Liquation cracking

Although the emphasis in recent years has been on the role of low sulphur contents in promoting hydrogen cracking, it is also possible for a sulphur content which is relatively high to give liquation cracks in the HAZ and for these minute cracks or hot tears to act as potent nuclei for the nucleation of hydrogen cracks. Steels... 

Microfissuring. Similar to austenitic stainless steel, nickel alloys are susceptible to formation of liquation cracks in reheated weld metal regions or parent metal HAZ. This type of cracking is controlled by factors outside the control of the welder such as grain size or content impurity. Some alloys are more sensitive than others. For example, the extensively studied Inconel 718 is now less sensitive than some cast superalloys, which cannot be welded without inducing liquation cracks. 

The partial fusion of minute regions rich in impurity elements (particularly sulphur) in the HAZ close to the fusion boundary. When liquation leads to cracking, the cracks are very small, but they can initiate hydrogen cracking. 

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