Microstructure and stress corrosion cracking of the fusion boundary region in an alloy 182-A533B low alloy steel dissimilar weld joint

Effects of aging temperature on microstructural evolution at dissimilar metal weld interfaces

“…B than in Alloy 152, as expected. In addition, in the weld metal region near the FB region, the welding process may cause the elemental gradient to become a dilution zone, which can be further distinguished into two regions, possibly originated from buttering layers during the welding process; this was also observed in earlier work [4,6,16]. Following the aging heat treatment, the elemental distribution became relatively uniform, and Cr was concentrated in the weld metal near the FB.…”

“…B near the FB. The precipitates were defined as Cr 23 C 6 based upon their TEM diffraction patterns [4,6,18]. In addition, the TEM diffraction patterns also show that the structure is mainly body-centered cubic in the LAS side and face-centered cubic in the Alloy 152 side.…”

“…Incidents of stress corrosion cracking (SCC) of Alloy 182 in pressurized water reactors have been reported in recent years, and the initiation and growth of SCC have been acknowledged in the Alloy 82/182 weld metals with dissimilar metal weldments (DMW) [1][2][3][4][5][6][7][8]. The corrosion resistance of welds composed of filler metal may be inferior to that of a properly annealed base metal owing to microsegregation, precipitation, the formation of unmixed zones, etc.…”

“…Because of dilution effects in the dilution zone and in the fusion boundary (FB) region near the A533 Gr. B LAS, the reduced Cr and Ni contents can increase corrosion and SCC susceptibility for the bulk weld metal [6,[11][12][13][14]. Additionally, the formation of residual stress in the FB region due to microstructural heterogeneity and thermal mismatch can result in a gradient of mechanical properties across the FB [15].…”

Microstructures and microhardness at fusion boundary of 316 stainless steel/Inconel 182 dissimilar welding

“…The inhomogeneity of chemical compositions and microstructures through the fusion boundary of a dissimilar metal welded joint can cause its complex crack growth behavior. Hou et al [12,13] indicated that Type-II grain boundaries, parallel to the fusion boundary, were more susceptible to SCC because of its high-angle characterization. Lu et al [14.15] showed that the fraction of coincidence site lattice (CSL) boundaries was increased with increase of distance from the fusion boundary to the weld heat affect zone (HAZ).…”