Influence of Al2O3 Particle Distribution on Mechanical Properties of Cold-Sprayed NiAl-Al2O3 Composite Coating Followed by Annealing

Dense 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. The NiAl-Al₂O₃ composite coatings were prepared by annealing the cold-sprayed Ni/Al-Al₂O₃ composite coatings. The effect of Al₂O₃ particle distribution on the microhardness and elastic modulus was investigated to aim at understanding the relationship between the coating microstructure and the mechanical property. Results showed that the coating microhardness increased with the increase of Al₂O₃ content and became to decrease with the increase of Al₂O₃ content when the Al₂O₃ content was higher than 20vol.%. It was found that the Al₂O₃ particles tended to contact with each other at an Al₂O₃ content higher than 20vol.%. The decrease of the composite coating hardness at high Al₂O₃ contents was attributed to the discontinuity of NiAl matrix owing to the concentrated distribution of the Al₂O₃ particles.