents known as pheromones, Based on Pheromone trail between sensor devices the shortest path is found. The methodology is based on finding the maximum number of connected covers that satisfy both sensing coverage and network connectivity. By finding the coverage area and sensing range, the network lifetime maximized and reduces the energy consumption

  6. Plasma nitriding process by direct current glow discharge at low temperature increasing the thermal diffusivity of AISI 304 stainless steel

    This work reports for the first time on the use of the open photoacoustic cell technique operating at very low frequencies and at room temperature to experimentally determine the thermal diffusivity parameter of commercial AISI304 stainless steel and AISI304 stainless steel nitrided samples. Complementary measurements of X-ray diffraction and scanning electron microscopy were also performed. The results show that in standard AISI 304 stainless steel samples the thermal diffusivity is (4.0 ± 0.3) × 10−6 m2/s. After the nitriding process, the thermal diffusivity increases to the value (7.1 ± 0.5) × 10−6 m2/s. The results are being associated to the diffusion process of nitrogen into the surface of the sample. Carrying out subsequent thermal treatment at 500 °C, the thermal diffusivity increases up to (12.0 ± 2) × 10−6 m2/s. Now the observed growing in the thermal diffusivity must be related to the change in the phases contained in the nitrided layer.

  7. Wear and Adhesive Failure of Al2O3 Powder Coating Sprayed onto AISI H13 Tool Steel Substrate

    Amanov, Auezhan; Pyun, Young-Sik

    2016-04-01

    In this study, an alumina (Al2O3) ceramic powder was sprayed onto an AISI H13 hot-work tool steel substrate that was subjected to sanding and ultrasonic nanocrystalline surface modification (UNSM) treatment processes. The significance of the UNSM technique on the adhesive failure of the Al2O3 coating and on the hardness of the substrate was investigated. The adhesive failure of the coating sprayed onto sanded and UNSM-treated substrates was investigated by a micro-scratch tester at an incremental load. It was found, based on the obtained results, that the coating sprayed onto the UNSM-treated substrate exhibited a better resistance to adhesive failure in comparison with that of the coating sprayed onto the sanded substrate. Dry friction and wear property of the coatings sprayed onto the sanded and UNSM-treated substrates were assessed by means of a ball-on-disk tribometer against an AISI 52100 steel ball. It was demonstrated that the UNSM technique controllably improved the adhesive failure of the Al2O3 coating, where the critical load was improved by about 31%. Thus, it is expected that the application of the UNSM technique to an AISI H13 tool steel substrate prior to coating may delay the adhesive failure and improve the sticking between the coating and the substrate thanks to the modified and hardened surface.

  8. Wear and Adhesive Failure of Al2O3 Powder Coating Sprayed onto AISI H13 Tool Steel Substrate

    Amanov, Auezhan; Pyun, Young-Sik

    2016-07-01

    In this study, an alumina (Al2O3) ceramic powder was sprayed onto an AISI H13 hot-work tool steel substrate that was subjected to sanding and ultrasonic nanocrystalline surface modification (UNSM) treatment processes. The significance of the UNSM technique on the adhesive failure of the Al2O3 coating and on the hardness of the substrate was investigated. The adhesive failure of the coating sprayed onto sanded and UNSM-treated substrates was investigated by a micro-scratch tester at an incremental load. It was found, based on the obtained results, that the coating sprayed onto the UNSM-treated substrate exhibited a better resistance to adhesive failure in comparison with that of the coating sprayed onto the sanded substrate. Dry friction and wear property of the coatings sprayed onto the sanded and UNSM-treated substrates were assessed by means of a ball-on-disk tribometer against an AISI 52100 steel ball. It was demonstrated that the UNSM technique controllably improved the adhesive failure of the Al2O3 coating, where the critical load was improved by about 31%. Thus, it is expected that the application of the UNSM technique to an AISI H13 tool steel substrate prior to coating may delay the adhesive failure and improve the sticking between the coating and the substrate thanks to the modified and hardened surface.

  9. A preliminary study of laser cladding of AISI 316 stainless steel using preplaced NiTi wire

    NiTi wire of diameter 1 mm was preplaced on AISI 316 stainless steel samples by using a binder. Melting of the NiTi wire to form a clad track on the steel substrate was achieved by means of a high-power CW Nd:YAG laser using different processing parameters. The geometry and microstructure of the clad deposit were studied by optical microscopy and scanning electron microscopy (SEM), respectively. The hardness and compositional profiles along the depth of the deposit were acquired by microhardness testing and energy-dispersive spectroscopy (EDS), respectively. The elastic behavior of the deposit was analyzed using nanoindentation, and compared with that of the NiTi wire. The dilution of the NiTi clad by the substrate material beneath was substantial in single clad tracks, but could be successively reduced in multiple clad layers. A strong fusion bonding with tough interface could be obtained as evidenced by the integrity of Vickers indentations in the interfacial region. In comparison with the NiTi cladding on AISI 316 using the tungsten inert gas (TIG) process, the laser process was capable of producing a much less defective cladding with a more homogeneous microstructure, which is an essential cladding quality with respect to cavitation erosion and corrosion resistance. Thus, the present preliminary study shows that laser cladding using preplaced wire is a feasible method to obtain a thick and homogeneous NiTi-based alloy layer on AISI 316 stainless steel substrate

  10. A preliminary study of laser cladding of AISI 316 stainless steel using preplaced NiTi wire

    Cheng, F.T.; Lo, K.H.; Man, H.C

    2004-08-25

    NiTi wire of diameter 1 mm was preplaced on AISI 316 stainless steel samples by using a binder. Melting of the NiTi wire to form a clad track on the steel substrate was achieved by means of a high-power CW Nd:YAG laser using different processing parameters. The geometry and microstructure of the clad deposit were studied by optical microscopy and scanning electron microscopy (SEM), respectively. The hardness and compositional profiles along the depth of the deposit were acquired by microhardness testing and energy-dispersive spectroscopy (EDS), respectively. The elastic behavior of the deposit was analyzed using nanoindentation, and compared with that of the NiTi wire. The dilution of the NiTi clad by the substrate material beneath was substantial in single clad tracks, but could be successively reduced in multiple clad layers. A strong fusion bonding with tough interface could be obtained as evidenced by the integrity of Vickers indentations in the interfacial region. In comparison with the NiTi cladding on AISI 316 using the tungsten inert gas (TIG) process, the laser process was capable of producing a much less defective cladding with a more homogeneous microstructure, which is an essential cladding quality with respect to cavitation erosion and corrosion resistance. Thus, the present preliminary study shows that laser cladding using preplaced wire is a feasible method to obtain a thick and homogeneous NiTi-based alloy layer on AISI 316 stainless steel substrate.

  11. Plasma nitriding process by direct current glow discharge at low temperature increasing the thermal diffusivity of AISI 304 stainless steel

    Prandel, L. V.; Somer, A.; Assmann, A.; Camelotti, F.; Costa, G.; Bonardi, C.; Jurelo, A. R.; Rodrigues, J. B.; Cruz, G. K. [Universidade Estadual de Ponta Grossa, Grupo de Espectroscopia Optica e Fotoacustica de Materiais, Departamento de Fisica, Av. Carlos Cavalcanti, 4748, CEP 84030-900, Ponta Grossa, PR (Brazil)

    2013-02-14

    This work reports for the first time on the use of the open photoacoustic cell technique operating at very low frequencies and at room temperature to experimentally determine the thermal diffusivity parameter of commercial AISI304 stainless steel and AISI304 stainless steel nitrided samples. Complementary measurements of X-ray diffraction and scanning electron microscopy were also performed. The results show that in standard AISI 304 stainless steel samples the thermal diffusivity is (4.0 {+-} 0.3) Multiplication-Sign 10{sup -6} m{sup 2}/s. After the nitriding process, the thermal diffusivity increases to the value (7.1 {+-} 0.5) Multiplication-Sign 10{sup -6} m{sup 2}/s. The results are being associated to the diffusion process of nitrogen into the surface of the sample. Carrying out subsequent thermal treatment at 500 Degree-Sign C, the thermal diffusivity increases up to (12.0 {+-} 2) Multiplication-Sign 10{sup -6} m{sup 2}/s. Now the observed growing in the thermal diffusivity must be related to the change in the phases contained in the nitrided layer.

  12. Plasma nitriding process by direct current glow discharge at low temperature increasing the thermal diffusivity of AISI 304 stainless steel

    Prandel, L. V.; Somer, A.; Assmann, A.; Camelotti, F.; Costa, G.; Bonardi, C.; Jurelo, A. R.; Rodrigues, J. B.; Cruz, G. K.

    2013-02-01

    This work reports for the first time on the use of the open photoacoustic cell technique operating at very low frequencies and at room temperature to experimentally determine the thermal diffusivity parameter of commercial AISI304 stainless steel and AISI304 stainless steel nitrided samples. Complementary measurements of X-ray diffraction and scanning electron microscopy were also performed. The results show that in standard AISI 304 stainless steel samples the thermal diffusivity is (4.0 ± 0.3) × 10-6 m2/s. After the nitriding process, the thermal diffusivity increases to the value (7.1 ± 0.5) × 10-6 m2/s. The results are being associated to the diffusion process of nitrogen into the surface of the sample. Carrying out subsequent thermal treatment at 500 °C, the thermal diffusivity increases up to (12.0 ± 2) × 10-6 m2/s. Now the observed growing in the thermal diffusivity must be related to the change in the phases contained in the nitrided layer.

  13. Surface modifications of AISI 1045 steel created by high intensity 1064 and 532 nm picosecond Nd:YAG laser pulses

    Interaction of Nd:YAG laser, operating at 1064 or 532 nm wavelength and a pulse duration of 40 ps, with AISI 1045 steel was studied. Surface damage thresholds were estimated to be 0.30 and 0.16 J/cm2 at the wavelengths of 1064 and 532 nm, respectively. The steel surface modification was studied at the laser energy density of 10.3 J/cm2 (at 1064 nm) and 5.4 J/cm2 (at 532 nm). The energy absorbed from Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following AISI 1045 steel surface morphological changes and processes were observed: (i) both laser wavelengths cause damage of the steel in the central zone of irradiated area; (ii) appearance of a hydrodynamic feature in the form of resolidified droplets of the material in the surrounding outer zone with 1064 nm laser wavelength; (iii) appearance of periodic surface structures, at micro- and nano-level, with the 532 nm wavelength and, (iv) development of plasma in front of the target. Generally, interaction of laser beam with the AISI 1045 steel (at 1064 and 532 nm) results in a near-instantaneous creation of damage, meaning that large steel surfaces can be processed in short time.

  14. Weldability evaluation of special stainless steels for utilization in petroleum industry; Avaliacao da soldabilidade de acos inoxidaveis especiais a ser utilizados na industria do petroleo

    Cortes Paredes, Ramon S. [Parana Univ., Curitiba, PR (Brazil)]. E-mail: ramon@demec.ufpr.br; Borsato, Karin Soldatelli [Pontificia Univ. Catolica do Parana, Curitiba, PR (Brazil); Bernardini, Pedro Amadeo Nanneti [Santa Catarina Univ., Florianopolis, SC (Brazil); Villanueva Aguila, Jaime [Universidade de Tarapaca (UTA), Arica (Chile)

    2003-07-01

    A weldability study of super austenitic stainless steel AISI 904L type 25 Ni. 20 Cr, with Mo, Cu and duplex stainless steel UNS S31803 additions is made. The higher mechanical properties and corrosion resistance of duplex stainless steels, when compared to other kinds of stainless steels, have increased the attention of different industrial areas. According to literature, AISI 904L stainless steel is sensitive to solidification and liquation cracking during welding. The main microstructural features, as well as mechanical properties of duplex stainless steels, can be modify when submitted to multiple thermal cycles , such as happen during welding process. Samples have been prepared and welded by two welding processes: coated electrodes and semi-automatic MIG. The objective was to evaluate the cracking sensitiveness of super austenitic steels . For duplex steels the aim was to research the welding process influence for tubular wire in the microstructure and mechanical properties of a 25 mm plate, which are considered of great thickness. In AISI 904L it has not been observed any solidification cracking in the structure in the two welding processes that were studied. However, cracking of liquation in the affected thermal zone has been observed. In duplex steels the use of different thermal cycles showed variation of delta ferrite in the structure of solidification and variation of ferrite grain size in the ZTA. The formation of nitrate and secondary austenitic was also observed, which results in a proportional hardness increase . The mechanical and microstructure characterization data of those two stainless steels are presented. (author)

  15. Qualidade de vida de pacientes submetidos ao transplante cardíaco: aplicação da escala Whoqol-Bref

    Maria Isis Freire de Aguiar

    2011-01-01

    Full Text Available FUNDAMENTO: O sucesso do transplante cardíaco significa garantir a sobrevida dos pacientes com cardiopatia e permitir-lhes desenvolver suas atividades diárias. O transplante cardíaco apresenta-se como a primeira opção de tratamento na falência cardíaca, representando um aumento de sobrevida e qualidade de vida dos transplantados. OBJETIVO: Avaliar a qualidade de vida de pacientes submetidos ao transplante cardíaco através da aplicação de uma escala padronizada (Whoqol-Bref. MÉTODOS: Estudo exploratório descritivo de abordagem quantitativa, realizado com 55 pacientes submetidos ao transplante cardíaco, em um período entre o terceiro e o 103º mês, que realizam acompanhamento na Unidade de Transplante e Insuficiência Cardíaca em um Hospital de Referência em Cardiologia na cidade de Fortaleza, CE. Os dados foram coletados no período de fevereiro a abril de 2009, por meio da aplicação de um questionário padronizado pela Organização Mundial da Saúde e utilização de dados constantes nos prontuários. RESULTADOS: Com relação ao domínio físico, 62,8% e 58,3% dos pacientes, dos sexos masculino e feminino, respectivamente, estão satisfeitos. No domínio psicológico, dentre pacientes do sexo masculino, 65,1% apresentam satisfação quanto à qualidade de vida e, no sexo feminino, 58,3% encontram-se satisfeitas. No domínio das relações sociais, observou-se que, no sexo masculino, 53,5% estão muito satisfeitos, e apresentou-se um nível de satisfação de 100% no sexo feminino. No domínio do meio ambiente, 65,1% do sexo masculino encontram-se satisfeitos, e no sexo feminino, 83,3% estão satisfeitas. CONCLUSÃO: O transplante cardíaco teve bastante influência na qualidade de vida dos pacientes transplantados, pois os resultados mostram-se estatisticamente significantes no pós-transplante.

  16. Hydrogen embrittlement of super austenitic stainless steel welded joints; Fragilizacao por hidrogenio em juntas soldadas de acos inoxidaveis superausteniticos

    Paredes, Ramon S. Cortes [Parana Univ., Curitiba, PR (Brazil). Centro Politecnico. Inst. de Tecnologia para o Desenvolvimento (LACTEC); Berthier, Thiana; Kuromoto, Neide K. [Parana Univ., Curitiba, PR (Brazil). Lab. de Materiais e Tratamento de Superficies. Lab. de Nanopropriedades Mecanicas

    2004-09-15

    The austenitic stainless steel embrittlement is usually present on sulphurous medium due to the hydrogen presence, resulting on cracks and corrosion on acid medium. Several researches carried out on the behaviour of hydrogenated stainless steel structures, had shown that the hydrogen induces superficial phase transformation during hydrogenation period and cracks formation after this period. These are due to the permeation of the hydrogen into the material, which is apprehended on preferential site, resulting on high pressure zones of molecular hydrogen. These zones may lead the crack formation, compromising the mechanical properties. There are few results on austenitic and super austenitic stainless steel, considering the transformations induced on welded unions. This work evaluates the cracks nucleation on welded unions of super austenitic stainless steel AISI 904L exposed to hydrogen rich environments and its relation to the reduction of material ductility. The samples were welded by the Mig/Mag process, followed by hydrogenation which were cathodic on sulfuric acid solution at room temperature. The results showed that the tested super austenitic stainless steel has a significant amount of cracks and no phase transformation has occurred after hydronization. (author)

  17. Biocompatibility evaluation of surface-treated AISI 316L austenitic stainless steel in human cell cultures.

    Martinesi, M; Bruni, S; Stio, M; Treves, C; Bacci, T; Borgioli, F

    2007-01-01

    The effects of AISI 316L austenitic stainless steel, tested in untreated state or subjected to glow-discharge nitriding (at 10 or 20 hPa) and nitriding + post-oxidizing treatments, on human umbilical vein endothelial cells (HUVEC) and on peripheral blood mononuclear cells (PBMC) were evaluated. All the treated samples showed a better corrosion resistance in PBS and higher surface hardness in comparison with the untreated alloy. In HUVEC put in contact for 72 h with the sample types, proliferation and apoptosis decreased and increased, respectively, in the presence of the nitrided + post-oxidized samples, while only slight differences in cytokine (TNF-alpha, IL-6, and TGF-beta1) release were registered. Intercellular adhesion molecule-1 (ICAM-1) increased in HUVEC incubated with all the treated samples, while vascular cell adhesion molecule-1 (VCAM-1) and E-selectin increased in the presence of all the sample types. PBMC incubated for 48 h with the samples showed a decrease in proliferation and an increase in apoptosis in the presence of the untreated samples and the nitrided + post-oxidized ones. All the sample types induced a remarkable increase in TNF-alpha and IL-6 release in PBMC culture medium, while only the untreated sample and the nitrided at 10 hPa induced an increase in ICAM-1 expression. In HUVEC cocultured with PBMC, previously put in contact with the treated AISI 316L samples, increased levels of ICAM-1 were detected. In HUVEC coincubated with the culture medium of PBMC, previously put in contact with the samples under study, a noteworthy increase in ICAM-1, VCAM-1, and E-selectin levels was always registered, with the exception of VCAM-1, which was not affected by the untreated sample. In conclusion, even if the treated samples do not show a marked increase in biocompatibility in comparison with the untreated alloy, their higher corrosion resistance may suggest a better performance as the contact with physiological environment becomes longer. PMID

  18. Evaluación del coeficiente de endurecimiento del acero AISI 1045 deformado por rodillo

    D. Alcántara

    2011-12-01

    Full Text Available El objetivo del trabajo es determinar el comportamiento del coeficiente de endurecimiento n por la ecuación de Hollomon en muestras cilíndricas de acero AISI 1045, las cuales, después de ser deformadas, se sometieron a ensayos de tracción. Se utiliza un diseño de experimento donde se tienen en cuenta las variables número de revolución (n con 27, 54 y 110 rev/min, fuerza de compresión (P de 500, 1 500 y   2 500 N y avance (S de 0,075; 0,125 y 0,25 mm/rev. Finalmente, aplicando el método de regresión se obtuvo un coeficiente de endurecimiento, el cual se aproxima a la linealidad cuando restringimos el cálculo a rangos de deformación elevados. Este coeficiente de endurecimiento se aplica en la ecuación de Hollomon para determinar el nuevo valor de tensión de fluencia y aplicarlo para el cálculo del trabajo mínimo a realizar en un proceso de deformación en frío empleando rodillo simple.   Palabras clave: Deformación Plástica; tensión; deformación; endurecimiento.The objective of the work is to determine the behavior of the hardening coefficient n by the equation of Hollomon, in cylindrical samples of steel AISI 1045, those which, after the deformed, were subjected to traction rehearsals. He used an experiment design where are kept in mind the revolution number (n with 27, 54 and 110 rev/min, it compression forces (P of 500, 1 500 and 2 500 N and feed (S of 0.075; 0.125 and 0.25 mm/rev. Finally, applying the regression method a hardening coefficient was obtained, which approaches to the linearity when restrict the calculation to high ranges of deformation. This hardening coefficient is applied in the equation of Hollomon for determine the new value of flow tension and to apply in the calculation of the minimum work to carry out in a cold process of deformation using simple roller.   Keywords: Plastic deformation; stress; deformation; hardening.

  19. Evaluación del comportamiento estructural y de resistencia a la corrosión de armaduras de acero inoxidable austenítico AISI 304 y dúplex AISI 2304 embebidas en morteros de cemento Pórtland

    Medina, E.; Cobo, A.; Bastidas, D. M.

    2012-01-01

    The mechanical and structural behaviour of two stainless steels reinforcements, with grades austenitic EN 1.4301 (AISI 304) and duplex EN 1.4362 (AISI 2304) have been studied, and compared with the conventional carbon steel B500SD rebar. The study was conducted at three levels: at rebar level, at section level and at structural element level. The different mechanical properties of stainless steel directly influence the behaviour at section level and structural element level. The study of the ...

  20. Welding of AA1050 aluminum with AISI 304 stainless steel by rotary friction welding process

    Chen Ying An

    2010-09-01

    Full Text Available The purpose of this work was to assess the development of solid state joints of dissimilar material AA1050 aluminum and AISI 304 stainless steel, which can be used in pipes of tanks of liquid propellants and other components of the Satellite Launch Vehicle. The joints were obtained by rotary friction welding process (RFW, which combines the heat generated from friction between two surfaces and plastic deformation. Tests were conducted with different welding process parameters. The results were analyzed by means of tensile tests, Vickers microhardness, metallographic tests and SEM-EDX. The strength of the joints varied with increasing friction time and the use of different pressure values. Joints were obtained with superior mechanical properties of the AA1050 aluminum, with fracture occurring in the aluminum away from the bonding interface. The analysis by EDX at the interface of the junction showed that interdiffusion occurs between the main chemical components of the materials involved. The RFW proves to be a great method for obtaining joints between dissimilar materials, which is not possible by fusion welding processes.

  1. Thermodynamic modeling and kinetics simulation of precipitate phases in AISI 316 stainless steels

    Yang, Y., E-mail: yangying@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Busby, J.T. [Fusion and Materials for Nuclear Systems Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2014-05-01

    This work aims at utilizing modern computational microstructural modeling tools to accelerate the understanding of phase stability in austenitic steels under extended thermal aging. Using the CALPHAD approach, a thermodynamic database OCTANT (ORNL Computational Thermodynamics for Applied Nuclear Technology), including elements of Fe, C, Cr, Ni, Mn, Mo, Si, and Ti, has been developed with a focus on reliable thermodynamic modeling of precipitate phases in AISI 316 austenitic stainless steels. The thermodynamic database was validated by comparing the calculated results with experimental data from commercial 316 austenitic steels. The developed computational thermodynamics was then coupled with precipitation kinetics simulation to understand the temporal evolution of precipitates in austenitic steels under long-term thermal aging (up to 600,000 h) at a temperature regime from 300 to 900 °C. This study discusses the effect of dislocation density and difusion coefficients on the precipitation kinetics at low temperatures, which shed a light on investigating the phase stability and transformation in austenitic steels used in light water reactors.

  2. Dissimilar friction welding of 6061-T6 aluminum and AISI 1018 steel: Properties and microstructural characterization

    Joining of dissimilar materials is of increasing interest for a wide range of industrial applications. The automotive industry, in particular, views dissimilar materials joining as a gateway for the implementation of lightweight materials. Specifically, the introduction of aluminum alloy parts into a steel car body requires the development of reliable, efficient and economic joining processes. Since aluminum and steel demonstrate different physical, mechanical and metallurgical properties, identification of proper welding processes and practices can be problematic. In this work, inertia friction welding has been used to create joints between a 6061-T6 aluminum alloy and a AISI 1018 steel using various parameters. The joints were evaluated by mechanical testing and metallurgical analysis. Microstructural analyses were done using metallography, microhardness testing, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray elemental mapping, focused ion beam (FIB) with ultra high resolution SEM and transmission electron microscopy (TEM) in TEM and STEM modes. Results of these analysis first suggested that joint strengths on the order of 250 MPa could be achieved. In addition, failures were seen in the plasticized layer on the aluminum side of the joint. Further, bond lines were characterized by a thin layer of formed Al-Fe intermetallic. This intermetallic layer averaged roughly 250 nm thick and compositionally appears related to the FeAl and Fe2Al5 phases.

  3. Carburization behavior of AISI 316LN austenitic stainless steel - Experimental studies and modeling

    AISI type 316LN austenitic stainless steel was exposed to flowing sodium at 798 K for 16,000 h in the bi-metallic (BIM) sodium loop. A modified surface layer of 10 μm width having a ferrite structure was detected from X-ray diffraction and electron micro probe based analysis. Beneath the modified surface layer a carburized zone of 60 μm width was identified which was found to consist of M23C6 carbides. A mathematical model based on finite difference technique was developed to predict the carburization profiles in sodium exposed austenitic stainless steel. In the computation, effect of only chromium on carbon diffusion was considered. Amount of carbon remaining in solution was determined from the solubility parameter. The predicted profile showed a reasonably good match with the experimental profile. Calculations were extended to simulate the thickness of the carburized layer after exposure to sodium for a period of 40 years. Attempt was also made to predict the carburization profiles based on equilibrium calculations using Dictra and Thermocalc which contain both thermodynamic and kinetic databases for the system under consideration.

  4. CRYOGENIC AND STRESS RELIEF THERMAL TREATMENTS IN AN AISI D2 STEEL

    Paula Fernanda da Silva Farina

    2012-06-01

    Full Text Available The effects of cryogenic treatments on an AISI D2 cold work tool steel using X-ray diffraction from syncronton radiation are studied. The aim of this work is to verify the effects of: i time at cryogenic temperatures (3, 10 and 30 hours; ii cryogenic temperatures (–80°C and –196°C; iii stress relief heat treatment (130°C before cryogenic treatments; iv effect of double tempering at 520°C for 2 hours each time, after cryogenic treatment at –196°C for 30 hours, with and without previous stress relief. X-ray diffraction experiments were conducted at the line D10B-XPD of the Laboratório Nacional de Luz Síncrotron and the experimental results were treated using Rietveld refining, with TOPAS Academic in conjunction with cards from the ICCD-PDF 2006 database for austenite, martensite and carbides M7C3and M2C. Tempered samples were characterized using SEM and SEM-FEG. Volume fraction of retained austenite and carbides, as well as changes in the crystal lattices of martensite and austenite are obtained from the X-ray experiments.

  5. Surface severe plastic deformation of AISI 304 via conventional shot peening, severe shot peening and repeening

    Highlights: • CSP and SSP treatments transform austenite to metastable martensite structure. • Nanograin layer thickness after CSP and SSP is 8 μm and 22 μm, respectively. • Shot peening leads to carbon segregation from coarse to nano grain layer. • Repeening is an effective way to reduce surface roughness. - Abstract: Air blast conventional shot peening (CSP), severe shot peening (SSP) and repeening (RP) as a severe plastic deformation applications on AISI 304 austenitic stainless steel is addressed. Shot peened specimens are investigated based on optical, FESEM and digital microscope. The investigations present the austenite transformation to metastable martensite via mechanical twinning due to plastic deformation with high strain rates. It is found that SSP induces thicker nanograin layer with compared to CSP. In XRD studies, the austenite peaks broaden by means of severe shot peening and FWHM increase reveals the grain size reduction below 25 nm regimes on the surface. In EDAX line analysis of CSP specimen, carbon content increase has been detected from deformed layer through the nanocrystalline layer then the content reduces. The carbon segregation takes place due to the energy level distinction between dislocations and Fe−C bonds. 3d contour digital microscope studies and roughness investigations reveal that SSP has deleterious side effect on the surface roughness and surface flatness. However, RP is an effective way to reduce the surface roughness to reasonable values

  6. Surface characterization of stainless steel AISI 316 L in contact with simulated body fluid

    Titanium and cobalt alloys, as well as some stainless steels, are often used in orthopedic surgery. In the more developed countries, stainless steel is used only for temporary implants since it does not hold up as well as other alloys to corrosion in a physiological medium. Nevertheless, stainless steel alloys are frequently used for permanent implants in developing countries. Therefore, more knowledge about its reaction to corrosion is needed as well as the characteristics of the surface layer generated in a physiological medium in order to control potential toxicity from the release of metallic ions into the organism. The surface films usually have a different composition and chemical state from the base material. The surface characterization of alloys used in orthopedic surgery should not be underestimated, since it heavily influences the behavior of the implant through the relationship of the surface film-tissue and the possible migration of metallic ions from the base metal to the surrounding tissue. This work presents a study of the surface composition and resistance to the corrosion of stainless steel AISI 316L in simulated body fluid (SBF) aired at pH 7.25 and 37oC. The resistance to the corrosion was studied with an electrochemical impedance spectroscopy (EIS) and anodic polarization curves (CW)

  7. Machining tools in AISI M2 high-speed steel obtained by spray forming process

    The aim of the present work was the obtention of AISI M2 high-speed steel by spray forming technique and the material evaluation when used as machining tool. The obtained material was hot rolled at 50% and 72% reduction ratios, and from which it was manufactured inserts for machining tests. The performance of inserts made of the spray formed material was compared to inserts obtained from conventional and powder metallurgy (MP) processed materials. The spray formed material was chemical, physical, mechanical and microstructural characterised. For further characterisation, the materials were submitted to machining tests for performance evaluation under real work condition. The results of material characterisation highlight the potential of the spray forming technique, in the obtention of materials with good characteristics and properties. Under the current processing, hot rolling and heat treatments condition, the analysis of the results of the machining tests revealed a very similar behaviour among the tested materials. Proceeding a criterious analysis of the machining results tests, it was verified that the performance presented by the powder metallurgy material (MP) was slight superior, followed by conventional obtained material (MConv), which presented a insignificant advantage over the spray formed and hot rolled (72% reduction ratio) material. The worst result was encountered for the spray forming and hot rolled (50% reduction ratio) material that presented the highest wear values. (author)

  8. Surface modification of AISI H13 tool steel by laser cladding with NiTi powder

    Norhafzan, B.; Aqida, S. N.; Chikarakara, E.; Brabazon, D.

    2016-04-01

    This paper presents laser cladding of NiTi powder on AISI H13 tool steel surface for surface properties enhancement. The cladding process was conducted using Rofin DC-015 diffusion-cooled CO2 laser system with wavelength of 10.6 µm. NiTi powder was pre-placed on H13 tool steel surface. The laser beam was focused with a spot size of 90 µm on the sample surface. Laser parameters were set to 1515 and 1138 W peak power, 18 and 24 % duty cycle and 2300-3500 Hz laser pulse repetition frequency. Hardness properties of the modified layer were characterized by Wilson Hardness tester. Metallographic study and chemical composition were conducted using field emission scanning electron microscope and energy-dispersive X-ray spectrometer (EDXS) analysis. Results showed that hardness of NiTi clad layer increased three times that of the substrate material. The EDXS analysis detected NiTi phase presence in the modified layer up to 9.8 wt%. The metallographic study shows high metallurgical bonding between substrate and modified layer. These findings are significant to both increased hardness and erosion resistance of high-wear-resistant components and elongating their lifetime.

  9. Effects of heat treatment on mechanical properties of modified cast AISI D3 tool steel

    Highlights: • Secondary hardening occurred when tempered at 500 °C and austenitized at 1050 °C. • Hardness of new steel is about 1 HRC higher than D3 steel, when tempered at 300 °C. • New steel has less bending strength and strain compared with D3 steel. • With increasing hardness wear resistance is improved about 56%. • Linear relationship observed between weight loss and hardness of modified steel. - Abstract: In this research new modified as-cast cold work AISI D3 tool steel was produced by increasing Ti and Nb and decreasing Cr. At first, Cast samples were homogenized at optimized cycle and then austenitized and tempered within the specified temperature ranges. Mechanical properties and wear behavior were determined by performing hardness test, three point bending test and pin on disc wear test. Also, scanning electron microscope was employed to characterize the new modified steel. For the specimens austenitized and tempered at 1050 °C and 500 °C respectively, the secondary hardening effect was observed which was consistent with lower weight loss of pin on disc wear test results. The results show that, the new modified as-cast steel represents hardness and wear resistance equal to or better than that of standard wrought D3 steel, while its strength and toughness are lower than those of wrought steel

  10. Problems in laser repair-cladding a surface AISI D2 heat treated tool steel

    The aim of the present work is to establish the relationship between laser cladding process parameters (Power, Process Speed and Powder feed rate) and AISI D2 tool steel metallurgical transformations, with the objective of optimizing the processing conditions during real reparation. It has been deposited H13 tool steel powder on some steel substrates with different initial metallurgical status (annealed or tempered) using a coaxial laser cladding system. The microstructure of the laser clad layer and substrate heat affected zone (HAZ) was characterized by Optical microscopy, Scanning Electron Microscopy (SEM) and Electron Backscattered Diffraction (EBSD). Results show that the process parameters (power, process speed, feed rate) determine the dimensions of the clad layer and are related to the microstructure formation. Although it is simple to obtain geometrically acceptable clads (with the right shape and dimensions) in many cases occur some harmful effects as carbide dilution and non-equilibrium phases formation which modify the mechanical properties of the coating. Specifically, the presence of retained austenite in the substrate-coating interface is directly related to the cooling rate and implies a hardness diminution that must be avoided. It has been checked that initial metallurgical state of the substrate has a big influence in the final result of the deposition. Tempered substrates imply higher laser absorption and heat accumulation than the ones in annealed condition. This produces a bigger HAZ. For this reason, it is necessary to optimize process conditions for each reparation in order to improve the working behaviour of the component. (Author)

  11. Electromagnetic nondestructive evaluation of tempering process in AISI D2 tool steel

    Kahrobaee, Saeed, E-mail: saeed.kahrobaee@yahoo.com; Kashefi, Mehrdad, E-mail: m-kashefi@um.ac.ir

    2015-05-15

    The present paper investigates the potential of using eddy current technique as a reliable nondestructive tool to detect microstructural changes during the different stages of tempering treatment in AISI D2 tool steel. Five stages occur in tempering of the steel: precipitation of ε carbides, formation of cementite, retained austenite decomposition, secondary hardening effect and spheroidization of carbides. These stages were characterized by destructive methods, including dilatometry, differential scanning calorimetry, X-ray diffraction, scanning electron microscopic observations, and hardness measurements. The microstructural changes alter the electrical resistivity/magnetic saturation, which, in turn, influence the eddy current signals. Two EC parameters, induced voltage sensed by pickup coil and impedance point detected by excitation coil, were evaluated as a function of tempering temperature to characterize the microstructural features, nondestructively. The study revealed that a good correlation exists between the EC parameters and the microstructural changes. - Highlights: • D2 steel parts were tempered at 200-650 °C to produce various microstructures. • Precipitation of ε and Fe{sub 3}C carbides and spheroidization of carbides were detected. • Retained austenite decomposition and secondary hardening effect were determined. • Variations of electrical resistivity (ρ) and magnetic saturation (Bs) were studied. • Combined effects of ρ and Bs on the EC outputs were evaluated.

  12. Electromagnetic nondestructive evaluation of tempering process in AISI D2 tool steel

    The present paper investigates the potential of using eddy current technique as a reliable nondestructive tool to detect microstructural changes during the different stages of tempering treatment in AISI D2 tool steel. Five stages occur in tempering of the steel: precipitation of ε carbides, formation of cementite, retained austenite decomposition, secondary hardening effect and spheroidization of carbides. These stages were characterized by destructive methods, including dilatometry, differential scanning calorimetry, X-ray diffraction, scanning electron microscopic observations, and hardness measurements. The microstructural changes alter the electrical resistivity/magnetic saturation, which, in turn, influence the eddy current signals. Two EC parameters, induced voltage sensed by pickup coil and impedance point detected by excitation coil, were evaluated as a function of tempering temperature to characterize the microstructural features, nondestructively. The study revealed that a good correlation exists between the EC parameters and the microstructural changes. - Highlights: • D2 steel parts were tempered at 200-650 °C to produce various microstructures. • Precipitation of ε and Fe3C carbides and spheroidization of carbides were detected. • Retained austenite decomposition and secondary hardening effect were determined. • Variations of electrical resistivity (ρ) and magnetic saturation (Bs) were studied. • Combined effects of ρ and Bs on the EC outputs were evaluated

  13. Simultaneous enhancement of strength and ductility in cryogenically treated AISI D2 tool steel

    Ghasemi-Nanesa, Hadi; Jahazi, Mohammad, E-mail: mohammad.jahazi@etsmtl.ca

    2014-03-01

    In this research, the effect of cryogenic treatment on microstructural evolution and mechanical properties enhancement of AISI D2 tool steel was investigated. Cryogenic treatment down to liquid nitrogen temperature (77 K) was added to the conventional heat treatment between hardening and tempering steps. Electron microscopy investigation showed higher volume fraction of fine carbides with average diameter below 1 μm indicating effective retardation in carbide coarsening process as a results of cryogenic treatment. A modification in types of carbides was also observed after cryogenic treatment. X-ray diffraction diagrams revealed transformation of retained austenite to martensite at cryogenic temperature. Weakening or removal of carbides peak in the X-ray diagram was considered as evidence of carbides different behavior at cryogenic temperature. Mechanical testing results indicated higher ultimate tensile strength, better ductility, and higher elastic modulus after cryogenic treatment. Analysis of stress–strain diagrams revealed different strain hardening behavior for cryogenically treated alloy when compared to the conventionally heat treated one. Fractography results confirmed strain hardening behavior and showed cleavage fracture for conventionally treated alloy but mixed cleavage–ductile fracture mode for cryogenically treated alloy. The improved mechanical properties after cryogenic treatment are interpreted in terms of the influence of higher volume fraction and uniform distribution of fine carbides in reducing the average active dislocations length and enhancement of the flow stress at any given plastic strain.

  14. Effect of thermal cycles on heavily cold deformed AISI 304L austenitic stainless steel

    The solution treated commercial grade AISI 304L austenitic stainless steel plate was heavily cold rolled to 90% of thickness reduction. Cold rolled specimens were annealed at various temperatures by thermal cycles and isothermal annealing. Strain-induced phase transformations and microstructure studies were carried out both in the cold rolled and annealed conditions. The X-ray diffraction and magnetic measurements were used for phase transformation studies. The transmission electron microscope characterisation revealed that the cyclic thermal process resulted in ultrafine grain austenite formation whereas, the isothermal annealing developed coarser grain size microstructure. The different microstructural evolutions by the above two processes largely influenced the development of the recrystallisation texture. The thermal cycling produced a distinct γ-fibre texture while the isothermal annealing resulted in a cube texture component along with the γ-fibre. The γ-fibre texture evolution was attributed to the over critical subgrains or nuclei and {1 0 0} cube texture to the coarser grains of micrometer size.

  15. Q-switch Nd:YAG laser welding of AISI 304 stainless steel foils

    Conventional fusion welding of stainless steel foils (<100 μm thickness) used in computer disk, precision machinery and medical device applications suffer from excessive distortion, formation of discontinuities (pore, void and hot crack), uncontrolled melting (melt-drop through) and poor aesthetics. In this work, a 15 ns pulsed, 400 mJ Nd:YAG laser beam was utilized to overcome these barriers in seam welding of 60 μm thin foil of AISI 304 stainless steel. Transmission electron microscopy was used to characterize the microstructures while hardness and tensile-shear tests were used to evaluate the strengths. Surface roughness was measured using a DekTak profilometer while porosity content was estimated using the light microscope. Results were compared against the data obtained from resistance seam welding. Laser welding, compared to resistance seam welding, required nearly three times less heat input and produced welds having 50% narrower seam, 15% less porosity, 25% stronger and improved surface aesthetics. In addition, there was no evidence of δ-ferrite in laser welds, supporting the absence of hot cracking unlike resistance welding

  16. Carburization behavior of AISI 316LN austenitic stainless steel - Experimental studies and modeling

    Sudha, C.; Sivai Bharasi, N.; Anand, R.; Shaikh, H.; Dayal, R. K.; Vijayalakshmi, M.

    2010-07-01

    AISI type 316LN austenitic stainless steel was exposed to flowing sodium at 798 K for 16,000 h in the bi-metallic (BIM) sodium loop. A modified surface layer of 10 μm width having a ferrite structure was detected from X-ray diffraction and electron micro probe based analysis. Beneath the modified surface layer a carburized zone of 60 μm width was identified which was found to consist of M 23C 6 carbides. A mathematical model based on finite difference technique was developed to predict the carburization profiles in sodium exposed austenitic stainless steel. In the computation, effect of only chromium on carbon diffusion was considered. Amount of carbon remaining in solution was determined from the solubility parameter. The predicted profile showed a reasonably good match with the experimental profile. Calculations were extended to simulate the thickness of the carburized layer after exposure to sodium for a period of 40 years. Attempt was also made to predict the carburization profiles based on equilibrium calculations using Dictra and Thermocalc which contain both thermodynamic and kinetic databases for the system under consideration.

  17. Carburization behavior of AISI 316LN austenitic stainless steel - Experimental studies and modeling

    Sudha, C. [Physical Metallurgy Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Sivai Bharasi, N. [Corrosion Science and Technology Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Anand, R. [Physical Metallurgy Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Shaikh, H., E-mail: hasan@igcar.gov.i [Corrosion Science and Technology Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Dayal, R.K. [Corrosion Science and Technology Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Vijayalakshmi, M. [Physical Metallurgy Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India)

    2010-07-31

    AISI type 316LN austenitic stainless steel was exposed to flowing sodium at 798 K for 16,000 h in the bi-metallic (BIM) sodium loop. A modified surface layer of 10 {mu}m width having a ferrite structure was detected from X-ray diffraction and electron micro probe based analysis. Beneath the modified surface layer a carburized zone of 60 {mu}m width was identified which was found to consist of M{sub 23}C{sub 6} carbides. A mathematical model based on finite difference technique was developed to predict the carburization profiles in sodium exposed austenitic stainless steel. In the computation, effect of only chromium on carbon diffusion was considered. Amount of carbon remaining in solution was determined from the solubility parameter. The predicted profile showed a reasonably good match with the experimental profile. Calculations were extended to simulate the thickness of the carburized layer after exposure to sodium for a period of 40 years. Attempt was also made to predict the carburization profiles based on equilibrium calculations using Dictra and Thermocalc which contain both thermodynamic and kinetic databases for the system under consideration.

  18. Electronic structures and nitride formation on ion-implanted AISI 304L austenitic stainless steel

    Chang, G.S.; Son, J.H.; Kim, S.H.; Chae, K.H.; Whang, C.N. (Yonsei Univ., Seoul (Korea, Republic of). Dept. of Physics); Menthe, E.; Rie, K.-T.; Lee, Y.P.

    1999-02-01

    A N[sub 2][sup +] implantation technique was employed to improve the surface hardness of stainless steel, and the electronic structures and nitride formation of the ion-implanted layer were investigated and compared with those produced using other techniques, including plasma nitriding. AISI 304L austenite stainless steel was irradiated by 80 keV N[sub 2][sup +] with a dosage ranging from 1.0 x 10[sup 16] to 1.0 x 10[sup 18] ions cm[sup -2] at room temperature. The formation of various nitrides was confirmed by X-ray diffraction. The quantitative hardness of the samples was measured by using a Knoop microhardness tester. X-ray photoelectron spectroscopy was also carried out to elucidate the chemical states and electronic structures of the ion-implanted layers. The measurements were repeated after post-annealing at 400 C for 1 h in a high vacuum. Changes in phase, chemical state and electronic structures were observed according to the ion dose and heat treatment. (orig.) 12 refs.

  19. Crack propagation in stainless steel AISI 304L in Hydrogen Chemistry conditions (HWC)

    Velocities of crack growth in samples type CT pre cracking of stainless steel AISI 304l solder and sensitized thermally its were obtained by the Rising Displacement method or of growing displacement. It was used a recirculation circuit that simulates the operation conditions of a BWR type reactor (temperature of 280 C and a pressure of 8 MPa) with the chemistry modified by the addition of hydrogen with and without the addition of impurities of a powerful oxidizer like the Cu+ ion. In each essay stayed a displacement velocity was constant of 1x10-9 m/s, making a continuous pursuit of the advance of the crack by the electric potential drop technique. Contrary to the idea of mitigation of the crack propagation velocity by effect of the addition of the hydrogen in the system, the values of the growth velocities obtained by this methodology went similar to the opposing ones under normal operation conditions. To the finish of the rehearsal one carries out the fractographic analysis of the propagation surfaces, which showed cracks growth in trans and intergranular way, evidencing the complexity of the regulator mechanisms of the IGSCC like in mitigation conditions as the alternative Hydrogen Chemistry. (Author)

  20. Plasma nitriding of AISI 52100 ball bearing steel and effect of heat treatment on nitrided layer

    Ravindra Kumar; J Alphonsa; Ram Prakash; K S Boob; J Ghanshyam; P A Rayjada; P M Raole; S Mukherjee

    2011-02-01

    In this paper an effort has been made to plasma nitride the ball bearing steel AISI 52100. The difficulty with this specific steel is that its tempering temperature (∼170–200°C) is much lower than the standard processing temperature (∼460–580°C) needed for the plasma nitriding treatment. To understand the mechanism, effect of heat treatment on the nitrided layer steel is investigated. Experiments are performed on three different types of ball bearing races i.e. annealed, quenched and quench-tempered samples. Different gas compositions and process temperatures are maintained while nitriding these samples. In the quenched and quench-tempered samples, the surface hardness has decreased after plasma nitriding process. Plasma nitriding of annealed sample with argon and nitrogen gas mixture gives higher hardness in comparison to the hydrogen–nitrogen gas mixture. It is reported that the later heat treatment of the plasma nitrided annealed sample has shown improvement in the hardness of this steel. X-ray diffraction analysis shows that the dominant phases in the plasma nitrided annealed sample are (Fe2−3N) and (Fe4N), whereas in the plasma nitrided annealed sample with later heat treatment only -Fe peak occurs.

  1. Effect of V Notch Shape on Fatigue Life in Steel Beam Made of AISI 1037

    Qasim Bader

    2014-04-01

    Full Text Available The present work encompasses effect of V notch shape with various geometries and dimensions on fatigue life behavior in steel beam made of Medium Carbon Steel AISI 1037 which has a wide application in industry. Fatigue life of notched specimens is calculated using the fatigue life obtained from the experiments for smooth specimens (reference and by use Numerical method (FEA.The fatigue experiments were carried out at room temperature, applying a fully reversed cyclic load with the frequency of (50Hz and mean stress equal to zero (R= -1, on a cantilever rotating-bending fatigue testing machine. The stress ratio was kept constant throughout the experiment. Different instruments have been used in this investigation like Chemical composition analyzer type (Spectromax ,Tensile universal testing machine type (WDW-100E ,Hardness tester type (HSV- 1000 , Fatigue testing machine model Gunt WP 140, Optical Light Microscope (OLM and Scanning Electron Microscope (SEM were employed to examine the fracture features . The results show that there is acceptable error between experimental and numerical works .

  2. Selective laser melting of Fe-Ni-Cr layer on AISI H13 tool steel

    Byeong-Don JOO; Jeong-Hwan JANG; Jae-Ho LEE; Young-Myung SON; Young-Hoon MOON

    2009-01-01

    An attempt to fabricate Fe-Ni-Cr coating on AISI H13 tool steel was performed with selective laser melting. Fe-Ni-Cr coating was produced by experimental facilities consisting of a 200 W fiber laser which can be focused to 80 μm and atmospheric chamber which can control atmospheric pressure with N2 or Ar. Coating layer was fabricated with various process parameters such as laser power, scan rate and fill spacing. Surface quality and coating thickness were measured and analyzed. Three different surface patterns, such as typeⅠ, typeⅡand type Ⅲ, are shown with various test conditions and smooth regular pattern is obtained under the conditions as 10 μm of fill spacing, 50-350 mm/s of scan rate and 40 μm of fill spacing, 10-150 mm/s of scan rate. The maximum coating thickness is increased with power elevation or scan rate drop, and average thickness of 10 μm fill spacing is lower than that of 40 μm fill spacing.

  3. Low temperature tensile deformation and acoustic emission signal characteristics of AISI 304LN stainless steel

    Barat, K.; Bar, H.N. [Material Science and Technology Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Mandal, D. [Material Processing and Technology Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Roy, H., E-mail: himadri9504@gmail.com [NDT and Metallurgy Group, CSIR-Central Mechanical Engineering Research Institute, Durgapur 713209 (India); Sivaprasad, S.; Tarafder, S. [Material Science and Technology Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India)

    2014-03-01

    This investigation examines low temperature tensile deformation behavior of AISI 304LN stainless steel along with synergistic analysis of acoustic emission signals. The tensile tests are done at a range of temperatures starting from 283 K till 223 K. The fracture surfaces of the broken specimens are investigated using scanning electron microscope. The amount of deformation induced martensite is measured using a feritscope. The obtained results reveal that with decrease in test temperature, both strength and ductility increase. The increase in strength and ductility with decreasing temperature is explained in terms of void morphologies and formation of deformation induced martensite. The rapid increment in strength and ductility at 223 K is associated with the burst of martensitic transformation at that temperature; which has been clarified from acoustic emission signals. An additional initiative has been taken to model the evolution of martensite formation from the observed cumulative emission counts using a non linear logarithmic functional form. The fitted curves from the recorded acoustic emission cumulative count data are found to be better correlated compared to earlier obtained results. However, at 223 K normal non-linear logarithmic fit is not found suitable due to presence of burst type signals at intervals, therefore; piecewise logarithmic function to model acoustic emission bursts is proposed.

  4. Low temperature tensile deformation and acoustic emission signal characteristics of AISI 304LN stainless steel

    This investigation examines low temperature tensile deformation behavior of AISI 304LN stainless steel along with synergistic analysis of acoustic emission signals. The tensile tests are done at a range of temperatures starting from 283 K till 223 K. The fracture surfaces of the broken specimens are investigated using scanning electron microscope. The amount of deformation induced martensite is measured using a feritscope. The obtained results reveal that with decrease in test temperature, both strength and ductility increase. The increase in strength and ductility with decreasing temperature is explained in terms of void morphologies and formation of deformation induced martensite. The rapid increment in strength and ductility at 223 K is associated with the burst of martensitic transformation at that temperature; which has been clarified from acoustic emission signals. An additional initiative has been taken to model the evolution of martensite formation from the observed cumulative emission counts using a non linear logarithmic functional form. The fitted curves from the recorded acoustic emission cumulative count data are found to be better correlated compared to earlier obtained results. However, at 223 K normal non-linear logarithmic fit is not found suitable due to presence of burst type signals at intervals, therefore; piecewise logarithmic function to model acoustic emission bursts is proposed

  5. Metallurgical response of an AISI 4140 steel to different plasma nitriding gas mixtures

    Adão Felipe Oliveira Skonieski

    2013-01-01

    Full Text Available Plasma nitriding is a surface modification process that uses glow discharge to diffuse nitrogen atoms into the metallic matrix of different materials. Among the many possible parameters of the process, the gas mixture composition plays an important role, as it impacts directly the formed layer's microstructure. In this work an AISI 4140 steel was plasma nitrided under five different gas compositions. The plasma nitriding samples were characterized using optical and scanning electron microscopy, microhardness test, X-ray diffraction and GDOES. The results showed that there are significant microstructural and morphological differences on the formed layers depending on the quantity of nitrogen and methane added to the plasma nitriding atmosphere. Thicknesses of 10, 5 and 2.5 µm were obtained when the nitrogen content of the gas mixtures were varied. The possibility to obtain a compound layer formed mainly by γ'-Fe4N nitrides was also shown. For all studied plasma nitriding conditions, the presence of a compound layer was recognized as being the responsible to hinder the decarburization on the steel surface. The highest value of surface hardness - 1277HV - were measured in the sample which were nitrided with 3vol.% of CH4.

  6. Propagation of crevices in stainless steel AISI304L in conditions of hydrogen chemistry (HWC)

    Crevice growth velocities in samples of AISI 304L stainless steel thermally welded and sensitized were obtained by the Rising displacement method or of growing displacement. It was used a recirculation circuit in where the operation conditions of a BWR type reactor were simulated (temperature of 288 C and a pressure of 8 MPa) with the chemistry modified by the addition of hydrogen with and without the addition of impurities of a powerful oxidizer like the Cu++ ion. CT pre cracked specimens were used and each rehearsal stayed to one constant displacement velocity of 1 x 10-9 m/s (3.6 μm/hr), making a continuous pursuit of the advance of the crack by the electric potential drop technique. To the end of the rehearsal it was carried out the fractographic analysis of the propagation surfaces. The values of the growth velocities obtained by this methodology went similar to the opposing ones under normal conditions of operation; while the fractographic analysis show the cracks propagation in trans and intergranular ways, evidencing the complexity of the regulator mechanisms of the one IGSCC even under controlled ambient conditions or with mitigation methodologies like the alternative hydrogen chemistry. (Author)

  7. Interlaboratory study of the AISI 316L steel tribo-corrosion

    Seven European laboratories have participated in an interlaboratory study of AISI 316L stainless steel tribo-corrosion. Different tests arrangements have been used (rotating pin-on-disc and disc-on-pin, rotating tube-on-flat, alternating pin-on-flat) depending on the test laboratory. The experimental conditions for the various tests have ranged from: 0.1 to 30 N for normal loads, 1 to 33 Hz for frequency and 5 to 150 mm/sec for linear speed, 0.79 to 25.50 cm2 for electrode surfaces, -244 to -71 mV for corrosion potentials, and -33 to 46 mV for passivation potentials. Data for electrochemical potentials during frictional wear, coefficients of friction, wear rates and wear channel size are tabulated in this article. A dispersion of data is observed between the laboratories for friction coefficients; but this dispersion of data is comparable and even inferior to that obtained in VAMAS interlaboratory tests. Electrochemical tests results also have a convergence that is typical of a previous interlaboratory test program conducted by EFC. A large deviation in coefficients of wear is observed and is also typical of previous VAMAS testing

  8. Tribological Properties of MoSi2 Against AISI10045 Steel Under Sliding Friction

    CHEN Ping; ZHANG Hou-an; CHEN Hua-hui

    2006-01-01

    MoSi2 samples were prepared by a self-propagating high-temperature synthesis (SHS) and a hot-press technique. The sliding friction and wear properties of intermetallic MoSi2 against AISI10045 steel under dry friction and oil lubrication conditions were investigated with a MRH-5A type ring-on-block friction and wear tester. The elemental composition, microstructure and worn surface morphology of the MoSi2 material were observed and analyzed by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The synthetic parameter pv value reflecting friction work, was used to discuss the tribological properties of MoSi2 material. The results show that 1) oil lubrication can obviously improve the tribological properties of MoSi2, 2) the bigger the pv value, the greater the antifriction and the abrasive resistance of MoSi2 under oil lubrication, 3) with an increase in the pv value, the wear mechanism of MoSi2 material under dry sliding friction is the fatigue fracture and adhesive wear and 4) under oil lubrication the wear mechanism is mainly fatigue pitting.

  9. Investigation of the influential parameters of machining of AISI 304 stainless steel

    R A Mahdavinejad; S Saeedy

    2011-12-01

    Austenitic stainless steels are hard materials to machine, due to their high strength, high ductility and low thermal conductivity. The last characteristic results in heat concentration at the tool cutting edge. This paper aims to optimize turning parameters of AISI 304 stainless steel. Turning tests have been performed in three different feed rates (0.2, 0.3, 0.4 mm/rev) at the cutting speeds of 100, 125, 150, 175 and 200 m/min with and without cutting fluid. A design of experiments (DOE) and an analysis of variance (ANOVA) have been made to determine the effects of each parameter on the tool wear and the surface roughness. It is being inferred that cutting speed has the main influence on the flank wear and as it increases to 175 m/min, the flank wear decreases. The feed rate has the most important influence on the surface roughness and as it decreases, the surface roughness also decreases. Also, the application of cutting fluid results in longer tool life and better surface finish.

  10. An Electrochemical Processing Strategy for Improving Tribological Performance of Aisi 316 Stainless Steel Under Grease Lubrication

    Zou, Jiaojuan; Li, Maolin; Lin, Naiming; Zhang, Xiangyu; Qin, Lin; Tang, Bin

    2014-12-01

    In order to improve the tribological performance of AISI 316 stainless steel (316 SS) under grease lubrication, electrochemical processing was conducted on it to obtain a rough (surface texturing-like) surface by making use of the high sensitivity of austenitic stainless steel to pitting corrosion in Cl--rich environment. Numerous corrosion pits or micro-ditches acted as micro-reservoirs on the obtained surface. While the grease could offer consistent lubrication, and then improve the tribological performance of 316 SS. Tribological behaviors of raw 316 SS and the treated sample were measured using a reciprocating type tribometer sliding against GCr15 steel counterpart under dry and grease lubrication conditions. The results showed that the mass losses of the two samples were in the same order of magnitude, and the raw sample exhibited lower friction coefficient in dry sliding. When the tests were conducted under grease lubrication condition, the friction coefficients and mass losses of the treated sample were far lower than those of the raw 316 SS. The tribological performance of 316 SS under grease lubrication was drastically improved after electrochemical processing.

  11. Flaw tolerance of the AISI 403 end fittings of CANDU pressure tubes

    The fuel channel assemblies in a CANDU nuclear reactor locate and support the fuel bundles in the reactor core and form part of the Primary Heat Transport System. Heavy water coolant flows through each fuel channel and over the fuel bundles to remove the heat generated by the fission reaction. The pressure tube is rolled into the end fitting at each end by a mechanically rolled joint. At the other end of the end fitting there is a seal which is removed to allow on-power refuelling. Thus the material must have a yield strength sufficient to make a leak tight rolled joint and adequate corrosion resistance at the seal face. End fittings are made of AISI 403, a 12% Cr-0.1% steel, which has the combination of properties needed. However, at the strength needed to make the rolled joint the mils lateral expansion (MLE) measured in Charpy tests does not consistently meet toughness requirements of Section III of the ASME Boiler and Pressure Vessel Code. A program was undertaken to demonstrate, by bursting end fittings containing machined flaws, that there was a safety factor of at least 3 at its end-of-life condition. The crack shape used was based on that specified in Appendix G of Section III but the crack was made deeper so that it was located in the region of high residual stress in the rolled joint. The partial thickness defect, a machined slot 17 mm deep and 75 mm long was fatigue sharpened before bursting

  12. Surface Nanostructure Formations in an AISI 316L Stainless Steel Induced by Pulsed Electron Beam Treatment

    Yang Cai

    2015-01-01

    Full Text Available High current pulsed electron beam (HCPEB is an efficient technique for surface modifications of metallic materials. In the present work, the formations of surface nanostructures in an AISI 316L stainless steel induced by direct HCPEB treatment and HCPEB alloying have been investigated. After HCPEB Ti alloying, the sample surface contained a mixture of the ferrite and austenite phases with an average grain size of about 90 nm, because the addition of Ti favors the formation of ferrite. In contrast, electron backscattered diffraction (EBSD analyses revealed no structural refinement on the direct HCPEB treated sample. However, transmission electron microscope (TEM observations showed that fine cells having an average size of 150 nm without misorientations, as well as nanosized carbide particles, were formed in the surface layer after the direct HCPEB treatment. The formation of nanostructures in the 316L stainless steel is therefore attributed to the rapid solidification and the generation of different phases other than the steel substrate in the melted layer.

  13. Microstructural evolution of AISI 4340 steel during Direct Metal Deposition process

    Research highlights: → 4340 steel was successfully deposited using diode laser DMD system on mild steel. → Ferrite, martensite and cementite microstructural phases were identified in the clad. → Lattice parameters of identified phases are shorter than reported lattice parameters. → Microhardness of the clad decreases down the clad layers. → Decrease in microhardness corresponds to degree of tempering of martensite phase. - Abstract: In the current investigation AISI 4340 steel was laser deposited on a rolled mild steel substrate by Direct Metal Deposition (DMD) technology. The microstructural investigation of the clad was performed using optical and electron microscopes and X-ray diffraction techniques. The microstructure consisted of ferrite, martensite and cementite phases. Two types of martensite, lathe-type and plate-type, were observed in the microstructure. Decrease in microhardness values from the top layer to the alloy layer proves that the degree of tempering of the martensite phase increases in the same direction. The lattice parameters of the identified phases were found to be shorter than those reported in literature. The reported parameters in literature are from samples processed under equilibrium conditions.

  14. Effect of two synthetic lubricants on life of AISI 9310 spur gears

    Townsend, Dennis P.; Shimski, John

    1991-01-01

    Spur-gear fatigue tests were conducted with two lubricants using a single lot of consumable-electrode vacuum-melted (CVM) AISI 9310 spur gears. The gears were case carburized and hardened to Rockwell C60. The gear pitch diameter was 8.89 cm. The lot of gears was divided into two groups, each of which was tested with a different lubricant. The test lubricants can be classified as synthetic polyol-ester-based lubricants. One lubricant was 30 percent more viscous that the other. Both lubricants have similar pressure viscosity coefficients. Test conditions included a bulk gear temperature of 350 K, a maximum Hertz stress of 1.71 GPa at the pitch line, and a speed of 10,000 rpm. The surface fatigue life of gears tested with one lubricant was approximately 2.4 times that for gears tested with the other lubricant. The lubricant with the 30 percent higher viscosity gave a calculated elastohydrodynamic (EHD) film thickness that was 20 percent higher than the other lubricant. This increased EHD film thickness is the most probable reason for the improvement in surface fatigue life of gears tested with this lubricant over gears tested with the less viscous lubricant.

  15. Solidification Microstructure of AISI M2 High Speed Steel Manufactured by the Horizontal Continuous Casting Process

    Zhou, X. F.; Fang, F.; Jiang, J. Q.

    2011-01-01

    In the present work, AISI M2 high speed steel is produced by the horizontal continuous casting process. The difference of solidification microstructure in ingots by mould casting and continuous casting has been examined by means of scanning electron microscope (SEM), electron back-scatter diffraction (EBSD), transmission electron microscope (TEM) and high resolution electron microscope (HREM). The results show that the as-cast structure consists of iron matrix and networks of M2C eutectic carbides, which are greatly refined in the continuous casting ingot compared to the case of ingot by mould casting. Meanwhile, the morphology of M2C eutectic carbides changes from the plate-like shape into the fibrous one. Micro-twining and stacking faults are observed in the plate-like M2C, whereas they are rarely identified in the fibrous M2C. Based on the characteristic of morphology and microstructure, it is expected that the plate-like M2C is a faceted phase while the fibrous M2C is a non-faceted phase.

  16. Study of microcracks morphology produced by Vickers indentation on AISI 1045 borided steels

    In this work, we analyzed the roughness morphology of indentation microcracks produced by the Vickers microindentation in the iron boride Fe2B. Using the paste boriding process, the boride layers were formed at the surface of AISI 1045 steels. The diffusion processes were carried out with 5 mm of boron paste thickness over the substrate surface at three different temperatures (1193, 1223 and 1273 K) with two different time exposures. The indentations in each Fe2B layer were made using a constant load of 200 g at four different distances from the surface. The fracture behavior of the Fe2B borided phase is found to be brittle in nature. The profiles of microcracks formed at the corners of the indentations were obtained using the scanning electronic microscopy and were analyzed within the framework of fractal geometry. We found that all indentation microcracks display a self-affine invariance characterized by the same roughness (Hurst) exponent H = 0.8 ± 0.1. The effect of the self-affine roughness of indentation microcracks on the measured fracture toughness is discussed within the framework of the mechanics of self-affine cracks. It is pointed out that the arrest of indentation microcracks is controlled by the fractal fracture toughness, which for the Fe2B borided phase is found to be Kfc = 0.42 ± 0.02 MPa m0.75 at all distances from the surface

  17. Changes of surface layer of nitrogen-implanted AISI316L stainless steel

    The effects of nitrogen ion implantation into AISI316L stainless steel on friction, wear, and microhardness have been investigated at an energy level of 125 keV at a fluence of 1·1017 - 1·1018 N/cm2. The composition of the surface layer was investigated by RBS, XRD (GXRD), SEM and EDX. The friction coefficient and abrasive wear rate of the stainless steel were measured in the atmospheres of air, oxygen, argon, and in vacuum. As follows from the investigations, there is an increase in resistance to frictional wear in the studied samples after implantation; however, these changes are of different characters in various atmospheres. The largest decrease in wear was observed during tests in the air, and the largest reduction in the value of the friction coefficient for all implanted samples was obtained during tests in the argon atmosphere. Tribological tests revealed larger contents of nitrogen, carbon, and oxygen in the products of surface layer wear than in the surface layer itself of the sample directly after implantation

  18. Physicochemical and tribological characterization of titanium or titanium plus carbon implanted AISI M2 steel

    AISI M2 steel samples were implanted with 110 keV titanium ions at fluences ranging from 5x1016 to 4x1017Ti cm-2. Titanium plus carbon dual implantation was also studied. Titanium distribution profiles were determined using the 48Ti(p,γ)49V resonant nuclear reaction. The incorporation of carbon and oxygen from residual gases was studied as a function of titanium fluence and residual pressure using nuclear backscattering spectrometry at 5.7 and 7.5 MeV He+ ion energies respectively. A competition phenomenon between carbon and oxygen incorporation is pointed out. Analysis of the phases formed was performed using conversion electron Moessbauer spectroscopy. Fe(Ti) solid solution, a-FexTi100-x and superficial a-Fe-Ti-C amorphous phases were identified. Tribological tests involving a ball (Al2O3 or 52100) and disc contact were performed to characterize the friction behaviour of the implanted surface. It is shown that titanium plus carbon implantation leads to a reduction in the friction coefficient. The wear tracks and debris were examined using scanning electron microscopy and electron microprobe cartography. For the two types of balls a reduction in the wear track width was observed together with oxidation of the wear debris. The tribological improvement observed depends not only on the presence of the superficial a-Fe-Ti-C amorphous layer but also on the surface chemical reaction during the wear process. (orig.)

  19. Multiaxial isothermal and thermal cycling tests of AISI 316 L(N) austenitic steel tubes

    Multiaxial isothermal and thermal cycling tests of tubes made of AISI 316 L(N) austenitic steel are described. The thermal cycling load is generated by periodic induction heating of the outer tube wall and simultaneous continuous cooling by means of water of the inner tube wall. Temperature gradients in excess of 100 K/mm are produced which give rise to fatigue-induced cracks mainly in the inner tube wall. In the tube specimens subjected to isothermal loads, the equibiaxial stress condition typical of thermal cycling tests is to be simulated. This stress load is produced in tubes by superimposing a longitudinal load (tension/compression) upon a circumferential load (internal/external pressures). A new test rig has been built especially for this purpose. The design and mode of operation of the rig as well as the measurement systems, especially for the measurement of circumferential strain, are described. The reference base for the multiaxial tests are uniaxial alternating strain tests of small round solid specimens. The tests are conducted in the LCF range and consequently are strain controlled. The test results obtained to date are presented. In all tests, special attention is paid to the generation and propagation of fatigue-induced cracks. In this connection, the measurement of crack lengths is described. (author)

  20. Microstructural features of hot pressure bonding between stainless steel type AISI-304 L and ziracloy-2

    The diffusion zone formed after reaching quasi-equilibrium in hot pressure bonding between stainless steel type AISI-304 L and Zircaloy-2 under particular thermal and compressive conditions (1000-11000C and 2-3 atm) contains two distinct layers, each separately localized in the modified stainless steel and Zircaloy matrices. SEM, TEM, X-ray diffraction and microanalysis were used to identify the phase structure and composition of the two diffusion layers. The nature and distribution of phases found in the diffusion layers can be explained in connection with the diffusion mechanisms operating after the initial stages of bond formation and interface disappearance: (a) The strog zirconium diffusion promotes ferrite and ZrCr2 formation in a narrow zone located near the stainless steel matrix. (b) Iron and nickel diffusion over large distances in the Zircaloy matrix leads to the occurrence of a larger zone having a two-phase structure. The light grey phase consists of untransformed α-Zr and a small precentage of high-temperature β-Zr phase. The darker grey phase contains essentially a very high amount of intermetallic bct compounds Zr-Fe-Ni, Zr2Fe and Zr2Ni dispersed in the small residue of Zircaloy matrix. (orig.)

  1. Effects of Cr2N Precipitation on the Antibacterial Properties of AISI 430 Stainless Steel

    Je-Kang Du

    2016-03-01

    Full Text Available Based on their mechanical properties and good corrosion resistance, some commercial Ni-Cr stainless steels have been widely applied as biomaterials, including the austenitic 304 stainless steel, the austenitic 316 stainless steel, the duplex 2205 stainless steel, and the ferritic 430 stainless steel. In order to reduce the occurrence of infections resulting from biomaterial implants, instruments, and medical devices, Cu2+ and Ag2+ ions have been added onto biomaterials for increasing the antibacterial properties, but they are known to damage biofilm. The occurrence of nanoparticles can also improve the antibacterial properties of biomaterials through various methods. In this study, we used Escherichia coli and analyzed the microstructures of American Iron and Steel Institute (AISI 430 stainless steel with a 0.18 mass % N alloy element. During a lower temperature aging, the microstructure of the as-quenched specimen is essentially a ferrite and martensite duplex matrix with some Cr2N precipitates formed. Additionally, the antibacterial properties of the alloy for E. coli ranged from 3% to 60%, consistent with the presence of Cr2N precipitates. When aged at a lower temperature, which resulted in nano-Cr2N precipitation, the specimen possessed the highest antibacterial activity.

  2. Phase Transformations During the Low-Temperature Nitriding of AISI 2205 Duplex Stainless Steel

    Yan, Jing; Gu, Tan; Qiu, Shaoyu; Wang, Jun; Xiong, Ji; Fan, Hongyuan

    2015-02-01

    Liquid nitriding of type AISI 2205 duplex stainless steel was conducted at 723 K (450 °C), using one type of novel low-temperature liquid chemical thermo-treatment. The transformation of the nitrided surface microstructure was systematically studied. Experimental results revealed that a nitrided layer formed on the sample surface with the thickness ranging from 3 to 28 μm, depending on nitriding time. After the 2205 duplex stainless steel was subjected to liquid nitriding 723 K (450 °C) for less than 8 hours, the pre-existing ferrite region on the surface transformed into the expanded austenite (S phase) by the infusion of nitrogen atoms, most of which stay in the interstitial sites. Generally, the dominant phase of the nitrided layer was the expanded austenite. When the nitriding time prolonged up to 16 hours, some pre-existing ferrite in expanded austenite was decomposed and ɛ-nitride precipitated subsequently. When the treatment time went up to 40 hours, large amount of ɛ-nitride and CrN precipitates were observed in the pre-existing ferritic region in the expanded austenite. Furthermore, many nitrides precipitated from the pre-austenite region. Acicular nitride was identified by transmission electron microscopy. The thickness of the nitrided layer increased with increasing nitriding time. The growth of the nitrided layer is mainly due to nitrogen diffusion in accordance with the expected parabolic rate law. Liquid nitriding effectively increased the surface hardness of 2205 duplex stainless steel by a factor of 3.

  3. Duplex treatment of 304 AISI stainless steel using rf plasma nitriding and carbonitriding

    Surface of 304 AISI austenitic stainless steel has been modified using duplex treatment technique of nitriding and carbonitriding. A thick modified nitrided layer, of approximately 20 μm, has been achieved when rf inductively coupled plasma was adjusted at 450 W for processing time of only 10 min. After performing the nitrided layer, the nitrided samples were carbonitrided using the same technique at different acetylene partial pressure ratios ranges from 10% to 70%, the balance was pure nitrogen. Different amount of nitrogen and carbon species are diffused underneath the surface through the nitrided layer during carbonitriding process and are found to be gas composition dependent. The treated samples were characterized by glow discharge optical spectroscopy, X-ray diffractometry, scanning electron microscopy and Vickers microhardness tester. The microstructure of the duplex treated layer indicates the formation of γ-Fe4N, Fe3C, CrN and nitrogen-expanded austenite (γN). The thickness of the duplex treated layer increases with increasing the acetylene partial pressure ratio. The surface microhardness of duplex treated samples has been found to be gas composition dependent and increased by 1.29 fold in comparison to the nitrided sample.

  4. Investigations on Surface Milling of Hardened AISI 4140 Steel with Pulse Jet MQL Applicator

    Bashir, Mahmood Al; Mia, Mozammel; Dhar, Nikhil Ranjan

    2016-06-01

    In this article, an experimental investigation was performed in milling hardened AISI 4140 steel of hardness 40 HRC. The machining was performed in both dry and minimal quantity lubricant (MQL) conditions, as part of neat machining, to make a strong comparison of the undertaken machining environments. The MQL was impinged int the form of pulse jet, by using the specially developed pulse-jet-attachment, to ensure that the cutting fluid can be applied in different timed pulses and quantities at critical zones. The tool wear, cutting force and surface roughness were taken as the quality responses while cutting speed, table feed rate and flow rate of the pulse were considered as influential factors. The depth of cut was kept constant at 1.50 mm because of its less significant effects and the straight oil was adopted as cutting fluid in pulse-jet-MQL. The effects of different factors, on the quality responses, are analyzed using ANOVA. It is observed that MQL applicator system exhibits overall better performance when compared to dry milling by reducing surface roughness, cutting force and prolonging tool life but a flow rate of 150 ml/h has tremendous effects on the responses. This investigation and afterward results are expected to aid the industrial practitioner and researcher to adopt the pulse-MQL in high speed milling to prolong tool life, reduce tool wear, diminish cutting force generation and promote better surface finish.

  5. A study on the corrosion Properties of AISI type 316 Stainless Steel Weldment

    As a study on the corrosion property change at each part near weldment in AISI type 316 Stainless Steel, causes for the decrease of the corrosion resistance, change of the passive tendency and process of pitting were investigated by metallographic and electrochemical techniques. The equilibrium corrosion potentials, the pitting potentials and the current densities in the passive region in 3% NaCl solution at 19-20 .deg. C were studied with the potentiostatic anodic polarization curves. And the shapes of the pits were investigated as soon as the experiment for anodic polarization curve had been finished(i.e. in the transpassive region). The followings are the main conclusions drawn from the above experiments. The decrease of corrosion resistance is caused by the residual stress as well as the thermal effect. The passivity decreased at HAZ, and a certain correlation between the passive potential range and the current density in the passive region was revealed. Pits were most frequently generated at HAZ, and pitting initiated near the grain boundaries

  6. Kinetics of niobium carbide coating produced on AISI 1040 steel by thermo-reactive deposition technique

    There are a lot of technologically interesting characteristics of niobium carbide coating deposited by pack method which is the production of hard, wear-resistant, oxidation and corrosion resistant coating layer on the steel substrates. In the present study, the growth kinetics of niobium carbide layer deposited by thermo-reactive diffusion techniques in a solid medium on steel samples was reported. Niobium carbide coating treatment was performed on AISI 1040 steels in the powder mixture consisting of ferro-niobium, ammonium chloride and alumina at 1073, 1173 and 1273 K for 1-4 h. The presence of NbC and Nb2C phases formed on the surface of the steel substrates was confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analyses. Niobium carbide layer thickness ranges from 3.42±0.52 to 11.78±2.29 μm depending upon the treatment time and temperature. Layer growth kinetics was analyzed by measuring the depth of niobium carbide layer as a function of time and temperature. The kinetics of niobium carbide coating by pack method shows a parabolic relationship between carbide layer thickness and treatment time, and the activation energy for the process is estimated to be 91.257 kJ mol-1. Moreover, an attempt was made to investigate the possibility of predicting the contour diagram of niobium carbide layer variation and to establish some empirical relationships between process parameters and niobium carbide layer thickness

  7. Microstructure and oxidation behavior of high strength steel AISI 410 implanted with nitrogen ion

    Bandriyana, Ismoyo, Agus Hadi; Sujitno, Tjipto; Dimyati, A.

    2016-04-01

    Surface treatment by implantation with nitrogen-ion was performed on the commercial feritic high strength steel AISI 410 which is termed for high temperature applications. The aim of this research was focused on the surface modification to improve its high temperature oxidation property in the early stages. Ion implantation was carried out at acceleration energy of 100 KeV and ion current 10 mA for 30, 60 and 90 minutes. The samples were subjected to the high temperature oxidation test by means of thermogravimetry in a magnetic suspension balance (MSB) at 500 °C for 5 hours. The scanning electron microscopy (SEM), X-ray diffraction spectrometry (XRD) and Vickers Hardness measurement were used for sample characterization. The formation of ferro-nitride phase after implantation did not occur, however a thin layer considered to contain nitrogen interstitials was detected. The oxidation of both samples before and after implantation followed parabolic kinetics indicating inward growth of oxide scale characteristically due to diffusion of oxygen anions towards matrix surface. After oxidation test relativelly stable oxide scales were observed. Oxidation rates decreased proportionally with the increasing of implantation time due to the formation of oxide layer which is considered to be effectiv inhibitor for the oxygen diffusion.

  8. Microstructure analysis of AISI 304 stainless steel produced by twin-roll thin strip casting process

    2007-01-01

    The microstructure of AISI 304 austenite stainless steel fabricated by the thin strip casting process were investigated using optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD).The microstructures of the casting strips show a duplex structure consisting of delta ferrite and austenite. The volume fraction of the delta ferrite is about 9.74vol% at the center and 6.77vol% at the surface of the casting thin strip, in vermicular and band shapes. On account of rapid cooling and solidification in the continuous casting process, many kinds of inclusions and precipitates have been found. Most of the inclusions and precipitates are spherical complex compounds consisting of oxides, such as, SiO2, MnO, Al2O3,Cr2O3,and FeO or their multiplicity oxides of MnO·Al2O3,2FeO·SiO2, and 2MnO·SiO2. Many defects including dislocations and stacking faults have also formed during the rapid cooling and solidification process, which is helpful to improve the mechanical properties of the casting strips.

  9. Simultaneous enhancement of strength and ductility in cryogenically treated AISI D2 tool steel

    In this research, the effect of cryogenic treatment on microstructural evolution and mechanical properties enhancement of AISI D2 tool steel was investigated. Cryogenic treatment down to liquid nitrogen temperature (77 K) was added to the conventional heat treatment between hardening and tempering steps. Electron microscopy investigation showed higher volume fraction of fine carbides with average diameter below 1 μm indicating effective retardation in carbide coarsening process as a results of cryogenic treatment. A modification in types of carbides was also observed after cryogenic treatment. X-ray diffraction diagrams revealed transformation of retained austenite to martensite at cryogenic temperature. Weakening or removal of carbides peak in the X-ray diagram was considered as evidence of carbides different behavior at cryogenic temperature. Mechanical testing results indicated higher ultimate tensile strength, better ductility, and higher elastic modulus after cryogenic treatment. Analysis of stress–strain diagrams revealed different strain hardening behavior for cryogenically treated alloy when compared to the conventionally heat treated one. Fractography results confirmed strain hardening behavior and showed cleavage fracture for conventionally treated alloy but mixed cleavage–ductile fracture mode for cryogenically treated alloy. The improved mechanical properties after cryogenic treatment are interpreted in terms of the influence of higher volume fraction and uniform distribution of fine carbides in reducing the average active dislocations length and enhancement of the flow stress at any given plastic strain

  10. Corrosion of aluminium, stainless steels and AISI 680 nickel alloy in nitrogen-based fuels

    Kap, I.; Starostin, M.; Shter, G.E.; Grader, G.S. [Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa (Israel)

    2012-07-15

    Nitrogen-based compounds can potentially be used as alternative non-carbon or low-carbon fuels. Nevertheless, the corrosion of construction materials at high temperatures and pressures in the presence of such fuel has not been reported yet. This work is focused on the corrosion of AISI Al 6061, 1005 carbon steel (CS), 304, 316L, 310 austenitic stainless steels (SS) and 680 nickel alloy in highly concentrated water solution of ammonium nitrate and urea (ANU). The corrosion at 50 C and ambient pressure and at 350 C and 20 bar was investigated to simulate storage and working conditions. Sodium chloride was added to the fuel (0-5 wt%) to simulate industrial fertilizers and accelerated corrosion environment. Heavy corrosion of CS was observed in ANU solution at 50 C, while Al 6061, 304 and 316L SS showed high resistance both to uniform and pitting corrosion in ANU containing 1% of sodium chloride. Addition of 5% sodium chloride caused pitting of Al 6061 but had no influence on the corrosion of SS. Tests in ANU at 350 C and 20 bar showed pitting on SS 304 and 316L and 680 nickel alloy. The highest corrosion resistance was found for SS 310 due to formation of stable oxide film on its surface. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Susceptibility to stress corrosion in stainless steels type AISI 321 and 12X18H10T used in PWR type reactors (WWER)

    Titanium stabilized stainless steels have been utilized in sovietic pressurized water reactors (VVER) for avoid the susceptibility to Intergranular Corrosion (IGC) present in other austenitic stainless steels. However the Intergranular Corrosion resistance of this kind of materials has been questioned because of Intergranular Stress Corrosion Cracking failures (IGSCC) have been reported. This paper study the electrochemical behavior of the AISI 321 stainless steel in a H3BO3 Solution contaminated with chlorides and its susceptibility to Intergranular Corrosion.Electrochemical prediction diagrams of the stainless steels AISI 321 and 12X18H10T (sovietic) sensitized (600 Centigrade, 3 h.) were compared. Cylindrical and conical samples were used in Slow Strain Rate Tests (SSRT), to determine the susceptibility to Stress Corrosion Cracking (SCC) in AISI 321 and 12X18H10T stainless steels. The results obtained showed that the temperature of the solution is a very important factor to detect this susceptibility. Fractography studies on the fracture surfaces of the samples obtained in the SSRT at high temperature were realized. Corrosion velocities of both AISI 321 and 12X18H10T stainless steels were determined using conical samples in the CERT system at high temperature. E.D.A.X. analysis was employed in both AISI 321 and 12X18H10T stainless steels in order to explain the degree of sensitization. (Author)

  12. Transplante cardíaco no Instituto Dante Pazzanese de Cardiologia: análise da sobrevida

    ASSEF Marco Aurélio Salles

    2001-01-01

    Full Text Available CASUÍSTICA E MÉTODOS: Foram analisados, retrospectivamente, 80 transplantes cardíacos realizados no Instituto Dante Pazzanese de Cardiologia (IDPC no período de novembro de 1991 a agosto de 2000. Houve predomínio do sexo masculino em 70% dos casos e a idade variou de 7 a 69 anos, com média de 44,8 anos. Doze (15% pacientes se encontravam em prioridade, em uso de drogas inotrópicas endovenosas no momento do transplante. As etiologias determinantes da insuficiência cardíaca congestiva grave foram: miocardiopatia dilatada idiopática em 37,5%, miocardiopatia isquêmica em 33,75%, miocardiopatia chagásica em 17,5% e outras causas em 11,25%. Foram realizados 78 transplantes ortotópicos e 2 heterotópicos. A técnica empregada foi bicaval/bipulmonar em 63,75%, atrial em 27,5%, bicaval/unipulmonar em 6,25% e heterotópico em 2,5%. A mortalidade hospitalar (30 dias foi de 18,75%. RESULTADOS: A sobrevida para o transplante ortotópico em um ano foi de 72,7%, em cinco anos 61,5% e em sete anos 56,4%. A sobrevida após o transplante foi correlacionada com as variáveis idade, causa de óbito e sexo do doador, e pelo transplante ter sido ou não a primeira cirurgia cardíaca do paciente.

  13. Aneurisma ilíaco associado a fístula arteriovenosa Iliac aneurysm associated with arteriovenous fistula

    Daniel Mendes Pinto

    2007-09-01

    Full Text Available A ruptura dos aneurismas aorto-ilíacos para a veia ilíaca ou veia cava é uma complicação pouco comum. A hipertensão venosa leva a vários sinais e sintomas, o que dificulta o diagnóstico pré-operatório, tais como edema do membro inferior, dispnéia, hematúria, sinais de insuficiência renal ou cardíaca. Sopro abdominal é a chave do diagnóstico clínico, associado à massa pulsátil e dor abdominal. O reconhecimento da fístula arteriovenosa no pré-operatório é importante para o planejamento cirúrgico. Relatamos um caso de aneurisma da artéria ilíaca comum e interna direita associado a fístula para veia ilíaca comum, cursando, inicialmente, com edema do membro inferior direito e dispnéia, o que levou ao diagnóstico incorreto de trombose venosa profunda.Rupture of aortoiliac aneurysms into the iliac vein or vena cava is an uncommon complication. Many signs and symptoms develop as a result of venous hypertension, which makes preoperative diagnosis difficult, such as leg edema, dyspnea, hematuria, signs of renal or cardiac insufficiency. Abdominal bruit, associated with pulsatile mass and abdominal pain, is the key for clinical diagnosis. Preoperative recognition of arteriovenous fistula is important for surgical planning. We report a case of right internal and common iliac artery aneurysm associated with fistula into the common iliac vein. Initial symptoms were right leg edema and dyspnea, which induced to the incorrect diagnosis of deep vein thrombosis.

  14. Correlation between electrical properties and thermodynamic stability of ACoO3-δ perovskites (A= La, Pr, Nd, Sm, Gd)

    For perovskites with the general formula ACoO3-δ (A = La, Pr, Nd, Sm, and Gd) the influence of the A-site cation on the electrical conductivity, electronic structure, thermodynamic stability, and oxygen stoichiometry was studied. The perovskite oxide powders were produced by a combined citric acid and ethylenediaminetetraacetic acid complexing method. Ceramic specimens sintered at 1100 deg. C in air were single-phase perovskites. With increasing temperature, the electrical conductivity shows three discrete regimes. All compositions show semiconductivity up to a transition temperature of ∼300 deg. C-450 deg. C and then behave like metallic conductors. The activation energies for the semiconductivity, as well as the transition temperatures to the metallic-like conduction, decrease monotonically with increasing pseudocubic lattice parameters, i.e., with increasing ionic radii of the A cation. This behavior correlates with decreasing oxygen nonstoichiometry and increased thermodynamic stability. The highest conductivity and the lowest activation energy of 0.66 eV were found for LaCoO3-δ, which also had the lowest semiconductor-metal transition temperature at 269 deg. C, the lowest oxygen nonstoichiometry of δ= 0.008, and the highest Gibbs free energy change for the decomposition reaction of 42.37 kJ/mol at 850 deg. C. GdCoO3-δ had the highest oxygen nonstoichiometry with δ0.032, a high activation energy of 1.19 eV for the semiconductivity with a high transition temperature at 452 deg. C, and the lowest Gibbs free energy change of 26.54 kJ/mol at 850 deg. C. X-ray absorption spectroscopy data imply an increasing Co low-spin character with decreasing cation radius from La to Gd, while an increase in temperature increases the number of holes or Co 3d bandwidth. This correlates well with the electrical conductivity data.

  15. Dimensional characteristics of welds performed on AISI 1045 steel by means of the application of high power diode laser; Caracteristicas dimensionales de soldadura formadas sobre el acero AISI 1045 mediante la aplicacion del laser diodo de alta potencia

    Sanchez-Castillo, A.; Pou, J.; Lusquinos, F.; Quintero, F.; Soto, R.; Boutinguiza, M.; Saavedra, M.; Perez-Amor, M.

    2004-07-01

    The named High Power diode Laser (HPDL), emits a beam of optical energy generated by diode stimulation and offers the capability of supplying levels of power up to 6 kW. The objective of this research work was to study the main welding variables and their effects on dimensional characteristics of the beads performed by means of application of this novel laser. The results obtained, show that HPDL, is an energy source able to perform welds on AISI 1045 steel plates under conduction mode, without any kind of mechanized preparation, preheating or post-weld treatment and, without filler metal application. (Author) 16 refs.

  16. Comparative study of the microbiological corrosion among an AISI 304L and an API X65; Estudio comparativo de la corrosion microbiologica entre un AISI 304L y un API X65

    Diaz S, A.; Arganis J, C.; Luna C, P.; Carapia M, L. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Gonzalez F, E. [ITT, Toluca, Estado de Mexico (Mexico)

    2004-07-01

    Metallic samples of AISI 304L sensitized and API X65, were subjected to the action of an inoculated media with reductive sulphate microorganisms (SBR), carrying out electrochemical evaluations by means of the techniques of Polarization Resistance (RP), Tafel extrapolation (ET) and Electrochemical Noise (RE). The generated information was complemented with the analysis and diagnostic of the present damage in the surfaces exposed in both metals. The used electrochemical techniques allow to determine the corrosion velocities associated to each system, establishing that the uniform corrosion is not affected by the effect of the microorganisms; however, electrochemical noise, evidenced the formation of stings associated to the presence of bacteria. (Author)

  17. Evaluación del comportamiento a fatiga de una unión soldada a tope de acero AISI 1015//Evaluation of the fatigue behaviour of a butt welded joint of AISI 1015 steel

    Pavel Michel Almaguer‐Zaldivar; Roberto Andrés Estrada-Cingualbres

    2015-01-01

    Las uniones soldadas son un componente importante de una estructura, por lo que siempre es necesario conocer la respuesta de las mismas sometidas a cargas cíclicas. El objetivo de este trabajo es obtener la curva S-N de una unión soldada a tope de acero AISI 1015 y electrodo E6013 como material de aporte. Los ensayos a fatiga se realizaron de acuerdo a la norma ASTM en una máquina universal MTS810. Se utilizaron probetas de sección rectangular. El ciclo de carga fueasimétrico a tracción, con ...

  18. Evaluation of Microstructure and Mechanical Properties of Laser Beam Welded AISI 409M Grade Ferritic Stainless Steel%Evaluation of Microstructure and Mechanical Properties of Laser Beam Welded AISI 409M Grade Ferritic Stainless Steel

    A K Lakshminarayanan; V Balasubramanian

    2012-01-01

    The microstructure analysis and mechanical properties evaluation of laser beam welded AISI 409M ferritic stainless steel joints are investigated. Single pass autogeneous welds free of volumetric defects were produced at a welding speed of 3 000 mm/min. The joints were subjected to optical microscope, scanning electron fractographe, microhardness, transverse and longitudinal tensile, bend and charpy impact toughness testing. The coarse ferrite grains in the base metal were changed into dendritic grains as a result of rapid solidification of laser beam welds. Tensile testing indicates overmatching of the weld metal is relative to the base metal. The joints also exhibited acceptable impact toughness and bend strength properties.

  19. Influence of sintering atmosphere on the mechanical properties of steel P / M AISI 430L; Influencia de la atmosfera de sinterizacion en las propiedades mecanicas de los aceros P/M AISI 430L

    Iglesias, F. J.; Martinez, C.; Costes, M. T.; Ruiz, J. M.; Garcia, L. E.; Corpas, F.

    2014-04-01

    It has studied the stainless steel powder metallurgy AISI 430L. It has compared the sintering in two different atmospheres; in vacuum, and in an atmosphere containing nitrogen. It has developed a heat treatment with the aim of improving the mechanical properties. This has been done through microstructural modification of complex nitrides of iron and chromium precipitates during the phase of sintering. Physical properties have been evaluated and are been performing a microstructural analysis for microstructure related to the increase in mechanical properties. (Author)

  20. Comportamiento tribológico del acero AISI W112 con endurecimiento lineal mediante laser de ND:YAG.L. // Tribological behavior of AISI W112 steel with lineal hardening by means of ND:YAG laser.

    R. Sagaró

    2001-07-01

    Full Text Available Para disminuir el desgaste en los sistemas tribológicos frecuentemente se acostumbra a endurecer localmente aquellaszonas sometidas a desgaste. En el presente trabajo, para incrementar la dureza y la resistencia al desgaste del acero AISIW112 se empleó un láser de Nd:YAG. Las características de fricción y desgaste del acero AISI W112 en condiciones decontacto deslizante en fricción seca con el acero 65MN4 fueron evaluadas para tratamientos convencionales luego de suirradiación con láser. En el trabajo se presentan además las transformaciones que ocurren durante el tratamiento con láser,así como la influencia de los parámetros operacionales del láser en la profundidad de la capa endurecida y lascaracterísticas tribológicas. El trabajo experimental corroboró que la resistencia al desgaste del acero AISI W112 es variasveces superior en comparación con los tratamientos convencionales.Palabras claves: Comportamiento tribológico, endurecimiento lineal, tratamiento superficial con láser._______________________________________________________________________________Abstract.Diminishing wear in tribological systems is usually done by locally hardening those areas subject to wear. In this paper ispresented the increasing of hardness and resistance to wear of AISI W112 steel by means of a Nd:YAG laser. Thecharacteristics of friction and wear of AISI W112 steel under sliding contact in dry friction conditions with the 65MN4steel were evaluated for conventional treatments and after laser irradiation. In the work are presented the transformationsthat take place during the laser treatment, as well as the influence of the laser operational parameters in the depth of thehardened layer and the tribological characteristics. The experimental work corroborated that the resistance to wear of AISIW112 steel is several times superior in comparison with conventional treatments.Key words: Tribological behavior , lineal hardening, laser superficial

  1. ESTUDIO DE LA SINERGIA CORROSIÓN-EROSIÓN DE RECUBRIMIENTOS DUROS DE TiN Y CrN OBTENIDOS SOBRE ACERO AISI 1045

    HARVEY PAYÁN; WILLIAM APERADOR; ALEJANDRO VARGAS

    2008-01-01

    En este trabajo se presentan los resultados del estudio de los efectos sinergeticos de la corrosión-erosión en recubrimientos duros de TiN y CrN obtenidos sobre acero AISI 1045 por medio de la técnica de pulverización catódica con magnetrón y se hace una comparación con los resultados mostrados por un acero inoxidable comercial AISI 316 y el acero AISI 1045 sin recubrimiento. El proceso de deposición física de vapor (Physical Vapor Deposition), contribuye ampliamente a la aplicación de pelícu...

  2. Nondestructive measurement of the residual stress TiN thin film coated on AISI 304 substrate by x-ray stress analyzer

    Zhang, Y. K.; Feng, A. X.; Lu, J. Z.; Kong, D. J.; Tang, C. P.

    2006-01-01

    Titanium nitride films are deposited on AISI 304 steel with a hollow-cathode-discharge (HCD) ion-plating technique. The status of residual stresses in TiN thin film coated on AISI304 substrate by HCD is studied by x-ray diffraction stress analyzer. By analyzing morphology of the residual stress of TiN thin film at interface between TiN film and AISI 304 substrate, the adhering mechanism of TiN thin film is understood as follows: the mechanical interlocking had important contribution to the adhesion strength, the thermal stress is the major factor which resulting TiN thin film peeling off spontaneously. The results show that the value of thin film is -210MPa~-650Mpa, and the thermal stress is compressive, the intrinsic stress is tensile, origins of the residual stress are primarily discussed.

  3. Desarrollo de una escala de auto-reporte para medición de síntomas maníacos

    Karol Barrios; Jorge Rodríguez-Losada; Ricardo Sánchez

    2014-01-01

    Resumen Antecedentes. No existen instrumentos de auto-reporte en español para medir síntomas de trastorno bipolar. La perspectiva del paciente puede dar información complementaria de utilidad para el diagnóstico y manejo de la enfermedad. Objetivo. Desarrollar una escala de auto-reporte para medir síntomas maníacos, a partir de la escala EMUN. Materiales y métodos. Los ítems de la escala EMUN se transformaron a un lenguaje en primera persona por parte de dos psiquiatras. Esta versión prelimin...

  4. QUINOA (CHENOPODIUM QUINOA WILLD): DIGESTIBILIDADE IN VITRO, DESENVOLVIMENTO E ANÁLISE SENSORIAL DE PREPARAÇÕES DESTINADAS A PACIENTES CELÍACOS

    L. I. A. CASTRO; C. M. V. REAL; I. S. C. PIRES; C. V. PIRES; N. A.V.D. PINTO; Miranda, L. S.; B. C. ROSA; P. A. DIAS

    2008-01-01

    A quinoa (Chenopodium quinoa Willd) é um pseudocereal isento de glúten, oriundo dos Andes, onde tem sido cultivado há milhares de anos. O objetivo deste trabalho foi desenvolver e avaliar sensorialmente algumas preparações contendo quinoa em grãos, flocos e farinha, destinadas ao paciente celíaco, e determinar a digestibilidade in vitro de sua proteína, submetida ou ...

  5. Taponamiento cardíaco debido a perforación de la aurícula derecha por catéter venoso central

    V. Ramos Medina; I. Palomo Gómez; P.J. Aranda Granados; J.L. Palomo Rando; M. Salguero Villadiego

    2014-01-01

    El taponamiento cardíaco es una complicación devastadora de los catéteres venosos centrales. Se debe en general a que la punta del catéter alcanza indebidamente las cavidades cardíacas derechas. Para la correcta identificación en la autopsia por el patólogo forense es importante que a los pacientes fallecidos en los hospitales que van a ser sometidos a autopsia no se les retiren los dispositivos que tengan insertados, e igualmente que no se les retiren en la sala de autopsias hasta que no se ...

  6. Contribuição de decavanadato para os efeitos IN VIVO e IN VITRO de vanadato no músculo cardíaco

    Soares, S. S.

    2007-01-01

    Tese dout., Biologia - Fisiologia Animal, Universidade do Algarve, 2007 No presente estudo aborda-se a contribuição da espécie decamérica de vanadato nos efeitos tóxicos in vivo e in vitro de vanadato. Após administração intravenosa de decavanadato em Sparus aurata, o vanadato decamérico induz respostas nos marcadores de stresse oxidativo do tecido cardíaco distintas das promovidas pelo monovanadato, evidenciando a importância de considerar a contribuição dos diferentes olig...

  7. Renovar novelando: lo apolíneo y lo dionisíaco en Las cerezas del cementerio de Gabriel Miró

    Thion Soriano-Mollá, Dolores

    2010-01-01

    Con Las cerezas del cementerio, Gabriel Miró se enfrenta a un doble reto, renovar la novela por los cauces de la subjetividad, el intimismo y el lirismo así como dar vida literaria a uno de los planteamientos centrales de El nacimiento de la tragedia de Nietzsche, la relación entre lo apolíneo y lo dionisíaco desde un punto de vista vital, estético y ontológico a través de su protagonista, el joven Félix Valdivia, quien encarna el triunfo de Dioniso.

  8. Investigação de lipofuscina em miócitos cardíacos de camundongos após tratamento com oxamniquine

    Maria Luiza Silveira Mello; Carmen S. Bertuzzo

    1984-01-01

    A fluorescencia natural devida à presença de corpos de lipofuscina foi pesquisada em miócitos cardíacos de camundongos adultos jovens tratados com oxamniquine. O objetivo foi buscar uma evidência de indução de envelhecimento celular precoce, com base em dados prévios de acentuação poliploidia, promovida pela droga. Comparando o miocárdio dos camundongos tratados com animais contrôle jovens e velhos, não foi observada a presença de lipofuscina nos seus miócitos. Isto possivelmente se deva a um...

  9. Mecanismo del daño mecánico letal por reoxigenación en miocitos cardíacos

    Ruiz Meana, Marisol

    1998-01-01

    Los miocitos cardíacos sometidos a hipoxia prolongada presentan un gran aumento en la concentración de Ca2+ citosólico. Durante la reoxigenación, la reactivación de la producción energética mitocondrial en presencia de Ca2+ citosólico elevado provoca una activación exagerada de la contractilidad celular que puede llegar a deformar irreversiblemente el citoesqueleto y romper la membrana celular. Este fenómeno, conocido como hipercontractura, es el responsable de la muerte celular que se produ...

  10. Resistance spot welding joints of AISI 316L austenitic stainless steel sheets: Phase transformations, mechanical properties and microstructure characterizations

    Highlights: • Resistance spot welding of AISI 316L stainless steel sheets. • Microstructure prediction by the use of Schaeffler and Pseudo-binary diagrams. • Non-equilibrium phases including skeletal, acicular and lathy delta ferrite formed. • Mechanical characterization of weld nuggets including peak load and failure energy. • Different failure modes were found at various welding currents. - Abstract: In this paper, we aim to optimize welding parameters namely welding current and time in resistance spot welding (RSW) of the austenitic stainless steel sheets grade AISI 316L. Afterward, effect of optimum welding parameters on the resistance spot welding properties and microstructure of AISI 316L austenitic stainless steel sheets has been investigated. Effect of welding current at constant welding time was considered on the weld properties such as weld nugget size, tensile–shear load bearing capacity of welded materials, failure modes, failure energy, ductility, and microstructure of weld nuggets as well. Phase transformations that took place during weld thermal cycle were analyzed in more details including metallographic studies of welding of the austenitic stainless steels. Metallographic images, mechanical properties, electron microscopy photographs and micro-hardness measurements showed that the region between interfacial to pullout mode transition and expulsion limit is defined as the optimum welding condition. Backscattered electron scanning microscopic images (BE-SEM) showed various types of delta ferrite in weld nuggets. Three delta ferrite morphologies consist of skeletal, acicular and lathy delta ferrite morphologies formed in resistance spot welded regions as a result of non-equilibrium phases which can be attributed to the fast cooling rate in RSW process and consequently, prediction and explanation of the obtained morphologies based on Schaeffler, WRC-1992 and Pseudo-binary phase diagrams would be a difficult task

  11. Analyses of oxide films grown on AISI 304L stainless steel and Incoloy 800HT exposed to supercritical water environment

    Fulger, Manuela; Mihalache, Maria; Ohai, Dumitru; Fulger, Stefan; Valeca, Serban Constantin

    2011-08-01

    Supercritical water (SCW) is being considered as a cooling medium for the next generation nuclear reactors because it provides high thermal efficiency and plant simplification. However, materials corrosion has been identified as a critical problem due to the oxidative nature of supercritical water. Thus, for safety using of these nuclear reactor systems a systematic study of candidate materials corrosion is needed. As in other high temperature environments, corrosion in SCW occurs by the growth of an oxide layer on the materials surface. The current work aims to evaluate oxidation behavior of AISI 304L SS and Incoloy 800HT in water at supercritical temperatures in the range 723-873 K under a pressure of 25 MPa for up to 1680 h. After exposure to deaerated supercritical water, the samples were investigated using gravimetry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Oxide films grown on these materials have a layered structure with an outer layer consisting of a mixture of iron oxide/iron-nickel spinel oxides and an inner layer consisting of chromium oxide in the case of Incoloy 800HT and nickel-chromium spinel oxide in the case of AISI 304L SS. The mass gains for Incoloy 800HT at all temperatures were small, while comparatively with AISI 304L SS which exhibited higher oxidation rates. In the same time the results obtained by EIS indicate the best corrosion resistance of oxides grown on Incoloy 800HT surface.

  12. Characterization of passive film formed on AISI 316L stainless steel after magnetoelectropolishing in a broad range of polarization parameters

    Rokosz, Krzysztof; Hryniewicz, Tadeusz [Politechnika Koszalinska, Division of Surface Electrochemistry, Raclawicka 15-17, PL 75-620 Koszalin (Poland); Raaen, Steiner [NTNU Trondheim, Institute of Physics, Trondheim (Norway)

    2012-09-15

    The aim of the paper is to present the changes in the surface film composition on AISI 316L stainless steel (SS) after electropolishing (EP) and magnetoelectropolishing (MEP) in a broad range of the process conditions. The X-ray photoelectron spectroscopy surface analyses were performed to reveal the effect of MEP. The EP process has been performed under natural convection (in a stagnant electrolyte), much above the polarization plateau. A series of experiments were carried out on AISI 316L SS samples in accordance with the five-level composite rotary statistical plan with the variables being the magnetic field intensity B (mT), and the anodic current density i (A dm{sup -2}). XP high resolution spectra have been obtained on AISI 316L SS surface concerning Fe 2p, Cr 2p, O 1s, S 2p, P 2p, and C 1s, respectively. The Cr:Fe ratio regarding both metallic M and compound X was also studied and calculated. At the end, the summary results of Cr/Fe = f(B, i) in relation to the corrosion potential, have been compared. The conclusions, concerning the selection of MEP process conditions, regarding the optimum Cr/Fe ratio and corrosion behavior, have been formulated. It was found the Cr:Fe ratio well correlates with the pitting corrosion potential. MEP process can modify not only the rate of dissolution to a determined extent, but also control the corrosion behavior and Cr:Fe ratio results. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Analyses of oxide films grown on AISI 304L stainless steel and Incoloy 800HT exposed to supercritical water environment

    Fulger, Manuela, E-mail: manuela.fulger@nuclear.ro [Institute for Nuclear Research Pitesti, POB 78, Campului Street, No. 1, 115400 Mioveni (Romania); Mihalache, Maria; Ohai, Dumitru [Institute for Nuclear Research Pitesti, POB 78, Campului Street, No. 1, 115400 Mioveni (Romania); Fulger, Stefan [University Politechnica Bucharest, Splaiul Independentei Street, No. 313, Bucharest 060042 (Romania); Valeca, Serban Constantin [University of Pitesti, Targul din Vale Street, No. 1, 110040 Pitesti (Romania)

    2011-08-15

    Supercritical water (SCW) is being considered as a cooling medium for the next generation nuclear reactors because it provides high thermal efficiency and plant simplification. However, materials corrosion has been identified as a critical problem due to the oxidative nature of supercritical water. Thus, for safety using of these nuclear reactor systems a systematic study of candidate materials corrosion is needed. As in other high temperature environments, corrosion in SCW occurs by the growth of an oxide layer on the materials surface. The current work aims to evaluate oxidation behavior of AISI 304L SS and Incoloy 800HT in water at supercritical temperatures in the range 723-873 K under a pressure of 25 MPa for up to 1680 h. After exposure to deaerated supercritical water, the samples were investigated using gravimetry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Oxide films grown on these materials have a layered structure with an outer layer consisting of a mixture of iron oxide/iron-nickel spinel oxides and an inner layer consisting of chromium oxide in the case of Incoloy 800HT and nickel-chromium spinel oxide in the case of AISI 304L SS. The mass gains for Incoloy 800HT at all temperatures were small, while comparatively with AISI 304L SS which exhibited higher oxidation rates. In the same time the results obtained by EIS indicate the best corrosion resistance of oxides grown on Incoloy 800HT surface.

  14. Evaluación del grado de sensibilización en el acero inoxidable AISI

    González, O.

    2003-12-01

    Full Text Available Austenitic stainless steel, when heat-treated at 550-850 °C, became susceptible to intergranular corrosion in acids. This phenomenon, know as sensitization, it is result from the precipitation of chrome carbides in the grain boundary, making these areas less resistant to corrosion. Two different electrochemical reactivation tests are compared with a destructive test and related to the classification of its respective microstructures. It was established a quantitative methodology to evaluate the degree of sensitization in AISI 304 and also to compare the correspondence of the results with the data of the automatic and portable EPR device for non-destructive field measurement of the degree of sensitization. The used electrochemical techniques were the EPR (Electrochemical Potentiokinetic Reactivation or single loop test and the PRP (Pasivation Reactivation Potentiokinetic or double loop test. The destructive test used was boiling, 120 h ferric sulfate-50 % sulfuric acid, according to the standard practices ASTM A-262 practices B. The classifications of each structures were according to the standard practices ASTM A-262 practices B.

    El acero inoxidable austenítico, cuando se calienta en un rango de temperatura entre 550 y 850 °C es susceptible a corrosión intergranular en ácidos. Este fenómeno, conocido como sensibilización, es resultado de la precipitación de carburos de cromo en el límite de grano, haciendo esas áreas menos resistentes a la corrosión. Se comparan dos pruebas diferentes de reactivación electroquímica con una prueba destructiva, relacionándolas con su respectiva microestructura. Se estableció una metodología cuantitativa para evaluar el grado de sensibilización del acero AISI 304 y se comparó con los datos generados de una herramienta no destructiva de campo, automática y portátil, para medir el grado de sensibilización. Las técnicas electroquímicas usadas fueron: la EPR (Reactivación electroqu

  15. Effect of Cl– on the corrosive wear of AISI 321 stainless steel in H2SO4 solution

    Yanliang Huang; Xiaoxia Jiang; Sizuo Li

    2003-06-01

    The effect of Cl– on the corrosive wear behaviour of AISI 321 stainless steel in H2SO4 solution was studied via the corrosive wear rate, the load bearing capacity of passive film and the relationship between pitting and corrosive wear. There is a critical load at natural potential, below which the corrosive wear rate is slightly lowered by Cl–, while above which is increased. At natural potential there are more pits at low load than that at a higher one in the wear tracks and the pits are also deeper. The load bearing capacity is lowered by Cl– at passive region and then the corrosive wear rate increased.

  16. THE EVALUATION OF TOOL WEAR IN THE MACHINING AISI 1050 STEEL HARDENED UP TO 53 HRC WITH COATED CARBIDE TOOL

    MOTORCU, Ali Rıza

    2006-01-01

    In this study, the machining of AISI 1050 steel which is hardened up to 53 HRC is carried out with two carbide tool materials (three layer coated carbide of TP100 containing Ti (C, N)/Al2O3/TiN and (multi layer coated carbide of TP1000 containing Ti (C, N)/Al2O3/ Ti (C, N)/TiN. Cutting tests are performed with constant depth of cut and feed rate under dry cutting conditions. The flank wear is examined using an optical microscope. Tool life curves and Taylor Tool Life Equation constants (n, C)...

  17. The influence of the martensitic transformation on the fatigue of an AISI type 316 metastable stainless steel

    The influence of the martensitic transformation on the process of pulse tension fatigue of a AISI type 316 metastable stainless steel was studied at 250 and 1960c. The fatigue tests were performed on annealed and cold worked specimens in order to separate the effects of static transformation, dynamic transformation and work hardening. The fatigue limits obtained from the corresponding Wohler curves were compared for the different test conditions. The results showed that the fatigue is not affected by the dynamically induced martensite. On the other hand the static martensite, previously induced, appears to decrease the resistance to fatigue. The reasons for these effects are discussed. (Author)

  18. Effect of martensite to austenite reversion on the formation of nano/submicron grained AISI 301 stainless steel

    The martensite to austenite reversion behavior of 90% cold rolled AISI 301 stainless steel was investigated in order to refine the grain size. Cold rolled specimens were annealed at 600-900 deg. C, and subsequently characterized by scanning electron microscopy, X-ray diffraction, Feritscope, and hardness measurements. The effects of annealing parameters on the formation of fully-austenitic nano/submicron grained structure and the mechanisms involved were studied. It was found that annealing at 800 deg. C for 10 s exhibited the smallest average austenite grain size of 240 ± 60 nm with an almost fully-austenitic structure.

  19. Effect of martensite to austenite reversion on the formation of nano/submicron grained AISI 301 stainless steel

    Karimi, M.; Najafizadeh, A. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Kermanpur, A., E-mail: ahmad_k@cc.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Eskandari, M. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2009-11-15

    The martensite to austenite reversion behavior of 90% cold rolled AISI 301 stainless steel was investigated in order to refine the grain size. Cold rolled specimens were annealed at 600-900 deg. C, and subsequently characterized by scanning electron microscopy, X-ray diffraction, Feritscope, and hardness measurements. The effects of annealing parameters on the formation of fully-austenitic nano/submicron grained structure and the mechanisms involved were studied. It was found that annealing at 800 deg. C for 10 s exhibited the smallest average austenite grain size of 240 {+-} 60 nm with an almost fully-austenitic structure.

  20. Dimensional characteristics of welds performed on AISI 1045 steel by means of the application of high power diode laser

    The named High Power diode Laser (HPDL), emits a beam of optical energy generated by diode stimulation and offers the capability of supplying levels of power up to 6 kW. The objective of this research work was to study the main welding variables and their effects on dimensional characteristics of the beads performed by means of application of this novel laser. The results obtained, show that HPDL, is an energy source able to perform welds on AISI 1045 steel plates under conduction mode, without any kind of mechanized preparation, preheating or post-weld treatment and, without filler metal application. (Author) 16 refs

  1. The Effects of Cutting Tool Coating on the Surface Roughness of AISI 1015 Steel Depending on Cutting Parameters

    Hasan GÖKKAYA

    2006-01-01

    The effects of a number of cutting tool coating materials on the surface quality of workpieces, depending on various cutting parameters, were investigated. AISI 1015 steel was processed without cooling on a lathe using 4 different cemented carbide cutting tools, i.e. uncoated, coated with AlTiN and coated with TiAlN using the PVD technique, and one with 3-layer coatings (outermost being TiN) applied by the CVD technique. Among the cutting parameters, the depth of cut was kept constan...

  2. AISI 304 stainless steel disintegration using a water jet intensified by mechanical vibrations with frequency of 20kHz

    Lehocká, D.; Klich, Jiří; Foldyna, Josef; Hloch, Sergej; Cárach, J.

    Belgrade: TEAM International Society, Faculty of Mechanical Engineering, University of Belgrade, 2015 - (Sedmak, A.), s. 320-323 ISBN 978-86-7083-877-2. [International Scientific and Expert Conference TEAM 2015 /7./. Belgrade (RS), 15.10.2015-16.10.2015] R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : pulsating water jet * disintegration * mass material removal * AISI 304 stainless steel Subject RIV: JQ - Machines ; Tools http://johanyak.hu/files/u1/publi/G_J_Survey_on_Intrusion_TEAM_2015.pdf

  3. EBSD karakterisering av et austenittisk rustfritt AISI 304 stål under in situ deformasjon ved ulike temperaturer

    Wenn, Maia

    2014-01-01

    Denne masteroppgaven kartlegger martensittdannelsen i et austenittisk rustfritt stål som følge av ytre påkjenninger i form av temperatur og spenning. Dette er gjort ved hjelp av in situ deformasjon i skanning elektronmikroskop (SEM) i kombinasjon med diffraksjon av tilbakespredte elektroner (EBSD). Stålet som er undersøkt er AISI 304, som er et austenittisk rustfritt stål med en fullstendig austenittisk struktur. Stålet ble undersøkt ved tre forskjelli...

  4. Effect of rare earth elements on microstructure and oxidation behaviour in TIG weldments of AISI 316L stainless steel

    The influence of rare earth addition in weld metal, on the microstructure and oxidation behaviour of AISI 316L stainless steel in dry air under isothermal condition at 973 K for 240 h is reported. Rare earth metal (REM) doped weld metal zone exhibits better oxidation resistance during isothermal holding as compared to base metal and undoped weld metal zone of 316L. Presence of both Ce and Nb in weld metal shows superior oxidation resistance than with Ce alone. TIG weld microstructures are presented by optical microscopy. The morphologies of the scales and nature of their adherence to the alloy substrates, and scale spallation have been characterized by SEM and EDAX

  5. Effect of CO2 laser cutting process parameters on edge quality and operating cost of AISI316L

    Eltawahni, Hayat; Hagino, M.; Benyounis, Khaled; Inoue, T; Olabi, Abdul-Ghani

    2012-01-01

    Laser cutting is a popular manufacturing process utilized to cut various types of materials economically. The width of laser cut or kerf, quality of the cut edges and the operating cost are affected by laser power, cutting speed, assist gas pressure, nozzle diameter and focus point position as well as the work-piece material. In this paper CO2 laser cutting of stainless steel of medical grade AISI316L has been investigated. Design of experiment (DOE) was implemented by applying Box-Behnken de...

  6. Investigation And Optimization Of EDM Process Of AISI 4140 Alloy Steel Using Various Tool Electrodes: A Review Paper

    Kishor Lal ,

    2014-11-01

    Full Text Available The purpose of this research work is to determine the optimized settings of key machining factors like pulse on time, discharge current and duty cycle for AISI 4140 alloy steel using various tool electrodes. The output responses will be measured are material removal rate (MRR,surface roughness(SR and tool wear rate(TWR. Mathematical models are proposed for the above are L27 orthogonal array. The micro structural changes in the work piece after machining process will also be examined by the use of SEM.

  7. Characteristics of sintered HA coating deposited by chemical method on AISI 316L substrate

    Graphical abstract: Potentiodynamic polarization curves of various conditions tested in Ringer’s solution at 37 ± 1 °C. - Highlights: • Sintering resulted in a well-dispersed HA-coating. • Sintering of HA resulted in a slightly higher surface roughness. • Sintering improved the coating/substrate adhesion. • Sintering of HA-coated samples possessed higher corrosion resistance. - Abstract: Hydroxyapatite (HA) coating is widely applied for biomaterials because of its chemical similarity to the mineral component of bones. The bioactive nature of HA coating enhances the formation of strong chemical bonds with surrounding bones. The present work is aimed at investigating the effects of sintering at 500, 600 and 700 °C on the crystallization and adhesive properties of HA coating, deposited by chemical method on AISI 316L stainless steel substrate. The properties of HA coating were studied by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and standard tensile adhesion test. In addition, the corrosion behavior after heat treatments was evaluated in Ringer’s solution at 37 °C as a simulated body fluid. The results refer to a good enhancement of the crystallization of the HA coating sintered at 700 °C. The adhesive strength of as-coated (AC) material increased from 8.3 MPa to 12.2, 16.8 and 19.8 MPa after sintering at 500, 600 and 700 °C, respectively. The corrosion rate of the as-coated material reduced sharply from 0.405 to 0.094 μA cm−2 after sintering at 700 °C

  8. Modeling of liquid phase formation by solid-solid interaction of Zircaloy and AISI 316 Steel

    Two models were developed in order to describe the eutectic interaction between Zircaloy-4 and AISI 316 stainless steel, in the temperature range 1000 - 1300 C degree. The aim of the models is to simulate what could happen in the nucleus of a power reactor in an eventual transient high temperature accident. Entry data correspond to the instantaneous positions of the Zircaloy-4 / liquid and stainless steel / liquid inter phases, obtained from experimental data. The hypothesis corresponding to the first model are: that the liquid phase growths by diffusion of the main elements of each alloy in the liquid (Fe and Zr), that there is no interaction between these elements during diffusion, that the diffusion or convection in the solid state is not considered, and that volume changes are negligible during fusion and interdiffusion. Concentrations at the solid/liquid inter phases and the effective diffusion coefficients for Zr and Fe in the liquid can be obtained. The model allows to calculate the formation kinetics for the liquid phase as measured by Zr oxide layers of 0, 10, 20 and 50 microns initial width, formed on the Zircaloy in order to simulate the operating conditions of a reactor. Incubation times for the onset of the reaction, observed experimentally in pre-oxidized samples, were calculated taking into account the oxide dissolution. The second model considers diffusion of Fe in Zircaloy since Fe is a fast diffuser in Zr. As in the first model, concentrations at the solid/liquid inter phases as well as the effective diffusion coefficients for Fe and Zr in the liquid, are calculated. The results obtained in this case depend on the Fe concentration at the solid/liquid interphase at the solid Zircaloy side, and on the Fe diffusivity in Zircaloy-4, which was estimated by the Fe diffusivity in Zr. (author)

  9. On low temperature ion nitriding of austenitic stainless steel AISI 316

    R. Russev

    2007-11-01

    Full Text Available Purpose: The purpose of this paper is to discuss some problems concerning the extremely high values of the nitride layer hardness and the features of so called S-phase which are formed after low-temperature ion nitriding of high-alloyed austenitic (austenitic-ferritic steels.Design/methodology/approach: The investigations are performed mainly by using of ray diffraction method after ion nitrided 316 (AISI steel.Findings: As a result of the work some data, concerning the structure and substructure, the phase composition of the S-phase, crystal lattice, the broadening of diffraction reflexes, mechanism of transformation of γ'- phase into S-phase, its high hardness etc. of the nitrided layer are obtained. It could be concluded that S-phase could be classified as a modified γ’-phase. The extremely high values of the hardness could be explained by the high nitrogen concentration in the solid solution and by the presence of increased density of the defects in the austenitic volume, which is transformed in the new S-phase.Research limitations/implications: The potencionstatic investigations of the electrochemical properties of the nitriding probes, performed by us, confirmed the data, obtained by the literature, but this problem will be discussed in some of the next publications.Originality/value: The high micro- and macro-deformations of the lattice of S-phase could be explained by the considerable registered expansions and the angle replacements of the slope (ψ on the ray diffraction maxima. The registered macro deformations could reach immense values, in the range of (1.4 – 2.1�10-2, which corresponds to macro deformations around 1900 – 2300 MPa (if we accept, for the austenite, the usual module of elasticity of 2.1�105 MPa. For such final decision it is necessary to obtain also some other confirmation facts.

  10. Friction Characteristics of Nitrided Layers on AISI 430 Ferritic Stainless Steel Obtained by Various Nitriding Processes

    Hakan AYDIN

    2013-03-01

    Full Text Available The influence of plasma, gas and salt-bath nitriding techniques on the friction coefficient of AISI 430 ferritic stainless steel was studied in this paper. Samples were plasma nitrided in 80 % N2 + 20 % H2 atmosphere at 450 °C and 520 °C for 8 h at a pressure of 2 mbar, gas nitrided in NH3 and CO2 atmosphere at 570 °C for 13 h and salt-bath nitrided in a cyanide-cyanate salt-bath at 570 °C for 1.5 h. Characterisation of nitrided layers on the ferritic stainless steel was carried out by means of microstructure, microhardness, surface roughness and friction coefficient measurements. Friction characteristics of the nitrided layers on the 430 steel were investigated using a ball-on-disc friction-wear tester with a WC-Co ball as the counter-body under dry sliding conditions. Analysis of wear tracks was carried out by scanning electron microscopy. Maximum hardness and maximum case depth were achieved on the plasma nitrided sample at 520 ºC for 8 h. The plasma and salt-bath nitriding techniques significantly decreased the average surface roughness of the 430 ferritic stainless steel. The friction test results showed that the salt-bath nitrided layer had better friction-reducing ability than the other nitrided layers under dry sliding conditions. Furthermore, the friction characteristic of the plasma nitrided layer at 520 ºC was better than that of the plasma nitrided layer at 450 °C.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3819

  11. Recubrimientos de (ti,aln sobre acero aisi 4140 por sputtering reactivo

    DANNA GARCIA

    2007-01-01

    Full Text Available Empleando la técnica de Pulverización catódica con radiofrecuencia y magnetrón (Magnetron Sputtering RF, se prepararon películas de (Ti,AlN sobre sustratos de acero AISI 4140. Se utilizó un blanco formado con polvos metálicos de Ti y Al, con composición nominal 60% Ti y 40% Al (porcentaje en átomos y una razón de presiones parciales de nitrógeno - argón, PN2/PAr de 0,1 aproximadamente; la temperatura del sustrato se varió entre 260 y 330 ºC y el tiempo de deposición entre 2 y 4,5 horas para obtener películas con diferentes espesores. La composición química de las películas se determinó mediante la técnica de energía dispersada de rayos X (EDX, y su topografía mediante microscopía de fuerza atómica (AFM. Igualmente se midió micro dureza, y se determinó su comportamiento electroquímico mediante espectroscopia de impedancia electroquímica EIS y ensayos TAFEL. Las películas obtenidas presentaron granos globulares, uniformes y de pequeño diámetro, con características electroquímicas de protección al sustrato frente a procesos de corrosión.

  12. Espectro óculo-aurículo-vertebral em pacientes com defeitos cardíacos congênitos

    Rafael Fabiano Machado Rosa

    2010-10-01

    Full Text Available FUNDAMENTO: Há poucos estudos avaliando a frequência do espectro óculo-aurículo-vertebral (EOAV nos pacientes com defeitos cardíacos congênitos (DCC. OBJETIVO: Verificar a frequência do EOAV em uma amostra de pacientes com malformações cardíacas graves. MÉTODOS: Avaliamos uma coorte prospectiva de pacientes com DCC, admitidos em uma unidade de terapia intensiva (UTI cardiopediátrica no Brasil. O diagnóstico de EOAV foi feito com base em dados clínicos, considerando critérios padrões. Os pacientes que preenchiam esses critérios foram submetidos ao cariótipo de alta resolução com bandamento GTG e hibridização fluorescente in situ para a microdeleção 22q11.2. O teste exato de Fisher (P < 0,05 foi usado para as análises estatísticas. RESULTADOS: Durante o período de avaliação, 330 pacientes foram hospitalizados pela primeira vez na UTI, mas trinta deles não participaram deste estudo. Dos 300 pacientes que constituíram a amostragem final, o EOAV foi verificado em três casos (1%. Todos apresentaram estudos citogenéticos normais. CONCLUSÃO: O EOAV parece ser uma condição frequente em pacientes com DCC. Contudo, não podemos excluir a possibilidade de que a frequência de EOAV encontrada em nosso estudo possa ter sido subestimada devido à baixa taxa de detecção pré-natal de DCC e ao acesso limitado dos pacientes ao tratamento médico apropriado em nosso meio. Estudos prospectivos futuros com critérios clínicos bem definidos e pacientes com defeitos leves e graves serão importantes para avaliar o papel do EOAV na população em geral de indivíduos com malformações cardíacas.

  13. Characterization of transcriptional profiles of MA-ACS1 and MA-ACO1 genes in response to ethylene, auxin, wounding, cold and different photoperiods during ripening in banana fruit.

    Choudhury, Swarup Roy; Roy, Sujit; Sengupta, Dibyendu N

    2008-12-01

    The ripening-specific genes MA-ACS1 (Musa acuminata ACC synthase1) and MA-ACO1 (M. acuminata ACC oxidase 1) are regulated in response to a wide variety of factors. Here, we have studied the differential transcript accumulation pattern and protein levels of MA-ACS1 and MA-ACO1 genes in response to ethylene, auxin, wounding and low temperature in preclimacteric banana fruit. We have shown that exogenous application of ethylene and auxin induced the expression of MA-ACS1, while MA-ACO1 showed marginal expression following ethylene treatment in preclimacteric stage. Auxin did not induce MA-ACO1 expression. Thus, auxin-treated banana fruits showed lower ethylene production rate as compared to ethylene-treated fruits. Conversely, wounding and cold treatment down-regulated the expression of both the genes and thus inhibited ethylene production. Furthermore, we have detected a GCC-box putative ethylene-responsive element (ERE)- and an auxin-responsive element (ARE)-specific DNA-binding activity in the banana pulp and studied the ethylene and auxin responsive characteristics of the GCC-box and ARE (TGTCTC) containing synthetic promoter fragments. In addition, we have detected an enhanced ethylene production rate and expression level of MA-ACS1 and MA-ACO1 genes along with a strong GCC-box-specific DNA-binding activity following exposure to constant dark period for 8d at the preclimacteric stage. Together, our study provides interesting information about the regulation of expression of MA-ACS1 and MA-ACO1 genes in response to various factors during ripening in banana fruit, which may have physiological relevance concerning ethylene biosynthesis during post-harvest conditions. PMID:18554749

  14. Influencia de los regímenes de lubricación en la vida de la herramienta y el acabado superficial del fresado de aceros endurecidos AISI D2 y AISI D6

    Maritza Mariño-Cala

    2015-10-01

    Full Text Available Se realizó un análisis de la calidad superficial y la vida de la herramienta durante el mecanizado con altas velocidades de los aceros endurecidos AISI D2 y AISI D6, en dos regímenes de lubricación. Los ensayos fueron realizados en un centro de mecanizado MORI SEIKI SV 40 y se emplearon herramientas intercambiables de metal duro recubiertas. La evaluación de la calidad superficial se realizó mediante el monitoreo off-line de la rugosidad superficial media Ra en el sentido del avance y perpendicular a este. La progresión del desgaste en las herramientas se analizó a través de un estereoscopio montado en conjunto con una cámara fotográfica digital interconectada a un programa analizador de imágenes. La aplicación de corte seco en operaciones de fresado de aceros endurecidos con altas velocidades apunta hacia una disminución de los costos del proceso asociados al uso de líquidos lubricantes y su reciclaje y a un aumento de la calidad superficial de la pieza y la vida de la herramienta.

  15. Estudio y diseño de un sistema de monitorización del ritmo cardíaco basado en un PSoC y un dispositivo móvil inteligente

    Hernández Gómez, Elías

    2015-01-01

    Este trabajo tiene como objetivo diseñar un sistema que permita monitorizar el ritmo cardíaco, apoyándose en un circuito diseñado especialmente para medir y acondicionar dicha señal con un dispositivo de tipo PSoC, que también será usado para la recopilación de datos, y una aplicación de Android para monitorizarlos. Por tanto, se plantean los siguientes objetivos para realizar el sistema propuesto:  -Estudiar el sensor necesario para medir el pulso cardíaco, seleccionando los ...

  16. Análisis de la calidad del registro de paro cardíaco en casos de responsabilidad médico legal en médicos generales, 1999-2007

    Barragán, Gabriel; Navarro Vargas, José Ricardo; Marulanda, Nathalie; Eslava Schmalbach, Javier Hernando

    2010-01-01

    Antecedentes. El registro del paro cardíaco es una actividad que se debe acompañar en la reanimación cerebro cardio pulmonar. En Colombia no existe un formato de registro oficial de paro cardiorrespiratorio, lo que dificulta la investigación en reanimación y la conducción de los procesos de responsabilidad médica que se deriven de esta atención. Objetivo. Analizar la calidad del registro de paro cardíaco en casos de responsabilidad médico legal iniciada a médicos generales que tuvieron as...

  17. Dynamics and performance of the free electron laser at Super-Aco with a harmonic RF cavity set on 500 MHz

    This work is dedicated to the development of the potentialities of the free electron laser that has been installed on the storage ring Super-Aco at Orsay university. We have studied the dynamics of the electron beam inside a harmonic RF cavity set on 500 MHz. The impact of the geometric characteristics of the optical cavity on the transverse overlapping between laser radiation and the electron beam has been studied in details. An important part of the work has been the assessment of the optical characterization of the dielectric multi-layer mirrors of the cavity. For that purpose a complete system has been designed to assess the changes in optical properties of mirrors during laser operation. Another important part of this work was the study of the interaction process between laser radiation and the electron bunch leading to saturation. This interaction process has been simulated through a new model and some predictions given by this model have been successfully confronted to experimental data. The installation of the harmonic RF cavity has led to a significant increase of the laser radiation gain and the value of the mean power of the laser radiation has reached 300 mW. An interesting application of this technique is the generation of high energy gamma photons through Compton backscattering. A collimated 35 MeV-energy photon beam has been produced at Super-Aco with a rate of 5.106 photons per second. (A.C.)

  18. Advance Payment ACO Model

    U.S. Department of Health & Human Services — The Advance Payment Model is designed for physician-based and rural providers who have come together voluntarily to give coordinated high quality care to the...

  19. ACO - Ant Colony Optimization

    Žumer, Viljem; Brest, Janez; Pešl, Ivan

    2015-01-01

    Ant colony optimization is a relatively new approach to solving NP-Hard problems. It is based on the behavior of real ants, which always find the shortest path between their nest and a food source. Such behavior can be transferred into the discrcte world, were real ants are replaced by simple agents. Such simple agents are placed into the environment where different combinatorial problems can be solved In this paper we describe an artificial ant colony capable of solving the travelling salesm...

  20. Optimization of Process Parameters in Turning Operation of AISI - 1016 Alloy Steels with CBN Using Artificial Neural Networks

    K.Mani lavanya

    2013-11-01

    Full Text Available We report the development of a predictive model based on artificial neural network (ANN for the estimation of Surface roughness of AISI-1016 during orthogonal turning with CBN insert tool. Turningexperiments were conducted at different cutting conditions on a PSG-A141 conventional lathe using CBN uncoated insert as tool with ISO designations SNMG-120408 and AISI-1016 as work piece using full factorial design. Cutting speed (v, feed rate (f, depth ofcut (d, were the input parameters of the machining experiment as well as theANN prediction model while the Surface roughness (Ra was the output variable.The neural networks with feed-forward and back-propagation learning algorithms were designed using the MATLAB Neural Network Toolbox. An optimal ANN architecture with the Levenberg-Marquardttraining algorithm and a learning rate of 0.1 was obtained using Taguchi method of experimental design. With the optimized ANN architecture, parametric study was conducted to relate the effect ofeach turning parameters on the surface roughness.The resultsobtained conclude that ANN is reliable method and it can be readily applied to different metal cutting processes with greater confidence.

  1. Pengaruh variasi Holding Time Pada Perlakuan Panas Quench Annealing Terhadap Sifat mekanik dan Mikro Struktur Pada Baja mangan AISI 3401

    Boby Endi Kurniawan

    2014-03-01

    Full Text Available 800x600 Baja mangan merupakan salah satu baja penting yang digunakan dalam industri dan memiliki aplikasi yang luas karena mempunyai wear resisten yang baik, kemampuan work hardening yang tinggi dengan ketangguhan dan keuletan yang tinggi. Tujuan dari penelitian ini adalah menganalisa pengaruh perubahan struktur mikro dan sifat mekanik pada baja mangan austenitic AISI 3401 .Penelitian baja mangan austenitk AISI 3401 ini dilakukan dengan perlakuan quench annneling pada temperature 10000C dengan empat variasi waktu tahan 30 menit, 60 menit, 120 menit yang diikuti pendinginan cepat media air, dan tanpa perlakuan. Kemudian dilakukan pengujian metalografi untuk mengetahui struktur mikro, uji kekerasan untuk mengetahui sifat mekanik dan uji XRD untuk menganalisis fasa hasil dari perlakuan quench annealing pada temperature 10000C dengan menggunakan empat variasi tersebut. Hasil penelitian diperoleh adanya pembentukan karbida dan austenit pada semua spesimen. Sedangkan hasil uji kekerasan yang didapatkan nilai yang tertinggi adalah pada waktu tahan 30 menit, yaitu 27 HRc Normal 0 false false false IN X-NONE X-NONE MicrosoftInternetExplorer4

  2. The effect of preheat and post weld heat treatment on the laser weldability of AISI 420 martensitic stainless steel

    Highlights: • Laser welding of martensitic stainless steel is a very challenging process. • An effect of post weld treatment on properties of laser weldment was investigated. • The desired properties of weldment have been achieved by controlling cooling rate. • The post-weld treatment could be responsible for reducing microcrack propagation. - Abstract: The martensitic stainless steels are widely used in many industries with their excellent mechanical properties and sufficient corrosion resistance. These steels usually are used for a wide range of applications like nuclear power plants, steam generators, mixer blades, pressure vessels, turbine blades, surgical tools, instrument manufacturing and so on. Contrary to good mechanical and corrosion properties of martensitic steels, poor weldability and cold cracking sensitivity are major problems that are faced in joining of these steels. In this study, the weldability of AISI 420 (X30Cr13) martensitic stainless steel by CO2 laser beam welding method has been investigated. Effects of pre and post weld heat treatments on mechanical properties and microstructure of laser welded AISI 420 martensitic stainless have also been determined. As a conclusion, it was determined that pre and post weld heat treatments sufficiently improved the mechanical properties of the welds

  3. Phase transformations in an AISI 410S stainless steel observed in directional and laser-induced cooling regimes

    Milton Sergio Fernandes de Lima

    2012-02-01

    Full Text Available The applications of the chromium ferritic stainless steel AISI 410S have been considerably increased in the last years in many technical fields as chemical industries and oil or gas transportation. However, the phase transformation temperatures are, currently, unknown for this alloy. The aim of this work is to determine the alpha to gamma transformation temperatures of the AISI 410S alloy in different cooling conditions and to analyze them using continuous cooling theory. In order to achieve different cooling rates and thermal conditions, two complementary techniques were used: Bridgman furnace crystal growth and laser remelting technique. The measured solidification temperature was around 1730 and 1750 K. Plate-like and dendritic austenite precipitates were obtained in solid-state phase using growth rates between 5 and 10 µm/s in directional growth experiments. Only plate-like austenite phase was observed in the experiments using growth rates above 100 µm/s. The appearance of dendrites, with the consequent segregation of the elements, can be previously determined by the microstructure modeling currently proposed. Massive austenite can be produced from 0.3 to 10 mm/s rates at temperatures between 1100-1300 K. The structure might be less sensitive to corrosion because this phase is produced without microsegregation.

  4. Irradiation creep and swelling of AISI 316 to exposures of 130 dpa at 385 to 4000C

    The creep and swelling of AISI 316 stainless steel have been studied at 385 to 4000C in EBR-II to doses of 130 dpa. Most creep capsules were operated at constant stress and temperature but mid-life changes in these variable were also made. This paper concentrates on the behavior of the 20% cold-worked condition but five other conditions were also studied. Swelling at ≤000C was found to lose the sensitivity to stress exhibited at higher temperatures while the creep rate was found to retain linear dependencies on both stress and swelling rate. The creep coefficients extracted at 4000C agree with those found in other experiments conducted at higher temperatures. In the temperature range of ≤4000C, swelling is in the recombination-dominated regime and the swelling rate falls strongly away from the ∼1%/dpa rate observed at higher temperatures. These lower rates of creep and swelling, coupled with the attainment of high damage levels without failure, encourage the use of AISI 316 in the construction of water-cooled fusion first walls operating at temperatures below 4000C. 23 refs., 8 figs

  5. Tribological properties of CrN coatings deposited by nitro-chromizing treatment on AISI D2 steel

    Durmaz, M., E-mail: mdurmaz@sakarya.edu.tr; Abakay, E.; Sen, U.; Sen, S. [Department of Metallurgical and Materials Engineering, Engineering Faculty, Sakarya University, Esentepe Campus, 54187 Sakarya (Turkey); Kilinc, B. [Department of Metallurgical and Materials Engineering, Institute of Arts and Sciences, Sakarya University, Esentepe Campus, 54187 Sakarya (Turkey)

    2015-03-30

    In this work, the wear test of uncoated and chromium nitride coated AISI D2 cold work tool steel against alumina ball realized at 0.1 m/s sliding speeds and under the loads of 2.5N, 5N and 10N. Steel samples were nitrided at 575°C for 8 h in the first step of the coating process, and then chromium nitride coating was performed thermo-reactive deposition technique (TRD) in a powder mixture consisting of ferro-chromium, ammonium chloride and alumina at 1000°C for 2 h. Nitro-chromized samples were characterized by X-Ray diffraction analysis (XRD), scanning electron microscopy (SEM), micro-hardness and ball on disk wear tests. The coating layer formed on the AISI D2 steel was compact and homogeneous. X-ray studies showed that the phase formed in the coated layer is Cr{sub 2}N. The depth of the layer was 8.15 µm. The average hardness of the layer was 2160±15 HV{sub 0.025}. For uncoated and chromium nitride materials, wear rate increased with increasing load. The results of friction coefficient and wear rate of the tested materials showed that the CrN coating presents the lowest results.

  6. Characteristics of the nitrided layer formed on AISI 304 austenitic stainless steel by high temperature nitriding assisted hollow cathode discharge

    Highlights: • AISI 304 austenite steel was nitrided at high temperatures in short time. • It could critically reduce time compared with low temperature nitriding. • The nitrided layer was mainly composed of nitrogen expanded austenite. • It could improve pitting corrosion resistance in NaCl solution. - Abstract: A series of experiments have been conducted on AISI 304 stainless steel using a hollow cathode discharge assisted plasma nitriding apparatus. Specimens were nitrided at high temperatures (520–560 °C) in order to produce nitrogen expanded austenite phase within a short time. The nitrided specimen was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, potentiodynamic polarization and microhardness tester. The corrosion properties of nitrided samples were evaluated using anodic polarization tests in 3.5% NaCl solution. The nitrided layer was shown to consist of nitrogen expanded austenite and possibly a small amount of CrN precipitates and iron nitrides. The results indicated that rapid nitriding assisted hollow cathode discharge not only increased the surface hardness but also improved the corrosion resistance of the untreated substrate

  7. Influence of Surface Preparation on the Kinetics of Controlled Gas-Nitrided AISI H13 Steels Used in Extrusion Dies

    Akhtar, S. S.; Arif, A. F. M.; Yilbas, B. S.; Sheikh, A. K.

    2010-04-01

    In the aluminum extrusion practice, gas nitriding represents an important factor in enhancing the service life of AISI H13 steel dies. It is observed that if the die-bearing surface is not adequately prepared before nitriding, a nonuniform and shallow nitrided layer develops with reduced hardening effect. The focus of this paper is to investigate the influence of different surface conditions in terms of roughness on the kinetics of nitrided layer developed during gas-nitriding process under controlled nitriding potential. Four samples made of AISI H13 steel properly heat treated (quenched and tempered) were considered: without surface preparation, ground, polished, and lapped. All the samples were gas nitrided under the same conditions and examined after being nitrided. The nitrided layers were characterized using different techniques including optical microscopy, scanning electron microscopy, x-ray diffraction analysis, energy dispersive spectrometry mapping, and microhardness analysis. It was found that the surface preparation prior to nitriding significantly enhanced the nitriding kinetics, which in turn resulted in even and deep nitrided case depth. This provided high load-bearing capacity due to increased and deep hardening effect as compared to unprepared sample. A thinner and uniform compound layer with well-resolved phases was achieved in comparison with unprepared sample.

  8. TRIBOLOGICAL BEHAVIORS OF PLASMA NITRIDED AISI 316 LN TYPE STAINLESS STEEL IN AIR AND HIGH VACUUM ATMOSPHERE AT ROOM TEMPERATURE

    A.DEVARAJU

    2010-09-01

    Full Text Available In this work, tribological behaviors of the plasma nitrided AISI 316 LN type austenitic stainless steel specimens (both pins and rings have been analyzed. The experiments have been conducted in high vacuum and in air atmosphere using Vacuum based high temperature Pin-on-disc tribometer. The tribological parameters such as friction coefficient and wear resistance have been analyzed by Origin graphs. The wear mechanisms involved have been identified by recording surface morphology on the wear track and pin surface through scanning electron microscope (SEM and Optical profilometer. The self mating of AISI 316 LN type stainless steel (316LN exhibits strong adhesion between the contact surfaces and severe surface damage both in air and in vacuum atmosphere. But, the self mating of Plasma Nitrided 316LN (CrN/CrN reveals mild wear till the CrN coating peeled off from the pin surface. It has also been proved that Plasma Nitrided (CrN layer on 316 LN ring was wear resistant layer when it issliding against the untreated 316 LN pin in air and high vacuum atmosphere.

  9. Improving the Adhesion Resistance of the Boride Coatings to AISI 316L Steel Substrate by Diffusion Annealing

    Campos-Silva, I.; Bernabé-Molina, S.; Bravo-Bárcenas, D.; Martínez-Trinidad, J.; Rodríguez-Castro, G.; Meneses-Amador, A.

    2016-07-01

    In this study, new results about the practical adhesion resistance of boride coating/substrate system formed at the surface of AISI 316 L steel and improved by means of a diffusion annealing process are presented. First, the boriding of AISI 316 L steel was performed by the powder-pack method at 1173 K with different exposure times (4-8 h). The diffusion annealing process was conducted on the borided steels at 1273 K with 2 h of exposure using a diluent atmosphere of boron powder mixture. The mechanical behavior of the boride coating/substrate system developed by both treatments was established using Vickers and Berkovich tests along the depth of the boride coatings, respectively. Finally, for the entire set of experimental conditions, the scratch tests were performed with a continuously increasing normal force, in which the practical adhesion resistance of the boride coating/substrate system was represented by the critical load. The failure mechanisms developed over the surface of the scratch tracks were analyzed; the FeB-Fe2B/substrate system exhibited an adhesive mode, while the Fe2B/substrate system obtained by the diffusion annealing process showed predominantly a cohesive failure mode.

  10. Study of the tensile behavior of AISI type 316 stainless steel using acoustic emission and infrared thermography techniques

    Thodamrakandy Haneef

    2015-07-01

    Full Text Available Acoustic emission (AE and infrared thermography technique (IRT have been used to study the tensile behavior of AISI type 316 stainless steel. Strain rates of tensile testing were varied from 1.4 × 10−3 s−1 to 1.4 × 10−2 s−1. AE root mean square voltage increases with increase in strain rate due to the increase in source activation. Dominant frequency of the AE signals generated during different regions of tensile deformation has also been used to compare the results for different strain rates. The dominant frequency increases from elastic region to around 590 kHz during work hardening and 710 kHz around ultimate tensile strength (UTS for all the strain rates. Temperature changes during different regions of deformation are monitored using infrared thermography. The temperature rise in the work hardening region is found to approximately increase linearly with time and from the slopes of the linear regression analyses the rate of temperature rise in the work-hardening region is obtained which is found to be very sensitive to strain rates. From the experimental results an empirical equation that relates the rate of temperature increase with strain rate and thermal hardening coefficient is obtained. The correlation between the variation of AE dominant frequency and temperature rise during different deformation regions provided better insight into the tensile behavior of AISI type 316 SS for different strain rates.

  11. High temperature oxidation behavior of austenitic stainless steel AISI 304 in steam of nanofluids contain nanoparticle ZrO2

    The objective of this study is to evaluate high temperature oxidation behavior of austenitic stainless steel SS 304 in steam of nanofluids contain nanoparticle ZrO2. The oxidation was performed at high temperatures ranging from 600 to 800°C. The oxidation time was 60 minutes. After oxidation the surface of the samples was analyzed by different methods including, optical microscope, scanning electron microscope (SEM) and X-ray diffraction (XRD). X-ray diffraction examination show that the oxide scale formed during oxidation of stainless steel AISI 304 alloys is dominated by iron oxide, Fe2O3. Minor element such as Cr2O3 is also appeared in the diffraction pattern. Characterization by optical microscope showed that cross section microstructure of stainless steel changed after oxidized with the oxide scale on the surface stainless steels. SEM and x-ray diffraction examination show that the oxide of ZrO2 appeared on the surface of stainless steel. Kinetic rate of oxidation of austenite stainless steel AISI 304 showed that increasing oxidation temperature and time will increase oxidation rate

  12. Resistance Spot Weldability of Dissimilar Materials: BH180-AISI304L Steels and BH180-IFT123 Steels

    Fatih Hayat

    2011-01-01

    In this study, resistance spot weldability of 180 grade bake hardening steel (BH180), 7123 grade interstitial free steel (IF7123) and 304 grade austenitic stainless steel (AISI304L) with each other was investigated. In the joining process, electrode pressure and weld current were kept constant and six different weld time were chosen. Microstructure, microhardness, tensile-shear properties and fracture types of resistance spot welded joints were examined. In order to characterize the metallurgical structure of the welded joint, the microstructural profile was developed, and the relationship between mechanical properties and microstructure was determined. The change of weld time, nugget diameter, the HAZ (heat affected zone) width and the electrode immersion depth were also investigated. Welded joints were examined by SEM (scanning electron microscopy) images of fracture surface. As a result of the experiment, it was determined that with increasing weld time, tensile shear load bearing capacity (TLBC) increased with weld time up to 25 cycle and two types of tearing occurred. It was also determined that while the failure occurred from IF side at the BHIS0+IF7123 joint, it occurred from the BH180 side at the BHIS0+AISI304L joint.

  13. Wear behavior of the surface alloyed AISI 1020 steel with Fe-Nb-B by TIG welding technique

    Kilinc, B.; Durmaz, M.; Abakay, E.; Sen, U.; Sen, S.

    2015-03-01

    Weld overlay coatings also known as hardfacing is a method which involves melting of the alloys and solidification for applied coatings. Recently hardfacing by welding has become a commonly used technique for improvement of material performance in extreme (high temperature, impact/abrasion, erosion, etc.) conditions.In the present study, the coatings were produced from a mixture of ferrous niobium, ferrous boron and iron powders in the ranges of -45µm particle size with different ratio. Fe12Nb5B3 and Fe2NbBalloys were coated on the AISI 1020 steel surface by TIG welding. The phases formed in the coated layer are Fe2B, NbB2, NbFeB and Fe0,2 Nb0,8 phases. The hardness of the presence phases are changing between 1689±85 HV0.01, and 181±7 HV0.1. Microstructural examinations were realized by optical and scanning electron microscopy. The wear and friction behaviors of Fe12Nb5B3 and Fe2NbB realized on the AISI 1020 steel were investigated by the technique of TIG welding by using ball-on-disk arrangement against alumina ball.

  14. Wear behavior of the surface alloyed AISI 1020 steel with Fe-Nb-B by TIG welding technique

    Kilinc, B., E-mail: bkilinc@sakarya.edu.tr; Durmaz, M.; Abakay, E. [Department of Metallurgical and Materials Engineering, Institute of Arts and Sciences, SakaryaUniversity, Esentepe Campus, 54187Sakarya (Turkey); Sen, U.; Sen, S. [Department of Metallurgical and Materials Engineering, Engineering Faculty, Sakarya University, Esentepe Campus, 54187 Sakarya (Turkey)

    2015-03-30

    Weld overlay coatings also known as hardfacing is a method which involves melting of the alloys and solidification for applied coatings. Recently hardfacing by welding has become a commonly used technique for improvement of material performance in extreme (high temperature, impact/abrasion, erosion, etc.) conditions.In the present study, the coatings were produced from a mixture of ferrous niobium, ferrous boron and iron powders in the ranges of -45µm particle size with different ratio. Fe{sub 12}Nb{sub 5}B{sub 3} and Fe{sub 2}NbBalloys were coated on the AISI 1020 steel surface by TIG welding. The phases formed in the coated layer are Fe{sub 2}B, NbB{sub 2}, NbFeB and Fe0,2 Nb{sub 0,8} phases. The hardness of the presence phases are changing between 1689±85 HV{sub 0.01}, and 181±7 HV{sub 0.1}. Microstructural examinations were realized by optical and scanning electron microscopy. The wear and friction behaviors of Fe{sub 12}Nb{sub 5}B{sub 3} and Fe2NbB realized on the AISI 1020 steel were investigated by the technique of TIG welding by using ball-on-disk arrangement against alumina ball.

  15. Characterization and expression profiles of MaACS and MaACO genes from mulberry (Morus alba L.)%桑树MaACS和MaACO基因的鉴定和表达模式研究

    Chang-ying LIU; Shu-mei HAN; Cheng LU; Mao-de YU; Rui-hua LÜ; Jun LI; Ai-chun ZHAO; Xi-ling WANG; Umuhoza DIANE; Xiao-hong WANG; Chuan-hong WANG; Ya-sheng YU

    2014-01-01

    1-Aminocyclopropane-1-carboxylic acid synthase (ACS) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) are encoded by multigene families and are involved in fruit ripening by catalyzing the production of ethylene throughout the development of fruit. However, there are no reports on ACS or ACO genes in mulberry, partly because of the limited molecular research background. In this study, we have obtained five ACS gene sequences and two ACO gene sequences from Morus Genome Database. Sequence alignment and phylogenetic analysis of MaACO1 and MaACO2 showed that their amino acids are conserved compared with ACO proteins from other species. MaACS1 and MaACS2 are type I, MaACS3 and MaACS4 are type II, and MaACS5 is type III, with different C-terminal se-quences. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) expression analysis showed that the transcripts of MaACS genes were strongly expressed in fruit, and more weakly in other tissues. The expression of MaACO1 and MaACO2 showed different patterns in various mulberry tissues. MaACS and MaACO genes demon-strated two patterns throughout the development of mulberry fruit, and both of them were strongly up-regulated by abscisic acid (ABA) and ethephon.%研究目的:分离和鉴定桑树中参与乙烯生物合成的酶的编码基因MaACS 和MaACO,研究其表达模式。创新要点:基于最新公布的桑树基因组数据库数据,获得5个MaACS 基因和2个MaACO 基因,对其进行了生物信息分析,同时鉴定了其在不同桑树组织中、不同发育时期桑椹中和不同激素作用下的表达模式。研究方法:通过生物信息学方法筛选和鉴定基因,利用荧光定量逆转录聚合酶链式反应(qRT-PCR)分析基因的表达量。重要结论:MaACS 和MaACO 基因在根、茎、叶等不同组织中呈现出不同的表达模式,在桑椹发育过程中呈现出两种表达模式,其表达量被脱落酸和乙烯利上调。

  16. Estimation of Fatigue Life of Laser Welded AISI304 Stainless Steel T-Joint Based on Experiments and Recommendations in Design Codes

    Lambertsen, Søren Heide; Damkilde, Lars; Kristensen, Anders Schmidt;

    2013-01-01

    In this paper the fatigue behavior of laser welded T-joints of stainless steel AISI304 is investigated experimentally. In the fatigue experiments 36 specimens with a sheet thickness of 1 mm are exposed to one-dimensional cyclic loading. Three different types of specimens are adopted. Three groups...

  17. In vitro performance of prefilled CO2 absorbers with the Aisys(®).

    Hendrickx, Jan F A; De Ridder, Simon P A J; Dehouwer, Alexander; Carette, Rik; De Cooman, Sofie; De Wolf, Andre M

    2016-04-01

    Low flow anesthesia increases the use of CO2 absorbents, but independent data that compare canister life of the newest CO2 absorbents are scarce. Seven different pre-packed CO2 canisters were tested in vitro: Amsorb Plus, Spherasorb, LoFloSorb, Medisorb, Medisorb EF, LithoLyme, and SpiraLith. CO2 (160 mL min(-1)) flowed into the tip of a 2 L breathing bag that was ventilated with a tidal volume of 500 mL, a respiratory rate of 10/min, and an I:E ratio of 1:1 using the controlled mechanical ventilation mode of the Aisys (®) (GE, Madison, WI, USA). In part I, canister life of each brand (all of the same lot) was tested with 12 different fresh gas flows (FGF) ranging from 0.25 to 4 L min(-1). In part II, canister life of six canisters each of two different lots of each brand were tested with a 350 mL min(-1) FGF. Canister life is presented as "FCU", fractional canister usage, the fraction of a canister used per hour, and is defined for the inspired CO2 concentration (FICO2) that denotes exhaustion. In part III, canister life per 100 g fresh granule content was calculated. FCU decreased linearly with increasing FGF. The relative position of the FCU-FGF curves of the different brands depends on the FICO2 threshold because the exhaustion rate (the rate of rise once FICO2 starts to increase) differs among the brands. Intra-lot variability was 18 % or less. The different prepacks can be ranked according their efficiency (least to most efficient) as follows: Amsorb Plus = Medisorb EF < LoFloSorb < Medisorb = Spherasorb = LithoLyme < SpiraLith (all for an FICO2 threshold = 0.5 %). Canister life per 100 g fresh granule content is almost twice as long when LiOH is used as the primary absorbent. The most important factors that determine canister life of prepacks in a circle breathing system are the chemical composition of the canister, the absolute amount of absorbent present in the canister, and the FICO2 replacement threshold. The use of the

  18. Microstructure, mechanical properties and chemical degradation of brazed AISI 316 stainless steel/alumina systems

    Paiva, O.C. [Instituto Superior de Engenharia do Porto (ISEP), Rua Dr. Antonio Bernardino de Almeida 431, 4200-072 Porto (Portugal)], E-mail: omp@isep.ipp.pt; Barbosa, M.A. [Instituto de Engenharia Biomedica (INEB), Rua do Campo Alegre, 823, 4150-180 Porto (Portugal); Faculdade de Engenharia da Universidade do Porto (FEUP), Rua Roberto Frias s/n, 4200-465 Porto (Portugal)

    2008-05-15

    The main aims of the present study are simultaneously to relate the brazing parameters with: (i) the correspondent interfacial microstructure, (ii) the resultant mechanical properties and (iii) the electrochemical degradation behaviour of AISI 316 stainless steel/alumina brazed joints. Filler metals on such as Ag-26.5Cu-3Ti and Ag-34.5Cu-1.5Ti were used to produce the joints. Three different brazing temperatures (850, 900 and 950 deg. C), keeping a constant holding time of 20 min, were tested. The objective was to understand the influence of the brazing temperature on the final microstructure and properties of the joints. The mechanical properties of the metal/ceramic (M/C) joints were assessed from bond strength tests carried out using a shear solicitation loading scheme. The fracture surfaces were studied both morphologically and structurally using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). The degradation behaviour of the M/C joints was assessed by means of electrochemical techniques. It was found that using a Ag-26.5Cu-3Ti brazing alloy and a brazing temperature of 850 deg. C, produces the best results in terms of bond strength, 234 {+-} 18 MPa. The mechanical properties obtained could be explained on the basis of the different compounds identified on the fracture surfaces by XRD. On the other hand, the use of the Ag-34.5Cu-1.5Ti brazing alloy and a brazing temperature of 850 deg. C produces the best results in terms of corrosion rates (lower corrosion current density), 0.76 {+-} 0.21 {mu}A cm{sup -2}. Nevertheless, the joints produced at 850 deg. C using a Ag-26.5Cu-3Ti brazing alloy present the best compromise between mechanical properties and degradation behaviour, 234 {+-} 18 MPa and 1.26 {+-} 0.58 {mu}A cm{sup -2}, respectively. The role of Ti diffusion is fundamental in terms of the final value achieved for the M/C bond strength. On the contrary, the Ag and Cu distribution along the

  19. Effect of component's geometry on the plasma nitriding behavior of AISI 4340 steel

    Highlights: → The thickness of the compound layer increases with increasing in temperature and groove width. → Surface layer at the remote regions from the edge is thinner than that of closer regions. → The hardness and the case depth of the nitrided layer increase with increasing the width of the groove. → Intensity of ε phase increases with increasing the width of the groove in both methods. → The ASPN specimens are covered by hexagonal particles and for the CPN by cauliflower shape nitrides. -- Abstract: The main aim of this work was to investigate the effect of the sample geometry on properties of the conventional plasma nitrided (CPN) and active screen plasma nitrided (ASPN) steel. Sample assemblies consisting of rectangular grooved steel blocks with different groove dimensions of 2, 4, 6, 8 and 10 (W) x 40 (H) x 20 (L) mm3 and AISI 4340 steel plates (substrates) with dimensions of 10 x 40 x 60 mm3, to serve as groove cover, were prepared. The sample assemblies were conventional and active screen plasma nitrided under the gas mixture of 75%N2 + 25%H2, at temperatures of 500 oC and 540 oC, pressure of 4 torr, for 5 h. Properties of the nitrided substrates were investigated by evaluating compound layer thickness, case depth, phase composition and hardness profile. Results of the experiments showed that the thickness of the compound layer, hardness and nitrided case depth increased with increasing the width of the groove for both methods. Also, in each sample, nitrogen atoms penetrated more deeply in the regions of the groove closer to the edge. Hallow cathode effect occurred at the sample with 2 mm width groove, in the CPN method, leading to the overheating of the sample. In ASPN, the hardness and the nitrided case depth are lower in comparison with CPN. The surface morphology of the CPN treated samples consists of cauliflower shape surface nitrides while the surface of the AS plasma nitrided samples are covered by the hexagonal particles with uniform

  20. Consistent Evaluation of ACOS-GOSAT, BESD-SCIAMACHY, CarbonTracker, and MACC Through Comparisons to TCCON

    Kulawik, Susan; Wunch, Debra; O’Dell, Christopher; Frankenberg, Christian; Reuter, Maximilian; Chevallier, Frederic; Oda, Tomohiro; Sherlock, Vanessa; Buchwitz, Michael; Osterman, Greg; Miller, Charles E.; Iraci, Laura T.; Wolf, Joyce

    2016-01-01

    Consistent validation of satellite CO2 estimates is a prerequisite for using multiple satellite CO2 measurements for joint flux inversion, and for establishing an accurate long-term atmospheric CO2 data record. Harmonizing satellite CO2 measurements is particularly important since the differences in instruments, observing geometries, sampling strategies, etc. imbue different measurement characteristics in the various satellite CO2 data products. We focus on validating model and satellite observation attributes that impact flux estimates and CO2 assimilation, including accurate error estimates, correlated and random errors, overall biases, biases by season and latitude, the impact of coincidence criteria, validation of seasonal cycle phase and amplitude, yearly growth, and daily variability. We evaluate dry-air mole fraction (X(sub CO2)) for Greenhouse gases Observing SATellite (GOSAT) (Atmospheric CO2 Observations from Space, ACOS b3.5) and SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) (Bremen Optimal Estimation DOAS, BESD v2.00.08) as well as the CarbonTracker (CT2013b) simulated CO2 mole fraction fields and the Monitoring Atmospheric Composition and Climate (MACC) CO2 inversion system (v13.1) and compare these to Total Carbon Column Observing Network (TCCON) observations (GGG2012/2014). We find standard deviations of 0.9, 0.9, 1.7, and 2.1 parts per million vs. TCCON for CT2013b, MACC, GOSAT, and SCIAMACHY, respectively, with the single observation errors 1.9 and 0.9 times the predicted errors for GOSAT and SCIAMACHY, respectively. We quantify how satellite error drops with data averaging by interpreting according to (error(sup 2) equals a(sup 2) plus b(sup 2) divided by n (with n being the number of observations averaged, a the systematic (correlated) errors, and b the random (uncorrelated) errors). a and b are estimated by satellites, coincidence criteria, and hemisphere. Biases at individual stations have year