Impact behavior of 980 MPa grade Cr-Ni weld metal composed of martensite and retained austenite

Abstract

MPa grade Cr-Ni weld metal with martensite and retained austenite was produced by single-pass GMAW. Its impact behavior was evaluated using the Charpy impact test. It was found that (1) strain-induced martensite transformation from the retained austenite enhances the impact absorbed energy at various temperatures and contents of oxygen in weld metal; (2) increasing the oxygen content in weld metal reduces the impact absorbed energy; and (3) at 233K, strain-induced martensite transformation can change the fracture mode of the weld metal with extremely low oxygen content from brittle to ductile, but it has no such effect at higher oxygen content levels. Oxide promotes ductile fracture. An increase in the oxygen content lowers the vTrs.

Mechanical Stability of Retained Austenite in Multi-Pass Cr-Ni Weld Metal in an Over-Matching Welded Joint

“…[1][2][3][4][5] A new Cr-Ni weld metal of 980 MPa grade with a microstructure of martensite and retained austenite (RA) was developed based on the concept that martensite guarantees high strength and retained austenite elevates mechanical properties and toughness as well as preventing hydrogen embrittlement. It has been con rmed that the retained austenite in the Cr-Ni weld metal enhances the mechanical properties [6][7][8] and fracture toughness 9,10) through stress-or strain-induced martensite transformation and that it effectively inhibits hydrogen embrittlement by trapping diffusive hydrogen. 11) In practical service, to ensure the above bene ts of retained austenite, there must be an appropriate amount in the weld metal.…”

Thermal stability of retained austenite in Cr–Ni weld metals at low temperatures

“…2 Strain induced martensite transformation from the retained austenite occurred in the Cr-Ni weld metal, 3 by which the toughness of weld metal is enhanced. 4 It emerged from previous works that for the newly developed weld metal, strength is achieved by martensite while retained austenite prevents cold cracking and ensures high toughness. Accordingly, a certain amount of retained austenite is required.…”

“…Research Center for Strategic Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan 2 Liaoning University of Technology, China 3 Tianjin Pipe Group Corporation, Tianjin, China4 China First Heavy Industries, Tianjin, China5 Joining and Welding Research Institute, Osaka University, Osaka, Japan *Corresponding author, email QIU.Hai@nims.go.jp…”