The isothermal and cyclic oxidation behaviour of two Co modified aluminide coatings at high temperature

•The isothermal and cyclic oxidation tests are performed at 1000 and 1100 °C.•The addition of Co to NiAl coating reduces the oxidation resistance slightly.•CoO is easier to be formed than NiO for its lower formation energy.•The mutual diffusion rate is higher in the coating with higher Co content.

The isothermal and cyclic oxidation behaviour of two Co modified aluminide coatings together with the simple aluminide coating were performed at 1000 °C and 1100 °C. All the three coatings show a much lower oxidation rate compared with the bare alloy. Results also indicate the addition of Co to the aluminide coating decreases the oxidation resistance slightly. It can be ascribed to that Co is easier to be oxidized than Ni at high temperature, and the Cr(W) rich phases which could act as a diffusion barrier are less in the coating with higher Co content.