Investigation on the effects of Zr alloying on in-situ synthesis of dual-scale reinforcement and wear resistance of wide-band laser clad nickel composite coatings

Nickel based composite coatings were prepared by wide-band laser cladding technology. The cladding process involved inducing the dissolution of WC particles within the laser molten pool through the application of a rectangular spot with uniform energy density. Additionally, Zr alloying was strategically employed to modulate the in-situ reinforced phase synthesis reaction. By analyzing the microstructure, phase composition, microhardness, and wear properties of the cladding layers, the influences of Zr alloying on both the microstructure evolution and reinforce mechanism of wear resistance of the cladding layers were discussed. XRD analysis showed that the in-situ precipitated phases within the laser molten pool were composed of massive (Cr, W)7C3 , (Cr, W)3C2, granular ZrC, and lamellar Cr23C6. Element map scanning analysis indicates the precipitated phases were enriched in Cr, C and W elements. It is suggested that the tungsten elements were involved in the synthesis of the in-situ reinforced phase by replacement solid solution. The Zr element precipitates primarily in the form of fine granular ZrC, which is concentrated in the vicinity of the primary precipitated phase to form a high-density secondary strengthening phase. With the increasing of Zr content, notable refinement and homogenization of the massive precipitated phase could be observed. The microhardness analysis indicates that the cladding layers achieved the highest average microhardness of 842 HV. The lowest wear weight loss rate was only 2.04 x 10-5 g/ m. The Zr addition of 4 wt% cladding layer exhibited superior wear resistance and high microhardness. In summary, the addition of Zr in the molten pool led to in-situ synthesized dual-scale reinforced particles, ultimately leading to greatly refined microstructure and enhanced coating performance.