Thermal Corrosion Behavior of NiCoCrAlTaY Coating for a Ni Base Superalloy Prepared by Low Pressure Plasma Spraying

The low pressure plasma spraying (LPPS) method was used to prepare NiCoCrAlTaY bond coating on a nickel base superalloy with the composition(wt, %)of C 0.13-0.22, Cr 8.50-9.50, Co 9.0-11.0, Mo 2.50-3.50, Al 4.80-5.70, Ti 4.10-4.70, Fe ≤1.0, V 0.60-0.90, and Ni in balance. The thermal corrosion tests, including Isothermal and cycle oxidation, were conducted for the specimens of the base alloy and the alloy with coatings. The experimental results showed that the thermal spraying NiCoCrAlTaY bond coating improved the thermal corrosion resistance of the alloy significantly. It has been found that the base alloy had high weight gain of 68.91g/m2 at the test condition of 1100°C for 100hrs, while the weightl gain of the specimens of the alloy with NiCoCrAlTaY bond coating, was only -0.76∼5.72g/m2. And the slight weight loss appeared when the specimen with with NiCoCrAlTaY bond coating was treated for 40hrs at1100°C. The results also showed that the addition of tantalum element in the coating was beneficial for the thermal oxidation resistance. It has been found that after oxidation at 1100°C for 100hrs, the continued Al2O3 film nuderneath the outside layer mixture oxides of Cr, Ni, Al and Co, was formed on the substrate surface after both the isothermal oxidation and cycling oxidation. The coating has a good combination with the nickel base superalloy substrate.