Tuning bias voltage to enhance oxidation resistance of AlCoCrNi high-entropy alloy coatings at 1000

• Published in: Journal of alloys and compounds 2024-10, Vol.1003, p.175525, Article 175525
• Main Authors: Zhao, S.C., Jiang, X., Zhang, X.D., Chen, L., Liu, W., Li, Y.T., Leng, Y.X.
• Format: Article
• Language: English
• Subjects: Bias voltage; Grain size; High entropy alloy coatings; Oxidation resistance; Residual stress
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2024.175525

AlCoCrNi-based high-entropy alloy (HEA) coatings have emerged as promising alternatives to conventional MCrAlY coatings due to their exceptional antioxidation properties. In this study, a series of AlCoCrNi HEA coatings were synthesized by DC magnetron sputtering under various bias voltages, and their antioxidation performance were evaluated at 1000 °C in air. The applied bias voltage was found to markedly influence the coatings' grain size and residual stresses—parameters critical to their antioxidative behavior. The grain size is directly correlated with the diffusion-controlled depletion of Al, which is pivotal for the genesis and thickening of the protective α-Al2O3 layer during high-temperature oxidation. Furthermore, the residual stress of the as-deposited HEA coatings impacts the compatibility of stress between the HEA coating and thermally grown oxide (TGO) layer, thereby affecting the TGO layer integrity and protective efficacy. Notably, the coating deposited under the bias voltage of −50 V exhibits superior oxidation resistance compared to other coatings by generating a robust and dense TGO layer with large grain size. This study delves into the intrinsic mechanisms underlying the bias-induced improvement in oxidation resistance of HEA coating. •Bias voltage affects grain size and residual stresses of AlCoCrNi coatings.•Grain size affects the Al depletion controlled by diffusion and the formation of TGO.•Residual stress affects the stress matching between the TGO layer and the coating.•-50 V bias voltage provides optimum oxidation resistance due to the robust TGO layer.•Conventional belief regarding the effect of bias voltage on anti-oxidation was challenged.