Study On The Post-weld Heat Preservation Technology Of Hi-frequency Induction Brazing For PCD Cutting Tools

The brazing of PCD compact is a key procedure of making polycrystalline diamond cutting tools. Nowadays, the high-frequency induction brazing is one of the most popular techniques used in the brazing of PCD compact around the world, because of its notable advantages such as less pollution to the environment and higher production efficiency. Much research on the pre-treatment and brazing course of PCD compact with cemented carbide has been carried out in China. However, the brazing intensity of PCD tools with cemented carbide substrate in practice is still much lower than that of those brazed abroad, due to the poor brazing usability of PCD compacts. Therefore, it is necessary to investigate the post-weld heat preservation technology of hi-frequency induction brazing for PCD cutting tools, which is studied less by domestic researchers, in order to further enhance the performance of PCD cutting tools.Firstly, a temperature control system of holding furnace based on AT89S51 single chip microcomputer was designed to improve the old holing furnace in this paper according to the requirement of brazing holding technology for PCD cutting tools. Meanwhile, the structure and work principle of the temperature control system were presented. The hardware, the software and the strategies of temperature control were also mainly described.Secondly, PCD cutting tools were brazed in air atmosphere with two different brazing filler alloys, one soldering and one cemented carbide base, using high-frequency induction brazing machine GP15-CW6. And post-weld heat preservation experiments of high-frequency induction brazing were carried out right away by putting the PCD cutting tools into the improved holing furnace after brazing. Shearing experiments were undertaken using cutting tools obtained in the brazing experiment and the cutting tools' shearing strength was measured later. The results of shearing experiment indicated that the shearing strength of brazing joints increased with the increase of heat preservation temperature, but increased first and decreased afterward with the prolonging of heat preservation time. And the shearing strength of PCD cutting tools using the way of post-weld heat preservation was higher than that of those using plaster power cooling or air cooling.Finally, the cutting tools' joints were observed by means of scanning electron microscope (SEM) and the elements' distributions were investigated using electron probe microanalyzer (EPMA). It was found that the joint organizations of 1# brazing filler alloy became homogeneous and the elements' segregation decreased with the rise of heat preservation temperature. But the joint organizations and element distributions of 2# brazing filler alloy didn't have obvious changes. It was also found that there were many micropores and inclusion disfigurements in the joints when heat preservation time was longer. In addition, the rake faces of PCD cutting tools under different heat preservation time were also observed using SEM. It was revealed that in course of post-weld heat preservation, there was thermal damage happening on the PCD cutting tools. Further more, with the increase of post-weld heat preservation time, thermal damage became serious gradually.