High temperature tensile and creep behaviour of low pressure plasma-sprayed NiCoCrAlY coating alloy

Abstract

NiCoCrAlY overlay coatings are used on high temperature superalloy components in some aircraft gas turbine engines. In this work, the high temperature tensile and creep behavior of low pressure plasma-sprayed plates of a typical NiCoCrAlY alloy has been studied. From room temperature to 800 K, the NiCoCrAlY alloy studied has nearly a constant low ductility and a high strength. At higher temperatures, it becomes weak and highly ductile. At and above 1123 K, the behavior is highly dependent on strain rate and exhibits classic superplastic characteristics with a high ductility at intermediate strain rates and a strain rate sensitivity of about 0.5. At either higher or lower strain rates, the ductility decreases and the strain rate sensitivities are about 0.2. In the superplastic deformation range, the activation energy for creep is 120 ± 20 kJ mol −1, suggesting a diffusion-aided grain boundary sliding mechanism. Outside the superplastic range, the activation energy for creep is calculated to be 290 ± 20 kJ mol −1.