Effect of Zirconium on the Oxidation Resistance of Chromium Stainless Steels

Abstract

The effect of zirconium alloying on the oxidation resistance of 15% to 18% chromium steels has been investigated by means of isothermal heating at the temperatures up to 1000°C. Alloying of zirconium the amount of which exceeds its stoichiometric equivalent to the total amount of carbon and nitrogen in steels is found to improve the oxidation resistance of chromium steels. Electron probe microanalysis of the scales formed on the zirconium containing steels can detect no zirconium in the scales and shows prominent chromium enrichment in the inner scales. Extraction analysis of precipitates in the steels after heating up to 1 100°C reveals the zirconium carbonitrides to be stable up to 1000°C. The stable precipitates prevent the steels from grain growth when heated up to 1000°C. The beneficial effect of zirconium on the oxidation resistance of chromium steels is considered to be attribute to stable zirconium carbonitride precipitates which prevent the steels from release of carbon and grain growth in the course of oxidation at temperatures up to 1000°C.