Microstructure and oxidation behaviour of Pt modified NiCrAlYSi coating on a Ni-based single crystal superalloy

In this study, the Pt + NiCrAlYSi coating and NiCrAlYSi+Pt coating were produced onto the Ni-based single crystal superalloy by using the arc ion plating (AIP) and electroplating. For the Pt + NiCrAlYSi coating, the Pt mainly distributed in substrate and the bottom of coating, while the Pt primarily located at the outer part of NiCrAlYSi+Pt coating. After isothermal oxidation at 1100 °C, the weight gains for the NiCrAlYSi coating, Pt + NiCrAlYSi coating and NiCrAlYSi+Pt coating were 1.81 mg/cm2, 1.68 mg/cm2 and 1.37 mg/cm2, respectively. The parabolic rate constant of the NiCrAlYSi+Pt coating was 6.2 × 10−3 mg2 cm−4 h−1, which was the smallest among three kinds of coatings. The mass of spalled oxides for the NiCrAlYSi coating, Pt + NiCrAlYSi coating and NiCrAlYSi+Pt coating were 2.07 mg/cm2, 0.937 mg/cm2 and 0.801 mg/cm2 after cyclic oxidation at 1150 °C. So, the addition of Pt in the NiCrAlYSi coating can significantly improve the adhesion of alumina scale. The oxidation test results indicated that the NiCrAlYSi+Pt coating showed the best oxidation resistance. Some Pt-rich particles were observed on the surface of the NiCrAlYSi+Pt coating after 1 cycle at 1150 °C. The enrichment of Pt on the outer part of NiCrAlYSi+Pt coating can increase the out diffusion flux of Al and promote the fast formation of pure Al2O3 at the early stage of oxidation.