PCD cutters are one of the classifications of diamond tools and are widely used in metal cutting. The PCD cutter itself has good performance indicators, so the heat transfer of the PCD cutter is rapid, the cutting force can be significantly reduced, the thermal deformation is small, the machining accuracy is high, and the chips are not easy to stick to the tip of the tool to form a mechanical tumor during the machining process.
Nevertheless, as a tool, PCD cutters are still subject to wear, which can be divided into:
There are often some tiny particles with extremely high hardness in the processed material, which can draw grooves on the surface of the tool, which is abrasive wear. Abrasive wear exists on all surfaces, especially on the rake face. Moreover, abrasive wear will occur at various cutting speeds, but for low-speed cutting, due to the low cutting temperature, the wear caused by other reasons is not obvious, so abrasive wear is the main reason.
When cutting, there is a lot of pressure and strong friction between the workpiece, the cutting and the front and rear cutter faces, so cold welding will occur. Due to the relative movement between the friction pairs, the cold welding will produce cracks and be taken away by one side, resulting in cold welding wear. Cold welding wear is generally severe at moderate cutting speeds.
Experiments have shown that brittle metals are more resistant to cold welding than plastic metals; multidirectional metals are smaller than unidirectional metals; metal compounds are less prone to cold welding than simple substances; B group elements and iron in the periodic table of chemical elements have a smaller tendency to cold welding. Cold welding is more serious when high-speed steel and cemented carbide are cut at low speed.
During cutting at high temperature and contact between the workpiece and the PCD cutter, the chemical elements on both sides diffuse each other in the solid state, changing the composition structure of the tool, making the surface of the tool fragile, and aggravating the wear of the tool. Diffusion phenomenon always maintains the continuous diffusion of objects with high depth gradient to objects with low depth gradient.
When the temperature rises, the surface of the tool is oxidized to produce softer oxides that are rubbed by chips, which is called oxidative wear. For example: at 700°C~800°C, oxygen in the air reacts with cobalt, carbide, titanium carbide, etc. in cemented carbide to form soft oxides; at 1000°C, PCBN reacts chemically with water vapor.
In short, not only PCD cutters but also other tools, the causes of wear include abrasive wear, cold welding wear, diffusion wear and oxidative wear. These four points are the main causes of tool wear. We also hope that the above understanding can help everyone better understand PCD cutters.
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