A Study On Laser Cladding Of Surface Structured CBN End Grinding Wheel

The conventional grinding wheel has a small bonding area between the abrasive grains and the bonding agent,so that the abrasive grains on the surface are easily peeled off during the grinding process.As a result,the conventional grinding wheel is prematurely in failure or thermal damage,and there are important defects such as greatly reducing the service life of the conventional grinding wheel and reducing the grinding performance of the grinding wheel.Moreover,the abrasive grains on the surface of the conventional grinding wheel are generally arranged randomly,and the ratio of the normal force to the tangential force is large in the grinding process,and the rigidity of the grinding machine is highly demanded.The conventional grinding wheel also has the difficulty of dressing the grinding wheel,which greatly reduces the chip space.In the end,when the workpiece is ground,the real-time temperature rises,and the processing efficiency and service life of the grinding wheel are lowered,which seriously affects the surface processing quality and processing efficiency of the part.In terms of manufacturing process,laser cladding technology can directly manufacture arbitrarily complex structures and nearly dense metal parts compared to conventional removal and forced deformation metal processing.And it not only saves material costs,but also shortens application and experimental cycles.In terms of materials,CBN and diamond have nearly the same hardness and thermal conductivity,while CBN has stronger chemical and thermal stability than diamond.In terms of the surface structure of the grinding wheel,the effective abrasive grain arrangement and its parameters are the most influential factors in the grinding wheel processing state.Therefore,this thesis studies the preparation of CBN surface structured end grinding wheel by laser cladding.The main research contents of the thesis include:(1)Reasonable laser processing parameters and material parameters were explored,CBN morphology in cladding layer was observed and failure modes were analyzed.The CBN abrasive particles previously placed on the alloy powder on CuSnTi are melted by laser onto AISI 1045 steel having various process parameters.The wettability and oxidizability of CBN abrasive particles were analyzed during laser cladding and the failure types of CBN in laser beads are observed.The results show that the Ti element in the CuSiTi substrate has very good activity on CBN and covers almost the entire surface of the CBN during laser processing.The Ti element has a stronger oxidation effect on the surface of CBN because Ti reacts with oxygen in the air,and there is no protection method to separate the workpiece from the air after laser processing.In laser processing,the failure of CBN can be divided into two categories:internal cracks in CBN due to high residual stress and partial or full gasification of CBN due to high temperature of laser beads.(2)The bonding form and holding force between CBN and substrate were tested to verify whether the grinding conditions were met and the laser processing parameters were optimized.Under different laser cladding process parameters,the morphology of CBN embedded in the laser cladding layer is observed.The elemental distribution along the cross-sectional interface of the substrate/alloy powder substrate/CBN abrasive particles is detected,and the morphology of CBN in the laser cladding layer after scratch test is analyzed.The reaction mechanism between CBN abrasive grains and CuSiTi alloy powder substrate is studied,and the laser cladding process parameters are optimized.A scratch test is conducted to test whether the CBN abrasive grains of the laser cladding layer prepared under the method can be used for the preparation of the grinding tool.The results show that the redistribution and segregation of Ti near the interface between the substrate and the substrate produces a Ti-Fe compound.And the laser cladding CBN on AISI 1045 meets the requirements of grinding under specific laser process parameters.(3)Analysising of the influence of abrasive group arrangement parameters,three types of surface structure are designed,which are blade sequence arrangement,discontinuous dislocation concentric arc arrangement and linear array arrangement.Through the software of Solidworks 3D modeling,CAXA 2D drawing and RobotArt trajectory programming,a CBN surface structured end grinding wheel is prepared by laser cladding method with four kinds of laser cladding including no surface structure.(4)Studying the advantages of structural grinding wheel in surface topography and grinding heat dissipation by comparative method,and optimizing grinding parameters.By observing the burns on the workpiece surface and the line roughness,it is concluded that the surface structure is helpful for grinding heat dissipation,and the heat dissipation effect is directly related to the structure form.and the optimal grinding parameters under this condition are given.And observe the surface topography of grinding wheel with large grinding depth to validate that the grinding holding force and grindability of grinding wheel.