Rupture behavior and fracture mode for Inconel 625-9% Cr steel dissimilar welded joints at high temperature

In the present study, the rupture behavior and fracture mode for the Inconel 625-9% Cr steel dissimilar welded joints are investigated. The results reveal that the relationship between the rupture time and stresses follows the formula: lg (t) = - 0.028 sigma + 6.75, while the microhardness measurement shows that the specimens with applied stresses under 620 degrees C both fracture in the heat affected zone of 9% Cr steel (9Cr-HAZ). Therefore, the microstructure of the 9Cr-HAZ adjacent to the fracture is emphatically observed, and it is found that the tempered martensite is the typical microstructure in 9Cr-HAZ. Simultaneously, massive micro-voids can be detected in 9Cr-HAZ along the grain boundaries. In addition, the particles around the micro-voids are identified as Laves phases combining with M23C6-type carbides. Thus by consuming the solid solution strengthening elements, especially W and Cr, the precipitation of these second phase particles softens the matrix, which can cause the formation of micro-voids. Subsequently, the initiation and convergence of those dispersed voids eventually lead to the failure of the ruptured specimens.

Automated summary

The study found a specific relationship between rupture time and stress in the Inconel 625-9% Cr steel dissimilar welded joints, with the presence of a significant number of microvoids in 9Cr-HAZ contributing to the fracture.