Analysis of Manufacturing Technology for PCD Cutting Tools

Manufacturing process

The manufacturing process of PCD cutting tools mainly includes two stages:

Manufacture of PCD composite plates: PCD composite plates are made by sintering natural or artificially synthesized diamond powder and binder (including cobalt, nickel and other metals) at a high temperature (1000-2000℃) and high pressure (5-10 million atmospheres). In the sintering process, due to the addition of the binder, a bonding bridge consisting mainly of TiC, SiC, Fe, Co, Ni and other components is formed between the diamond crystals, and the diamond crystals are embedded in the skeleton of the bonding bridge in a covalent bond.

Usually, the composite plates are made into circular discs with fixed diameter and thickness, and the sintered composite plates need to be grinding, polishing, and subjected to other corresponding physical and chemical treatments.

Processing of PCD cutting tool blades: The processing of PCD cutting tool blades mainly includes cutting of composite plates, welding of blades, grinding of blade edges, etc.

Cutting technology of PCD cutting tools

Due to the high hardness and wear resistance of PCD composite plates, special processing technology must be adopted. At present, several processing methods are mainly used in processing PCD composite plates, including electrical discharge wire cutting, laser processing, ultrasonic processing, high-pressure water jet, etc.

Among the processing methods, electrical discharge machining has the best effect. The bonding bridges in PCD make it possible to machine composite plates by electrical discharge. Under the condition of working fluid, the pulse voltage is used to form a discharge channel of working fluid near the electrode metal, and a discharge spark is generated locally, so that the polycrystalline diamond can be melted and fall off, thus forming the required triangular, rectangular or square tool head blank.

The efficiency and surface quality of electrical discharge machining of PCD composite plates are affected by cutting speed, PCD particle size, layer thickness, electrode quality, etc. Among them, the reasonable selection of cutting speed is very important. Experiments have shown that increasing cutting speed will reduce processing surface quality, while too low cutting speed will produce "bowing", and reduce cutting efficiency. Increasing the thickness of PCD cutting tool blades will also reduce cutting speed.

Welding technology of PCD cutting tools

In addition to mechanical clamping and adhesive methods, PCD composite plates are mostly pressed on hard alloy substrates by brazing. The welding methods mainly include laser welding, vacuum diffusion welding, vacuum brazing, high frequency induction brazing, etc.

At present, high-frequency induction heating brazing with less investment and low cost is widely used in the welding of PCD cutting tool blades. In the process of blade welding, the selection of welding temperature, welding flux and welding alloy will directly affect the performance of the post-welding tool.

In the welding process, the control of welding temperature is very important. If the welding temperature is too low, the welding strength is not enough; if the welding temperature is too high, the PCD is easy to graphitize, which may cause "over-burning" and affect the bonding of PCD composite plates and hard alloy substrates. In the actual processing process, the welding temperature can be controlled according to the insulation time and the depth of redness of PCD (generally below 700℃).

Automatic welding technology is mostly used in foreign high-frequency welding, with high efficiency and good quality, and can achieve continuous production; in China, manual welding is mostly used, with lower production efficiency and less ideal quality.

Grinding technology of PCD cutting tools

The high hardness of PCD makes its material removal rate extremely low. At present, the grinding technology of PCD cutting tools mainly uses diamond sand wheels with ceramic binders for grinding.

Because the grinding between the grinding wheel abrasive and PCD is the interaction between two materials with similar hardness, the grinding law is relatively complicated. For high-grit, low-speed grinding wheels, the use of water-soluble cooling fluid can improve the grinding efficiency and precision of PCD. The selection of grinding wheel binder should be based on the type of grinder and processing conditions.

As the electrical discharge grinding (EDG) technology is hardly affected by the hardness of the workpiece to be ground, the use of EDG technology to grind PCD has significant advantages. Grinding of some complex-shaped PCD cutting tools also has a huge demand for such flexible grinding technology.

With the continuous development of electrical discharge grinding technology, EDG technology will become a major development direction of PCD grinding.