Effect of environment, mechanical conditions, and materials characteristics on AE behavior during corrosion fatigue processes of an austenitic stainless steel

Abstract

Acoustic emission (AE) behavior during corrosion fatigue (CF) processes has been studied in a commercial grade 304 austenitic stainless steel with special attention to the effect of environment, mechanical conditions, and materials characteristics. Precracked compact tension specimens were tested under cyclic tension-tension load, polarized potentiostatically in 1N H 2SO 4 + 0.5M HaCl or 1N H 2SO 4 solutions at room temperature. Valuable AE signals discriminated from environmental and mechanical noises by source location were monitored at the loading phase near the maximum load. The experimental results showed that the AE activity observed in corrosive environments increased significantly with the acceleration of crack growth rates, compared with that observed in air (inert environment). Detailed SEM observations found cleavage-like cracking, intergranular-like cracking, separations, etc. on the crack surfaces. The AE sources which provided the high AE activity during CF crack growth were shown to be such microcracking processes as cleavage-like cracking, intergranular-like cracking, and separations caused by the cooperation of environments (intergranular corrosion or hydrogen), mechanical conditions (triaxial stress), and materials characteristics (non-metallic inclusions or carbides precipitated along grain boundaries by sensitization). The effect of these three factors on the AE behavior and cracking mechanisms is discussed in detail.