| The vitrified bond diamond grinding tools are widely used in the field of high-precision grinding,but their development in the field of grinding is limited due to their high brittleness,poor thermal conductivity and shape-preserving property.Composite bond is a trend of the development of grinding wheels.The introduction of metal phase into the vitrified bond can effectively improve the performance of the vitrified bond grinding tools,and the suitable composite effect of metal phase and ceramic phase becomes a key to the ceramic-metal bond grinding tools with excellent properties.In this paper,The Ni-P film was uniformly introduced into the vitrified bond by electroless plating,so as to solve the problem of poor toughness.Through the discussion of the deposition speed,the plating time and the weight gain rate,the bath composition and the plating conditions of ceramic-metal bond powder with different Ni-P content were made sure.The performance,microstructure and phase composition of the sinered samples were characterized by various Instrument and equipment,and this paper explored the influence of sintering process parameters,Ni-P content and particle size composition of the bond on the ceramic-metal bond and its grinding tool.The results showed that:?1?The effects of plating conditions and bath composition on the deposition rate,the plating time and the weight gain rate of electroless plating were investigated.The results showed that increasing the p H,the bath load,the temperature of plating solution and the concentration of main salt could improve the deposition speed and shorten the plating time.The pH,the temperature of plating solution and the concentration of sodium citrate had a little relation with the weight gain rate.In addition,the weight gain rate decreased linearly with increasing the bath load.It was a better way to prepare composite bond powder with the different content of Ni-P by controlling the bath load.?2?The optimum plating conditions and bath composition were as follows:the concentration of main salt?NiSO4·6H2O?was 30g/L,the concentration of reducing agent?NaH2PO2·H2O?was 25g/L,the concentration of complexing agent?C6H5Na3O7·2H2O?was10g/L,the concentration of complexing agent?CH3COONa·2H2O?was 10g/L,the bath temperature was 55?,pH was 5.2.Under these conditions,the phosphorus content of the coating was 9.83wt%,the XRD patterns of the composite bond powders showed non-crystalline structure.?3?The results showed that the phase composition of hot pressed sintered samples were Ni and Ni3P,while those of sintered samples in the muffle furnace were Ni and cristobalite,and the Ni3P was integrated into the vitrified bond system.?4?The optimum hot pressing parameters of ceramic-metal bond were as follows:sintering temperature at 670?,holding time for 3min and hot pressing pressure at 19.6MPa.In this process,with Ni-P content of ceramic-metal bond increasing from 0wt%to 23wt%,the microstructure of the samples changed from the microstructure of the samples changed from the island structure of ceramic phases melted through together to the reticular structure of ceramic phases independed.When the Ni-P content of sample was 20wt%,the metal phase and ceramics phases interlaced and inserted each other,and the ceramic-metal bond had better mechanical properties.The results showed that the bending strength and impact strength were155.22MPa and 3.15KJ/m2 respectively,which were 73%and 1.67 times higher than the vitrified bond?the bending strength 89.7MPa,the impact strength 1.18KJ/m2?respectively.?5?The optimum sintering temperature of the grinding tools was 690?.At this sintering temperature,the grinding tool with 20wt%Ni-P content had the optimum performance.Its metal phase was fused with ceramic phase,and the Ni in the composite bond increased the adhesion work between bond and diamond.Its bending strength and impact strength of were86.15MPa and 5.71KJ/m2 respectively,which were 2.67 and 2.86 times higher than the vitrified bond grinding tool?the bending strength 23.48MPa,the impact strength 1.48KJ/m2?respectively.As the size of ceramic-metal bond became finer,the pores on the grain boundary of the grinding tools became less,and their bending strength and impact strength increased.But they were lower than the mechanical strength of the grinding tool with mixed size of ceramic-metal bond. |
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