低含量碳化钨对激光熔覆镍基复合涂层性能影响

Effect of Low Content of Tungsten Carbide on the Performance of Nickel-Based Composite Coatings by Laser Cladding

为研究相对较低含量(质量分数≤15%)碳化钨镍基合金涂层中碳化钨对涂层性能的影响,采用激光熔覆技术在316L不锈钢基体上制备了不同碳化钨含量镍基碳化钨复合涂层,表征其组织形貌,同时对比分析不同碳化钨含量复合涂层的硬度、耐磨性。结果表明,涂层熔道顶部搭接处存在明显的分界线,分界线上侧为细小等轴晶,下侧为粗大的柱状晶;碳化钨颗粒周围微熔形成析出物,同时在熔池底部有聚集趋势,且随碳化钨含量增大聚集趋势增大;镍基复合涂层硬度和耐磨性随添加碳化钨含量增大而提升,15%质量分数碳化钨复合涂层相较于纯镍熔覆涂层硬度提高约12.88%,摩擦因数降低约19.62%,磨痕形貌显示低含量碳化钨复合涂层中硬质颗粒的耐磨支撑作用相对较弱,复合涂层整体硬度提升是耐磨性能增强的主要因素。

In order to study the influence of tungsten carbide(WC) dispersions on the mechanical properties of nickel-based alloy coatings, the composite coatings with different mass fractions of tungsten carbide(≤15%) were fabricated on 316L stainless steel substrate by laser cladding(LC) technique. The microstructures and mechanical properties, e.g. hardness and wear resistance, which are related to the composite coatings with different WC contents were characterized and analyzed by scanning electron microscopy(SEM) and tribology testings, respectively. Results show that the melting pool exhibits an obvious bimodal structures at the top of the overlaps where the fine equiaxed grains are on the top of the coarse columnar grains. Due to the gravity effect, the heavy WC particles is tend to aggregate at the bottom of melting pool, and the tendency of uneven dispersion of WC particles increases with the higher of WC concentrations. The hardness and wear resistance of WC/nickel-based composite coatings were also enhanced with the increments of WC additions. Hardness of 15% WC/nickel-based composite coatings increased about 11.4% with a large reduction in the friction coefficient by about 19.62% compared with the pure nickel claddings, and the abrasion morphology showed that the wear-resistance enhancements of hard particles in low content WC/nickel-based composite coatings was relatively weak. The improvement of the wear resistance of the composite is mainly attributed to the increase of overall hardness of composite coatings.