Abstract
Under starved lubrication conditions, gears are subjected to excessive wear and are therefore prone to failure. The laser cladding of nano titanium carbide (TiC) composite functional gradient coatings on a gear’s surface is an effective way to improve the wear resistance and service life of the latter. In this paper, a laser-cladded gradient coating was prepared on a 40Cr gear steel surface using a pre-prepared nano-TiC powder and a 12CrNi2 powder. During the preparation of the coating, the nano-TiC powder was gradually increased along the gradient direction. The phase composition and microstructure of the coating material were then characterized by scanning X-ray diffraction (XRD) and scanning electron microscopy (SEM). The respective surface roughness, micro-hardness and wear resistance of the gradient coatings were also tested. The results showed that the TiC was transformed from nanoceramic particles embedded in the coating interior to an agglomerated large-volume hard phase structure as the pre-prepared nano-TiC powder increased. The micro-hardness gradually increased from 612 HV at the bottom of the gradient coating to 1088 HV at the top. With the increase in micro-hardness and the transformation of TiC into a hard phase, the gradient coating showed a 50% reduction in friction coefficient, a 40% reduction in grinding loss, and a significant increase in wear resistance under heavy load and starved lubricant conditions. The research further showed that the nano-TiC gradient functional coating is an ideal choice for improving the service life of gear.
Published Version
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