High Temperature Oxidation Behavior of HfH₂-CoCrAlYSi Coating Fabricated by Laser Cladding

CoCrAlYSi coating has been widely used in aero-engine for its high temperature oxidation resistance. As an additive element, Hf has been studied for improving the performance of CoCrAlYSi coating. However, there is a lack of study about the influence of Hf on the high temperature oxidation behavior of CoCrAlYSi coating. In this study, we prepared customized CoCrAlYSi coatings with various HfH2 contents by laser cladding. The microstructure evolution of CoCrAlYSi coating and formation characteristics of gamma-Co solution phases were discussed. The isothermal oxidation products and oxide films of CoCrAlYSi coating at 1100 degrees C were analyzed. Results showed that due to the addition of HfH2, the grain of CoCrAlYSi coatings was refined, together with the micro-cracks decreased. The addition of HfH2 postponed the formation of CoO during isothermal oxidation test at 1100 degrees C in synthetic air. The lack of CoO further postponed the formation of CoCr2O4, which may cause the failure of CoCrAlYSi coating. Meanwihle, the growth rate of Cr2O3 oxide film was decreased due to the addition of Hf, which led to the improvement of stability of CoCrAlYSi coating.