| 40Cr steel has good mechanical properties, low temperature impact toughness, low notch sensitivity, and good hardenability. It was widely used in the manufacturing field.40Cr is often used in the manufacture of cutting tools of tool holder and segment, but it is very serious wear and tear, low service life because of poor working conditions and big impact. Using laser cladding (LC) to deal with the surface of40Cr steel can improve its performance. In this experiment, we preset ceramic composite powder and alloy (WC, TiC and Co50alloy powder) on40Cr steel surface. Finally, we prepared the TiC-WC/Co50and WC/Co50metal ceramic composite coating by laser cladding. Analyze the surface effect of different composition and process parameters. The bonding characteristics, phase composition, microstructure morphology of the coatings were investigated by XRD, SEM and OM; using micro-hardness tester and high-temperature wear tester studied the micro-hardness distribution and the wear behaviors at different temperatures of the coatings. According to the results of previous work, we chose the optimal technology of laser cladding on the processed40Cr segment with the WC/Co50ceramic coatings, prepared40Cr carbide coated tools for tool rod, and also studied cutting property of40Cr carbide coated tools compared with high speed steel cutting experiment. The results as follows:(1) In preset layer of the WC and Co50alloy powder, When WC content is lower than92%(mass fraction), we can prepare better surface quality of the ceramic composite coating by adjusting the parameters of laser cladding. The coating turn out to be a good binding ability with40Cr base material, the combination is metallurgical combination without macroscopic crack.(2) The WC and Co50alloy powder decompose in the laser cladding process and coating is mainly composed of WC, W2C, M6C (mainly Co3W3C and Fe3W3C),(Cr, Fe)7C3and Fe-Cr phase composition and so on, the bigger laser power density, the greater the WC decomposition and generate the more W2C, M6C and brittle carbides.(3)SEM analysis showed that the cladding layer is mainly composed of dendritic crystal, interdendritic eutectic, isometric, columnar crystal and diffuse distribution of hard phase and carbide network (M6C type carbides), along the cladding layer depth direction, there is an obvious organizational change, present a rapid solidification tissue morphology.(4) After dealing with40Cr by laser cladding, the micro hardness and wear properties are improved, average micro hardness of WC/Co50coating by laser cladding is nearly2times than the40Cr base material. Micro hardness gradient distribution of cladding layer is reasonable, suitable for tools. The wear mass losses shown that the coating wear resistance have greatly improved than40Cr, and within a certain range,with the increase of the content of WC,wear-resisting performance enhancements.(5) Preparing WC/Co50coating on the surface of40Cr tool by laser cladding, The cutting experiments that compared with high speed steel cutter. The results shown that the laser cladding of40Cr tool reaches to the standard of high speed steel cutter, meet the requirements of cutting performance. The cutting performance is better than W6Mo5Cr4V2HSS cutting tools. |
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