Experimental investigation and parametric analysis of laser-based fusion bonding of polyamide 6 to AISI 1018 low-carbon steel

This study investigates laser-assisted metal–plastic (LAMP) joining of polyamide 6 (PA6) to AISI 1018 low-carbon steel using a 1 kW fibre laser system. The individual and interaction effects of four key process parameters, laser power, scanning speed, defocus distance, and number of scans, on joint quality are examined using a central composite design of the response surface method. An empirical model is developed to correlate lap-shear strength with these parameters and validated through analysis of variance and additional experiments, confirming predictive reliability. Careful control of process conditions ensures balanced heat input and laser interaction time, enabling enhanced interfacial adhesion while limiting polymer degradation and thereby improving joint performance. A maximum lap-shear strength of 45.86 N mm −1 for the AISI 1018/PA6 joint, about 66 % of the tensile strength of 2 mm-thick PA6, is achieved using 900 W laser power, 35 mm s −1 scanning speed, 40 mm defocus distance, and two scan passes. Post-shear analysis reveals PA6 residues and elongated fibrils on the steel surface, confirming strong interfacial adhesion and load transfer. Failure modes exhibit both adhesive and cohesive characteristics, influenced by process parameters. These findings confirm LAMP joining as a reliable method for fabricating durable AISI 1018/PA6 hybrids with adequate joint strength.