Sample records for chromizing

  1. Peningkatan Sifat-Sifat Fatik Baja NS-1045 Chromized dengan Proses Perlakuan Panas

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    Amru Siregar


    Full Text Available Metal alloys for usage the high temperature, besides needed the good mechanical properties, also needed the corrosion resistance properties. Chromized components exhibit superior resistance to a variety of aggressive corrosive mechanism, including high temperature oxidation, and chloride-related attack. Chromized coatings are diffusion-type coating can be applied by electrodeposition. So that happened degradation fatigue strength of chromized steel. The mechanical properties of chromized steel can be improved by heat-treatment process. In this research conducted hardening and tempering process to NS-1045 chromized steel. Influence of heat-treatment to the mechanical properties, it is has been tested by using machine rotary bending test. While examination of microstructure can do it by using microscope optic and scanning electrone microscopy (SEM. Analysis influence heat-treatment of NS-1045 chromized steel to fatigue strength, it is increase about (20÷25%.

  2. Segregation of Molten Salt on Chromizing in Thermal Diffusion Process

    Institute of Scientific and Technical Information of China (English)

    WANG Hongfu; WANG Junyuan; WANG Huachang


    The segregation of thermal diffusion salt bath chromizing process was analyzed.The experimental chromizing ingredients were prepared by the four groups A,B,C,and D.In order to study the segregation status of this case,the cooling molten salt in the crucible was removed by drilling from the heart core of molten salt.The core of molten salt was analyzed by X-ray fluorescence spectroscopy and XRD.Through the analysis,we can conclude that the Cr element deposited in the bottom was 4.51 times than the top.Chloride added to the molten salt will reduce segregation.Meantime we proposed some measures to overcome the segregation problem.

  3. Oxidation of Al2O3-dispersion chromizing coating by pack-cementation at 800℃

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yue-bo; CHEN Hong-yu; ZHANG Hai-jun; WANG Yong-dong


    Preparation and oxidation of an Al2O3-dispersed chromizing coating were investigated by chromizing an aselectrodeposited Ni-Al2O3 nanocomposite film using a conventional pack-cementation method at a greatly decreased temperature (800℃).For comparison,chromizing was also performed with the same condition on an as-deposited Ni film without Al2O3 nanoparticles.Oxidation at 900℃ indicates that,compared with the Al2O3-free chromizing coating,the Al2O3-dispersed chromizing coating exhibits a increased oxidation resistance,due to the formation of purer and denser chromia scale.The effect of Al2O3 on the coating formation and the coating oxidation behavior was discussed in details.

  4. Effect of Y2O3 on microstructure and oxidation of chromizing coating

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yue-bo; ZHANG Hai-jun; WANG Yong-dong


    A Y2O3-modified chromizing coating was produced by chromizing an as-electrodeposited Ni-Y2O3 composite film using pack cementation method at 1 100 ℃ for 3 h. For comparison, chromizing was also performed under the same condition on an as-deposited Ni film without Y2O3 particles. Oxidation at 900 ℃ for 120 h indicates that although on both two chromizing coatings chromia scales grow during oxidation, the Y2O3-modified chromizing coating exhibits an increased oxidation resistance due to the formation of thinner, denser and freer-grain scale. The effect of Y2O3 on the coating formation and the coating oxidation behavior was discussed in detail.

  5. A Novel Duplex Low-temperature Chromizing Process at 500℃

    Institute of Scientific and Technical Information of China (English)


    An optimized low-temperature chromizing process at 500℃ was realized on a plain medium-carbon steel with 0.45 wt pct carbon via a duplex chromizing process which consists of a precursor plasma nitriding, and a followed salt bath thermoreactive deposition and diffusion (TRD) chromizing process. CrN layer with a thin diffusion layer underneath was formed. The duplex chromizing process was studied by optical microscopy(OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction(XRD), and transmission electron microscopy (TEM). It was found that the chromizing speed at 500℃ was successfully enhanced by adding more Cr-Fe powders into the salt bath, and the CrN layer formed at the cost of the prior nitride compound layer. A CrN layer with average 8.1μm in thickness and 1382 HV0.01 in microhardness was formed on the substrate by duplex chromizing at 500℃ for 24 h. Further more, the CrN layer consisted of nanocrystalline CrN grains.

  6. Thermodynamic analysis of carbon migration in W1-1.0C steel in plasma surface chromizing

    Institute of Scientific and Technical Information of China (English)


    W1-1.0C steel was chromized at 1173 K with double glow plasma surface alloying process, and the distribution of Fe, Cr,and C contents in the chromized layer was measured using glow discharge spectrum analysis (GDA).The behavior and mechanism of carbon migration during the formation of chromized layer were studied through thermodynamic analysis and calculation.The gradient of carbon chemical potential was regarded as the driving force of carbon migration.An equation was derived to describe the carbon content varying with the chromium content within the carbon-rich region.The calculated results from the equation approximated closely to the experimental ones.

  7. Comparison of surface fractal dimensions of chromizing coating and P110 steel for corrosion resistance estimation

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Naiming, E-mail: [Research Institute of Surface Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Guo, Junwen [Research Institute of Surface Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Xie, Faqin [School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072 (China); Zou, Jiaojuan; Tian, Wei [Research Institute of Surface Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Yao, Xiaofei [School of Materials and Chemical Engineering, Xi’an Technological University, Xi’an 710032 (China); Zhang, Hongyan; Tang, Bin [Research Institute of Surface Engineering, Taiyuan University of Technology, Taiyuan 030024 (China)


    Highlights: • Continuous chromizing coating was synthesized on P110 steel by pack cementation. • The chromizing coating showed better corrosion resistance. • Comparison of surface fractal dimensions can estimate corrosion resistance. - Abstract: In the field of corrosion research, mass gain/loss, electrochemical tests and comparing the surface elemental distributions, phase constitutions as well as surface morphologies before and after corrosion are extensively applied to investigate the corrosion behavior or estimate the corrosion resistance of materials that operated in various environments. Most of the above methods are problem oriented, complex and longer-period time-consuming. However from an object oriented point of view, the corroded surfaces of materials often have self-similar characterization: fractal property which can be employed to efficiently achieve damaged surface analysis. The present work describes a strategy of comparison of the surface fractal dimensions for corrosion resistance estimation: chromizing coating was synthesized on P110 steel surface to improve its performance via pack cementation. Scanning electron microscope (SEM) was used to investigate the surface morphologies of the original and corroded samples. Surface fractal dimensions of the detected samples were calculated by binary images related to SEM images of surface morphologies with box counting algorithm method. The results showed that both surface morphologies and surface fractal dimensions of P110 steel varied greatly before and after corrosion test, but the chromizing coating changed slightly. The chromizing coating indicated better corrosion resistance than P110 steel. Comparison of surface fractal dimensions of original and corroded samples can rapidly and exactly realize the estimation of corrosion resistance.

  8. Influence of adding various rare earths on microstructures and corrosion resistance of chromizing coatings prepared via pack cementation on P110 steel

    Institute of Scientific and Technical Information of China (English)

    林乃明; 谢发勤; 钟涛; 吴向清; 田伟


    In order to improve the corrosion resistance and increase the service lifetime of P110 steel during operation,four chromizing coatings were formed onto its surface with/without addition of rare earths via pack cementation process.The surface morphologies and microstructures of the chromizing coatings were observed using scanning electron microscopy(SEM),and the phase constitutions were investigated by X-ray diffraction(XRD).Electrochemical corrosion behavior of the chromizing coatings in simulated oilfield ...

  9. Improved corrosion resistance and interfacial contact resistance of 316L stainless-steel for proton exchange membrane fuel cell bipolar plates by chromizing surface treatment (United States)

    Lee, S. B.; Cho, K. H.; Lee, W. G.; Jang, H.

    The electrochemical performance and electrical contact resistance of chromized 316 stainless-steel (SS) are investigated under simulated operating condition in a proton-exchange membrane fuel cell (PEMFC). The corrosion resistance of the chromized stainless steel is assessed by potentiodynamic and potentiostatic tests and the interfacial contact resistance (ICR) is examined by measuring the electrical contact resistance as a function of the compaction force. The results show that the chromizing surface treatment improves the corrosion resistance of the stainless steel due to the high-chromium concentration in the diffuse coating layer. On the other hand, the excess Chromium content on the surface increases the contact resistance of the steel plate to a level that is excessively high for commercial applications. This study examines the root cause of the high-contact resistance after chromizing and reports the optimum process to improve the corrosion resistance without sacrificing the ICR by obtaining a chrome carbide on the outer layer.

  10. Tribological properties of CrN coatings deposited by nitro-chromizing treatment on AISI D2 steel

    Energy Technology Data Exchange (ETDEWEB)

    Durmaz, M., E-mail:; 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)


    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.

  11. Chromized Layers Produced on Steel Surface by Means of CVD

    Institute of Scientific and Technical Information of China (English)



    Chemical vapour deposition of chromium on the surface of carbon steel has been investigated using a novel CVD method that combines the low cost of pack cementation method with advantages of vacuum technique. The processes have been performed in chromium chlorides atmosphere at a low pressure range from 1 to 800 hPa, the treatment temperature 800 to 950℃. Studies of the layers thickness, the phase composition, Cr, C and Fe depth profiles in diffusion zone have been conducted. The effect of the vacuum level during the process and the process parameters such as time and temperature on layer diffusion growth on the carbon steel surface has been investigated.

  12. Low Temperature Salt-bath Chromizing of Steel 45%45钢的低温盐浴渗铬

    Institute of Scientific and Technical Information of China (English)

    叶金玲; 叶峰; 邹敢锋



  13. An investigation on the effect of chromizing parameters on hot corrosion behaviour of In-738 Lc at 850 'deg'

    International Nuclear Information System (INIS)

    One of the most effective method used in protecting gas turbine blade against hot corrosion and oxidation is the employment of enriched chromium coatings. The effect of processing parameters such as time and chemical compositions of coating on its structure and hot corrosion resistance were evaluated in this work. Pack cementation method was used at 1100 degfor various time. Structure of coating was examined using the light and electron microscopy to evaluate hot corrosion resistance of the coated specimens, that were subjected to hot corrosion test at 850 'deg' for 528 hr s along with an uncoated sample. The corroded surfaces of the samples were studied using light and electron microscopes as well as XRD analysis. The results show that by increasing both the amount of chromium in the pack and time of operation, hot corrosion resistance of coating increases. However, the mechanical properties of the coated samples were adversely affected by increasing the surface concentration of chromium and/or thickness of coating more than a certain amount. Therefore, it is essential to optimize the time and chromium concentration in order to obtain the best mechanical and hot corrosion properties

  14. Evaluation of equilibrium composition of saturating medium on steel niobium-chromizing in chlorine-containing environment

    International Nuclear Information System (INIS)

    For the process of diffusion coating of steels with niobium and chromium an equilibrium composition of reactive media under reduced pressure was studied. Thermodynamic analysis was made within the temperature range of 500-1500 K for eight systems including Nb, Cr, Cl, C as initial reagents and O2, N2 and Fe as components of air and steels treated. The results obtained may help to determine optimum composition of saturating medium and show the possibility of niobium carbide formation in a wide temperature range

  15. Influence of Pre-Nitrocarburizing on Chromizing and Vanadizing%预先氮碳共渗对渗铬和渗钒的影响

    Institute of Scientific and Technical Information of China (English)

    倪宏昕; 单丽云; 王超; 倪振尧



  16. Simultaneous aluminizing and chromizing of steels to form (Fe,Cr){sub 3}Al coatings and Ge-doped silicide coatings of Cr-Zr base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, M.; He, Y.R.; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering


    A halide-activated cementation pack involving elemental Al and Cr powders has been used to achieve surface compositions of approximately Fe{sub 3}Al plus several percent Cr for low alloy steels (T11, T2 and T22) and medium carbon steel (1045 steel). A two-step treatment at 925 C and 1150 C yields the codeposition and diffusion of aluminum and chromium to form dense and uniform ferrite coatings of about 400 {micro}m thickness, while preventing the formation of a blocking chromium carbide at the substrate surfaces. Upon cyclic oxidation in air at 700 C, the coated steel exhibits a negligible 0.085 mg/cm{sup 2} weight gain for 1900 one-hour cycles. Virtually no attack was observed on coated steels tested at ABB in simulated boiler atmospheres at 500 C for 500 hours. But coatings with a surface composition of only 8 wt% Al and 6 wt% Cr suffered some sulfidation attack in simulated boiler atmospheres at temperatures higher than 500 C for 1000 hours. Two developmental Cr-Zr based Laves phase alloys (CN129-2 and CN117(Z)) were silicide/germanide coated. The cross-sections of the Ge-doped silicide coatings closely mimicked the microstructure of the substrate alloys. Cyclic oxidation in air at 1100 C showed that the Ge-doped silicide coating greatly improved the oxidation resistance of the Cr-Zr based alloys.

  17. Surface modification and performance of inexpensive Fe-based bipolar plates for proton exchange membrane fuel cells (United States)

    Bai, Ching-Yuan; Wen, Tse-Min; Huang, Mao-Suan; Hou, Kung-Hsu; Ger, Ming-Der; Lee, Shuo-Jen

    A reforming pack chromization with rolling pretreatment process is utilized to develop inexpensive and high-performance Fe-based metal bipolar plates (SS 420, SS 430, and SS 316 stainless steels) for PEMFC systems. Rolling process is previously performed to reduce the chromizing temperature and generate a coating possessing excellent conductivity and corrosion resistance on the steels during chromization. The power efficiencies of rolled-chromized and simple chromized bipolar plates are compared with graphite bipolar plates employed in PEMFCs. The results show that the rolled-chromized bipolar plates have a corrosion current (I corr) of 7.87 × 10 -8 A cm -2 and an interfacial contact resistance of 9.7 mΩ cm 2. Moreover, the power density of the single cell assembled with rolled-chromized bipolar plates is 0.46 W cm -2, which is very close to that of graphite (0.50 W cm -2), in the tested conditions of this study.

  18. An introduction to surface alloying of metals

    CERN Document Server

    Hosmani, Santosh S; Goyal, Rajendra Kumar


    An Introduction to Surface Alloying of Metals aims to serve as a primer to the basic aspects of surface alloying of metals. The book serves to elucidate fundamentals of surface modification and their engineering applications. The book starts with basics of surface alloying and goes on to cover key surface alloying methods, such as carburizing, nitriding, chromizing, duplex treatment, and the characterization of surface layers. The book will prove useful to students at both the undergraduate and graduate levels, as also to researchers and practitioners looking for a quick introduction to surface alloying.

  19. The influence of Cr and Al pack cementation on low carbon steel to improve oxidation resistance (United States)

    Prasetya, Didik; Sugiarti, Eni; Destyorini, Fredina; Thosin, Kemas Ahmad Zaini


    Pack chromizing and aluminizing has been widely used for many years to improve hot temperature oxidation and corrosion resistance of metals. The coating process involves packing the steel in a powder mixture which contain aluminum and chromium source, and inert filler (usually alumina), and halide activator NH4Cl. Al and Cr were deposited onto carbon steel by pack cementation process using elemental Al and Cr powder as Al and Cr source, whereas NiCo alloys codeposited by electrodeposition. The position of Al and Cr could be under or over Ni-Co alloys deposited. Pack cementation was heated on dry inert gas at temperature 800 °C about 5 hours and 20 minute for Cr and Al respectively. Al and Cr was successfully deposited. Laying down effect of Al and Cr onto carbon steel whether up and down toward NiCo alloys coating have affected to oxidation resistance. The pack aluminizing as top layer given best resitance to restrain excessive oxide scale, in contrast pack chromizing reveal bad oxidation resistance, moreover occured spallation on layer.

  20. Development of anti-corrosion coating on low activation materials against fluoridation and oxidation in Flibe blanket environment

    Energy Technology Data Exchange (ETDEWEB)

    Nagasaka, Takuya, E-mail: [National Institute for Fusion Science, Oroshi 322-6, Toki, Gifu 509-5292 (Japan); Kondo, Masatoshi; Muroga, Takeo; Sagara, Akio; Motojima, Osamu [National Institute for Fusion Science, Oroshi 322-6, Toki, Gifu 509-5292 (Japan); Tsutsumi, Tatsuya; Oishi, Tatsuya [Shinto Industrial Co., Ltd., Kururi 376-10, Tokitsu, Nagasaki 851-2107 (Japan)


    W coating by vacuum plasma spray process and Cr coating by chromizing process were performed on fusion low activation materials, JLF-1 ferritic steel and NIFS-HEAT-2 vanadium alloy. The present study discusses feasibility of the coatings as anti-corrosion coating against fluoridation in Flibe for fusion low activation materials. Coatings were characterized by microstructural analysis and examination on chemical stability by corrosion tests. The corrosion tests were conducted with H{sub 2}O-47% HF solution at RT and He-1% HF-0.06 H{sub 2}O gas mixture at 823 K to simulate fluoridation and oxidation in Flibe. The coatings presented suppression of fluoride formation compared with JLF-1 or NIFS-HEAT-2, however weight loss due to WF{sub 6} formation was induced, and much Cr{sub 2}O{sub 3} was formed.

  1. Plasma surface alloying of titanium alloy for enhancing burn-resistant property

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ping-ze; XU Zhong; ZHANG Gao-hui; HE Zhi-yong; YAO Zheng-jun


    Conventional titanium alloy may be ignited and burnt under high temperature, high pressure and high gas flow velocity condition. In order to avoid this problem, burn-resistant alloying layers were made on the surface of Ti-6Al-4V and Ti-6.5Al-0.3Mo-1.5Zr-0.25Si titanium alloys by using double glow plasma surface alloying technology (DG Technology). Two typical burn-resistant layers Ti-Cr and Ti-Mo were made by DG plasma chromizing and DG plasma molybdenizing, respectively. Burn-resistant properties were tested by layer ignition method using 2 kW laser machine. Ignition experiments result reveals that the ignition temperature of alloyed layer with Mo and Cr concentration above 10% is about 200℃ higher than ignition temperature of Ti-6Al-4V substrate.

  2. Formation of Chromium Coating and Comparative Examination on Corrosion Resistance with 13Cr Steel in CO2-SATURATED Simulated Oilfield Brine (United States)

    Zou, Jiaojuan; Xie, Faqin; Lin, Naiming; Yao, Xiaofei; Tian, Wei; Tang, Bin


    In order to enhance the surface properties of P110 oil casing tube steel and increase its usage during operation, chromium coating was fabricated by pack cementation. Scanning electron microscope, energy dispersive spectrometry and X-ray diffraction were used to investigate the surface morphology, cross-sectional microstructure, element distribution and phase constitutions of the coating. Comparative examinations on corrosion resistance between chromium coating and 13Cr stainless steel in CO2-saturated simulated oilfield brine were carried out via electrochemical measurements. The results showed that the obtained coating was uniform and compact, mainly consisted of CrxCy and doped with minor Cr2N. Chromizing treatment made it possible to create on the working surface of P110 steel with enhanced corrosion resistance, and the chromium coating indicated lower pitting corrosion sensitivity than that of 13Cr stainless steel.

  3. Study on an innovative fast reactor utilizing hydride neutron absorber development of coating technique on cladding inner surface

    International Nuclear Information System (INIS)

    The study to extend the control rod life of the Fast Reactor (FR) and to compress its excess reactivity are being performed by adopting the hafnium hydride (HfHx) for control rod material and by using the gadolinium hydride (GdHx) burnable poison (BP) for the reactivity recession, respectively. In the program named 'Study on an innovative Fast Reactor utilizing Hydride Neutron Absorber', the coating technique on inner surface of cladding has been developed to prevent hydrogen transfer through cladding at occasions of the temperature rise events. The Cr2O3 coating (chromizing) and the Al2O3 coating (calorizing) were selected for the coating techniques from the viewpoint of stability under in-core conditions. Following tests were performed for austenitic steel SUS316 which is widely used in FRs and for ferritic steel SUS430. The SUS430 was selected to simulate the ODS (Oxide Dispersion Strengthened ferritic steel) which is the attractive candidate material for the high burn-up FR. Examination of coating processing conditions by using short length claddings (100-200 mm). Approval of coating conditions to mock-up length cladding (1000 mm). Measurement of hydrogen transfer coefficient. Then appropriate conditions for coating were clarified and the formation of homogeneous films of both chromizing and calorizing was achieved on the inner surfaces of long length claddings (1000 mm). The hydrogen transfer experiments showed that the hydrogen transfer coefficient of coated SUS316 and SUS430 can be reduced to below 1/10 of SUS316 raw material. (author)

  4. Influence of process parameters on thickness and wear resistance of rare earth modified chromium coatings on P110 steel synthesized by pack cementation

    Institute of Scientific and Technical Information of China (English)

    LIN Naiming; XIE Faqin; WU Xiangqing; TIAN Wei


    The pack cementation was employed to produce rare earth modified chromium coatings on P110 steel aiming at improving its performance and increasing the usage lifetime during operation. The orthogonal array design (OAD) was applied to set experiments. Contents of NH4Cl, types of RE, contents of RE, test temperature and soaking time were the main factors, and each factor was endowed with four levels.While the range analysis and analysis of variance were used to investigate the results of OAD tests on thickness and wear resistance. The results indicated that for a promising coating with higher thickness value and excellent anti-wear property, the test temperature was the most significant process factor. The potential promising conditions for chromizing treatment were: adding 1% NH4Cl and 1% LaCl3, maintaining the test temperature at 1000 ℃ for 8 h. The results of verification showed that the coating formed under the optimal process parameter had a valid thickness of 28 μm and a reduction of 0.32 mg in wear resistance test.

  5. Development of fracture mechanics data for two hydrazine APU turbine wheel materials (United States)

    Curbishley, G.


    The effects of high temperature, high pressure ammonia were measured on the fracture mechanics and fatigue properties of Astroloy and Rene' 41 turbine wheel materials. Also, the influence of protective coatings on these properties was investigated. Specimens of forged bar stock were subjected to LCF and HCF tests at 950 K (1250 F) and 3.4 MN/sq m (500 psig) pressure, in ammonia containing about 1.5 percent H2O. Aluminized samples (Chromizing Company's Al-870) and gold plated test bars were compared with uncoated specimens. Comparison tests were also run in air at 950 K (1250 F), but at ambient pressures. K sub IE and K sub TH were determined on surface flawed specimens in both the air and ammonia in both uncoated and gold plated conditions. Gold plated specimens exhibited better properties than uncoated samples, and aluminized test bars generally had lower properties. The fatigue properties of specimens tested in ammonia were higher than those tested in air, yet the K sub TH values of ammonia tested samples were lower than those tested in air. However, insufficient specimens were tested to develop significant design data.

  6. Final Report, Materials for Industrial Heat Recovery Systems, Tasks 3 and 4 Materials for Heat Recovery in Recovery Boilers

    Energy Technology Data Exchange (ETDEWEB)

    Keiser, James R.; Kish, Joseph R.; Singh, Preet M.; Sarma, Gorti B.; Yuan, Jerry; Gorog, J. Peter; Frederick, Laurie A.; Jette, Francois R.; Meisner, Roberta A.; Singbeil, Douglas L.


    tubes. Also, these fluctuating air flow patterns can result in deposition of black liquor on the wall tubes, and during periods when deposition is high, there is a noticeable increase in the concentrations of sulfur-bearing gases like hydrogen sulfide and methyl mercaptan. Laboratory studies have shown that chromized and aluminized surface treatments on carbon steel improve the resistance to sulfidation attack. Studies of superheater corrosion and cracking have included laboratory analyses of cracked tubes, laboratory corrosion studies designed to simulate the superheater environment and field tests to study the movement of superheater tubes and to expose a corrosion probe to assess the corrosion behavior of alternate superheater alloys, particularly alloys that would be used for superheaters operating at higher temperatures and higher pressures than most current boilers. In the laboratory corrosion studies, samples of six alternate materials were immersed in an aggressive, low melting point salt mixture and exposed for times up to 336 h, at temperatures of 510, 530 or 560°C in an inert or reactive cover gas. Using weight change and results of metallographic examination, the samples were graded on their resistance to the various environments. For the superheater corrosion probe studies, samples of the same six materials were exposed on an air-cooled corrosion probe exposed in the superheater section of a recovery boiler for 1000 h. Post exposure examination showed cracking and/or subsurface attack in the samples exposed at the higher temperatures with the attack being more severe for samples 13 exposed above the first melting temperature of the deposits that collected on the superheater tubes. From these superheater studies, a ranking was developed for the six materials tested. The task addressing cracking and corrosion of primary air port tubes that was part of this project produced results that have been extensively implemented in recovery boilers in North America