Impact behavior of 9-Cr and 12-Cr ferritic steels after low-temperature irradiation

International Nuclear Information System (INIS)

Klueh, R.L.; Vitek, J.M.; Corwin, W.R.; Alexander, D.J.

1987-01-01

Miniature Charpy impact specimens of 9Cr-1MoVNb and 12Cr-1MoVW steels and these steels with 1 and 2% Ni were irradiated in the High-Flux Isotope Reactor (HFIR) at 50 0 C to displacement damage levels of up to 9 dpa. Nickel was added to study the effect of transmutation helium. Irradiation caused an increase in the ductile-brittle transition temperature (DBTT). The 9Cr-1MoVNb steels, with and without nickel, showed a larger shift than the 12Cr-1MoVW steels, with and without nickel. The results indicated that helium also increased the DBTT. The same steels were previously irradiated at higher temperatures. From the present and past tests, the effect of irradiation temperature on the DBTT behavior can be evaluated. For the 9Cr-1MoVNb steel, there is a continuous decrease in the magnitude of the DBTT increase up to an irradiation temperature of about 400 0 C, after which the shift drops rapidly to zero at about 450 0 C. The DBTT of the 12Cr-1MoVW steel shows a maximum increase at an irradiation temperature of about 400 0 C and less of an increase at either higher or lower irradiation temperatures

The effects of adding molybdenum and niobium on the creep strength of 18Cr-10Ni-20Co austenitic steel

International Nuclear Information System (INIS)

Tomono, Yutaka

1987-01-01

The decrease in the creep strength of structural materials during service at elevated temperatures is a very important problem that affects the security of plants and machinery. The improvement in the creep strength of 18Cr-10Ni-20Co austenitic steel achieved through the addition of molybdenum and niobium was studied in tests carried out at 973K and 1,073K. The creep strengthening mechanism was examined using transmission electron micrographs, X-ray diffraction, etc. The results obtained are summarized as follows: (1) The creep strength of low C-18Cr-10Ni-20Co austenitic steel with molybdenum was greatly improved by the addition of niobium up to 1% by weight. In the case of long-term creep, no trend toward decreasing creep strength was observed. (2) The creep strength of austenitic steel possessing a matrix strengthened with molybdenum can be improved through the addition of niobium combined with precipitation hardening with fine carbides precipitated in the grains. (author)

Creep Strength of Dissimilar Welded Joints Using High B-9Cr Steel for Advanced USC Boiler

Science.gov (United States)

Tabuchi, Masaaki; Hongo, Hiromichi; Abe, Fujio

2014-10-01

The commercialization of a 973 K (700 °C) class pulverized coal power system, advanced ultra-supercritical (A-USC) pressure power generation, is the target of an ongoing research project initiated in Japan in 2008. In the A-USC boiler, Ni or Ni-Fe base alloys are used for high-temperature parts at 923 K to 973 K (650 °C to 700 °C), and advanced high-Cr ferritic steels are planned to be used at temperatures lower than 923 K (650 °C). In the dissimilar welds between Ni base alloys and high-Cr ferritic steels, Type IV failure in the heat-affected zone (HAZ) is a concern. Thus, the high B-9Cr steel developed at the National Institute for Materials Science, which has improved creep strength in weldments, is a candidate material for the Japanese A-USC boiler. In the present study, creep tests were conducted on the dissimilar welded joints between Ni base alloys and high B-9Cr steels. Microstructures and creep damage in the dissimilar welded joints were investigated. In the HAZ of the high B-9Cr steels, fine-grained microstructures were not formed and the grain size of the base metal was retained. Consequently, the creep rupture life of the dissimilar welded joints using high B-9Cr steel was 5 to 10 times longer than that of the conventional 9Cr steel welded joints at 923 K (650 °C).

Determination of susceptibility to intergranular corrosion of stainless steels type X5CrNi18-10 in field

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Bore V. Jegdic

2016-12-01

Full Text Available In this paper, the DL EPR method (electrochemical potentiokinetic reactivation with double loop was modified and used to study the susceptibility to intergranular corrosion and stress corrosion cracking of a stainless steel type X5CrNi18-10. The tests were performed in a special electrochemical cell, with the electrolyte in the gel form. Modified DL EPR method is characterized by simple and high accuracy measurements as well as repeatability of the test results. The indicator of susceptibility to intergranular corrosion (Qr/QpGBA obtained by modified DL EPR method is in a very good agreement with the same indicator obtained by standard DL EPR method. The modified DL EPR method is quantitative and highly selective method. Small differences in the susceptibility of the stainless steel type CrNi18-10 to intergranular corrosion and stress corrosion cracking can be determined. Test results can be obtained in a short time. The cost of tests performed by modified DL EPR method is much lower than the cost of tests by conventional chemical methods. Modified DL EPR method can be applied in the field on the stainless steels constructions.

Long-term Stability of 9- to 12 % Cr Steels

DEFF Research Database (Denmark)

Hald, John

2004-01-01

In the recent 25 years creep rupture strength of 9- to 12 %Cr steels for steam pipes and turbines has been doubled by development of new alloys. This development has formed a basis for improved efficiency of fossil fired steam power plants by introduction of advanced steam temperatures...... and pressures. Newly developed steam pipe steels are based on modifications of well-established steels like the X 20CrMoV12 1. Balanced addition of V, Nb and N to a 9Cr 1 Mo steel led to the Modified 9 Cr steel P 91. Addition of 1% W to a 9Cr 1 MoVNbN base composition led to steel E 911 and partial replacement...... of Mo with 1.8 % W combined with a slight amount of Boron led to steel P 92. The creep rupture strength of these new alloys are now secured with long-term tests up to 100,000 hours, which demonstrate improvements of 50% (P 91), 75 % (E 911) and 100 % (P 92) in strength compared to X 20CrMoV12 1....

Structure change in 25 Cr - 20 Ni steels as a function of their Cr, Ni, Si and W content

International Nuclear Information System (INIS)

Gribaudo, L.M.; Durand, F.; Durand-Charre, M.

1983-01-01

The influence of varying the Cr, Ni, Si and W concentrations on the type and composition of the carbides of solidification and on the phase shift temperature is studied with 18 alloys of composition close to stainless steel-25-20 (AISI 310) composition. Experimental techniques used are differential thermal analysis, microprobe and scanning electron microscope. Crystallization is interpreted with the equilibrium diagram Ni-Cr-C. The formation of the interdendritic σ phase for a chromium rich alloys is interpreted with the phase equilibrium diagram of Fe-Ni-Cr-C. Mechanical properties and corrosion resistance are dependent on the morphology of the carbides M 7 C 3 and M 23 C 6 [fr

Influence of damage rate on physical and mechanical properties and swelling of 18Cr-9Ni austenitic steel in the range of 3.10-9 to 4.10-8 dpa/sec

International Nuclear Information System (INIS)

Shcherbakov, E.N.; Kozlov, A.V.; Yagovitin, R.I.; Evseev, M.V.; Kinev, E.A.; Isobe, Y.; Sagisaka, M.; Okita, T.; Sekimura, N.; Garner, F.

2007-01-01

Full text of publication follows: Whereas most data on radiation-induced changes in mechanical properties or dimensional stability needed for fusion - relevant dpa levels and dpa rates are generated at relatively high neutron flux in fast reactors, many fusion and fission components will operate at much lower dpa rates. Much less data are available from long-lived structural components operating at very low flux levels. In addition most published data were generated from relatively thin specimens (∼1-2 mm or less), while some actual fusion structural components can be on the order of 1-2 cm thick. In this study we have examined a 9 cm diameter pipe constructed from Fe-18Cr-9Ni steel analogous to AISI 304 that stayed outside the core of BN-600 for 22 years. The walls of the pipe were 2 cm thick and experienced temperatures in the range 370-375 deg. C. The walls were sectioned into 5 slices at a number of positions to yield doses in the range 1.5 to 22 dpa at 3 x 10 -9 to 4 x 10 -8 dpa/s. Changes in elastic moduli were studied using an ultrasonic technique and changes in electrical resistivity and mechanical properties of the 18Cr9Ni austenitic steel was examined. Swelling was measured both by immersion density and electron microscopy, reaching a maximum of ∼3 %. Swelling appears to be accelerated somewhat at these lower dpa rates as observed in other recent studies. Tensile properties were also measured. Radiation-induced changes of electrical resistivity, Young's and shear moduli were observed but did not agree fully with predictions based on voids alone. Strong contributions from second phase precipitates were found to be contributing to changes in both physical and mechanical properties. (authors)

Shot Peening Effects on Subsurface Layer Properties and Fatigue Performance of Case-Hardened 18CrNiMo7-6 Steel

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H. S. Ho

2018-01-01

Full Text Available The present study is conducted with a dual-aim: firstly, to examine the effect of several single shot peening conditions on the subsurface layer properties and fatigue performance of the case-hardened 18CrNiMo7-6 steel, and secondly, to propose an optimized peening condition for improved fatigue performance. By carrying out the subsurface integrity analysis and fatigue testing, the underlying relationships among the peening process, subsurface layer property and fatigue performance are investigated, the way peening conditions affect the fatigue life and its associated scatter for the case-hardened 18CrNiMo7-6 steel is quantitatively assessed. The in-depth study shows that dual peening can be an optimized solution, for it is able to produce a subsurface layer with enhanced properties and eventually gain a significant improvement in fatigue performance.

Measurement of high temperature elastic moduli of an 18Cr-9Ni-2.95 Cu-0.58 Nb-0.1C (Wt %) austenitic stainless steel

Science.gov (United States)

Tripathy, Haraprasanna; Hajra, Raj Narayan; Sudha, C.; Raju, S.; Saibaba, Saroja

2018-04-01

The Young's modulus (E) and Shear modulus (G) of an indigenously developed 18Cr-9Ni-0.1C-2.95 Cu-0.58Nb (wt %) austenitic stainless steel has been evaluated in the temperature range 298 K to 1273 K (25 °C to 1000 °C), using Impulse excitation technique (IET). The Bulk modulus (K) and the poison's ratio have been estimated from the measured values of E and G. It is observed that the elastic constants (E, G and K) are found to decrease in a nonlinear fashion with increase in temperature. The Cu precipitation is found to influence the elastic moduli of the steel in the cooling cycle. The observed elastic moduli are fitted to 3rd order polynomial equations in order to describe the temperature dependence of E, G, K moduli in the temperature range 298-1273 K (25 °C to 1000 °C). The room temperature values of E,G and K moduli is found to be 207, 82 and 145 GPa respectively for the present steel.

Room and elevated temperature Mechanical Behavior of 9-12% Cr Steels

Energy Technology Data Exchange (ETDEWEB)

Dogan, Omer N.; Hawk, Jeffrey A.; Schrems, Karol K.

2005-02-01

The mechanical properties of medium Cr steels used in fossil fired power plants are very good because of their excellent high temperature microstructural stability. However, as the desire to increase the operating temperature (>650C) of the plant goes up, the need for steels that maintain their strength at these temperatures also increases. The mechanical properties of three medium Cr steels (0.08C-(9-12)Cr-1.2Ni-0.7Mo-3.0Cu-3.0Co-0.5Ti) were investigated through hardness, hot hardness and tensile measurements. The strength of the 9-12%Cr steels at room temperature after long-term isothermal aging (750C; 1000 hours) compares favorably with that of other power plant steels (e.g., P91). In addition, the elevated temperature strength and hot hardness also behave similarly. The mechanical behavior will be discussed in terms of the strength, elongation and tensile fracture characteristics.

Microstructure and elevated temperature stability of 9-12% Cr steels

Energy Technology Data Exchange (ETDEWEB)

Dogan, Omer N.; Hawk, Jeffrey A.

2005-02-01

Medium Cr steels have been used in fossil fired power plants for many years because of their excellent high temperature stability and mechanical properties. As the desire to increase the efficiency of power plants continues, the operating temperature (>650C) continues to go up. Currently available low and medium Cr containing steels will not withstand the new operating temperature and must be reassessed in terms of their solid-solution and precipitation strengthening schemes. Three medium Cr steels were developed to investigate high temperature alloy strengthening strategies: 0.08C-(9-12)Cr-1.2Ni-0.7Mo-3.0Cu-3.0Co-0.5Ti. The microstructure of the alloy will be described in the as-cast and thermo-mechanically worked states. In addition, the effect on microstructure from long-term high temperature exposure will also be discussed. Finally, the overall stability of these steels will be compared against currently available power plant steels.

Creep and creep fatigue crack behavior of 1Cr- and 9Cr-steels

International Nuclear Information System (INIS)

Maile, K.; Klenk, A.; Schellenberg, G.; Granacher, J.; Tramer, M.

2000-01-01

A large database for creep crack initiation and propagation under constant load conditions is available on conventional power plant steels of types 1%Cr and 12%Cr. Modern plants are often used in the medium and peak load regime, thus the dominant loading situation in high temperature components is creep fatigue. For life assessment data about crack initiation and growth under creep fatigue loading are required. These characteristics can not be substituted by pure fatigue or creep crack data. Therefore, a comprehensive test programme was started to investigate the creep fatigue crack behaviour of a 1%CrMoNiV turbine rotor steel (30CrMoNiV 4 11) at 550 C and a new 9%CrMoVNb pipe steel (type P 9 1) at 600 C. DENT-specimen with 15 and 60 mm thickness as well as side grooved CT-specimen with 25 and 50 mm thickness have been tested to determine possible influences of geometry and thus to check the transferability of the data to components. The creep fatigue crack growth results of tests with dwell times between t H = 0,32h and 10 h lie in the scatterbands given by creep crack growth results. Nevertheless a higher crack growth rate under creep fatigue conditions can be stated. An increase in crack growth rate due to creep fatigue is clearly visible. Loading situations with frequencies higher than 1.10 -4 Hz should be not assessed with pure creep crack results or sufficient safety margins have to be applied. (orig.)

Mechanical properties of irradiated 9Cr-2WVTa steel

International Nuclear Information System (INIS)

Klueh, R.L.; Alexander, D.J.; Rieth, M.

1998-01-01

An Fe-9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa) steel has excellent strength and impact toughness before and after irradiation in the Fast Flux Test Facility and the High Flux Reactor (HFR). The ductile-brittle transition temperature (DBTT) increased only 32 C after 28 dpa at 365 C in FFTF, compared to a shift of ∼60 C for a 9Cr-2WV steel--the same as the 9Cr-2WVTa steel but without tantalum. This difference occurred despite the two steels having similar tensile but without tantalum. This difference occurred despite the two steels having similar tensile properties before and after irradiation. The 9Cr-2WVTa steel has a smaller prior-austenite grain size, but otherwise microstructures are similar before irradiation and show similar changes during irradiation. The irradiation behavior of the 9Cr-2WVTa steel differs from the 9Cr-2WV steel and other similar steels in two ways: (1) the shift in DBTT of the 9Cr-2WVTa steel irradiated in FFTF does not saturate with fluence by ∼28 dpa, whereas for the 9Cr-2WV steel and most similar steels, saturation occurs at <10 dpa, and (2) the shift in DBTT for 9Cr-2WVTa steel irradiated in FFTF and HFR increased with irradiation temperature, whereas it decreased for the 9Cr-2WV steel, as it does for most similar steels. The improved properties of the 9Cr-2WVTa steel and the differences with other steels were attributed to tantalum in solution

Fatigue resistance of Cr-Ni-Mo-V steel

International Nuclear Information System (INIS)

Naumchenkov, N.E.; Filimonova, O.V.; Borisov, I.A.

1985-01-01

A study was made on the effect of additional alloying (Ni, Ni+Co), stress concentration, surface plastic strain on fatigue resistance of rotor steel of Cr-Ni-Mo-V-composition. It is shown that the steel with decreased carbon content possesses high complex of mechanical properties. Fatigue characteristics are not inferior to similar characteristics of steels of 25KhN3MFA type. Additional alloying of the steel containing 0.11...0.17% C and 4.5...4.7% N:, with niobium separately or niobium and cobalt in combination enabled to improve fatigue resistance of samles up to 25%. Strengthening of stress concentration zones by surface plastic strain is recommended for improving rotor suppporting 'nower under cyclic loading

Welding of heterogeneous 12Kh2MFSR steels with the Mn-Cr-Si-Ni system

International Nuclear Information System (INIS)

Smirnov, A.N.; Belogolov, E.I.

1978-01-01

The process of welding pipes of the 12Kh2MFSR pearlitic steels and austenitic steels of the Mn-Cr-Si-Ni system was studied. The filler materials were selected, and the working capacity of welded joints was examined in ageing and cyclic heatings. The microhardness of steels was measured, and the ultimate strength of welded joints was determined. The following has been established: the composite joints of steels of the Mn-Cr-Si-Ni system and 12Kh2MFSR steel are advisable to be welded on a coating layer welded by the EhA395/9 electrodes on the surface of a pipe of the 12Kh2MFSR pearlitic steel; this guarantees the sufficient working capacity of welded joints

Random cyclic constitutive models of 0Cr18Ni10Ti pipe steel

International Nuclear Information System (INIS)

Zhao Yongxiang; Yang Bing

2004-01-01

Experimental study is performed on the random cyclic constitutive relations of a new pipe stainless steel, 0Cr18Ni10Ti, by an incremental strain-controlled fatigue test. In the test, it is verified that the random cyclic constitutive relations, like the wide recognized random cyclic strain-life relations, is an intrinsic fatigue phenomenon of engineering materials. Extrapolating the previous work by Zhao et al, probability-based constitutive models are constructed, respectively, on the bases of Ramberg-Osgood equation and its modified form. Scattering regularity and amount of the test data are taken into account. The models consist of the survival probability-strain-life curves, the confidence strain-life curves, and the survival probability-confidence-strain-life curves. Availability and feasibility of the models have been indicated by analysis of the present test data

Mechanical properties of steel 8 CrMoNiNb 9 10 in dependence on the microstructural condition

International Nuclear Information System (INIS)

Fabritius, H.; Schnabel, E.

1976-01-01

Tension tests at room temperature to 600 0 C and creep-rupture tests at 500 to 600 0 C lasting up to about 75,000 h on two casts of steel 8 CrMoNiNb 9 10 with about 0.08% C, 0.3% Si, 0.7% Mn, 0.012% N, 0.005% Al, 2.34% Cr, 0.95% Mo, 0.8% Nb and 0.64% Ni in bainitic and ferritic microstructural condition. Influence of annealing at 650 to 800 0 C on the properties in the tension test. Influence of aging at 500 to 600 0 C lasting up to 30,000 h with and without mechanical stress on the properties in the tension test at aging temperature and on the toughness behaviour in the notched bar impact bend test at room temperature. (orig.) [de

The characteristics of precipitates in 18% Cr/30% Ni cast steel with additions of Nb and Ti

International Nuclear Information System (INIS)

Piekarski, B.

1995-01-01

The microstructure of austenitic cast steel with approx. 0.3%C, 4.37%Si, 0.69%Mn, 17.8%Cr, 29.3%Ni, 1.47%Nb and 1.07%Ti have been examined after ageing at 900 C for 300 h. There was found five precipitates: M 23 C 6 , MnS, Ni 3 Fe, (Ti,Nb)C and an intermetallic Ni-Nb-S phase. Ni, Nb, Si-rich precipitate could have been formed in as cast condition. (author)

The Phase Transformations in Hypoeutectoid Steels Mn-Cr-Ni

Directory of Open Access Journals (Sweden)

RoŻniata E.

2015-04-01

Full Text Available The results of a microstructure and hardness investigations of the hypoeutectoid steels Mn-Cr-Ni, imitating by its chemical composition toughening steels, are presented in the paper. The analysis of the kinetics of phase transformations of undercooled austenite of steels containing different amounts of alloying elements in their chemical composition, constitutes the aim of investigations.

Formed electroslag welded joint from austenitic steel 18/10 CrNi

International Nuclear Information System (INIS)

Jilek, L.; Kusak, L.; Martinak, A.

1987-01-01

The electroslag welded joint from titanium stabilized steel 18/10 CrNi of 150 mm in thickness showed positive results for both nondestructive and destructive testing. Czechoslovak flux VUZ-4F and the optimized welding mode were completely proven. The weldment was subject to deformation by forging with a removal of 20 to 50% and to bending deformation. A 40% to 50% deformation was necessary for breaking the coarse-grain casting structure. The bending deformation resulted in breaking the coarse-grain casting structure in the entire cross-section, it was, however, only acting in a narrow band corresponding to the largest curvature. At the same time, the heat affected zone decayed. Following heat treatment, especially forming, the delta ferrite content in the weld metal decreased, the mechanical properties of the weld metal and the welded joint following welding and heat treatment showed a relatively large scatter. Forming reduced the scatter and improved plastic properties. Machining within 40 and 50% resulted in good echogenicity of the welded joint in ultrasound testing. The welded joint showed equal properties as the base material of the weldment. (author). 15 figs., 2 tabs., 16 refs

Z-phase in 9-12% Cr Steels

DEFF Research Database (Denmark)

Danielsen, Hilmar; Hald, John

2004-01-01

The complex nitride Z-phase, Cr(V,Nb)N, has recently been identified as a major cause for premature breakdown in creep strength of a number of new 9-12%Cr martensitic steels. A thermodynamic model of the Z-phase has been created based on the Thermo-Calc software. The model predicts the Z-phase to......The complex nitride Z-phase, Cr(V,Nb)N, has recently been identified as a major cause for premature breakdown in creep strength of a number of new 9-12%Cr martensitic steels. A thermodynamic model of the Z-phase has been created based on the Thermo-Calc software. The model predicts the Z......-phase to be stable in all of the new 9-12%Cr martensitic steels. This has generally been confirmed by the performed experiments. Z-phase precipitation seems to be a kinetic problem, and drivning force calculations using Thermo-Calc with the developed model have been used to predict steel compositions, which...

Behaviour of Z phase in 9–12%Cr steels

DEFF Research Database (Denmark)

Danielsen, Hilmar Kjartansson; Hald, John

2006-01-01

The literature on the behaviour of modified Z phase Cr(V,Nb)N in creep resistant martensitic 9–12%Cr steels is briefly reviewed. Ten different 9–12%Cr steels were investigated after prolonged exposure at 600–660uC; the modified Z phase was found in all of them. In steels with high Cr content (11......–12%), Z phase precipitates much faster than in 9%Cr steels. Precipitation of Z phase is associated with dissolution of MX carbonitrides, and causes a breakdown in long term creep strength in 9–12%Cr steels. High Cr steels show creep instabilities accompanied with Z phase precipitation, whereas low Cr...... steels show good long term creep stability. A niobium free CrVN variant of the modified Z phase was observed for the first time during the course of this work. The solution temperature of the Cr(V,Nb)N and CrVN modified Z phases was found to be close to 800uC for 11–12%Cr steels, much lower than the 1200...

Microstructural Characterization of Clad Interface in Welds of Ni-Cr-Mo High Strength Low Alloy Steel

Energy Technology Data Exchange (ETDEWEB)

Kim, Hong-Eun; Kim, Min-Chul; Lee, Ho-Jin; Kim, Keong-Ho [KAERI, Daejeon (Korea, Republic of); Lee, Ki-Hyoung [KAIST, Daejeon (Korea, Republic of); Lee, Chang-Hee [Hanyang Univ., Seoul (Korea, Republic of)

2011-08-15

SA508 Gr.4N Ni-Cr-Mo low alloy steel, in which Ni and Cr contents are higher than in commercial SA508 Gr.3 Mn-Mo-Ni low alloy steels, may be a candidate reactor pressure vessel (RPV) material with higher strength and toughness from its tempered martensitic microstructure. The inner surface of the RPV is weld-cladded with stainless steels to prevent corrosion. The goal of this study is to evaluate the microstructural properties of the clad interface between Ni-Cr-Mo low alloy steel and stainless weldment, and the effects of post weld heat treatment (PWHT) on the properties. The properties of the clad interface were compared with those of commercial Mn-Mo-Ni low alloy steel. Multi-layer welding of model alloys with ER308L and ER309L stainless steel by the SAW method was performed, and then PWHT was conducted at 610°C for 30 h. The microstructural changes of the clad interface were analyzed using OM, SEM and TEM, and micro-Vickers hardness tests were performed. Before PWHT, the heat affected zone (HAZ) showed higher hardness than base and weld metals due to formation of martensite after welding in both steels. In addition, the hardness of the HAZ in Ni-Cr-Mo low alloy steel was higher than that in Mn-Mo-Ni low alloy steel due to a comparatively high martensite fraction. The hardness of the HAZ decreased after PWHT in both steels, but the dark region was formed near the fusion line in which the hardness was locally high. In the case of Mn-Mo-Ni low alloy steel, formation of fine Cr-carbides in the weld region near the fusion line by diffusion of C from the base metal resulted in locally high hardness in the dark region. However, the precipitates of the region in the Ni-Cr-Mo low alloy steel were similar to that in the base metal, and the hardness in the region was not greatly different from that in the base metal.

Microstructural Characterization of Clad Interface in Welds of Ni-Cr-Mo High Strength Low Alloy Steel

International Nuclear Information System (INIS)

Kim, Hong-Eun; Kim, Min-Chul; Lee, Ho-Jin; Kim, Keong-Ho; Lee, Ki-Hyoung; Lee, Chang-Hee

2011-01-01

SA508 Gr.4N Ni-Cr-Mo low alloy steel, in which Ni and Cr contents are higher than in commercial SA508 Gr.3 Mn-Mo-Ni low alloy steels, may be a candidate reactor pressure vessel (RPV) material with higher strength and toughness from its tempered martensitic microstructure. The inner surface of the RPV is weld-cladded with stainless steels to prevent corrosion. The goal of this study is to evaluate the microstructural properties of the clad interface between Ni-Cr-Mo low alloy steel and stainless weldment, and the effects of post weld heat treatment (PWHT) on the properties. The properties of the clad interface were compared with those of commercial Mn-Mo-Ni low alloy steel. Multi-layer welding of model alloys with ER308L and ER309L stainless steel by the SAW method was performed, and then PWHT was conducted at 610°C for 30 h. The microstructural changes of the clad interface were analyzed using OM, SEM and TEM, and micro-Vickers hardness tests were performed. Before PWHT, the heat affected zone (HAZ) showed higher hardness than base and weld metals due to formation of martensite after welding in both steels. In addition, the hardness of the HAZ in Ni-Cr-Mo low alloy steel was higher than that in Mn-Mo-Ni low alloy steel due to a comparatively high martensite fraction. The hardness of the HAZ decreased after PWHT in both steels, but the dark region was formed near the fusion line in which the hardness was locally high. In the case of Mn-Mo-Ni low alloy steel, formation of fine Cr-carbides in the weld region near the fusion line by diffusion of C from the base metal resulted in locally high hardness in the dark region. However, the precipitates of the region in the Ni-Cr-Mo low alloy steel were similar to that in the base metal, and the hardness in the region was not greatly different from that in the base metal.

Optimizing Heat Treatment Process of Fe-13Cr-3Mo-3Ni Martensitic Stainless of Steel

Science.gov (United States)

Anwar, M. S.; Prifiharni, S.; Mabruri, E.

2017-05-01

The Fe-13Cr-3Mo-3Ni stainless steels are modified into martensitic stainless steels for steam turbine blades application. The working temperature of steam turbine was around 600 - 700 °C. The improvement properties of turbine blade material is necessary to maintain steam turbine work. The previous research revealed that it has corrosion resistance of Fe-13Cr-3Mo-3Ni which is better than 13Cr stainless steels in the chloride environment. In this work, the effect of heat treatment on microstructure and hardness of Fe-13Cr-3Mo-3Ni stainless steels has been studied. The steel was prepared by induction melting followed by hot forging. The steels were austenitized at 1000, 1050, and 1100 °C for 1 hour and were tempered at 600, 650, and 700 °C for 1 hour. The steels were then subjected to metallographic observation and hardness test of Rockwell C. The optimal heat treatment of Fe-13Cr-3Mo-3Ni was carried out austenitized in 1050 °C and tempered in 600 - 700 °C.

Electron-beam welding of 21-6-9 (Cr--Ni--Mn) stainless steel: effect of machine parameters on weldability

International Nuclear Information System (INIS)

Casey, H.

1975-04-01

The high-manganese, nitrogen-strengthened 21-6-9 (Cr--Ni--Mn) austenitic stainless steel has a weldability rating similar to that of more common austenitic stainless steels in terms of cracking, porosity, etc. However, weld pool disruption problems may occur with this alloy that can be related to instability within the molten weld pool. Selection of machine parameters is critical to achieving weld pool quiescence as this report confirms from recent tests. Test samples came from heats of air-melted, vacuum-arc remelted, and electroslag remelted material. Low- and high-voltage machine parameters are discussed, and effects of parameter variation on weld pool behavior are given. Data relate weld pool behavior to weld fusion-zone geometry. Various weld parameters are recommended for the 21-6-9 alloy, regardless of its source or chemistry. (auth)

Development of improved HP/IP rotor material 2% CrMoNiWV (23 CrMoNiWV 88)

International Nuclear Information System (INIS)

Wiemann, W.

1989-01-01

The new 2% CrMoNiWV steel has a sufficient strength level, a very good creep (rupture) behaviour and an excellent toughness behaviour for a creep resistant steel. Even after long time high temperature exposure the toughness degradation is so small that it is still better than this of best 1% CrMo(Ni)V steels. The fatigue behaviour is well comparable to this of 1% CrMo(Ni)V. The 2% CrMoNiWV steel has the capability to substitute the traditional 1% CrMo(Ni)V. (orig.) With 26 annexes

Improved hardness of laser alloyed X12CrNiMo martensitic stainless steel

CSIR Research Space (South Africa)

Adebiyi, DI

2011-07-01

Full Text Available The improvement in hardness of X12CrNiMo martensitic stainless steel laser alloyed with 99.9% pure titanium carbide, stellite 6 and two cases of premixed ratio of titanium carbide and stellite 6 [TiC (30 wt.%)- stellite 6 (70 wt.%) and TiC (70 wt...

Corrosion resistance of stainless steels and high Ni-Cr alloys to acid fluoride wastes

International Nuclear Information System (INIS)

Smith, H.D.; Mackey, D.B.; Pool, K.H.; Schwenk, E.B.

1992-04-01

TRUEX processing of Hanford Site waste will utilize potentially corrosive acid fluoride processing solutions. Appropriate construction materials for such a processing facility need to be identified. Toward this objective, candidate stainless steels and high Ni-Cr alloys have been corrosion tested in simulated acid fluoride process solutions at 333K. The high Ni-Cr alloys exhibited corrosion rates as low as 0.14 mm/y in a solution with an HF activity of about 1.2 M, much lower than the 19 to 94 mm/y observed for austenitic stainless steels. At a lower HF activity (about 0.008 M), stainless steels display delayed passivation while high Ni-Cr alloys display essentially no reaction

Effect of cloric acid concentration on corrosion behavior of Ni/Cr coated on carbon steel

Science.gov (United States)

Desiati, Resetiana Dwi; Sugiarti, Eni; Thosin, K. A. Zaini

2018-05-01

Corrosion is one of the causes of metal degradation. Carbon steel (Fe) is easy to corrode in the extreme environment. Coating on carbon steel is required to improve corrosion resistance owing to protection or hindrance to extreme environmental conditions. In this present work, carbon steel was coated by electroplating techniques for nickel and pack cementation for chrome. The corrosion rate test was performed by Weight Loss method on FeNiCr, FeNi, FeCr and uncoated Fe as comparator which was dyed in 37% HCl and 25% HCl which had previously been measured dimension and mass. The immersion test result of FeNiCr and FeNi specimen were better than FeCr and uncoated Fe in terms of increasing corrosion resistance. The corrosion rate for 56 hours in 37% HCl for FeNiCr was 1.592 mm/y and FeNi was 3.208 mm/y, FeCr only lasted within 32 hours with corrosion rate was 6.494 mm/y. Surface of the sample after the corrosion test there was pitting, crevice corrosion and alloy cracking caused by chloride. The higher the concentration of HCl the faster the corrosion rate.

Determination of chemical activities of Fe, Cr, Ni and Mn in stainless steel 316 by Knudsen effusion cell mass spectrometry

International Nuclear Information System (INIS)

Venugopal, V.; Kulkarni, S.G.; Subbanna, C.S.; Sood, D.D.

1995-01-01

Cold-worked austenitic stainless steel of the type AISI 316 is being used as the cladding and wrapper materials in fast reactor fuel pins. Knowledge of the thermodynamic activities of the steel constituents is necessary to predict the possibility of fuel-cladding, coolant-cladding or fission product-cladding chemical reactions. The thermodynamic activities of Fe, Cr, Ni and Mn for stainless steel 316 were determined by measuring their partial pressures in the temperature range 1293-2120 K, using Knudsen effusion cell mass spectrometry. High purity Ag was used as an internal calibrant. The chemical activities of Fe (a Fe ), Cr (a Cr ), Ni (a Ni ) and Mn (a Mn ) were evaluated using literature data for the vapour pressures of pure metals. log a Fe ±0.18=-1.586+2074/T (T=1293-1872 K)log a Cr ±0.30=-2.350+2612/T (T=1293-2120 K)log a Ni ±0.20=-2.140+1794/T (T=1468-1974 K)log a Mn ±0.23=-2.041-5478/T (T=1302-1894 K) ((orig.))

Enhancement of tribological properties of 9Cr18 stainless steel by dual Mo and S Co implantation

International Nuclear Information System (INIS)

Zhang Tao; Song Jiaohua; Li Guoqing; Chu, Paul K.; Brown, Ian G.

2001-01-01

Mo and S ions were simultaneously implanted into 9Cr18 stainless steel samples. The frictional properties of the implanted samples were assessed using a pin-on-disk tester and the elemental depth profiles were measured by Auger electron spectroscopy. The hardness of the samples was also measured. We find that this dual-element implantation process reduces the coefficient of friction by a factor of 2 and increases the low-friction lifetime by a factor of 4 compared to the 9Cr18 surface with Mo or S implantation alone. This enhancement is related to the synergistic coexistence of the implanted elements at the same place. We have also investigated the process using computer simulation. The simulation results help disclose the characteristics of the modified layer and explain the effects of dual-element ion implantation

The Effect of Si and Mn on Microstructure and Selected Properties of Cr-Ni Stainless Steels

Directory of Open Access Journals (Sweden)

Kalandyk B.

2017-03-01

Full Text Available Cast stainless steel of the Cr-Ni duplex type is used, among others, for the cast parts of pumps and valves handling various chemically aggressive media. Therefore, the main problem discussed in this article is the problem of abrasion wear resistance in a mixture of SiC and water and resistance to electrochemical corrosion in a 3% NaCl-H2O solution of selected cast steel grades, i.e. typical duplex cast steel, high silicon and manganese duplex cast steel, and Cr-Ni austenitic cast steel (type AISI 316L. The study shows that the best abrasion wear resistance comparable to Ni-Hart cast iron was obtained in the cast duplex steel, where Ni was partially replaced with Mn and N. This cast steel was also characterized by the highest hardness and matrix microhardness among all the tested cast steel grades. The best resistance to electrochemical corrosion in 3% NaCl-H2O solution showed the cast duplex steel with high content of Cr, Mo and N. The addition of Ni plays rather insignificant role in the improvement of corrosion resistance of the materials tested.

Formability of high-alloy dual-phase Cr-Ni steels

International Nuclear Information System (INIS)

Elfmark, J.

2004-01-01

The formability of dual-phase high-alloy Cr-Ni steel within the temperature range from 900 to 1250 C was studied using laboratory tensile and torsion tests. The dual-phase steels on 24% Cr basis are characterized by poor hot formability due to very low stable deformation values and slow recrystallization. Mathematical description of deformation stability exhaustion was derived, as well as a model of formability control based on analysis of the gradual diffuse deformation stability from the stability limit to the moment when the deformation starts to concentrate in a small volume of the test piece. Rolling simulation of dual-phase steel strip was used as an example demonstrating the draught scheme optimization technique which avoids the danger of crack occurrence during the rolling of dual-phase steel strip. (orig.)

Chemical diffusion of Cr, Ni and Si in welded joints. II

International Nuclear Information System (INIS)

Kucera, J.; Ciha, K.

1987-01-01

The results are given of a study in chemical diffusion in welded joints P2/A and P3/A. P2 stands for the steel (Fe-17.48 Cr-8.15 Ni-0.14 Si), P3 for (Fe-18.52 Cr-8.20 Ni-1.78 Si) and A for the Fe-Arema. Triadic sandwiche-like samples were diffusion heated at temperatures from 920 to 1170 degC. The concentration distributions N(x,t) of the given elements were measured with microprobe JXA-3A. The evaluation of the experimental data was carried out either by Grube's method, or in some cases by the spline-polynomial method. The evaluated diffusivities D-bar satisfy the Arrhenius relation and yield the standard diffusion characteristics D 0 and H. The diffusivities D-bar of Cr, Ni and Si in P1/A, in P2/A and P3/A welded joints vary with Si content in P1, P2 and P3 alloys, similar to the Cr-51 and Ni-63 self-diffusivities in Fe-18 Cr-12 Ni-X Si steels, and tend to increase with increasing Si content. The values D-bar measured in the vicinity of grain boundaries are higher than the bulk diffusion coefficients. The most rapid diffusant is Si and the slowest one Ni. Thus, the relations D-bar Si :D-bar Cr :D-bar Ni ≅ 6:3:1 (P3/A) and D-bar Si :D-bar Cr :D-bar Ni ≅ 1.7:1.4:1 (P3/A) are valid at 1050 degC. Comparing the results with those published if can be noted that the Cr-51 and Ni-63 self-diffusion in Fe-18 Cr-12 Ni-X Si steels is faster than chemical diffusion of these elements in the said steel welded joints P2/A and P3/A; X varies from 0.14 to 1.98. (author). 7 tabs., 7 figs., 20 refs

Effect of cold deformation on latent energy value and high-temperature mechanical properties of 12Cr18Ni10Ti steel

International Nuclear Information System (INIS)

Maksimkin, O.P.; Shiganakov, Sh.B.; Gusev, M.N.

1997-01-01

Energetic and magnetic characteristics and also the high-temperature mechanical properties depending on the preliminary cold deformation of 12Cr18Ni10Ti steel are presented. It is shown that the value of storage energy in the steel has being grown with increase of the deformation. The rate of its growth has been increased after beginning of martensitic γ→α'- transformation when value of comparative storage energy at first decreased and then has been stay practically constant. Level of mechanical properties of the steel at 1073 K has been determined not only by value of cold deformation but and structural reconstruction corresponding to deformations 35-45% and accompanying with α'-phase martensite formation and change of energy accumulating rate. Preliminary cold deformation (40-60 %) does not improve high- temperature plasticity of steel samples implanted by helium. refs. 7, figs. 2

Precipitation hardening in a 12%Cr-9%Ni-4%Mo-2%Cu stainless steel

International Nuclear Information System (INIS)

Haettestrand, Mats; Nilsson, Jan-Olof; Stiller, Krystyna; Liu Ping; Andersson, Marcus

2004-01-01

A combination of complementary techniques including one-dimensional and three-dimensional atom probe, energy-filtered transmission electron microscopy and conventional transmission electron microscopy has been used to assess the precipitation reactions at 475 deg. C in a 12%Cr-9%Ni-4%Mo-2%Cu precipitation hardening stainless steel. The continuous hardening up to at least 1000 h of ageing was attributed to a sequence of precipitation reactions involving nickel-rich precipitates nucleating at copper clusters followed by molybdenum-rich quasicrystalline precipitates and nickel-rich precipitates of type L1 0 . An estimate of the relative contributions to the strength increment during tempering based on measurements of particle densities was performed. Nickel-rich precipitates were found to play the most important role up to about 40 h of ageing after which the effect of quasicrystalline particles became increasingly important

Gradient microstructure and microhardness in a nitrided 18CrNiMo7-6 gear steel

Science.gov (United States)

Yang, R.; Wu, G. L.; Zhang, X.; Fu, W. T.; Huang, X.

2017-07-01

A commercial gear steel (18CrNiMo7-6) containing a tempered martensite structure was nitrided using a pressurized gas nitriding process under a pressure of 5 atm at 530 °C for 5 hours. The mechanical properties and microstructure of the nitrided sample were characterized by Vickers hardness measurements, X-ray diffraction, and backscatter electron imaging in a scanning electron microscope. A micro-hardness gradient was identified over a distance of 500 μm with hardness values of 900 HV at the top surface and 300 HV in the core. This micro-hardness gradient corresponds to a gradient in the microstructure that changes from a nitride compound layer at the top surface (∼ 20 μm thick) to a diffusion zone with a decreasing nitrogen concentration and precipitate density with distance from the surface, finally reaching the core matrix layer with a recovered martensite structure.

Spectroscopic characterisation of iodine deposits on 18%Cr/8%Ni and mild steel surfaces oxidised in CO2/CH3I gas mixtures

International Nuclear Information System (INIS)

Tyler, J.W.

1987-08-01

An understanding and quantification of iodine-131 attenuation within the gas circuit of a Commercial Advanced Gas-cooled Reactor is required for reactor safety assessments. To this end it is desirable to identify the chemical state of iodine in the gas phase or when deposited on reactor surfaces. Samples of 18%Cr/8%Ni and mild steel pipe, with iodine deposited on their surfaces following oxidation in CO 2 /CH 3 I gas mixtures, have been characterised in the present work using a variety of different spectroscopic techniques including X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, scanning Auger microscopy and X-ray diffraction. The chemical nature of the deposited iodine has been determined by X-ray photoelectron spectroscopy to be a metal iodide by correlating I 3d binding energies with those obtained from well characterised standards; the binding energies of the ejected I 3d photoelectrons being sensitive to the chemical environment experienced by the iodine atoms. The distribution of iodine throughout the oxide layers formed on these steels was determined by repeated cycles of argon-ion bombardment and analysis to build up an elemental depth profile whilst at the same time determining the chemical state of the elements present. Differences in oxide composition and morphology are discussed in relation to the deposition behaviour observed on 18%Cr/8%Ni and mild steel and it is suggested that gradual incorporation of the iodine occurs throughout the oxidation/deposition period. (U.K.)

The effect of cobalt and molybdenum on the creep strength of low C-18Cr-10Ni steel

International Nuclear Information System (INIS)

Tomono, Yutaka; Ueda, Jitsuhiko

1982-01-01

The improvement of creep strength through the addition of cobalt and molybdenum to low C-18Cr-10Ni steel was studied at a temperature range of between 700 and 800 0 C. Changes in mechanical and physical properties such as lattice parameter and stacking fault energy, related to the additional elements were investigated to estimate the strengthening effect. Dislocation structures corresponding to the various creep stages were observed through a transmission electron microscope to distinguish the solution hardening effect of the added elements from the precipitation hardening effects of carbide. The results obtained are summarized as follows: (1) Addition of cobalt of up to 20% by weight improved the creep strength of austenitic steel. Addition of molybdenum of up to 5% by weight remarkably improved the creep strength of austenitic steel having a cobalt content of 20% by weight. (2) The trend for creep strength to improve with the addition of these elements was closely coincident with increases in lattice parameter and did not necessarily coincide with changes in the stacking fault energy. (author)

Substitution of modified 9 Cr-1 Mo steel for austentic stainless steels

International Nuclear Information System (INIS)

Sikka, V.K.

1982-04-01

This report describes the current program to develop a high-strength ferritic-martensitic steel. The alloy is essentially Fe-9% Cr-1% Mo with small additions of V and Nb and is known as modifed 9 Cr-1 Mo steel. Its elevated-temperature properties and design allowable stresses match those of type 304 stainless steel for temperatures up to 600 0 C and exceed those of other ferritic steels by factors of 2 to 3. The improved strength of this alloy permits its use in place of stainless steels for many applications

Optimum alloy compositions in reduced-activation martensitic 9Cr steels for fusion reactor

International Nuclear Information System (INIS)

Abe, F.; Noda, T.; Okada, M.

1992-01-01

In order to obtain potential reduced-activation ferritic steels suitable for fusion reactor structures, the effect of alloying elements W and V on the microstructural evolution, toughness, high-temperature creep and irradiation hardening behavior was investigated for simple 9Cr-W and 9Cr-V steels. The creep strength of the 9Cr-W steels increased but their toughness decreased with increasing W concentration. The 9Cr-V steels exhibited poor creep rupture strength, far below that of a conventional 9Cr-1MoVNb steel and poor toughness after aging at 873 K. It was also found that the Δ-ferrite should be avoided, because it degraded both the roughness and high-temperature creep strength. Based on the results on the simple steels, optimized martensitic 9Cr steels were alloy-designed from a standpoint of enough thoughness and high-temperature creep strength. Two kinds of optimized 9Cr steels with low and high levels of W were obtained; 9Cr-1WVTa and 9Cr-3WVTa. These steels indeed exhibited excellent toughness and creep strength, respectively. The 9Cr-1WVTa steel exhibiting an excellent roughness was shown to be the most promising for relatively low-temperature application below 500deg C, where irradiation embrittlement is significant. The 9Cr-3WVTa steel was the most promising for high temperature application above 500deg C from the standpoint of enough high-temperature strength. (orig.)

[Studies on the tolerance of the organism to X 5 CrNiMo 18.10 steel (Königsee). II. Light microscopic studies of the surrounding tissue of metal implants (X 5 CrNiMo 18.10 steel) in guinea pigs].

Science.gov (United States)

Höhndorf, H; Drössler, K; Stiehl, P

1977-06-01

The tissue around X 5 CrNiMo 18.10-steel implantates with different surfaces was examined in 72 guinea-pigs. Aside from controls, these animals were preoperatively sensibilized against chromium and nickel. The results can be summarized since the histologic findings showed no different peculiarities. The authors describe an intussusception of the implantate in connective tissue which evidently depends on time and surface. Further the spreading of alien material in the surrounding of the implantate, and morphologic findings are reported. The morphologic evidences are described and discussed in detail, since they are interpreted as signs of cell-mediated immune reactions. The presence of lymphocytes, lymphoblasts, histiocytes (mostly carrying alien material), and granulocytes, as well as proliferations at the arterioles suggest an overlapping of immune reactions.

Fatigue damage evolution of cold-worked austenitic nickel-free high-nitrogen steel X13CrMnMoN18-14-3 (1.4452)

Energy Technology Data Exchange (ETDEWEB)

Tikhovskiy, I.; Weiss, S.; Fischer, A. [Univ. of Duisburg-Essen, Materials Science and Engineering II, Duisburg (Germany)

2004-07-01

Due to the fact that the risk of Ni-allergies becomes more and more important for modern therapies, the necessity of Ni-free implant materials becomes increasingly important. Beside Co- and Ti-base alloys Ni-free high-nitrogen steels may offer an attractive alternative. The present work presents the austenitic high-nitrogen and nickel-free steel X13CrMnMoN18-14-3, (Material No.: 1.4452) after 20% cold-working. In addition this material was deformed under axial cyclic total strain controlled fatigue tests at room temperature. The development of dislocation structure due to different loading amplitudes was compared to none cyclically deformed material. The good mechanical und fatigue properties of these austenitic high-nitrogen steels as well as the better tribological, chemical and biological properties compared to CrNiMo-steels qualify these steels as a promising alternative in medical applications. (orig.)

A Weakest-Link Approach for Fatigue Limit of 30CrNiMo8 Steels (Preprint)

Science.gov (United States)

2011-03-01

34Application of a Weakest-Link Concept to the Fatigue Limit of the Bearing Steel Sae 52100 in a Bainitic Condition," Fatigue and Fracture of...AFRL-RX-WP-TP-2011-4206 A WEAKEST-LINK APPROACH FOR FATIGUE LIMIT OF 30CrNiMo8 STEELS (PREPRINT) S. Ekwaro-Osire and H.V. Kulkarni Texas...2011 4. TITLE AND SUBTITLE A WEAKEST-LINK APPROACH FOR FATIGUE LIMIT OF 30CrNiMo8 STEELS (PREPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT

Effect of heat treatment on workability of Cr-Ni-Mo steels

International Nuclear Information System (INIS)

Barcal, J.; Macek, K.

1988-01-01

The workability was studied of the new development generation of hardenable martensite Cr-Ni-Mo steels of the 10-10-2 and 6-11-3 types whose application is envisaged in future in nuclear engineering. Attention is paid to identification of inclusions and the phase analysis ofthe structure with respect to heat treatment and steel type. Face milling was used in the test of workability. In addition, tensile strength and impact bending strength testing was performed. The results showed that steel of the 6-11-3 type in the quenched condition was best workable. However, this steel showed a significant reduction in workability when in the hardened condition. Reduced workability can also be presumed for type 10-10-2 steel in the hardened condition when life is considered. Microstructure changes leading to softening of steel by aging had a favourable effect on workability, especially in steels of the 10-10-2 type. Hardened steels of the 6-11-3 type are recommended to be re-quenched. (Z.M.). 7 figs., 3 tabs., 9 refs

The research of axial corrosion fatigue on 10Ni3CrMoV steel

Science.gov (United States)

Xie, Xing; Yi, Hong; Xu, Jian; Xie, Kun

2017-09-01

Fatigue life had been studied with 10CrNi3MoV steel at different load ratios and in different environmental medias. The microstructure and micro-topography had been observed and analyzed by means of SEM, EDS and TEM. Our findings indicated that, the fatigue life of 10Ni3CrMoV steel in seawater was shorter than in air, the difference in longevity was larger with the decreasing of axis stress. Corrosion pits had a great influence on corrosion fatigue life.

Applicability of the θ projection method to creep curves of Ni-22Cr-18Fe-9Mo alloy

International Nuclear Information System (INIS)

Kurata, Yuji; Utsumi, Hirokazu

1998-01-01

Applicability of the θ projection method has been examined for constant-load creep test results at 800 and 1000degC on Ni-22Cr-18Fe-9Mo alloy in the solution-treated and aged conditions. The results obtained are as follows: (1) Normal type creep curves obtained at 1000degC for aged Ni-22Cr-18Fe-9Mo alloy are fitted using the θ projection method with four θ parameters. Stress dependence of θ parameters can be expressed in terms of simple equations. (2) The θ projection method with four θ parameters cannot be applied to the remaining creep curves where most of the life is occupied by a tertiary creep stage. Therefore, the θ projection method consisting of only the tertiary creep component with two θ parameters was applied. The creep curves can be fitted using this method. (3) If the θ projection method with four θ or two θ parameters is applied to creep curves in accordance with creep curve shapes, creep rupture time can be predicted in terms of formulation of stress and/or temperature dependence of θ parameters. (author)

A New Method to Produce Ni-Cr Ferroalloy Used for Stainless Steel Production

Science.gov (United States)

Chen, Pei-Xian; Chu, Shao-Jun; Zhang, Guo-Hua

2016-08-01

A new electrosilicothermic method has been proposed in the present paper to produce Ni-Cr ferroalloy, which can be used for the production of 300 series stainless steel. Based on this new process, the Ni-Si ferroalloy is first produced as the intermediate alloy, and then the desiliconization process of Ni-Si ferroalloy melt with chromium concentrate is carried out to generate Ni-Cr ferroalloy. The silicon content in the Ni-Si ferroalloy produced in the submerged arc furnace should be more than 15 mass% (for the propose of reducing dephosphorization), in order to make sure the phosphorus content in the subsequently produced Ni-Cr ferroalloy is less than 0.03 mass%. A high utilization ratio of Si and a high recovery ratio of Cr can be obtained after the desiliconization reaction between Ni-Si ferroalloy and chromium concentrate in the electric arc furnace (EAF)-shaking ladle (SL) process.

Heterogeneity of structure and properties of 12Cr18Ni10Ti and 08Cr16Ni11Mo3 stainless steels irradiated up to high damaging doses in reactor Bn-350

International Nuclear Information System (INIS)

Maksimkin, O.P.; Tivanova, O.V.; Turubarova, L.G.; Silnyagina, N.S.; Doronina, T.A.

2006-01-01

Full text: Earlier, during investigation of post-operating properties and structure of responsible units of fast neutron reactors there was shown /1, 2/ that depending on character of preliminary treatment of austenite stainless steel (austenization, cold deformation, mechanical and thermal treatment) radiation effects could be different. In /2/ one could observe heterogeneity at swelling of cold- worked hexahedral ducts along perimeter, in particular, the swelling of corners was less than plates'. At the same time after mechanical-thermal treatment the corners swell in 3-5 times of magnitude higher than plates. By the present there are several assumptions about nature of this phenomenon. One of them is a difference of deformation degree of material in corners and plates of the duct. It is known that /3/ external effects (including deformation) induce martensitic γ→α transformation in austenitic steels, due to which the structure and properties of steel are changed. In particular, paramagnetic FCC matrix reveals sites with ferromagnetic BCC structure. Steel heating, containing martensitic α-phase higher than ∼ 450-800 deg C, results in reverse γ→α transformation in material, which in its turn leads to formation of phase phase-hardened austenite. We can expect that only peculiarities of processes of direct and reverse martensitic transformations, which took place during preliminary austenitic steel treatment, will predetermine its behavior under irradiation. Taking into account the above mentioned there have been carried out complex material-scientific investigations of 12Cr18Ni10Ti and 08Cr16Ni11Mo3 steel samples cut off from different sites (both adjacent to corners and far from them) of hexagonal ducts of spent fuel assemblies of BN-350 reactor. There were used samples in the form of plates of different sizes: 5x10x2 mm - for metallographic investigations (microscope Neophot-2) and determination of microhardness (PMT-3); 2x20x0,3 mm - for mechanical

Effect of shot peening on the residual stress and mechanical behaviour of low-temperature and high-temperature annealed martensitic gear steel 18CrNiMo7-6

DEFF Research Database (Denmark)

Yang, R.; Zhang, X.; Mallipeddi, D.

2017-01-01

A martensitic gear steel (18CrNiMo7-6) was annealed at 180 degrees C for 2h and at similar to 750 degrees C for 1h to design two different starting microstructures for shot peening. One maintains the original as-transformed martensite while the other contains irregular-shaped sorbite together...... with ferrite. These two materials were shot peened using two different peening conditions. The softer sorbite + ferrite microstructure was shot peened using 0.6 mm conditioned cut steel shots at an average speed of 25 m/s in a conventional shot peening machine, while the harder tempered martensite steel...

Behavior of X 6 CrNi 18 11 under sequential testing of creep and fatigue

Energy Technology Data Exchange (ETDEWEB)

Husslage, W [TNO, Apeldoorn (Netherlands); Breitling, H [INTERATOM, Bergisch Gladbach (Germany)

1977-07-01

The behaviour of the austenitic stainless steel X 6 CrNi 18 11 with about 0.05% C, 18% Cr and 11% Ni was investigated under combined creep and cyclic loading at 550 degrees C. Base metal specimens and specimens containing a weld were tested by: prior cyclic loading followed by creep loading to rupture; prior creep loading followed by cyclic loading to rupture; alternating periods of creep and cyclic loading to rupture. The results were evaluated using the linear cumulative fatigue and creep damage rule. The damage factor D determined on basis of the respective behaviour of base material and welds varied between 0.5 and 1.6 if specimens containing a weld defect were not taken into consideration. Weld defects, which had predominantly an influence on fatigue, lowered the damage factor D up to 0.2. Evaluation of the results on welds with the pure creep and fatigue behaviour of base material shows damage factors between 0.4 and 0.9. By the high margins between allowable creep and fatigue life and life measured with specimens, the cumulative damages of base material and welded joints are much better than the allowable values according to CCI 1592 of the ASME Boiler and Pressure Vessel Code. (author)

Phase transformation and grain growth behavior of a nanocrystalline 18/8 stainless steel

Energy Technology Data Exchange (ETDEWEB)

Kotan, Hasan, E-mail: hasankotan@gmail.com [Konya Necmettin Erbakan University, Department of Metallurgical & Materials Engineering, Konya 42090 (Turkey); Darling, Kris A. [US Army Research Laboratory, Weapons and Materials Research Directorate, RDRL-WMM-F, Aberdeen Proving Ground, MD 21005-5069 (United States)

2017-02-16

Fe-18Cr-8Ni and Fe-18Cr-8Ni-1Y (at%) stainless steel powders were nanostructured by mechanical alloying from elemental powders and subjected to 90 min annealing treatments at various temperatures. The microstructural evolutions as a function of alloy compositions and temperatures were investigated by in-situ and ex-situ x-ray diffraction experiments, transmission electron microscopy and focused ion beam microscopy. The dependence of hardness on the microstructure was utilized to study the mechanical changes. It was found that the resulting microstructures by mechanical alloying were bcc solid solution, the so-called α’-martensite structure. The high temperature in-situ x-ray diffraction experiments showed that the martensite-to-austenite reverse phase transformation was completed above 800 and 900 °C for Fe-18Cr-8Ni and Fe-18Cr-8Ni-1Y steels, respectively. A partial or complete retransformation to martensite was observed upon cooling to room temperature. Annealing of nanocrystalline Fe-18Cr-8Ni steel yielded grain growth reaching to micron sizes at 1100 °C while addition of 1 at% yttrium stabilized the microstructure around 160 nm grain size and 6 GPa hardness after 90 min annealing at 1200 °C.

Long term properties and microstructural evolution of 18Cr-10Ni-3Cu-Ti-Nb austenitic stainless steel for boiler tube application

Energy Technology Data Exchange (ETDEWEB)

Minami, Y.; Fukui, T.; Ono, T. [TenarisNKK Tubes, Kawasaki, Kanagawa (Japan); Caminada, S. [TenarisDalmine, Dalmine, BG (Italy)

2010-07-01

The allowable tensile stress of 0.1C-18Cr-10Ni-3Cu-Ti-Nb steel (TEMPALOY AA-1; ASME C.C. 2512) is more than 30% higher compared with that of ASME SA-213 Grade TP347H in the temperature range 600-700 C. This high creep rupture strength is obtained by the precipitation of MC and M{sub 23}C{sub 6} carbides, and Cu-rich phase. Long term creep rupture tests over 10{sup 5}h enabled to verify the superior creep rupture strength of this steel. The investigation of microstructural evolution on the creep ruptured and aged specimens has shown the high structural stability of this material. Hardness and impact properties after high temperature aging reveal similar performance as conventional 18-8 stainless steels. Excellent steam oxidation resistance can be achieved by a shot-blasting method. The scale thickness of shot-blasted tube after 1000h at 750 C is below a few micron meters. These results have revealed that the mechanical properties and environmental resistance of this steel enable the use of TEMPALOY AA-1 in the latest generation of advanced USC boiler. (orig.)

Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

NARCIS (Netherlands)

Bojack, A.; Zhao, L.; Morris, P.F.; Sietsma, J.

2016-01-01

The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two

Development of oxide dispersion strengthened 9Cr ferritic-martensitic steel clad tube for fast reactor

International Nuclear Information System (INIS)

Laha, K.; Saroja, S.; Mathew, M.D.; Jayakumar, T.; Vijay, R.; Venugopal Reddy, A.; Lakshminarayana, B.; Kapoor, Komal; Jha, S.K.; Tonpe, S.S.

2012-01-01

One of the key issues in the economical operation of FBR is to achieve high burn-up of fuel (200-250 GWd/t) which considerably reduces the fuel cycle cost. This imposes stringent requirements of void swelling resistance upto 200 dpa for the core structural materials. Presently used alloy 09 (a modified austenitic stainless steel, 15Cr-15Ni-Ti) for PFBR has void swelling limit less than 150 dpa. Because of the inherent void swelling resistance, 9-12Cr steels ferritic/martensitic steels are qualified for irradiation upto 200 dpa but their low creep strength at temperatures above 600 deg C restricts their application as a clad material. Oxide dispersion strengthening is found to be promising means of extending the creep resistance of ferritic/martensitic steels beyond 650 deg C without sacrificing the inherent advantages of high thermal conductivity and low swelling of ferritic steels

Characteristics of Ni-Cr-Fe laser clad layers on EA4T steel

Science.gov (United States)

Chen, Wenjing; Chen, Hui; Wang, Yongjing; Li, Congchen; Wang, Xiaoli

2017-07-01

The Ni-Cr-Fe metal powder was deposited on EA4T steel by laser cladding technology. The microstructure and chemical composition of the cladding layer were analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The bonding ability between the cladding layer and the matrix was measured. The results showed that the bonding between the cladding layer and the EA4T steel was metallurgical bonding. The microstructure of cladding layer was composed of planar crystals, columnar crystals and dendrite, which consisted of Cr2Ni3, γ phase, M23C6 and Ni3B phases. When the powder feeding speed reached 4 g/min, the upper bainite occurred in the heat affected zone (HAZ). Moreover, the tensile strength of the joint increased, while the yield strength and the ductility decreased.

Tribological properties and surface structures of ion implanted 9Cr18Mo stainless steels

International Nuclear Information System (INIS)

Fengbin, Liu; Guohao, Fu; Yan, Cui; Qiguo, Sun; Min, Qu; Yi, Sun

2013-01-01

The polished quenched-and-tempered 9Cr18Mo steels were implanted with N ions and Ti ions respectively at a fluence of 2 × 10 17 ions/cm 2 . The mechanical properties of the samples were investigated by using nanoindenter and tribometer. The results showed that the ion implantations would improve the nanohardness and tribological property, especially N ion implantation. The surface analysis of the implanted samples was carried out by using XRD, XPS and AES. It indicated that the surface exhibits graded layers after ion implantation. For N ion implantation, the surface about 20 nm thickness is mainly composed of supersaturated interstitial N solid solution, oxynitrides, Cr x C y phase and metal nitrides. In the subsurface region, the metal nitrides dominate and the other phases disappear. For Ti ion implantation, the surface of about 20 nm thickness is mainly composed of titanium oxides and carbon amorphous phase, the interstitial solid solution of Ti in Fe is abundant in the subsurface region. The surface components and structures have significant contributions to the improved mechanical properties

Creep constitutive equation of dual phase 9Cr-ODS steel

International Nuclear Information System (INIS)

Sakasegawa, Hideo; Ukai, Shigeharu; Tamura, Manabu; Ohtsuka, Satoshi; Tanigawa, Hiroyasu; Ogiwara, Hiroyuki; Kohyama, Akira; Fujiwara, Masayuki

2008-01-01

9Cr-ODS (oxide dispersion strengthened) steels developed by JAEA (Japan Atomic Energy Agency) have superior creep properties compared with conventional heat resistant steels. The ODS steels can enormously contribute to practical applications of fast breeder reactors and more attractive fusion reactors. Key issues are developments of material processing procedures for mass production and creep life prediction methods in present R and D. In this study, formulation of creep constitutive equation was performed against the backdrop. The 9Cr-ODS steel displaying an excellent creep property is a dual phase steel. The ODS steel is strengthened by the δ ferrite which has a finer dispersion of oxide particles and shows a higher hardness than the α' martensite. The δ ferrite functions as a reinforcement in the dual phase 9Cr-ODS steel. Its creep behavior is very unique and cannot be interpreted by conventional theories of heat resistant steels. Alternative qualitative model of creep mechanism was formulated at the start of this study using the results of microstructural observations. Based on the alternative creep mechanism model, a novel creep constitutive equation was formulated using the exponential type creep equation extended by a law of mixture

TEM Studies of Boron-Modified 17Cr-7Ni Precipitation-Hardenable Stainless Steel via Rapid Solidification Route

Science.gov (United States)

Gupta, Ankur; Bhargava, A. K.; Tewari, R.; Tiwari, A. N.

2013-09-01

Commercial grade 17Cr-7Ni precipitation-hardenable stainless steel has been modified by adding boron in the range 0.45 to 1.8 wt pct and using the chill block melt-spinning technique of rapid solidification (RS). Application of RS has been found to increase the solid solubility of boron and hardness of 17Cr-7Ni precipitation-hardenable stainless steel. The hardness of the boron-modified rapidly solidified alloys has been found to increase up to ~280 pct after isochronal aging to peak hardness. A TEM study has been carried out to understand the aging behavior. The presence of M23(B,C)6 and M2(B,C) borocarbides and epsilon-carbide in the matrix of austenite and ferrite with a change in heat treatment temperature has been observed. A new equation for Creq is also developed which includes the boron factor on ferrite phase stability. The study also emphasizes that aluminum only takes part in ferrite phase stabilization and remains in the solution.

Behavior of helium gas atoms and bubbles in low activation 9Cr martensitic steels

Science.gov (United States)

Hasegawa, Akira; Shiraishi, Haruki; Matsui, Hideki; Abe, Katsunori

1994-09-01

The behavior of helium-gas release from helium-implanted 9Cr martensitic steels (500 appm implanted at 873 K) during tensile testing at 873 K was studied. Modified 9Cr-1Mo, low-activation 9Cr-2W and 9Cr-0.5V were investigated. Cold-worked AISI 316 austenitic stainless steel was also investigated as a reference which was susceptible helium embrittlement at high temperature. A helium release peak was observed at the moment of rupture in all the specimens. The total quantity of helium released from these 9Cr steels was in the same range but smaller than that of 316CW steel. Helium gas in the 9Cr steels should be considered to remain in the matrix at their lath-packets even if deformed at 873 K. This is the reason why the martensitic steels have high resistance to helium embrittlement.

Behavior of helium gas atoms and bubbles in low activation 9Cr martensitic steels

International Nuclear Information System (INIS)

Hasegawa, Akira; Shiraishi, Haruki; Matsui, Hideki; Abe, Katsunori

1994-01-01

The behavior of helium-gas release from helium-implanted 9Cr martensitic steels (500 appm implanted at 873 K) during tensile testing at 873 K was studied. Modified 9Cr-1Mo, low-activation 9Cr-2W and 9Cr-0.5V were investigated. Cold-worked AISI 316 austenitic stainless steel was also investigated as a reference which was susceptible helium embrittlement at high temperature. A helium release peak was observed at the moment of rupture in all the specimens. The total quantity of helium released from these 9Cr steels was in the same range but smaller than that of 316CW steel. Helium gas in the 9Cr steels should be considered to remain in the matrix at their lath-packets even if deformed at 873 K. This is the reason why the martensitic steels have high resistance to helium embrittlement. ((orig.))

Irradiation hardening of Mod.9Cr-1Mo steel

International Nuclear Information System (INIS)

Ryu, Woo-Seog; Kim, Sung-Ho; Choo, Kee-Nam; Kim, Do-Sik

2009-01-01

An irradiation test of Mod.9Cr-1Mo steel was carried out in the OR5 test hole of HANARO of a 30 MW thermal power at 390±10degC up to a fast neutron fluence of 4.4x10 19 (n/cm 2 ) (E > 1.0 MeV). The dpa of the irradiated specimens was evaluated to be 0.034 - 0.07. Tensile and impact tests of the irradiated Mod.9Cr-1Mo were done in the hot cell of the IMEF. The change of the tensile strength by irradiation was similar to the change of the yield strength. The increase of the yield and tensile strengths was up to 18% and 10% respectively. The elongation reduction of the weldment was up to 65%. (author)

Analysis of a multi pass weld of a thick walled tube made of austenitic stainless steel X6 CrNiNb 18 10

International Nuclear Information System (INIS)

Scholtes, B.; Zinn, W.; Ilg, U.; Backfisch, W.; Gibmeier, J.; Kirch, D.

2006-01-01

In this paper, microstructure and residual stresses of a multi pass welding of a thick-walled tube made of austenitic stainless steel X6 CrNiNb 18 10 (1.4550) are systematically characterized and assessed. Results of microstructural and phase analyses, residual stress and hardness measurements as well as of a tensile test using micro specimen and SEM analyses are presented. Using these data, plastic deformations occurring during the welding process in the vicinity of the weld seam are evaluated. Finally, consequences of an additional heat treatment at 400 C/24 h are studied. (Abstract Copyright [2006], Wiley Periodicals, Inc.) [de

The structure of the alphinizing coat on alloy steels

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S. Pietrowski

2008-12-01

Full Text Available In this paper results of the structure of the coat alphinizing in AlSi5 silumin on alloy steels: acid-proof 1H18N9T (X6CrNiTi18-10 and high speed SW18 (HS18-0-1 were presented. The temperature of the alphinizing bath was amounts to750±5°C, and immersion time of the element τ = 180s. It was shown, that there is the different “g” coat thickness on testing steels. On the 1H18N9T steel it amounts to g = 52μm, and on the SW18 steel – g = 203μm. Regardless of a grade of testing alloy steels the coat consist of three layers with diversified phasic structure. There is different chemical composition of coat layers on testing steels. The first layer from the base consist of AlFe phase containing alloy addictions of steels: Cr and Ni (1H18N9T and W, V and Cr (SW18. On this layer crystallize the second layer of intermetallic phases. It is the phase containing the main alloy addiction of steels: AlFeCr (1H18N9T and AlFeW (SW18. The last, outside layer consist of silumin containing AlFeNi intermetallic phases on the 1H18N9T steel and AlFeW on the SW18 steel. Regardless of the grade of testing steels there is Si element in all layers of the coat. There are morphological differences in tested layers. The second layer (AlFeW phase inside the coat on the SW18 steel consist of faced crystals growing into in outside silumin layer. On the 1H18N9T steel a boundary between transient and outside layer is more uniform. Free separations of intermetallic phases inside silumin layer on the 1H18N9T steel have lamellar and on the SW18 steel – faced form.

Feasibility study on decontamination of the contaminated stainless steel with HBF4 solution

International Nuclear Information System (INIS)

Dong Ruilin; Zhang Yuan; Qiu Dangui; Huang Yuying; Ren Xianwen

2002-01-01

Decontamination experiments were carried out with HBF 4 solution on the following four kinds of sample: 1Cr18Ni9Ti stainless steel with and without welding line, 1Cr18Ni9Ti stainless steel with oxide layer formed in boiling concentrated nitric acid solution, natural uranium and 230 Th contaminated stainless steel pipe sample from one decommissioning nuclear facility. The results indicated that the oxide layer, the welding line of the 1Cr18Ni9Ti stainless steel and itself can be dissolved in the HBF 4 decontamination solution. The solubility of the 1Cr18Ni9Ti stainless steel in the HBF 4 solution used in the test is more than 5 g/L, which means that the 0.13 m 2 stainless steel could be dissolved up to a thickness of 5 μm in one liter of decontamination solution. The decontamination efficiency is more than 85% in 30 minutes for the 230 Th contaminated sample, and 87% in 2 hours for the natural uranium contaminated sample. Both samples could be decontaminated to the background level after several runs of the decontamination

Development of banded microstructure in 34CrNiMo6 steel

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A. Nagode

2016-07-01

Full Text Available In this paper the development of a banded microstructure in hot-rolled 34CrNiMo6 steel which consisted of bainitic and martensitic bands is explained. The chemical compositions of the bands were measured with energy dispersive x-ray spectroscopy (EDS, which showed that the martensitic bands contained more alloying elements (Mn, Cr, Mo, Si than bainitic bands. By using Oberhoffer reagent, the segregations of phosphorus were also revealed. These phosphorus segregations coincided with the positive segregations of the alloying elements. The continuous cooling transformation (CCT diagrams of steel were calculated. They confirmed the formation of martensite in positive segregations and the formation of bainite in negative segregations.

Microstructure and Wear Resistance of TIG Remelted NiCrBSi Thick Coatings

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Guo-lu Li

2018-01-01

Full Text Available The self-fluxing NiCrBSi coatings with 800 μm thickness were prepared on the surface of AISI1045 steel substrate by plasma spraying. And the remelted coating was obtained using by the tungsten inert gas (TIG arc process. The microstructure, surface roughness, hardness, phase composition, and wear resistance of the sprayed coating and remelted coating were systematically investigated. The results demonstrate that TIG remelted treatment can significantly eliminate the microscopic defects in thick coating and improve its density. The surface roughness (Ra of the remelted coating is only 18.9% of the sprayed coating. The hardness of the remelted coating is 26.8% higher than that of the sprayed coating. The main phases in the sprayed coating are changed from γ-Ni, Cr7C3, and Cr2B to γ-Ni, Cr23C6, CrB, Ni3B, and Fe3C. The wear mass loss of the remelted coating is only 17.1% of the sprayed coating. Therefore, a Ni-based thick coating with good wear resistance can be obtained by plasma spraying and remelted technique.

Precipitation process of Z-phase in 9-12%CR steels

DEFF Research Database (Denmark)

Danielsen, Hilmar Kjartansson

2014-01-01

Precipitation of Z-phase, Cr(V,Nb)N, is known to negatively affect creep properties of 9-12%Cr steels for power plant applications as it dissolves finely distributed MX particles, (V,Nb)N, especially in high Cr steels. As the Z-phase precipitates slowly as large particles, this causes a net drop ...... and crystallographically into Z-phase CrTaN particles. Copyright © 2014 Electric Power Research Institute, Inc. Distributed by ASM International®. All rights reserved....

Microstructure characterization in the weld joint of a high nickel austenitic alloy and Cr18-Ni8 stainless steel

Energy Technology Data Exchange (ETDEWEB)

Wu, Na; Li, Yajiang; Wang, Juan [Shandong Univ., Jinan (CN). Key Lab. for Liquid - Solid Structural Evolution and Processing of Materials (Ministry of Education)

2012-06-15

High nickel austenitic alloy, 6 mm thick, and Cr18-Ni8 stainless steel with a thickness of 0.6 mm were joined by pulsed current tungsten inert gas arc welding without filler metal in this work. Metallographic examination, microhardness measurement and electron microprobe analysis were used to reveal microstructural characteristics in the joint. The results indicated that the weld metal consisted of {gamma}-austenite, {delta}-ferrite and carbides without the appearance of martensite. There were dendrite crystals at the edge of the weld metal near the high nickel austenitic alloy and isometric crystals in the center of the weld metal. The microhardness of the weld metal was the highest due to the existence of carbides and its finer structure. Graphite flakes were still embedded in the austenite matrix of the heat-affected zone without the formation of martensite. (orig.)

Structure of Fe-Ni-Cr steel welded joints

International Nuclear Information System (INIS)

Bratukhin, A.G.; Maslenkov, S.B.; Logunov, A.V.

1993-01-01

Properties of a welded joint depend on the structure of metal of the joint and near the joint areas subjected to thermal effect in the process of welding. The well-known phenomena, accompanying the welding (grain growth in near the joint area, intergrain slip, stressed state related to crystallization and rapid cooling), as well as certain other processes, which have been insufficiently studied either due to their poor pronouncement or owing to imperfection of the equipment and methods employed, were analyzed, as applied to stainless hihg-strength Fe-Ni-Cr steels

Estimation of the Temperature-Dependent Nitrogen Solubility in Stainless Fe-Cr-Mn-Ni-Si-C Steel Melts During Processing

Science.gov (United States)

Wendler, Marco; Hauser, Michael; Sandig, Eckhard Frank; Volkova, Olena

2018-04-01

The influence of chemical composition, temperature, and pressure on the nitrogen solubility of various high alloy stainless steel grades, namely Fe-14Cr-(0.17-7.77)Mn-6Ni-0.5Si-0.03C [wt pct], Fe-15Cr-3Mn-4Ni-0.5Si-0.1C [wt pct], and Fe-19Cr-3Mn-4Ni-0.5Si-0.15C [wt pct], was studied in the melt. The temperature-dependent N-solubility was determined using an empirical approach proposed by Wada and Pehlke. The thus calculated N-concentrations overestimate the actual N-solubility of all the studied Fe-Cr-Mn-Ni-Si-C steel melts at a given temperature and pressure. Consequently, the calculation model has to be modified by Si and C because both elements are not recognized in the original equation. The addition of the 1st and 2nd order interaction parameters for Si and C to the model by Wada and Pehlke allows a precise estimation of the temperature-dependent nitrogen solubility in the liquid steel bath, and fits very well with the measured nitrogen concentrations during processing of the steels. Moreover, the N-solubility enhancing effect of Cr- and Mn-additions has been demonstrated.

Microstructure of the Transitional Area of the Connection of a High-temperature Ni-based Brazing Alloy and Stainless Steel AISI 321 (X6CrNiTi 18–10

Directory of Open Access Journals (Sweden)

R. Augustin

2010-01-01

Full Text Available This paper presents a detailed examination of the structure of the transitional area between a brazing alloy and the parent material, the dimensions of the diffusion zones that are created, and the influence on them of a change in the brazing parameters. Connections between Ni-based brazing alloys (NI 102 with a small content of B and AISI 321 stainless steel (X6CrNiTi 18–10 were created in a vacuum (10−2 Pa at various brazing temperatures and for various holding times at the brazing temperature. Various specimens were tested. First, the brazing alloys were wetted and the dependence of the wetting on the brazing parameters was assessed. Then a chemical microanalysis was made of the interface between the brazing alloy and the parent material. The individual diffusion zones were identified on pictures from a light microscope and REM, and their dimensions, together with their dependence on the brazing parameters, were determined.

Interface bonding of NiCrAlY coating on laser modified H13 tool steel surface

Science.gov (United States)

Reza, M. S.; Aqida, S. N.; Ismail, I.

2016-06-01

Bonding strength of thermal spray coatings depends on the interfacial adhesion between bond coat and substrate material. In this paper, NiCrAlY (Ni-164/211 Ni22 %Cr10 %Al1.0 %Y) coatings were developed on laser modified H13 tool steel surface using atmospheric plasma spray (APS). Different laser peak power, P p, and duty cycle, DC, were investigated in order to improve the mechanical properties of H13 tool steel surface. The APS spraying parameters setting for coatings were set constant. The coating microstructure near the interface was analyzed using IM7000 inverted optical microscope. Interface bonding of NiCrAlY was investigated by interfacial indentation test (IIT) method using MMT-X7 Matsuzawa Hardness Tester Machine with Vickers indenter. Diffusion of atoms along NiCrAlY coating, laser modified and substrate layers was investigated by energy-dispersive X-ray spectroscopy (EDXS) using Hitachi Tabletop Microscope TM3030 Plus. Based on IIT method results, average interfacial toughness, K avg, for reference sample was 2.15 MPa m1/2 compared to sample L1 range of K avg from 6.02 to 6.96 MPa m1/2 and sample L2 range of K avg from 2.47 to 3.46 MPa m1/2. Hence, according to K avg, sample L1 has the highest interface bonding and is being laser modified at lower laser peak power, P p, and higher duty cycle, DC, prior to coating. The EDXS analysis indicated the presence of Fe in the NiCrAlY coating layer and increased Ni and Cr composition in the laser modified layer. Atomic diffusion occurred in both coating and laser modified layers involved in Fe, Ni and Cr elements. These findings introduce enhancement of coating system by substrate surface modification to allow atomic diffusion.

Efectos gammágenos del cobre en los aceros inoxidables 18Cr8Ni

Directory of Open Access Journals (Sweden)

Botella, J.

1997-10-01

Full Text Available From a series of 22 typical 18Cr8Ni stainless steel 40 kg ingots, with copper variable concentrations from 0.6 to 3.0 weight %, δ-ferrite is measured with a ferrite-meter device, calculating a nickel equivalent of 0.27 for copper. Some differences between the 8-ferrite and that on calculated by DeLong -excluding the copper γ-gene action- have been found because of different solidification and cooling regimes in ingot and weld cases.

A partir de una serie de 22 lingotes de 40 kg de aceros inoxidables típicos 18Cr8Ni, con concentraciones variables de cobre entre 0,6 y 3,0 % en masa, se mide la ferrita δ mediante un medidor de ferrita y se deduce para el cobre un equivalente en níquel de 0,27, a la vez que se establecen ciertas diferencias entre los contenidos de ferrita δ medida y la deducida según DeLong -excluida la acción gammágena del cobre- por el hecho de solidificar en lingotes en vez de la típica solidificación de soldaduras.

The integrity of 9Cr-1Mo to stainless steel transition joints in AGR steam generators

International Nuclear Information System (INIS)

James, D.W.; Neumann, P.; Soo, J.

1982-01-01

The metallurgical aspects of the transition joint between 9Cr-1Mo and 316 stainless steel boiler tube sections are reviewed. A large minimum superheat margin (106 0 C) between the dryout zone and the 9Cr-1Mo to stainless steel transition joint was specified in the original design to eliminate the risk of wetting the stainless steel which is susceptible to stress corrosion cracking. However, small defects were discovered in the welds between the 9Cr-1Mo and Sanicro (72%Ni-16%Cr-10%Fe) transition piece, resulting from dilution of the weld pool by nickel from the transition piece. This led to the possibility of weld failure as a result of creep crack growth in service, and any significant reduction in operating temperature would mean that the large superheat margin could not be sustained. The creep properties of the joints, together with the transition joint temperature distribution, enabled tube failure rates to be determined as a function of operating temperature. A probabilistic model was developed so that the transition joint could be operated within a temperature 'window', the lower temperature limit being determined by stress corrosion considerations and the upper limit being set by creep rate limitations. This allows full load performance from the boilers throughout the anticipated life of the plant. (author)

Kinetics of phase transformations of undercooled austenite in 18CrNiMo7-6 steel applied for toothed wheels

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J. Krawczyk

2010-07-01

Full Text Available Toothed wheels constitute essential part of the steel structural elements market. The most often hypereutectoid structural steels forcarburizing are used for toothed wheels. The final producers of toothed wheels are not demanding regarding a microstructure, providedthat the determined requirements will be fulfilled (e.g. metallurgical purity determined by ultrasounds. Therefore delivered forgings can be in an annealed or quenched state. This results from the situation that the final heat treatment or heat-chemical one is being done at one of the last stages of the toothed wheel production. An essential factor allowing to develop the proper heat treatment is the knowledge of the kinetics of phase transformations of undercooled austenite and its relating to technological conditions, being at the producer disposal, as well as to forging dimensions. Such investigations should be carried out on real melts used for forgings for toothed wheels production together with an analysis of microstructure changes on the forging cross-section. They should be based on calculation methods determining the distribution of cooling rates on its cross-section in dependence of an applied cooling medium.The mentioned above problems in relation to 18CrNiMo7-6 steel - are elucidated in this paper. The aim of the investigations wasthe description of the kinetics of phase transformations of undercooled austenite in this steel. The CCT diagram was constructed for the austenitizing temperature determined on the basis of phase transformations temperatures (the so-called critical points.

Effect of Alloy 625 Buffer Layer on Hardfacing of Modified 9Cr-1Mo Steel Using Nickel Base Hardfacing Alloy

Science.gov (United States)

Chakraborty, Gopa; Das, C. R.; Albert, S. K.; Bhaduri, A. K.; Murugesan, S.; Dasgupta, Arup

2016-04-01

Dashpot piston, made up of modified 9Cr-1Mo steel, is a part of diverse safety rod used for safe shutdown of a nuclear reactor. This component was hardfaced using nickel base AWS ER NiCr-B alloy and extensive cracking was experienced during direct deposition of this alloy on dashpot piston. Cracking reduced considerably and the component was successfully hardfaced by application of Inconel 625 as buffer layer prior to hardface deposition. Hence, a separate study was undertaken to investigate the role of buffer layer in reducing the cracking and on the microstructure of the hardfaced deposit. Results indicate that in the direct deposition of hardfacing alloy on modified 9Cr-1Mo steel, both heat-affected zone (HAZ) formed and the deposit layer are hard making the thickness of the hard layer formed equal to combined thickness of both HAZ and deposit. This hard layer is unable to absorb thermal stresses resulting in the cracking of the deposit. By providing a buffer layer of Alloy 625 followed by a post-weld heat treatment, HAZ formed in the modified 9Cr-1Mo steel is effectively tempered, and HAZ formed during the subsequent deposition of the hardfacing alloy over the Alloy 625 buffer layer is almost completely confined to Alloy 625, which does not harden. This reduces the cracking susceptibility of the deposit. Further, unlike in the case of direct deposition on modified 9Cr-1Mo steel, dilution of the deposit by Ni-base buffer layer does not alter the hardness of the deposit and desired hardness on the deposit surface could be achieved even with lower thickness of the deposit. This gives an option for reducing the recommended thickness of the deposit, which can also reduce the risk of cracking.

Evaluation of austenitic stainless steels for transpassive corrosion by metal purification technology. Synergistic effect of Si and P on intergranular corrosion of Fe-18Cr-14Ni alloys

International Nuclear Information System (INIS)

Mayuzumi, Masami; Ohta, Joji; Kako, Kenji; Kawakami, Eishi

2001-01-01

The synergistic effect of Si, Mn, C, P, and S on the transpassive corrosion of HP18Cr-14Ni alloys was studied in 13N nitric acid. The specimens were fabricated using a cold crucible method in a high-vacuum chamber to reduce contamination. The additions of Si<1% and Mn<2% had no effect on the corrosion behavior of HP18Cr-14Ni alloys, and the addition of Si<1% also had no effect on the corrosion behavior of HP18Cr-14Ni-1Mn alloys, although 1% Si induced intergranular corrosion in both the alloys. Thus, HP18Cr-14Ni-1Mn-0.5Si alloys were selected to evaluate the effects of C, P and S (100 ppm each). The addition of P, and the co-addition of C, P, and S to HP18Cr-14Ni-1Mn-0.5Si induced intergranular corrosion of the same degree in the solution annealed condition. This result suggests the synergistic effect of Si and P to induce intergranular corrosion, since the single addition of Si or P to this level did not lead to intergranular corrosion of HP18Cr-14Ni alloys. HP18Cr-14Ni-1Mn-0.5Si alloys containing C, P, and S at the 100 ppm level each showed superior corrosion resistance compared to a commercial Type 304L in 13N nitric acid. (author)

Microstructure and wear behaviors of laser clad NiCr/Cr3C2-WS2 high temperature self-lubricating wear-resistant composite coating

Science.gov (United States)

Yang, Mao-Sheng; Liu, Xiu-Bo; Fan, Ji-Wei; He, Xiang-Ming; Shi, Shi-Hong; Fu, Ge-Yan; Wang, Ming-Di; Chen, Shu-Fa

2012-02-01

The high temperature self-lubricating wear-resistant NiCr/Cr3C2-30%WS2 coating and wear-resistant NiCr/Cr3C2 coating were fabricated on 0Cr18Ni9 austenitic stainless steel by laser cladding. Phase constitutions and microstructures were investigated, and the tribological properties were evaluated using a ball-on-disc wear tester under dry sliding condition at room-temperature (17 °C), 300 °C and 600 °C, respectively. Results indicated that the laser clad NiCr/Cr3C2 coating consisted of Cr7C3 primary phase and γ-(Fe,Ni)/Cr7C3 eutectic colony, while the coating added with WS2 was mainly composed of Cr7C3 and (Cr,W)C carbides, with the lubricating WS2 and CrS sulfides as the minor phases. The wear tests showed that the friction coefficients of two coatings both decrease with the increasing temperature, while the both wear rates increase. The friction coefficient of laser clad NiCr/Cr3C2-30%WS2 is lower than the coating without WS2 whatever at room-temperature, 300 °C, 600 °C, but its wear rate is only lower at 300 °C. It is considered that the laser clad NiCr/Cr3C2-30%WS2 composite coating has good combination of anti-wear and friction-reducing capabilities at room-temperature up to 300 °C.

High-temperature brazing of X5CrNi18 10 and NiCr20TiAl using the atmospherically plasma-sprayed L-Ni2 filler metal

International Nuclear Information System (INIS)

Wielage, B.; Drozak, J.

1992-01-01

The hybrid-technological combination of the atmospheric plasma spraying for the application of a high-temperature filler metal followed by a brazing process was analyzed in terms of structure and mechanical properties of X5CrNi18 10 and NiCr20TiAl brazing joints. The thickness of the filler metal layer was minimized at [de

Effect of carbon content on microstructure and mechanical properties of hot-rolled low carbon 12Cr-Ni stainless steel

International Nuclear Information System (INIS)

Zheng, H.; Ye, X.N.; Li, J.D.; Jiang, L.Z.; Liu, Z.Y.; Wang, G.D.; Wang, B.S.

2010-01-01

Research highlights: → Hot-rolled ultra low carbon martensite is characterized by dislocation cells substructure. → The formation of dislocation cells is attributed to high Ms and low interstitial atoms content. → Hot-rolled ultra low carbon 12Cr-Ni stainless steel has excellent impact toughness. → Delta ferrite deteriorates the impact toughness of hot-rolled 12Cr-Ni stainless steel. - Abstract: 12Cr-Ni stainless steels containing different carbon contents from 0.004 wt.% to 0.034 wt.% were hot-rolled and air-cooled. Their corresponding microstructures were observed with optical microscope and transmission electron microscope, and the Vickers hardness, tensile and impact tests were also carried out. It was found that the martensitic morphology was significantly influenced by carbon content. The as-received ultra low carbon martensite in the steel containing 0.004 wt.% C is characterized by dislocation cells substructure. The formation of dislocation cells is attributed to high martensite finishing point (above 400 deg. C) and low interstitial atoms content. On the other hand, the martensite in the steel containing 0.034 wt.% C consists mainly of typical martensite laths because of low martensite finishing point and high interstitial atoms content which hinder dislocation motion. Furthermore, carbon content has an evident effect on the mechanical properties of 12Cr-Ni steels. The hardness and strength of the as-received steels increase with an increase in carbon content, but their elongation and impact toughness decrease with the carbon content. The steel containing 0.004 wt.% C has excellent impact toughness due to the ultra low carbon content in the martensite composed of dislocation cells.

Changes of structure and properties of cast steels GX10NiCrNb32-20 and GX10NiCrNb3-25 after long-term tempering at 600-1000 C

International Nuclear Information System (INIS)

Gommans, R.; Schrijen, H.; Sundermann, J.; Steinkusch, W.; Hering, W.

2001-01-01

Low-alloy cast steels of type GX 10NiCrNb 32.20 are commonly used for the outlet section of reformer and cracker tubes for the temperature range of 600-1000 C. There was a lack of data on the ductility of the 25%Cr alloyed cast steel GX10NiCrNb 35.25 at room temperature after tempering, which was investigated in a joint project of Pose-Marre and DSM. Mechanical tests were carried out at room temperature and at elevated temperatures. Apart from light microscopy, also SEM/EDX, SAM and TEM analyses were carried out. The 25% alloy has lower ductility than the 20% alloy, owing primarily to the more pronounced development of M 6 C carbide from primary NbC carbide, which takes up Ni and Si during tempering. The microstructure and composition of the M 6 C carbide wre not fully clarified. Information is presented on the potential application of low-carbon materials of the type GX10NiCrNb35.25 [de

Observations on thermally cycled 20% Cr/25% Ni/Nb stabilised stainless steel

International Nuclear Information System (INIS)

Lobb, R.C.

1984-06-01

A variety of optical and electron techniques, such as optical metallography, scanning electron microscopy and electron probe microanalysis, have been used to study the morphology and composition of oxides formed on 20 Cr/25 Ni/Nb stainless steel during oxidation at 850 0 C and subsequent thermal cycling in simulated reactor gas. (author)

Conversion of MX Nitrides to Modified Z-Phase in 9-12%Cr Ferritic Steels

DEFF Research Database (Denmark)

Cipolla, Leonardo

for Z-phase formation was highlighted during the studies. Several 9-12%Cr commercial steels with prolonged high-temperature exposures have been investigated, too. The same mechanism of Z-phase formation observed in 12%Cr model alloys was identified in industrial 9-12%Cr steels after thousands of hours......The 9-12%Cr ferritic steels are extensively used in modern steam power plants at service temperature up to 620°C. Currently the best perform ing ferritic creep resistance steel is the ASTM Grade 92, whose high temperature strength has recently been assessed by European Creep Collaborative Committee...... in 2005 as 600°C/113MPa/10 5h. All previous attempts made in the last twenty years to develop ferritic steels for 650°C applications have failed due to the incapacity to combine the superior oxidation resistance, given by 12%Cr content, with excellent creep resistance of high-alloyed ferritic steels...

Void formation and helium effects in 9Cr-1MoVNb and 12Cr-1MoVW steels irradiated in HFIR and FFTF at 400/degree/C

International Nuclear Information System (INIS)

Maziasz, P.J.; Klueh, R.L.

1988-01-01

Martensitic/ferritic 9Cr-1MoVNb and 12Cr-1MoVW steels doped with up to 2 wt% Ni have up to 450 appm He after HFIR irradiation to /approximately/38 dpa, but only 5 appm He after 47 dpa in FFTF. No fine He bubbles and few or no larger voids were observable in any of these steels after FFTF irradiation at 407/degree/C. By contrast, many voids were found in the undoped steels (30-90 appm He) irradiated in HFIR at 400/degree/C, while voids plus many more fine He bubbles were found in the Ni-doped steels (400-450 appm He). Irradiation in both reactors at /approximately/400/degree/C produced significant changes in the as-tempered lath/subgrain boundary, dislocation, and precipitation structures that were sensitive to alloy composition, including doping with Ni. However, for each specific alloy the irradiation-produced changes were exactly the same comparing samples irradiated in FFTF and HFIR, particularly the Ni-doped steels. Therefore, the increased void formation appears solely due to the increased helium generation found in HFIR. While the levels of void swelling are relatively low after 37-39 dpa in HFIR (0.1-0.4%), details of the microstructural evolution suggest that void nucleation is still progressing, and swelling could increase with dose. The effect of helium on void swelling remains a valid concern for fusion application that requires higher dose experiments. 15 refs., 14 figs., 8 tabs

Effects of Bond Coating on NiCrBSi-Mo Composite Functional Coating Properties in Plasma Spraying NiCrBSi-Mo/Ni Coating

OpenAIRE

DU Ji-yu; LI Fang-yi; LU Hai-yang; SHANG Jian-tong; LI Zhen

2017-01-01

Nickel-based bond coating and composite functional coating were sprayed on leaf blade steel material FV520B successively by using air plasma spraying system. NiCrBSi-Mo powder deposition rate, coating porosity, bonding strength and surface hardness were tested. The results indicate that, for the NiCrBSi-Mo/Ni coating, bond coating with 180-220μm thickness can improve NiCrBSi-Mo powder deposition rate while the surface coating with lower porosity, higher bonding strength and high hardness is p...

Fundamental modelling of particle strengthened 9-12% Cr steels

Energy Technology Data Exchange (ETDEWEB)

Magnusson, Hans; Sandstroem, Rolf [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Materials Science and Engineering; Royal Inst. of Tech., Stockholm (Sweden). Brinell Centre

2010-07-01

Creep strength of particle strengthened 9-12% Cr steels can be predicted by fundamental modelling. The creep strength is evaluated from the state of the microstructure during creep. Particle hardening at high temperatures can be predicted by taking dislocation climb across particles into account. Work hardening is calculated from immobile dislocations in subgrain interiors and at boundaries using the composite theory. Subgrain coarsening will lower the influence of the mechanically hard boundaries. Recovery in dislocation density is predicted through static recovery by climb and dynamic recovery by locking and dipole formation. Solid solution hardening is needed in order to explain the difference in creep strength between different 9-12% Cr steels. The accumulation of large atoms such as Mo and W will slow down the dislocation climb velocity, and thereby the microstructure recovery rate. 100000h rupture strength is predicted for X20, P91, P92 steels without any use of fitting parameters. The creep strength of P91 steel with different microstructure due to Al additions. Z-phase transformation and heat affected material is presented. (orig.)

Fabrication and characterization of reference 9Cr and 12Cr-ODS low activation ferritic/martensitic steels

Energy Technology Data Exchange (ETDEWEB)

Muroga, T., E-mail: muroga@nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Nagasaka, T. [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Li, Y.; Abe, H. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Ukai, S. [Graduate School of Engineering, Hokkaido University, N13, W8, Kita-ku, Sapporo 060-8628 (Japan); Kimura, A. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Okuda, T. [Kobelco Research Institute, 1-5-5 Takatsukadai, Nishi-ku, Kobe, Hyogo 651-2271 (Japan)

2014-10-15

For the purpose of arranging reference alloys available for various characterization efforts by Japanese fusion research groups, fabrication of reference 9Cr and 12Cr-ODS steels have been carried out with similar manufacturing processes followed by various characterizations. The fabrication proceeded with powder mixing, MA, encapsulation into mild steel cases, hot extrusion and hot forging, followed by final heat treatments. Each alloy was extruded into three bars. The characterization included chemical composition analysis, SEM and TEM microstructural observations, hardness tests, tensile tests at RT and 973 K, and relatively short-term thermal creep tests at 973 K. Room temperature hardness for 9Cr-ODS was larger than 12Cr-ODS, the former showing large increase when annealing temperature exceeded 1200 K and the latter showing no significant change with annealing temperature. Tensile strength of 9Cr-ODS was significantly larger than that of 12Cr-ODS at RT but comparable at 973 K. 9Cr-ODS showed longer and shorter creep rupture time than 12Cr-ODS at high and low stress levels, respectively. The mechanism of the difference in creep properties of the two alloys was discussed.

Study of mechanical properties and high temperature oxidation behavior of a novel cold-spray Ni-20Cr coating on boiler steels

Energy Technology Data Exchange (ETDEWEB)

Kaur, Narinder [Semiconductor Materials and Device Laboratory, Department of Semiconductor Science, Dongguk University-Seoul, Seoul 100715 (Korea, Republic of); Kumar, Manoj [School of Mechanical, Materials & Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab (India); Sharma, Sanjeev K.; Kim, Deuk Young [Semiconductor Materials and Device Laboratory, Department of Semiconductor Science, Dongguk University-Seoul, Seoul 100715 (Korea, Republic of); Kumar, S.; Chavan, N.M.; Joshi, S.V. [International Advanced Research Centre for Powder Metallurgy & New Materials (ARCI), Hyderabad 500005 (India); Singh, Narinder [Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar, Punjab (India); Singh, Harpreet, E-mail: harpreetsingh@iitrpr.ac.in [School of Mechanical, Materials & Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab (India)

2015-02-15

Highlights: • A presynthesized Ni-20Cr nanocrystalline powder was successfully deposited on T22 and SA 516 boilers steels using cold spray process. • The coatings are observed to have more than 2-folds microhardness in comparison with the base steels. • The coating was successful in reducing the weight gain of T22 and SA 516 steel by 71% and 94%. - Abstract: In the current investigation, high temperature oxidation behavior of a novel cold-spray Ni-20Cr nanostructured coating was studied. The nanocrystalline Ni-20Cr powder was synthesized by the investigators using ball milling, which was deposited on T22 and SA 516 steels by cold spraying. The crystallite size based upon Scherrer's formula for the developed coatings was found to be in nano-range for both the substrates. The accelerated oxidation testing was performed in a laboratory tube furnace at a temperature 900 °C under thermal cyclic conditions. Each cycle comprised heating for one hour at 900 °C followed by cooling for 20 min in ambient air. The kinetics of oxidation was established using weight change measurements for the bare and the coated steels. The oxidation products were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and X-ray mapping techniques. It was found from the results that the coating was successful in reducing the weight gain of SA213-T22 and SA 516-Grade 70 steel by 71% and 94%, respectively. This may be attributed to relatively denser structure, lower porosity and lower oxide content of the coating. Moreover, the developed nano-structured Ni-20Cr powder coating was found to perform better than its counterpart micron-sized Ni-20Cr powder coating, in terms of offering higher oxidation resistance and hardness.

Microstructure refinement and strengthening mechanisms of a 9Cr oxide dispersion strengthened steel by zirconium addition

International Nuclear Information System (INIS)

Xu, Hai Jian; Lu, Zheng; Wang, Dong Mei; Liu, Chunming

2017-01-01

To study the effects of zirconium (Zr) addition on the microstructure, hardness and the tensile properties of oxide dispersion strengthened (ODS) ferritic-martensitic steels, two kinds of 9Cr-ODS ferritic-martensitic steels with nominal compositions (wt.%) of Fe-9Cr-2W-0.3Y_2O-3 and Fe-9Cr-2W-0.3Zr-0.3Y_2O_3 were fabricated by the mechanical alloying (MA) of premixed powders and then consolidated by hot isostatic pressing (HIP) techniques. The experimental results showed that the average grain size decreases with Zr addition. The trigonal δ-phase Y_4Zr_3O_1_2 oxides and body-centered cubic Y_2O_3 oxides are formed in the 9Cr-Zr-ODS steel and 9Cr non-Zr ODS steel, respectively, and the average size of Y_4Zr_3O_1_2 particles is much smaller than that of Y_2O_3. The dispersion morphology of the oxide particles in 9Cr-Zr-ODS steel is significantly improved and the number density is 1.1 x 10"2"3/m"3 with Zr addition. The 9Cr-Zr-ODS steel shows much higher tensile ductility, ultimate tensile strength and Vickers hardness at the same time

Creep-fatigue-environment interaction of 9Cr-1Mo-V-Nb steel

International Nuclear Information System (INIS)

Shibata, Hiroyuki; Ishikawa, Akiyoshi; Asada, Yasuhide

1996-01-01

An extension of the creep-fatigue damage model has been conducted in the present study. The original damage model has been developed to the predict the creep-fatigue life of 9Cr-1Mo-V-Nb steel (Modified 9Cr-1Mo steel) in a very high vacuum environment. The present study is to extend an applicability of the model to the creep-fatigue damage accumulation in the air environment. (orig.)

Impact Strength of Austenitic and Ferritic-Austenitic Cr-Ni Stainless Cast Steel in -40 and +20°C Temperature

Directory of Open Access Journals (Sweden)

Kalandyk B.

2014-10-01

Full Text Available Studies described in this paper relate to common grades of cast corrosion resistant Cr-Ni steel with different matrix. The test materials were subjected to heat treatment, which consisted in the solution annealing at 1060°C followed by cooling in water. The conducted investigations, besides the microstructural characteristics of selected cast steel grades, included the evaluation of hardness, toughness (at a temperature of -40 and +20oC and type of fracture obtained after breaking the specimens on a Charpy impact testing machine. Based on the results of the measured volume fraction of ferrite, it has been found that the content of this phase in cast austenitic steel is 1.9%, while in the two-phase ferritic-austenitic grades it ranges from 50 to 58%. It has been demonstrated that within the scope of conducted studies, the cast steel of an austenitic structure is characterised by higher impact strength than the two-phase ferritic-austenitic (F-A grade. The changing appearance of the fractures of the specimens reflected the impact strength values obtained in the tested materials. Fractures of the cast austenitic Cr-Ni steel obtained in these studies were of a ductile character, while fractures of the cast ferritic-austenitic grade were mostly of a mixed character with the predominance of brittle phase and well visible cleavage planes.

Transformation and Precipitation Kinetics in 30Cr10Ni Duplex Stainless Steel

Science.gov (United States)

Fazarinc, Matevz; Terčelj, Milan; Bombač, David; Kugler, Goran

2010-09-01

To improve the microstructure during casting, hot forming, and heat treatment of 30Cr10Ni duplex stainless steel, accurate data on the precipitation and transformation processes at high temperatures are needed. In this article, the precipitation and transformation processes at various aging times in the temperature range 873 K to 1573 K (600 °C to 1300 °C) were studied. The 30Cr10Ni ferrous alloy contains a relatively large amount of Cr, Ni, and C, which results in a complex microstructure. In addition to the ferrite, austenite, and sigma phase, the M23C6 and MC carbides were also observed in the microstructure. The precipitation of the sigma phase was observed after just 3 minutes of aging, and after 30 minutes of aging at approximately 1053 K (780 °C), its fraction exceeded 40 pct. An intensive austenite-to-ferrite transformation was observed above 1423 K (1150 °C). Optical microscopy, energy-dispersive X-ray spectroscopy (EDS), electron backscattered diffraction (EBSD), and X-ray diffraction (XRD), as well as micro-indentation hardness, hardness, impact toughness, and tensile tests, were carried out to evaluate the obtained microstructures of aged samples.

Tribological properties and surface structures of ion implanted 9Cr18Mo stainless steels

Science.gov (United States)

Fengbin, Liu; Guohao, Fu; Yan, Cui; Qiguo, Sun; Min, Qu; Yi, Sun

2013-07-01

The polished quenched-and-tempered 9Cr18Mo steels were implanted with N ions and Ti ions respectively at a fluence of 2 × 1017 ions/cm2. The mechanical properties of the samples were investigated by using nanoindenter and tribometer. The results showed that the ion implantations would improve the nanohardness and tribological property, especially N ion implantation. The surface analysis of the implanted samples was carried out by using XRD, XPS and AES. It indicated that the surface exhibits graded layers after ion implantation. For N ion implantation, the surface about 20 nm thickness is mainly composed of supersaturated interstitial N solid solution, oxynitrides, CrxCy phase and metal nitrides. In the subsurface region, the metal nitrides dominate and the other phases disappear. For Ti ion implantation, the surface of about 20 nm thickness is mainly composed of titanium oxides and carbon amorphous phase, the interstitial solid solution of Ti in Fe is abundant in the subsurface region. The surface components and structures have significant contributions to the improved mechanical properties.

Microstructure of Vacuum-Brazed Joints of Super-Ni/NiCr Laminated Composite Using Nickel-Based Amorphous Filler Metal

Science.gov (United States)

Ma, Qunshuang; Li, Yajiang; Wu, Na; Wang, Juan

2013-06-01

Vacuum brazing of super-Ni/NiCr laminated composite and Cr18-Ni8 stainless steel was carried out using Ni-Cr-Si-B amorphous filler metal at 1060, 1080, and 1100 °C, respectively. Microstructure and phase constitution were investigated by means of optical and scanning electron microscopy, energy-dispersive spectroscopy, x-ray diffraction, and micro-hardness tester. When brazed at 1060-1080 °C, the brazed region can be divided into two distinct zones: isothermally solidified zone (ISZ) consisting of γ-Ni solid solution and athermally solidified zone (ASZ) consisting of Cr-rich borides. Micro-hardness of the Cr-rich borides formed in the ASZ was as high as 809 HV50 g. ASZ decreased with increase of the brazing temperature. Isothermal solidification occurred sufficiently at 1100 °C and an excellent joint composed of γ-Ni solid solution formed. The segregation of boron from ISZ to residual liquid phase is the reason of Cr-rich borides formed in ASZ. The formation of secondary precipitates in diffusion-affected zone is mainly controlled by diffusion of B.

The Structure of the Silumin Coat on Alloy Cast Steels

Directory of Open Access Journals (Sweden)

T. Szymczak

2012-04-01

Full Text Available The work presents the analysis results of the structure of the coat obtained by dipping in silumin AlSi5 of two grades of alloy cast steel: GX6CrNiTi18-10 (LH18N9T and GX39Cr13 (LH14. The temperature of the silumin bath was 750±5°C, and the hold-up time of the cast steel element τ = 180 s. The absolute thickness of the coat obtained in the given conditions was g = 104 μm on cast steel GX6CrNiTi18-10 and g = 132 μm on GX39Cr13. The obtained coat consisted of three layers of different phase structure. The first layer from the base “g1`” was constructed of the phase AlFe including Si and alloy additives of the tested cast steel grades: Cr and Ni (GX6CrNiTi18-10 and Cr (GX39Cr13. The second layer “g1``” of intermetallic phases AlFe which also contains Si and Cr crystallizes on it. The last, external layer “g2” of the coat consists of the silumin containing the intermetallic phases AlFeSi which additionally can contain alloy additives of the cast steel. It was shown that there were no carbides on the coat of the tested cast steels which are the component of their microstructure, as it took place in the case of the coat on the high speed steels.

Welded joint properties of steel 2.25Cr1MoNiNb

International Nuclear Information System (INIS)

Gladis, R.; Ivanek, J.; Gottwald, M.

1981-01-01

Welded joints of steel 08Cr2.25Mo1NiNb for fast reactor steam generators made using manual arc welding with electrodes of identical compositions attain short-term mechanical properties and times to fracture when creep tested that match those of the base material. The reduction of the carbidic phase content in the steel and the welded joint metal did not adversely affect the tensile properties of the welded joint while increasing notch toughness of the heat-affected zone. Reduced carbon and niobium contents in the steel and the welded joint resulted in significant reduction in the proportion of carbidic eutectic particles in both the heat-affected zone and the weld metal. (Ha)

Precipitation sequences in austenitic Fe-22Cr-21Ni-6Mo-(N) stainless steels

International Nuclear Information System (INIS)

Kim, S.-J.; Lee, T.-H.

1999-01-01

Precipitation sequence of nitrogen containing Fe-22Cr-21Ni-6Mo-N austenitic stainless steel has been investigated after aging at high temperatures, and compared with nitrogen free steel. The σ phases and M 23 C 6 carbides were observed along the grain boundaries as well as in the matrix in both of the solution treated specimens. The M 6 C carbides and chi phase appeared successively in between 3 hours and 24 hours depending on the nitrogen content. Main difference in aging behavior was the precipitation of fine nitrides. Aging for 24 hours and 168 hours of nitrogen containing steel resulted in the formation of fine Cr 2 N and faceted AlN nitrides. The crystallography, structure and morphology were analyzed with analytical electron microscopy. (orig.)

Microstructure refinement and strengthening mechanisms of a 9Cr oxide dispersion strengthened steel by zirconium addition

Energy Technology Data Exchange (ETDEWEB)

Xu, Hai Jian; Lu, Zheng; Wang, Dong Mei; Liu, Chunming [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang (China)

2017-02-15

To study the effects of zirconium (Zr) addition on the microstructure, hardness and the tensile properties of oxide dispersion strengthened (ODS) ferritic-martensitic steels, two kinds of 9Cr-ODS ferritic-martensitic steels with nominal compositions (wt.%) of Fe-9Cr-2W-0.3Y{sub 2}O-3 and Fe-9Cr-2W-0.3Zr-0.3Y{sub 2}O{sub 3} were fabricated by the mechanical alloying (MA) of premixed powders and then consolidated by hot isostatic pressing (HIP) techniques. The experimental results showed that the average grain size decreases with Zr addition. The trigonal δ-phase Y{sub 4}Zr{sub 3}O{sub 12} oxides and body-centered cubic Y{sub 2}O{sub 3} oxides are formed in the 9Cr-Zr-ODS steel and 9Cr non-Zr ODS steel, respectively, and the average size of Y{sub 4}Zr{sub 3}O{sub 12} particles is much smaller than that of Y{sub 2}O{sub 3}. The dispersion morphology of the oxide particles in 9Cr-Zr-ODS steel is significantly improved and the number density is 1.1 x 10{sup 23}/m{sup 3} with Zr addition. The 9Cr-Zr-ODS steel shows much higher tensile ductility, ultimate tensile strength and Vickers hardness at the same time.

Characterization of corrosion resistant on NiCoCr coating layer exposed to 5%NaCl

Science.gov (United States)

Sugiarti, E.; Sundawa, R.; Desiati, R. D.; Zaini, K. A.

2018-03-01

Highly corrosion resistant of carbon steel coated NiCoCr was applied in corrosive of marine environtment. Carbon steel coated NiCoCr was prepared by a two step technique of NiCo electro-deposition and Cr pack cementation. The samples were exposed to 5 wt.% NaCl for 48 and 168 hours. The microstructure and corrosion product were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The corrosion resistance of carbon steel coated NiCoCr was found to be better than that of carbon steel substrate without coating. The results showed the microstructure of 48 h corroded sample has duplex layer composed of inner α-(Ni,Co), α-Cr and outer Cr2O3, while a quite thin and continues protective oxide of Cr2O3 was observed in outer layer of 168 h corroded sample. The formation of oxide scale rich in Cr2O3 has contributed for the better corrosion resistance of carbon steel coated NiCoCr, whereas the formation of non protective oxide of iron might caused low corrosion resistance of carbon steel substrate.

Review of Z phase precipitation in 9–12 wt-%Cr steels

DEFF Research Database (Denmark)

Danielsen, Hilmar Kjartansson

2016-01-01

For high temperature applications, 9–12 wt-%Cr steels in fossil fired power plants rely upon precipitate strengthening from (V,Nb)N MX nitrides for long term creep strength. During prolonged exposure at service temperature, another nitride precipitates: Cr(V,Nb)NZ phase. The Z phases lowly replace......MX, eventually causing a breakdown in creep strength. The present paper reviews the Z phase and its behaviour in 9–12 wt-%Cr steels including thermodynamic modelling, crystal structure, nucleation process and precipitation rate as a function of chemical composition. The influence of Z phase precipitation upon...

Numerical simulation of Cr2N age-precipitation in high nitrogen stainless steels

International Nuclear Information System (INIS)

Dai, Q.X.; Yuan, Z.Z.; Luo, X.M.; Cheng, X.N.

2004-01-01

At the temperature raging from 700 to 950 deg. C, the Cr 2 N age-precipitation in high nitrogen austenitic stainless steels Fe24Mn18Cr3Ni0.62N was investigated in this paper. A qualitative mathematical model of Cr 2 N age-precipitation, ln t S = f (Me,1/T), was established based on the thermodynamics and kinetics and phase transformation theories. Satisfactory results were obtained by means of the test of artificial neural network. This mathematical model can be applied to the calculation design and predication of Cr 2 N age-precipitation in high nitrogen stainless steels

Influence of Z-phase on long-term creep stability of martensitic 9-12% Cr steels

Energy Technology Data Exchange (ETDEWEB)

Danielsen, Hilmar K. [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Mechanical Engineering; Hald, John [DONG Energy A/S (Denmark); Vattenfall (Denmark)

2010-07-01

The long-term creep strength of the new generation of martensitic creep resistant 9-12%Cr steels since the well-known steel Grade 91 relies strongly on particle strengthening by fine Mn nitrides based on V and Nb. During long-term high-temperature exposures the Mn nitrides may be replaced by the thermodynamically more stable Z-phases (Cr(V,Nb)N) causing a breakdown in creep strength. Cr contents above 10.5% strongly accelerate Z-phase precipitation, which explains the lack of success for all attempts to develop martensitic creep resistant steels with high Cr content for oxidation protection. However 9%Cr steels do not seem to be affected by the Z-phase. Careful control of the Z-phase precipitation process has led to the design of experimental 12%Cr martensitic steels strengthened by fine Z-phase nitrides based on Nb or Ta. Such steels may again enable the combination of high strength and oxidation resistance in the same alloy. This opens a new pathway for further alloy development of the heat resistant martensitic steels. (orig.)

Contamination assessment of heavy metals in the soils around Khouzestan Steel Company (Ni, Mn, Pb, Fe, Zn, Cr)

International Nuclear Information System (INIS)

Hormozi Nejad, F.; Rastmanesh, F.; Zarasvandi, A.

2016-01-01

The highest concentrations were found at soil samples 4 and 12. Comparison of heavy metals concentration with unpolluted soil standard indicated that, concentrations of Cr, Zn, Fe, Ni and Pb is higher than that of unpolluted soil standard. In general, Manganese, Chromium, Zinc and Lead are the most important elements that are found in emissions of steel plants. The soil samples near the steel plant and downwind direction have much higher pollution level. The results showed that Mn, Pb and Zn is related to human activity and Cr have geogenic source and Fe and Ni have both geogenic and anthropogenic source in the study area in the city of Ahwaz.

Slurry Erosion Studies on Surface Modified 13Cr-4Ni Steels: Effect of Angle of Impingement and Particle Size

Science.gov (United States)

Manisekaran, T.; Kamaraj, M.; Sharrif, S. M.; Joshi, S. V.

2007-10-01

Hydroturbine steels, such as 13Cr-4Ni martensitic steels, are generally subjected to heavy-erosive wear and loss of efficiency due to solid particulate entrainment in the water. Surface-modified steels have proven to give better performance in terms of erosive wear resistance. In the present study, an attempt is made to investigate the effect of angle of impingement and particle size on slurry-jet erosion behavior of pulsed plasma nitrided and laser hardened 13Cr-4Ni steels. Laser hardening process has shown good performance at all angles of impingement due to martensitic transformation of retained austenite. Plastic deformation mode of material removal was also an evident feature of all laser-hardened surface damage locations. However, pulsed-plasma nitrided steels have exhibited chip formation and micro-cutting mode of erosive wear. Erosion with 150-300 μm size was twice compared to 150 μm size slurry particulates.

Hot Corrosion Behavior of Stainless Steel with Al-Si/Al-Si-Cr Coating

Science.gov (United States)

Fu, Guangyan; Wu, Yongzhao; Liu, Qun; Li, Rongguang; Su, Yong

2017-03-01

The 1Cr18Ni9Ti stainless steel with Al-Si/Al-Si-Cr coatings is prepared by slurry process and vacuum diffusion, and the hot corrosion behavior of the stainless steel with/without the coatings is studied under the condition of Na2SO4 film at 950 °C in air. Results show that the corrosion kinetics of stainless steel, the stainless steel with Al-Si coating and the stainless steel with Al-Si-Cr coating follow parabolic laws in several segments. After 24 h corrosion, the sequence of the mass gain for the three alloys is the stainless steel with Al-Si-Cr coating coating coating. The corrosion products of the three alloys are layered. Thereinto, the corrosion products of stainless steel without coating are divided into two layers, where the outside layer contains a composite of Fe2O3 and FeO, and the inner layer is Cr2O3. The corrosion products of the stainless steel with Al-Si coating are also divided into two layers, of which the outside layer mainly consists of Cr2O3, and the inner layer is mainly SiO2. The corrosion film of the stainless steel with Al-Si-Cr coating is thin and dense, which combines well with substrate. Thereinto, the outside layer is mainly Cr2O3, and the inside layer is Al2O3. In the matrix of all of the three alloys, there exist small amount of sulfides. Continuous and protective films of Cr2O3, SiO2 and Al2O3 form on the surface of the stainless steel with Al-Si and Al-Si-Cr coatings, which prevent further oxidation or sulfide corrosion of matrix metals, and this is the main reason for the much smaller mass gain of the two alloys than that of the stainless steel without any coatings in the 24 h hot corrosion process.

Study of magnetism in Ni-Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

Science.gov (United States)

Kishore, G. V. K.; Kumar, Anish; Chakraborty, Gopa; Albert, S. K.; Rao, B. Purna Chandra; Bhaduri, A. K.; Jayakumar, T.

2015-07-01

Nickel base Ni-Cr alloy variants are extensively used for hardfacing of austenitic stainless steel components in sodium cooled fast reactors (SFRs) to avoid self-welding and galling. Considerable difference in the compositions and melting points of the substrate and the Ni-Cr alloy results in significant dilution of the hardface deposit from the substrate. Even though, both the deposit and the substrate are non-magnetic, the diluted region exhibits ferromagnetic behavior. The present paper reports a systematic study carried out on the variations in microstructures and magnetic behavior of American Welding Society (AWS) Ni Cr-C deposited layers on 316 LN austenitic stainless steels, using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The phase variations of the oscillations of a Co-Cr alloy coated magnetic field sensitive cantilever is used to quantitatively study the magnetic strength of the evolved microstructure in the diluted region as a function of the distance from the deposit/substrate interface, with the spatial resolution of about 100 nm. The acquired AFM/MFM images and the magnetic property profiles have been correlated with the variations in the chemical compositions in the diluted layers obtained by the energy dispersive spectroscopy (EDS). The study indicates that both the volume fraction of the ferromagnetic phase and its ferromagnetic strength decrease with increasing distance from the deposit/substrate interface. A distinct difference is observed in the ferromagnetic strength in the first few layers and the ferromagnetism is observed only near to the precipitates in the fifth layer. The study provides a better insight of the evolution of ferromagnetism in the diluted layers of Ni-Cr alloy deposits on stainless steel.

The entire mean stress relaxation effects of 0Cr18Ni10Ti piping steel

International Nuclear Information System (INIS)

Yang Bing; Zhao Yongxiang

2005-01-01

Experimental study is performed on the mean stress relaxation effects of the Chinese new piping material, 0Cr18Ni10Ti steel. Six sets of specimens are respectively fatigued under a strain-controlled mode with the six straining ratios (R ε ) of -1, -0.52, -0.22, 0.029, 0.18, and 0.48 by an improved test method implied with an maximum likelihood statistical principle. The test results reveal that the material exhibits a Masing behaviour and, surprisingly, involves an entire mean stress relaxation. A challenge is then emerging to the traditional same treat of straining ratio and stressing ratio (R σ ) in fatigue analysis and assessment. There is still no effective method to describe this kind of relaxation. However the R ε effects can represent the relaxation effects appropriately by investigation on the material random cyclic stress-strain (σ-ε) relations and strain-life (ε-N) relations with different R ε . The intrinsic randomness of the responses is taken into account on a probabilistic sense. Significant differences are observed of the material cyclic responses under different R ε . For σ-ε relations, the R ε effects act as a decreasing trend to the stress amplitudes with the increasing survival probability and confidence. The strongest effect appears at R ε of 0.029, and a weaker one acts as R ε is far away from zero. For ε-N relations, R ε greater than zero exhibits a positive effect on the fatigue lives of about 1.3 to 1.6 times under a survival probability of 0.999 and a confidence of 95%, while a negative effect is exhibited in case of R ε less than zero. Present work indicates that systematic researches should be made to give a reasonable fatigue prediction in service on a basis of cyclic strain inspection of structures. (authors)

Comparison of Steam Oxidation of 18%Cr Steels from Various Power Plants

DEFF Research Database (Denmark)

Montgomery, Melanie; Hald, John

2015-01-01

Lean austenitic steels such as the 18%Cr TP347H have been utilized in many power plants in Denmark. Steam oxidation has been investigated for both coarse-grained and fine-grained versions of TP347H. Oxidation for coarsegrained steels follows a parabolic rate however this is not always the case fo...

Characteristics of Modified 9Cr-1Mo Steel for Reactor Pressure Vessel of Very High Temperature Gas Cooled Reactor

Energy Technology Data Exchange (ETDEWEB)

Kim, Sung Ho; Ryu, W. S.; Han, Chang Hee; Yoon, J. H.; Chang, Jong Hwa

2004-11-15

Many researches and developments have been progressed for the construction of VHTR by 2020 in Korea. Modified 9Cr-1Mo steel has been receiving attention for the application to the reactor pressure vessel material of VHTR. We collected and analyzed the research data for modified 9Cr-1Mo steel in order to understand the characteristics of modified 9Cr-1Mo steel. The modified 9Cr-1Mo steel is a modified alloy system similar to conventional 9Cr-1Mo grade ferritic steel. Modifications include additions of vanadium, niobium, and nitrogen, as well as lower carbon content. In this report, we summarized the change of microstructure and mechanical properties after tempering, thermal aging, and irradiation. Modified 9Cr-1Mo steel has high strength and thermal conductivity, low thermal expansion, and good resistance to corrosion. But the irradiation embrittlement behavior of modified 9Cr-1Mo steel should be evaluated and the evaluation methodology also should be developed. At the same time, the characteristics of weldment which is the weak part in pressure vessel should be evaluated.

Microstructures and mechanical properties of 9Cr oxide dispersion strengthened steel produced by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Xie, Rui [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); School of Metallurgy, Northeastern University, Shenyang 110819 (China); Lu, Zheng, E-mail: luz@atm.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); Lu, Chenyang; Li, Zhengyuan [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); Ding, Xueyong [School of Metallurgy, Northeastern University, Shenyang 110819 (China); Liu, Chunming [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China)

2017-02-15

Highlights: • A 9Cr-ODS steel was produced by mechanical alloying and spark plasma sintering. • Bimodal grain size distribution was observed. • Formation mechanism of bimodal grain size distribution was discussed. • The size and number density of nanoscale particles were obtained by SAXS and HRTEM. • The contribution of nano-sized particles to yield strength is dominating. - Abstract: 9Cr oxide dispersion strengthened (ODS) steel was fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). The nano-sized particles, grain size distribution and mechanical properties of 9Cr-ODS steel sintered at 950 °C were studied by synchrotron radiation small angle X-ray scattering (SAXS), high-resolution transmission electron microscopy (HRTEM), electron backscatter diffraction (EBSD) and tensile experiment. The results showed that bimodal grain size distribution in the matrix is observed, which is attributed to the heterogeneous recrystallization process during the SPS. High-density nano-sized Y{sub 2}Ti{sub 2}O{sub 7} and some large oxides of Cr{sub 2}Mn(Ti)O{sub 4} are formed in 9Cr-ODS steel. The number density and average size of Y{sub 2}Ti{sub 2}O{sub 7} obtained from SAXS are 4.72 × 10{sup 22}/m{sup 3} and 4.4 nm, respectively. The yield strengths of 9Cr-ODS steel fabricated by SPS are compared with the typical 9Cr-ODS steel produced by HIP.

Effect of Solution Annealing on Susceptibility to Intercrystalline Corrosion of Stainless Steel with 20% Cr and 8% Ni

Science.gov (United States)

Taiwade, R. V.; Patil, A. P.; Patre, S. J.; Dayal, R. K.

2013-06-01

In general, as-received (AR) austenitic stainless steels (ASSs) contain complex carbide precipitates due to manufacturing operations, subsequent annealing treatment, or due to the fabrication processes such as welding. The presence of pre-existing carbides leads to cumulative sensitization and make the steel susceptible to intercrystalline corrosion (ICC)/intergranular corrosion (IGC) which causes premature failure during service. Solution annealing (SA) is one of the ways to deal with such situations. In this present investigation, the AR (hot rolled and mill annealed) chromium-nickel (Cr-Ni) ASS is compared with SA Cr-Ni ASS. The extent of ICC/IGC was evaluated qualitatively and quantitatively by various electrochemical tests including ASTM standard A-262 Practice A and Practice E, double loop electrochemical potentiokinetic reactivation and electrochemical impedance spectroscopy. The degree of sensitization for hot rolled mill annealed AR condition is found to be substantially higher (51.55%) than that of SA condition (26.9%) for thermally aged samples (at 700 °C). The chemical composition across the grain boundary was measured using electron probe micro-analyzer for both (AR and SA) conditions and confirms that the pre-sensitization effect was completely removed after SA treatment.

Microstructure and long-term creep properties of 9–12% Cr steels

DEFF Research Database (Denmark)

Hald, John

2008-01-01

Advanced microstructure characterisation and microstructure modelling has demonstrated that long-term microstructure stability in 9–12% Cr steels under technical loading conditions is equivalent to precipitate stability. Mo and W can have a positive influence on long-term creep strength of 9–12% Cr...

Influence of Normalizing Temperature on the Microstructure and Hardness of 9Cr-1Mo ODS Steel

Energy Technology Data Exchange (ETDEWEB)

Jang, Ki Nam; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Kyu Tae [Dongguk University, Gyeongju (Korea, Republic of)

2016-10-15

Oxide dispersion strengthened(ODS) steel has superior high-temperature strength and creep properties because fine oxide particles having an excellent stability at high temperatures are uniformly distributed in the matrix. ODS steel has being developed for structure materials of sodium fast cooled reactor(SFR) because of its excellent irradiation resistance and mechanical properties. 9Cr-1Mo ODS steel has better high temperature strength and irradiation resistance than common 9Cr-1Mo steel because Y{sub 2}O{sub 3} nano-sized particles which interrupt dislocation movement and grain boundary slip are uniformly dispersed in the martensite matrix. The mechanical properties of the ODS steels are mainly determined by their microstructures, and the microstructure is considerably decided by the heat-treatment conditions. This study focused on the effect of normalizing temperature on microstructure and hardness of 9Cr-1Mo martensitic ODS steel so as to optimize the heat-treatment condition. In this study, the effect of normalizing temperature on mechanical property and microstructures of 9Cr-1Mo martensitic ODS steel was investigated. It was shown that the microhardness was steadily increased with increasing of the normalizing temperature. According to TEM observation, mechanical property of 9Cr-1Mo ODS steel was significantly affected by lath width. These observations, could be useful to understand the relationship between normalizing temperature and microstructure.

Si effects on radiation induced segregation in high purity Fe-18Cr-14Ni alloys irradiated by Ni ions

International Nuclear Information System (INIS)

Ohta, Joji; Kako, Kenji; Mayuzumi, Masami; Kusanagi, Hideo; Suzuki, Takayoshi

1999-01-01

To illustrate the effects of the element Si on radiation induced segregation, which causes irradiation assisted stress corrosion cracking (IASCC), we investigated grain boundary chemistry of high purity Fe-18Cr-14Ni-Si alloys irradiated by Ni ions using FE-TEM. The addition of Si up to 1% does not affect the Cr depletion at grain boundaries, while it slightly enhances the depletion of Fe and the segregation of Ni and Si. The addition of 2% Si causes the depletion of Cr and Fe and the segregation of Ni and Si at grain boundaries. Thus, the Si content should be as low as possible. In order to reduce the depletion of Cr at grain boundaries, which is one of the major causes of IASCC, Si content should be less than 1%. (author)

Microstructure-based assessment of creep rupture strength in 9Cr steels

International Nuclear Information System (INIS)

Spigarelli, S.

2013-01-01

A microstructure-based model to assess the long-term creep strength in 9Cr steels is proposed. The model takes into account a number of different key issues, including the presence and evolution of the most important families of precipitates (M 23 C 6 , MX, Laves and Z phases), the subgrain recovery process, the different strengthening mechanisms (solid solution strengthening and particle strengthening), and is able to give realistic values of the long-term creep strength in P9, P91 and P911 steels. If properly tuned to describe the mid/long-term precipitation of the Z-phase, and the concurrent dissolution of MX precipitates, the model can also predict the sigmoidal behaviour which leads to the early rupture of single heats of P91 steel. Highlights: ► Creep response at 600 °C of 9% Cr steels. ► Important effect of the different families of precipitates. ► The effect is described by introducing the grain size term in a previously developed model. ► Degradation of particle strengthening effect is considered by calculating the coarsening of the particles.

Structure of steel 8 CrMoNiNb 9 10 and its variations in long-term thermal stress

International Nuclear Information System (INIS)

Fabritius, H.; Schnabel, E.

1976-01-01

On four casts of steel 8 CrMoNiNb 9 10 with about 0.06% C, 0.25; Si, 0.7% Mn, 0.012% N, 0.002 to 0.020% Al, 2.25% Cr, 0.94% Mo, 0.63 to 0.91% Nb and 0.67% Ni, transformation behaviour and structural changes during long-time annealing at 500 to 750 degC lasting up to 30,000 h were studied in unformed condition and after previous cold forming. The carbon content was largely bound in form of primary niobium carbonitrides so that during quenching and tempering low-carbon bainite was formed, or at very slow cooling a ferritic structure without pearlite. Martensite occurred only after fast cooling from temperatures above 1200 degC. Bainite exhibited a very high dislocation density and a large number of coherent niobium carbonitrides. During tempering, the precipitates overaged, and the dislocations started to arrange themselves to subgrain boundaries. Hardness and strength in quenched and tempered condition were essentially governed by dislocation density and size of subgrains. In the whole range of bainite transformation, they are only slightly dependent upon the cooling rate and hence upon the dimensions of the products. The structural changes which occurred in bainitic material during long-time aging and led to a ferritic structure in the final state were interpreted as recovery and recrystallization. In unformed and slightly formed material recrystallization led to a very coarse-grained structure. In highly formed material a very fine-grained structure was achieved by recrystallization. By a high degree of cold forming the recrystallization process was considerably promoted. With an annealing time of 10 5 h, no recrystallization is to be expected for unformed specimens of the studied cast up to 580 degC, but above 650 degC complete recrystallization. (author)

Attempts to improve the fatigue characteristics of the austenitic steel X5CrNi18-10 in the temperature range of 25-600 C by mechanical boundary layer hardening; Zur Verbesserung des Ermuedungsverhaltens des austenitischen Stahls X5CrNi18-10 im Temperaturbereich 25-600 C durch mechanische Randschichtverfestigungsverfahren

Energy Technology Data Exchange (ETDEWEB)

Nikitin, Ivan

2007-01-31

Pieces of the austenitic steel X5CrNi18-10 whose boundary layers had been hardened by different methods were investigated with a view to their fatigue deformation characteristics in the temperature range of 25-600 degC. Parallel to this, microstructural and X-ray analyses provided deeper understanding of fatigue deformation. The microstructure was characterized, among others, by TEM. Boundary layers were solidified by rolling, by a combination of mechanical and thermal processes, by high-temperature rolling, and by laser shock solidification. The analyses focused on microstructural processes and on the intrinsic stress stability and provided important information on the fabrication of structural components with optimised life. (orig.)

Tensile strength and creep behaviour of austenitic stainless steel type 18Cr - 12Ni with niobium additions at 700°C

Science.gov (United States)

Sordi, V. L.; Bueno, L. O.

2010-07-01

The effect of niobium additions up to 2.36 wt% on the creep behavior of a series of seven extra low carbon 18Cr-12Ni austenitic stainless steels at 700°C has been investigated. Grain size and hardness measurements, hot tensile tests and constant stress creep tests from 90 to 180 MPa were carried out for each alloy, in the solution treated condition at 1050, 1200 and 1300°C followed by quench in water. The mechanical behavior at high temperature was related to the amount of NbC precipitation occurring during the tests. Solid solution and intermetallic compound effects were also considered. Creep data analysis was done to determine the parameters of the creep power-law equation dot epsilon = A.σn and the Monkman-Grant relation dot epsilon.tmR = K. Niobium-carbide precipitation in these steels reduces the secondary stage dependence of strain rate with applied stress, resulting in n-values which indicate the possibility of operation of various creep mechanisms. The creep strength during the secondary stage is primarily controlled by the amount of NbC available for precipitation. However, the rupture times increase progressively with niobium content, as the amount of undissolved carbide particles in grain boundaries and the Laves phase precipitation increase.

Creep rupture properties of oxidised 20%Cr austenitic stainless steels

International Nuclear Information System (INIS)

Lobb, R.C.; Ecob, R.C.

1989-02-01

Sheet specimens of stabilised 20%Cr/25%Ni/Nb and nitrided 20%Cr/25%Ni/Ti stainless steels, both used as fuel cladding materials in CAGRs, have been oxidised in simulated reactor gas (Co 2 /1-2%CO) for up to l.9kh at 850 0 C, including intermediate thermal cycles to room temperature. The oxidised specimens have been creep tested subsequently at 750 0 C, under conditions of constant stress. The creep rupture properties are affected differently for the two materials. For 20%Cr/25%Ni/Nb stainless steel, there was no effect of oxidation on the intrinsic microstructure, when compared with thermally aged, non-oxidised material. Any differences in creep ductility were ascribed to geometric effects in specimens of this alloy. Lower ductilities were associated with an increased incidence of pitting attack (higher oxide spallation) and it was concluded that the extent of local, rather than general, loss of section controlled the ductility. For nitrided 20%Cr/25%Ni/Ti stainless steel, the intrinsic microstructure was affected by oxidation, such that increased grain boundary precipitation of M 23 C 6 occurred. The resultant effect was for a greater tendency for intergranular failure at lower ductility than for the thermally aged material. The magnitude of this reduction could not be quantified because the specimen geometry was also changed by oxidation. In this instance, the oxidation mode that produced the most severe loss of section was grain boundary, rather than pitting, attack. This mode of attack was not linked directly to oxide fracture/spallation, but to the period of oxidation. (author)

Mechanical properties of steel X 6 CrNi 18 11 after creep

Energy Technology Data Exchange (ETDEWEB)

Heesen, E te; Lorenz, H; Grosser, E D [INTERATOM, Bergisch Gladbach (Germany)

1977-07-01

Test series were conducted to determine the influence of prior creep on the mechanical properties of X 6 CrNi 18 11 base material, weld joint and weld metal. Creep and tensile tests on base and weld joint were performed at 600 degrees C, the weld metal was Investigated at 550, 600, and 650 degrees C. With regard to the base materials, prior creep leads to a significant reduction in tensile ductility combined with an increase of the 0.2 % proof stress. Residual ductility represents a sufficient ductility reserve. For the weld joint tensile strength remains unchanged up to the end of the secondary creep stage. Although tensile elongation and reduction of area decrease, the relative reduction is less compared to the base material. Concerning the weld metal the 0.2 % proof stress reveals a marked decrease due to the test temperature leading to a stress relief heat treatment. Ultimate tensile strength and ductility Indicate little or no deviations from the original values. Thermal exposures in the absence of stress nearly gave the same properties as were found on precrept specimens. (author)

Determination of Cr, Mn, Si, and Ni in carbon steels by optical emission spectrometry with spark source

International Nuclear Information System (INIS)

Garcia Gonzalez, M.A.; Pomares Alfonso, M.; Mora Lopez, L.

1995-01-01

Elemental composition of steels determines some important of his characteristic moreover it is necessary to obtain their quality certification. Analytical procedure has performed for determination of Cr, Mn, Si and Ni in carbon steels by optical emission spectrometry with spark source. reproducibility of results is 5-11 %. Exactitude has tested with results that have obtained by internationally recognised methods-

Microstructure and Tribological Properties of AlCoCrFeNiTi0.5 High-Entropy Alloy in Hydrogen Peroxide Solution

Science.gov (United States)

Yu, Y.; Liu, W. M.; Zhang, T. B.; Li, J. S.; Wang, J.; Kou, H. C.; Li, J.

2014-01-01

Microstructure and tribological properties of an AlCoCrFeNiTi0.5 high-entropy alloy in high-concentration hydrogen peroxide solution were investigated in this work. The results show that the sigma phase precipitates and the content of bcc2 decrease during the annealing process. Meanwhile, the complex construction of the interdendrite region changes into simple isolated-island shape, and much more spherical precipitates are formed. Those changes of microstructure during the annealing process lead to the increase of hardness of this alloy. In the testing conditions, the AlCoCrFeNiTi0.5 alloy shows smoother worn surfaces and steadier coefficient of friction curves than does the 1Cr18Ni9Ti stainless steel, and SiC ceramic preserves better wear resistance than ZrO2 ceramic. After annealing, the wear resistance of the AlCoCrFeNiTi0.5 alloy increases coupled with SiC counterface but decreases with ZrO2 counterface.

Damage development in 9%Cr steels

International Nuclear Information System (INIS)

Rauch, M.; Maile, K.

2003-01-01

Modern 9-11% martensitic steels are candidate materials to be used in modern fossil fired power plants with high efficiency rates. The focus of the R and D work is put on the further development and optimisation, the determination of material characteristics but also on the identification and quantification of damage mechanisms and the damage evolution. For this purpose extensive experiments such as long creep tests on specimens under internal pressure, metallurgical examinations and theoretical investigations for determination of stress-strain state which have been conducted. The laboratory tests are completed by examination of real components. As a result an empirical description of the creep cavity density as a function of deformation and multiaxiality of stress state has been carried out which can be used in further FE-calculations determining the damage state. The results of all metallographical examinations on specimens with different heat treatments and service loads are summarised in a structure atlas and are published for further usage. Damage development, martensitic 9 % Cr steels, creep cavity density, creep tests under multiaxial load, metallographical investigations, and measurements on pipe bends. (author)

Steamside Oxidation Behavior of Experimental 9%Cr Steels

Energy Technology Data Exchange (ETDEWEB)

Dogan, O.N.; Holcomb, G.R.; Alman, D.E.; Jablonski, P.D.

2007-10-01

Reducing emissions and increasing economic competitiveness require more efficient steam power plants that utilize fossil fuels. One of the major challenges in designing these plants is the availability of materials that can stand the supercritical and ultra-supercritical steam conditions at a competitive cost. There are several programs around the world developing new ferritic and austenitic steels for superheater and reheater tubes exposed to the advanced steam conditions. The new steels must possess properties better than current steels in terms of creep strength, steamside oxidation resistance, fireside corrosion resistance, and thermal fatigue resistance. This paper introduces a series of experimental 9%Cr steels containing Cu, Co, and Ti. Stability of the phases in the new steels is discussed and compared to the phases in the commercially available materials. The steels were tested under both the dry and moist conditions at 650ºC for their cyclical oxidation resistance. Results of oxidation tests are presented. Under the moist conditions, the experimental steels exhibited significantly less mass gain compared to the commercial P91 steel. Microstructural characterization of the scale revealed different oxide compositions.

Low-Cycle Fatigue Behavior of 10CrNi3MoV High Strength Steel and Its Undermatched Welds.

Science.gov (United States)

Song, Wei; Liu, Xuesong; Berto, Filippo; Razavi, S M J

2018-04-24

The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern for engineering structure design, especially for the welded joints. The paper presents a comparison of the low cycle fatigue behaviors between 10CrNi3MoV high strength steel and its undermatched weldments. Uniaxial tension tests, Push-pull, strain-controlled fatigue tests were conducted on base metal and weldments in the strain range of 0.2⁻1.2%. The monotonic and cyclic stress-strain curves, stress-life, strain-life and energy-life in terms of these materials were analyzed for fatigue assessment of materials discrepancy. The stress-life results of base metal and undermatched weld metal exhibit cyclic softening behaviors. Furthermore, the shapes of 10CrNi3MoV steel hysteresis loops show a satisfactory Masing-type behavior, while the weld metal shows a non-Masing type behavior. Strain, plastic and total strain energy density amplitudes against the number of reversals to failure results demonstrate that the undermatched weld metal presents a higher resistance to fatigue crack initiation than 10CrNi3MoV high strength steel. Finally, fatigue fracture surfaces of specimens were compared by scanning electron microscopy to identify the differences of crack initiation and the propagation between them.

Low-Cycle Fatigue Behavior of 10CrNi3MoV High Strength Steel and Its Undermatched Welds

Directory of Open Access Journals (Sweden)

Wei Song

2018-04-01

Full Text Available The use of high strength steel allows the design of lighter, more slender and simpler structures due to high strength and favorable ductility. Nevertheless, the increase of yield strength does not guarantee the corresponding improvement of fatigue resistance, which becomes a major concern for engineering structure design, especially for the welded joints. The paper presents a comparison of the low cycle fatigue behaviors between 10CrNi3MoV high strength steel and its undermatched weldments. Uniaxial tension tests, Push-pull, strain-controlled fatigue tests were conducted on base metal and weldments in the strain range of 0.2–1.2%. The monotonic and cyclic stress-strain curves, stress-life, strain-life and energy-life in terms of these materials were analyzed for fatigue assessment of materials discrepancy. The stress-life results of base metal and undermatched weld metal exhibit cyclic softening behaviors. Furthermore, the shapes of 10CrNi3MoV steel hysteresis loops show a satisfactory Masing-type behavior, while the weld metal shows a non-Masing type behavior. Strain, plastic and total strain energy density amplitudes against the number of reversals to failure results demonstrate that the undermatched weld metal presents a higher resistance to fatigue crack initiation than 10CrNi3MoV high strength steel. Finally, fatigue fracture surfaces of specimens were compared by scanning electron microscopy to identify the differences of crack initiation and the propagation between them.

Effects of the Microstructure on Segregation behavior of Ni-Cr-Mo High Strength Low Alloy RPV Steel

Energy Technology Data Exchange (ETDEWEB)

Park, Sang Gyu; Wee, Dang Moon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2010-10-15

SA508 Gr.4N Ni-Cr-Mo low alloy steel has an improved fracture toughness and strength, compared to commercial Mn-Mo-Ni low alloy RPV steel SA508 Gr.3. Higher strength and fracture toughness of low alloy steels could be achieved by adding Ni and Cr. So there are several researches on SA508 Gr.4N low alloy steel for a RPV application. The operation temperature and time of a reactor pressure vessel is more than 300 .deg. C and over 40 years. Therefore, in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel, it requires a resistance of thermal embrittlement in the high temperature range including temper embrittlement resistance. S. Raoul reported that the susceptibility to temper embrittlement was increasing a function of the cooling rate in SA533 steel, which suggests the martensitic microstructures resulting from increased cooling rates are more susceptible to temper embrittlement. However, this result has not been proved yet. So the comparison of temper embrittlement behavior was made between martensitic microstructure and bainitic microstructure with a viewpoint of boundary features in SA508 Gr.4N, which have mixture of tempered bainite/martensite. In this study, we have compared temper embrittlement behaviors of SA508 Gr.4N low alloy steel with changing volume fraction of martensite. The mechanical properties of these low alloy steels) were evaluated after a long-term heat treatment(450 .deg. C, 2000hr. Then, the images of the segregated boundaries were observed and segregation behavior was analyzed by AES. In order to compare the misorientation distributions of model alloys, grain boundary structures were measured with EBSD

Welding and corrosion resistance of the new nitrogen alloyed steel X2 CrNiMnMoN241764

International Nuclear Information System (INIS)

Arit, N.; Henser, H.; GroB, V.

1994-01-01

Remanit 4565 S is a new developed nitrogen alloyed austenitic stainless steel. Characteristic features are: improved strength and toughness, delayed precipitation of carbides and intermetallic phases, improved corrosion resistance. Welding fabrication is possible without the risk of pore formation. TIG-welded joints are as resistant as the base metal, using filler metal SG-NiCr 20 Mo 15 (Thermanit Nimo C) respectively SG-NiCr 28 Mo(Thermanit 30/40 E) according to the area of application. (Author) 8 refs

Relationship between thermal embrittlement and hydrogen cracking in 18Ni(250) maraging steel

International Nuclear Information System (INIS)

Rack, H.J.

1974-01-01

The role of grain boundary precipitate structure on the stress corrosion susceptibility of 18Ni(250) maraging steel was examined. Varying solution treatment procedures were used to achieve either a precipitate-free grain boundary or one containing a high density of Ti(C,N) particles. The introduction of these treatments, although drastically affecting the monotonic fracture toughness, did not significantly alter the stress corrosion threshold in 100 percent relative humidity. These results are shown to be consistent with the previous suggestion that, under open circuit conditions, hydrogen-assisted cracking controls the environmental crack growth behavior of 18Ni maraging steels. (U.S.)

Short Communication on “Self-welding susceptibility of NiCr-B hardfaced coating with and without NiCr-B coating on 316LN stainless steel in flowing sodium at elevated temperature”

Energy Technology Data Exchange (ETDEWEB)

Kumar, Hemant, E-mail: hemant@igcar.gov.in [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur, Kharagpur, 721 302 (India); Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Ramakrishnan, V.; Albert, S.K.; Bhaduri, A.K. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Ray, K.K. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur, Kharagpur, 721 302 (India)

2017-02-15

The self-welding susceptibility between NiCr-B coated 316LN stainless steel and the base metal, and that between NiCr-B hardfaced coatings has been evaluated in flowing sodium at 823 K for 90 and 135 days under contact stress of 8.0 and 11.0 MPa using a fabricated set-up. Neither any self-welding could be observed nor could any damage be detected on the specimen surfaces of the selected materials under the imposed experimental conditions, which indicate their satisfactory potential for applications in Fast Breeder Reactors.

Evaluation of mechanical properties and nano-meso structures of 9–11%Cr ODS steels

Energy Technology Data Exchange (ETDEWEB)

Tanno, Takashi, E-mail: tanno.takashi@jaea.go.jp [Japan Atomic Energy Agency, Oarai, Ibaraki 311-1393 (Japan); Ohtsuka, Satoshi; Yano, Yasuhide; Kaito, Takeji [Japan Atomic Energy Agency, Oarai, Ibaraki 311-1393 (Japan); Oba, Yojiro; Ohnuma, Masato [National Institute for Materials Science, Tsukuba 305-1195 (Japan); Koyama, Shinichi; Tanaka, Kenya [Japan Atomic Energy Agency, Oarai, Ibaraki 311-1393 (Japan)

2013-09-15

Highlights: • We successfully manufactured 11Cr-ODS steels with residual α-ferrite controlled. • Dispersion conditions of nano oxide particles were quantitatively characterized. • Tungsten solid solution could improve only tensile strength of ODS steels at 973 K. • Oxide dispersion strengthening was dominant in creep strength of ODS steels at 973 K. -- Abstract: This study carried out mechanical tests and microstructural characterizations of several 9Cr and 11Cr-ODS tempered martensitic steels. From those results, the appropriate chemical composition range of 11Cr-ODS tempered martensitic steel was discussed from the viewpoint of high temperature strength improvement. It was shown that the residual α-ferrite fraction in 11Cr-ODS steel was successfully controlled to the same level as the 9Cr-ODS steel, which has excellent high temperature strength, by selecting the chemical compositions on the basis of the multi-component phase diagram. The tensile strength decreased with decreasing W content from 2.0 to 1.4 wt%. On the other hand, creep strength at 973 K did not degrade by the decreasing W content. Both tensile strength and creep strength increased with increasing population of the nano-sized oxide particles. Small angle X-ray scattering analysis revealed that titanium and excess oxygen contents were key parameters in order to improve the dispersion conditions of nano-sized oxide particles.

Stress-controlled inelastic behavior of modified 9 Cr-1 Mo steel at elevated temperatures

International Nuclear Information System (INIS)

Taguchi, Kosei.

1989-01-01

Interest in the ferritic steels of higher chromium concentration has increased recently because of an economical combination of mechanical and corrosion properties at elevated temperatures. A modified 9 Cr-1 Mo ferritic steel, developed in the United States, has been expected as an alternative structural material for fast breeder reactor components, in which Type 304 stainless steel or 2.25 Cr-1 Mo steel is currently used. For application of this material to the structural components, a lot of work has been done to develop evaluation methods for the deformation behavior and strength properties. The authors have studied the inelastic behavior and the creep-fatigue properties of modified 9 Cr-1 Mo steel at elevated temperatures, and proposed a constitutive equation and a creep-fatigue damage equation based on the overstress concept. In this paper, the applicability is discussed of the constitutive equation to stress-controlled inelastic behavior, such as creep strain hardening and stress cycling

Effect of load ratio and saltwater corrosive environment on the initiation life of fatigue of 10Ni5CrMoV steel

Science.gov (United States)

Xie, Xing; Yi, Hong; Xu, Jian; Gen, Liming; Chen, Luyun

2017-09-01

Fatigue initiation life has been studied with 10CrNi5MoV steel for use in ocean engineering at different load ratios and in different environmental media. The microstructure and micro-topography have been observed and analyzed by means of SEM, EDS and EBSD. Our findings indicate that, the initiation life of 10Ni5CrMoV steel in seawater is shorter than that in air, and the difference in longevity is larger with the increasing of load ratio. Corrosion pits had a great influence on initial corrosion fatigue life.

Study of the Weldability of Austenitic PH Steel for Power Plants

Directory of Open Access Journals (Sweden)

Ziewiec A.

2016-06-01

Full Text Available The article presents the results of Transvarestraint test of a modern precipitation hardened steel X10CrNiCuNb18-9-3 with copper. For comparison, the results of tests of conventional steel without the addition of copper X5CrNi18-10 are presented. The total length of all cracks and the maximum length of cracks were measured. The study of microstructure (LM, SEM showed that the austenitic stainless steel X10CrNiCuNb18-9-3 is very prone to hot cracking. After performing the Transvarestraint tests three types of cracks were observed: solidification cracks occurring during crystallization, liquation cracks due to segregation in the heat affected zone (HAZ and surface cracks. Niobium carbonitrides dispersed in the bands of segregation are the reason of high susceptibility to liquation cracking. Segregation of copper occurring during solidification causes of surface cracking. A combined effect of copper and stresses contributes to formation of hot microcracks. These microcracks propagate to a depth of 20-30 μm.

Cr-Ni ALLOY ELECTRODEPOSITION AND COMPARISON WITH CONVENTIONAL PURE Cr COATING TECHNIQUE

Directory of Open Access Journals (Sweden)

M. Moniruzzaman

2012-12-01

Full Text Available Cr coating is widely used as the outer surface of precision parts due to its attractive appearance and superior corrosion resistance properties. It is obtained by electrodeposition via a conventional bath with hexavalent Cr ions. This manufacturing technique has many drawbacks, such as very low efficiency and high operating temperature and it is hazardous to health. In this work, we studied a Cr-Ni alloy deposition technique and compared the alloy coating properties to those with conventional Cr coating. Sequential two-step alloy electrodeposition was also compared. We took varying concentrations of Cr, Ni and complexing agents for the electrodeposition of Cr-Ni alloy and sequential Cr-Ni alloy coating on mild steel. Operating parameters, i.e. current density and temperature, were varied to examine their effects on the coating properties. The coatings thus obtained were characterized by visual observation, corrosion test, microhardness measurement, morphology and chemical analysis. The Cr-Ni alloy coating was found to be more corrosion resistant in 5% NaCl solution and harder than the pure Cr coating obtained by conventional electrodeposition. Toxic gas was produced in a much lower extent in the alloy coating than the conventional Cr coating technique. Again, the two-step Cr-Ni alloy coating was found better in terms of corrosion resistance as well as hardness compared to the Cr-Ni alloy coating. The process was also found to be much more environmentally friendly.

Fracture Resistances of Y_2O_3 Particle Dispersion Strengthened 9Cr Steel at Room Temperature and High Temperatures

International Nuclear Information System (INIS)

Yoon, Ji Hyun; Kang, Suk Hoon; Lee, Yongbok; Kim, Sung Soo

2012-01-01

The fracture resistance and tensile properties of Y_2O_3 oxide dispersion strengthened steel containing 9 wt% Cr (9Cr-ODS) were measured at various temperatures up to 700°C. The fracture characteristics were compared with those of commercial E911 ferritic/martensitic steel. The strength of 9Cr-ODS was at least 30% higher than that of E911 steel at the test temperatures below 500°C. The strength difference between the two materials was almost diminished at 700°C. 9Cr-ODS showed cleavage fracture behavior at room temperature and unstable crack growth behaviors at 300°C and 500°C. The J-R fracture resistance of 9Cr-ODS was much lower than that of E911 steel at all temperatures. It was deduced that the coarse Cr_2O_3 particles that were formed during the alloying process provided the crack initiation sites of cleavage fracture in 9Cr-ODS.

Tensile properties of the modified 13Cr martensitic stainless steels

Energy Technology Data Exchange (ETDEWEB)

Mabruri, Efendi, E-mail: effe004@lipi.go.id; Anwar, Moch Syaiful, E-mail: moch.syaiful.anwar@lipi.go.id; Prifiharni, Siska, E-mail: siska.prifiharni@lipi.go.id; Romijarso, Toni B.; Adjiantoro, Bintang [Research Center for Metallurgy and Materials, Indonesian Institute of Sciences (LIPI) Kawasan Puspiptek Gd. 470 Serpong, Tangerang Selatan 15314 (Indonesia)

2016-04-19

This paper reports the influence of Mo and Ni on the tensile properties of the modified 13Cr martensitic stainless steels in tempered condition. Four steels with different content of Mo and Ni were prepared by induction melting followed by hot forging, quenching and tempering. The experimental results showed that the addition of about 1% and 3% Mo has a beneficial effect to increase both the tensile strength and the elongation of the steels. On the contrary, the addition of about 3% Ni into the martensitic stainless steel results in decreasing of both the tensile strength and the elongation. Among the alloys investigated the 13Cr3Mo type steel exhibited largest tensile strength of 1348 MPa and largest elongation of 12%. The observation on the tensile fractured surfaces by using scanning electron microscope supported these findings.

Tensile properties of the modified 13Cr martensitic stainless steels

International Nuclear Information System (INIS)

Mabruri, Efendi; Anwar, Moch Syaiful; Prifiharni, Siska; Romijarso, Toni B.; Adjiantoro, Bintang

2016-01-01

This paper reports the influence of Mo and Ni on the tensile properties of the modified 13Cr martensitic stainless steels in tempered condition. Four steels with different content of Mo and Ni were prepared by induction melting followed by hot forging, quenching and tempering. The experimental results showed that the addition of about 1% and 3% Mo has a beneficial effect to increase both the tensile strength and the elongation of the steels. On the contrary, the addition of about 3% Ni into the martensitic stainless steel results in decreasing of both the tensile strength and the elongation. Among the alloys investigated the 13Cr3Mo type steel exhibited largest tensile strength of 1348 MPa and largest elongation of 12%. The observation on the tensile fractured surfaces by using scanning electron microscope supported these findings.

Evaluation of dynamic fracture toughness of cold worked 9Cr-1Mo steel

International Nuclear Information System (INIS)

Sathyanarayanan, S.; Sasikala, G.; Ray, S.K.

2004-01-01

Dynamic J-R curves for cold worked 9Cr-1Mo steel have been estimated from instrumented impact test data at ambient temperature on pre-cracked Charpy specimens using three methods of analysis, namely those by Ray et al., Schindler, and Sreenivasan and Mannan. It is concluded that of these three, Schindler's method is the best suited for the purpose since it gives consistent variations with cold work of dynamic J-R curves and dynamic fracture toughness. Cold work results in substantial degradation in dynamic fracture toughness of 9Cr-1Mo steel

Consideration of the oxide particle-dislocation interaction in 9Cr-ODS steel

Science.gov (United States)

Ijiri, Yuta; Oono, N.; Ukai, S.; Yu, Hao; Ohtsuka, S.; Abe, Y.; Matsukawa, Y.

2017-05-01

The interaction between oxide particles and dislocations in a 9Cr-ODS ferritic steel is investigated by both static and in situ TEM observation under dynamic straining conditions and room temperature. The measured obstacle strength (?) of the oxide particles was no greater than 0.80 and the average was 0.63. The dislocation loops around some coarsened particles were also observed. The calculated obstacle strength by a stress formula of the Orowan interaction is nearly equaled to the average experimental value. Not only cross-slip system but also the Orowan interaction should be considered as the main interaction mechanism between oxide particles and dislocation in 9CrODS ferritic steel.

Analysis of High Temperature Deformed Structure and Dynamic Precipitation in W9Mo3Cr4V Steel

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

With TEM、SEM, various high-temperature deformed structures inW9Mo3Cr4V steel were investigated. The sub-structures，recrystallized nuclei, as well as the dynamic precipitation were also studied and analyzed. The relationship between recrystallized structures and dynamic precipitation was discussed. The results showed that the deformed structures in W9Mo3Cr4V steel are more complicated than those in low alloy steels. Because W9Mo3Cr4V steel is a high-speed steel, there are a large number of residual carbides on the matrix. Also, much dynamic precipitating carbides will precipitate during deformation at high temperature.

Effect of titanium on the creep deformation behaviour of 14Cr-15Ni-Ti stainless steel

Science.gov (United States)

Latha, S.; Mathew, M. D.; Parameswaran, P.; Nandagopal, M.; Mannan, S. L.

2011-02-01

14Cr-15Ni-Ti modified stainless steel alloyed with additions of phosphorus and silicon is a potential candidate material for the future cores of Prototype Fast Breeder Reactor. In order to optimise the titanium content in this steel, creep tests have been conducted on the heats with different titanium contents of 0.18, 0.23, 0.25 and 0.36 wt.% at 973 K at various stress levels. The stress exponents indicated that the rate controlling deformation mechanism was dislocation creep. A peak in the variation of rupture life with titanium content was observed around 0.23 wt.% titanium and the peak was more pronounced at lower stresses. The variation in creep strength with titanium content was correlated with transmission electron microscopic investigations. The peak in creep strength exhibited by the material with 0.23 wt.% titanium is attributed to the higher volume fraction of fine secondary titanium carbide (TiC) precipitates.

Effect of titanium on the creep deformation behaviour of 14Cr-15Ni-Ti stainless steel

Energy Technology Data Exchange (ETDEWEB)

Latha, S. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603 102 (India); Mathew, M.D., E-mail: mathew@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603 102 (India); Parameswaran, P.; Nandagopal, M. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603 102 (India); Mannan, S.L. [National Engineering College, Kovilpatti, Tamil Nadu 628 503 (India)

2011-02-28

14Cr-15Ni-Ti modified stainless steel alloyed with additions of phosphorus and silicon is a potential candidate material for the future cores of Prototype Fast Breeder Reactor. In order to optimise the titanium content in this steel, creep tests have been conducted on the heats with different titanium contents of 0.18, 0.23, 0.25 and 0.36 wt.% at 973 K at various stress levels. The stress exponents indicated that the rate controlling deformation mechanism was dislocation creep. A peak in the variation of rupture life with titanium content was observed around 0.23 wt.% titanium and the peak was more pronounced at lower stresses. The variation in creep strength with titanium content was correlated with transmission electron microscopic investigations. The peak in creep strength exhibited by the material with 0.23 wt.% titanium is attributed to the higher volume fraction of fine secondary titanium carbide (TiC) precipitates.

Effect of titanium on the creep deformation behaviour of 14Cr-15Ni-Ti stainless steel

International Nuclear Information System (INIS)

Latha, S.; Mathew, M.D.; Parameswaran, P.; Nandagopal, M.; Mannan, S.L.

2011-01-01

14Cr-15Ni-Ti modified stainless steel alloyed with additions of phosphorus and silicon is a potential candidate material for the future cores of Prototype Fast Breeder Reactor. In order to optimise the titanium content in this steel, creep tests have been conducted on the heats with different titanium contents of 0.18, 0.23, 0.25 and 0.36 wt.% at 973 K at various stress levels. The stress exponents indicated that the rate controlling deformation mechanism was dislocation creep. A peak in the variation of rupture life with titanium content was observed around 0.23 wt.% titanium and the peak was more pronounced at lower stresses. The variation in creep strength with titanium content was correlated with transmission electron microscopic investigations. The peak in creep strength exhibited by the material with 0.23 wt.% titanium is attributed to the higher volume fraction of fine secondary titanium carbide (TiC) precipitates.

Corrosion behavior of steels in liquid lead bismuth with low oxygen concentrations

Science.gov (United States)

Kurata, Yuji; Futakawa, Masatoshi; Saito, Shigeru

2008-02-01

Corrosion tests in pots were conducted to elucidate corrosion behavior of various steels in liquid lead-bismuth for 3000 h under the condition of an oxygen concentration of 5 × 10 -8 wt% at 450 °C and an oxygen concentration of 3 × 10 -9 wt% at 550 °C, respectively. Significant corrosion was not observed at 450 °C for ferritic/martensitic steels, F82H, Mod.9Cr-1Mo steel, 410SS, 430SS except 2.25Cr-1Mo steel. Pb-Bi penetration into steels and dissolution of elements into Pb-Bi were severe at 550 °C even for ferritic/martensitic steels. Typical dissolution attack occurred for pure iron both at 550 °C without surface Fe 3O 4 and at 450 °C with a thin Fe 3O 4 film. Ferritization due to dissolution of Ni and Cr, and Pb-Bi penetration were recognized for austenitic stainless steels, 316SS and 14Cr-16Ni-2Mo steel at both temperatures of 450 °C and 550 °C. The phenomena were mitigated for 18Cr-20Ni-5Si steel. In some cases oxide films could not be a corrosion barrier in liquid lead-bismuth.

HIGH TEMPERATURE TENSILE PROPERTIES OF NEW FE-CR-MN DEVELOPED STEEL

OpenAIRE

M. Mahmoudiniya; Sh. Kheirandish; M. Asadi Asadabad

2017-01-01

Nowadays, Ni-free austenitic stainless steels are being developed rapidly and high price of nickel is one of the most important motivations for this development. At present research a new FeCrMn steel was designed and produced based on Fe-Cr-Mn-C system. Comparative studies on microstructure and high temperature mechanical properties of  new steel and AISI 316 steel were done. The results showed that new FeCrMn developed steel has single austenite phase microstructure, and its tensile st...

Creep and time to rupture of a 16/16 Cr Ni Steel

International Nuclear Information System (INIS)

Solano, R.; Garcia, R.; Bohm, H.; Schirra, M.

1972-01-01

The influence of different thermal-mechanical treatments on the creep and time to rupture of a 16/16 Cr.Ni steel is studied. The solution treated material after annealing at 700-800 degree centigree did not affect time to rupture. At the contrary a 12% cold-working and annealing at 800 degree centigree improve the time to rupture. This treatment is preserved up to 700 degree centigree 10 4 hours. The ductility is not strongly affected. A metallographic study of the fracture was carried out. (Author) 23 refs

Electrochemical Behavior and Hydrophobic Properties of CrN and CrNiN Coatings in Simulated Proton Exchange Membrane Fuel Cell Environment

Directory of Open Access Journals (Sweden)

JIN Jie

2016-10-01

Full Text Available The CrN and CrNiN coatings were prepared on the surface of 304 stainless steel by closed field unbalanced magnetron sputtering.X ray diffraction and field emission scanning electron microscopy were used to characterize the structure and morphology of the coatings.The electrochemical corrosion properties under the simulated proton exchange membrane fuel cell(PEMFC environment, interfacial contact resistance and hydrophobic properties of the two kinds of different coatings were investigated by electrochemical methods,contact resistance test and hydrophobic test,respectively.The results indicate that CrN coating mainly consists of CrN and Cr2N phase,CrN and Cr2N phases in the CrNiN coating are less compared to CrN film, and Ni exist as element in CrNiN coating; dynamic polarization tests show the coating is of better corrosion resistance,whereas the corrosion resistance of CrNiN coating is worse than that of CrN coating,constant potential polarization test shows the corrosion current density of CrN and CrNiN coatings are equivalent; CrN and CrNiN coatings significantly reduce the interfacial contact resistance of the 304 stainless steel,among which CrN coating has the smallest contact resistance; and CrNiN coating which has better hydrophobicity than that of CrN coating is more beneficial for the water management in proton exchange membrane fuel cell.

Precipitation in 20 Cr-25 Ni type stainless steel irradiated at low temperatures in a thermal reactor (AGR)

International Nuclear Information System (INIS)

Taylor, C.

1983-01-01

The effects of irradiation on the microstructure of AGR fuel rod cladding have been studied by analytical electron microscopy. Two alloys were investigated, the standard 20 Cr-25 Ni steel stabilised with Nb and a variant containing less Nb but strengthened with a dispersion of TiN precipitates. Irradiation at 360 deg C to 480 deg C produced (Ni, Si)-rich precipitates in both alloys; additionally the standard alloy contained (Ni, Nb, Si)-rich precipitates when irradiated at 440 deg C to 640 deg C. While similar features have been observed in other austenitic stainless steels irradiated in fast reactors, where the lattice-damage rate is greater than in a thermal reactor, their formation is not predicted by isothermal equilibrium diagrams. It is suggested here that the phases are irradiation-induced and that the total displacement damage is the controlling factor. Cladding solution-treated above 1050 deg C then irradiated at 2 -based reactor coolant occurred in cladding with low levels of cold-work at the outer surface, also resulting in Cr-rich carbide formation. (author)

Reformed austenite transformation during fatigue crack propagation of 13%Cr-4%Ni stainless steel

Energy Technology Data Exchange (ETDEWEB)

Thibault, Denis, E-mail: thibault.denis@ireq.ca [Institut de recherche d' Hydro-Quebec (IREQ), 1800, boul. Lionel-Boulet, Varennes, Quebec, J3X 1S1 (Canada); Bocher, Philippe, E-mail: philippe.bocher@etsmtl.ca [Ecole de technologie superieure, 1100, rue Notre-Dame Ouest, Montreal, Quebec, H3C 1K3 (Canada); Thomas, Marc, E-mail: marc.thomas@etsmtl.ca [Ecole de technologie superieure, 1100, rue Notre-Dame Ouest, Montreal, Quebec, H3C 1K3 (Canada); Lanteigne, Jacques, E-mail: lanteigne.jacques@ireq.ca [Institut de recherche d' Hydro-Quebec (IREQ), 1800, boul. Lionel-Boulet, Varennes, Quebec, J3X 1S1 (Canada); Hovington, Pierre, E-mail: hovington.pierre@ireq.ca [Institut de recherche d' Hydro-Quebec (IREQ), 1800, boul. Lionel-Boulet, Varennes, Quebec, J3X 1S1 (Canada); Robichaud, Patrice, E-mail: patrice.robichaud@riotinto.com [Centre de recherche et de developpement Arvida (CRDA), 1955, boul. Mellon, Jonquiere, Quebec, G7S 4K8 (Canada)

2011-08-15

Highlights: {yields} Reformed austenite in 13%Cr-4%Ni stainless steel transforms during fatigue crack growth. {yields} Low cycle fatigue tests showed that this transformation to martensite is gradual. {yields} XRD spectrums obtained on the fracture surface and have been correlated to LCF results. - Abstract: In the as-quenched state, 13%Cr-4%Ni martensitic stainless steels are essentially 100% martensitic. However, a certain amount of austenite is formed during the tempering of this alloy. This reformed austenite is thermally stable at room temperature but can transform to martensite under stress. This transformation is known to happen during impact testing but it has never been established if it occurs during fatigue crack propagation. This study presents the results of X-ray diffraction measurements of reformed austenite before and after crack growth testing. It has been found that reformed austenite does transform to martensite at the crack tip and that this transformation occurs even at a low stress intensity factor. Low-cycle fatigue tests were conducted to verify austenite transformation under cyclic straining. It was found that reformed austenite transforms only partially during the first strain reversal but that essentially all austenite has disappeared after 100 cycles. The relation between austenite transformation under low-cycle fatigue and its transformation during crack growth is also discussed.

Reformed austenite transformation during fatigue crack propagation of 13%Cr-4%Ni stainless steel

International Nuclear Information System (INIS)

Thibault, Denis; Bocher, Philippe; Thomas, Marc; Lanteigne, Jacques; Hovington, Pierre; Robichaud, Patrice

2011-01-01

Highlights: → Reformed austenite in 13%Cr-4%Ni stainless steel transforms during fatigue crack growth. → Low cycle fatigue tests showed that this transformation to martensite is gradual. → XRD spectrums obtained on the fracture surface and have been correlated to LCF results. - Abstract: In the as-quenched state, 13%Cr-4%Ni martensitic stainless steels are essentially 100% martensitic. However, a certain amount of austenite is formed during the tempering of this alloy. This reformed austenite is thermally stable at room temperature but can transform to martensite under stress. This transformation is known to happen during impact testing but it has never been established if it occurs during fatigue crack propagation. This study presents the results of X-ray diffraction measurements of reformed austenite before and after crack growth testing. It has been found that reformed austenite does transform to martensite at the crack tip and that this transformation occurs even at a low stress intensity factor. Low-cycle fatigue tests were conducted to verify austenite transformation under cyclic straining. It was found that reformed austenite transforms only partially during the first strain reversal but that essentially all austenite has disappeared after 100 cycles. The relation between austenite transformation under low-cycle fatigue and its transformation during crack growth is also discussed.

Tensile strength and creep behaviour of austenitic stainless steel type 18Cr - 12Ni with niobium additions at 700{sup 0}C

Energy Technology Data Exchange (ETDEWEB)

Sordi, V L; Bueno, L O, E-mail: sordi@ufscar.b [Federal University of Sao Carlos, Materials Engineering Department, Sao Carlos (SP), 13565-905 (Brazil)

2010-07-01

The effect of niobium additions up to 2.36 wt% on the creep behavior of a series of seven extra low carbon 18Cr-12Ni austenitic stainless steels at 700{sup 0}C has been investigated. Grain size and hardness measurements, hot tensile tests and constant stress creep tests from 90 to 180 MPa were carried out for each alloy, in the solution treated condition at 1050, 1200 and 1300{sup 0}C followed by quench in water. The mechanical behavior at high temperature was related to the amount of NbC precipitation occurring during the tests. Solid solution and intermetallic compound effects were also considered. Creep data analysis was done to determine the parameters of the creep power-law equation {epsilon}-dot = A.{sigma}{sup n} and the Monkman-Grant relation {epsilon}-dot .t{sup m}{sub R} = K. Niobium-carbide precipitation in these steels reduces the secondary stage dependence of strain rate with applied stress, resulting in n-values which indicate the possibility of operation of various creep mechanisms. The creep strength during the secondary stage is primarily controlled by the amount of NbC available for precipitation. However, the rupture times increase progressively with niobium content, as the amount of undissolved carbide particles in grain boundaries and the Laves phase precipitation increase.

Diffusion bonding of 9Cr ODS ferritic/martensitic steel with a phase transformation

Energy Technology Data Exchange (ETDEWEB)

Noh, Sanghoon, E-mail: shnoh@kaeri.re.kr [Nuclear Materials Division, Korea Atomic Energy Research Institute, Yuseong-gu, Daejeon (Korea, Republic of); Kimura, Akihiko [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto (Japan); Kim, Tae Kyu [Nuclear Materials Division, Korea Atomic Energy Research Institute, Yuseong-gu, Daejeon (Korea, Republic of)

2014-10-15

Highlights: • Diffusion bonding was employed to join 9Cr oxide dispersion strengthened ferritic/martensitic steel under uniaxial hydrostatic pressure, and the microstructure and tensile properties of the joints were investigated. • ODS steel was successfully diffusion bonded at an austenization temperature to migrate a residual diffusion bonding interface. • The tensile properties of the joint region were comparable with that of the base metal with a ductile fracture occurred far from the bonding interface. • It is considered that diffusion bonding with a phase transformation can be a very useful joining method for fabricating components in next-generation nuclear systems using 9Cr ODS ferritic/martensitic steel. - Abstract: Diffusion bonding was employed to join oxide-dispersion-strengthened ferritic/martensitic steel under uniaxial hydrostatic pressure using a high vacuum hot press, and the microstructure and tensile properties of the joints were investigated. 9Cr oxide dispersion strengthened (ODS) steel was successfully diffusion bonded at 1150 °C for 1 h to migrate a residual bonding interface. Following heat treatment, including normalising at 1050 °C and tempering at 800 °C for 1 h, comparable results without inclusions or micro-voids at the bonding interface, or degradation in the base metal were achieved. Transmission electron microscopy (TEM) observation revealed that the nano-oxide particles in the bonding region were uniformly distributed in the matrix. At room temperature, the joint had nearly the same tensile properties with that of the base metal. The tensile strength of the joint region at elevated temperatures was comparable with that of the base metal. The total elongation of the joint region decreased slightly, but reached 80% of the base metal at 700 °C, and a ductile fracture occurred far from the bonding interface. Therefore, it is considered that diffusion bonding with a phase transformation can be a very useful joining method for

Observations of copper clustering in a 25Cr-7Ni super duplex stainless steel during low-temperature aging under load

Science.gov (United States)

Thuvander, M.; Zhou, J.; Odqvist, J.; Hertzman, S.; Hedström, P.

2012-07-01

Atom-probe tomography was used to investigate phase separation and copper (Cu) clustering in the ferrite phase of a 25Cr-7Ni super duplex stainless steel. The steel was subjected to a tensile load during aging at 325°C for 5800 h. The degree of phase separation into α (Fe-rich) and α‧ (Cr-rich) was small, but still, it was the highest in the steel subjected to the highest load. Cu was found to cluster, and the number density of clusters increased with increasing load. In the material subjected to the highest load, Cu was enriched in regions that were neither Fe-rich nor Cr-rich. These regions also had the highest number density of Cu clusters.

Influence of Z-phase on long-term creep stability of martensitic 9-12%Cr steels

Energy Technology Data Exchange (ETDEWEB)

Hald, J. [DONG Energy (Denmark)]|[Vattenfall Europe AG, Berlin (Germany)]|[DTU Mechanical Engineering (Denmark); Danielsen, H.K. [DTU Mechanical Engineering (Denmark)

2008-07-01

The long-term creep strength of the new generation of martensitic creep resistant 9- 12% Cr steels since the well-known steel Grade 91 relies strongly on particle strengthening by fine MN nitrides based on V and Nb. During long-term hightemperature exposures the MN nitrides may be replaced by the thermodynamically more stable Z-phases (Cr(V,Nb)N) causing a breakdown in creep strength. Cr contents above 10.5% strongly accelerate Z-phase precipitation, which explains the lack of success for all attempts to develop martensitic creep resistant steels with high Cr content for oxidation protection. The Z-phase nucleation process by Cr-diffusion into pre-existing MN nitrides is rate controlling for the Z-phase transformation. More work is needed before effects of chemical composition on the nucleation process can be reliably modeled. Careful control of the Z-phase precipitation process has led to the design of experimental 12%Cr martensitic steels strengthened by Z-phase. Such steels may again enable the combination of high strength and oxidation resistance in the same alloy. This opens a new pathway for further alloy development of the heat resistant martensitic steels. (orig.)

Dissolution and oxidation behaviour of various austenitic steels and Ni rich alloys in lead-bismuth eutectic at 520 °C

Energy Technology Data Exchange (ETDEWEB)

Roy, Marion, E-mail: marion.roy@cea.fr [CEA, DEN, DPC, SCCME, Laboratoire d’Etude de la Corrosion Non Aqueuse, F-91191 Gif-sur-Yvette (France); Martinelli, Laure, E-mail: laure.martinelli@cea.fr [CEA, DEN, DPC, SCCME, Laboratoire d’Etude de la Corrosion Non Aqueuse, F-91191 Gif-sur-Yvette (France); Ginestar, Kevin, E-mail: kevin.ginestar@cea.fr [CEA, DEN, DPC, SCCME, Laboratoire d’Etude de la Corrosion Non Aqueuse, F-91191 Gif-sur-Yvette (France); Favergeon, Jérôme, E-mail: jerome.favergeon@utc.fr [Laboratoire Roberval, UMR 7337, Université de Technologie de Compiègne, Centre de Recherche de Royallieu, CS 60319, 60203 Compiègne Cedex (France); Moulin, Gérard [Laboratoire Roberval, UMR 7337, Université de Technologie de Compiègne, Centre de Recherche de Royallieu, CS 60319, 60203 Compiègne Cedex (France)

2016-01-15

Ten austenitic steels and Ni rich alloys were tested in static lead-bismuth eutectic (LBE) at 520 °C in order to obtain a selection of austenitic steels having promising corrosion behaviour in LBE. A test of 1850 h was carried out with a dissolved oxygen concentration between 10{sup −9} and 5 10{sup −4} g kg{sup −1}. The combination of thermodynamic of the studied system and literature results leads to the determination of an expression of the dissolved oxygen content in LBE as a function of temperature: RT(K)ln[O](wt%) = −57584/T(K) −55.876T(K) + 254546 (R is the gas constant in J mol{sup −1} K{sup −1}). This relation can be considered as a threshold of oxygen content above which only oxidation is observed on the AISI 316L and AISI 304L austenitic alloys in static LBE between 400 °C and 600 °C. The oxygen content during the test leads to both dissolution and oxidation of the samples during the first 190 h and leads to pure oxidation for the rest of the test. Results of mixed oxidation and dissolution test showed that only four types of corrosion behaviour were observed: usual austenitic steels and Ni rich alloys behaviour including the reference alloy 17Cr-12Ni-2.5Mo (AISI 316LN), the 20Cr-31Ni alloy one, the Si containing alloy one and the Al containing alloy one. According to the proposed criteria of oxidation and dissolution kinetics, silicon rich alloys and aluminum rich alloy presented a promising corrosion behaviour. - Highlights: • 10 austenitic steels and Ni rich alloys were tested in LBE at 520 °C with dissolved oxygen content between 10{sup -9} and 5 10{sup -4} wt%. • It is shown that only thermodynamics cannot explain the Ni rich alloys corrosion behaviour in LBE. • The role of oxygen on corrosion behaviour in LBE was highlighted. • An equilibrium line was defined above which only oxidation has occurred on 316L: RTln[O](wt%) = -57584/T(K)-55.876T(K)+254546. • 18Cr-15Ni-3.7Si, 21Cr-11Ni-1.6Si and 14Cr-25Ni-3.5Al

Silicon coating treatment to improve high temperature corrosion resistance of 9%Cr steels

International Nuclear Information System (INIS)

Hill, M.P.

1989-01-01

A silicon coating process is described which confers good protection on 9%Cr steels and alloys in CO 2 based atmospheres at high temperatures and pressures. The coatings are formed by decomposition of silane at temperatures above 720 K. Protective layers are typically up to 1 μm thick. The optimum coating conditions are discussed. The chemical state of the coatings has been investigated by X-ray photoelectron spectroscopy and has demonstrated the importance of avoiding silicon oxide formation during processing. Corrosion testing has been carried out for extended periods, up to 20 000 h, at temperatures between 753 and 853 K, in a simulated advanced gas cooled reactor gas at 4 MPa pressure. Benefit factors of up to 60 times have been measured for 9%Cr steels. Even higher values have been measured for 9Cr-Fe binary alloy on which a 1 μm coating was sufficient to eliminate significant oxidation over 19 000 h except at the specimen edges. The mechanism of protection is discussed. It is suggested that a silicon surface coating for protecting steels from high temperature corrosion has some advantages over adding silicon to the bulk metal. (author)

Effect of nitrogen alloying of stainless steels on their corrosion stability

International Nuclear Information System (INIS)

Chigal, V.; Knyazheva, V.M.; Pitter, Ya.; Babich, S.G.; Bogolyubskij, S.D.

1986-01-01

Results of corrosion tests and structural investigations of 03Cr18Ni10 and 03Cr18Ni10Mo3 steels without nitrogen and with nitrogen content of 0.15-0.3% are presented. Corrosion-electrochemical behaviour of Cr20Ni20 steel with ultralow carbon content (0.004-0.006%) and nitrogen content with 0-0.5% as well as Cr 2 N nitride behaviour are investigated. A conclusion is made on nitrogen and excessive nitride phase effect on corrosion stability of steel in corrosive media with different reduction-oxidation properties

Reversed austenite in 0Cr13Ni4Mo martensitic stainless steels

Energy Technology Data Exchange (ETDEWEB)

Song, Y.Y., E-mail: songyuanyuan@imr.ac.cn [Institute of Metal Research, Chinese Academy of Science, Shenyang 110016 (China); Li, X.Y.; Rong, L.J.; Li, Y.Y. [Institute of Metal Research, Chinese Academy of Science, Shenyang 110016 (China); Nagai, T. [National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047 (Japan)

2014-01-15

The austenite reversion process and the distribution of carbon and other alloying elements during tempering in 0Cr13Ni4Mo martensitic stainless steel have been investigated by in-situ high temperature X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The microstructure of the reversed austenite was characterized using transmission electron microscopy (TEM). The results revealed that the amount of the reversed austenite formed at high temperature increased with the holding time. Direct experimental evidence supported carbon partitioning to carbides and Ni to the reversed austenite. The reversed austenite almost always nucleated in contact with lath boundary M{sub 23}C{sub 6} carbides during tempering and the diffusion of Ni promoted its growth. The Ni enrichment and the ultrafine size of the reversed austenite were considered to be the main factors that accounted for the stability of the reversed austenite. - Highlights: • The amount of the reversed austenite formed at high temperature increases with the holding time. • STEM results directly show that carbon is mainly partitioned into the carbides and Ni into the reversed austenite. • The Ni enrichment and the ultrafine size are the main factors leading to the stabilization of the reversed austenite.

PLASTIC DEFORMATION ON THE MACHINED SURFACE OF STEEL Cr20Ni10MoTi AT DRILLING

Directory of Open Access Journals (Sweden)

Jozef Jurko

2009-07-01

Full Text Available Information about material machinability is very important for the machining technology. Precise and reliable information on the machinability of a material before it enters the machining process is a necessity, and this brings the verification of technological methods in practice. This article presents the conclusions of machinability tests on austenitic stainless steel according to EN-EU (ISO: steel Cr20Ni10MoTi. This article presents the conclusions of VEGA grant agency at the Ministry of Education SR for supporting research work and co-financing the projects: Grant work #01/3173/2006 with the title „Experimental investigation of cutting zones in drilled and milled stainless steels

Creep-fatigue evaluation method for modified 9Cr-1Mo steel

International Nuclear Information System (INIS)

Wada, Y.; Aoto, K.

1997-01-01

As creep-fatigue evaluation methods on normalized and tempered Modified 9Cr-1Mo steel for design use, the time fraction rule and the simplified conventional ductility exhaustion rule are investigated for the prediction of tension strain hold creep-fatigue damage of this material. For the above investigation, stress relaxation behaviour during strain hold has to be analyzed using stress-strain-time relation. The initial value of stress relaxation was determined by cyclic stress-strain curves in continuous cycling fatigue tests. Cyclic stress-strain behaviour of Mod.9Cr-1Mo(NT) steel is different from that of austenitic stainless steels, so this effect was considered. Stress relaxation analysis was performed using static creep strain-time relation and conventional hardening rule. The time fraction by using the above stress relaxation analysis results can give good prediction for creep-fatigue life of Mod.9Cr-1Mo(NT) steel. For design use it is practical to be able to estimate creep damages conservatively by both strain behaviour of cyclic plastic (in continuous cycling fatigue tests) and monotonic creep (in standard creep tests). The life reduction by strain hold at the minimum peak of compressive stress in creep-fatigue tests was examined, and this effects can be evaluated by the relationship between the location of oxidation and the effective deformation at crack tip. In an accelerated oxidation environment, for example in high temperature and high pressure steam, a different approach for life reduction should be developed based on the mechanism of growth of oxide and crack growth with oxidation. However, in the creep damage dominant region, its effect is saturated and the effect of cavity growth along grain boundary becomes dominant for long-term strain hold in the high temperature conditions. (author). 6 refs, 6 figs

Microstructural evolution in 13Cr-8Ni-2.5Mo-2Al martensitic precipitation-hardened stainless steel

International Nuclear Information System (INIS)

Ping, D.H.; Ohnuma, M.; Hirakawa, Y.; Kadoya, Y.; Hono, K.

2005-01-01

The microstructure of 13Cr-8Ni-2.5Mo-2Al martensitic precipitation-hardened (PH) stainless steel has been investigated using transmission electron microscopy, three-dimensional atom probe and small-angle X-ray scattering. A high number density (∼10 23-25 m -3 ) of ultra-fine (1-6 nm) β-NiAl precipitates are formed during aging at 450-620 deg. C, which are spherical in shape and dispersed uniformly with perfect coherency with the matrix. As the annealing temperature increases, the size and concentration of the precipitates increase concurrently while the number density decreases. The Mo and Cr segregation to the precipitate-matrix interface has been detected and is suggested to suppress precipitate coarsening. In the sample aged for 500 h at 450 deg. C, the matrix decomposes into Cr-rich (α') and Cr-poor (α) regions. The decrease in the strength at higher temperature (above 550 deg. C) is attributed to the formation of larger carbides and reverted austenite

Comparative studies on ultrasonic, friction, laser and resistance pressure welding of NiTi shape memory alloys with high-alloy steels. Final report; Vergleichende Untersuchungen zum Ultraschall-, Reib-, Laserstrahl- und Widerstandspressschweissen von NiTi-Shape-Memory-Metall mit hochlegierten Staehlen. Abschlussbericht

Energy Technology Data Exchange (ETDEWEB)

Zuckschwerdt, K.

2000-04-01

The suitability of different welding techniques for welding of NiTi shape memory alloys with high-alloy steel (C12CrNi17-7, X5CrNiNb19-9, X20Cr13) was investigated. The quality of the welds was analyzed using mechanical-technological, fractographic, metallographic and electron microscopy analysis. [German] Ziel dieses Forschungsvorhabens ist es, die Eignung der einzelnen Schweissverfahren fuer das Fuegen von NiTi-Formgedaechtnislegierungen mit hochlegiertem Stahl (X12CrNi17-7, X5CrNiNb19-9, X20Cr13) darzustellen und zu beurteilen. Die Qualitaet der Fuegeverbindungen wird mit Hilfe mechanisch-technologischer, fraktographischer, metallographischer und elektronenmikroskopischer Untersuchungen bewertet.

High Temperature Behavior of Cr3C2-NiCr Coatings in the Actual Coal-Fired Boiler Environment

Science.gov (United States)

Bhatia, Rakesh; Sidhu, Hazoor Singh; Sidhu, Buta Singh

2015-03-01

Erosion-corrosion is a serious problem observed in steam-powered electricity generation plants, and industrial waste incinerators. In the present study, four compositions of Cr3C2-(Ni-20Cr) alloy coating powder were deposited by high-velocity oxy-fuel spray technique on T-91 boiler tube steel. The cyclic studies were performed in a coal-fired boiler at 1123 K ± 10 K (850 °C ± 10 °C). X-ray diffraction, scanning electron microscopy/energy dispersive X-ray analysis and elemental mapping analysis techniques were used to analyze the corrosion products. All the coatings deposited on T-91 boiler tube steel imparted hot corrosion resistance. The 65 pctCr3C2 -35 pct (Ni-20Cr)-coated T-91 steel sample performed better than all other coated samples in the given environment.

Creep strength and microstructural evolution of 9-12% Cr heat resistant steels during creep exposure at 600 C and 650 C

Energy Technology Data Exchange (ETDEWEB)

Mendez Martin, Francisca [Graz Univ. of Technology (Austria). Inst. for Materials Science and Welding; Panait, Clara Gabriela [MINES ParisTech, UMR CNRS, Evry (France). Centre des Materiaux; V et M France CEV, Aulnoye-Aymeries (France); Bendick, Walter [Salzgitter Mannesmann Forschung GmbH (SZMF), Duisburg (DE)] (and others)

2010-07-01

9-12% Cr heat resistant steels are used for applications at high temperatures and pressures in steam power plants. 12% Cr steels show higher creep strength and higher corrosion resistance compared to 9% Cr steels for short term creep exposure. However, the higher creep strength of 12 %Cr steels drops increasingly after 10,000-20,000 h of creep. This is probably due to a microstructural instability such as the precipitation of new phases (e.g. Laves phases and Z-phases), the growth of the precipitates and the recovery of the matrix. 9% Cr and 12% Cr tempered martensitic steels that have been creep tested for times up to 50,000 h at 600 C and 650 C were investigated using Transmission Electron Microscopy (TEM) on extractive replicas and thin foils together with Backscatter Scanning Electron Microscopy (BSE-SEM) to better understand the different creep behaviour of the two different steels. A significant precipitation of Laves phase and low amounts of Z-phase was observed in the 9% Cr steels after long-term creep exposure. The size distribution of Laves phases was measured by image analysis of SEM-BSE images. In the 12% Cr steel two new phases were identified, Laves phase and Z-phase after almost 30,000 h of creep test. The quantification of the different precipitated phases was studied. (orig.)

Soft-martensitic stainless Cr-Ni-Mo steel for turbine rotors in geothermic power stations

International Nuclear Information System (INIS)

Schonfeld, K.; Potthast, E.

1986-01-01

Steel Grade X5 Cr-Ni-Mo 12 6 containing 0.05% carbon, 12% chromium, 6% nickel, and 1.50% molybdenum is an advantageous material for turbine rotors in geothermic power stations because of its excellent strength and toughness properties in combination with good erosion and corrosion resistance. In terms of the phase diagram, this soft-martensitic steel has its place at the martensite/austenite/ferrite interface. Therefore, its chemical composition must be chosen so as to have a completely martensitic structure after hardening. The manufacture of and the mechanical properties of a turbine rotor 1200 mm in diameter by 5600 mm in length with a finished weight of approximately 21.5 tons are described in detail

Comparison of mechanical behavior of TiN, TiNC, CrN/TiNC, TiN/TiNC films on 9Cr18 steel by PVD

Science.gov (United States)

Feng, Xingguo; Zhang, Yanshuai; Hu, Hanjun; Zheng, Yugang; Zhang, Kaifeng; Zhou, Hui

2017-11-01

TiN, TiNC, CrN/TiNC and TiN/TiNC films were deposited on 9Cr18 steel using magnetron sputtering technique. The morphology, composition, chemical state and crystalline structure of the films were observed and analyzed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Hardness and adhesion force were tested by nanoindentation and scratch tester, respectively. The friction and wear behavior of TiN, TiNC, CrN/TiNC and TiN/TiNC films sliding against GCr15 balls were investigated and compared synthetically using ball-on-disk tribometer. It was found that Tisbnd N, Tisbnd C, Tisbnd Nsbnd C and Csbnd C bonds were formed. The TiN/TiNC film was composed of TiN, TiC and TiNC phases. Hardness and adhesion force results indicated that although the TiN film possessed the highest hardness, its adhesion force was lowest among all the films. Tribological test results showed that the friction coefficient of TiN/TiNC was much lower than that of TiN and the wear rate decreases remarkably from 2.3 × 10-15 m3/Nm to 7.1 × 10-16 m3/Nm, which indicated the TiN/TiNC film has better wear resistance.

Segmentation of 9Cr Steel Samples based on Composition and Mechanical Property

Science.gov (United States)

Krishnamurthy, Narayanan; Maddali, Siddharth; Vyacheslav, Romanov; Hawk, Jeffrey

Data mining approaches were used to look at composition-process-property linkage in 9Cr steel. We present results of cluster identification using 7 principal composition elements and analyze its significance with respect to mechanical tensile properties. Data set comprises 82 compositional variants of 9Cr steel whose Cr weight fraction ranges 8-13%. The alloys underwent heat treatments (homogenization, normalization, and 1 to 3 tempering cycles) and were tested for tensile and creep properties at room temperature and elevated temperatures (427/800 oC median/max). In this study, alloys were partitioned into groups, and their mechanical properties were analyzed for significant differences across groups. Normalized weight fractions were used to delineate groups of alloys. Partitioning Around Medoids (PAM) clustering was used, with dissimilarities instead of distance metrics. Dataset of 21 chemical components, with Fe being the majority component, followed by Cr and C. Major contributors of composition to PAM clustering were obtained from PCA scores. Mean ultimate tensile strength of segmented groups of alloys was analyzed with ANOVA & Tukey HSD tests to identify the final 3 groups based on composition and mechanical property.

Creep and Oxidation Behavior of Modified CF8C-Plus with W, Cu, Ni, and Cr

Science.gov (United States)

Unocic, Kinga A.; Dryepondt, Sebastien; Yamamoto, Yukinori; Maziasz, Philip J.

2016-04-01

The microstructures of modified CF8C-Plus (Fe-19Cr-12Ni-0.4W-3.8Mn-0.2Mo-0.6Nb-0.5Si-0.9C) with W and Cu (CF8CPWCu) and CF8CPWCu enhanced with 21Cr + 15Ni or 22Cr + 17.5Ni were characterized in the as-cast condition and after creep testing. When imaged at lower magnifications, the as-cast microstructure was similar among all three alloys as they all contained a Nb-rich interdendritic phase and Mn-based inclusions. Transmission electron microscopy (TEM) analysis showed the presence of nanoscale Cu-rich nanoprecipitates distributed uniformly throughout the matrix of CF8CPWCu, whereas in CF8CPWCu22/17, Cu precipitates were found primarily at the grain boundaries. The presence of these nanoscale Cu-rich particles, in addition to W-rich Cr23C6, nanoscale Nb carbides, and Z-phase (Nb2Cr2N2), improved the creep strength of the CF8CPWCu steel. Modification of CF8CPWCu with Cr and Ni contents slightly decreased the creep strength but significantly improved the oxidation behavior at 1073 K (800 °C). In particular, the addition of 22Cr and 17.5Ni strongly enhanced the oxidation resistance of the stainless steel resulting in a 100 degrees or greater temperature improvement, and this composition provided the best balance between improving both mechanical properties and oxidation resistance.

The thermal fatigue behaviour of creep-resistant Ni-Cr cast steel

Directory of Open Access Journals (Sweden)

B. Piekarski

2007-12-01

Full Text Available The study gives a summary of the results of industrial and laboratory investigations regarding an assessment of the thermal fatigue behaviour of creep-resistant austenitic cast steel. The first part of the study was devoted to the problem of textural stresses forming in castings during service, indicating them as a cause of crack formation and propagation. Stresses are forming in carbides and in matrix surrounding these carbides due to considerable differences in the values of the coefficients of thermal expansion of these phases. The second part of the study shows the results of investigations carried out to assess the effect of carbon, chromium and nickel on crack resistance of austenitic cast steel. As a criterion of assessment the amount and propagation rate of cracks forming in the specimens as a result of rapid heating followed by cooling in running water was adopted. Tests were carried out on specimens made from 11 alloys. The chemical composition of these alloys was comprised in a range of the following values: (wt-%: 18-40 %Ni, 17-30 %Cr, 1.2-1.6%Si and 0.05-0.6 %C. The specimens were subjected to 75 cycles of heating to a temperature of 900oC followed by cooling in running water. After every 15 cycles the number of the cracks was counted and their length was measured. The results of the measurements were mathematically processed. It has been proved that the main factor responsible for an increase in the number of cracks is carbon content in the alloy. In general assessment of the results of investigations, the predominant role of carbon and of chromium in the next place in shaping the crack behaviour of creep-resistant austenitic cast steel should be stressed. Attention was also drawn to the effect of high-temperature corrosion as a factor definitely deteriorating the cast steel resistance to thermal fatigue.

The influence of heat treatment and process parameters optimization on hardness and corrosion properties of laser alloyed X12CrNiMo steel

CSIR Research Space (South Africa)

Popoola, API

2016-10-01

Full Text Available Martensitic stainless steels are used in the production of steam turbine blades but their application is limited due to low hardness and poor corrosion resistance. Laser surface alloying and heat treatment of X12CrNiMo Martensitic stainless steel...

Boundary and sub-boundary hardening in tempered martensitic 9Cr steel during long-term creep at 650 C

Energy Technology Data Exchange (ETDEWEB)

Abe, Fujio [National Institute for Materials Science, Sengen, Tsukuba (Japan)

2010-07-01

The boundary and sub-boundary hardening is shown to be the most important strengthening mechanism in creep of the 9% Cr steel base metal and welded joints. The addition of boron reduces the coarsening rate of M{sub 23}C{sub 6} carbides along boundaries near prior austenite grain boundaries during creep, enhancing the boundary and sub-boundary hardening. This improves long-term creep strength of base metal. The enhancement of boundary and sub-boundary hardening is significantly reduced in fine-grained region of Ac{sub 3} HAZ simulated specimens of conventional steel P92. In NIMS 9Cr boron steel welded joints, the grain size and distribution of carbonitrides are substantially the same between the HAZ and base metal, where fine carbonitrides are distributed along the lath and block boundaries as well as along prior austenite grain boundaries. This is essential for the suppression of Type IV fracture in NIMS 9% Cr boron steel welded joints. Newly alloy-designed 9Cr steel with 160 ppm boron and 85 ppm nitrogen exhibits much higher creep rupture strength of base metal than P92 and also no Tpe-IV fracture in welded joints at 650 C. (orig.)

Interfacial microstructure and performance of brazed diamond grits with Ni-Cr-P alloy

Energy Technology Data Exchange (ETDEWEB)

Wang, C.Y. [Faculty of Mechanical and Electronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China)], E-mail: cywang@gdut.edu.cn; Zhou, Y.M.; Zhang, F.L.; Xu, Z.C. [Faculty of Mechanical and Electronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China)

2009-05-12

The reaction mechanism of the interface among diamond, commercial Ni-Cr-P alloy and steel substrate has been studied by optical microscopy, scanning electron microscope, X-ray diffraction and Raman spectroscopy. The reaction layers formed among diamond, brazing alloy and steel substrate produced good wettability of diamond grits for achieving better quality tools. The reaction layer between diamond and brazing alloy comprised a reaction layer of brazing alloy and a reaction layer of diamond. Cr{sub 7}C{sub 3} and Cr{sub 3}C{sub 2} formed in the reaction layer of brazing alloy was the main reason for improving the bonding strength of Ni-Cr alloy to the diamond grits. A reaction layer of diamond may be a graphitization layer formed on the surface of diamond under high temperature brazing. The reaction layer of brazing alloy and steel substrate was the co-diffusion of Ni, Cr and Fe between the brazing alloy and the steel substrate. The life and sharpness of brazed diamond boring drill bits fabricated in this study were superior to the electroplated one in the market owing to its high protrusion and bonding strength.

Hydrogen effect on different melts of steel 03Cr10Ni10Mo2(Ti,Al)

International Nuclear Information System (INIS)

Hruby, J.; Novosad, P.; Axamit, R.

1984-01-01

The effect of hydrogen on martensitic 03Cr10Ni10Mo2(Ti,Al) steel was studied following vacuum induction melting and electroslag remelting with and without the effect of radiation. Under the influence of hydrogen and under the same parameters of catodic hydrogen charging of steel after vacuum induction melting shows a 20 - 30% reduction in total ductility. Steels after electroslag remelting show a higher reduction in total ductility - within the range of 26 - 33%, i.e., 33 - 43% for different melts, and contraction Z shows a reduction of 23 - 59%. Electroslag remelted steels show a greater reduction in plasticity owing to hydrogen than steels melted in vacuum induction furnaces. The reduction of the yield point and the breaking strength owing to hydrogen are more explicit than in steel after vacuum melting. In non-irradiated hydrogenated samples a higher yield point was evident. (B.S.)

Modelling and characterization of chi-phase grain boundary precipitation during aging of Fe-Cr-Ni-Mo stainless steel

International Nuclear Information System (INIS)

Xu, W.; San Martin, D.; Rivera Diaz del Castillo, P.E.J.; Zwaag, S. van der

2007-01-01

High molybdenum stainless steels may contain the chi-phase precipitate (χ, Fe 36 Cr 12 Mo 10 ) which may lead to undesirable effects on strength, toughness and corrosion resistance. In the present work, specimens of a 12Cr-9Ni-4Mo wt% steel are heat treated at different temperatures and times, and the average particle size and particle size distribution of chi-phase precipitate are studied quantitatively. A computer model based on the KWN framework has been developed to describe the evolution of chi-phase precipitation. The kinetic model takes advantage of the KWN model to describe the precipitate particle size distribution, and is coupled with the thermodynamic software ThermoCalc for calculating the instantaneous local thermodynamic equilibrium condition at the interface and the driving force for nucleation. A modified version of Zener's theory accounting for capillarity effects at early growth stages is implemented in this model. The prediction of the model for chi-phase precipitation at a grain boundary is compared to experimental results and both the average particle size and the particle size distribution are found to be in good agreement with experimental observations at late precipitation stages

An examination of the potential for 9%Cr1%Mo steel as thick section tubeplates in fast reactors

International Nuclear Information System (INIS)

Orr, J.; Sanderson, S.J.

1984-01-01

The steam generator units of future commercial demonstration fast reactors are likely to have a requirement for heavy section tubeplates (up to 500mm thick) with good elevated temperature strength and creep-fatigue resistance. A comparison of the mechanical properties available for ferritic steels has suggested that 9%Cr1%Mo steel would be a strong candidate material for this application. Although this steel is covered in some national specifications for tubes, pipes, plates and forgings and is also well established in the UK nuclear industry, international experience to date is confined to sections less than ca 150mm. The potential of 9%Cr1%Mo steel for use in thick sections has therefore been assessed in the present study by using simulation heat treatments. The work reported here involved the laboratory-scale cooling of bar samples to simulate water-quenching rates in cylindrical sections up to 720mm diameter (ie: equivalent to 500mm thick plate). The tensile properties at ambient and 525 0 C and impact fracture appearance transition temperatures were determined for material tempered after cooling at simulated thick section rates; the transformation characteristics as influenced by the net chromium equivalent were also established. The results of this work show that 9%Cr1%Mo steel may be fully hardened in the equivalent of the section sizes examined,and the mechanical properties of tempered material show only a small reduction from those of thin section normalised and tempered 9%Cr1%Mo steel. These findings support the potential usage of heavy section 9%Cr1%Mo steel envisaged for fast reactor steam generator tubeplates

Mean strain effects on the random cyclic strain-life relations of 0Cr18Ni10Ti pipe steel

International Nuclear Information System (INIS)

Zhao Yongxiang; Yang Bing

2005-01-01

Experimental study is performed on the mean strain effects on the random cyclic strain-life relations of the new nuclear material, 0Cr18Ni10Ti pipe steel. In order to save costs of specimens and tests, an improved maximum likelihood fatigue test method is applied to manage the present strain-controlled fatigue tests. Six straining ratios, respectively, -1, -0.52, 0.22, 0.029, 0.18, and 0.48, are applied to study the effects. Total 104 specimens are fatigued. Since the material exhibits an entirely relaxation effect of mean stress under the six ratios and, in addition, there is no effectively method for the description of the mean straining effects under this case, previous Zhao's random strain-life relations are therefore applied for effective characterization of the scattering test data under the six ratios on a basis of Coffin-Manson equation.Then the effects of the ratios are analyzed respectively on the average fatigue lives, the standard deviations of the logarithms of fatigue lives, and the fatigue lives under different survival probabilities and confidences. The results reveal that the ratios greater than zero exhibit a positive effect of about 1.3 to 1.6 times under the survival probability of 0.999 and the confidence of 95%. A negative effect is exhibited for the case of the ratios less than zero. In addition, the assessment of the effects from the sense of average fatigue lives might result in a wrong conclusion for the practice of higher reliabilities. The effects can be appropriately assessed from a probabilistic sense to take into account the average lives, the scattering regularity of test data, and the size of sampling. (author)

Microstructure and mechanical properties of friction stir welded 9Cr ODS steel

International Nuclear Information System (INIS)

Min, Hyoung Kee; Kang, Suk Hoon; Noh, Sanghoon; Lee, Jung Gu; Jang, Jinsung; Kim, Tae Kyu

2013-01-01

It is well known that the welding of ODS steel with a conventional melting.solidification process is not adequate to reserve nano-oxide particles in the matrix homogeneously. To reserve nano-oxide particles in the matrix homogeneously, friction stir welding (FSW) is the most promising technique to join ODS alloys. In this study, the effects of FSW on the microstructure and mechanical properties of a ODS steel were studied to apply the FSW process to 9Cr ODS steels. Microstructures were observed by means of optical microscopy, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). A tensile test and hardness test were carried out to the investigate mechanical properties. FSW could successfully produce defect-free welds on ODS plates. FSW produced a fine grain structure consisting of ferrite and martensite. Tensile strengths and elongations of the SZs were excellent at 298 K, compared to those of the BM. This study suggests that FSW might be an appropriate welding method of ODS steels. Oxide dispersion strengthened (ODS) ferritic-martensitic (FM) steel containing 9 wt%Cr is a promising candidate material for high temperature components operating in aggressive environments such as nuclear fusion and fission systems because of the excellent elevated temperature strength, corrosion and radiation resistance. These characteristics come from microstructures consisting of fine grains and nano-oxide particles dispersed in high number density. However, for more applications of ODS steel in nuclear systems, its weldability is the one of the barrier to be solved

Comparison of the segregation behavior between tempered martensite and tempered bainite in Ni-Cr-Mo high strength low alloy RPV steel

Energy Technology Data Exchange (ETDEWEB)

Park, Sang Gyu; Kim, Min Chul; Kim, Hyung Jun; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2012-05-15

SA508 Gr.4N Ni-Cr-Mo low alloy steel has an superior fracture toughness and strength, compared to commercial Mn-Mo-Ni low alloy RPV steel SA508 Gr.3. Higher strength and fracture toughness of low alloy steels could be obtained by adding Ni and Cr. So several were performed on researches on SA508 Gr.4N low alloy steel for a RPV application. The operation temperature and term of a reactor pressure vessel is more than 300 .deg. C and over 40 years. Therefore, in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel, the resistance of thermal embrittlement in the high temperature range including temper embrittlement is required. S. Raoul reported that the susceptibility to temper embrittlement was increasing a function of the cooling rate in SA533 steel, which suggests the martensitic microstructures resulting from increased cooling rates are more susceptible to temper embrittlement. However, this result has not been proved yet. So the comparison of temper embrittlement behavior was made between martensitic microstructure and bainitic microstructure with a viewpoint of boundary features in SA508 Gr.4N, which have mixture of tempered bainite/martensite. We have compared temper embrittlement behaviors of SA508 Gr.4N low alloy steel with changing volume fraction of martensite. The mechanical properties of these low alloy steels were evaluated after a long-term heat treatment. Then, the the segregated boundaries were observed and segregation behavior was analyzed by AES. In order to compare the misorientation distributions of model alloys, grain boundary structures were measured with EBSD

Electrochemical impedance spectrometry using 316L steel, hastelloy, maraging, Inconel 600, Elgiloy, carbon steel, TiN and NiCr. Simulation in tritiated water. 2 volumes

International Nuclear Information System (INIS)

Bellanger, G.

1994-03-01

Polarization and electrochemical impedance spectrometry curves are presented and discussed. These curves make it possible to ascertain the corrosion domains and to compare the slow and fast kinetics (voltammetry) of different stainless steel alloys. These corrosion kinetics, the actual or simulated tritiated water redox potentials, and the corrosion potentials provide a classification of the steels studied here: 316L, Hastelloy, Maraging, Inconel 600, Elgiloy, carbon steel and TiN and NiCr deposits. From the results it can be concluded that Hastelloy and Elgiloy have the best corrosion resistance. (author). 49 refs., 695 figs., tabs

Equation of short fatigue crack growth law of 1Cr18Ni9Ti weld metal

International Nuclear Information System (INIS)

Zhao Yongxiang; Yang Bing; Gao Qing

2005-01-01

The method is investigated for characterizing the short fatigue crack (SFC) behaviour of 1Cr18Ni9Ti weld metal by the 'effective short fatigue crack criterion'. Three considerations are given. Firstly, the dominant effective short fatigue crack (DESFC) behaviour is a result of the interaction and evolution of the collective SFCs and, therefore, it is deemed suitable to describe their collective behaviour. Secondly, the significant character of microstructural short crack (MSC) regime and physical short crack (PSC) regime for the behaviour of SFCs indicates that it should be well exhibited in the characterization. Thirdly, the stronger irregular behaviour of SFCs indicates the single parameter of cyclic stress or strain amplitude for representing driving force of DESFC growth may be not appropriated. A new growth law for the collective SFCs is derived from a consideration of the local cyclic strain energy density driving the DESFC initiation in the initial zone and, then, driving the DESFC growth in the zones around its tips. The final form of this law is relative to the total cyclic strain energy density of remote fields, which circle the initial zone and, then, the zones around the DESFC tips. Availability has been indicated by an analysis of the test data of present material. (authors)

Low-temperature cyclic cracking resistance of Fe-Cr-Ni and Fe-Cr-Mn steels welded joints

International Nuclear Information System (INIS)

Ostash, O.P.; Zhmur-Klimenko, V.T.; Yarema, S.Ya.; Yushchenko, K.A.; Strok, L.P.; Belotserkovets, V.I.

1983-01-01

Results of further investigations into regularities of development of low-temperature fatigue fracture of welded oints in 07Kh13G20AN4 steel are presented, they are compared with analogous data traditional cryogenic 0Kh18N10T and 03Kh13AG19 steels. Welded joints have been prepared by means of automatic V-like level arc Welding of plates; 0Kh18N10T and 07Kh13G20AN4 steels have been welded by means of sv-04Kh19N9 wire, 03Kh13AG19 steel-by means of sv-07Kh13AG19 wire. Tests at almost zero (asymmetry coefficient R=0.05) cycle of extension at 15-20 Hz frequency have been conducted on 5 mm thick disk samples at 20 deg C and - 160 deg C according to the given methods. It is shown that by cyclic crack resistance of welded joint zones of 0Kh18N10T steel and chromium-manganese steels at normal temperature the 07Kh13G20AN4 steel exceeds 0Kh18N10T steel, at low temperature it yields to 0Kh18N10T only by fracture toughness of heat affected zones HAZ and weld metal (ne). 07Kh13G20AN4 steel and its welded joints as most hardened and cheap may be a good substituent for 0Kh18N10T steel. Optimization of WM alloying for increase of its cyclic fracture toughness at cryogenic temperatures is necessary

Effect of rare earth element yttrium addition on microstructures and properties of a 21Cr-11Ni austenitic heat-resistant stainless steel

International Nuclear Information System (INIS)

Chen, Lei; Ma, Xiaocong; Wang, Longmei; Ye, Xiaoning

2011-01-01

Research highlights: → Applications of Y in 21Cr-11Ni austenitic heat-resistant stainless steel. → Sensible characteristics of microstructure and properties have been observed. → Y has been found be effective in improving hot ductility of 21Cr-11Ni steel. → Inhibitory effect of Y on S segregation to the grain boundary has been observed. -- Abstract: In this comparative study, the microstructure and the mechanical properties of a 21Cr-11Ni austenitic heat-resistant stainless steel with and without addition of rare earth (RE) element yttrium have been investigated. The results show that a number of fine spherical yttrium-rich oxide particles are not uniformly distributed in the matrix of steel with yttrium; instead, they are aligned along the rolling direction. The grains surrounding the alignment are nearly one order of magnitude smaller than those farther away from the alignment. The approximate calculation results indirectly show that the grain refinement may be mainly attributed to the stimulation for nucleation of recrystallization rather than to pinning by particles. Furthermore, the alignment has resulted in significant loss in transverse impact toughness and tensile elongation at room temperature. There is a trough in the hot ductility-temperature curve, which is located between 973 and 1173 K. The ductility trough of steel with yttrium becomes shallow within a certain temperature range, especially around 1073 K, indicating that improvement on hot ductility is achieved by yttrium addition. The results may be attributed to the increase of grain boundary cohesion indicated by the effective improvement on intergranular failure tendency, and the inhibitory effect of yttrium on sulfur segregation to grain boundaries is believed to be an important cause.

Microstructural characterization of second phases in X10CrMoVNb9-1 and 12CrMoWCuVNb steels after long steam exposure time at 550 C

International Nuclear Information System (INIS)

Rodak, Kinga; Hernas, Adam; Vodarek, Vlastimil

2015-01-01

Microstructural changes in high alloy (9-12% Cr) creep resistant martensitic X10CrMoVNb9-1 and 12CrMoW . CuVNb steels after 100 000 h of steam exposure at 550 C have been studied using scanning transmission electron microscopy. Precipitates were identified using electron diffraction patterns and energy dispersive X-ray spectroscopy analysis. After long time exposure, a significant coarsening of M 23 C 6 carbides, and intensive precipitation of the coarse Laves phase were observed. Moreover, in the 12CrMoW . CuVNb steel, a low amount of the modified Z-phase particles was detected. The microstructures of the X10Cr . MoVNb9-1 and 12CrMoWCuVNb steels after 100 000 h of exposure differ in several aspects.

Microstructural characterization of second phases in X10CrMoVNb9-1 and 12CrMoWCuVNb steels after long steam exposure time at 550 C

Energy Technology Data Exchange (ETDEWEB)

Rodak, Kinga; Hernas, Adam [Silesian Univ. of Technology, Inst. of Materials Science, Katowice (Poland); Vodarek, Vlastimil [VSB-Technical Univ. of Ostrava (Czech Republic)

2015-07-15

Microstructural changes in high alloy (9-12% Cr) creep resistant martensitic X10CrMoVNb9-1 and 12CrMoW . CuVNb steels after 100 000 h of steam exposure at 550 C have been studied using scanning transmission electron microscopy. Precipitates were identified using electron diffraction patterns and energy dispersive X-ray spectroscopy analysis. After long time exposure, a significant coarsening of M{sub 23}C{sub 6} carbides, and intensive precipitation of the coarse Laves phase were observed. Moreover, in the 12CrMoW . CuVNb steel, a low amount of the modified Z-phase particles was detected. The microstructures of the X10Cr . MoVNb9-1 and 12CrMoWCuVNb steels after 100 000 h of exposure differ in several aspects.

Fireside corrosion and steamside oxidation of 9-12% Cr martensitic steels exposed for long term testing

DEFF Research Database (Denmark)

Montgomery, Melanie; Jensen, S. A.; Rasmussen, F.

2009-01-01

MoV121 and HCM12 for the 12% Cr steels. The test tubes were welded in as part of the existing final superheaters in actual plants and exposure has been conducted over a ten year period (1994-2005). Compared to the older steel types, T92 and HCM12 utilise tungsten to improve their creep strength. From......To obtain long term corrosion and steam oxidation data for the 9-12%Cr ferritic steels, test tube sections have been exposed in Amager 3 and Avedore 1 coal fired power plants in Denmark (formerly run by ENERGI E2). Thus direct comparisons can be made for T91 and T92 for the 9% Cr steels and X20Cr...... Avedore I testing, T91 and T92 can be compared for exposure times up to similar to 48 000 h exposure. From Amager 3 testing, X20, HCM12 and T92 were tested; T92 has been exposed for up to 31 000 h and X20 and HCM12 have had 84 500 h exposure. Tube sections were removed for various exposure durations...

Microstructure and Corrosion Behavior of Ni-Alloy/CrN Nanolayered Coatings

Directory of Open Access Journals (Sweden)

Hao-Hsiang Huang

2011-01-01

Full Text Available The Ni-alloy/CrN nanolayered coatings, Ni-Al/CrN and Ni-P/CrN, were deposited on (100 silicon wafer and AISI 420 stainless steel substrates by dual-gun sputtering technique. The influences of the layer microstructure on corrosion behavior of the nanolayered thin films were investigated. The bilayer thickness was controlled approximately 10 nm with a total coating thickness of 1m. The single-layer Ni-alloy and CrN coatings deposited at 350∘C were also evaluated for comparison. Through phase identification, phases of Ni-P and Ni-Al compounds were observed in the single Ni-alloy layers. On the other hand, the nanolayered Ni-P/CrN and Ni-Al/CrN coatings showed an amorphous/nanocrystalline microstructure. The precipitation of Ni-Al and Ni-P intermetallic compounds was suppressed by the nanolayered configuration of Ni-alloy/CrN coatings. Through Tafel analysis, the corr and corr values ranged from –0.64 to –0.33 V and 1.42×10−5 to 1.14×10−6 A/cm2, respectively, were deduced for various coating assemblies. The corrosion mechanisms and related behaviors of the coatings were compared. The coatings with a nanolayered Ni-alloy/CrN configuration exhibited a superior corrosion resistance to single-layer alloy or nitride coatings.

Nitrogen effect on the tendency of Cr-Ni-MN steels to delayed fracture under stress and hydrogen effects

International Nuclear Information System (INIS)

Suvorova, S.O.; Fillipov, G.A.

1996-01-01

Austenitic steels types 03Kh17N16G10AM5, 03Kh6N12G10AM5 and 07Kh13AG20 with various nitrogen contents were studied for their tendency to delayed fracture using mechanical tests, fractography and X ray diffraction analysis. The steel type 07Kh13G20 exhibited the highest strength in the initial state but showed an increase tendency to delayed fracture after hydrogenation. It is underlined that nitrogen additions essentially intensify the tendency of cold worked steels to delayed fracture. This fact should be taken into account when using nitrogen-containing Cr-Ni-Mn steels under severe operational conditions. 4 refs., 2 tabs

Capture cross sections for Cr, Fe and Ni

International Nuclear Information System (INIS)

Corvi, F.

1990-01-01

Since stainless steel represents about 25% of the volume of a fast power reactor, its constituent elements strongly influence its two main neutronic parameters: critical enrichment and breeding gain. Also, capture in the narrow p and d-wave resonances of Cr, Fe and Ni contributes as much as 10 to 15% of the Doppler coefficient of reactivity. Following sensitivity calculations, typical accuracy requirements in the energy range 0.1-100 keV are 5-10% for capture in Fe and 10-20% for capture in Ni and Cr. 11 refs, 2 tabs

Effects of Cr2N Precipitation on the Antibacterial Properties of AISI 430 Stainless Steel

Directory of Open Access Journals (Sweden)

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.

Creep Rupture Analysis and Life Estimation of 1.25Cr-0.5Mo, 2.25Cr-1Mo and Modified 9Cr-1Mo Steel: A Comparative Study

Science.gov (United States)

Roy, Prabir Kumar

2018-04-01

This paper highlights a comparative assessment of creep life of 1.25Cr-0.5Mo, 2.25Cr-1Mo and modified 9Cr-1Mo steels based on accelerated creep rupture tests. Creep rupture test data have been analysed and creep life of the above mentioned materials have been assessed using Larson Miller parameter at the stress levels of 60 and 42 MPa for different temperatures. Limiting steam temperatures for minimum design life of 105 h at 42 and 60 MPa for the above mentioned steels have also been calculated. Microstructural studies for the three above mentioned steels are also done.

Atomistic study of the hardening of ferritic iron by Ni-Cr decorated dislocation loops

Science.gov (United States)

Bonny, G.; Bakaev, A.; Terentyev, D.; Zhurkin, E.; Posselt, M.

2018-01-01

The exact nature of the radiation defects causing hardening in reactor structural steels consists of several components that are not yet clearly determined. While generally, the hardening is attributed to dislocation loops, voids and secondary phases (radiation-induced precipitates), recent advanced experimental and computational studies point to the importance of solute-rich clusters (SRCs). Depending on the exact composition of the steel, SRCs may contain Mn, Ni and Cu (e.g. in reactor pressure vessel steels) or Ni, Cr, Si, Mn (e.g. in high-chromium steels for generation IV and fusion applications). One of the hypotheses currently implied to explain their formation is the process of radiation-induced diffusion and segregation of these elements to small dislocation loops (heterogeneous nucleation), so that the distinction between SRCs and loops becomes somewhat blurred. In this work, we perform an atomistic study to investigate the enrichment of loops by Ni and Cr solutes and their interaction with an edge dislocation. The dislocation loops decorated with Ni and Cr solutes are obtained by Monte Carlo simulations, while the effect of solute segregation on the loop's strength and interaction mechanism is then addressed by large scale molecular dynamics simulations. The synergy of the Cr-Ni interaction and their competition to occupy positions in the dislocation loop core are specifically clarified.

Corrosion resistance of Ultra-Low-Carbon 19% Cr-11% Ni stainless steel for nuclear fuel reprocessing plants in nitric acid

International Nuclear Information System (INIS)

Ariga, Tamako; Takagi, Yoshio; Inazumi, Toru; Masamura, Katsumi; Sukekawa, M.

1995-01-01

An Ultra-Low-Carbon 19% Cr-11% Ni Stainless Steels used in nuclear fuel reprocessing plants where highly corrosion resistance in nitric acid is required has been developed. This steel has optimized the chemistry composition to decrease inclusions and deformation-induced martensitic transformation. The formation of deformation-induced martensite has the potential danger of accelerating corrosion in nitric acid. In this paper, effects of cold reduction and martensitic transformation on corrosion resistance of Ultra-Low-Carbon Stainless Steels in nitric acid are discussed. The developed steel showed excellent corrosion resistance during long-term exposure to nitric acid. (author)

Effect of chemical composition on irradiation embrittlement and annealing in Ni-Cr-Mo-V reactor pressure vessel steel

Energy Technology Data Exchange (ETDEWEB)

Novosad, P [Czech Nuclear Society, Prague (Czech Republic)

1994-12-31

Results concerning copper and phosphorus influence on radiation-induced changes in the Ni-Cr-Mo-V steel mechanical properties, are presented. Correlations between different mechanical properties for steels with different chemical composition, are presented. A comparison of transition temperature shifts obtained for static and dynamic fracture toughness tests and Charpy impact tests, is discussed. Recovery of radiation hardening, measured by hardness test after isochronal annealing of steels with different compositions, is also shown. Copper content strongly affects irradiation-induced changes of mechanical properties, but phosphorus content in connection with variable copper content has only a small effect. (author). 4 refs., 4 figs., 4 tabs.

Dissipation and accumulation of energy during plastic deformation of Armco -iron and 12Cr18Ni10Ti stainless steel irradiated by neutrons

International Nuclear Information System (INIS)

Toktogulova, D.; Maksimkin, O.; Gusev, M.; Garner, F.

2007-01-01

Full text of publication follows: Much attention is currently being paid in the fusion materials community to modeling of radiation damage and its consequences in structural alloys on mechanical properties. Such activities are best guided with experimental data on the fundamental microstructural and thermodynamic processes involved. This report addresses such fundamental concerns. During plastic deformation of metals some fraction of the externally-applied mechanical energy is converted into heat and is partially accumulated in the form of crystal lattice defects. The thermal release arises from gliding dislocations, their various interactions, their annihilation etc. With respect to irradiated material, one might expect additional heat release caused by interactions of dislocation and radiation-induced defects. To explore this possibility flat mini-tensile specimens of Armco-iron and 12Cr18Ni10Ti stainless steel, both in the annealed condition, were irradiated in the range 2x10 18 to 1.3x10 20 n/cm 2 (E>0.1 MeV) in the WWR-K reactor at T≤350 K. Mechanical tests of both irradiated and non-irradiated specimens were conducted at room temperature in a facility that was a combination of a Calvet calorimeter and a micro-tensile device. This allows simultaneous measurement of mechanical properties and thermodynamic parameters such as deformation work, dissipated heat and latent energy during deformation. The authors derived the kinetics of changes in thermodynamic characteristics versus the deformation level. As the neutron fluence rises, the material's capability to accumulate energy appears to be declining. For example, 12Cr18Ni10Ti irradiated to 1.3x10 20 n/cm 2 did not show any energy accumulation under deformation. In Armco-iron at 1.4x10 19 n/cm 2 the heat release considerably exceeded the deformation work value. The authors assume that such effects might be related with annihilation of point defects and their complexes introduced during irradiation. To test this

Long-term strength and allowable stresses of grade 10Kh9MFB and X10CrMoVNb9-1 (T91/P91) chromium heat-resistant steels

Science.gov (United States)

Skorobogatykh, V. N.; Danyushevskiy, I. A.; Schenkova, I. A.; Prudnikov, D. A.

2015-04-01

Currently, grade X10CrMoVNb9-1 (T91, P91) and 10Kh9MFB (10Kh9MFB-Sh) chromium steels are widely applied in equipment manufacturing for thermal power plants in Russia and abroad. Compilation and comparison of tensile, impact, and long-term strength tests results accumulated for many years of investigations of foreign grade X10CrMoVNb9-1, T91, P91, and domestic grade 10Kh9MFB (10Kh9MFB-Sh) steels is carried out. The property identity of metals investigated is established. High strength and plastic properties of steels, from which pipes and other products are made, for operation under creep conditions are confirmed. Design characteristics of long-term strength on the basis of tests with more than one million of hour-samples are determined ( and at temperatures of 500-650°C). The table of recommended allowable stresses for grade 10Kh9MFB, 10Kh9MFB-SH, X10CrMoVNb9-1, T91, and P91 steels is developed. The long-time properties of pipe welded joints of grade 10Kh9MFB+10Kh9MFB, 10Kh9MFB-Sh+10Kh9MFB-Sh, X10CrMoVNb9-1+X10CrMoVNb9-1, P91+P91, T91+T91, 10Kh9MFB (10Kh9MFB-Sh)+X10CrMoVNb9-1(T/P91) steels is researched. The welded joint reduction factor is experimentally determined.

Influence of ion implanted helium on deuterium trapping in Kh18N10T stainless steel

International Nuclear Information System (INIS)

Tolstolutskaya, G.D.; Ruzhitskij, V.V.; Kopanets, I.E.

2004-01-01

The results are presented on evolution of distribution profiles and helium and deuterium thermal desorption ion implanted in steel 18Cr10NiTi. Accumulation, trapping, retention and microstructure evolution are studied; effect helium and hydrogen simultaneous implantation on these processes is also studied

Controlling the ductile to brittle transition in Fe–9%Cr ODS steels

Energy Technology Data Exchange (ETDEWEB)

Di Martino, S.F., E-mail: s.f.di-martino@lboro.ac.uk; Riddle, N.B.; Faulkner, R.G.

2013-11-15

Probably the most important range of materials for consideration as the blanket material for the tokamak design for fusion reactors ITER and DEMO is the high alloy Fe–9Cr oxide dispersion strengthened ferritic steels. Ferritic steels possess exceptional thermal conductivity and low thermal expansion and are resistant to void swelling. Their main drawback is high ductile to brittle transition temperatures, particularly in the oxide dispersion strengthened versions. This paper describes attempts to reduce the DBTT in an un-irradiated ferritic steel by a novel heat treatment procedure. New batches of high alloy Fe–9Cr oxide dispersion strengthened (Eurofer) ferritic steel have been produced by a powder metallurgy route, and relatively homogeneous material has been produced by hot isostatic pressing (HIP). Mini-Charpy test specimens were made from materials which had been subjected to a matrix of heat treatments with varying solution treatment temperature (ST), cooling rate from the ST temperature, and tempering treatment. The initial DBTT was in the range of 150–200 °C (423–473 K). Downward shifts of up to approximately 200 °C (473 K) have been observed after solution treatment at 1300 °C (1573 K) followed by slow cooling. This paper describes the microstructure of this material, and discussion is made of the likely microstructural factors needed to produce these DBTT downward shifts.

Improved creep and oxidation behavior of a martensitic 9Cr steel by the controlled addition of boron and nitrogen

Energy Technology Data Exchange (ETDEWEB)

Mayr, Peter [Massachusetts Institute of Technology, Cambridge, MA (United States). Dept. of Materials Science; Graz Univ. of Technology (Austria). Inst. of Material Science and Welding; Holzer, Ivan; Mendez-Martin, Francisca [Graz Univ. of Technology (Austria). Inst. of Material Science and Welding; Albu, Mihaela; Mitsche, Stefan [Graz Univ. of Technology (Austria). Inst. for Electron Microscopy; Gonzalez, Vanessa; Agueero, Alina [Instituto Nacional de Tecnica Aeroespacial, Torrejon de Ardoz (Spain)

2010-07-01

This manuscript gives an overview on recent developments of a martensitic steel grade based on 9Cr3W3CoVNb with controlled additions of boron and nitrogen. Alloy design by thermodynamic equilibrium calculations and calculation of boron-nitrogen solubility is discussed. Out of this alloy design process, two melts of a 9Cr3W3CoVNbBN steel were produced. The investigation focused on microstructural evolution during high temperature exposure, creep properties and oxidation resistance in steam at 650 C. Microstructural characterization of ''as-received'' and creep exposed material was carried out using conventional optical as well as advanced electron microscopic methods. Creep data at 650 was obtained at various stress levels. Longest-running specimens have reached more than 20,000 hours of testing time. In parallel, long-term oxidation resistance has been studied at 650 C in steam atmosphere up to 5,000 hours. Preliminary results of the extensive testing program on a 9Cr3W3CoVNbBN steel show significant improvement in respect to creep strength and oxidation resistance compared to the state-of-the-art 9 wt. % Cr martensitic steel grades. Up to current testing times, the creep strength is significantly beyond the +20% scatterband of standard grade P92 material. Despite the chromium content of 9 wt % the material exhibits excellent oxidation resistance. Steam exposed plain base material shows comparable oxidation behavior to coated material, and the corrosion rate of the boron-nitrogen controlled steel is much lower compared to standard 9 wt % Cr steel grades, P91 and P92. (orig.)

characterization and weldability of plasma nitrided P/M martensitic stainless steel X 20 Cr Ni 172

International Nuclear Information System (INIS)

Abdel-Karim, R.A.; El-demellawy, M.A; Waheed, A.F.

2004-01-01

stainless steels are widely used in nuclear applications, as a construction material. in these applications stainless steels suffer from corrosion degradation due severe environment and operating conditions. improving the engineering properties of such material prolong the service life time.in the present study, powder metallurgy technique namely plasma rotating electrode process (PREP) was used to produce martensitic steel DIN X 20 Cr Ni 172 with 0.5 % N. this step was followed by hot isostatic pressing process (HIP) . the effect of N on the weldability of this steel has been investigated . this included microstructure characterization, hardness evaluation and ferrite content measurements. the results showed that the presence of high nitrogen content in this steel resulted in a pore free structure with improved the hardness across the welding area. A single phase with few precipitates was detected on the grain boundaries in the heat affected zone. the results were supplemented by x-ray diffraction patterns and EDAX analysis

Welding of heat-resistant 20% Cr-5% Al steels

International Nuclear Information System (INIS)

Tusek, J.; Arbi, D.; Kosmac, A.; Nartnik, U.

2002-01-01

The paper treats welding of heat-resistant ferritic stainless steels alloyed with approximately 20% Cr and 5% Al. The major part of the paper is dedicated to welding of 20% Cr-5% Al steel with 3 mm in thickness. Welding was carried out with five different welding processes, i. e., manual metal-arc, MIG, TIG, plasma arc, and laser beam welding processes, using a filler material and using no filler material, respectively. The welded joints obtained were subjected to mechanical tests and the analysis of microstructure in the weld metal and the transition zone. The investigations conducted showed that heat-resistant ferritic stainless 20% Cr-5% Al steel can be welded with fusion welding processes using a Ni-based filler material. (orig.)

Effect of Welding Processes on the Microstructure, Mechanical Properties and Residual Stresses of Plain 9Cr-1Mo Steel Weld Joints

Science.gov (United States)

Nagaraju, S.; Vasantharaja, P.; Brahadees, G.; Vasudevan, M.; Mahadevan, S.

2017-12-01

9Cr-1Mo steel designated as P9 is widely used in the construction of power plants and high-temperature applications. It is chosen for fabricating hexcan fuel subassembly wrapper components of fast breeder reactors. Arc welding processes are generally used for fabricating 9Cr-1Mo steel weld joints. A-TIG welding process is increasingly being adopted by the industries. In the present study, shielded metal arc (SMA), tungsten inert gas (TIG) and A-TIG welding processes are used for fabricating the 9Cr-1Mo steel weld joints of 10 mm thickness. Effect of the above welding processes on the microstructure evolution, mechanical properties and residual stresses of the weld joints has been studied in detail. All the three weld joints exhibited comparable strength and ductility values. 9Cr-1Mo steel weld joint fabricated by SMAW process exhibited lower impact toughness values caused by coarser grain size and inclusions. 9Cr-1Mo steel weld joint fabricated by TIG welding exhibited higher toughness due to finer grain size, while the weld joint fabricated by A-TIG welding process exhibited adequate toughness values. SMA steel weld joint exhibited compressive residual stresses in the weld metal and HAZ, while TIG and A-TIG weld joint exhibited tensile residual stresses in the weld metal and HAZ.

Mechanical behavior of 9Cr-1Mo-1V steel due to creep fatigue deformation

International Nuclear Information System (INIS)

Kim, Sang Tae; Kim, Jae Kyoung; Lee, Hak Sun; Oh, Sang Hyun; Kwun, Sook In; Kim, Chung Seok

2005-01-01

Creep-fatigue tests with trapezoid load wave were performed on a 9Cr-1Mo-1V steel at high temperature(550 .deg. C). Trapezoid load wave is considering about hold time for creep effects. we could find out some information in the relationship between number of cycles to failure and hold time. The number of cycles to failure depended on hold time. The cyclic behavior of 9Cr-1Mo-1V steel was characterized by cyclic softening with increasing number of cycles in high temperature. Also we could observe some cavity in the specimens. The size of cavity was different from each hold time

Kinetics of Z-Phase Precipitation in 9 to 12 pct Cr Steels

DEFF Research Database (Denmark)

Danielsen, Hilmar Kjartansson; Nunzio, Paolo Emilio di; Hald, John

2013-01-01

precipitated Z-phase 20 to 50 times faster than the 9 pct Cr steel. Transmission electron microscopy (TEM) was applied to follow the Z-phase precipitation, using energy-dispersive X-ray spectroscopy (EDS) line scans and atomic resolution imaging. © The Minerals, Metals & Materials Society and ASM International...

HIGH TEMPERATURE TENSILE PROPERTIES OF NEW FE-CR-MN DEVELOPED STEEL

Directory of Open Access Journals (Sweden)

M. Mahmoudiniya

2017-03-01

Full Text Available Nowadays, Ni-free austenitic stainless steels are being developed rapidly and high price of nickel is one of the most important motivations for this development. At present research a new FeCrMn steel was designed and produced based on Fe-Cr-Mn-C system. Comparative studies on microstructure and high temperature mechanical properties of  new steel and AISI 316 steel were done. The results showed that new FeCrMn developed steel has single austenite phase microstructure, and its tensile strength and toughness were higher than those of 316 steel at 25, 200,350 and 500°C. In contrast with 316 steel, the new FeCrMn steel did not show strain induced transformation and dynamic strain aging phenomena during tensile tests that represented higher austenite stability of new developed steel. Lower density and higher strength of the new steel caused higher specific strength in comparison with the 316 one that can be considered as an important advantage in structural applications but in less corrosive environment

Erosion-oxidation behavior of thermal sprayed Ni20Cr alloy and WC and Cr3C2 cermet coatings

Directory of Open Access Journals (Sweden)

Clarice Terui Kunioshi

2005-06-01

Full Text Available An apparatus to conduct high temperature erosion-oxidation studies up to 850 °C and with particle impact velocities up to 15 m.s-1 was designed and constructed in the Corrosion Laboratories of IPEN. The erosion-oxidation behavior of high velocity oxy fuel (HVOF sprayed alloy and cermet coatings of Ni20Cr, WC 20Cr7Ni and Cr3C2 Ni20Cr on a steel substrate has been studied. Details of this apparatus and the erosion-oxidation behavior of these coatings are presented and discussed. The erosion-oxidation behavior of HVOF coated Cr3C2 25(Ni20Cr was better than that of WC 20Cr7Ni, and the erosion-oxidation regimes have been identified for these coatings at particle impact velocity of 3.5 m.s-1, impact angle of 90° and temperatures in the range 500 to 850 °C.

Effect of silicon contents on the microstructures and mechanical properties of heat affected zones for 9Cr2WVTa steels

Energy Technology Data Exchange (ETDEWEB)

Wang, Jian [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, 110016, Shenyang (China); Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Science, 110016, Shenyang (China); Lu, Shanping, E-mail: shplu@imr.ac.cn [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, 110016, Shenyang (China); Rong, Lijian [Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Science, 110016, Shenyang (China); Li, Dianzhong [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, 110016, Shenyang (China)

2016-03-15

The weldability of 9Cr2WVTa steels with silicon content varying from 0.30 wt.% to 1.36 wt.% was studied to meet the requirement of Generation-Ⅳ nuclear reactor. Samples of enlarged HAZs were fabricated by a thermal-mechanical simulator based on the simulation and measurement of non-equilibrium phase transformation. The content of δ-ferrite in the HAZs increased with the silicon content and the peak temperature of welding thermal cycle. The impact toughness in the HAZs decreased in different degrees when the δ-ferrite exhibits stripe (lower than 4.82%) or blocky types (higher than 4.82%). Post weld heat treatment (PWHT) has a significant role on improving the toughness. Adding silicon content increased the volume of δ-ferrite and therefore, decreased the tensile strength of the HAZs for 9Cr2WVTa steels. Silicon also as solid solution strengthening element increased the tensile strength. The 9Cr2WVTa steel has good weldability when the silicon content is lower than 0.60 wt.%. - Highlights: • The weldability of 9Cr2WVTa steel with different silicon contents was studied. • The impact toughness decreased in different degrees owing to the δ-ferrite. • PWHT has a significant role on improving the impact toughness. • The 9Cr2WVTa steel with silicon content not exceeding 0.60 wt.% has good weldability.

The change of NiCrBSi alloys’ phase composition after plasma spraying

Directory of Open Access Journals (Sweden)

A. Dudek

2008-08-01

Full Text Available Material for investigations was NiCrBSi powder for components’ coatings which improve their corrosion resistance as well as resistance to friction wear and erosion. Plasma spraying method was used to produce a coating with thickness of 300 μm on low-alloy steel which was then remelted with the base material. Using X-ray quality analysis, phase composition was determined for: NiCrBSi powder, obtained coating and the alloyed surface layer. Crystallinity degree was also calculated for NiCrBSi layer sprayed on the base material.

Thermal Aging Evaluation of Mod. 9Cr-1Mo Steel using Nonlinear Rayleigh Waves

Energy Technology Data Exchange (ETDEWEB)

Joo, Young-Sang; Kim, Hoe-Woong; Kim, Jong-Bum [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Marino, Daniel; Kim, Jin-Yeon; Jacobs, L.J [Georgia Institute of Technology, Atlanta (United States); Ruiz, Alberto [UMSNH, Morelia (Mexico)

2014-10-15

Thermal aging can pose a high risk to decreases in the mechanical properties such as strength or creep resistance. This can lead to an unexpected failure during long term operation. Nonlinear NDE techniques are preferred over conventional NDE techniques (linear ultrasonic measurements) because nonlinear ultrasonic techniques have shown their capability to detect a microstructural damage in the structures undergoing fatigue and creep. These nonlinear ultrasonic techniques make use of the fact that the dislocation density increases, which will create a nonlinear distortion of an ultrasonic wave; this damage causes the generation of measurable higher harmonic components in an initially mono-chromatic ultrasonic signal. This study investigates the recently developed non-contact nonlinear ultrasonic technique to detect the microstructural damage of mod. 9Cr-1Mo steel based on nonlinear Rayleigh wave with varying propagation distances. Nonlinear Rayleigh surface wave measurements using a non-contact, air-coupled ultrasonic transducer have been applied for the thermal aging evaluation of modified 9Cr-1Mo ferritic-martensitic steel. Thermal aging for various heat treatment times of mod.. 9Cr-1Mo steel specimens is performed to obtain the nucleation and growth of precipitated particles in specimens. The amplitudes of the first and second harmonics are measured along the propagation distance and the relative nonlinearity parameter is obtained from these amplitudes. The relative nonlinearity parameter shows a similar trend with the Rockwell C hardness.

The influence of Cr and Al pack cementation on low carbon steel to improve oxidation resistance

Science.gov (United States)

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

2012-06-01

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.

The rate(time)- dependent mechanical behavior modified 9Cr-1Mo steel, 3

International Nuclear Information System (INIS)

Moosbrugger, J.C.

1991-01-01

In this paper, constitutive equations are presented for the nonisothermal small strain behavior of modified 9Cr-1Mo steel between 25degC - 600degC. The basic framework uses the superposition of nonlinear kinematic hardening rules as proposed by Chaboche and coworkes. A framework for accounting for isotropic softening is presented wherein this softening can be included in a drag stress, in a yield stress or as a decrease in the saturation level of kinematic hardening or some combination of these; a single isotropic softening equation is used as determined from experiments. The behavior of modified 9Cr-1Mo steel between 25degC - 600degC has been investigated by Swindeman, and Majors et. al. and many important features have been discussed. Here, model parameters are determined from available isothermal uniaxial data and some correlations with isothermal and nonisothermal tests are presented. (J.P.N.)

Development of small punch tests for ductile-brittle transition temperature measurement of temper embrittled Ni-Cr steels

International Nuclear Information System (INIS)

Baik, J.M.; Kameda, J.; Buck, O.

1983-01-01

Small punch tests were developed to determine the ductile-brittle transition temperature of nickel-chromium (Ni-Cr) steels having various degrees of temper embrittlement and various microstructures. It was found that the small punch test clearly shows the ductile-brittle transition behavior of the temper-embrittled steels. The measured values were compared with those obtained from Charpy impact and uniaxial tensile tests. The effects of punch tip shape, a notch, and the strain rate on the ductile-brittle transition behavior were examined. It was found that the combined use of a notch, high strain rates, and a small punch tip strongly affects the ductile-brittle transition behavior. Considerable variations in the data were observed when the small punch tests were performed on coarse-grained steels. Several factors controlling embrittlement measurements of steels are discussed in terms of brittle fracture mechanisms

Low-cost, high-strength Fe--Ni--Cr alloys for high temperature exhaust valve application

Science.gov (United States)

Muralidharan, Govindarajan

2017-09-05

An Fe--Ni--Cr alloy is composed essentially of, in terms of wt. %: 2.4 to 3.7 Al, up to 1.05 Co, 14.8 to 15.9 Cr, 25 to 36 Fe, up to 1.2 Hf, up to 4 Mn, up to 0.6 Mo, up to 2.2 Nb, up to 1.05 Ta, 1.9 to 3.6 Ti, up to 0.08 W, up to 0.03 Zr, 0.18 to 0.27 C, up to 0.0015 N, balance Ni, wherein, in terms of atomic percent: 8.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.11.5, 0.53.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.65, and 0.16.ltoreq.Cr/(Fe+Ni+Cr+Mn).ltoreq.0.21, the alloy being essentially free of Cu, Si, and V.

Influence of creep ductility on creep-fatigue behaviour of 20%Cr/25%Ni/Nb stainless steel

International Nuclear Information System (INIS)

Gladwin, D.; Miller, D.A.

1985-01-01

The influence of creep ductility on creep-fatigue endurance of 20%Cr/25%Ni/Nb stainless steel has been examined. In order to induce different creep ductilities in the 20/25/Nb stainless steel, three different thermo-mechanical routes were employed. These resulted in a range of ductilities (3-36%) being obtained at the strain rates of interest. Strain controlled slow-fast creep-fatigue cycles were used with strain rates of 10 -6 s -1 , 10 -7 s -1 in tension and 10 -3 s -1 in compression. It was found that creep ductility strongly influenced the creep-fatigue endurance of the 20/25/Nb stainless steel. When failure was creep dominated endurance was found to be directly proportional to the creep ductility. A ductility exhaustion model has been used to successfully predict creep-fatigue endurance when failure was creep dominated. (author)

Low-activation Mn-Cr austenitic stainless steel with further reduced content of long-lived radioactive elements

Energy Technology Data Exchange (ETDEWEB)

Onozuka, M.; Saida, T.; Hirai, S. [Mitsubishi Heavy Ind. Ltd., Yokohama (Japan); Kusuhashi, M.; Sato, I.; Hatakeyama, T. [The Japan Steel Works Ltd., Chatsu-machi 4, Muroran 051-8505 (Japan)

1998-06-01

Low-activation austenitic stainless steel based on Mn-Cr non-magnetic steels has been developed. The alloying elements of long-life activation, such as Ni, Mo and Co, were eliminated and substituted with Mn along with an addition of N. A Mn-Cr austenitic stainless steel, 24.5Mn-13.5Cr-0.02C-0.2N, has been developed successfully. Examined material properties, including mechanical, thermal and magnetic properties, as well as weldability and characteristics of corrosion resistance, are presented. It was found that the alloy has excellent material properties virtually equivalent to those of 316SS. In this study, the applicability of the Schaeffler, DeLong and Hull constitution diagrams for the stainless steels with low Ni and high Mn contents was also examined. The boundary conditions distinguishing the single austenite phase from the others have been identified for the Mn-Cr steels. (orig.) 22 refs.

Low-activation Mn Cr austenitic stainless steel with further reduced content of long-lived radioactive elements

Science.gov (United States)

Onozuka, Masanori; Saida, Tomikane; Hirai, Shouzou; Kusuhashi, Mikio; Sato, Ikuo; Hatakeyama, Tsuyoshi

1998-06-01

Low-activation austenitic stainless steel based on Mn-Cr non-magnetic steels has been developed. The alloying elements of long-life activation, such as Ni, Mo and Co, were eliminated and substituted with Mn along with an addition of N. A Mn-Cr austenitic stainless steel, 24.5Mn-13.5Cr-0.02C-0.2N, has been developed successfully. Examined material properties, including mechanical, thermal and magnetic properties, as well as weldability and characteristics of corrosion resistance, are presented. It was found that the alloy has excellent material properties virtually equivalent to those of 316SS. In this study, the applicability of the Schaeffler, DeLong and Hull constitution diagrams for the stainless steels with low Ni and high Mn contents was also examined. The boundary conditions distinguishing the single austenite phase from the others have been identified for the Mn-Cr steels.

Microstructural, mechanical and tribological investigation of 30CrMnSiNi2A ultra-high strength steel under various tempering temperatures

Science.gov (United States)

Arslan Hafeez, Muhammad; Farooq, Ameeq

2018-01-01

The aim of the research was to investigate the variation in microstructural, mechanical and tribological characteristics of 30CrMnSiNi2A ultra-high strength steel as a function of tempering temperatures. Steel was quenched at 880 °C and tempered at five different tempering temperatures ranging from 250 °C to 650 °C. Optical microscopy and pin on disc tribometer was used to evaluate the microstructural and wear properties. Results show that characteristics of 30CrMnSiNi2A are highly sensitive to tempering temperatures. Lathe and plate shaped martensite obtained by quenching transform first into ε-carbide, second cementite, third coarsened and spheroidized cementite and finally into recovered ferrite and austenite. Hardness, tensile and yield strengths decreased while elongation increased with tempering temperatures. On the other hand, wear rate first markedly decreased and then increased. Optimum amalgamation of characteristics was achieved at 350 °C.

Microstructural characterization of 5-9% chromium reduced-activation steels

International Nuclear Information System (INIS)

Jayaram, R.; Klueh, R.L.

1997-01-01

The microstructures of a 9Cr-2W-0.25-0.1C (9Cr-2WV), a 9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa), a 7Cr-2W-0.25V-0.07Ta-0.1C (7Cr-2WVTa), and a 5Cr-2W-0.25V-0.07Ta-0.1C (5Cr-2WVTa) steel (all compositions are in weight percent) have been characterized by Analytical Electron Microscopy (AEM) and Atom Probe Field Ion Microscopy (APFIM). The matrix in all four reduced-activation steels was 100% martensite. In the two 9Cr steels, the stable precipitates were blocky M 23 C 6 and small spherical MC. The two lower-chromium steels contained blocky M 7 C 3 and small needle-shaped carbonitrides in addition to M 23 C 6 . AEM and APFIM analysis revealed that in the steels containing tantalum, the majority of the tantalum was in solid solution. The experimental observations were in good agreement with phases and compositions predicted by phase equilibria calculations

Effects of mean strain on the random cyclic stress-strain relations of 0Cr18Ni10Ti pipe steel

International Nuclear Information System (INIS)

Zhao Yongxiang; Yang Bing

2005-01-01

Experimental study is performed for the effects of the mean strain on the random cyclic stress-strain relations of the new nuclear material, 0Cr18Ni10Ti pipe steel. From saving the size of specimens, an improved maximum likelihood fatigue test method is proposed to operate the present strain-controlled fatigue tests. Six straining ratios, -1, -0.52, -0.22, 0.029, 0.18, and 0.48, respectively, are applied to study the effects. Fatigue test has been carried out on totally 104 specimens. The test results reveal that the material exhibits a Masing behaviour and the saturation hysteresis loops under the six ratios hold an entirely relaxation effect of mean stress. There is no effectively method for the description of the mean straining effects under this case. Previous Zhao's random stress-strain relations are therefore applied to characterizing effectively the scattering test data under the six ratios on a basis of Ramberg-Osgood equation. Then the effects of the ratios are analyzed respectively on the average stress amplitudes, the standard deviations of the stress amplitudes, and the stress amplitudes under different survival probabilities and confidences. The results reveal that the ratios act a relatively decreasing effect to the stress amplitudes under higher survival probabilities and confidences. The strongest effect appears at the ratio of 0.029, and a weaker effect acts as the distance increase of the ratio from the zero. In addition, it is indicated that the effects from the sense of average fatigue lives might result in a wrong conclusion. The effects can be appropriately assessed from a probabilistic sense to take into account the scattering regularity of test data and the size of sampling. (author)

Low-field spin dynamics of Cr7Ni and Cr7Ni-Cu -Cr 7Ni molecular rings as detected by μ SR

Science.gov (United States)

Sanna, S.; Arosio, P.; Bordonali, L.; Adelnia, F.; Mariani, M.; Garlatti, E.; Baines, C.; Amato, A.; Sabareesh, K. P. V.; Timco, G.; Winpenny, R. E. P.; Blundell, S. J.; Lascialfari, A.

2017-11-01

Muon spin rotation measurements were used to investigate the spin dynamics of heterometallic Cr7Ni and Cr7Ni -Cu-Cr7Ni molecular clusters. In Cr7Ni the magnetic ions are arranged in a quasiplanar ring and interact via an antiferromagnetic exchange coupling constant J , while Cr7Ni -Cu-Cr7Ni is composed of two Cr7Ni linked by a bridging moiety containing one Cu ion, that induces an inter-ring ferromagnetic interaction J'≪J . The longitudinal muon relaxation rate λ collected at low magnetic fields μ0H BPP)-like heuristic fitting model that takes into account of a distribution of electronic spin characteristic times for T >5 K, while the shoulder presented by Cr7Ni can be reproduced by a BPP function that incorporates a single electronic characteristic time theoretically predicted to dominate for T <5 K. The flattening of λ (T ) in Cr7Ni -Cu-Cr7Ni occurring at very low temperature can be tentatively attributed to field-dependent quantum effects and/or to an inelastic term in the spectral density of the electronic spin fluctuations.

Overview of 9Cr steels properties for structural application in sodium fast reactors

International Nuclear Information System (INIS)

Cabet, Celine; Courouau, Jean-Louis; Dalle, France; Desgranges, Clara; Forest, Laurent; Martinelli, Laure; Sauzay, Maxime

2015-01-01

A research and development programme has been launched by CEA, EDF and AREVA for the choice and qualification of material for sodium fast reactor (SFR) structural components. The requirements on steam generator (SG) are demanding, with operating temperatures ranging from 240 deg. C to 530 deg. C in water/steam and in sodium for an extended design life of several decades. The selection of the SG materials is based on many characteristics: fabrication, welding, thermal properties, mechanical strength at low and high temperature, environmental resistance. 9%Cr steels which are relevant candidate alloys for different designs of SGs have been extensively studied in the past decade. The objective of this paper is to review some advances made at CEA on determining properties of the X10CrMoVNb9-1 steel (hereafter named 'grade 91'): welding, modelling of cyclic softening, modelling of long-term creep, compatibility with liquid sodium, corrosion in steam. (authors)

High temperature oxidation of 9% and 12% Cr steel: effect of water vapour; Oxidation haute temperature d'un acier 9% et 12% de teneur Cr. Effet de la vapeur d'eau

Energy Technology Data Exchange (ETDEWEB)

Evin, H.; Heritier, D.; Chevalier, S. [Universite de Bourgogne, Institut Carnot de Bourgogne UMR 5209 CNRS, 21 - Dijon (France); Fojer, C. [OCAS N.V. ArcelorMittal Research Industry Gent, Zelzate (Belgium)

2008-07-01

Isothermal tests were performed on commercial 9%Cr and 12%Cr steels between 600 and 750 deg C in air under atmospheric pressure. The same steels were also tested in oxidizing atmosphere enriched with 12% H{sub 2}O at 700 deg C for 24 hours. Kinetics data were registered and the corrosion products were analyzed using different characterization tools such as scanning electron microscope, x-ray diffraction and secondary ions mass spectrometry. 9%Cr steels showed very limited high temperature corrosion behavior in air, because a breakaway appeared after less than 80 hours at 750 deg C. Spinel oxides composed of iron, chromium and manganese (Mn{sub 1.5}Cr{sub 1.5}O{sub 4} and MnFe{sub 2}O{sub 4}) were identified over the surfaces of both steel grades after oxidation. (Cr,Fe){sub 2}O{sub 3} was also identified especially at 700 deg C and 750 deg C, whereas Fe{sub 2}O{sub 3} mainly grew at 600 and 650 deg C. Differences in oxide morphology and composition were noticed between the samples oxidized under air and air + 12 % water vapor. (authors)

Observations of defect structure evolution in proton and Ni ion irradiated Ni-Cr binary alloys

Energy Technology Data Exchange (ETDEWEB)

Briggs, Samuel A., E-mail: sabriggs2@wisc.edu [University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Barr, Christopher M. [Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Pakarinen, Janne [University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); SKC-CEN Belgian Nuclear Research Centre, Boeretang 200, B-2400 Mol (Belgium); Mamivand, Mahmood [University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Hattar, Khalid [Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185 (United States); Morgan, Dane D. [University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Taheri, Mitra [Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Sridharan, Kumar [University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States)

2016-10-15

Two binary Ni-Cr model alloys with 5 wt% Cr and 18 wt% Cr were irradiated using 2 MeV protons at 400 and 500 °C and 20 MeV Ni{sup 4+} ions at 500 °C to investigate microstructural evolution as a function of composition, irradiation temperature, and irradiating ion species. Transmission electron microscopy (TEM) was applied to study irradiation-induced void and faulted Frank loops microstructures. Irradiations at 500 °C were shown to generate decreased densities of larger defects, likely due to increased barriers to defect nucleation as compared to 400 °C irradiations. Heavy ion irradiation resulted in a larger density of smaller voids when compared to proton irradiations, indicating in-cascade clustering of point defects. Cluster dynamics simulations were in good agreement with the experimental findings, suggesting that increases in Cr content lead to an increase in interstitial binding energy, leading to higher densities of smaller dislocation loops in the Ni-18Cr alloy as compared to the Ni-5Cr alloy. - Highlights: • Binary Ni-Cr alloys were irradiated with protons or Ni ions at 400 and 500 °C. • Higher irradiation temperatures yield increased size, decreased density of defects. • Hypothesize that varying Cr content affects interstitial binding energy. • Fitting CD models for loop nucleation to data supports this hypothesis.

The effects of minor alloy modifications and heat treatment on the microstructure and creep rupture behavior of 2.25Cr-1Mo Steel

International Nuclear Information System (INIS)

Todd, J.A.; Chung, D.W.; Parker, E.R.

1983-01-01

The effects of alloy additions on the microstructure of simulated cooled and tempered 2.25Cr-1Mo steels have been studied using transmission electron microscopy. Carbide precipitation sequences have been identified in the modification 3Cr-1Mo-1Mn-1Ni and compared to those in 2.25Cr-1Mo steels modified with Mn and Ni and also with Ti, V and B. The influence of minor compositional changes on the creep rupture behavior of 2.25Cr-1Mo steel has been studied at 500 C, 560 C, and 600 C. The most significant effect of alloy modifications on creep properties resulted from additions of Mn and Cr. Preliminary studies show that 1% Mn and 0.5Mn + 1Ni + 0.75Cr additions significantly reduce creep strength at all three temperatures for tests up to 2000 hours duration. The 3Cr-1Mo-1Mn-1Ni steel showed improvements in rupture ductility at all temperatures when compared with the base 2.25Cr-1Mo steel and the manganese-nickel modifications. Plots of the Larson-Miller parameter for both these modifications lay within the scatter band for commercial 2.25Cr-1Mo steels

Effect of Molybdenum on the Corrosion Behavior of High-Entropy Alloys CoCrFeNi2 and CoCrFeNi2Mo0.25 under Sodium Chloride Aqueous Conditions

Directory of Open Access Journals (Sweden)

Alvaro A. Rodriguez

2018-01-01

Full Text Available The corrosion behavior of high-entropy alloys (HEAs CoCrFeNi2 and CoCrFeNi2Mo0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276 and stainless steel 316L (UNS 31600 to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pitting corrosion. Cyclic voltammetry (CV can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi2Mo0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi2 and stainless steel 316L.

Standard and applied material testing methods of austenitic CrNi stainless steels in different nitric acid media - procedures and results

International Nuclear Information System (INIS)

Leistikow, S.; Kraft, R.; Schanz, G.

1989-07-01

Extended ASTM Standard Huey Testing has been performed in at 120 0 C boiling 14.4 molar (65%) nitric acid during 15 periods (15x48 = 720 h duration) for quality control of numerous commercial nitric acid resistant austenitic CrNi steels. It was shown how sensitively the chosen testing conditions could differentiate between CrNi steels of the same nominal composition as specified for DIN W.Nr. 1.4306 (AISI Type 304 L), but with varying residual element contents. Within an attempt to differentiate within this group of steels by application of electrochemical methods, potentiostatic tests at 1250 mV in nitric acid of equal concentration and temperature were able to detect remarkable differences in corrosion behaviour already after one hour. Another approach, more typical for the electrochemical potentials during materials application in reprocessing plants of nuclear fuel, gave preference to long-term immersion tests, which were performed in nitric acid of lower concentration and temperature. Reference tests in pure 7 molar, 90 0 C nitric acid could only reveal by surface attack small differences in steel quality by exposures of 720 h duration. To shorten the test time by an increase of the redox potential chromium (VI) ions were added to the nitric acid. In a solution of 0,5 g Gr (VI)/l at 90 0 C remarkable differences in corrosion behavior of the steels - similar to the Huey test results - became measurable by means of gravimetry and metallography already during a short-term exposure of 24-71 h. (orig./MM) [de

Microstructural characterization of 5-9% chromium reduced-activation steels

Energy Technology Data Exchange (ETDEWEB)

Jayaram, R. [Univ. of Pittsburgh, PA (United States); Klueh, R.L. [Oak Ridge National Lab., TN (United States)

1997-08-01

The microstructures of a 9Cr-2W-0.25-0.1C (9Cr-2WV), a 9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa), a 7Cr-2W-0.25V-0.07Ta-0.1C (7Cr-2WVTa), and a 5Cr-2W-0.25V-0.07Ta-0.1C (5Cr-2WVTa) steel (all compositions are in weight percent) have been characterized by Analytical Electron Microscopy (AEM) and Atom Probe Field Ion Microscopy (APFIM). The matrix in all four reduced-activation steels was 100% martensite. In the two 9Cr steels, the stable precipitates were blocky M{sub 23}C{sub 6} and small spherical MC. The two lower-chromium steels contained blocky M{sub 7}C{sub 3} and small needle-shaped carbonitrides in addition to M{sub 23}C{sub 6}. AEM and APFIM analysis revealed that in the steels containing tantalum, the majority of the tantalum was in solid solution. The experimental observations were in good agreement with phases and compositions predicted by phase equilibria calculations.

Oxide fuel fabrication technology development of the FaCT project (5). Current status on 9Cr-ODS steel cladding development for high burn-up fast reactor fuel

International Nuclear Information System (INIS)

Ohtsuka, Satoshi; Kaito, Takeji; Yano, Yasuhide; Yamashita, Shinichiro; Ogawa, Ryuichiro; Uwaba, Tomoyuki; Koyama, Shinichi; Tanaka, Kenya

2011-01-01

This paper describes evaluation results of in-reactor integrity of 9Cr and 12Cr-ODS steel cladding tubes and the plan for reliability improvement in homogeneous tube production, both of which are key points for the commercialized use of ODS steels as long-life fuel cladding tubes. A fuel assembly in the BOR-60 irradiation test including 9Cr and 12Cr-ODS fuel pins has achieved the highest burn-up, i.e. peak burn-up of 11.9at% and peak neutron dose of 51dpa, without any fuel pin rupture and microstructure instability. In another fuel assembly containing 9Cr and 12Cr-ODS steel fuel pins whose peak burn-up was 10.5at%, one 9Cr-ODS steel fuel pin failed near the upper end of the fuel column. A peculiar microstructure change occurred in the vicinity of the ruptured area. The primary cause of this fuel pin rupture and microstructure change was shown to be the presence of metallic Cr inclusions in the 9Cr-ODS steel tube, which had passed an ultrasonic inspection test for defects. In the next stage from 2011 to 2013, the fabrication technology of full pre-alloy 9Cr-ODS steel cladding tube will be developed, where the handling of elemental powder is prohibited in the process. (author)

In-situ Raman and X-ray photoelectron spectroscopic studies on the pitting corrosion of modified 9Cr-1Mo steel in neutral chloride solution

Science.gov (United States)

Ramya, S.; Nanda Gopala Krishna, D.; Mudali, U. Kamachi

2018-01-01

In-situ Raman and X-ray photoelectron spectroscopic studies were performed for the identification of native and corroded surface oxide layers of modified 9Cr-1Mo steel. The Raman data obtained for native oxide layer of modified 9Cr-1Mo steel revealed that it was mainly composed of oxides of Fe and Cr. The presence of alloying element Mo was found to be less significant in the native oxide film. The oxides of Cr were dominant at the surface and were found to be decreasing closer to metal/oxide layer interface. The changes in the chemical composition of the native films upon in-situ pitting during potentiostatic polarization experiment were characterized by in-situ Raman analysis. The corrosion products of potentiostatically polarized modified 9Cr-1Mo steel was composed of dominant Fe (III) phases viz., γ- Fe2O3, α and γ - FeOOH along with the oxides of chromium. The results from Raman analysis were corroborated with the XPS experiments on as received and pitted samples of modified 9Cr-1Mo steel specimens. It was observed that the oxides of Cr and Mo contributed for the stability of the surface layer by forming Cr2O3 and MoO3. Also, the study attempted to find out the intermediate corrosion products inside the metastable pits to account for the pseudo passive behavior of modified 9Cr-1Mo steel in 0.1 M NaCl solution.

Representation of the properties 10 CrMoNiNb 9 10

International Nuclear Information System (INIS)

Dette, M.; Hahn, H.; Nieuwland, H.C.D.; Tichler, J.W.

The high-temperature ferritic steal 10 CrMoNiNb 9 10 is used as structural material in nuclear steam generators. It is exposed to loads within the creep range. In order to resist safety also loads caused by incidents after long temperature stress, the time-independent stability parameters must not fall below specified minimum values. The material is characterised by the stability degree Nb/C+N and the niobium excess δ Nb. (orig.) [de

Heat treatment effects on impact toughness of 9Cr-1MoVNb and 12Cr-1MoVW steels irradiated to 100 dpa

Energy Technology Data Exchange (ETDEWEB)

Klueh, R.L.; Alexander, D.J. [Oak Ridge National Lab., TN (United States)

1997-08-01

Plates of 9Cr-1MoVNb and 12Cr-1MoVW steels were given four different heat treatments: two normalizing treatments were used and for each normalizing treatment two tempers were used. Miniature Charpy specimens from each heat treatment were irradiated to {approx}19.5 dpa at 365{degrees}C and to {approx}100 dpa at 420{degrees}C in the Fast Flux Test Facility (FFTF). In previous work, the same materials were irradiated to 4-5 dpa at 365{degrees}C and 35-36 dpa at 420{degrees}C in FFTF. The tests indicated that prior austenite grain size, which was varied by the different normalizing treatments, had a significant effect on impact behavior of the 9Cr-1MoVNb but not on the 12Cr-1MoVW. Tempering treatment had relatively little effect on the shift in DBTT for both steels. Conclusions are presented on how heat treatment can be used to optimize impact properties.

Heat treatment effects on impact toughness of 9Cr-1MoVNb and 12Cr-1MoVW steels irradiated to 100 dpa

International Nuclear Information System (INIS)

Klueh, R.L.; Alexander, D.J.

1997-01-01

Plates of 9Cr-1MoVNb and 12Cr-1MoVW steels were given four different heat treatments: two normalizing treatments were used and for each normalizing treatment two tempers were used. Miniature Charpy specimens from each heat treatment were irradiated to ∼19.5 dpa at 365 degrees C and to ∼100 dpa at 420 degrees C in the Fast Flux Test Facility (FFTF). In previous work, the same materials were irradiated to 4-5 dpa at 365 degrees C and 35-36 dpa at 420 degrees C in FFTF. The tests indicated that prior austenite grain size, which was varied by the different normalizing treatments, had a significant effect on impact behavior of the 9Cr-1MoVNb but not on the 12Cr-1MoVW. Tempering treatment had relatively little effect on the shift in DBTT for both steels. Conclusions are presented on how heat treatment can be used to optimize impact properties

Preliminary Microstructural and Microscratch Results of Ni-Cr-Fe and Cr3C2-NiCr Coatings on Magnesium Substrate

Science.gov (United States)

Istrate, B.; Munteanu, C.; Lupescu, S.; Benchea, M.; Vizureanu, P.

2017-06-01

Thermal coatings have a large scale application in aerospace and automotive field, as barriers improving wear mechanical characteristics and corrosion resistance. In present research, there have been used two types of coatings, Ni-Cr-Fe, respectively Cr3C2-NiCr which were deposited on magnesium based alloys (pure magnesium and Mg-30Y master alloy). There have been investigated the microstructural aspects through scanning electronic microscopy and XRD analysis and also a series of mechanical characteristics through microscratch and indentation determinations. The results revealed the formation of some adherent layers resistant to the penetration of the metallic indenter, the coatings did not suffer major damages. Microstructural analysis highlighted the formation of Cr3C2, Cr7C3, Cr3Ni2, Cr7Ni3, FeNi3, Cr-Ni phases. Also, the apparent coefficient of friction for Ni-Cr-Fe coatings presents superior values than Cr3C2-NiCr coatings.

Influence of Nb content on grain size and mechanical properties of 18 wt% Cr ferritic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Kang, Y. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Mao, W.M., E-mail: weiminmao@263.net [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Chen, Y.J. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Jing, J.; Cheng, M. [Taizhou Xinyu Precision Manufacture Company Limited, Jiangyan 225500, Jiangsu (China)

2016-11-20

The influence of Nb contents between 0.20 and 1.20 wt% on the grain size and mechanical properties of 18 wt% Cr ferritic stainless steel produced by investment casting was investigated. The average grain sizes of the three steels decreased apparently with increasing Nb content mainly due to the increasing number of pre-existing oxides formed at higher temperature, which were more likely to be the nuclei of heterogeneous nucleation. The thermodynamic analysis of Nb(C,N) formation was in conformity to the experimental result that the Nb(C,N) precipitates became larger with increasing Nb content. The as-cast specimen with the smallest grain size of steel C had the worse tensile strength and elongation in comparison with the as-cast specimens of steels A and B, mostly owing to the catenarian and dendritic Nb(C,N) particles distributed densely at the grain boundaries. The mechanical properties of specimens were not improved remarkably through high temperature solid-solution, whereas the mechanical properties of normalized specimens in the three steels were improved to different degrees. The coalescence and sparse distribution of smaller precipitates at grain boundaries after normalizing effectively weakened the local stress concentration arising from the reticular distribution of particles. The normalized specimen of steel A with 0.24 wt% Nb still showed good mechanical properties. Normalizing at 850 °C for 2 h is the appropriate heat treatment for the 18 wt% Cr ferritic stainless steel. The comparatively rational Nb content of the ferritic stainless steel is between 0.20 and 0.40 wt% for investment casting production.

Difference between Cr and Ni K-edge XANES spectra of rust layers formed on Fe-based binary alloys exposed to Cl-rich environment

International Nuclear Information System (INIS)

Konishi, Hiroyuki; Mizuki, Jun'ichiro; Yamashita, Masato; Uchida, Hitoshi

2005-01-01

The rust layer formed on weathering steel possesses a strong protective ability against corrosives in an atmospheres. This ability is related to the structure of the rust layer. The difference in the protective ability of a rust layer. The difference in the protective ability of a rust layer in a Cl-rich environment between conventional weathering steel containing Cr and advanced weathering steel containing Ni is believed to be caused by the differences in local structural and chemical properties between alloying elements. Cr and Ni, in the rust layer. In order to examine the effect of these alloying elements on the structure of the rust layer formed on steel in a Cl-rich environment, we have performed Cr and Ni K-edge X-ray absorption near-edge structure (XANES) measurements for the rust layer of Fe-Cr and Fe-Ni binary alloys exposed to a Cl-rich atmosphere using synchrotron radiation. The results of the Cr K-edge XANES measurements for the rust layer of Fe-Cr binary alloys show that the atomic geometry around Cr depends on the concentration of Cr. Therefore, it is expected that the local structure around Cr in the rust layer is unstable. On the other hand, from the results of the Ni K-edge XANES measurements for the rust layer of Fe-Ni binary alloys. Ni is considered to be positioned at a specific site in the crystal structure of a constituent of the rust layer, such as akaganeite or magnetite. As a consequence, Ni negligibly interacts with Cl - ions in the rust layer. (author)

Production and characterization of stainless steel based Fe-Cr-Ni-Mn-Si(-Co) shape memory alloys

International Nuclear Information System (INIS)

Otubo, J.

1995-01-01

It is well known that the Fe based alloys can exhibit shape memory effect due to the γ to ε martensitic transformation. The effect may not be as striking as observed in the NiTi alloy but it might become attractive from the practical point of view. In this work, two compositions of Fe-Cr-Ni-Mn-Si(-Co) stainless steel based shape memory alloy, prepared by the VIM technique, will be presented. The results are good with shape recovery of 95% for a pre-strain of 4% after some training cycles. In terms of workability the alloys produced are worse than the usual AISI304. However, adjusting the thermo-mechanical processing, it is perfectly possible to produce wire as thin as 1,20mm in dia. or down. (orig.)

Creep behaviour of modified 9Cr-1Mo ferritic steel

International Nuclear Information System (INIS)

Choudhary, B.K.; Isaac Samuel, E.

2011-01-01

Creep deformation and fracture behaviour of indigenously developed modified 9Cr-1Mo steel for steam generator (SG) tube application has been examined at 823, 848 and 873 K. Creep tests were performed on flat creep specimens machined from normalised and tempered SG tubes at stresses ranging from 125 to 275 MPa. The stress dependence of minimum creep rate obeyed Norton's power law. Similarly, the rupture life dependence on stress obeyed a power law. The fracture mode remained transgranular at all test conditions examined. The analysis of creep data indicated that the steel obey Monkman-Grant and modified Monkman-Grant relationships and display high creep damage tolerance factor. The tertiary creep was examined in terms of the variations of time to onset of tertiary creep with rupture life, and a recently proposed concept of time to reach Monkman-Grant ductility, and its relationship with rupture life that depends only on damage tolerance factor. SG tube steel exhibited creep-rupture strength comparable to those reported in literature and specified in the nuclear design code RCC-MR.

Microstructural Variations Across a Dissimilar 316L Austenitic: 9Cr Reduced Activation Ferritic Martensitic Steel Weld Joint

Science.gov (United States)

Thomas Paul, V.; Karthikeyan, T.; Dasgupta, Arup; Sudha, C.; Hajra, R. N.; Albert, S. K.; Saroja, S.; Jayakumar, T.

2016-03-01

This paper discuss the microstructural variations across a dissimilar weld joint between SS316 and 9Cr-RAFM steel and its modifications on post weld heat treatments (PWHT). Detailed characterization showed a mixed microstructure of austenite and martensite in the weld which is in agreement with the phases predicted using Schaeffler diagram based on composition measurements. The presence of very low volume fraction of δ-ferrite in SS316L has been identified employing state of the art electron back-scattered diffraction technique. PWHT of the ferritic steel did not reduce the hardness in the weld metal. Thermal exposure at 973 K (700 °C) showed a progressive reduction in hardness of weld joint with duration of treatment except in austenitic base metal. However, diffusion annealing at 1073 K (800 °C) for 100 hours resulted in an unexpected increase in hardness of weld metal, which is a manifestation of the dilution effects and enrichment of Ni on the transformation characteristics of the weld zone. Migration of carbon from ferritic steel aided the precipitation of fine carbides in the austenitic base metal on annealing at 973 K (700 °C); but enhanced diffusion at 1073 K (880 °C) resulted in coarsening of carbides and thereby reduction of hardness.

Irradiation performance of 9--12 Cr ferritic/martensitic stainless steels and their potential for in-core application in LWRs

International Nuclear Information System (INIS)

Jones, R.H.; Gelles, D.S.

1993-08-01

Ferritic-martensitic stainless steels exhibit radiation stability and stress corrosion resistance that make them attractive replacement materials for austenitic stainless steels for in-core applications. Recent radiation studies have demonstrated that 9% Cr ferritic/martensitic stainless steel had less than a 30C shift in ductile-to-brittle transition temperature (DBTT) following irradiation at 365C to a dose of 14 dpa. These steels also exhibit very low swelling rates, a result of the microstructural stability of these alloys during radiation. The 9 to 12% Cr alloys to also exhibit excellent corrosion and stress corrosion resistance in out-of-core applications. Demonstration of the applicability of ferritic/martensitic stainless steels for in-core LWR application will require verification of the irradiation assisted stress corrosion cracking behavior, measurement of DBTT following irradiation at 288C, and corrosion rates measurements for in-core water chemistry

Electrochemical impedance spectrometry using 316L steel, hastelloy, maraging, Inconel 600, Elgiloy, carbon steel, TiN and NiCr. Simulation in tritiated water. 2 volumes; Spectrometrie d`impedance electrochimique sur acier 316L, hastelloy, maraging inconel 600, elgiloy, acier au carbone, TiN, NiCr. Simulations en eau tritiee. 2 volumes

Energy Technology Data Exchange (ETDEWEB)

Bellanger, G.

1994-03-01

Polarization and electrochemical impedance spectrometry curves are presented and discussed. These curves make it possible to ascertain the corrosion domains and to compare the slow and fast kinetics (voltammetry) of different stainless steel alloys. These corrosion kinetics, the actual or simulated tritiated water redox potentials, and the corrosion potentials provide a classification of the steels studied here: 316L, Hastelloy, Maraging, Inconel 600, Elgiloy, carbon steel and TiN and NiCr deposits. From the results it can be concluded that Hastelloy and Elgiloy have the best corrosion resistance. (author). 49 refs., 695 figs., tabs.

Physical properties of molten core materials: Zr-Ni and Zr-Cr alloys measured by electrostatic levitation

Energy Technology Data Exchange (ETDEWEB)

Ohishi, Yuji, E-mail: ohishi@see.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University (Japan); Kondo, Toshiki [Graduate School of Engineering, Osaka University (Japan); Ishikawa, Takehiko [Japan Aerospace Exploration Agency (Japan); SOKEN-DAI (Graduate University for Advanced Studies) (Japan); Okada, Junpei T. [Institute for Materials Research, Tohoku University (Japan); Watanabe, Yuki [Advanced Engineering Services Co. Ltd. (Japan); Muta, Hiroaki; Kurosaki, Ken [Graduate School of Engineering, Osaka University (Japan); Yamanaka, Shinsuke [Graduate School of Engineering, Osaka University (Japan); Research Institute of Nuclear Engineering, University of Fukui (Japan)

2017-03-15

It is important to understand the behaviors of molten core materials to investigate the progression of a core meltdown accident. In the early stages of bundle degradation, low-melting-temperature liquid phases are expected to form via the eutectic reaction between Zircaloy and stainless steel. The main component of Zircaloy is Zr and those of stainless steel are Fe, Ni, and Cr. Our group has previously reported physical property data such as viscosity, density, and surface tension for Zr-Fe liquid alloys using an electrostatic levitation technique. In this study, we report the viscosity, density, and surface tension of Zr-Ni and Zr-Cr liquid alloys (Zr{sub 1-x}Ni{sub x} (x = 0.12 and 0.24) and Zr{sub 0.77}Cr{sub 0.23}) using the electrostatic levitation technique. - Highlights: • The physical properties of Zr-Ni and Zr-Cr liquid alloys have been measured Zr{sub 1-x}Ni{sub x} (x = 0.12 and 0.24) and Zr{sub 77}Cr{sub 23}. • The measurement was conducted using the electrostatic levitation technique. • The density, viscosity, and surface tension of each liquid alloy were measured.

Physical properties of molten core materials: Zr-Ni and Zr-Cr alloys measured by electrostatic levitation

International Nuclear Information System (INIS)

Ohishi, Yuji; Kondo, Toshiki; Ishikawa, Takehiko; Okada, Junpei T.; Watanabe, Yuki; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke

2017-01-01

It is important to understand the behaviors of molten core materials to investigate the progression of a core meltdown accident. In the early stages of bundle degradation, low-melting-temperature liquid phases are expected to form via the eutectic reaction between Zircaloy and stainless steel. The main component of Zircaloy is Zr and those of stainless steel are Fe, Ni, and Cr. Our group has previously reported physical property data such as viscosity, density, and surface tension for Zr-Fe liquid alloys using an electrostatic levitation technique. In this study, we report the viscosity, density, and surface tension of Zr-Ni and Zr-Cr liquid alloys (Zr 1-x Ni x (x = 0.12 and 0.24) and Zr 0.77 Cr 0.23 ) using the electrostatic levitation technique. - Highlights: • The physical properties of Zr-Ni and Zr-Cr liquid alloys have been measured Zr 1-x Ni x (x = 0.12 and 0.24) and Zr 77 Cr 23 . • The measurement was conducted using the electrostatic levitation technique. • The density, viscosity, and surface tension of each liquid alloy were measured.

Fatigue Properties of Aged Mod. 9Cr-1Mo

International Nuclear Information System (INIS)

Kim, Dae Whan; Kim, Sung Ho; Lee, Chan Bock

2007-01-01

Ferritic/Martensitic steel has a good mechanical properties and a lower thermal expansion coefficient than austenitic stainless steel. Mechanical property of Mod. 9Cr-1Mo steel is less than austenitic stainless steel at high temperature. High temperature mechanical properties are affected by precipitation for Mod. 9Cr-1Mo. FMS steel is used for long time at high temperature and the effect of aging on mechanical properties is very important. In this study, low cycle fatigue properties with aging were investigated

Evaluation of rolling contact fatigue of induction heated 13Cr-2Ni-2Mo Stainless steel bar with Si3N4-ball

Science.gov (United States)

Yadoiwa, Ariyasu; Mizobe, Koshiro; Kida, Katsuyuki

2018-03-01

13Cr % martensitic stainless steels were used in various industry, because they have excellent corrosion resistance and high hardness among other stainless steels. They are also expected as a bearing material, however, the research on rolling contact fatigue (RCF) is not enough. In this study, 13Cr-2Ni-2Mo stainless steels were quenched by induction heating and their RCF lives were evaluated. A Si3N4-ball was used in order to apply higher stress (Pmax = 5.6 GPa) than our previous tests (Pmax=5.3 GPa), in a single-ball RCF testing machine. It was found that the basic life (L10) was 2.20×106 cycles and Median life (L50) was 6.04×106 cycles. In addition, Weibull modulus became higher than the previous tests.

Alloy Design of Martensitic 9Cr-Boron Steel for A-USC Boiler at 650 °C — Beyond Grades 91, 92 and 122

Science.gov (United States)

Abe, Fujio; Tabuchi, M.; Tsukamoto, S.

Boundary hardening is shown to be the most important strengthening mechanism in creep of tempered martensitic 9% Cr steel base metal and welded joints at 650 °C. The enrichment of soluble boron near prior austenite grain boundaries (PAGBs) by the GB segregation is essential for the reduction of coarsening rate of M23C6 carbides near PAGBs, enhancing the boundary and sub-boundary hardening near PAGBs, and also for the change in α/γ transformation behavior in heat-affected-zone (HAZ) of welded joints during heating of welding, producing the same microstructure in HAZ as in the base metal. Excess addition of nitrogen to the 9Cr-boron steel promotes the formation of boron nitrides during normalizing heat treatment, which consumes most of soluble boron and degrades the creep strength. A NIMS 9Cr steel (MARBN; Martensitic 9Cr steel strengthened by boron and MX nitrides) with 120-150 ppm boron and 60-90 ppm nitrogen, where no boron nitride forms during normalizing heat treatment, exhibits not only much higher creep strength of base metal than Grades 91, 92 and 122 but also substantially no degradation in creep strength due to Type IV fracture in HAZ of welded joints at 650°C. The protective Cr2O3-rich scale forms on the surface of 9Cr steel by pre-oxidation treatment in Ar gas, which significantly improves the oxidation resistance in steam at 650°C.

Soft zone formation in dissimilar welds between two Cr-Mo steels

International Nuclear Information System (INIS)

Albert, S.K.; Gill, T.P.S.; Tyagi, A.K.; Mannan, S.L.; Rodriguez, P.; Kulkarni, S.D.

1997-01-01

Two dissimilar weldments between 9Cr-1Mo and 2.25Cr-1Mo ferritic steels have been characterized for their microstructural stability during various postweld heat treatments (PWHTs). The samples for the investigation were extracted from bead-on-plate weldments made by depositing 2.25Cr-1Mo weld metal on 9Cr-1Mo base plate and vice versa. Subsequent application of PWHT resulted in the formation of a soft zone in the low Cr ferritic steel weld or base plate. A carbide-rich hard zone, adjoining the soft zone, was also detected in the high Cr side of the weldment. Unmixed zones in the weld metal provided additional soft and hard zones in the weld metals. The migration of carbon from low-Cr steel to high-Cr steel, driven by the carbon activity gradient, has been shown to be responsible for the formation of soft and hard zones. A carbon activity diagram for 2.25Cr-1Mo/9Cr-1Mo weldments has been proposed to aid in the selection of welding consumables for reducing or preventing the soft zone formation

Grain boundary segregation in FeCrNi model alloys; Korngrenzensegregation in FeCrNi-Modellegierungen

Energy Technology Data Exchange (ETDEWEB)

Schlueter, B.; Schneider, F.; Mummert, K. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany); Muraleedharan, P. [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Div. of Metallurgy

1998-12-31

P and S segregate at the grain boundaries and thus increase susceptibility to intergranular corrosion at those sites. This could be proven by means of nitric acid-chromate tests and potentiostatic etching tests. There is a direct connection between loss in mass, mean depth of intergranular corrosion attacks, dissolution current density, and level of segregation-induced concentration of P and S at the grain boundaries. The segregation effect at these sites was found to be most evident in specimens of the examined Fe-Cr-Ni steel which had been heat-treated for 1000 hours at 550 C. However, segregation occurs also in materials that received a heat treatment of 400 C/5000 hours, while intergranular corrosion is observed only after heat treatment of 500 C/1000 hours. Apart from segregation of P, formation of Cr-rich phosphides is observed, which leads to depletion of Cr at the precipitates. (orig./CB) [Deutsch] P und S segregieren an die KG und erhoehen dort die IK-Anfaelligkeit. Dies konnte mit Hilfe von Salpetersaeure-Chromat- und Potentiostatischem Aetztest nachgewiesen werden. Es besteht ein direkter Zusammenhang zwischen Masseverlust, mittlerer IK-Angriffstiefe, Aufloesungsstromdichte und Hoehe der segregationsbedingten Anreicherungen von P und S an den KG. Der KG-Segregationseffekt am untersuchten Fe-Cr-Ni-Stahl ist im Waermebehandlungszustand 550 C/1000 h am deutlichsten ausgepraegt. Aber auch bereits bei 400 C/5000 h findet Segregation statt. IKSpRK tritt nur im Waermebehandlungszustand 550 C/1000 h auf. Neben der P-Segregation wird die Bildung Cr-reicher Phosphide beobachtet, die zur Abreicherung von Cr an den Ausscheidungen fuehrt. (orig.)

Microstructural evolution in austenitic heat-resistant cast steel 35Cr25Ni12NNbRE during long-term service

International Nuclear Information System (INIS)

Liu Jiangwen; Jiao Dongling; Luo Chengping

2010-01-01

The microstructural evolution of austenitic heat-resistant cast steel 35Cr25Ni12NNbRE during aging and long-term service was investigated using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The microstructure of the as cast steel consists of the dendritic austenite, the block-like eutectic carbide M 7 C 3 spreaded among austenitic dendrite, and a small quantity of M 23 C 6 carbide. The microstructure of the steel aged at 600 deg. C consists of eutectic carbide M 23 C 6 transformed from eutectic carbide M 7 C 3 and dendritic austenite in which fine secondary carbide particles M 23 C 6 precipitated. The precipitated carbide M 23 C 6 kept a cubic-cubic orientation relationship (OR) with austenite matrix. There existed a carbide precipitation free zone (PFZ) around the eutectic carbide. For the long-term serviced samples, the secondary carbide precipitated in the austenite strikingly increased and the PFZ disappeared. Part of the M 23 C 6 transformed into M 6 C, which always kept a twin OR, [114] M 6 C //[110] A //[110] M 23 C 6 , with the austenite and the M 23 C 6 secondary carbide. In addition, a small quantity of σ phase FeCr and ε-Cr 2 N were also identified. The effects of alloy composition and service condition on the microstructural evolution of the steel were discussed.

Effects of iron spallation products Ti, P and S on the physical metallurgy of 9Cr martensitic steels

International Nuclear Information System (INIS)

Danylova, O.; Carlan, Y. de; Hamon, D.; Brachet, J.C.; Alamo, A.

2002-01-01

The design of an Accelerator Driven System (ADS) requires that the 'window', which separates the proton accelerator from the spallation target, be able to withstand very severe irradiation conditions. Fe-9/12Cr martensitic steels are good candidates for the window material due to their intrinsic stability under neutron irradiation, but the influence of iron spallation elements on their behaviour is not known. To elucidate the effects of the spallation elements titanium, phosphorus and sulphur on the behaviour of martensitic steels, it was decides to obtain different castings of 9Cr 1Mo steels doped with these elements. The aim of this paper is to present the data obtained on the physical metallurgy of these steels and to show the possible methods of obtaining titanium, phosphorus and sulphur in solid solution for subsequent study of the evolution of the microstructure and mechanical properties. (authors)

Heat treated 9 Cr-1 Mo steel material for high temperature application

Science.gov (United States)

Jablonski, Paul D.; Alman, David; Dogan, Omer; Holcomb, Gordon; Cowen, Christopher

2012-08-21

The invention relates to a composition and heat treatment for a high-temperature, titanium alloyed, 9 Cr-1 Mo steel exhibiting improved creep strength and oxidation resistance at service temperatures up to 650.degree. C. The novel combination of composition and heat treatment produces a heat treated material containing both large primary titanium carbides and small secondary titanium carbides. The primary titanium carbides contribute to creep strength while the secondary titanium carbides act to maintain a higher level of chromium in the finished steel for increased oxidation resistance, and strengthen the steel by impeding the movement of dislocations through the crystal structure. The heat treated material provides improved performance at comparable cost to commonly used high-temperature steels such as ASTM P91 and ASTM P92, and requires heat treatment consisting solely of austenization, rapid cooling, tempering, and final cooling, avoiding the need for any hot-working in the austenite temperature range.

The kinetics of phase transformations of undercooled austenite of the 38MnCrNi6-4-4 hypoeutectoid steel

OpenAIRE

R. Dąbrowski; R. Dziurka; E. Rożniata

2012-01-01

Purpose: Present work corresponds to the research on the kinetic of phase transformation of undercooled austenite of 38MnCrNi6-4-4 hypoeutctoid steel. The kinetic of phase transformation of under cooled austenite of investigated alloy was presented on CCT diagram (continuous cooling transformation). Also the methodology of a dilatometric samples preparation and the method of the critical points determination were described.Design/methodology/approach: The austenitising temperature was defined...

Creep behaviour of the alloys NiCr22Co12Mo and 10CrMo9 10 under static and cyclic load conditions

International Nuclear Information System (INIS)

Wolf, H.

1990-01-01

The creep behaviour of NiCr20Co12Mo is investigated under static strain and at 800deg C, with stresses applied ranging from 105 MPa to 370 MPa. The ferritic steel 10CrMo 9 10 is tested for its creep behaviour under static strain and at the temperatures of 600deg C and 550deg C, with stresses applied between 154 MPa and 326 MPa (at 600deg C), or between 250 MPa and 458 MPa (at 550deg C). The experiments are made to determine the effects of changes in strain on the materials' deformation behaviour, placing emphasis on transient creep and elastic or anelastic response. The mean internal stress is determined from changes in strain. Cyclic creep is analysed as a behaviour directly responding to the pattern of change in strain. Effects of certain strain changes not clarified so far are analysed. The cyclic strain experiments are analysed according to the velocity factor concept. The usual models of creep deformation (theta projection concept) are compared with the model of effective strain, which is based on the fundamental equation of plastic deformation by dislocation motion (Orowan equation). (MM) [de

Recovery and Precipitate Analysis of 9 Pct Cr-1 Pct MoVNb Steel during Creep

NARCIS (Netherlands)

Kabadwal, A.; Tamura, M.; Shinozuka, K.; Esaka, H.

The effect of tempering temperature and creep exposure on the microstructure of a modified 9Cr steel was investigated. Creep-interrupted specimens, including the grip portion, were investigated precisely using mainly X-ray and inductively coupled plasma (ICP) spectroscopy. After saturation of

9% Cr steel high temperature oxidation. Solutions investigated for improving corrosion resistance of the steel

Energy Technology Data Exchange (ETDEWEB)

Evin, Harold Nicolas; Heintz, Olivier; Chevalier, Sebastien [UMR 5209 CNRS-Bourgogne Univ. (France). Lab. Interdisciplinaire Carnot de Bourgogne; Foejer, Cecilia; Jakani, Saad; Dhont, Annick; Claessens, Serge [OCAS N.V. ArcelorMittal Global R and D, Gent (Belgium)

2010-07-01

The improvement of high temperature oxidation resistance of low chromium content steels, such as T/P91, is of great interest in regards with their application in thermal power generating plants. Indeed, they possess good creep properties, but are facing their limits of use at temperature higher than 600 C, due to accelerated corrosion phenomena. Good knowledge of the mechanisms involved during their oxidation process is needed to prevent the degradation of the materials and to extend life time of the power plants components. Oxide layers thermally grown, on 9% Cr steels (provided by OCAS N.V), during isothermal tests between 600 C and 750 C in laboratory air under atmospheric pressure were investigated, by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The oxidation behaviour appeared very limited at 750 C, due to the presence of a breakaway, which can be linked to iron porous oxide grown over the surface of the samples. ''In situ'' X-ray Photoelectron spectroscopy (XPS) analyses were performed in air at 600 C after short exposures (between 5 min and 25 h). A complex mixture of iron oxide, Cr{sub 2}O{sub 3} and Cr (VI) species were characterized in the scales. The in-situ analyses were compared and related to XPS analyses performed on thick oxide scales formed on samples oxidized in air at 600 C for 100h. An oxidation mechanism is then proposed to understand the oxide scale growth in the temperature range 600 - 750 C. The second step of this study consists in improving the high temperature corrosion resistance of these steels without modifying their mechanical properties. Thus several solutions were investigated such as MOCVD coatings, pack cementation coatings, and tested in cycle conditions prior. (orig.)

Development of the dentistry alloy Ni-Cr-Nb; Desenvolvimento de ligas odontologicas Ni-Cr-Nb

Energy Technology Data Exchange (ETDEWEB)

Souza, M.A.; Ramos, A.S.; Hashimoto, T.M., E-mail: mari_sou@hotmail.co [UNESP/FEG, Guaratingueta, SP (Brazil). Fac. de Engenharia. Dept. de Materiais e Tecnologia

2010-07-01

This work reports on the structural characterization of Ni-Cr-Mo and Ni-Cr-Nb alloys produced by arc melting. Samples were characterized by means of optical microscopy, X-ray diffraction, scanning electron microscopy, and EDS analysis. Results indicated that the arc melting process was efficient to produce homogeneous structures in Ni-Cr-Mo and Ni-Cr-Nb alloys. The nickel dissolved large amounts of Cr, Mo and Nb, which was detected by EDS analysis and X-ray diffraction. The alloy containing molybdenum indicated the presence of structure based on Ni{sub SS}, while that the alloys containing niobium presented primary grains of Ni{sub SS} and precipitates formed by the simultaneous transformation of the Ni and Ni{sub 3}Nb phases. (author)

Influence of cooling rates on the transformation behaviour of 9Cr-1Mo-0.07C steel

International Nuclear Information System (INIS)

Saroja, S.; Vijayalakshmi, M.; Raghunathan, V.S.

1992-01-01

The choice of various decomposition mechanisms of austenite in a 9Cr-1 Mo-0.07C steel under different rates of cooling has been studied. The techniques employed were electron probe micro-analysis, X-ray diffraction and electron microscopy. The observed morphological features may be explained based on the predominance of the two types of transformation, austenite → martensite and austenite → ferrite during cooling. In the steel used in this study, decomposition of austenite to proeutectoid ferrite was favoured at cooling rates less than about 2 Ks -1 . The mechanism by which the supersaturated proeutectoid ferrite relieves its excess solute concentration was also studied. A ''microstructural map'' has been proposed to predict the constitution at the end of any given cooling rate for 9Cr-1 Mo-0.07C steel. The choice of commercial treatment has been rationalized with respect to the resultant microstructural constituents. (Author)

Hardness and Wear Resistance of TiC-Fe-Cr Locally Reinforcement Produced in Cast Steel

Directory of Open Access Journals (Sweden)

Olejnik E.

2016-06-01

Full Text Available In order to increase wear resistance cast steel casting the TiC-Fe-Cr type composite zones were fabricated. These zones were obtained by means of in situ synthesis of substrates of the reaction TiC with a moderator of a chemical composition of white cast iron with nickel of the Ni-Hard type 4. The synthesis was carried out directly in the mould cavity. The moderator was applied to control the reactive infiltration occurring during the TiC synthesis. The microstructure of composite zones was investigated by electron scanning microscopy, using the backscattered electron mode. The structure of composite zones was verified by the X-ray diffraction method. The hardness of composite zones, cast steel base alloy and the reference samples such as white chromium cast iron with 14 % Cr and 20 % Cr, manganese cast steel 18 % Mn was measured by Vickers test. The wear resistance of the composite zone and the reference samples examined by ball-on-disc wear test. Dimensionally stable composite zones were obtained containing submicron sizes TiC particles uniformly distributed in the matrix. The macro and microstructure of the composite zone ensured three times hardness increase in comparison to the cast steel base alloy and one and a half times increase in comparison to the white chromium cast iron 20 % Cr. Finally ball-on-disc wear rate of the composite zone was five times lower than chromium white cast iron containing 20 % Cr.

Microstructural evolution and creep behaviour of the modified 9% Cr steel with boron and cobalt

International Nuclear Information System (INIS)

Nowakowski, P.; Spiradek-Hahn, K.; Brabetz, M.; Zeiler, G.

1998-01-01

In the present study the microstructural evolution of the new 9% Cr with boron and cobalt is shown during creep at 650 o C. The minimum creep rates of the new alloy are significantly lower than those of conventional 12 % Cr steel. This is due to the high stability of M 23 C 6 precipitates with respect to the coarsening and the preservation of high dislocation density in the course of creep exposure. (author)

Optimization of consolidation parameters of 18Cr-ODS ferritic steel through microstructural and microtexture characterization

Science.gov (United States)

Dash, Manmath Kumar; Mythili, R.; Dasgupta, Arup; Saroja, S.

2018-04-01

This paper reports the optimization of consolidation process based on the evolution of microstructure, microtexture and densification in 18%-Cr Oxide Dispersion Strengthened steel. The steel powder of composition Fe-18Cr-0.01C-2W-0.25Ti-0.35Y2O3 has been consolidated by cold isostatic pressing (CIP) for green compaction after mechanical milling. Sintering (1000-1250 °C) and hot isostatic pressing (HIP) at 1150 °C has been employed to achieve good densification on compacted CIP specimen. The effect of sintering temperatures on densification behavior was evaluated and sintering at 1150°C was identified to be optimum for achieving good compaction (92% density) and homogeneous polygonal microstructure with a uniform distribution of fine pores. In addition, HIP of CIP product at 1150°C was found to yield a more homogeneous microstructure as compared to sintered product with 97% density. A static/dynamic recrystallization associated with (1 1 1) texture is observed during consolidation process. A statistical comparison has been made based on frequency of grain boundary distribution and associated texture with its theoretical attributes.

Tribological Properties of HVOF-Sprayed TiB2-NiCr Coatings with Agglomerated Feedstocks

Science.gov (United States)

Zhao, Zichun; Li, Hui; Yang, Tianlong; Zhu, Hongbin

2018-04-01

Boride materials have drawn great attention in surface engineering field, owing to their high hardness and good wear resistance. In our previous work, a plasma-sprayed TiB2-based cermet coating was deposited, but the coating toughness was significantly influenced by the formation of a brittle ternary phase (Ni20Ti3B6) derived from the reaction between TiB2 and metal binder. In order to suppress such a reaction occurred in the high-temperature spraying process, the high-velocity oxygen-fuel spraying technique was applied to prepare the TiB2-NiCr coating. Emphasis was paid on the microstructure, the mechanical properties, and the sliding wearing performance of the coating. The result showed that the HVOF-sprayed coating mainly consisted of hard ceramic particles including TiB2, CrB, and the binder phase. No evidence of Ni20Ti3B6 phase was found in the coating. The mechanical properties of HVOF-sprayed TiB2-NiCr coating were comparable to the conventional Cr3C2-NiCr coating. The frictional coefficient of the TiB2-NiCr coating was lower than the Cr3C2-NiCr coating when sliding against a bearing steel ball.

Tribological Properties of HVOF-Sprayed TiB2-NiCr Coatings with Agglomerated Feedstocks

Science.gov (United States)

Zhao, Zichun; Li, Hui; Yang, Tianlong; Zhu, Hongbin

2018-03-01

Boride materials have drawn great attention in surface engineering field, owing to their high hardness and good wear resistance. In our previous work, a plasma-sprayed TiB2-based cermet coating was deposited, but the coating toughness was significantly influenced by the formation of a brittle ternary phase (Ni20Ti3B6) derived from the reaction between TiB2 and metal binder. In order to suppress such a reaction occurred in the high-temperature spraying process, the high-velocity oxygen-fuel spraying technique was applied to prepare the TiB2-NiCr coating. Emphasis was paid on the microstructure, the mechanical properties, and the sliding wearing performance of the coating. The result showed that the HVOF-sprayed coating mainly consisted of hard ceramic particles including TiB2, CrB, and the binder phase. No evidence of Ni20Ti3B6 phase was found in the coating. The mechanical properties of HVOF-sprayed TiB2-NiCr coating were comparable to the conventional Cr3C2-NiCr coating. The frictional coefficient of the TiB2-NiCr coating was lower than the Cr3C2-NiCr coating when sliding against a bearing steel ball.

Residual stress determination by neutron diffraction in a car gear-shaft made of 20NiCrMo2 alloyed case hardening steel

Czech Academy of Sciences Publication Activity Database

Rogante, M.; Mazzanti, M.; Mikula, Pavol; Vrána, Miroslav

2012-01-01

Roč. 50, č. 4 (2012), s. 213-220 ISSN 0023-432X R&D Projects: GA ČR(CZ) GAP204/12/1360 Institutional support: RVO:61389005 Keywords : 20NiCrMo2 steel * gear-shaft * caser hardening * residual stress * neutron diffraction Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 0.687, year: 2012

Reduced-activation austenitic stainless steels: The Fe--Mn--Cr--C system

International Nuclear Information System (INIS)

Klueh, R.L.; Maziasz, P.J.

1988-01-01

Nickel-free manganese-stabilized steels are being developed for fusion-reactor applications. As the first part of this effort, the austenite-stable region in the Fe--Mn--Cr--C system was determined. Results indicated that the Schaeffler diagram developed for Fe--Ni--Cr--C alloys cannot be used to predict the constituents expected for high-manganese steels. This is true because manganese is not as strong an austenite stabilizer relative to δ-ferrite formation as predicted by the diagram, but it is a stronger austenite stabilizer relative to martensite than predicted. Therefore, the austenite-stable region for Ne--Mn--Cr--C alloys occurs at lower chromium and hugher combinations of manganese and carbon than predicted by the Schaeffler diagram. Development of a manganese-stabilized stainless steel should be possible in the composition range of 20 to 25% Mn, 10 to 15% Cr, and 0.01 to 0.25%C. Tensile behavior of an Fe--20%Mn--12%Cr--0.25%C alloy was determined. The strength and ductility of this possible base composition was comparable to type 316 stainless steel in both the solution-annealed and cold-worked condition

Investigations on avoidance of hot cracks during laser welding of austenitic Cr-Ni steels and nickel-based alloys using temperature field tailoring. Final report; Untersuchungen zur Vermeidung von Heissrissen beim Laserstrahlschweissen von austenitischen Cr-Ni-Staehlen und Nickelbasislegierungen mittels Temperaturfeld-Tailoring. Schlussbericht

Energy Technology Data Exchange (ETDEWEB)

NONE

2013-08-08

The aim of the project was to transfer the developed method of laser beam welding of heat treated machining steels of temperature field tailoring on hot crack endangered austenitic Cr-Ni steels and nickel-based alloys. With this method, transient thermal stresses adjacent to the weld are produced by an travelling induction heating so that the hot cracking is prevented during welding. As test materials the austenitic Cr-Ni steel with sulfur additive 1.4305, the Cr-Ni steels 1.4404 and 1.4435 and the nickel-based alloy Udimet 720 were selected. As a result of the research it was shown that a hot crack-free laser welding in the investigated materials using at least three different welding and material-technical approaches is possible. [German] Das Ziel des Forschungsvorhabens bestand darin, das fuer das Laserstrahlschweissen verguetbarer Automatenstaehle entwickelte Verfahren des Temperaturfeld-Tailorings auf heissrissgefaehrdete austenitische Cr-Ni-Staehle und Nickelbasislegierungen zu uebertragen. Mit diesem Verfahren werden waehrend des Schweissens transiente thermische Spannungen neben der Schweissnaht durch eine mitlaufende induktive Erwaermung so erzeugt, dass die Heissrissbildung verhindert wird. Als Versuchswerkstoffe wurden der austenitische Cr-Ni-Stahl mit Schwefelzusatz 1.4305, die Cr-Ni-Staehle 1.4404 und 1.4435 sowie die Nickelbasislegierung Udimet 720 ausgewaehlt. Im Ergebnis des Forschungsvorhabens konnte gezeigt werden, dass ein heissrissfreies Laserstrahlschweissen bei den untersuchten Werkstoffen unter Nutzung von mindestens drei verschiedenen schweiss- und werkstofftechnischen Ansaetzen moeglich ist: Erstens koennen mit einem Temperaturfeld-Tailoring bei im Stumpfstoss zu verschweissenden Blechen aus austenitischen Staehlen bis mindestens 6 mm Dicke senkrecht zur Naht und parallel zur Blechoberflaeche wirkende transiente Druckspannungen erzeugt werden, die der Bildung von Mittelrippenrissen oder dazu parallel liegenden Heissrissen entgegenwirken

The oxidation behaviour of Fe-9Cr-1Mo steels

International Nuclear Information System (INIS)

Rowlands, P.C.; Holmes, D.R.; Whittaker, A.; Brierley, R.A.; Garrett, J.C.P.

1983-01-01

The oxidation behaviour of Fe9Cr1Mo steels over a wide range of conditions covering likely operating environments has been determined. In particular the effects of temperature, gas composition and materials variables on production materials have been investigated. From this work the mechanisms of protective and breakaway corrosion have broadly been elucidated. The vital role of carbon deposition in the oxide and carburisation of the metal has been determined. Aspects of the breakaway and protective oxidation mechanisms have been incorporated into a statistical model for predicting breakaway initiation and boiler component life. The results obtained from the tube life calculations indicate very low probabilities of component failure for coolant gas compositions containing up to the equivalent of 825 vppm H 2 O and 1%CO. For a more aggressive gas at the upper limit of CO concentration (2%CO) there is a small probability of failure within 25 years for finned boiler tubes. Current work may in time allow these constraints composition to be relaxed. The information gained has been used in the design of Heysham II/Torness to reduce the probabilities of 9Cr component failure to insignificant levels. (author)

Creep and time to rupture of a 16/16 Cr Ni Steel; Comportamiento a la fluencia lenta de la aleacion X 8 Cr Ni Mo Nb 1616 con distintos tratamientos termicos

Energy Technology Data Exchange (ETDEWEB)

Solano, R; Garcia, R; Bohm, H; Schirra, M

1972-07-01

The influence of different thermal-mechanical treatments on the creep and time to rupture of a 16/16 Cr.Ni steel is studied. The solution treated material after annealing at 700-800 degree centigree did not affect time to rupture. At the contrary a 12% cold-working and annealing at 800 degree centigree improve the time to rupture. This treatment is preserved up to 700 degree centigree 10{sup 4} hours. The ductility is not strongly affected. A metallographic study of the fracture was carried out. (Author) 23 refs.

Initial study on Z-phase strengthened 9-12% Cr steels by atom probe tomography

Energy Technology Data Exchange (ETDEWEB)

Liu, Fang; Andren, Hans-Olof [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Applied Physics

2010-07-01

The microstructure of two different types of Z-phase strengthened experimental steels, CrNbN-based or CrTaN-based, was investigated. Both steels underwent aging at 650 C for relatively short period of time, 24 hours or 1005 hours. Atom probe tomography was used to study the chemical composition of the matrix and precipitates, and the size and number density of the small precipitates. Both steels contain Laves phase at prior austenite grain boundaries and martensitic lath boundaries. The CrTaN-based steel was found more promising due to its finer and more densely distributed precipitates after 1005 hour aging. (orig.)

Influence of dynamic sodium environment on the creep-fatigue behaviour of Modified 9Cr-1Mo ferritic-martensitic steel

International Nuclear Information System (INIS)

Kannan, R.; Ganesan, V.; Mariappan, K.; Sukumaran, G.; Sandhya, R.; Mathew, M.D.; Bhanu Sankara Rao, K.

2011-01-01

Highlights: → The effects of dynamic sodium on the CFI behaviour of Mod. 9Cr-1Mo steel has investigated. → The cyclic stress response of Mod. 9Cr-1Mo steel under flowing sodium environment is similar to that of air environment. → The creep-fatigue endurance of the alloy is found to decrease with introduction of hold time and with increase in the duration of hold time and the factor of life increase in sodium compared to air environment is reduced with increase in hold time. → In contrast to air environment, tensile holds were found to be more damaging than compression hold in sodium environment. → Design rules based on air environment can be safely applied for the components operating in sodium environment. - Abstract: The use of liquid sodium as a heat transfer medium for sodium-cooled fast reactors (SFRs) necessitates a clear understanding of the effects of dynamic sodium on low cycle fatigue (LCF), creep and creep-fatigue interaction (CFI) behaviour of reactor structural materials. Mod. 9Cr-1Mo ferritic steel is the material of current interest for the steam generator components of sodium cooled fast reactors. The steam generator has a design life of 30-40 years. The effects of dynamic sodium on the LCF and CFI behaviour of Mod. 9Cr-1Mo steel have been investigated at 823 and 873 K. The CFI life of the steel showed marginal increase under flowing sodium environment when compared to air environment. Hence, the design rules for creep-fatigue interaction based on air tests can be safely applied for components operating in sodium environment. This paper attempts to explain the observed LCF and CFI results based on the detailed metallography and fractography conducted on the failed samples.

Stainless steel corrosion in conditions simulating WWER-1000 primary coolant. Corrosion behaviour in mixed core

International Nuclear Information System (INIS)

Krasnorutskij, V.S.; Petel'guzov, I.A.; Gritsina, V.M.; Zuek, V.A.; Tret'yakov, M.V.; Rud', R.A.; Svichkar', N.V.; Slabospitskaya, E.A.; Ishchenko, N.I.

2011-01-01

Research into corrosion kinetics of austenitic stainless steels (06Cr18Ni10Ti, 08Cr18Ni10Ti, 12Cr18Ni10Ti) in medium which corresponds to composition and parameters of WWER-1000 primary coolant with different pH values in autoclave out-pile conditions during 14000 hours is given. Surface of oxide films on stainless steels is investigated. Visual inspection of Westinghouse and TVEL fuel was carried out after 4 cycles in WWER-1000 primary water chemistry conditions at South Ukraine NPP. Westinghouse and TVEL fuel cladding materials possess high corrosion resistance. Blushing of weldments was observed. No visual corrosion defects or deposits were observed on fuel rods.

Microchemistry of neutron irradiated 12%CrMoVNb martensitic steel

International Nuclear Information System (INIS)

Little, E.A.; Morgan, T.S.; Faulkner, R.G.

1992-01-01

Non-equilibrium solute segregation has been studied in a 12%CrMoVNb martensitic steel following fast reactor irradiation at 465 C and correlated with the development of M 6 X η-phase. Cr, Ni, Si, Mo, P and Mn are all shown to exhibit positive segregation to lath boundaries and are subsequently incorporated into M 6 X precipitates. The co-segregation of a combination of these elements which include P and Si, and possibly Cr or Mo, appears to promote M 6 X formation

Wear of Flame-Sprayed Ni-Cr-B-Si Powder Coating on Journal for Seal Contact

Directory of Open Access Journals (Sweden)

Hu Sheng-Yen

2016-01-01

Full Text Available Flame-sprayed techniques is used in this paper to coat Ni-Cr-B-Si powder on low-carbon steel or bearing steel materials of the journal surface. The wear tester is used to explore material properties of the binding capability, surface hardness, wear and friction within each layer depth. The normal force is applied in addition to the cladding layer by not only using bearing ball but also oil seal pieces, to explore rubber material of oil seal contact journal. In experiments to explore the material and processing conditions affect the microstructure and hardness of the cladding layer, and at the same hardness, surface roughness to affect the performance of the mill run.The results showed that spraying Ni-Cr-B-Si alloy powder in mild steel sheet to melt and run, cladding layer and the substrate has a uniform distribution of fine abrasive particles and binding effect, causing the substrate surface hardness (HRC about promotion 10 times. While, if sprayed Ni-Cr-B-Si alloy powder to steel panels bearing surface because the surface coated compact structure, can reduce the surface roughness and the coefficient of friction, and more improve the wear resistance of the cladding layer.

Impingement wastage experiments with 9Cr 1Mo steel

Energy Technology Data Exchange (ETDEWEB)

Kishore, S., E-mail: skishore@igcar.gov.in [IGCAR (India); Beauchamp, François; Allou, Alexandre [CEA (France); Kumar, A. Ashok; Chandramouli, S.; Rajan, K.K. [IGCAR (India)

2016-02-15

Highlights: • Sodium heated steam generators are crucial components of fast breeder reactors. • A leak in steam generator tube will cause sodium water reaction that damages the tubes. • A collaborative study by CEA and IGCAR was conducted to quantify the extent of damage on 9Cr 1Mo tube due to a steam/water leak. • It was compared against the predictions of PROPANA code. - Abstract: Steam Generator (SG) is one of the vital components of sodium cooled fast reactor (SFR). The main safety concern with SG is a probable sodium–water reaction. In case, one of its water/steam carrying tubes leaks, water/steam gets into contact with sodium causing sodium-water reaction, which is highly exothermic and producing corrosive NaOH and hydrogen. The ejecting reaction products at high temperature, impinges upon adjacent tubes by a process called impingement wastage. It could damage one of the neighboring tubes in a short time, if the detection and protection systems are failing. IGCAR and CEA carried out a collaborative study on impingement wastage of 9Cr 1Mo steel, which is one of the candidate materials for SFR SG tubes. The studies comprise of experimental works at IGCAR and simulation works with PROPANA code at CEA. This paper brings out the data and experience gained through this cooperative work.

Density of Liquid Ni-Cr Alloy

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

The density of liquid Ni-Cr alloy was measured by a modified sessile drop method. The density of liquid Ni-Cr alloywas found to decrease with increasing temperature and Cr concentration in the alloy. The molar volume of liquidNi-Cr alloy increases with increasing the Cr concentration in the alloy. The molar volume of Ni-Cr alloy determinedin the present work shows a positive deviation from the linear molar volume.

Boron Steel: An Alternative for Costlier Nickel and Molybdenum Alloyed Steel for Transmission Gears

Directory of Open Access Journals (Sweden)

A. Verma

2010-06-01

Full Text Available Case Carburized (CC low carbon steels containing Ni, Cr and Mo alloying elements are widely used for transmission gears in automobile, as it possesses desired mechanical properties. In order to cut cost and save scarce materials like Ni and Mo for strategic applications, steel alloyed with Boron has been developed, which gives properties comparable to Ni-Cr-Mo alloyed steel. In the process of steel development, care was taken to ensure precipitation of boron which results in precipitation hardening. The characterization of the developed boron steel had exhibited properties comparable to Ni-Cr-Mo alloyed steel and superior to conventional boron steel.

A comparison of low-chromium and high-chromium reduced-activation steels for fusion applications

International Nuclear Information System (INIS)

Klueh, R.L.; Maziasz, P.J.; Alexander, D.J.

1996-01-01

Ferritic steels have been considered candidate structural materials for first wall and blanket structures for fusion power plants since the late 1970s. The first steels considered in the United States were the conventional Cr-Mo steels Sandvik HT9 (nominally 12Cr-1Mo-0.25V-0.5W-0.5Ni-0.2C, here designated l2Cr-1MoVW), modified 9Cr-1Mo steel (9Cr-1Mo-0.2V-0.06Nb-0. IC, designated 9Cr-1MoVNb) and, to a lesser extent, 2 1/4Cr-1Mo steel (2.25Cr-Mo-0.1C). All compositions are in wt. %. The normalized-and-tempered 9 and 12Cr steels had a tempered martensite microstructure, and the normalized-and-tempered 2 1/4 Cr steel had a tempered bainite microstructure. This report describes chromium steels tested in normalized and tempered conditions. Miniature tensile and Charpy specimens were tested

The enhancement in wear resistance of W18Cr4V steel by ion implantation

International Nuclear Information System (INIS)

Zhou Ping; Xu Peiguang

1987-01-01

Two new methods of ion implantation were adopted in comparison with nitrogen implantation: carbon monoxide was implanted directly into W18Cr4V steel, and nitrogen was implanted into a deposited titanium film about 1000 A thick. It is shown that higher surface hardness and wear resistance have been achieved. The composition and phase structure of the implanted layer was determined in detail. The wear mechanisms were discussed

Preliminary results of effect of environment on the low cycle fatigue behaviour of type 316 stainless steel and 9% Cr ferritic steel

International Nuclear Information System (INIS)

Wood, D.S.; Slattery, G.F.; Wynn, J.; Connaughton, M.D.; Lambert, M.E.

1976-06-01

Strain controlled fatigue tests on Type 316 steel at 625 0 C and 9% Cr steel at 525 0 C have been performed in air and in helium containing 200 μ atm H 2 and 1 μ atm H 2 O. In rapid cycling the endurance of Type 316 steel in this helium mixture was found to be about five times longer than in air. When a hold time was introduced into the tension part of the cycle however the endurance in the two environments was found to be virtually identical. Fractomicrographic examinations have been performed which have helped to explain some of these findings which are attributed to differences in oxidation behaviour at the crack tip. In the case of the 90% Cr steel the endurance in the helium mixture was found to be only slightly better than in air. The implications of these results are considered in relation to thermal shock effects on sodium cooled fast reactor components. (author)

Low-field spin dynamics of Cr₇Ni and Cr₇Ni-Cu-Cr₇Ni molecular rings as detected by μsR

OpenAIRE

Sanna, S.; Arosio, P.; Bordonali, L.; Adelnia, F.; Mariani, M.; Garlatti, E.; Baines, C.; Amato, A.; Sabareesh, K. P.V.; Timco, G.; Winpenny, R. E.P.; Blundell, S. J.; Lascialfari, A.

2017-01-01

Muon spin rotation measurements were used to investigate the spin dynamics of heterometallic Cr7Ni and Cr7Ni-Cu-Cr7Ni molecular clusters. In Cr7Ni the magnetic ions are arranged in a quasiplanar ring and interact via an antiferromagnetic exchange coupling constant J, while Cr7Ni-Cu-Cr7Ni is composed of two Cr7Ni linked by a bridging moiety containing one Cu ion, that induces an inter-ring ferromagnetic interaction J ≪ J. The longitudinal muon relaxation rate λ collected at low magnetic fields...

A new and unusual deformation behavior observed in 12Cr18Ni10Ti stainless steel irradiated at 307 deg. C to 55 dpa in BN-350

International Nuclear Information System (INIS)

Gusev, M.; Maksimkin, O.; Osipov, I.S.; Garner, F.

2007-01-01

Full text of publication follows: It is currently accepted that neutron irradiation of stainless steels in general leads to increased strength, reduction of ductility and inevitably to embrittlement. The microstructural origins of such changes in mechanical behavior are well understood. Occasionally, however, a new phenomenon is observed at higher fluences. Void-induced embrittlement is an example whereby the ductility loss is strongly accelerated when new microstructural conditions develop from voids that cause stress concentration, removal of nickel from the matrix and thereby induce a martensitic transformation. This process occurs at moderately high temperatures where high void swelling can occur. It now appears that there is another, previously unobserved phenomenon that develops in austenitic steel irradiated to relatively high dose and relatively low temperature. In this case, however, the loss of plasticity commonly developed at lower dose is reversed and is replaced by an unusually high deformation. The plastic deformation was studied of miniature flat tensile specimens of 12Cr18Ni10Ti austenitic steel cut from a fuel assembly wrapper irradiated in the BN-350 reactor to 55 dpa at 580 K (307 deg. C). A new optical extensometry technique was employed that uses a video camera and multiple tiny markers painted on the specimen, allowing visualization and recording of the strain distribution as it develops along the specimen. The total deformation derived from the engineering diagrams for these specimens was 35-40%, while 3-7% was expected from previous studies conducted at lower dpa levels. The video record showed that the material resists necking and involves a moving deformation wave that initiates near one of the tensile grippers and spreads along ∼3/4 of the gauge length before failure occurs. Such behavior, often called a 'moving neck' has been observed previously in pure iron and Al-Mg alloys but has not been observed in irradiated stainless steels

Nondestructive testing for microstructural characterization in 9Cr-1Mo ferritic steel towards assessment of fabrication quality and in-service degradation

Energy Technology Data Exchange (ETDEWEB)

Jayakumar, T.; Rao, K.B.S.; Raj, Baldev [Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

1999-07-01

The paper discusses the usefulness of non destructive testing for microstructural characterization in 9Cr-1Mo ferritic steel. Ultrasonic velocity and attenuation measurements and spectral analysis have been used in a complementary way for characterizing Ac{sub 1} and Ac{sub 3} temperatures, amount of martensite and ferrite, dissolution of V{sub 4}C{sub 3} and NbC and formation of {delta}-ferrite. The microstructural degradation occurring due to thermal ageing and creep has also been studied by ultrasonic velocity measurements. Magnetic Barkhausen noise technique has been used for estimating the extent of various regions in heat affected zone (HAZ) of 9Cr-1Mo ferritic steel weldment. The same technique has been used for the assessment of low cycle fatigue damage in 9Cr-1Mo steel. The study establishes that non destructive methods can be used for the assessment of fabrication quality and in service degradation of the components. (author)

Quantitative evaluation of safety use limit for crevice corrosion in Ni-Cr-Mo alloys

International Nuclear Information System (INIS)

Fukaya, Yuichi; Akashi, Masatsune; Sasaki, Hidetsugu; Tsujikawa, Shigeo

2007-01-01

The most important problem with corrosion-resistant alloys such as stainless steels is localized corrosion. Crevice corrosion, which is a typical localized corrosion, occurs under the mildest environmental conditions. Consequently, whether crevice corrosion occurs or not is an important issue in structural material selection. This study investigated highly corrosion-resistant Ni-Cr-Mo alloys whose resistance for crevice corrosion is difficult to evaluate with the JIS G 0592 standard for common strainless steels. The optimized procedures for determining the critical potential and temperature for crevice corrosion of the alloys were developed based on the JIS method. The limits of safety usage of various Ni-Cr-Mo alloys were evaluated quantitatively in chloride solution environments. (author)

On the corrosion testing of weldments of high alloyed CrNiMo-stainless steels and NiCrMo-alloys

International Nuclear Information System (INIS)

Riedel, G.; Voigt, C.; Werner, H.

1997-01-01

Weldments of high-alloyed CrNiMo stainless steels and NiCrMo alloys can be more susceptible to localized corrosion than the solution annealed basic material owing to segregations and precipitations in the heat affected zone, the high temperature zone and/or in the weld. To investigate these differences the FeCl 3 -test (10% FeCl 3 . 6aq), the test ''green death'' (11.5% H 2 SO 4 , 1.2% HCl, 1% CuCl 2 , 1% FeCl 3 ) as well as chronopotentiostatic tests in artificial sea water or in 3% NaCl-solution are used. In particular for testing the highest alloyed materials a CaCl 2 -test was developed (4.5 M CaCl 2 , chronopotentiostatic test in duration of 8 to 10 hours at + 200 mV (SCE)), which can be carried out to a temperature of 115 C at atmospheric pressure. The aggressivity increases in the range FeCl 3 -test, ''green death''-test, CaCl 2 -test. Matching and graduated over-alloyed weldments (TIG, heat input of 7 and 15.5 kJ/cm) of materials 1.4529, 1.4562, 2.4856, 2.4819 (german materials No.) are comparingly examined in various tests, of materials 1.4406, 1.4539, 1.4439 and 1.4563 (german materials No.) only matching weldments in the FeCl 3 -test. In strongly oxidizing media only a highly over-alloyed performed weldment (filler material 2.4607, german material No.) produces the best corrosion behaviour, measured as the critical temperatures of localized corrosion. Measurements of critical current densities of passivation can be used for investigations of corrosion behaviour of weldments, too. Critical current densities of passivation are showing a tendency to inverse proportion to the critical temperatures of localized corrosion. Suitable electrolytes are among others 0.2 M H 2 SO 4 + 1 M NaCl + 10 -3 % KSCN, N 2 -bubbled, 25 to 60 C and xM H 2 SO 4 + 4 M NaCl + 10 -3 % KSCN (x = 0.05 to 1), 25 C, in contact with air. An influence of heat input at the welding is indicated in the test of localized corrosion, but it is only small. It is sometimes more clearly shown at

Study of the microstructure and of microhardness variation of a Ni-Fe-Cr austenitic alloy by niobium

International Nuclear Information System (INIS)

Carvalho e Camargo, M.U. de; Lucki, G.

1979-01-01

The mechanisms of hardening and corrosion resistance increase in Ni-Fe-Cr austenitic stainless steels by Nb additions are of interest to nuclear technology Niobium additions to a 321 type stainless steel were made in order to study the microhardness, electrical resistivity and metallography. Experimental measurements results are shown. The effect of Nb additions as a micro-alloying element and the thermal and mechanical processes (cold working in particular) in the microstructure and microhardness properties of the 11% Ni - 70%Fe - 17% Cr austenitic alloys were studied. (Author) [pt

Strength behaviour of 10CrMo9.10 steel in nonsteady-state applications

International Nuclear Information System (INIS)

Seidel, C.

2 testing runs with cyclic temperature increase were conducted on steel 10CrMo9.10 samples, i.e., at 500 degC and cyclic increase by 10, 25 and 50 degC, and at 550 degC and cyclic increase by 50 degC. Long-term strength was studied under a strain of 6.1 to 25.6 kp/mm 2 for 22,000 hours and the effect of periodical unloading was investigated on long-term strength at 550 degC. Sample loading and unloading proceeded within the range of 8.8 to 24.7 kp/mm 2 at an unloading rate of 8 to 100 %/min. Steel lifetime was not affected by the number of cycles. The effect of the changing load and of constant temperature without load on the long-term strength of the steel at 550 degC is shown graphically. The results showed a clear dependence of steel life on dwell time at the given temperature without load. (J.P.)

Investigation of the relationships between mechanical properties and microstructure in a Fe-9%Cr ODS steel

OpenAIRE

Hary Benjamin; Guilbert Thomas; Wident Pierre; Baudin Thierry; Logé Roland; de Carlan Yann

2016-01-01

Ferritic-martensitic Oxide Dispersion Strengthened (ODS) steels are potential materials for fuel pin cladding in Sodium Fast Reactor (SFR) and their optimisation is essential for future industrial applications. In this paper, a feasibility study concerning the generation of tensile specimens using a quenching dilatometer is presented. The ODS steel investigated contains 9%Cr and exhibits a phase transformation between ferrite and austenite around 870 °C. The purpose was to generate different ...

Dry sliding wear behavior and corrosion resistance of NiCrBSi coating deposited by activated combustion-high velocity air fuel spray process

International Nuclear Information System (INIS)

Liu, Shenglin; Zheng, Xueping; Geng, Gangqiang

2010-01-01

NiCrBSi is a Ni-based superalloy widely used to obtain high wear and corrosion resistant coatings. This Ni-based alloy coating has been deposited onto 0Cr13Ni5Mo stainless steel using the AC-HVAF technique. The structure and morphologies of the Ni-based coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS). The wear resistance and corrosion resistance were studied. The tribological behaviors were evaluated using a HT-600 wear test rig. The wear resistance of the Ni-based coating was shown to be higher than that of the 0Cr13Ni5Mo stainless steel because Fe 3 B, with high hardness, was distributed in the coating so the dispersion strengthening in the Ni-based coating was obvious and this increased the wear resistance of the Ni-based coating in a dry sliding wear test. Under the same conditions, the worn volume of 0Cr13Ni5Mo stainless steel was 4.1 times greater than that of the Ni-based coating. The wear mechanism is mainly fatigue wear. A series of the electrochemical tests was carried out in a 3.5 wt.% NaCl solution in order to examine the corrosion behavior. The mechanisms for corrosion resistance are discussed.

Internal carbonitriding behavior of Ni-V, Ni-Cr, and Ni-3Nb alloys

International Nuclear Information System (INIS)

Allen, A.T.; Douglass, D.L.

1999-01-01

Ni-2V, Ni-5V, Ni-12V, Ni-10Cr, Ni-20Cr, and Ni-3Nb alloys were carbonitrided in C 3 H 6 and NH 3 gas mixtures (bal H 2 ) over the range 700--1,000 C. Carbonitridation of Ni-12V and Ni-20Cr in C 3 H 6 /NH 3 /H 2 (1.5/1.5/97 v/o) and (1.5/10/88.5 v/o) produced duplex subscales consisting of near-surface nitrides with underlying carbides. Growth of each zone obeyed the parabolic rate law under most conditions. The presence of carbon generally did not effect the depth of the nitride zones compared to nitriding the alloys in NH 3 /H 2 (10/90 v/o). However, at 700 C, the nitride zones were deeper in the carbonitrided Ni-V alloys and Ni-20Cr. The presence of nitrogen generally increased the depth of the carbide zones in Ni-12V and Ni-20Cr compared to carburizing these alloys in C 3 H 6 /H 2 (1.5/98.5 v/o). VN, CrN, and NbN formed in Ni-V, Ni-Cr, and Ni-Nb alloys, respectively, whereas the underlying carbide layers contained V 4 C 3 in Ni-12V, Cr 3 C 2 above a zone of Cr 7 C 3 in Ni-20Cr, and NbC in Ni-3Nb. The solubilities and diffusivities of nitrogen and carbon in nickel were determined. Nitrogen and carbon each exhibited retrograde solubility with temperature in pure Ni in both carbonitriding environments. Nitrogen diffusion in nickel was generally lower in each carbonitriding mixture compared to nitrogen diffusion in a nitriding environment, except at 700 C when nitrogen diffusion was higher. Carbon diffusion in nickel was generally higher in the carbonitriding environments compared to carbon diffusion in a carburizing environment

Some elevated temperature tensile and strain-controlled fatigue properties for a 9%Cr1Mo steel heat treated to simulate thick section material

International Nuclear Information System (INIS)

Sanderson, S.J.; Jacques, S.

Current interest has been expressed in the usage of thick section 9%Cr1%Mo steel, particularly for UK Commercial Demonstration Fast Reactor (CDFR) steam generator tubeplates. This paper presents the results of some preliminary mechanical property test work on a single cast of the steel, heat treated to simulate heavy ruling sections encompassing thicknesses likely to be met in the CDFR context. The microstructures of the simulated thick section material were found to remain predominantly as tempered martensite even at the slowest transformation cooling rates used (50 deg. C/h). The effect of microstructure is reflected in the elevated temperature proof stress, tensile strength and strain-controlled fatigue endurance which were found to be comparable with the properties established for thin section normalised and tempered 9%Cr1%Mo steel. These results are extremely encouraging and, taken in conjunction with the results from other simulation work on this material, further demonstrate the potential of thick section 9%Cr1%Mo steel. (author)

Modeling of Ni Diffusion Induced Austenite Formation in Ferritic Stainless Steel Interconnects

DEFF Research Database (Denmark)

Chen, Ming; Molin, Sebastian; Zhang, L.

2015-01-01

Ferritic stainless steel interconnect plates are widely used in planar solid oxide fuel cell (SOFC) or electrolysis cell (SOEC) stacks. During stack production and operation, nickel from the Ni/YSZ fuel electrode or from the Ni contact component diffuses into the IC plate, causing transformation...... of the ferritic phase into an austenitic phase in the interface region. This is accompanied with changes in volume and in mechanical and corrosion properties of the IC plates. In this work, kinetic modeling of the inter-diffusion between Ni and FeCr based ferritic stainless steel was conducted, using the CALPHAD...

Changes In Properties and Microstructure of High-Chromium 9-12%Cr Steels Due to Long-Term Exposure at Elevated Temperature

Directory of Open Access Journals (Sweden)

Zieliński A.

2016-06-01

Full Text Available This paper presents the characteristics of the performance of P91 (X10CrMoVNb9-1, P92 (X10CrWMoVNb9-2 and VM12 (X12CrCoWVNb12-2-2 steels used for condition assessment of the pressure components of boilers with supercritical steam parameters. Studies on the mechanical properties, microstructure tests using scanning and transmission electron microscopy, and X-ray analysis of the phase composition of precipitates were performed for selected steels in the as-received condition and after long-term annealing. These steel characteristics are used for the evaluation of the microstructural changes and mechanical properties of the material of components after long-term service. The result of this study is the database of material characteristics representing the mechanical properties related to the microstructure analysis and it can be used for diagnosis of the components of pressure parts of power boilers.

Alloying and heat treatment optimization of Fe/Cr/C steels for improved mechanical properties

International Nuclear Information System (INIS)

Sarikaya, M.

1979-06-01

The effects of alloying elements and heat treatments on the microstructural changes and strength-toughness properties were investigated in optimization of vacuum melted Fe/Cr/C base steels. The structure of the steels in the as-quenched conditions consisted of highly dislocated autotempered lath martensite (strong phase) and thin continuous interlath films of retained austenite (tough phase). It has been emphasized again that the mechanical properties of the steels are sensitive to the amount and the stability of retained austenite. To increase the stability of retained austenite in the as-quenched condition 2 w/o Mn or 2 w/o Ni was added to the base steel, viz., Fe/3Cr/0.3C. Partial replacement of Cr by about 0.5 w/o Mo did not alter the beneficial microstructure

Comparative study of creep behaviour in three Cr Ni 15/15 steel stabilized with Ti and with different contents in W, Mn, Mo and Bor

International Nuclear Information System (INIS)

Solano, R.R.; Rivas, M. de las; Schirra, M.; Seith, B.

1975-01-01

The main difference between the three steels which are tested at temperature range from 650 0 C to 750 0 C is due to the hardening elements pf the matrix and the Boron content: 1. 12R72HV (X10NiCrMoTiB 1515) 2% Mn 1,5% Mo 80 ppmB 2. Vaccutherm (X12CrNiWTi 1613) 3% W 2,5 ppmB 3. RGT 21 (X12CrNiWTi 1613) 3% W 50 ppm B. The investigations of all casts are carried out in two different heat treatments which are suitable for the conditions required for the operation of the reactor. Cond. I: 1150 0 C 30 min, water quenced; 800 0 32 hour, air; 10% cold work. Cond. II: 1150 0 C 30 min, water quenched; 10% cold work. In connection with creep test the condition I irrespective of 3 steels show no remarkable difference. The observation at 750 0 C test temperature and also at condition II above 650 0 C on Boron-free Vaccutherm cast shows an unfavourable behaviour. There is no significant difference in the stress dependence of secondary creep rate and also absolute creep rate. A definite superiority is to be found for 12R72HV when considering the values for time-yield-limit-ratio and ductility compared to the W-steels. The test results shows different fracture behaviour. Transcrystalline fracture is found on cast 12R72HV, whereas RGT 21 and Vaccutherm show transition from transcrystalline to intercrystalline fracture, depending on the rupture time and test temperature. The long term rupture specimens show intercrystalline fracture. (author)

Two feasible approaches to enhance the wear behaviors of NiCrBSi coating in atmosphere and aqueous environments

Science.gov (United States)

Ye, Yuwei; Wang, Chunting; Zheng, Wenru; Xiong, Wei; Wang, Yongxin; Li, Xiaogang

2017-09-01

NiCrBSi coating was deposited successfully on the surface of 316 stainless steel substrate by means of plasma spraying. The microstructures and mechanical property were analyzed by scanning electron microscopy, x-ray diffraction, and a Vickers hardness tester. The wear performances of the coatings sliding against the GCr15 ball under ambient air and water conditions were investigated, and two feasible approaches (tungsten carbide (WC)-doping and heat treatment) were used to improve the tribological performance. Results showed that the hardness of the NiCrBSi coating increased by 12.5% and 28.5% and the porosity decreased by 26.1% and 47.8%, respectively, after WC-doping and heat treatment. During dry friction, the friction coefficient and wear rate of the NiCrBSi coating were about 0.47 and 1.4  ×  10-5 mm3 N-1 m-1, respectively. These values were higher than those obtained on other coatings. In water conditions, all coatings showed a lower friction and wear rate than that in ambient air, which was as a result of the lubrication effect of water. Significantly, with WC-doping and heat treatment, the friction coefficients of both coatings were about 18.5% and 36.7%, respectively, lower than that of the NiCrBSi coating. Furthermore, the wear rates of both coatings were about 20% and 70%, respectively, lower than that of the NiCrBSi coating.

Corrosion behavior of high purity Fe-Cr-Ni alloys in trans-passive condition

International Nuclear Information System (INIS)

Mayuzumi, Masami; Ohta, Jyoji; Kako, Kenji

1998-01-01

The corrosion behavior of high-purity (99.99%) Fe-Cr-Ni alloys was investigated in 13 N nitric acid with/without Ce 4+ ions to clarify the effect of impurities on the trans-passive corrosion of stainless steel. The following results were obtained. (1) Almost no intergranular corrosion was observed in the high-purity alloys, although the corrosion rate of the matrix region was nearly the same as that of a commercial stainless steel with the same Cr and Ni content. (2) Due to the improved intergranular corrosion resistance, the effect of the purification became significant in the corrosion condition with the grain-separation being predominant. (3) The high-purity alloys showed higher susceptivility to intergranular corrosion with aging treatment between 873 K and 1073 K. Although the sulfuric acid/copper sulfate test suggested the formation of Cr-depleted zones, a grain boundary micro-analysis using a FETEM with an EDX did not reveal any change in Cr content or impurity segregain along the grain boundaries. The mechanism of corrosion enhancement resulting from the aging treatment remains nuclear. (author)

Cyclic oxidation behavior of plasma sprayed NiCrAlY/WC-Co/cenosphere coating

Science.gov (United States)

Mathapati, Mahantayya; Ramesh M., R.; Doddamani, Mrityunjay

2018-04-01

Components working at elevated temperature like boiler tubes of coal and gas fired power generation plants, blades of gas and steam turbines etc. experience degradation owing to oxidation. Oxidation resistance of such components can be increased by developing protective coatings. In the present investigation NiCrAlY-WC-Co/Cenosphere coating is deposited on MDN 321 steel substrate using plasma spray coating. Thermo cyclic oxidation behavior of coating and substrate is studied in static air at 600 °C for 20 cycles. The thermo gravimetric technique is used to approximate the kinetics of oxidation. X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray mapping techniques are used to characterize the oxidized samples. NiCrAlY-WC-Co/Cenosphere coating exhibited lower oxidation rate in comparison to MDN 321 steel substrate. The lower oxidation rate of coating is attributed to formation of Al2O3, Cr2O3, NiO and CoWO4 oxides on the outermost surface.

Aging precipitation behavior and its influence on mechanical properties of Mn18Cr18N austenitic stainless steel

Science.gov (United States)

Qin, Fengming; Li, Yajie; He, Wenwu; Zhao, Xiaodong; Chen, Huiqin

2017-11-01

The aging precipitation behavior in Mn18Cr18N austenitic stainless steel was investigated at temperatures from 600 °C to 900 °C. During isothermal aging treatment, the primary precipitate was Cr2N with a = 0.478 nm and c = 0.444 nm, and it preferentially nucleates along initial grain boundaries and gradually grows towards the interior of grains in discontinuous cellular way. Meanwhile, a small amount of granular face-centred cubic M23C6 with a = 1.066 nm also were observed, which mainly form along grain boundaries. The effect of these precipitates on mechanical properties of the alloy was studied. It was found that precipitates result in degeneration of the matrix hardness. Meanwhile, the SEM morphologies of aged tensile sample show that the brittle fracture predominates during deformation, i.e. the fracture mode transforms from intergranular fracture to transgranular fracture with the increasing of aging time. Compared with the solution-treated sample, the strength of the aged tensile samples slightly decreases and plasticity remarkably deteriorates.

Microstructure evolution and shear strength of vacuum brazed joint for super-Ni/NiCr laminated composite with Ni–Cr–Si–B amorphous interlayer

International Nuclear Information System (INIS)

Wu, Na; Li, Yajiang; Ma, Qunshuang

2014-01-01

Highlights: • Divorced eutectic of γ-Ni and Ni 3 B formed in the brazed region. • The detailed isothermal solidification mechanism was proposed. • Borides formed at the interfaces at different temperatures were identified. • Effect of brazing temperatures on microstructure and shear strength was investigated. • Excellent joint with shear strength of 191 MPa was obtained at 1100 °C for 20 min. - Abstract: Vacuum brazing of super-Ni/NiCr laminated composite and Cr18–Ni8 steel was carried out with Ni–Cr–Si–B amorphous interlayer at different temperatures (1060–1150 °C). The effects of brazing temperature on the microstructure evolution and shear strength of the joints were investigated. Microstructure, chemical composition and microhardness of the joints were studied using field emission scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction and microsclerometer. Shear strength of the joints were measured by the electromechanical universal testing machine. Diffusion of B was the controlling factor for microstructure evolution. The detailed isothermal solidification mechanism was proposed in this study. The fracture morphology of the joint made at 1100 °C exhibited plastic feature and the shear strength reached 191 MPa. Bulky Ni 3 B formed in super-Ni cover layer near the brazed region when performed at 1060–1100 °C while Ni–B eutectic formed instead at 1150 °C

Alloying effect on martensite transformation in stainless steels

International Nuclear Information System (INIS)

Gulyaev, A.P.; Shlyamnev, A.P.; Sorokina, N.A.

1975-01-01

The effect of cobalt, nickel, molybdenum on the martensite transformation kinetics in stainless steels containing 9 to 13% Cr has been studied. Cobalt in Fe-Cr base alloys decreases the temperature of the Msub(in) and Msub(fin) points without a considerable decrease of the martensite phase amount after the transformation. Nickel reduces the martensite transformation temperature range, the nickel effect being enhanced in the presence of cobalt, which is characterized by a change of the linear dependence Msub(in)=f(%Ni) for a quadratic one. Molybdenum decreases the temperature of the Msub(in) and Msub(fin) points intensively, thus, substantially increasing the residual austenite amount. In the steels investigated Ni and Co decrease, whereas Mo increases, to some extent, the temperature of the reverse a-γ-transformation. The reduction of chromium content from 13 to 9% stimulates the martensite transformation initiation, that is why, in alloys containing 9% Cr, the increase in the contents of Ni, Co., Mo with the martensite structure maintained is possible. A further alloying of steel containing 13% Cr with these elements is rather limited due to the inhibition of the martensite transformation

Effect of heat treatment on pitting corrosion of austenitic Cr-Ni-Mo steels in sodium chloride solution

International Nuclear Information System (INIS)

Stefec, R.; Franz, F.; Holecek, A.

1979-01-01

The pitting corrosion resistance of Cr17Ni12Mo2,5 type steel under potentiostatic polarization in a sodium chloride solution is adversely affected by previous annealing. The data obtained were systematically dependent on annealing temperature, time and surface roughness. The corrosion current, the number of pits or the mean area of pit opening and the corrosion rate within the pits were increased by previous annealing at 550 to 750 0 C for 1-100 hrs. The highest corrosion rate estimated corresponded to heat treatments provoking severe sensitization to intergranular corrosion. The paercentage area of corrosion pit openings and the estimated pit penetration rates were several times higher for as-machined than for polished surfaces. It can be assumed that pitting corrosion is little affected by the carbon content and that molybdenum depletion of grain-boundary zones is responsible for the reduced pitting resistance of annealed steels. (orig./HP) [de

Effect of various heat treatments on microstructure and mechanical properties of 34CrNiMo6 steel

International Nuclear Information System (INIS)

Abd El-Azim, M.E.; Ghoneim, M.M.; Nasreldin, A.M.; Soliman, S.

1997-01-01

Three different austenitization treatments were applied to high strength 34CrNiMo6 steel: conventional austenitization (CAT), high temperature austenitization (HTA) and duplex treatment (DT). It was found that DT structure has finer prior austenite grain size (30 μm) than those of HTA (200 μm) and CAT (70 μm) structures. DT and HTA structures have coarser lath size for martensite than CAT structure. DT results in higher room temperature impact toughness than HTA and CAT structures and shifts the ductile-brittle transition to lower temperatures by 14 K and 32 K in comparison with HTA and CAT structures, respectively. However, DT structure has intermediate values of room temperature yield stress and ultimate tensile strength between those of CAT and HTA structures. When this steel was tempered at 300 and 400 C it underwent tempered martensite embrittlement associated with intergranular fracture. (orig.)

Prediction and Monitoring Systems of Creep-Fracture Behavior of 9Cr-1Mo Steels for Reactor Pressure Vessels

International Nuclear Information System (INIS)

Potirniche, Gabriel; Barlow, Fred D.; Charit, Indrajit; Rink, Karl

2013-01-01

A recent workshop on next-generation nuclear plant (NGNP) topics underscored the need for research studies on the creep fracture behavior of two materials under consideration for reactor pressure vessel (RPV) applications: 9Cr-1Mo and SA-5XX steels. This research project will provide a fundamental understanding of creep fracture behavior of modified 9Cr-1Mo steel welds for through modeling and experimentation and will recommend a design for an RPV structural health monitoring system. Following are the specific objectives of this research project: Characterize metallurgical degradation in welded modified 9Cr-1Mo steel resulting from aging processes and creep service conditions; Perform creep tests and characterize the mechanisms of creep fracture process; Quantify how the microstructure degradation controls the creep strength of welded steel specimens; Perform finite element (FE) simulations using polycrystal plasticity to understand how grain texture affects the creep fracture properties of welds; Develop a microstructure-based creep fracture model to estimate RPVs service life; Manufacture small, prototypic, cylindrical pressure vessels, subject them to degradation by aging, and measure their leak rates; Simulate damage evolution in creep specimens by FE analyses; Develop a model that correlates gas leak rates from welded pressure vessels with the amount of microstructural damage; Perform large-scale FE simulations with a realistic microstructure to evaluate RPV performance at elevated temperatures and creep strength; Develop a fracture model for the structural integrity of RPVs subjected to creep loads; and Develop a plan for a non-destructive structural health monitoring technique and damage detection device for RPVs.

Prediction and Monitoring Systems of Creep-Fracture Behavior of 9Cr-1Mo Steels for Teactor Pressure Vessels

Energy Technology Data Exchange (ETDEWEB)

Potirniche, Gabriel [Univ. of Idaho, Moscow, ID (United States); Barlow, Fred D. [Univ. of Idaho, Moscow, ID (United States); Charit, Indrajit [Univ. of Idaho, Moscow, ID (United States); Rink, Karl [Univ. of Idaho, Moscow, ID (United States)

2013-11-26

A recent workshop on next-generation nuclear plant (NGNP) topics underscored the need for research studies on the creep fracture behavior of two materials under consideration for reactor pressure vessel (RPV) applications: 9Cr-1Mo and SA-5XX steels. This research project will provide a fundamental understanding of creep fracture behavior of modified 9Cr-1Mo steel welds for through modeling and experimentation and will recommend a design for an RPV structural health monitoring system. Following are the specific objectives of this research project: Characterize metallurgical degradation in welded modified 9Cr-1Mo steel resulting from aging processes and creep service conditions; Perform creep tests and characterize the mechanisms of creep fracture process; Quantify how the microstructure degradation controls the creep strength of welded steel specimens; Perform finite element (FE) simulations using polycrystal plasticity to understand how grain texture affects the creep fracture properties of welds; Develop a microstructure-based creep fracture model to estimate RPVs service life; Manufacture small, prototypic, cylindrical pressure vessels, subject them to degradation by aging, and measure their leak rates; Simulate damage evolution in creep specimens by FE analyses; Develop a model that correlates gas leak rates from welded pressure vessels with the amount of microstructural damage; Perform large-scale FE simulations with a realistic microstructure to evaluate RPV performance at elevated temperatures and creep strength; Develop a fracture model for the structural integrity of RPVs subjected to creep loads; and Develop a plan for a non-destructive structural health monitoring technique and damage detection device for RPVs.

Specific features of precipitation hardening of austenitic steels with various base. 2. Kinetics and mechanism of carbide precipitation

International Nuclear Information System (INIS)

Kositsyna, I.I.; Sagaradze, V.V.; Khakimova, O.N.

1997-01-01

Electron microscopic studies were carried out to determine the kinetics and mechanisms of precipitation hardening in Fe-Mn, Fe-Mn-Cr, Fe-Cr-Mn-N, Fe-Cr-Ni and Fe-Ni base stainless steels (45G20M2F2, 50Kh16G15N6M2F2, 45Kh18N10G10M2F2, 40Kh18Ni18M2F2, 45N26M2F2). The steels were heat treated under various conditions. It is revealed that in manganese steels the particles of vanadium carbide nucleate according to homogeneous mechanism at all aging temperatures (600-750 deg C). The presence of chromium in the matrix promotes the transition to heterogeneous mechanism of carbide nucleation and growth. With nickel content increasing the plasticity of precipitation hardened steels gets better due to more intense diffusion of atoms and vacancies to grain boundaries and, hence, the widening of near-boundary zones free of carbide particles

Helium accumulation and bubble formation in FeCoNiCr alloy under high fluence He+ implantation

Science.gov (United States)

Chen, Da; Tong, Y.; Li, H.; Wang, J.; Zhao, Y. L.; Hu, Alice; Kai, J. J.

2018-04-01

Face-centered cubic (FCC) high-entropy alloys (HEA), as emerging alloys with equal-molar or near equal-molar constituents, show a promising radiation damage resistance under heavy ion bombardment, making them potential for structural material application in next-generation nuclear reactors, but the accumulation of light helium ions, a product of nuclear fission reaction, has not been studied. The present work experimentally studied the helium accumulation and bubble formation at implantation temperatures of 523 K, 573 K and 673 K in a homogenized FCC FeCoNiCr HEA, a HEA showing excellent radiation damage resistance under heavy ion irradiation. The size and population density of helium bubbles in FeCoNiCr samples were quantitatively analyzed through transmission electron microscopy (TEM), and the helium content existing in bubbles were estimated from a high-pressure Equation of State (EOS). We found that the helium diffusion in such condition was dominated by the self-interstitial/He replacement mechanism, and the corresponding activation energy in FeCoNiCr is comparable with the vacancy migration energy in Ni and austenitic stainless steel but only 14.3%, 31.4% and 51.4% of the accumulated helium precipitated into helium bubbles at 523 K, 573 K and 673 K, respectively, smaller than the pure Ni case. Importantly, the small bubble size suggested that FeCoNiCr HEA has a high resistance of helium bubble formation compared with Ni and steels.

Instrumental photoactivation analysis of some elements in steel

International Nuclear Information System (INIS)

Galatanu, V.; Timus, D.; Catana, D.

1985-01-01

Photoactivation determination of Cr, Ni and Mo had been performed in large representative samples of steel. The disc samples (40 mm diameter and 3,5 mm thickness) were irradiated in the bremstrahlung beam of a 25 MeV betatron, at 0.5 m from the Pt target in order to insure a fairly uniform irradiation. The gamma-rays were detected with a 40 cm Ge(Li) detector coupled to an IR 90 programmable analyser. The concentration determined were between 0,1% and 9% for Ni, 0,4% and 18% for Cr and 0,05% and 1,50% for Mo. The accuracy of the determinations was 10% for lower consentrations and 3% for higher concentrations

Effect of normalization heat treatment on creep and tensile properties of modified 9Cr-1Mo steel

International Nuclear Information System (INIS)

Panneer Selvi, S.; Sakthivel, T.; Parameswaran, P.; Laha, K.

2016-01-01

Creep and tensile properties have been investigated on modified 9Cr-1Mo steel subjected to single and double normalization heat treatments. Optical, scanning and transmission electron microscopic investigation revealed the presence of refined prior austenite grain size and fine M 23 C 6 precipitates in the double normalized steel compared to the steel subjected to single normalization heat treatment. Increased creep strain and significant reduction in creep rupture life were observed with the double normalized steel in comparison with single normalized steel. Increased tensile ductility coupled with marginal decrease in tensile strength at higher test temperature was observed with double normalized steel compared to single normalized steel. It has been attributed to the presence of refined prior austenite grain size and coarsening of Nb rich MX precipitates in double normalized steel. (author)

Ferritic stainless steels: corrosion resistance + economy

International Nuclear Information System (INIS)

Remus, A.L.

1976-01-01

Ferritic stainless steels provide corrosion resistance at lower cost. They include Type 409, Type 439, 18SR, 20-Mo (1.6 Mo), 18-2 (2 Mo), 26-1S, E-Brite 26-1, 29 Cr-4 Mo, and 29 Cr-4 Mo-2 Ni. Their corrosion and mechanical properties are examined. Resistance to stress-corrosion cracking is an advantage compared to austenitic types

Tensile properties of modified 9Cr-1Mo steel by shear punch testing and correlation with microstructures

Energy Technology Data Exchange (ETDEWEB)

Karthik, V., E-mail: karthik@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603102 (India); Laha, K.; Parameswaran, P.; Chandravathi, K.S.; Kasiviswanathan, K.V.; Jayakumar, T.; Raj, Baldev [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603102 (India)

2011-10-15

Modified 9Cr-1Mo ferritic steel (P91) is subjected to a series of heat treatments consisting of soaking for 5 min at the selected temperatures in the range 973 K-1623 K (below Ac{sub 1} to above Ac{sub 4}) followed by oil quenching and tempering at 1033 K for 1 h to obtain different microstructural conditions. The tensile properties of the different microstructural conditions are evaluated from small volumes of material by shear punch test technique. A new methodology for evaluating yield strength, ultimate tensile strength and strain hardening exponent from shear punch test by using correlation equations without employing empirical constants is presented and validated. The changes in the tensile properties are related to the microstructural changes of the steel investigated by electron microscopic studies. The steel exhibits minimum strength and hardness when soaked between Ac{sub 1} and Ac{sub 3} (intercritical range) temperatures due to the replacement of original lath martensitic structure with subgrains. The finer martensitic microstructure produced in the steel after soaking at temperatures above Ac{sub 3} leads to a monotonic increase in hardness and strength with decreasing strain hardening exponent. For soaking temperatures above Ac{sub 4}, the hardness and strength of the steel increases marginally due to the formation of soft {delta} ferrite. - Highlights: > A methodology presented for computing tensile properties from shear punch test. > UTS and strain hardening estimated using extended analysis of blanking models. > The analysis methodology validated for different heat treated 9Cr-1Mo steel. > Changes in tensile properties of steel correlated with microstructures.

Oxidation and thermal shock behavior of thermal barrier coated 18/10CrNi alloy with coating modifications

Energy Technology Data Exchange (ETDEWEB)

Guergen, Selim [Vocational School of Transportation, Anadolu University, Eskisehir (Turkmenistan); Diltemiz, Seyid Fehmi [Turkish Air Force1st Air Supply and Maintenance Center Command, Eskisehir (Turkmenistan); Kushan, Melih Cemal [Dept. of Mechanical Engineering, Eskisehir Osmangazi University, Eskisehir (Turkmenistan)

2017-01-15

In this study, substrates of 18/10CrNi alloy plates were initially sprayed with a Ni-21Cr-10Al-1Y bond coat and then with an yttria stabilized zirconia top coat by plasma spraying. Subsequently, plasma-sprayed Thermal barrier coatings (TBCs) were treated with two different modification methods, namely, vacuum heat treatment and laser glazing. The effects of modifications on the oxidation and thermal shock behavior of the coatings were evaluated. The effect of coat thickness on the bond strength of the coats was also investigated. Results showed enhancement of the oxidation resistance and thermal shock resistance of TBCs following modifications. Although vacuum heat treatment and laser glazing exhibited comparable results as per oxidation resistance, the former generated the best improvement in the thermal shock resistance of the TBCs. Bond strength also decreased as coat thickness increased.

Role of oxides and porosity on high temperature oxidation of liquid fuelled HVOF thermal sprayed Ni50Cr coatings

OpenAIRE

Song, B.; Bai, M.; Voisey, K.T.; Hussain, Tanvir

2017-01-01

High chromium content in Ni50Cr thermally sprayed coatings can generate a dense and protective scale at the surface of coating. Thus, the Ni50Cr coating is widely used in high temperature oxidation and corrosion applications. A commercially available gas atomized Ni50Cr powder was sprayed onto a power plant steel (ASME P92) using a liquid fuelled high velocity oxy-fuel (HVOF) thermal spray with three processing parameters in this study. Microstructure of as-sprayed coatings was examined using...

Effects of Cr2N Precipitation on the Antibacterial Properties of AISI 430 Stainless Steel

OpenAIRE

Je-Kang Du; Chih-Yeh Chao; Yu-Ting Jhong; Chung-Hao Wu; Ju-Hui Wu

2016-01-01

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 anti...

Comparison of SA508 Gr.3 and SA508 Gr.4N Low Alloy Steels for Reactor Pressure Vessel Steel

Energy Technology Data Exchange (ETDEWEB)

Kim, Min Chul; Lee, B. S

2009-12-15

The microstructural characteristics and mechanical properties of SA508 Gr.3 Mn-Mo-Ni low alloy steel and SA508 Gr.4N Ni-Mo-Cr low alloy steel were investigated. The differences in the stable phases between these two low alloy steels were evaluated by means of a thermodynamic calculation using ThermoCalc. They were then compared to microstructural features and correlated with mechanical properties. Mn-Mo-Ni low alloy steel shows the upper bainite structure which has the coarse cementite in the lath boundaries. However, Ni-Mo-Cr low alloy steel shows the mixture of lower bainite and tempered martensite structure that homogeneously precipitates the small carbides such as M{sub 23}C{sub 6} and M{sub 7}C{sub 3} due to an increase of hardenability and Cr addition. In the mechanical properties, Ni-Mo-Cr low alloy steel has higher strength and toughness than Mn-Mo-Ni low alloy steel. Ni and Cr additions increase the strength by solid solution hardening. Besides, microstructural changes from upper bainite to tempered martensite improve the strength of the low alloy steel by grain refining effect. And the changes in the precipitation behavior by Cr addition improve the ductile-brittle transition behavior along with a toughening effect of Ni addition.

Hydrogen embrittlement of the 22 Cr5 Ni austeno-ferritic stainless steel. Role of the microstructure

International Nuclear Information System (INIS)

Iacoviello, Francesco

1997-01-01

Austenitic-ferritic stainless steels are characterised by very good mechanical properties and by a high corrosion resistance, especially to stress-corrosion and to pitting. However, their duplex structure shows a sensitivity to hydrogen embrittlement. Among duplex stainless steels, the 22 Cr 5 Ni grade has gradually became the most used. In this work the tensile properties and the resistance to fatigue crack propagation of 22 Cr5 Ni duplex stainless steel have been analysed, with and without hydrogen charging, after it had been treated at temperatures ranging between 200-1050 deg. C for varying times. The heat treatment times and temperatures were chosen to characterise completely the effects of the different intermetallic and the carbide and nitride phases and to compare these results with those from the tensile tests and those in the literature. A technique for obtaining the hydrogen diffusion coefficient in the steel was optimised and was shown to be alternative to the permeation technique. Thermal analysis was used to determine the activation energy of the hydrogen traps in the steel. From the results the following conclusions were established: - Grain boundaries and dislocations have very little influence on the process of hydrogen diffusion. - The quantity of hydrogen absorbed depends in that any type of precipitate decrease the absorption. This decrease was probably due to changes in the diffusivity and solubility of hydrogen caused by the precipitation. - The charging with hydrogen caused a large decrease in ε m pc for the steel for all heat treatments temperature, except 1050 deg. C. At this temperature the effect was much less as the dislocation density was very low and the precipitates were now in solution. - Hydrogen charging of the steel did not affect the YS and the decrease in UTS produced depended on the microstructure. Use of the embrittlement index 'F' showed that spinodal decomposition and precipitation of G phase decrease hydrogen embrittlement

Hydrogen embrittlement of thermomechanically treated 18Ni Maraging steel

International Nuclear Information System (INIS)

Munford, J.W.; Rack, H.J.; Kass, W.J.

1977-01-01

The influence of thermomechanical treatments on susceptibility to cracking in 100 percent relative humidity air and low pressure (93.3 KPa) gaseous hydrogen has been investigated for 18Ni (350 ksi) Maraging steel. Two thermomechanical treatments were studied, ausforming and marforming and compared with the standard solution treated and aged material. Although little difference exists for the strength and toughness values between these treatments, a two to five-fold increase in the stress intensity threshold for cracking was found for both the ausformed and marformed material. A dramatic difference in cracking kinetics was also apparent as shown by the failure times at comparable stress intensities. Fractographic analysis showed that the primary fracture mode was 100 percent intergranular for the solution treated and aged samples while the ausform and marform failures were predominately quasi-cleavage or intergranular depending on orientation. Finally, permeation and diffusion measurements were conducted on the above materials and these results are correlated with the environmental cracking behavior

Hydrogen embrittlement of thermomechanically treated 18Ni Maraging steel

Energy Technology Data Exchange (ETDEWEB)

Munford, J.W.; Rack, H.J.; Kass, W.J.

1977-01-01

The influence of thermomechanical treatments on susceptibility to cracking in 100 percent relative humidity air and low pressure (93.3 KPa) gaseous hydrogen has been investigated for 18Ni (350 ksi) Maraging steel. Two thermomechanical treatments were studied, ausforming and marforming and compared with the standard solution treated and aged material. Although little difference exists for the strength and toughness values between these treatments, a two to five-fold increase in the stress intensity threshold for cracking was found for both the ausformed and marformed material. A dramatic difference in cracking kinetics was also apparent as shown by the failure times at comparable stress intensities. Fractographic analysis showed that the primary fracture mode was 100 percent intergranular for the solution treated and aged samples while the ausform and marform failures were predominately quasi-cleavage or intergranular depending on orientation. Finally, permeation and diffusion measurements were conducted on the above materials and these results are correlated with the environmental cracking behavior.

Effect of ETA treatment on corrosion fatigue in rotors and blades and stress corrosion cracking in 3.5 NiCrMoV steel low-pressure turbine discs

International Nuclear Information System (INIS)

Hitomi, Itoh; Takashi, Momoo; Takayuki, Shiomi

2001-01-01

In recent years, to increase the reliability and reduce the amount of feed water iron to prevent of fouling of steam generator tubes, ethanolamine (ETA) treatment has been adopted into the secondary system. In this investigation, the authors verified that ethanolamine treatment does not adversely affect the susceptibility of either stress corrosion cracking (SCC) in the turbine discs that are the principal units in the secondary system or corrosion fatigue (CF) in rotors and blades. In the first stage, a laboratory investigation was made of (1) SCC initiation and propagation in 3,5 NiCrMoV steel and (2) CF in 3,5 NiCrMoV steel and blade steels, in both cases using deaerated water to which had been added ethanolamine with few organic acids that is 10 times the estimated concentration. It was confirmed that the ethanolamine treatment had almost no effect. In the second stage, test pieces (removed from the disc steel inserted into the turbine extraction chamber before the ethanolamine treatment was started) were used to observe the initiation and propagation of SCC. Even after long-term observation, ethanolamine treatment into the secondary system was found to have almost no effect on the susceptibility of SCC in discs. (author)

The influence of cold work on the oxidation behaviour of stainless steel

International Nuclear Information System (INIS)

Langevoort, J.C.

1985-01-01

In this thesis the study of the interaction of oxygen gas with stainless steel surfaces is described. Thermogravimetry, microscopy and ellipsometry have been used to follow the oxidation in situ, while EDX, AES and XPS have been used to determine the oxide compositions. The aim of this thesis is to reveal the influence on the oxidation behaviour of stainless steel of i) cold work (rolling, drawing, milling, polishing and Ar ion bombardment) ii) the initially formed oxide and iii) the experimental conditions. Two types of stainless steels have been used (AISI 304 (a 18/8 Cr/Ni steel) and Incoloy 800 H (a 20/30 Cr/Ni steel)). (Auth.)

Establishment of Wear Resistant HVOF Coatings for 50CrMo4 Chromium Molybdenum Alloy Steel as an Alternative for Hard Chrome Plating

Science.gov (United States)

Karuppasamy, S.; Sivan, V.; Natarajan, S.; Kumaresh Babu, S. P.; Duraiselvam, M.; Dhanuskodi, R.

2018-05-01

High cost imported components of seamless steel tube manufacturing plants wear frequently and need replacement to ensure the quality of the product. Hard chrome plating, which is time consuming and hazardous, is conventionally used to restore the original dimension of the worn-out surface of the machine components. High Velocity Oxy-Fuel (HVOF) thermal spray coatings with NiCrBSi super alloy powder and Cr3C2 NiCr75/25 alloy powder applied on a 50CrMo4 (DIN-1.7228) chromium molybdenum alloy steel, the material of the wear prone machine component, were evaluated for use as an alternative for hard chrome plating in this present work. The coating characteristics are evaluated using abrasive wear test, sliding wear test and microscopic analysis, hardness test, etc. The study results revealed that the HVOF based NiCrBSi and Cr3C2NiCr75/25 coatings have hardness in the range of 800-900 HV0.3, sliding wear rate in the range of 50-60 µm and surface finish around 5 microns. Cr3C2 NiCr75/25 coating is observed to be a better option out of the two coatings evaluated for the selected application.