Pulsed laser cladding on IN718 alloy using pre-coated CrCoNi-TiC/SiC powders for enhancing wear resistance

Abstract

By employing a pulsed laser, laser cladding was performed on IN718 alloy pre-coated with CrCoNi-TiC/SiC powders and three defect-free coatings were prepared successfully. Microstructures of these coatings were subjected to dedicated characterization and well correlated with their surface performances (hardness/wear resistance). The CrCoNi coating was found to be predominantly composed of coarse grains. The addition of TiC and SiC powders will not only generate fine carbides dispersed in the coatings but also lead to the changes of grain and substructure morphologies through modifying the solidification thermodynamics in the cladding zone. The CrCoNi-TiC and the CrCoNi-SiC coatings have average grain sizes of 8.1 ± 7.9 μm and 6.6 ± 5.6 μm, respectively, much smaller than that of the CrCoNi coating (19.3 ± 19.2 μm), indicating effective grain refinement after incorporating such carbides. The average hardness values of CrCoNi-TiC and the CrCoNi-SiC coatings are measured as 315.9 ± 5.3 HV and 321.8 ± 8.6 HV, respectively, considerably higher than those of the CrCoNi coating (265.3 ± 6.9 HV) and the substrate (255.3 ± 4.5 HV). Both the composite coatings also have lower wear rates (6.6 × 10−4 mm3·N−1·m−1 for the CrCoNi-TiC coating and 2.9 × 10−4 mm3·N−1·m−1 for the CrCoNi-SiC coating) than the CrCoNi coating (9.3 × 10−4 mm3·N−1·m−1) and the IN718 substrate (11.1 × 10−4 mm3·N−1·m−1). Based on dedicated microstructural analyses, the synergistic strengthening effects due to grain refinement, second phase particles, and solid solution of alloying elements are found to have contributed to the superior surface performances of both the composite coatings, with the SiC demonstrated to be a more effective additive.