Intercrystalline crack
A crack that runs between the crystals of a metal along the grain boundaries. It is promoted by high growth of low-melting phases or embrittlement and occurs under high thermal stresses.
Physical-Chemical Mechanism of Action
An intercrystalline crack is a separation fracture that runs along the boundaries between different crystals (grain boundaries) of a metal. These grain boundaries can be promoted by high growth of low-melting phases or embrittlement that accumulate there.
Metallurgical Relevance & Welding Risks
Intercrystalline cracks mainly occur under high thermal stresses and can lead to hot cracking. They grow especially near embrittled phases or grain boundary segregations, which impairs the toughness and strength of the material.
Workshop Practice & Instructions
To avoid intercrystalline cracks, it is important to ensure controlled cooling of the weld. This can be achieved by using cooling water or special cooling gases. The cooling rate should be set so that the structure does not cool too quickly (t8/5 < 5 s) and no glass-hard martensitic phases form. At high stresses, using stabilized steels or reducing the carbon content can also help.