Numerical simulation and experimental investigation of laser overlap welding of Ti6Al4V and 42CrMo

Finite element method (FEM) and processing experiments were utilized to investigate the thermal phenomena and microstructure of laser overlap welding of Ti6Al4V and 42CrMo. A FEM model of temperature field was established, under considerations of thermal contact resistance and forced convection effect of shielding gas flow. Based on the model, temperature field with various laser power values and scanning velocities was calculated to explore the relationship between the process parameters and the interface temperature. Experiments were conducted on a 1 kW Nd:YAG laser materials processing system with five-axis CNC working station. Microstructure, chemical composition and microhardness of the joint were evaluated. From the numerical simulation and experimental investigation, the calculated temperature history at measuring points had the similar tendency to the experimental results. The interface temperature could just reach or be a little higher than the melting point of the lower sheet material 42CrMo by adjusting the process parameters according to the numerical calculation. At the interface, intermetallic compounds TiFe and TiFe2 were detected. The thickness of intermetallic reaction layer containing intermetallic compounds was found to depend on the heat input.