2013 Volume 54 Issue 8 Pages 1517-1523
Oxidation of coated and uncoated TZM alloys has been investigated under high temperature plasma flames with varying exposure time. TZM alloy specimens were pack-cemented in a powder mixture of Si, NaF and Al2O3 (25, 5 and 70 mass%) in an Ar atmosphere at 1173 K, resulting in the formation of MoSi2 and Mo5Si3 layers on the TZM alloy. When the uncoated alloy was exposed to the flame for up to 4 min, the TZM alloy specimen showed a significant weight loss. However, the MoSi2-coated TZM alloy specimen did not exhibit a measureable weight loss during the same exposure time due to the presence of the MoSi2 layer. The effect of coating layers on the oxidation of TZM alloy under the dynamic flame is discussed based on the surface morphology and the microstructural observations, together with the weight changes during the test.