Morphology, Microstructure and Improved Mechanical Properties of TiB2/TiB/TiN Reinforced Ti3Al Matrix Composite Coating with ZrO2 Addition

Ti3Al matrix composite coatings were synthesized on a TC4 titanium alloy with Ti, Al and BN mixed powder by in situ laser cladding. Then, the effect of ZrO2 addition to the composite coatings was investigated. The phase composition, microstructure and element distribution of the composite coatings were characterized by scanning electron microscopy, x-ray diffraction and electron probe microanalysis. Results showed that the Ti3Al matrix composite coatings were reinforced by TiB2, TiB and TiN phases. The quality and mechanical properties of the composite coating can be significantly improved with ZrO2 addition under optimum laser power of 1000 W. The microhardness of the composite coatings was 2-3 times higher than that of the substrate, and the wear resistance of the composite coating without and with ZrO2 addition was enhanced by nearly 4 and 7 times compared to the substrate. The better properties of the composite coating with ZrO2 addition were mainly attributed to the formation of a ZrO2 network. The network-like distribution of ZrO2 provided dispersion strengthening and grain refinement effects. This research is expected to provide a new coating material to obtain high-performance Ti3Al matrix composite coating.