The Investigation Of Diamond Powder Surface Plating And Application

After coating a layer of metal on the surface of diamond powder,the bonding ability between diamond particles and binder in grinding wheel can be enhanced,thus the wear resistance of diamond grinding wheel can be improved.In this paper,a layer of nickel was coated on the surface of diamond powder by electroless plating.The effects of the plating bath composition and plating conditions on the results of electroless plating of diamond powder were investigated.Electroplating with copper sheet instead of diamond,and the coating morphologies,cathode weight gain,surface roughness,deposition potential,corrosion potential and corrosion current density were characterized.The effect of the concentration of nickel chloride,boric acid and sodium dodecyl sulfate(SDS)on bath performance and coating quality was studied.The grinding wheel was made of diamond particles of different proportions.The wear resistance,hardness and smoothness of diamond grinding wheel were tested and analyzed by electronic balance,Vickers hardness tester and inductance micrometer.The effects of diamond granularity proportion on the wear resistance of diamond grinding wheel were investigated.After studying the problems of diamond powder surface plating and application,the main conclusions are as follows:1.By investigating the influence of plating bath composition and process conditions on the results of electroless plating of diamond powder,the following conclusions are obtained.(1)The order of influence of complexant on weight gain of electroless plating was citric acid > ammonia > sodium citrate,and weight gain will be reduced without adding sodium citrate.The weight gain rate of electroless plating is related to the nickel grain size deposited on the surface of diamond powder,and the coated diamond powder with less leakage and less continuous crystals can be obtained when pH value is about 4.The optimal proportion of complexant is citric acid 25 g/L,sodium citrate 12.5 g/L and ammonia water 17.5 mL/L.(2)Nickel slag will be formed without adding stabilizer,and excessive addition of stabilizer will inhibit the reaction,while the reaction will proceed normally if the amount of dispersant is increased.(3)With the increase of diamond addition amount,the weight gain rate decreases,and the best coating has been achieved when diamond addition amount is 6 g.(4)With the increase of temperature,the rate of weight gain increases,and 80~85 ? is the optimum range.2.By investigating the influence of bath composition on bath performance and coating quality under natural convection,the following conclusions are obtained.(1)Boric acid has the greatest effect on the cathode weight gain,so do the nickel chloride on the surface roughness,deposition potential,corrosion potential and corrosion current density.(2)The coating pitting appeared due to the combined effect of SDS and boric acid,and the condition is that the concentration of SDS and boric acid is low in the electroplating bath.(3)The cathode weight gain from the first use of plating solution is less than that of the reused.The concentration of nickel chloride in the bath is not balanced,which results in the corrosion resistance of the coatings in different positions is inconsistent,and the corrosion resistance in the middle of the coating is better than that at the edge.3.By investigating the influence of diamond granularity proportion on the wear resistance of grinding wheel,the following conclusions are obtained.(1)With the increase of diamond particle size,the wear resistance of diamond grinding wheel is improved;and the wear resistance of diamond wheel made of coated diamond is better than that of diamond wheel made of uncoated diamond.(2)Based on 120/140 size diamond,no matter whether the doped abrasive is uncoated diamond or coated diamond,the corresponding ratio can be found,which makes the wear resistance better than that of single 120/140 abrasive.