Experimental work on passivation mechanisms and cracking planes of 304L stainless steel stress corrosion cracking in acidic medium using Atomic Emission Spectro-Electrochemistry, SEM, EBSD, and XRD techniques

摘要

SCC was produced for 304L austenitic stainless steel in different concentrations of chloride containing sulfuric acid solutions: (M 2 H_2SO_4 + M 0.5 NaCl). Scanning Electron Microscope (SEM), and Electron Backscatter Diffraction (EBSD) were used to characterize the produced cracks. Analysis revealed grains to be ruptured preferentially according to four plane families; {111}, {110}, {102}, and {211} with percentages rounded to (28,27, 17, 16) % respectively. Film Rupture-dissolution Model [1] explains intergranular SCC as cycles of mechanical slip-induced passive film breakdown causing excessive material dissolution until it repassivates again. For face centered cubic crystals, {111} planes are those over which slipping occurs. However, rupture planes could be of {110} family due to equal dislocation-pile-up on the primary and conjugate {111} planes [2], As illustrated in Fig. 1, the macroscopically applied stress (Σ) on the material is redistributed over the grains locally (σ) according to their individual crystallographical orientation. To analyze this further, an elasto-mechanical modeling is to be performed using Finite Element Methods at the crystalline scale to try to find the potential planes with maximum stresses. Interaction of the local crystallographical aspects with Stress intensity factor at crack tip, and resulting local plasticity is to be analyzed. Results will be correlated to the experimental results obtained.