Fabrication and properties of ZrC-ZrB2/Ni cermet coatings on a magnesium alloy by atmospheric plasma spraying of SHS powders

ZrB2-ZrC/Ni composite powders were successfully produced from a Ni-Zr-B4C system by self-propagating high-temperature synthesis (SHS), and ZrB2-ZrC/Ni cermet coatings were deposited on a magnesium alloy substrate by atmospheric plasma spraying (APS) using the SHS-derived powders as feedstock powders. Microstructure and phase composition of the SHS powders and APS coatings were investigated by scanning electron microscopy and X-ray diffraction, respectively. Microhardness and wear resistance of the coatings were examined by using a Vickers hardness tester and pin-on-desk tribometer. The coatings exhibited lamellar and porous structure, mainly consisting of ZrB2, ZrC and Ni in addition to the by-product ZrO2. The coatings bonded well to the substrate with the bonding strength as high as 16.27 MPa. Microhardness and wear resistance of the substrate were significantly improved by the coatings. The wear resistance of the coatings for the substrate initially increased and subsequently decreased with the increase in Ni content. The coating with 30 wt% Ni in the feedstock powder displayed the highest microhardness of 525.02±96.08 HV0.1 and the best wear resistance for the substrate.