Insights into the microstructure evolution and crystallographic texture of API X-65 steel/UNS S32750 stainless steel dissimilar welds by EBSD analysis

In this study, the microstructural features and microtexture evolution of API X-65 steel welded to UNS S32750 stainless steel were evaluated. The weldments were produced with the different heat input (HI) values: 0.68 and 0.78 kJ/mm. The samples were then characterized by means of the electron backscatter diffraction analysis. The obtained results showed that the microtexture components formed in the UNS S32750 heat-affected zones (HAZs) and the UNS S32750 base metal were the same. However, the microtexture of the API X-65 HAZs was significantly affected by the HI values in comparison to that of the API X-65 parent metal. A random orientation of grains and also a non-uniform distribution of both austenite and ferrite phases were observed in the weld zones. It was revealed that with decreasing the HI value, the austenite's fractions decreased; hence, almost equal fractions of austenite and ferrite phases were formed in the weldment employing the HI value of 0.68 kJ/mm. It was inferred that the kernel average misorientation and fractions of the especial boundaries were not influenced by the changes in the HI values. Moreover, it was observed that the weld metals showed slightly better impact resistance in comparison to the base metals.

Automated summary

In this study, the microstructural features and microtexture evolution of API X-65 steel welded to UNS S32750 stainless steel were evaluated with different heat input (HI) values. It was found that decreasing the HI value led to a decrease in the fractions of austenite, resulting in almost equal fractions of austenite and ferrite phases in the weldment using the HI value of 0.68 kJ/mm. The impact resistance of the weld metals was slightly better compared to the base metals.