Study On Preparation And Brazing Diamond Film Of Active Coated Brazing Filler Metal

Diamond film has excellent combination properties, so it has great application foreground especially in machining. But there are many problems in the process of making brazing diamond film tools. In order to solve the problems of complexities and shaping difficulties in preparation of brazing filler metal, we exploit a new one with fewer processes in shaping and well brazing results. We called it active coated brazing filler metal.Using technology of magnetron sputtering in vacuum, we prepared the active coated brazing filler metal: Ti was sputtered onto the Ag-Cu alloy foil under proper sputtering voltage, sputtering current and sputtering time. Through annealing, the binding force between the coated film and the base foil was strengthened. And we acquired the brazing filler metals used in the test of brazing diamond film and cemented carbides. Using this brazing filler metal, firm binding of CVD diamond thick film and cemented carbides formed by vacuum brazing under the condition that brazing temperature at 850℃, pressure below 5×10-2Pa and keeping 10 minutes. By the SEM photograph, we found that the active element Ti evenly distributed on the surface of the brazing filler metal. And in the joint, a continuous TiC film was generated by Ti reacted with carbon on the surface of diamond film. The TiC film and mechanical anchoring was the bridge linking diamond film and the brazing filler metal.Because of great difference among the expansion coefficient of diamond film, cements carbides and the brazing filler metal, high residual stress would generated in the brazing joint. The cooling velocity has great influence on the residual stress. Using of Finite Element Method, numerical simulation of residual stress generated with different cool velocity during the cooling process was done. We obtain the rules of the variation of residual stress and the distribution of stress field.