Effect of laser remelting treatment on the tribological properties of plasma sprayed WC–Cr3C2–Ni reinforced NiCrBSi coatings

Abstract

The incorporation of single hard phases, such as tungsten carbide (WC), and chromium carbide (Cr3C2), into NiCrBSi coatings effectively enhances their performance, thereby fulfilling the tough requirements of high-temperature friction condition. To investigate the collaborative reinforcing effect of multiple hard phases and further enhance the high-temperature wear resistance of the coating, a novel WC–Cr3C2–NiCrBSi binary hard phase reinforced coating was developed and subjected to laser remelting treatment. The as-sprayed coatings demonstrate a distinct lamellar structure that diminishes upon remelting, resulting in significant densification of the coatings and a reduction in porosity to 0.3 %. The microhardness of the remelting coatings is reduced by about 10 % due to dilution of the coating by the lower hardness of the base material. However, during the laser remelting process, WC and Cr3C2 decompose and dissolve into the alloying binder phase of the coating, serving as solid solution agents. In cases where the concentration of W elements is elevated, a considerable precipitation of W-rich carbide is observed within the coating. Notably, N30 coatings demonstrate remarkable were resistance at both ambient and 700 °C, resulting in a significant reduction in wear volume by 86.5 % and 55.2 % respectively in comparison to original NiCrBSi coatings. The remelting treatment enhances the densification of the coating, improves the homogeneity of the microstructure, and reduces the coefficient of friction of the coating. The laser-remelted coating exhibits a decreased wear volume, attributed to a transition in its wear mechanism from fatigue-dominated to abrasive wear at room temperature. Conversely, under frictional conditions at 700 °C, the remelted coating experiences an augmented wear volume, attributed to severe abrasive wear.