Transcrystalline crack
A crack that runs directly through the crystallites and occurs in brittle microstructures under mechanical or thermal overload. Indicates low toughness.
Physical-Chemical Mechanism of Action
A transgranular crack is a crack that runs directly through the crystallites of a metal. This typically happens in brittle microstructures under mechanical or thermal overload. The toughness of the material is too low in this case to prevent the crack.
Metallurgical Relevance & Risks in Welding
A transgranular crack can occur in brittle microstructures like martensite or ferrite under mechanical or thermal overload. This leads to a strong loss of toughness and increases the susceptibility to hot cracks and cold cracks. Such a crack can also significantly shorten the service life of a component.
Workshop Practice & Action Guidelines
To avoid transgranular cracks, it is important to control the microstructure of the metal. For steels with high carbon content (e.g., martensite), the hardness should be reduced by tempering. The weld must be carefully cooled to achieve a homogeneous microstructure. Too rapid cooling can cause brittle microstructures and increase the susceptibility to transgranular cracks.