Effect of WC particle size on the microstructural evolution and tribological properties of laser cladding Ti-bearing Co-based WC reinforced coating

To improve the wear resistance of 300 M steel under reciprocating wear in landing gear shock strut, Ti-bearing Co-based WC reinforced coatings with three different WC particle sizes (280 mesh, 200 mesh, and 150-300 mesh) were successfully fabricated by laser cladding method. The effect of WC particle size on phase composition, microstructure, microhardness and tribological properties were systematically investigated. The results show that the phase composition of these coatings consists mainly of gamma-Co, TiC, WC, Cr23C6 and CrCo, and that varying the WC particle size changes the morphologies of the second phases. With the increase of WC particle size, the morphology of TiC is dendritic, ellipsoidal and block, respectively; the morphology of Cr23C6 changes from discontinuous fine particles to grid-like at grain boundaries. And the TiC-WC composite phases appear when the particle size of the added WC particles is a mixture. The coating with a mixture of 150-300 mesh WC particles, has the highest hardness range, the lowest average friction coefficient of 0.372, and the lowest wear rate of 9.61 x 10(-5) mm(3)/N<middle dot>m. The wear mechanisms of all three coatings are abrasive wear and oxidation wear, and the oxide film on the worn surface of the coatings gradually becomes denser and more continuous with increasing WC particle size.