Effect of bias voltage on the oxidation resistance of NiCoCrAlYTa coatings prepared by arc ion plating

•With an increase in bias voltage, the oxidation resistance of the NiCoCrAlYTa coating by arc ion plating significantly decreased although the coating became dense•Ta played a detrimental role on the oxidation behaviour at the latter stage of the oxidation process since it could accelerate the degradation of the protective Al2O3 layer.•The degradation of the Al2O3 layer could be a gradual evolution process without cracks or spallations. The NiCoCrAlYTa coatings were prepared on the superalloy K423A by arc ion plating under different bias voltages from -50V to -150V, and the oxidation behaviour of these coatings was investigated at 1050°C for 100 h. The results showed that with an increase in bias voltage, the oxidation resistance of the coating significantly decreased although the coating became denser. Ta played a detrimental role on the oxidation behaviour at the latter stage of the oxidation process. The degradation mechanism of the protective Al2O3 layer and the oxidation model of the coating were discussed.