The objective of this study is to prepare nickel-based coatings using laser-cladding technology and adding appropriate amounts of WC particles to enhance the quality of the cladding layer. This addition significantly increases the hardness, wear resistance, high-temperature performance, and corrosion resistance of the coatings. The morphology, size, addition ratio, and distribution of the WC particles have a significant impact on the structure and properties of the coatings. The microstructure, elemental composition, and phase distribution of the coatings vary with different laser-processing parameters. Therefore, controlling the WC content is crucial for manipulating the structure, morphology, and types of phases formed in the coatings and reducing defects, which is essential for regulating the microstructure of the cladding layers. In this study, nickel-based composite coatings are prepared using laser-cladding technology, with the addition of a WC ceramic-reinforcing phase. The aim of this study is to investigate the microstructural changes in WC particles in nickel-based cladding layers and their reinforcement mechanisms. This study also examines the effect of WC particles and their contents on the phase composition, microhardness, and corrosion resistance of the cladding layers. Additionally, the friction and wear performances and mechanisms of the nickel-based cladding layers under ambient- and high-temperature conditions are explored to fabricate high-hardness and wear-resistant nickel-based ceramic-particle composite coatings. This study aims to effectively enhance the properties of the substrate and provide insights for future applications.

The Ni-0%WC cladding layer comprises phases such as γ-(Fe,Ni), Ni₃Fe, and Cr₂₃C₆. When WC is introduced, novel phases including Fe₃W₃C and W₂C emerge within the nickel-based cladding layer alongside the WC phase (Fig. 3). A metallurgical bond forms between the nickel-based cladding layer and the substrate, giving rise to planar crystals. At WC mass fraction of 5%, considerable residual stress is observed at the base of the cladding layer, rendering it prone to crack formation (Fig. 5). The inclusion of WC leads to an increase in the eutectic structure within the cladding layer, coupled with a marked reduction in both the quantity and size of the dendrites. Upon reaching a 15% WC mass fraction , the morphology of the eutectic structure transitions from dendritic to reticular. As the WC content increases, the reticular eutectic structure expands, with the tungsten atoms predominantly precipitating as blocky acicular carbides. Initially, the size of the dendrites surrounding the WC increases before subsequently diminishing; at a 35% WC mass fraction , the coarse dendrites adjacent to the WC vanish entirely (Fig. 8). The WC enhances the nucleation rates and refines the grains within the molten pool, thereby strengthening the grain refinement. A higher WC content leads to the precipitation of several phases that are evenly dispersed throughout the cladding layer, thereby strengthening the dispersion. Consequently, as the WC content increases, the microhardness of the cladding layer progressively rises. Upon reaching a 35% WC mass fraction , the average microhardness reaches 841.39 HV, marking a 3.2-fold increase compared to that of the substrate (Fig. 10). Notably, the nickel-based cladding layer significantly boosts the wear resistance of the substrate (Fig. 11). The wear mechanisms observed in the substrate include adhesive wear, microcutting, and oxidative wear, which are characterized by pronounced surface plastic deformation and elevated friction coefficients (Fig. 12). The addition of WC effectively mitigates plastic deformation during the wear process in the cladding layer, thereby reducing the friction coefficient. Nevertheless, the high hardness and low toughness of the precipitated hard phases may cause cracks to form on the cladding-layer surface, with the resulting debris being trapped between the friction pairs, amplifying the surface friction coefficient (Fig. 14). Correspondingly, as the WC content increases, the wear loss of the cladding layer gradually decreases (Fig. 16). In comparison to the substrate, the nickel-based cladding layer markedly enhances the high-temperature wear resistance (Fig. 18). While the substrate exhibits relatively poor corrosion resistance, characterized by severe surface corrosion, the Ni-0%WC cladding layer generates passive films on the anode surface, bolstering the corrosion resistance chiefly through intergranular corrosion mechanisms (Fig. 20). However, with the addition of WC, the defects in the cladding layer escalate, leading to an uneven distribution of the passive film, thereby fostering localized microcell formation and the emergence of numerous pitting-corrosion spots. Despite a marginal decrease in corrosion resistance, the overall impact remains minimal (Fig. 21).

Using 45 steel as the substrate, Ni60 alloy powder was mixed with spherical cast WC particles to prepare the cladding powder. The mixture was then subjected to uniform mixing through ball milling and vacuum drying. After cleaning and preheating, Ar gas was employed as the shielding gas and carrier during the cladding process. The cladding was conducted using a coaxial powder-feeding method on a laser-cladding machine to create a single-layer multi-pass cladding layer. The microstructure and phase composition of the cladding layers were analyzed using optical microscopy, scanning electron microscope, and X-ray diffraction. The microhardness and corrosion resistance of the cladding layers were evaluated using a Vickers hardness tester and electrochemical workstation, respectively. Furthermore, the wear resistance of the cladding layers was examined under both ambient- and high-temperature conditions using a friction and wear testing machine.

The research findings delineate the profound impact of different WC contents on the phase composition, microstructure, microhardness, wear resistance, and corrosion resistance of the nickel-based composite coatings. The cladding composite coatings bond robustly with the substrate, encompassing phases such as γ-(Fe,Ni), Ni₃Fe, and Cr₂₃C₆. Adding WC notably reduces the dendrite size and quantity within the cladding layers, accompanied by an augmentation in the eutectic structures. Incrementally increasing the WC content precipitates harder phases, consequently elevating the microhardness of the cladding layers, and culminating in an average hardness of 841.39 HV at 35% WC mass fraction , approximately 3.2 times higher than that of the substrate. Moreover, incorporating WC substantially increases the wear resistance of the cladding layers, thereby alleviating adhesion. Nonetheless, a WC mass fraction exceeding 25% could potentially instigate brittleness and fatigue cracking. In contrast to the substrate, the nickel-based cladding layers show amplified high-temperature wear resistance and markedly enhance the corrosion resistance of the substrate, despite a marginal decline in corrosion resistance due to the addition of WC.