关键词: 等离子堆焊, 双送粉, Ni60A/WC复合涂层, 物相, 硬度, 热疲劳性

Abstract: An external powder feeding system was combined with plasma surfacing equipment to establish a dual powder feeding channel. Under different external WC powder feeding rates, Ni60A/WC composite coatings were prepared on H13 steel, and compared with the Ni60A/WC coatings prepared by the built-in single powder feeding method. The coatings were evaluated by means of microscopic morphology observation, XRD analysis, microhardness test and thermal fatigue test. The results show that when the external WC powder feeding rate of the dual powder feeding system exceeds 6 g/min, the WC particles in the prepared coating are uniformly distributed. The phases of the coatings prepared by the two methods are all γ-(Fe, Ni) solid solution, Cr₇C₃, Cr₂₃C₆, Cr₃C₂ and Cr₄Ni₁₅W. The hardness of the coating prepared by the dual powder feeding method is higher than that prepared by the single powder feeding method, and as the external WC powder feeding rate increases, the hardness also increases accordingly. Cracks occur in the coatings prepared by both methods after the thermal fatigue test. The thermal fatigue cracks are concentrated at the fusion lines of the coatings and around the WC particles, and as the external WC powder feeding rate increases, the number of cracks appearing in the coatings increases accordingly. Comprehensive comparison shows that when the external powder feeding rate of the dual powder feeding system is 8 g/min, the overall performance of the coating is the best.

Key words: plasma surfacing, dual powder feeding, Ni60A/WC composite coating, phase composition, hardness, thermal fatigue resistance