The resistance of stainless steel to sensitization can be increased by reducing the carbon content, since sensitization is caused by the formation of chromium-rich carbides at grain boundaries which depletes the boundary region of chromium. The reduction in carbon content also lowers the strength of the steel, but this can be counteracted by adding nitrogen, leading to a series of low-carbon high-nitrogen alloys which are promising candidates for applications in the nuclear industry. However, the effect of nitrogen on the phase relationships in stainless steel are complex, and the purpose of this study is to examine these effects.Samples of 316 stainless steel with 16 w/o Cr, 9.8 w/o Ni, 2.5 w/o Mo, 0.03 w/o C, and 0.06-0.16 w/o N which had been solutionized and then aged at 600-700°C for 3-300 hours were used. Grain boundary phases were identified using electron diffraction, and grain boundary chemistry was measured using X-ray spectroscopy with a 10nm probe, either positioned directly on the boundary or stepped across the boundary with a spatial resolution of 50nm. The Cliff-Lorimer method was used to quantify the x-ray results.
Effects of Carbon Content and Chromium Segregation on Creep Rupture Properties of Low Carbon and Medium Nitrogen Type 316 Stainless Steel