Cutting Parameters and Failure Mechanism of Polycrystalline Diamond Cutters

1. Brief introduction of polycrystalline diamond cutters

Polycrystalline diamond cutters have low friction coefficient, excellent thermal conductivity and low expansion coefficient. Its hardness is 2 to 4 times that of cemented carbide, and the tool life is more than 10 times that of cemented carbide.

2. Cutting parameters and failure mechanism of polycrystalline diamond cutters

(1) Cutting speed

Polycrystalline diamond cutters can be processed at higher speeds, and cutting speed is an important factor affecting the quality of processing. Although under the premise of high-speed cutting, the machining efficiency of the tool can be improved. However, due to the high hardness and brittleness of polycrystalline diamond cutters, under high-speed rotation, the increase of cutting temperature and cutting force, the instantaneous collision of the tool and the cutting sample will cause the tool tip to be brittle, so the polycrystalline diamond cutter needs re-sharpening. Therefore, when processing different workpiece materials, the cutting speed of polycrystalline diamond cutters should also be different.

(2) Feed rate

The feed rate of the polycrystalline diamond cutter directly affects its processing quality of the workpiece and the service life. If the feed rate of the polycrystalline diamond tool is too large, the geometric area of the polycrystalline diamond cutter in contact with the sample will increase exponentially, resulting in increased surface roughness; if the feed rate is too small, the processing efficiency will decrease. Therefore, for different equipment and processing materials, it is an important factor to improve processing quality and processing efficiency to find the right feed rate through continuous trials.

3. Cutting depth

In addition, the cutting depth also has a great influence on the service life of the cutter. If the cutting force of a polycrystalline diamond cutter increases, the cutting heat increases, which accelerates tool wear and affects tool life. In addition, the increase in cutting depth tends to cause the cutting edge of polycrystalline diamond cutters to break. Therefore, when using different polycrystalline diamond cutters with different grain sizes and processing different workpieces under different processing conditions, the cutting performance is different. Therefore, the actual cutting parameters of polycrystalline diamond cutters should be determined through a large number of experiments and processing conditions.

4. Failure mechanism

The failure modes of traditional tools are abrasive wear, bonding wear (cold welding wear), diffusion wear, oxidation wear and thermoelectric wear. The wear forms of polycrystalline diamond cutters mainly include polycrystalline layer damage, bonding wear and diffusion wear. When polycrystalline diamond cutters are used to process metal matrix composite materials, the failure mode is mainly bonding wear and failure caused by intercrystalline cracks in diamond grains; when processing materials with high hardness and high brittleness, the bonding wear of polycrystalline diamond cutters is not obvious; when processing materials with low brittleness, tool wear increases, and bonding wear plays a leading role.