Dual effects of Cr doping on the high-temperature oxidation behavior of Mo₂FeB₂-based cermets

The effects of Cr doping on the high-temperature oxidation behavior of Mo₂FeB₂-based cermets were systematically investigated at 700 °C, 740 °C and 800 °C, respectively. The results indicated that the doped Cr element made dual effects on the oxidation behavior based on the varied oxidation temperatures, oxidation durations and Cr contents. At 700 °C and 740 °C, the oxidation resistance of Mo₂FeB₂-based cermets was enhanced by Cr doping less than 6 wt%, while the higher Cr content (8 wt%) reversely accelerated the oxidation rate. The positive effect was mainly derived from the formation of Cr-rich inner layer. As the oxidation temperature reached 800 °C, the superior oxidation resistance could be obtained in the first 20 h with Cr contents of 2 wt% and 4 wt% However, the longer oxidation durations or higher Cr contents could result in the swelling and cracking of oxide layer, then triggered the destructive oxidation.