A thermogravimetric and metallographic study of the high temperature oxidation of a binary nickel-chromium alloy in humidified air. Part I: Oxidation start at heating
Air humidity may significantly influence the behaviour in oxidation at high temperature of the refractory metallic alloys. To study the effect of water vapour on the oxidation phenomena in thermal cycling conditions in the case of nickel-based alloys a Ni-25Cr binary alloy was considered. It was subjected to oxidation at four high temperatures, 1000, 1100, 1200 and 1300°C for 48 hours in dry air and in a humidified air. The heating parts of the thermogravimetry curves were exploited to specify the temperatures of oxidation start and the amount of oxide mass formed during heating. By comparison with dry air, the water concentration tried in this work induced an earlier oxidation during heatingwith a good reproducibility of temperature start.