Fangyan Luo

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.

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.

The 316L SS surfaces were prepared with CoCrFeNi HEA/W-composite coatings using the laser cladding technique with various mass fractions of W. The mass fractions of W were 10, 20, 30, and 40%. The microstructure of the HEA/W-composite coatings was investigated using a variety of characterization methods. According to the results, the samples were in the BBC phase. In the SEM images, a solid–liquid bonding layer was observed, which indicates the samples had good metallurgical bonding. The W particles prevented the orderly growth of the HEA grains, and a significant refinement of the grains around the W particles occurred. The lattice constants measured by XRD mapping indicate that adding W particles to CoCrFeNi HEA leads to lattice distortion. The hardness of the HEA/W coatings was substantially higher than the substrate and the pure CoCrFeNi coating by hardness measurements and was greatest at a W content of 40%. The hardness of the HEA/W coatings was significantly increased compared to the substrate and the pure CoCrFeNi coating by hardness measurements and was greatest at a W content of 40%. The HEA/W coating was tested for electrochemical corrosion, and a 10% mass fraction of W achieved the highest level of corrosion resistance.