The behavior of MCrAlY coatings on Ni 3Al-base superalloy

Abstract

This work is concerned with NiCrAlY and NiCoCrAlY coatings deposited on the superalloy IC-6 (Ni 3Al-base superalloy) by arc ion plating (AIP). The results indicated that the presence of Al and Mo in alloy IC-6 impeded Cr atoms moving from coatings to substrates during the deposition process. As a consequence, the distribution of Cr is well proportioned in both NiCrAlY and NiCoCrAlY coatings. Vacuum heat treatment drastically increased diffusivities and the coating became more uniform. The interdiffusion also led to the phase transformation in the coatings. Although γ′-Ni 3Al and γ-Ni were still the major phases in the coating, their lattice constant a 0 decreased. The results of isothermal oxidation showed that the oxidation behavior of coatings obeyed the parabolic rate law. The oxidation resistance was not influenced very much by the presence of Co in the NiCrAlY coating at 900 °C static atmosphere. NiCoCrAlY coating had poorer oxidation resistance than NiCrAlY coating when they were exposed at 1000 °C.