为了提高热锻模具的高温磨损性能, 以H13钢为基体材料, 采用半导体激光器在其表面激光熔覆Co基WC复合粉末。通过显微硬度计、扫描电子显微镜、X射线衍射仪、高温摩擦磨损试验机对熔覆层的硬度、显微组织和高温耐磨性进行了研究。结果表明, 激光熔覆后涂层的显微硬度和高温磨损性能在很大程度上得到了提高。经分析, 该涂层主要组成相为过饱和固溶体Co, 硬质相CoCx、Fe3W3C、(Cr, Fe)23C6等。涂层在600 ℃高温磨损过程中, 一方面, 硬度相对较低的富Co区先磨损, 使硬度较高的碳化物硬质相凸显出表面, 阻止了对磨材料的磨损作用; 另一方面, Co、Cr元素在高温摩擦过程中促进了具有润滑作用的氧化膜CoO、CoO·Cr2O3的形成, 使摩擦系数降低, 从而使得熔覆层的高温耐磨性提高了2 倍左右。熔覆层高温磨损机制主要以磨粒磨损和粘着磨损为主。

In order to improve the high temperature wear resistance of hot-forging die, the Co-based WC composite power was cladded by diode laser on the surface of H13 substrate. The microhardness, microstructure and performance of high temperature were resistance of the coating are tested by micro-hardness tester, scanning electronic microscope, X-ray diffraction, high-temperature friction and wear tester respectively. The results show that the microhardness and high temperature wear resistance of coating are greatly improved after laser cladding. The XRD profile indicates that, the coating mainly consists of supersaturated solid solution of Co, hard phase CoCx, Fe3W3C, (Cr, Fe)23C6. During the process of high temperature wear testing at 600 ℃, on the one hand, the rich Co zone with relatively low hardness wore firstly, which made the carbide hard phase with relatively high hardness upon the surface, preventing the wear of the grinding material; on the other hand, the high temperature friction process facilitated the transition from Co, Cr elements to lubricating oxidation films of CoO and CoO·Cr2O3, which lowered the friction coefficient. After laser cladding, the high-temperature wear resistance of the coating increases about two times related to the substrate. The wear mechanism of cladding coating is dominated by abrasive wear and adhesive wear during high temperature wear process.