Microstructure and properties of WC reinforced iron matrix composites manufactured by laser additive

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, wear machine and electrochemical workstation. The laser additive layer and matrix had good metallurgical bond. The phase composition of the laser 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 surface distance, cellular crystals appeared in the bottom layer. The grain size of sub-surface was the smallest and even and had the highest hardness of 1057HV, 4.2 times as much as that of 40Cr steel matrix. The middle layer had the lowest wear rate of 0.29 mg/mm2, the best wear resistance, the highest self-corrosion potential of −205.86 mV and the best corrosion resistance. The corrosion rate in the bottom layer was the slowest, and the passivation current was 0.1865 μA/cm2. The added tungsten carbide particles react with Fe-based powder to form Fe2C and Fe2W, forming the second phase reinforcement, which improves the wear resistance, corrosion resistance and hardness of the matrix. The sub-surface layer of the additive manufacturing layer has the highest hardness, while the middle layer has the best wear resistance and corrosion resistance. © 2020, Chongqing Wujiu Periodicals Press. All rights reserved.