In situ multi-elemental analysis by laser induced breakdown spectroscopy in additive manufacturing

Abstract

The feasibility of in situ quantitative multi-elemental analysis during the additive manufacturing process has been demonstrated for the first time using laser induced breakdown spectroscopy (LIBS). The coaxial laser cladding technique was utilized for the production of highly wear-resistant coatings (nickel alloy reinforced with tungsten carbide grains). High-quality production as well as gradient composition coating synthesis required an online technique for quantitative elemental analysis. A low-weight, compact LIBS probe was designed to equip the laser cladding head installed at an industrial robot. Hot solidified clad as well as a melt pool surface was sampled by the LIBS probe but meaningful analytical results were achieved only for the latter case due to non-uniform distribution of tungsten carbide grains in the upper surface layer. LIBS sampling inside the melt pool did not affect the clad properties according to optical microscopy and scanning electron microscopy measurements. On-line LIBS quantitative analysis of key components (carbon and tungsten) was demonstrated during the synthesis of highly wear-resistant coatings and obtained results were in good agreement with offline analysis performed by electron energy dispersive X-ray spectroscopy, X-ray fluorescence spectroscopy, and the combustion infrared absorption method. In situ quantitative multielemental analysis by LIBS is a perspective control or/and feedback tool to improve quality of compositionally graded materials in additive manufacturing.