How to avoid cracks in cemented carbide?

The thermal conductivity of cemented carbide is relatively small. For example, the thermal conductivity of tungsten drill type cemented carbide is 58.62~87.92W/(m•K), and the thermal conductivity of tungsten-cobalt-titanium alloy is generally 16.75~62.8W/(m• K). In order to avoid cracks, it is impossible to choose a processing rule with a large pulse width. For example, a transistor pulse power supply was used to process cemented carbide, and a pulse width of 800 μs and a peak current of 1.5 A were selected. As a result, serious network cracks were generated on the processed surface.

Therefore, in rough machining, relatively small pulse width (for example, less than 100 μs) and higher peak current are used, so that the heat-affected layer of the so-called EDM is thinner. Even if there is a crack, its depth is relatively shallow. Then during finishing, the same small pulse width and higher peak current can be selected to almost completely remove the shallow cracks produced by rough machining. Such selection rules can not only avoid cracks, but also have better surface roughness.

Cracks have a great influence on the service life of cold forging dies, so the cold forging dies after finishing EDM must be polished to remove all the heat-affected layers produced by EDM, otherwise the die may crack during use.