Tribological Performance of TiB_2-Ni Composite Coating Deposited by APS

TiB2-Ni composite powders were prepared by pressurized hydrogen reduction cladding with different proportion of TiB2.The coatings were then prepared by APS.The microstructures and the phase composition of the powders as well as the deposited coatings were analyzed by scanning electron microscopy(SEM)and X-ray diffraction(XRD).The coatings were tested using a ring-on-disc tribometer from ambient temperature to 300°C.A sprayed Cr3C2-NiCr coating was tested as a reference.The morphologies of the worn surface of the coatings were observed and analyzed.It is found that the TiB2-Ni composite coatings present higher friction coefficient than that of the Cr3C2-NiCr coating at room temperature due to the adhesive wear mechanism,whereas the main wear mechanism of Cr3C2-NiCr coating is rupture and exfoliation.However,at high temperature,the friction coefficient of the TiB2-Ni composite coating decreases as a result of B2O3 solid lubricant,which alleviates the adhesive wear on coatings.Furthermore,the TiB2-Ni composite coating greatly reduces the mass loss of the boron cast iron.