激光增材制造WC增强铁基复合材料组织结构及性能研究

Microstructure and Properties of WC Reinforced Iron Matrix Composites Manufactured by Laser Additive

目的采用激光增材制造技术制备WC增强铁基复合材料,并对其显微组织结构及性能进行表征测试,为后续制备大体积激光增材做技术理论及工艺储备。方法加入质量分数为10%的WC粉末,利用激光增材制造技术在40Cr钢表面制备WC增强铁基复合材料层,采用X射线衍射仪(XRD)、金相显微镜(OM)、扫描电子显微镜(SEM)、硬度计、磨粒磨损机、电化学工作站等,分析激光增材层逐层组织结构、力学性能及其变化规律。结果激光增材层与基体呈良好冶金结合,相组成为α-(Fe,Cr)、Fe2C、Fe2W、Fe3B。表层、亚表层及中层区显微组织为鱼骨状树枝晶,在其周围存在硬质颗粒,随着表面距离的增加,底层区出现胞状晶。亚表层区晶粒最为细小均匀,硬度最高,为1057HV,是基体的4.2倍。中层区磨损率最低(0.29 mg/mm^2),耐磨性最好,自腐蚀电位最高(-205.86 mV),耐蚀性能最好。底层区钝化电流密度最小,为0.1865μA/cm^2,腐蚀速度最慢。结论加入的WC颗粒与铁基粉反应生成的Fe2C与Fe2W形成第二相强化,提高了基体的硬度、耐磨性及耐蚀性,且增材层亚表层区硬度最高,中层区耐磨性、耐蚀性最好。

The work aims to prepare WC reinforced iron matrix composite by laser additive manufacturing technology,and characterize and test its microstructure and properties to provide technical theory and technology reserve for subsequent preparation of large volume laser additive.Tungsten carbide powder with a mass fraction of 10%was added to prepare tungsten carbide-reinforced iron matrix composite layer on the surface of 40Cr steel by laser additive manufacturing.The microstructure,mechanical properties and variation rules of laser additive manufacturing layers were analyzed by X-ray diffraction(XRD),metallographic microscope (OM), scanning electron microscope (SEM), hardness tester, abrasive wear machine andelectrochemical workstation. The laser additive layer and matrix had good metallurgical bond. The phase composition of thelaser additive manufacturing layer included α-(Fe,Cr), Fe2C, Fe2W and Fe3B. The microstructures of the surface layer,sub-surface and middle layer were fish-like dendrites, and there were hard particles around them. With the increase of surfacedistance, cellular crystals appeared in the bottom layer. The grain size of sub-surface was the smallest and even and had thehighest hardness of 1057HV, 4.2 times as much as that of 40Cr steel matrix. The middle layer had the lowest wear rate of0.29 mg/mm2, the best wear resistance, the highest self-corrosion potential of ?205.86 mV and the best corrosion resistance. Thecorrosion rate in the bottom layer was the slowest, and the passivation current was 0.1865 μA/cm2. The added tungsten carbideparticles react with Fe-based powder to form Fe2C and Fe2W, forming the second phase reinforcement, which improves the wearresistance, corrosion resistance and hardness of the matrix. The sub-surface layer of the additive manufacturing layer has thehighest hardness, while the middle layer has the best wear resistance and corrosion resistance.