What role does brazing welding play in the manufacture of PCD tools?

For the preparation of PCD cutting tools, the brazing/ welding of PCD composite sheet and cemented carbide or steel matrix is very important.

The brazing/ welding methods of PCD mainly include laser welding, vacuum diffusion welding, vacuum brazing, and high-frequency induction brazing. The brazing process of PCD composite sheet is one of the key technologies restricting the popularization and application of PCD cutting tools. As we all know, the brazing of hard alloys mostly adopts high-temperature brazing process (the brazing temperature is about 1000°C), while the PCD composite sheet must adopt low-temperature brazing process, otherwise it will cause thermal damage to the PCD composite sheet and affect its cutting performance. However, the joint strength of low temperature brazing is often relatively low, and it is easy to desolder during tool processing. At present, many domestic tool manufacturers are troubled by the thermal damage and desoldering problems of PCD tool welding.

Many researchers have also conducted in-depth research on this issue. Among them, in the study of high-frequency induction brazing technology for PCD composite sheets, it was found that when high-frequency induction brazing PCD composite sheets, the welding temperature has the greatest impact on the welding strength. Through the research on the thermal stability of the PCD composite sheet, the safe temperature of brazing is determined: when the PCD composite sheet is brazed in an air atmosphere, the safe brazing temperature of the CTB002 grade should be lower than 650°C; the CTBO 10 grade should be lower than 670°C, CTB025 grade should be lower than 720°C. In addition, when brazing PCD composite sheets, WC-based cemented carbide with higher cobalt content (ie, K-type cemented carbide) should be preferred, which is beneficial to improve the brazing strength.

At present, most manufacturers of PCD cutting tools at home and abroad choose high-frequency welding process. The most important technical parameters of the process include welding temperature, welding time, holding environment and holding time. The welding temperature will have a direct impact on the internal structure of the PCD cutting edge. If the welding temperature is too high, it will cause the PCD cutting edge to carbonize and affect its cutting performance; if the welding temperature is too low, it will cause weak welding and affect the joint strength.

The welding time refers to the time for maintaining the welding temperature. If the holding time is not enough, the flux will not be melted sufficiently and evenly, and the welding will not be strong. If the holding time is too long, the PCD cutting edge will affect its cutting performance due to prolonged exposure to high temperature. If the welded PCD tool is cooled in the air, the thermal stress between the PCD and the tool body will be too large, resulting in weak welding, and even cracks may appear on the PCD tool in severe cases. Therefore, it is best to quickly put the welded tool into a vacuum or inert gas medium with a certain temperature for a certain period of time to cool it slowly.

PCD/ PCBN Inserts Welding Operating Process

Step 1: welding Preparation

Welding powder, Silver / copper foil , pcd / pcbn blanks, cutter body .

Between the cutter body and pcd and pcbn blanks put into the Silver / copper foil and Silver/ copper powder .

*CBN Inserts With Copper Foil , 800~900℃

*PCD inserts with Silver foil , 750℃

Step 2 : high frequency induction brazing/ welding machine

Step 3 : welding

Opening the water and electricity of high-frequency welding machine . Then opening the panel. Putting the cutter body into the sensor, pressing the remote control switch, starting heating. When the workpiece is heated to 830-860 ℃, copper foil melting and filling weld. Finally, pressing the "Stop" button to stop heating.

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