Coating Ni-P Alloy On Micro Diamond Particles And Its Machining Performance Evaluation

Fixed abrasive lapping technology because of its environmental protection, low processing cost and high processing efficiency has been a new technology of lapping process and has developed rapidly in recent years. The diamond particles are commonly used for fixed abrasive lapping. However the diamond particles are easy to fall off in the process of lapping, the utilization efficiency of diamond is greatly reduced. Nickel plated on diamond grits surface can improve the ability of resin matrix to hold grains, and then improve the utilization ratio of diamond abrasives.Ni-P layer was prepared on diamond particles by electro-less plating in this paper. Fixed abrasive pads(FAP) were prepared which embedded with nickel plated diamond particles. Diamond morphology and processing properties were evaluated through continuous lapping experiments and related test systems. The main work and results are as follows:(1) The effect of complexing agent and reducing agent for electroless Ni-P alloy on phosphorus content and covering ratio were studied. The morphology of coating was observed by SEM. The results show that under the same conditions, the P content of coating increases with the increase of complexing ability and reducing agent content. The covering ratio of coating decreases with the the increase of complexing ability of complexing agent. The covering ratio of coating increases with the increase of reducing agent content. The surface roughness of nickel plated diamond increase with the increase of P content.(2) The processing characteristics of diamond particles with different P content in the fixed abrasive pads were performed. The effects of P content on the coefficient of friction(COF), acoustic emission(AE), material removal rate(MRR), the quality of the workpiece surface and wear resistance of FAP during the lapping process were compared and compared with electro-plated diamonds. The results demonstrate that the COF, MRR, roughness of lapped work-piece increase first, then decrease with the increase of P content. The machining efficiency and stability of middle-phosphorus diamond lapping pad are best. After sustainable process for 50 minutes,the material removal rate is 6.4μm/min, retention rate is 58.8%, which is about 1.2 times of low-phosphorus diamond. The wearing quantity of pads decrease with the increase of P content after lapping. The surface roughness and machining performance of electro-plated diamond all lie between low-phosphorus and high-phosphorus ones.(3) Diamonds in different lapping phases have different forces and contact state during lapping process. Nickel coating contents of two kinds of different size diamonds were optimized respectively and compared each other. The results demonstrate that the force and the holding strength between the resin matrix and gains of coarse lapping diamond are all higher than fine lapping diamond in lapping process. The requirement for surface roughness of coarse lapping diamond coating is also higher than fine lapping diamond. During the process of lapping K9 glass, the machining efficiency of 40-50μm diamond and 20-30μm diamond reach maximum when Ni-P covering ratio are 50% and 30% respectively.