Distinguishing effect of different surface finishing techniques on the stress corrosion cracking susceptibility of 304L and 316L SS in chloride environment

Abstract

Surface finishing operations are found to play a major role in determining the stress newlinecorrosion cracking resistance of austenitic stainless steel components. Milling, grinding and newlineturning operations result in a heavily deformed surface microstructure leading to newlinedeterioration in corrosion resistance. The present study is an organized attempt to enhance newlinethe resistance of SS in the solution annealed and in surface machined condition to chloride newlineinduced stress corrosion cracking by appropriate surface engineering. AISI 304L and 316 L newlineSS in solution annealed condition were subjected to the different surface working newlineconditions like a) grinding, b) milling, c) turning and d) buffing operations. The surface and newlinecross section of the samples were characterized using optical microscopy, field emission newlinescanning electron microscopy (FESEM) and micro-hardness test. Phase confirmation and newlineresidual stress analysis were done by X-ray diffraction (XRD). The samples were tested for newlinethe stress corrosion cracking (SCC) susceptibility as per ASTM G36 for 3 h, 9 h, and 72 h. newlineDetailed characterization of the samples was carried out post SCC tests. Results showed newlinethat surfaces in milled, turned and ground conditions were susceptible to SCC. However, newlineon the application of buffing the surfaces were able to resist SCC in boiling MgCl2 newlinesolution. Buffing induces compressive stresses on the surface together with the removal of newlinea plastically strained layer from the surface resulting in enhanced SCC resistance. Further newlinethe samples in milled, ground and turned conditions were also subjected to buffing newlineoperation under optimized conditions followed by SCC tests. Results showed that the SCC newlineresistance of the SS surfaces in milled, turned and ground conditions can be enhanced by newlinethe application of buffing operation at the end. Conventional machining operations such as newlinegrinding, milling, and turning resulted in high tensile residual stresses on the surface newlinetogether with the high density of deformation bands making these surfaces highly newlinesusceptible to