Fenju An

This study systematically investigates the influence of laser power (1000 W, 1400 W, 1800 W) on the microstructure and properties of Ni25 alloy coatings prepared by laser cladding to optimize process parameters for enhanced comprehensive performance. Through the analysis of multi-dimensional characterization, it is found that the laser power significantly changes the thermal cycle, thus determining the evolution of microstructure. At 1000 W, a fine dendritic structure with dispersed hard phases (BNi₃, BFe₃Ni₃, CrB₂, Cr₇C₃) yielded the highest hardness (442.52 HV) but poor wear (volume loss: 0.3346 mm³) and corrosion resistance (Icorr: 2.75 × 10⁻⁴ A·cm⁻²) due to microstructural inhomogeneity. The 1400 W coating, featuring a uniform γ-Ni dendrite/eutectic network and increased B solid solubility, achieved an optimal balance with the lowest wear rate (0.0685 mm³), superior corrosion resistance (Icorr: 2.34 × 10⁻⁵; A·cm⁻²), and a stable friction coefficient (0.816), despite lower hardness (342.00 HV). At 1800 W, grain coarseness and Cr₇C₃ decomposition led to blocky hard phases, recovering hardness (415.36 HV) and reducing the friction coefficient (0.757), but resulting in intermediate wear and corrosion resistance. This study demonstrates that the uniformity and continuity of the microstructure are the key determinants governing the comprehensive service properties of the laser cladding layer, with their importance outweighing a single hardness index. 1400 W is identified as the optimal laser power, providing critical insights for fabricating high-performance Ni25 coatings in demanding service environments.

In this study, laser melting experiments of Ni60/WC composite powder coatings were carried out using a laser, and the surface morphology and microstructure of the coatings were analyzed using a scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). In addition, hardness testing equipment was used to assess the hardness of the coatings and an electrochemical workstation was used to characterize their corrosion resistance. The key findings demonstrate substantial variations in coating performance based on remelting parameters. The coatings processed without secondary laser remelting exhibited an average hardness of 501.36 (standard deviation 154.46) HV_0.2, a self-corrosion potential of −0.039 V, and a self-corrosion current density of 8.11 × 10⁻⁴ A/cm². In contrast, some coatings were subjected to secondary remelting at 800 mm/min (S 800). The laser is used to scan the surface of the cladding with the laser on the surface of the cladding, and the speed is the feed rate of the laser scanning. XRD analysis revealed intensified main peaks, indicative of elevated solid solution and carbide content. SEM micrographs displayed fishbone-like and feather-like morphologies, with the hardness increasing to 622.98 (standard deviation 9.60) HV_0.2 and the corrosion metrics improving to −0.038 V and 2.86 × 10⁻⁵ A/cm². In contrast, coatings remelted at 600 mm/min (S600) exhibited broader but less intense XDR peaks, alongside diminished reticulation in SEM imagery. These samples demonstrated marginally lower hardness 599.91 (standard deviation 8.35) HV_0.2 but superior corrosion resistance, with a self-corrosion potential of −0.012 V and current density of 2.64 × 10⁻⁵ A/cm². The results underscore the critical influence of laser scanning velocity and remelting frequency on microstructural evolution, mechanical strength, and electrochemical stability. Enhanced hardness correlates with refined microstructural features, while enhanced corrosion resistance arises from reduced defect density and stabilized electrochemical activity.

The aim of this investigation was to examine how CeO₂ powder influences the performance of WC + Ni60 composite powder. Various cladding layers of WC + Ni60, incorporating differing mass fractions of CeO₂, were created on the surface of Q235 steel utilizing laser cladding technology. To analyze the microscopic structure of the resulting cladding layer, scanning electron microscopy was employed. Additionally, the abrasion and corrosion resistance properties were assessed through experimentation with a pin-and-disc friction and wear tester and an electrochemical workstation, respectively. The results of the study showed that when the mass fraction of CeO₂ was 1%, the grain on the surface of the coating was refined, the carbide formation was reduced, and the uniformity of the cladding layer was the best. In terms of corrosion resistance, the coating with 1% CeO₂ had a self-corrosion potential of 0.07 V and a self-corrosion current density of 1.82 × 10⁻⁵ A·cm⁻², showing the best corrosion resistance, and the coating self-corrosion potential was higher than that of the coating and substrate without CeO₂. In terms of abrasion resistance, coatings with 1% CeO₂ had a lower coefficient of friction (0.47) and a smaller wear rate 0.034 mm³, and the wear amount was only 23.5% of that of coatings without CeO₂, resulting in the best wear resistance. In conclusion, coatings containing 1% CeO₂ exhibit the minimal coefficient of friction and the lowest wear rates, while simultaneously providing optimal corrosion resistance.

In order to study the effect of laser remelting on the properties of Q235 steel, WC-enhanced nickel-based remelted layers at different powers were prepared on the surface of Q235 steel using laser cladding technology. Their micro-morphologies were observed using scanning electron microscopy, and their hardness and corrosion resistance were tested using a Vickers hardness tester and an electrochemical workstation. The results show that when the laser power reached 1600 W, the number of WC particles was reduced, the fragments of the broken reinforcement particles were more evenly distributed, the fused layer had the highest uniformity, and the microhardness was more average. Additionally, the corrosion current density reached 2.397 × 10⁻⁵ A/cm², the self-corrosion potential E_corr of the remelted coatings was positive relative to the substrate, the corrosion resistance was the highest, the coating was uniformly flat, and its hardness was the highest.