Wear mechanisms and micro-evaluation on WC particles investigation of WC-Fe composite coatings fabricated by laser cladding

With WC as the reinforcing phase particles, the Fe-WC composite coatings with mass fractions 0-60 wt% of WC were fabricated on a 15CrNiMo cone bit steel by laser cladding. The phase composition, microstructure, microhardness, friction and wear properties of the composite coatings were studied. Moreover, special attention was paid to investigate the thermal damage forms of WC particles and its influence mechanism on the structure evolution and wear properties. The research results reveal that most of the WC particles maintain their complete morphology, but some WC particles are melted due to the thermal damage type of dissolution-collapseprecipitation. The degree of burning loss rate is related to the quantity distribution and average particle size of WC in local area. Main surrounding structures of WC are composed of equiaxed and cellular crystals, and few short columnar crystals. The microhardness of the WC-Fe composite coating increases with increasing WC particles content. Compared with the microhardness (621.7HV(0.2)) of the Fe-based coating, the microhardness of the WC-Fe composite coating gradually increased from 729.9HV(0.2) to 1029.2HV(0.2), and its average relative wear resistance is 1.3 times that of the coating without WC particles. Moreover, combined with existing WC and W2C, as well as the presence of precipitated M23C6, M7C3 and eta phases, which significantly improve the wear resistance of WC-Fe composite coatings. In summary, the main wear mechanisms of Fe-based coatings reinforced by WC particles are abrasive wear accompanied by varying degrees of adhesive wear and three-body abrasive wear.

Automated summary

The Fe-WC composite coatings fabricated by laser cladding on 15CrNiMo cone bit steel show enhanced microhardness and wear resistance, mainly due to the reinforcement of WC particles, which significantly improve the wear performance of the coatings.