Influence of Al2O3 Content on the Mechanical Properties of Cold-Sprayed NiAl-Al2O3 Composite Coating by Plasma Activated Sintering

Ni/Al-Al₂O₃ composite coatings with Al₂O₃ contents up to 60vol.% were deposited by cold spraying using the mechanically alloyed Ni/Al-Al₂O₃ composite powders. Dense intermetallics based NiAl-Al₂O₃ composite coatings were prepared by plasma activated sintering of the as-cold-sprayed Ni/Al-Al₂O₃ composite. The effect of Al₂O₃ content on the microhardness and elastic modulus of the coatings was investigated to aim at correlating the microstructure and the mechanical property of the cold-sprayed composite coatings. Results showed that the angular morphology of Al₂O₃ particles in the as-cold-sprayed coatings changed to a near spherical morphology after sintering, possibly owing to the partially melting of Al₂O₃ particles. Compared to the porous structure of the NiAl intermetallics formed by self-propagating high-temperature synthesis, the cold-sprayed NiAl based composed coatings presented a dense microstructure, which was formed through the diffusion mechanism. The microhardness of the coatings increased from Hv560 to Hv850 when the content of Al₂O₃ increased from 20vol.% to 60vol.%.