Study On Preparation Of Magnetic Abrasives Based On Alkaline Electroless Composite Plating

With the development of industry, the precision components with fine surface quality are widely applied in high precision product applications, national defense and other important areas, precision and special processing of the components is becoming a hot issue in manufacture industry. Magnetic abrasive finishing (MAF) has many outstanding features, such as the flexible processability, the excellent surface quality, the low-cost equipment investment, which has unique advantages in manufacturing complex surface and internal surface of cavity. But as one of the core factors in magnetic abrasive finishing, the preparation method of magnetic abrasives can not up to aim, which impedes the industrial application of magnetic abrasive processing.Electroless composite plating is such method that water-insoluble particles are added to chemical plating, aiming to manufacture composite coatings with good performance. To deal with the existing problems of magnetic abrasives preparation, Preparation of magnetic abrasives based on alkaline electroless composite plating is proposed. The main contents are as follows:The deposition rate of electroless plating and hardness of coatings are taken as indexes, the bath formulation are optimized by using the orthogonal experiment and single factor experiments, the optimal bath formulation forms by following contents:30 g/L NiSO4,25 g/L NaH2PO2·H2O,65 g/L C6H5Na3O72H2O,25 g/L assistant complexing agent,2 mg/L H2NCSNH2,30 g/L accelerator, and at the condition of pH=10, temperature of 70"C. Coating by using this solution has excellent hardness, which can strengthen binding force between coating and base metal; levels of the element phosphorus in coating is 4.172%, it can be classified to the low phosphorus coating. Coating metal experiences changes from amorphous state to crystalline state after 400℃ heat treatment, N13P texture is produced, hardness of coating further improves. Scratch hardness test on coating suggests that there is a fine adhesion between coating and base metal.Choosing synthetic diamond as particle phase, choosing bar-iron wire as ferromagnetic phase, choosing Ni-P coating as bonding agent, magnetic abrasives are manufactured by barrel plating. According to the characteristics of electroless composite plating, strip abrasives are chosen to replace spherical abrasives; distribution uniformity of diamond particles on coating is chosen as leading indicator, the effect of different element on the distribution uniformity of diamond particles on coating are studied by single factor experiment. The optimum parameters are obtained as follows:barrel rotating speed 7°/s, concentration of diamond grains 0.4 g/L, time interval of rotating of the barrel 5min, stirring speed of solution 300 r/min, diamond grains distributed evenly on the surface of the base metal, which can insure the performance of magnetic abrasives.Internal surface of stainless steel pipe are ground using newly made magnetic abrasives on the numerical control lathe, grinding efficiency and working life are tested, and explore the effect of spindle rotation speed, processing time, pole feed speed on the surface roughness.