Suppression method of liquefaction crack in electron beam welding of dissimilar superalloy based on finite element analysis

To address the technical challenge of liquefaction cracking in the electronic beam welded joint of the Mar-M247/GH4169 superalloy, targeted finite element analysis and experimental validation were conducted. This study employed a combined approach of finite element simulation and experimental validation. Specifically, by analyzing prevailing crack formation mechanisms, the concept of sensitivity temperature range equivalent stress increment (S_STRESI) was proposed to evaluate the liquefaction crack sensitivity of electronic beam welded joints in dissimilar high-temperature alloys. The accuracy of S_STRESI was validated through comparative analysis with actual crack conditions. A finite element model was utilized to elucidate effective suppression strategies for liquefaction cracks, demonstrating that beam offset and preheating methods can significantly reduce cracking sensitivity in the heat-affected zone of high-temperature alloys. Research findings indicate that the S_STRESI peak occurs at approximately 428 MPa in the central region of the side heat-affected zone of Mar-M247, which also corresponds to the location of observed liquefaction cracks. Both beam offset and preheating effectively mitigate the S_STRESI peak to reduce liquefaction crack sensitivity. When the offset is 0.5 mm, the S_STRESI peak decreases to 400 MPa; at 1 mm, it drops to 355 MPa; and at 1.5 mm, the S_STRESI peak region disappears. Increasing the preheating temperature to 200 ℃ reduces the S_STRESI peak to 352 MPa, while exceeding 600 ℃ completely eliminates the S_STRESI peak range. When the beam is offset by 1.5 mm from the GH4169 side and preheated to 600 ℃, it effectively prevents liquefaction cracks from forming in the central region of the side heat-affected zone of Mar-M247. The beam offset reduces the thermal deformation difference between the two sides of the heat-affected zone, balancing the stress states on both sides of the welded joint. This lowers the S_STRESI (side stress) extremum of Mar-M247 and thus avoids the occurrence of liquefaction cracks.