In part 3 we know that chipping/fracturing wear occurs to tungsten carbide cutter components when the service conditions are much tougher than carbide’s tolerance, especially when the cutting edges are unprotected, and so designs need consider to use protective edge chamfers and radii, avoiding sharp inside edges and other stress-inducing features. In this part we will talk about thermal cracking which is also one of the most common failure modes of tungsten carbide cutters.

4. Thermal Cracking

Cemented tungsten carbide cutters have relatively poor thermal shock resistance and sudden changes in temperature often produce failure by thermal cracking. Thermal cracks can result from thermal stresses developed in a single heating-cooling cycle if the temperature change is rapid and significant. These cracks often take the form of a network of fine cracks occurring throughout the bulk of the carbide component and normally result in catastrophic failure. Thermal cracks may also develop gradually over thousands of thermal cycles involving very small changes in temperature. The latter are more localized and typically occur as closely-spaced, radial cracks that extend from edges of the part. As the process progresses these cracks deepen and widen resulting in the spalling away of the carbide located between them.

(To be continued. This article is divided into 9 parts and this is part 4, for part 3 please refer tohttp://news.chinatungsten.com/en/tungsten-information/79331-ti-10139 ; for part 5 please refer tohttp://news.chinatungsten.com/en/tungsten-information/79348-ti-10146)

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