Microstructures, hardness and erosion behavior of thermal sprayed and heat treated NiAl coatings with different ceria

The microstructure, hardness and erosion behavior of High velocity oxy-fuel (HVOF) thermal sprayed and heat treated NiAl intermetallic coatings with three different ceria were studied through erosion tests, Vickers hardness tests and microstructural characterizations in this paper. Test results showed that heat treatment can obviously change the erosion behavior of the HVOF thermal sprayed NiAl intermetallic coatings. After heat treatment at high temperatures, Al2O3, CeAlO3 and NiAl2O3 are formed in the NiAl intermetallic coatings. Heat treated at high temperature (above 600 °C), the NiAl intermetallic coatings were strongly softened and exhibited higher erosion rates. Work hardening occurred during the erosion test. The degree of work hardening in thermal sprayed coating is larger than that in heat-treated coatings. Erosion surface morphologies and cross sections showed that the erosion is a mixture mechanism of mainly ductile combined with partly brittle for the coatings containing ceria.