Oxidation behavior of Ru(Al)-RuAl intermetallic eutectics produced by ingot and powder metallurgy

Oxidation characteristics and changes in the microstructure of Ru(Al)-RuAl intermetallic eutectics produced by ingot and powder metallurgy were reported. Oxidation was conducted in air at 1100 and 1300 °C up to 100 h. It was shown that oxidation behavior is affected by the microstructure and the phase composition. At 1100 °C oxidation of the lamellar eutectic produced by ingot metallurgy resulted in formation of the external Al2O3 scale and the internal oxidation zone mostly with the periodic structure. The external Al2O3 scale was porous and nonprotective. The internal oxidation zone consisted of discontinuous bands composed of Al2O3 and Ru-rich phase. At 1300 °C the oxidation resistance and the stability of the lamellar microstructure were markedly decreased. The eutectic alloy produced by powder metallurgy was less affected by oxidation at 1100 °C than the alloy produced by ingot metallurgy and it was characterized by the absence of the periodic structure. However, both alloys generally exhibited poor oxidation resistance. The results were discussed within the context of oxidation characteristics of RuAl and other intermetallic phases.