The Research Of Microstructure And Machinability Of Cemented Carbide Cutting Tools Prepared By Laser Cladding

Cutting is one of the most important processing methods in machinery manufacturing industry. With the increase in the amount of metal removal and the complication and diversification of objects, the increased level of automation and improved efficiency of the machining put forward higher requirements for tools.Cemented carbide cutting tools have been prepared by multi laser cladding on 45 steel. We observed the macroscopic morphology and analysed the micro structure of the coating by OM and SEM, phase structure and its variation by XRD and EDS. We carried out a series of cutting experiments by combining ordinary machine bed with piezoelectric three-cutting dynamometer and optical microscopy. In the experiment we offered a comprehensive comparison with YG8 carbide cutting tools. The results showed that:We got a serious of blades with well macroscopic morphology and with no crackles. Coating and the substrate were metallurgically bonded, and multi-layer cladding process formed a dense coating eventually. Microstructure included dendrites, packaging hypereutectics, interdendritic eutectics and massive hard phase particles. Most microstructure of the upper coating was massive hard phase particles, decomposed carbide particles and a small amount of tissue dendrites. Microstructure in the middle coating was equiaxed crystals and interdendritic eutectics. The bottom of the coating was plane crystals, a large number of coarse columnar dendrites and interdendritic eutectics, and the microstructure was messy. WC particles exhibited a gradient distribution from the bottom to the top of coating. Volume and quantity of WC particles increased from the bottom to the top. Coating consisted of WC, W2C, Al2O3, Co3W3C, Fe3W3C, CoCr solid solution and so on. The formation of a large number of carbide phases and solid solution phases showed that WC particles were decomposed, and the formation of Al2O3 phase showed the high activity of A1 and O in the molten pool were binded preferentially and it formed a chemically stable ceramic phase Al2O3, which prevented the O and C to be combined, at last the generation of gas holes were suppressed. Main cutting force of YG8 tools was less than the laser cladding tools, and was more stable too. The projected BUE acted on the workpiece surface and formed a relatively rough surface under vibration eventually. Cutting force of the laser cladding tools was larger and more volatile due to the easier formation and instability of BUE, and the cutting force changed with BUE. Larger main cutting force of laser cladding tools formed larger cutting heat. Cutting process of YG8 carbide tools was more stable, which leaded to good chip formation. Chips of laser cladding cutting tools were oxidized in the larger thermal effect, and were easier to be broken. Laser manufactured tools could form smaller surface roughness values than YG8 carbide tools finally. The wear forms of YG8 tools were mainly abrasive wear and a part of diffusion wear. While the wear forms of laser cladding tools were abrasive wear/adhesive wear/diffusion wear and oxidative wear.