Microstructural and Corrosion Characteristics of a Heat Treatable Stainless-SteelWeldments

Abstract

In this research, AISI 316 stainless steel samples were welded and subjected to post-weld heat treatment (PWHT). Thereafter, theywere evaluated for microstructural andcorrosion behaviours. PWHT was carried out on some of the welded samples at 400°C for 12 minutes in the muffle furnace. Investigation of microstructure and chemical characterization of the samples was performed using scanning electron microscope, whilst also corrosion rate was evaluated by weight loss method in a controlled environment The As-welded and post-welded samples were immersed in 0.5M of tetraoxosulphate (IV) acid at room temperature and then studied for 15days with each sample removed at 3days interval. It was evident that the post-weld heat-treated samples under controlled heating condition showed higher resistance to corrosion than the as-welded sample which is attributed to the fact that PWHT increases steel weldment resistance to stress corrosion cracking ultimately. Therefore, corrosion susceptibility of stainless steel in H2SO4 medium during exposure time could be a pointer to the aggressive sulphide ion (SO4 -) which continuously breaks down the protective film on the metal sample.Two major carbide precipitates of Cr23M7 and CR7C3 were evident after the simulation of the research material, which could pose a detrimental effect on the general performance of the steel in engineering and other industrial applications.