Effects of HAZ widths on creep crack growth properties of welded joints

Abstract

The finite element method (FEM) based on ductility exhaustion damage model was used to investigate the effects of heat-affected zone (HAZ) widths on creep crack growth (CCG) properties for the compact tension (CT) specimens with pre-crack located in the middle of softer and harder HAZs under the same initial load level. The results show for the welded joints with softer HAZ containing crack that the creep rupture life increases and CCG rate decreases with increasing HAZ width due to the decrease of material constraint effect. For the welded joints with harder HAZ containing crack, a second crack in soft material near interface generally forms, and the rupture life is mainly determined by the initiation time of the second crack. The CCG length in harder HAZ increases with increasing HAZ width. There exist proper widths of the harder HAZ which have the longest rupture life due to the lower stress triaxiality and later initiation of second crack in soft material near interface. The CCG properties of HAZs may be improved by adjusting HAZ widths and its creep properties by adopting proper welding methods or process. The HAZ widths and mismatches in creep properties should be fully considered in creep life assessments for the welded joints.