2018 Volume 58 Issue 11 Pages 2102-2109
Effect of Cr content and microstructure on high temperature oxidation behavior of high nitrogen steels with 0.2–0.3 mass% of nitrogen has been investigated. For high temperature oxidation test 9–15%Cr high nitrogen steels are prepared. High temperature oxidation tests were carried out in air mainly at 800°C for 300 h at maximum. Weight gain was measured and oxide scales were observed using an optical microscope and analyzed with an electron probe X-ray microanalyzer. The addition of high nitrogen improved the oxidation resistance of 9–15%Cr high nitrogen steels. It was found that the oxidation resistance of the high nitrogen steels does not depend greatly on Cr content but on their microstructure. The oxidation resistance of high nitrogen ferritic heat-resistant steels increased as the fraction of martensite structure increased. These results indicate for high nitrogen steels Cr diffusion along grain boundaries is further promoted resulting in the formation of protective oxide scale having high Cr concentration.