Effect of Cold-working and Mo Addition on Creep Behavior in High Mn Austenitic Stainless Steels

Abstract

Synopsis :The effect of cold-working and Mo addition on creep behavior in 15Mn-17Cr-0.09C-0.39N-(0.01, 0.5, 1.0, 1.5, 2.0) Mo steels has been investigated. The steels with solution treatment at 1373 K and ones with 40 % cold-rolling are subjected to a creep test at 873 K under 200-400 MPa, respectively. Time to rupture (t r ) of both steels increases with increasing the Mo concentration. Since t r in the cold-rolled steels is shorter then that in solution-treated ones in a same creep condition, cold-working is suggested to be harmful for creep strength. Creep rate in a primary creep region of cold-rolled steels with more than 1.0 Mo is smaller than that for solution-treated ones because many dislocations are induced by the cold-working. This nature is advantageous as sealing materials for high temperature. Mo addition causes decreasing of minimum creep rate in the solution-treated steels. A linear relationship exists between logarithm of minimum creep rate and Mo content. In the cold-rolled steels with 0.01 Mo and 0.5 Mo, recrystallization is partially occurred during a prescribed heat treatment before the creep tests. Therefore, the creep rate is promptly accelerated. In the cold-rolled steels with more than 1.0 Mo, the suppression of recrystallization by Mo yields the small minimum creep rate and the extension of t r . Fine precipitates of Laves phase are generated in grain interior in tertiary creep region of cold-rolled steels with 1.5 and 2.0 Mo. It also contributes to the extension of t r due to the retarding effect of creep rate acceleration.

Effect of Intergranular Carbides on Creep Strength in Nickel-Based Heat-Resistant Alloys

“…28) Hirata et al also reported that the acceleration of the creep rate in cold-rolled high-Mn austenitic stainless steel is due to stress redistribution between soft recrystallized and hard deformed grains. 29) In the Bailey-Orowan model, the effective stress is proportional to the internal stress in the particle-distributed hardening alloys. 30,31) In the region adjacent to the PFZ, the internal stress is increased by stress redistribution.…”