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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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
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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...
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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