Abstract
This study examines the solidification brittle temperature range (BTR) of CMSX-4 superalloy welds. Based on the BTR evaluation results, we quantitatively suggest the minimum BTR value for the solidification crack-free welding of the alloy. For the BTR evaluation, a transverse-Varestraint test correlated with real-time visualization of the molten pool temperature was applied. The BTR was evaluated to be 28 K for the 10A-linear condition, 109 K for the 20A-linear, and 336 K for the 30A-linear. With the application of oscillation, the BTR expanded to 434 K (0.6Hz-oscillated). The wide variation in BTR according to the welding conditions was investigated through the characteristics of the crystal growth behavior at the solidification cracking regions. For the 10A-linear condition with the narrowest BTR of 28 K, the entire weld metal, including the solidification cracking region, exhibited perfectly epitaxial growth identical to the base metal's crystal orientation. As the BTR expanded, controversially, the solidification cracking region showed polycrystalline behavior. Consequently, the BTR in the CMSX-4 superalloy welds can be reduced, and weldability can be improved by enhancing the degree of single crystallization during welding fabrication. This improvement is attributed to the reduction of dendrite coalescence undercooling.
Published Version
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