Research on the effect of the variation of laser power on the contour control and performance control of laser cladding Ni60CuMo/IN718 coating on RuT300

Abstract

To improve the wear resistance of Vermicular cast iron (RuT300) surface and overcome the crack inhibition bottleneck of high-hardness coating, a Ni60CuMo/IN718 composite coating was fabricated on RuT300 surface. Results indicate the cracking-free coating with a maximum hardness of 475 HV0.5 at 800 W. In addition, the hard phases MC (M=Nb, Ti), Cr7C3, CrB and the self-lubricating phase Cu3.8Ni were in-situ synthesized in the coating. Increasing laser power raised C content from substrate in the molten pool, providing more C elements for in-situ synthesized Cr7C3. Along with the consumption of Cr by carbide generation, the Cr content used for in-situ synthesized CrB decreases. Moreover, the hardness of Cr7C3 is lower than that of CrB, and the low-hardness Fe in the substrate intensifies the coatings dilution with the increasing power. Therefore, these effects result in a non-positive correlation between the increase of laser power and the coatings hardness. Due to the better anti-wear effect of the high hardness coating, the hardest coatings have the lowest wear rates at room temperature (RT). Abrasive wear is the primary wear mechanism for these coatings at RT. Fe2O3 generated by high temperature friction plays a lubricating effect, but the coating with the low hardness softened by high temperature is not conducive to the compaction and forming of the oxide film. As a result, coatings that produce a moderate oxide film at 300 °C and 500 °C have a lower wear rate in the same environment. The main wear mechanism for the coatings is oxidative wear.