Influence of nanostructured ZrO2 additions on the wear resistance of Ni-based alloy coatings deposited by APS process

In the present investigation, the influence of the addition of nanostructure zirconia particles on the microstructure, micro-hardness and wear performance of a Ni-based alloy (Colmonoy 88) deposited by atmospheric plasma spraying (APS) on low carbon steel has been reported. Two different procedures were tested: (i) spraying powders of Colmonoy 88 and zirconia mixed by mechanical alloying and (ii) spraying powders separately using a dual powder injection system available at the APS equipment. The microstructure and the mechanical properties of coatings were characterized by scanning electron microscopy/energy dispersive X-ray analysis (SEM-EDS), X-ray diffraction (XRD) and micro-hardness measurements. The tribological properties were evaluated at room temperature in reciprocating sliding wear equipment. The results indicate that the as-sprayed modified coatings were mainly composed by Ni, Ni-Cr-Fe, Cr23C6, Cr5B3, and tetragonal zirconia. Evenly distribution of zirconia can be seen in the coatings produced by powders prepared by mechanical alloying, while dispersive ones can be seen in the other case. Hardness and wear resistance of coatings is increased with nanostructured zirconia additions, while their friction coefficient is decreased. Coatings produced with mechanical alloying show the highest wear resistance of all tested coatings. Nanostructured ZrO2 coating displays the worst wear resistance.