Intergranular cracking of Hastelloy C-276 in the socket welded assemblies

초록

The cause of thermal cracking about a socket welded tube was investigated by stress simulation and its comparison to hardness distribution of welding seam, HAZ and matrix of the tube. In the condition of heat-input in melting range of 1349 degrees C, the stress was concentrated in HAZ at the opposite side of welding area by ANSYS program, which corresponded to the distribution of real hardness values of the tube. The high stress concentration in HAZ might be induced from fine carbide precipitation which formed during welding process. It could cause, therefore, tube cracking in operating condition simultaneously followed by bulging inside of the welded tube. In the crack propagation through all the tube originated from inside HAZ, it might be accelerated by thermal fatigue, and propagated along grain boundaries accompanied by the metal dust formation.

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