Oxidation resistant coatings for refractory metal cermets

Refractory metal cermets have attractive mechanical properties for high temperature applications, but exhibit poor resistance to oxidation attack. A two-step coating process has been developed in order to provide an effective high temperature oxidation resistance. W–HfN and Mo–ZrN cermet samples were initially coated with a layer of Mo through a Mo(CO)6 decomposition reaction. The second step involved a co-deposition of B and Si by a pack cementation treatment. The resultant aluminoborosilicate coating exhibits good adherence to the cermet samples. Oxidation exposure at temperatures up to 1400 °C demonstrated minimal mass change and an unaltered cermet microstructure.