Study On Preparation And Performance Of Low Temperature Brazing Paste For Diamond Cutting Tools

Diamond cutting tools possess high hardness and wear resistance. After grinding, roughness of the diamond cutting tools is small. Simultaneously, diamond has low friction coefficient, high thermal conduction efficiency. The comprehensive performance makes diamond very suitable for precision machining, being an ideal material to make the cutting tools. Welding of the diamond blade with cutter body is a key step for the diamond cutting tool manufacture. Too high welding temperature will cause structural damage of the diamond cutters. Therefore, preparation of low temperature brazing paste is of great importance for the manufacturing of the diamond cutting tools. Based on diamond brazing characteristics and requirements, we developed a low-temperature brazing paste, maintaining good brazing performance while brazing temperatures is low. The paste is easy to use and cost-effective. The main contents are as follows:Based on the characteristics of diamond brazing, we developed a new type of adhesive for diamond cutting tool brazing paste. The main components of the adhesive are polybutene, hydrogenated castor oil, fatty alcohol ethoxylates(AEO-9), and oleic acid. We added hydrogenated castor oil a thickner to improve the viscosity of polybutene and the thixotropic property of the adhesive. The fatty alcohol ethoxylates(AEO-9) acts as a dispersing agent to improve the dispersion of the particles in the adhesive and oleic acid acts as a lubricant to improve the flow properties of the adhesive. The adhesive is prepared in oil bath at 110℃ by incubation for 30 min with mechanical stirring. This thesis also analyzed the binding mechanism of each component by viscometer.The thermal characteristics of the brazing paste were analyzed by thermal analysis techniques. Through brazing paste wetting experiments, we calculated brazing wetting angle and the spreading area to analyze the effect of the content and particle size of Ti powders on the brazing filler metal wetting properties. Finally, we get an ideal brazing paste suitable for diamond brazing. The results showed that the wetting and flow performance of the brazing filler metal is good, at the content and particle size of active element Ti of 4% and 40 ~ 150 μm in the brazing filler.Using the above prepared brazing paste effects of brazing process parameters on the bond strength of the diamond with the cutter body were investigated by a high frequency induction equipment. We used shearing experiment, scanning electron microscope(SEM), and energy dispereive X-ray spectroscopy(EDS) to investigate the brazing performance and diamond surface morpholo-gy. The welding process parameters were optimized. Appropriate temperature and holding time will reduce the generation of brazing internal defects and promote the growth of Ti C. Suitable heating rate can reduce thermal damage to the diamond and prevent heat stress caused by uneven heating. The experimental results show that at the heating current of 500 A, brazing time of 10 s, temperature of 900℃, and weld thickness of 100~120 μm the brazing strength is the highest.