激光熔覆Cu包SiCp/Ni35覆层组织及磨损性能

目的研究Cu包SiC_p/Ni35激光熔覆层的显微组织、物相及其在25℃和600℃下的摩擦机理。方法采用化学镀的方法在SiC_p表面包覆一层Cu,并用激光熔覆的方法在H13钢表面制备了Cu包SiC_p增强Ni35熔覆层。用XRD、OM、SEM和EDS对熔覆层的物相、组织和成分进行了分析,用显微硬度计测试了熔覆层的显微硬度,用高温磨损试验机测试了熔覆层在常温、高温下的耐磨性能。结果熔覆层由基相γ-Ni(Fe)固溶体、增强相M7C3以及硼化物、硅化物和石墨构成。熔覆层的显微硬度和常温摩擦性能较H13钢显著提高,而其高温摩擦性能较H13钢基体提高较少。结论 SiC_p化学包覆Cu能减缓激光熔覆过程中SiC_p的分解,但分解速度还是过快。常温磨损时,高硬度碳化物和硅化物的覆层提高了材料的耐磨性能。高温下模具钢表面形成致密的氧化物薄膜,起到减磨降摩的作用,而高温下覆层无法形成致密氧化膜,导致其耐磨性能弱于常温。

Microstructure and Wear Properties of Cu-coated SiCp/Ni35 Coating by Laser Cladding

The work aims to study microstructures, phases and friction mechanism at 25 ℃ and 600 ℃ of C SiCp/Ni35 laser clad coating. The Cu-coated SiCpwas prepared in the method of electroless plating, and the Cu-coated SiCp-reinforced N35 clad coating was prepared on H13 steel by laser cladding. Phase, microstructure and composition of the clad coating were analyzed with XRD, OM, SEM and EDS. Microhardness of the clad coating was tested with microharness tester, and wear resistances at room temperature and high temperature were tested by high temperature wear tester. The clad coating was composed of matrix phase γ-Ni(Fe) solid solution, reinforced phase M7C3, borides, silicide and graphite. Micro-hardness and friction property at room temperature of the clad coating are significantly higher than those of H13 steel, while wear resistance of the coating at high temperature has only a little increase than that of H13 steel. Cu coated SiCp can slow down the decomposition of SiCp in laser cladding process, but the decomposition rate is too high. High hardness carbide and si-licide in the coating can improve wear resistance at room temperature. Dense oxide film forms on the surface of die steel at high temperature, which can reduce wear and friction; no dense oxide film forms on the clad coating at high temperature, which leads to lower wear resistance than that at room temperature.