Comparative study of helium bubbles, microstructure, and mechanical properties in the white bright band of SA508-3/52(M) dissimilar metal weld joints

After metallographic etching, unetched white bright bands (WBB) are evident in the SA508-3/52(M) dissimilar metal weld joints. The WBBs in both joint without a buttering layer (JWOBL) and joint with a buttering layer (JWBL) are composed of austenite, with no presence of martensite. A pronounced elemental gradient is present within the WBB. The width of the WBB in JWOBL exceeds that in JWBL. Owing to differences in the welding thermal cycling process, precipitates are present in the WBB of JWOBL, whereas JWBL lacks such precipitates. These precipitates hinder dislocation movement and assist in the nucleation and growth of helium bubbles. Consequently, the nanoindentation hardness and helium bubble number density of the WBB in JWOBL are significantly higher than those in JWBL. Irradiation damage, including helium bubbles, induces irradiation hardening of the joints. At elevated irradiation temperatures, however, the extent of irradiation hardening diminishes.