The Preparation And Property Research On New P/M Metal Based Diamond Composite Sawing And Grinding

P/M metal-based diamond composite tools possess self-sharpening, near-net-forming, and of much higher production efficiency, have been widely used to saw and grind hard-brittle materials such as stone, ceramic, semiconductor. What’s more, recent advances in the field of aerospace, electron, communication and so on raise a higher claim to the refining of tools. To reduce the preparation costs of metal based diamonds tools and ensure the excellent machine, interface and friction peoperties, the design of matrix component, optimizing of sintering process, interfacial thermodynamics and dynamics, friction and wear of segments were studied. Then the unified of microstructure, composition, properties and process will be reached. To reduce the thickness and improve the machining precision, the trail-produce, microstructure, mechnical properties and interface of diamond ultra thin sawing were also performed.A response surfaces model, whose12vertices and any two centroids are used for the experimental points, has been successfully established by the mixture experiment and extreme vertices design method (EVD). It can be concluded that the mixture experiment and EVD can be usded to calculate the matrix performance because the multiple correlation coefficient solved by regression analysis using Excel. The regression equations, whose calculation errors are2.8、3.4、2.9%compared with experimental value, can reliablely predict the matrix performance. The optimal contents of each component are:Fe60-66wt.%, Cu20-30wt.%and66-68wt.%, Co0-1wt.%, Sn0-0.8wt.%and7-8wt.%;According to the optimal matrix component and extreme difference analysis of orthogonal test results for Cu/Fe based diamond composite segments, it can be drawn the conclusion that the process parameters effects on density, hardness, bending strength and elastic modulus of segments are different. The optimal parameter ranges of Cu/Fe based diamond segments are sintering temperature700-740℃, pressure17-21MPa, dwelling time2-4min;Thermodynamics analyses show that the Gibbs free energy change of Cr7C3, Cr3C2and Cr23C6by reactions between Cr and diamond/graphite, and diamond graphitization are both negative at specific experimental conditions, indicating that the Cr3C2, Cr7C3and Cr23C6carbides reactions and diamond graphitization can automatically proceed in the experimental condition. According to the experimental verification, it can be seen that the surface of diamond sintered exist adhesive/spalling layers and the diamond graphitization not occurs and the metallurgy interfaces between matrix and diamond are formed, which are cinsistent with the throry;According to friction analysis results of diamond segments in there kinds of process, the relationship between sintering temperature, pressure, mechanical and friction properties is much closed. The Cu based diamond segments, whose matrix wear modes are adhensive and abrasive and whose diamonds are abrasive wear modes, are more wear-resisting with increasing sintering temperature or pressure. The wear modes of diamond in Fe based diamong segments are serious abrasive wear, mild abrasive wear and thermal erosion wear. The wear matching and friction properties of Fe based diamond segments are the best in the condition of740℃/13MPa/6min;The axial and radial microstructures of green are anisotropy because of much smaller aspect ratio during cold uniaxial compaction (CUC). With increasing pressure, the green densification is affected by non uniform deformation and changing inter-powder force. The deformation time is different at different loading rate, the green prosity is higher because of more deformation at low pressure when the loading rate is lower and the spring back occurs at higher loading rate. The densification is improved with longer dwelling time. The fracture morphologies, containing dimples, cleavages and brittleness along with iron rich particles, are dependent on the lattice types and interfacial bonding of matrix phases which are affected by the microstructure of green samples. The optimal cold compaction process of Cu based matrixes are pressurel87Mpa, loading rate0.1mm/min, dwelling time2min and Fe168Mpa,0.15mm/min,4min;The Cr and Fe are enrichment in the interface of Cu/Fe based diamong ultra thin sawing during cold compaction sintering respectively and the interface bonding of Fe based is better than Cu based. According to2D hydrostatic equation of diamond, stress values of diamond in hot pressed Cu/Fe based diamong ultra thin sawing are-645,-387MPa which are much lower than thermal stress because of stress release by carbide, plastic deformation and phase transition during cooling.