The acoustic emission(AE) method has been utilized to study the detectability of crack initiation and growth during intergranular stress corrosion cracking(IGSCC) of Inconel 600 alloy and to evaluate its applicability as a non-destructive testing method by comparing the crack behavior with AE parameters and measuring the minimum detectable crack size.
Variously heat-treated specimens were tensioned by use of a constant extension rate tester at various extension rates to yield different stress corrosion cracking behaviors of Inconel specimens. Significant AE responses were observed during IGSCC, ductile fracture and plastic deformation. The magnitude of AE peak amplitudes was in the decreasing order for IGSCC, ductile fracture and plastic deformation. AE also was effective means to identify the transition from small crack initiation and growth to dominant crack growth. Close correlation was found to exist between AE behaviors and electrochemical current changes, suggesting that the formation and breakdown of passive film is involved in IGSCC of Inconel 600. The minimum crack size detectable with AE was approximately 200 to 400㎛ in length and below 100㎛ in depth, indicating the possibility of detecting small IGSC cracks prior to the growth of single dominant cracks.
