Numerical modelling on the plastic flow and interfacial self-cleaning in linear friction welding of superalloys

Abstract

The self-cleaning effect of linear friction welding (LFW) is believed to be a crucial means to remove surface contaminants for achieving a satisfactory property of the resultant joints. To systematically investigate the self-cleaning process, a fully-coupled computational model was established based on an integrated approach considering dual plastic bodies for simulating the LFW of a typical Ni-based superalloy, GH4169. Since the removal of surface contaminants is determined by the material flow during LFW, the plastic flow behaviour was studied followed by the introduction of contaminant removal process and parameter optimisation. Results showed the material flow rate was at the highest level when two components were at the maximum relative displacement. The forging load continuously extruding the softened materials from the interface gave the greatest contribution to the material flow and formation of the flash. The removal rate of contaminants was initially increased followed by a subsequent decrease after reaching the peak during the welding process. The removal of 95 % surface contaminants was found to be a criterion to determine the critical welding parameter in simulation. The critical shortening length for removing the contaminants was decreased with increasing friction pressure, but an opposite trend was observed with the oscillation frequency. Validation by experiments suggested that the model provided reasonable and accurate predictions for flash formation, material flow, and final joint property in LFW of GH4169 superalloy. The present developed model could be utilised to select welding parameters of the LFWed Ni-based superalloy joint with a significant simplification to the manufacturing process.