Non-destructive identification of weld-boundary and porosity formation during laser transmission welding by using optical coherence tomography

Laser transmission welding offers significant benefits over conventional welding techniques enabling single-stage rapid plastic joining. The quality of laser transmission welded products is commonly assessed by measuring the weld penetration depth, hardened weld boundary, and inspecting the formation of porosity. However, the existing methods of verification are inevitably accompanied by destruction of the specimen. Thus, non-destructive quality assessment methods for laser transmission welding have gained attention recently. Here, we demonstrated an extended industrial application of 860 nm wavelength-based spectral domain optical coherence tomography for the non-destructive inspection of the aforementioned quality parameters of laser transmission welded industrial plastic materials, i.e., polycarbonate and acrylonitrile butadiene styrene copolymer. The acquired cross-sectional resolution and volumetric and intensity profiles sufficiently contributed to the quality assessment procedure, revealing the weld boundary and porosity formation, and thus confirming the potential applicability of optical coherence tomography for the quality inspection of laser transmission welded products.