| With the rapid development of modern industry, the requirement of components' reliability and life is higher and the surface quality of workpiece is more important. As a kind of non-traditional finishing process technology on surface, magnetic abrasive finishing technology has characteristics of good processing flexibility and adaptivity. Magnetic abrasive finishing applies to processing plane, internal and external surface of tube,3D surface and so on. But the lack of preparation of magnetic abrasives restricts the large-scale application of magnetic abrasive finishing in industry.Over the past twenty years, electroless composite plating has developed rapidly and applied to prepare composite materials based on metal. By adding micro paticles with high hardness or wear-resisting to the electroless solution, particles and metal deposit on the surface of workpiece. The composite coating has high hardness and good wear resistance. Combined with the advantage of electroless composite plating, this paper proposed the process program of preparation of magnetic abrasives based on acidic electroless composite plating to solve the existing problems of preparation technology of magnetic abrasives. Main work includes the following aspects:(1) The deposition rate, hardness of coating and pH stability of solution were taken as indexes. Single factor experiments and orthogonal experiments were used to explore the influence of process parameters on the electroless plating solution performance. The optimal process parameters were as follows:30 g/L NiSO4·6H2O,30 g/L NaH2PO2·H2O,21 g/L C3H6O3,6 g/L GtHeOs,1.5 mg/L CN2H4S,7.5 g/L C4H6O4,18 g/L NaC2H9O5, pH 5.1, temperature 85 "C and loading ratio 1.0 dm2/L. Coatings prepared by the process formula were deposed under different temperatures and detected by the XRD. The research showed that as the temperature increased the coating structure changed from amorphous state to crystalline state and the optimal heat treatment temperature was 400? with the highest hardness 805.12 HV. The coating was not pulled off from metal matrix in the experiments of thermal shock and scratch, so the binding force between coating and metal matrix was fine.(2) Choosing steel balls 0.6 mm as ferromagnetic phase, choosing diamond content of coating as index, orthogonal experiments were adopted to explore the optimal process parameters with different sizes of diamond powder. Diamond powder deposited homogeneously on the entire surface of magnetic abrasives prepared by composite barrel plating, no phenomenon of reunion happened and abrasive particles were embedded firmly in the plating. The ball and needle magnetic abrasives with a variety of specifications were prepared to meet different processing requirements.(3) Experiments on the surface of 45 steel were conducted on the plane magnetic abrasive finishing testbed with spherical magnetic abrasives to explore the influence of processing time, spindle speed and machining gap to the surface roughness of workpiece. Based on reasonable process parameters, the influence of different sizes of the particle phase and the ferromagnetic phase on surface roughness and removal rate was investigated through experiments. The finishing performance of ball and needle magnetic abrasives was compared and the reason was analyzed.Experiments showed that magnetic abrasives prepared by acidic electroless composite plating hadhigher hardness and binding force and magnetic abrasive performance was excellent. The topic made beneficial exploration on the large-scale preparation of magnetic abrasives in industry. |
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