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Models of varying complexity are available for understanding the role of composition on the solidification behavior of engineering alloys. The choice of an appropriate model is dictated by the solidification behavior of the alloy. In some situations, seemingly complex alloys can be represented accurately using simple binary models when only one eutectic reaction occurs during solidification. In contrast,...
The ductility-dip cracking (DDC) behavior of Ni-Cr-Fe alloys has been evaluated by the use of in situ scanning electron microscopy (SEM) involving high temperature deformation. This unique approach provides information regarding the DDC phenomenon and its dependence on microstructural features such as grain boundaries and second phase precipitates. Experimental materials were prepared based on the...
A modification of the original Cast Pin Tear Test (CPTT) developed by Hull in the 1970s is being used to quantify weld solidification cracking in Ni-base alloys, including both precipitation-strengthened “superalloys” and solid-solution strengthened alloys. This test uses a copper hearth and mold system to produce cast pins of different length. By changing the cast pin length, the thermal strain during...
Operating experience in the nuclear power industry has shown that dissimilar metal welds joined with Inconel 82/182 (ERNiCr-3/ENiCrFe-3) filler metal in the primary loop of pressurized water reactor (PWR) plants are susceptible to primary water stress corrosion cracking (PWSCC). Repair of these dissimilar metal weld joints by weld overlay (WOL) using the PWSCC resistant 52 M (ERNiCrFe-7A) filler metal...
This paper summarizes published methodologies of mitigating weld cracking by altering thermal strain and stress distributions during welding with thermomechanical methods. Thermomechanical conditions for weld cracking during fusion welding are discussed at first and then four thermomechanical methods are introduced which include (a) trailing cooling, (b) side rolling, (c) controlling heat input, and...
Presented here are results and discussion for weldability testing on Alloy C-22 weld-metal. The Transvarestraint test was used to determine the solidification cracking susceptibility of the alloy; results indicate that Alloy C-22 is resistant to solidification cracking. The STF test demonstrated that Alloy C-22 weld metal is susceptible to ductility-dip-cracking (DDC); no recovery of cracking resistance...
A new welding consumable, based on the Ni-Cu metallurgical system, was developed to reduce hexavalent Cr (Cr6+) emissions during welding of austenitic stainless steels. However, dissimilar metal welds between Ni-Cu alloys and stainless steels have not been thoroughly evaluated for susceptibility to elevated temperature cracking during welding. This study was performed to determine susceptibility of...
Electron beam welding of forged Allvac 718Plus superalloy has been carried out without any visible cracks in weld cross-sections. Healed cracks in the heat affected zone were, however, seen in most cross-sections with the healing as well as the cracking believed to be due to the constitutional liquation of the δ-phase. The δ-phase undergoes constitutional liquation in the Heat Affected Zone (HAZ)...
The stray grain formation behavior and susceptibility to solidification cracking in autogenous welds on single crystal alloy CMSX-4 have been investigated. Welds were prepared using the electron beam (EB) and gas tungsten arc welding (GTAW) processes. The stray grain area fraction and cracking susceptibility were determined and correlated to the processing parameters and process type. The stray grain...
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