Oxidation behavior of AlCoCrFeNiSix high entropy alloy bond coatings prepared by atmospheric plasma spray

To investigate the oxidation resistance of AlCoCrFeNi high entropy alloy coating and the effect of Si modification on oxidation resistance, AlCoCrFeNiSix (x = 0, 0.15, 0.3) coatings were prepared on 316 L stainless steel substrate by atmospheric plasma spray (APS). The evolution process and oxidation kinetics of the thermal grown oxide (TGO) layer at 800 °C for the three coatings were discussed, and the growth model of the TGO layer was established. The results show that the oxides tend to be preferentially generated at the particle boundaries and diffused laterally, but the Al2O3 would hinder them. The TGO layer of the three coatings transformed from the single layer to the double layer with the oxidation process, and the lower oxide layers were continuous and dense Al2O3. Spinel oxides appear in the TGO layers of the Si0 and Si0.3 coatings, but the TGO layer of the Si0.15 coating consists entirely of Al2O3 and which displays the lowest oxidation rate. Although the Si modification reduced the growth rate of the TGO layer, the content of the Si element was not proportional to the improvement of the oxidation resistance of the coating.