Microstructural aspects of the causes of type IV cracking in Cr-Mo steel weld joints

摘要

Fusion welded joints of Cr-Mo steels fail prematurely under creep condition at the heat affected zone (HAZ) close to the base metal, termed as type IV cracking. Optical metallography and hardness testing across the joint establish that the type IV cracking occurs in the soft intercritical HAZ. Based on detailed microstructural studies carried out to understand the evolution of the microstructure and its role in determining the tendency for type IV cracking, the factors that lead to deterioration of creep strength in intercritical HAZ in weld joint of Cr-Mo steels are: a) fine grained structure