The Effect of Cold Work on the Stress-Corrosion Cracking of Type 302 Austenitic Stainless Steel

Abstract

Abstract The effect of cold work on stress-corrosion cracking of Type 302 austenitic stainless steel wire exposed to boiling (154 C, 309 F) 42 weight-percent aqueous magnesium chloride solution was determined. Wire specimens of 0.02-in diameter were stressed in uniaxial tension using specially designed glass test cells containing the corrosive environment. Tests were conducted at five applied stresses over the range 10,000 to 30,000 psi with laboratory-annealed wire and as-received (bright-annealed) material which had been cold worked 10, 20 and 30 percent. It was established that: (1) failure generally occurred in the vapor phase above the boiling MgCl2 solution, (2) the time-to-failure varied inversely with the applied stress, (3) the 10 percent cold-worked material exhibited the shortest time-to-failure, and (4) the 30 percent cold-worked material had the maximum resistance to stress-corrosion cracking. The short times-to-failure recorded for the 10 percent cold-worked material were attributed to introduction of large amounts of localized residual stresses in the bright-annealed material by the cold-working process. The longer times-to-failure associated with the more heavily cold-worked material were explained by the transformation of austenite to “quasi-martensite”. Crack propagation rates, nearly independent of the applied stress, were greatest for 10 percent cold-worked material. Average crack depth decreased with increasing degrees of applied stress and cold work. In general, a positive correlation existed between the crack density (cracks/inch) and the applied stress.