Failure mode and fatigue mechanism of laser-remelted plasma-sprayed Ni alloy coatings in rolling contact

The failure mode and rolling contact fatigue failure mechanism of the laser-melted plasma-sprayed coatings were investigated in this paper. The coating was deposited by using a high-efficiency plasma spraying system and remelted by using a CO2 laser in a continuous mode. Thirteen rolling contact tests were performed to obtain the statistical result at an identical condition. Experimental results showed that spalling is the main failure mode of the remelted coating in rolling contact. Prior to the formation of the spall, the surface main crack and ring-type crack have been generated. However, only the main crack might not directly cause the formation of the spall. The joining of the ring-type cracks and subsurface branched cracks was directly responsible for the spall formation.