High temperature isothermal oxidation behaviour of an oxide dispersion strengthened derivative of IN625

Gas atomised IN625 powder was mechanically alloyed with <1·0 Wt.% nano-yttria and consolidated by spark plasma sintering (SPS) to produce an oxide dispersion strengthened (ODS) alloy. The isothermal oxidation rate constant of the ODS alloy, and wrought IN625, was determined by thermogravimetric analysis. This was performed at 900 °C in static laboratory air for exposure times of up to 1000 h. It was found that the ODS alloy oxidised ~40x slower than wrought IN625, which is attributed to the reactive element effect. It is further proposed that the improvement in oxidation resistance of the ODS alloy, and the superior morphology of the oxide scale formed on the ODS alloy, may be related to the presence of Nb carbide, rather than δ-phase, in the ODS alloy.