Effect of ferrite transformation on the tensile and stress corrosion properties of type 316 L stainless steel weld metal thermally aged at 873 K
01 Jul 1995-Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science (Springer-Verlag)-Vol. 26, Iss: 7, pp 1859-1868
TL;DR: In this article, the effect of microstructural changes, due to transformation of delta ferrite, on the associated variations that take place in the tensile and stress corrosion properties of type 316 L stainless steel weld deposits when subjected to postweld heat treatment at 873 K for prolonged periods (up to 2000 hours).
Abstract: This article deals with the effect of the microstructural changes, due to transformation of delta ferrite, on the associated variations that take place in the tensile and stress corrosion properties of type 316 L stainless steel weld deposits when subjected to postweld heat treatment at 873 K for prolonged periods (up to 2000 hours). On aging for short durations (up to 20 hours), carbide/ carbonitride was the dominant transformation product, whereas sigma phase was dominant at longer aging times. The changes in the tensile and stress corrosion behavior of the aged weld metal have been attributed to the two competitive processes of matrix softening and hardening. Yield strength (YS) was found to depend predominantly on matrix softening only, while sig-nificant changes in the ultimate tensile strength (UTS) and the work-hardening exponent, n, occurred due to matrix hardening. Ductility and stress corrosion properties were considerably affected by both factors. Fractographic observations on the weld metal tested for stress-corrosion cracking (SCC) indicated a combination of transgranular cracking of the austenite and interface cracking.
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TL;DR: In this paper, a standard 316H welding wire was used to obtain 6% δ-ferrite in the weld metal by automatic tungsten inert gas welding, and the effect of aging time at 750°C on microstructure and mechanical proper...
Abstract: A standard 316H welding wire was used to obtain 6% δ-ferrite in the weld metal by the automatic tungsten inert gas welding. The effect of aging time at 750°C on microstructure and mechanical proper...
3 citations
Cites background from "Effect of ferrite transformation on..."
...impact energy were related directly to the amounts and morphologies of M23C6 and σ phase [27,28]....
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...[28] found that these factors influencing the mechanical properties of the as-aged weld metal gave rise to opposing effects (softening and hardening)....
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...residual stress resulted in the matrix softening, which also decreased the microhardness [27,28]....
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...And the total amount of precipitates (M23C6 to σ phase) increased owing to the increasing decomposition amount of δ-ferrite [21,28]....
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...Furthermore, the precipitated M23C6 deteriorated the elongation and impact energy of the weld metal, but the matrix softening resulting from the removal of welding residual stress had beneficial effects on the elongation and impact energy of the weld metal [27,28]....
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TL;DR: In this paper, stress corrosion tests were performed for welded 308 stainless steel under proton irradiation at 473 K. The in-beam loading condition was 0 and 300MPa in tension under an irradiation dose rate of 1.3 © 1017 dpa/s.
Abstract: Stress corrosion tests were performed for welded 308 stainless steel under proton irradiation at 473K. The concentration of oxygen and hydrogen in the feed water was controlled to be below 5 and 10 ppb, respectively. The in-beam loading condition was 0 and 300MPa in tension under an irradiation dose rate of 1.3 © 1017 dpa/s. The electrochemical corrosion potential (ECP) was also measured during the tests. After the corrosion tests, the specimen surface at the fusion zone was examined by SEM for all specimens. Extensive electrochemical reactions on the specimen surface were implied by ECP measurement under the in-beam loading condition. The initiation of surface cracking followed by coalescence of numerous larger corrosion pits at the boundaries of ferrite phases in the austenitic matrix was detected for the in-beam specimens at 300MPa. Thus, the initial process of stress corrosion cracking at weld metal would be accelerated under irradiation. [doi:10.2320/matertrans.MAW201411]
2 citations
01 Jan 2002
TL;DR: In this article, the authors used fractographical features and activation energy measurements to understand the mechanism of stress corrosion cracking of austenitic steels in a chloride medium and found that cold work and sensitization decrease the threshold values and adversely influence the crack growth rates.
Abstract: Number of loading techniques such as constant strain, constant load, slow strain rate are being used for stress corrosion testing of materials. These techniques have been useful in comparision of stress corrosion susceptibility of various alloy/environment combinations and also to evaluate the influence of metallurgical factors for a particular alloy. Fracture mechanics approach in combination with above loading techniques has been successfully utilized in getting quantitative data with respect to threshold values and crack growth rates in addition to grading the alloys with respect to cracking susceptibility. This data could be used in predictive models. In this paper, data available up to date on austenitic steels is presented and analyzed. Work carried out at authors laboratory on AISI 304LN and AISI 316LN stainless steels and their welds has been highlighted. It has been found that cold work and sensitization decrease the threshold values and adversely influence the crack growth rates. For welds of AISI 316SS, it is seen that threshold values are almost half and crack growth rates are an order of magnitude higher as compared to solution annealed condition. Based on the data generated on crack growth rates, analysis of acoustic emission records during crack growth, fractographical features and activation energy measurements attempt has been made to understand the mechanism of stress corrosion cracking of austenitic steels in chloride medium. A brief introduction to life prediction approaches such as slip dissolution model, models based on crack growth rates and statistical approach has been given.
2 citations
TL;DR: In this article, two types of 316 butt welds with carbon contents of 0.016% and 0.062% have been produced using the gas tungsten arc welding process.
Abstract: Two types of 316 butt welds with carbon contents of 0.016% and 0.062% have been produced using the gas tungsten arc welding process. The δ-ferrite content decreased from 7.2 to 2.8% in volume as the carbon content increased. The creep-rupture strength and creep ductility of the two types of weld metals have been measured at 550 ℃ over the stress range of 290–316 MPa and at 600 ℃ over 230–265 MPa. The microstructure change and precipitation behavior of the weld metals were observed and related to the creep rupture properties. The creep rupture strength of the C2 (0.062% C) weld metal was higher than that of the C1 (0.016% C) weld metal at both 550 ℃ and 600 ℃. At 550 ℃, as the decrease in the applied stress, the difference of the creep-rupture life between the two weld metals diminished due to the higher depletion rate of carbon by precipitation of M23C6 in the C2 weld metal, while at 600 ℃, the difference enlarged due to the massive precipitation of σ phase and extensive crack formation and propagation along σ/austenite boundaries in the C1 weld metal. For both the C1 and C2 weld metal, the decrease in ductility was adverse with the transformation percentage and related to products of the δ-ferrite transformation.
1 citations
References
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TL;DR: In this article, the authors studied the stress corrosion cracking of a sensitized Type 304 stainless steel at room temperature using controlled potentials and two concentrations of sodium thiosulfate.
Abstract: The stress corrosion cracking of a sensitized Type 304 stainless steel has been studied at room temperature using controlled potentials and two concentrations of sodium thiosulfate. In both constant extension rate and constant load tests, the crack velocities attain extremely high values, up to 8 μm s-1. Scratching electrode experiments conducted at various pH values on simulated grain boundary material show that both the crack initiation frequency and crack velocity are closely related to the repassivation rate of the grain boundary material as expected on a dissolution-controlled mechanism; however, the maximum crack velocity at any potential is consistently about two orders of magnitude higher than that predicted from the electrochemical data. Frequent grain boundary separation ahead of the crack tip is thought to occur, but retarded repassivation of the grain boundary material is a necessary feature of the cracking. Effects of strain-generated martensite are discussed.
64 citations
54 citations
TL;DR: In this paper, Potentiostatic and isothermal immersion tests have been used to investigate pitting corrosion in the weld metal of low carbon (<0.03%C) austenitic stainless steels.
Abstract: Potentiostatic and isothermal immersion tests have been used to investigate pitting corrosion in the weld metal of low carbon (<0.03%C) austenitic stainless steels. The experiments were co...
46 citations
TL;DR: In this paper, the microstructure changes and consequent deterioration in the room temperature tensile properties of type 316L stainless steel weld metal when exposed to elevated temperatures (773 to 973 K) for prolonged periods (up to 5000 hours).
Abstract: This paper deals with the microstructural changes and consequent deterioration in the room temperature tensile properties of type 316L stainless steel weld metal when exposed to elevated temperatures (773 to 973 K) for prolonged periods (up to 5000 hours). The microstructure-property correlation derived in this study is based on a variety of techniques: Magne-Gage, electrochemical extraction, X-ray diffraction, tensile testing, and both optical and electron microscopy. It has been established that the amount and morphology of the sigma phase are the key factors in determining the changes in the strength levels, total elongation, and extent of work hardening. The amount and morphology of sigma, in turn, is seen to depend on the relative kinetics of the various transformations, such as dissolution of delta-ferrite, growth of carbides,etc., shape changes in sigma, and the relative stabilities of the phases at the corresponding temperature of aging. The complicated dependence of the tensile properties on the microstrutural changes has been explained with direct quantitative evidence.
44 citations