Effect of Composition and Heat Treatment On the Stress Corrosion Cracking Of Austenitic Stainless Steels

Abstract

A grooved, tensile type, accelerated stress corrosion test is described by which austenitic stainless steels were tested in both the solution and the vapor phase of boiling 42 percent magnesium chloride. Of the commercial alloys tested, Types 310 and 314 stainless steel offered considerably greater resistance to cracking than the more commonly used 304, 316 and 347 grades. These grades not only showed longer times to crack for the same applied stress but indicated higher threshold stresses below which cracking would not be expected to occur. Resistance to cracking increased with both nickel and silicon content but was generally unaffected by carbon, nitrogen, manganese and chromium contents within commercial limits. Variations in heat treatment and surface conditions were relatively ineffective in changing the cracking times of austenitic stainless steels. Treatments designed to apply on oxide film showed some improvement in the resistance to cracking of these alloys. The data suggest that stress corrosion cracking in these alloys is both electro-chemical and mechanical in nature, probably closely related to the deformation characteristics of the alloys and, to a lesser extent, the passive film which protects them. 6.2.5