Improving the interfacial bonding strength of dissimilar PA66 plastic and 304 stainless steel by oscillating laser beam

Abstract Achieving high interfacial bonding strength between plastics and metals is one of the key challenges of structural lightweight. Oscillating laser beam was employed to improving the strength in this paper. Based on orthogonal test and variance analysis, the effects of oscillating radius, frequency and defocus distance on morphological characteristics, interfacial microstructure and mechanical properties of lap welds were discussed. It was found that the weld interface at the PA66 side could be divided into three zones, which were completely melted zone (CMZ), partially melted zone (PMZ) and soften zone (SZ). The binding force dominated by C O Cr chemical bond was the main force of interfacial joining. The PMZ was the most cohesive zone because its relative content of C O Cr chemical bond was twice higher than that of CMZ. Its area ratio to the whole weld interface dominated the shearing strength, and was in direct proportion to it. The results showed that increasing the oscillating frequency was beneficial to increase the area ratio of PMZ, and it had most significant effect on the shearing strength, whose contribution percentage was 63.07%. The shearing strength increased from 2.9 MPa to 7.75 MPa when the area ratio of the PMZ increased from 35.9% to 52%.