Experimental and numerical study of dissimilar laser welding characterisation of ASTM B637 and duplex 2205

This study presents a comprehensive investigation into the impact of dissimilar fibre laser welding parameters on the thermal and mechanical characteristics of ASTM B637 nickel-based alloy and duplex 2205 stainless steel in a circular geometry. A central composite design (CCD) approach was employed to systematically examine the effects of the key process parameters on the responses of melt pool geometry, temperature field near the melt pool, and joint tensile stress and strain. Numerical simulations were conducted to evaluate temperature distribution inside the fusion zone, molten pool geometry and the microstructural changes according to the temperature gradient induced by heating and solidification process. The results demonstrated that increasing laser power from 300 to 400 W led to a significant increase in the depth of the melt pool from 1 to 1.5 mm. Experimental measurements validated the numerical simulations, confirming their accuracy in predicting temperature gradients and molten pool behaviour. The temperature near the melt pool of both metals had experienced more than 200 °C temperature variation by increasing the laser power from 200 to 400 W. At high welding speed of 500 mm/min, a lower temperature level about 50 °C was observed for the duplex side because of having more heat sink effect. Microstructural analysis revealed a transition from columnar dendrites near the fusion boundary to a cellular structure toward the fusion zone centre, driven by variations in solidification intensity. Furthermore, tensile strength and elongation properties exhibited notable improvements with increased laser power. A rise of laser power from 250 to 450 W resulted in a tensile strength increase from 330 MPa to 570 MPa, while elongation improved from 3 % to 19 %. These findings emphasize the critical role of laser power and welding speed to improve weld quality and mechanical performance.