Some Effects of Nitrogen Content on the Stress Corrosion Susceptibility of AIS1 Type 304 Austenitic Stainless Steel

Abstract

The effects of nitrogen content on the susceptibility of AISI Type 304 stainless steel to stress corrosion cracking have been studied by exposing U-bend specimens of the alloy containing various amounts of nitrogen to boiling magnesium chloride solutions. It was found that nitrogen in solid solution in Type 304 stainless steel reduces the resistance of the alloy to stress corrosion. Increasing amounts of nitrogen cause shorter times to crack initiation and more rapid failures by increasing the rate of propagation. The susceptibility of Type 304 is further increased by thermally aging the stressed U-bend specimens at 154 C before exposing them to the corrosive medium. The observations from this investigation seem to support those past theories which suggested that the increased susceptibility of austenitic stainless steels with higher nitrogen contents was due to the formation of nitrogen-rich areas within the austenitic matrix.

Effect of nitrogen content in sensitised austenitic stainless steel on the crack growth rate in simulated BWR environment

“…Dutta et al [30] have reported that higher nitrogen levels (0.19 wt.%) in type 316L stainless steel lead to a greater DOS due to chromium nitride precipitation as compared to the SS with 0.16 wt.% nitrogen. In some of the studies [31,32] it has been reported that presence of nitrogen in type 304 austenitic SS results in earlier crack initiation and higher CGR in boiling magnesium chloride solution. It has also been reported that nitrogen addition up to 0.16 wt.% reduces susceptibility to IGSCC in sensitised type 304 stainless steel in sodium sulphate added water at 250°C [29].…”