Optimizing Surface Hardness and Corrosion Resistance in 316L Stainless Steel via SMRT and Plasma Nitriding.

Abstract

Increasing the mechanical strength of stainless steel is fundamental to expanding its applications and extending its useful life, especially due to its impressive corrosion resistance. However, many processes that make possible increasing the hardness and wear resistance of these steels also compromise their performance when they are subjected to corrosive environments. Because of the need to increase surface hardness without jeopardizing corrosion resistance, this study explores the impact of a surface mechanical rolling treatment (SMRT) with volumetric reductions of 50% and 70%, together with high-temperature plasma nitriding (PN) (450, 500, and 550 °C), on 316L steel. X-ray diffraction analysis analyzed the composition and structure of the resulting coatings. Mechanical strength was assessed using Vickers microhardness, while corrosion resistance was tested in a 3.5%-by-weight NaCl solution. The results indicate a substantial increase in surface hardness in all of the nitrided samples. Notably, the samples were subjected to rolling with 50% and 70% volumetric reduction, and subsequent nitriding at 550 °C showed a reduced impairment of corrosion resistance. This shows that the methodology adopted in this study, consisting of SMRT and PN, can increase the useful life and expand the applicability of stainless steels commonly used in various industry sectors.