Optimization of the composition of austenitic stainless nitrogen-containing steels with high corrosion and mechanical properties

Abstract

The study investigated 16 grades of austenitic stainless steels (ASS) with different chemical composition, including nitrogen. Metallographic and electrochemical studies of pitting corrosion in a solution of 3.5% NaCl (GOST 9.912) were carried out. The optimum ratios of carbon and nitrogen concentrations in ASS are determined, which allow obtaining high resistance to pitting corrosion and high strength. Equation of the dependence of break down potential Eb and strength (Rp0.2 and Rm) on the chemical composition of the steels with nitrogen were proposed. The effect of heat treatment and severe plastic deformation on the pitting resistance, mechanical and paramagnetic properties of the HNS has been studied. It was shown that during SPD, the HNS strength increased by about 3 times, while the fracture was not brittle and occurred by the quasi-cleavage mechanism. Although the potential of Eb decreased, it remained higher than that of steel 09Cr18Ni10Ti. The HNS of the investigated composition also showed high resistance to stress corrosion cracking in a quenched and aged at 500 zC states, and did not show embrittlement in a corrosive environment even after SPD. © The Authors, published by EDP Sciences, 2019.