Suppression method of liquefaction cracks in electron beam welding of dissimilar superalloys based on finite element analysis

To address the technical challenge of liquefaction cracks easily formed in the electron beam welding joints of the Mar-M247/GH4169 dissimilar superalloys, targeted finite element analysis and experimental validation were conducted. An approach of combining finite element simulation with experimental validation was employed. By analyzing current prevailing crack formation mechanisms, the concept of equivalent stress increment (S_STRESI) for the sensitivity temperature range was proposed to evaluate the liquefaction crack sensitivity in the electron beam welding joints of dissimilar superalloys. 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 crack sensitivity in the heat-affected zone of the superalloy. Research findings indicate that the S_STRESI extremum occurs in the central region of the heat-affected zone of the Mar-M247 side at approximately 428 MPa, which also corresponds to the location of observed liquefaction cracks. Beam offset and preheating effectively decrease the S_STRESI extremum to reduce liquefaction crack sensitivity. As the offset is 0.5 mm, the S_STRESI extremum decreases to 400 MPa; at 1.0 mm, it drops to 355 MPa; at 1.5 mm, the S_STRESI extremum region disappears. Increasing the preheating temperature to 200 ℃ reduces the S_STRESI extremum to 352 MPa, while with the preheating temperature exceeding 600 ℃, the S_STRESI extremum range disappears. When the beam is offset by 1.5 mm from the GH4169 side with the temperature preheated to 600 ℃, the liquefaction cracks are effectively prevented from forming in the central region of the heat-affected zone of the Mar-M247 side. 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 extremum of the Mar-M247 side and thus avoids the formation of liquefaction cracks.