Study On Nano-ceramics Harden Layer Of The Autogenous Grinding Blade By Laser Cladding

This paper presents nano-SiC powder and the mixed powder with micron-metal powder coating in the 45 steel substrate surface using the 500W all solid-state (Nd:YAG) CW lasers, and applies it to the shredder blades. Firstly, through the comparative analysis about the microstructures and micro-hardness of nano-SiC coatings under different laser cladding process parameters, finds out appropriate cladding process parameters. Secondly, comparates the microstructures and micro-hardness of the mixture coatings of the different percentage of nano-SiC powder with micron-Fe, Co, Ni and Cr powder, uses the friction and wear tester to test the friction-wear performance of the coatings, and uses the SEM to see the coatings’compositions, then select the hardened layer. Finally, the hardened layers are applied to the self-sharpening blades. Tests the abrasive wear performance of the blades in the homemade abrasive wear tester. And manufactures blades that could be used in the foliage grinder.It discusses the influencing factors of the weld width of the single-channel coating, such as scanning speed, laser power, the distance between the part surface and the level of laser. Apart from the main three laser parameters, the factors also contain the coatings’materials, the coatings’ thickness and so on. In fact, the three main laser parameters reflect the size of the laser power density in the laser cladding process. The slower the scanning speed is; the bigger the laser power is; the nearer the distance between the part surface and the level of laser focus is, the more higher the laser power density will be. If the laser power density is too low, the coating wll not be melt; the bond strength between the part and the coating will be low. If the laser power density is too high, the microstructures will be big; the heat-affected of the substrate will be high. There are some micro-cracks in the single-channel nano-SiC coating.It finds that the scanning speed, the laser power, the distance between the part surface and the level of laser focus all have some influence on the micro-hardness, the microstructures and the patterns of the coatings in the laser cladding process of multi-channel nano-SiC coating. The coatings have little micro cracks. For the patterns of the coatings, if the over lap rate is too big, it will be messy. If the scanning speed is too slow, the coating will easily have tumors. The final laser parameters for the multi-channel coating:the scanning speed is 3mm/s, the laser power is 305 W, the distance between the part surface and the level of laser focus is 20mm, the laser track clearance is 0.4mm。Add some metal power to increase the toughness in the process of preparation of the hardened layer. It has observed the microstructures and micro-hardness of the mixture coatings of the different percentage of nano-SiC powder with micron-Fe, Co, Ni and Cr powder under the same laser parameters. The micro-hardness of the mixture coatings will be lower with the following the more percentage of the metal powers. The join of Co powder will decrease the hardness more quickly. On the contrary, Ni and Cr powder will decrease the hardness more slowly. Therefore, select two or three kinds materials from Fe, Ni and Cr powders to increase the toughness of the hardened layer.Through testing the part of the hardened layers in the friction and wear tester, to make the theoretical basises for their practical application, and to analyze the hardened layers’friction-wear performance. On the same conditions of wear and tear, the coefficients of friction of the hardened layers are lower than the existing blades, the mass-losses of the hardened layers are also smaller. On the basis of certain process, manufacture the grinder blades with the hardened layers. Test and analysis of the grinder blades’ abrasive wear performance of prepared homemade abrasive wear testing machine. The results show that the amount of wear-masses of the blades are gradually increasing with the wear time. On the initial stages, the amount of wear-masses of the blades increases. On the certain stage, the amount of wear-masses of the blades increases slowly. After a certain time, the amount of wear-masses of the blades increases quickly. This process has some relations with the using environment of the blades.