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

通过6 kW 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W6C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%。

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

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)7C3, W6C 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.