The intermediate and high-temperature oxidation behaviour of (Mo,X)Si-2 (X=W,Ta) intermetallic alloys

The oxidation behaviour of (Mo,X)Si-2 (X = W, Ta) alloys was studied at low (773 K) and high temperatures (1073, 1673 K). W and/or Ta additions did not suppress pest oxidation which was shifted slightly to temperatures higher than 773 K by Ta. Mo and Si were detected in the oxides formed in pest oxidation. All alloys exhibited low oxidation rates at T > 1000 K. A silica scale was formed at T > 1600 K. The scale thickness depended;on alloy composition with the thinner scale formed on the alloys with Ta addition. Formation of Mo5Si3 beneath the scale was not detected. (C) 1997 Elsevier Science Limited.