40Cr刀具表面激光熔覆WC/Co50复合涂层的微观组织及其磨损性能

Microstructure and wear behavior of WC/Co50 composite coatings on 40Cr cutting tool surface prepared by laser cladding

通过6 k W横流CO2激光器在40Cr钢表面激光熔覆了不同成分配比的WC/Co50复合涂层。运用金相光学显微镜(OM),扫描电镜(SEM),能谱仪(EDS)和X射线衍射(XRD)等表征手段分析了涂层结合区形貌、显微组织和物相组成,测试了复合涂层的显微硬度和磨损性能。结果表明,外加的WC颗粒在高能激光束作用下大部分发生溶解,涂层主要由碳化物WC、W2C、(Cr,Fe)7C3和M6C及Fe-Cr固溶体等物相组成。涂层中组织结构比较复杂,出现了树枝状初晶、包状过共晶,枝晶间共晶和硬质相颗粒。WC/Co50熔覆涂层的最大显微硬度位于涂层次表面,其最大平均显微硬度为基材的1.93倍,且随着深度的增加逐渐降低。相同磨损条件下,复合涂层的磨损失重仅为基材的13.3%。

WC/Co50 cladding coating was fabricated on 40Cr cutting tool surface by 6 kW transverse- flows multimode CO2 laser apparatus. The surface morphology, phase composition, microstructure, microhardness and wear behavior of the cladding coating were analyzed by optical microscope （OM）, scanning electron microscope （SEM）, energy disperse spectroscopy （EDS）, X-ray Diffraction （XRD） hardness tester and friction wear testing machine. The results show that the original WC particles were dissolved greatly under the action of high-energy laser beam. The phase of coating is mainly composed of carbides WC, W2C,（Cr, Fe）TC3, M6C and Fe-Cr solid solution. The microstructure of WC/Co50 coating is complex, which consists of the primary dendrites, cellular eutectic, interdendritic eutectic and hard phase particles. The average hardness of the WC/Co50 coating is 1.93 times of the substrate, and the hardness of WC/Co50 cladding coating decreases with the increase of the surface depth. Under the same conditions, the wear weight loss of the composite coating is only 13.3% of the substrate.