Effect of Al Layer on Oxidation Behavior of NbCrAl Coating

NbCrAl coatings in the presence or absence of Al outer layer were prepared on C103 Nb based alloy and alumina substrate by direct current magnetron sputtering technique. The oxidation performance of coating systems was evaluated by isothermal oxidation tests. The element diffusion and oxidation behavior of the coating systems were investigated. The results indicate that the mass gains of NbCrAl and Al/NbCrAl coatings are 2.02 mg/cm 2 and 0.79 mg/cm 2 at 1 000 °C for short time. Al/NbCrAl coatings exhibit more effective protection than NbCrAl coatings. The addition of Al layer can improve the oxidation resistance of NbCrAl coatings, which is attributed to the Al layer offering enough Al content to react with oxygen to form a continuous and dense Al 2 O 3 scale on NbCrAl coating and it can inhibit the further internal oxidation.