Jiang Huang

CoCrFeNi/WC-Nb high-entropy alloy (HEA) composite coating was prepared on the surface of Q235 steel by LC (laser cladding) technology, and the effects of WC and in situ NbC reinforcement on the coating were studied. The phase composition, phase characteristics, microhardness, and wear resistance of the cladding coatings were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), friction and wear tester, and X-ray photoelectron spectroscopy (XPS), and the corrosion resistance was tested by a three-electrode electrochemical workstation. The results show that the CoCrFeNi/WC-Nb HEA coating consists of FCC, WC, NbC, and Laves phases, and the reinforcing phase causes grain refinement and lattice distortion. The microhardness reached (418.29 ± 16.72) HV, which was about 2.64-times higher than that of the CoCrFeNi HEA coating. The wear rate decreased to (1.150 ± 0.11) × 10⁻⁴ mm³N⁻¹m⁻¹, which was about 0.25 times that of the CoCrFeNi HEA coating, and the wear of the coating changed from abrasive wear to adhesive wear. The corrosion current density and corrosion voltage of the CoCrFeNi/WC-Nb HEA coating are (3.3820 ± 0.2103) × 10⁻⁶ A/cm² and −(0.7650 ± 0.0850) V, respectively.

HfC possesses high hardness, high melting point, and excellent thermal stability, and is regarded as an important wear-resistant reinforcing phase material. In this study, the laser cladding technique was employed to fabricate CoCrFeNiTi and CoCrFeNiTi/HfC composite coatings on the surface of Q235 substrate. The influence of HfC addition on the phase structure evolution, microstructure, and wear resistance of the coatings was systematically investigated. The results showed that the addition of HfC did not alter the phase structure of the coating, which remained dominated by an FCC solid solution. However, they induced the formation of an in situ TiC strengthening phase and reduced the brittle Laves phase content, thereby optimizing the coating’s toughness. At the same time, the coating transformed from columnar to equiaxed crystals, with significantly finer grains and further improved structural uniformity. Compared with the CoCrFeNiTi coating, the CoCrFeNiTi/HfC composite coating exhibited a more stable friction coefficient, a significantly lower wear rate, and improved wear resistance by approximately 2.4 times. The performance improvement was mainly attributed to the load-bearing strengthening and crack-pinning effect of the in situ TiC, the inhibitory effect of the reduction in the Laves brittle phase on adhesive wear, and the synergistic effect of Hf, which forms a stable oxidation-protective film during friction.

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 paper, the preparation of Ni60 + WC/NbC composite coating by laser cladding technology was studied. The coating properties were analyzed by a scanning electron microscope (SEM), an energy dispersion spectroscope (EDS), X-ray diffraction (XRD), a hardness tester, and a friction and wear tester. The results show that WC and NbC, as two typical ceramic reinforcing phases, play a positive role in improving the wear resistance and hardness of the coating. Under the action of a high-temperature (about 2500 °C) laser beam, some complex compounds, such as Ni₃Fe and M₂₃C₆ (M=Fe, Cr) are formed in the coating, which leads to the left deviation of XRD peak position. With the decrease in WC and the increase in Nb particles, the wear mechanism of the coating changes from abrasive wear to adhesive wear. When adding 10% WC, the microhardness of the coating reaches 809.5 HV, the coefficient of friction is 0.496, and the wear rate is 1.1804 × 10⁻⁷ mm³ N⁻¹·m⁻¹, which shows the best wear resistance.

In this study, 20 wt.% of Nb was incorporated into a CrFeNi medium-entropy alloy (MEA) powder system to prepare CrFeNi-Nb composite coatings on a Q235B mild steel substrate by laser cladding technology. The effects of Nb addition on the phase composition, microstructure, and wear resistance of CrFeNi coatings were systematically investigated. Microstructural characterization revealed that the CrFeNi coating exhibited a single face-centered cubic (FCC) phase structure, while the CrFeNi-Nb composite coating demonstrated a dual-phase structure comprising FCC phase and Laves phase. The Laves phase significantly enhanced the microhardness and wear resistance of the coating. The average microhardness of the CrFeNi-Nb coating increased by 259.62% compared to the substrate and 190.58% compared to the Nb-free CrFeNi coating. The average coefficient of friction (COF) of the coating decreased from 0.74 to 0.68; the wear rate reduced from 5.77 × 10⁻⁴ mm³ N⁻¹ m⁻¹ to 2.26 × 10⁻⁴ mm³ N⁻¹ m⁻¹; and the weight loss decreased from 10.77 mg to 4.3 mg. The experimental results demonstrated that the addition of Nb promoted the formation of the Laves phase in the CrFeNi MEA, which effectively improved the wear resistance of the coating.

This research delves into the corrosion resistance and wear behavior of Ni60-based composite coatings strengthened by TiC and NbC particles, which are produced by laser cladding. Three distinct coatings were prepared: S1 (Ni60 + 20%TiC), S2 (Ni60 + 10%TiC + 10%NbC), and S3 (Ni60 + 20%NbC). Microstructural characterization revealed that the addition of TiC and NbC altered phase composition, inducing lattice distortion and promoting the formation of carbides such as Cr₇C₃, Ni₃C, and Nb₂C. The S2 coating exhibited the highest average microhardness (1045 HV) due to synergistic grain refinement and homogeneous carbide dispersion. Wear resistance followed the order S2 > S3 > S1, attributed to the optimized balance of hard-phase distribution and reduced abrasive wear. Electrochemical tests in 3.5 wt% NaCl solution demonstrated superior corrosion resistance for S3, characterized by the lowest corrosion current density (1.732 × 10⁻⁶ A/cm²) and a stable passivation film, facilitated by NbC-induced oxide formation. While S2 achieved peak mechanical performance, S3 excelled in corrosion resistance, highlighting the trade-off between carbide reinforcement and electrochemical stability. This work underscores the potential of tailoring dual-carbide systems in Ni60 coatings to enhance durability in harsh 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.