Advances in the understanding of the annular laser beam wire cladding process

This paper experimentally studies the influence of conventional process parameters (laser beam power, P, workpiece, and wire feeding velocities), and the nominal workpiece irradiation proportion WIPN parameter, on ALB-WC process stability and generated clad geometry. The study was based on an extensive set of single clad experiments using stainless steel AISI 316L wire of 0.6 mm diameter and a stainless steel AISI 304 workpiece. The results show that the laser beam power required for a stable process increases non-linearly with WIPN, and this relationship can be described by quadratic regression. An increase in either the workpiece or wire feeding velocity respectively causes a reduction or enlargement of the stability region in the P-WIPN stability diagrams. The influences on stability diagrams are explained by means of the increase in the nominal WIPN to the effective WIPE, as a result of the clad height generated. With respect to clad geometry, it was shown that an increase in the WIPN causes a decrease in the dilution ratio, which is linearly correlated with the workpiece and melt pool temperatures, while clad width and height are not influenced by the WIPN. The paper further explains the complex influences of the process parameters observed on process stability and generated clad geometry using a phenomenological description of the ALB-WC process at a low and high nominal WIPN. For this purpose, heat transfer, Marangoni flow, and laser beam reflections are considered qualitatively and supported by IR and visual images of the wire-end and melt pool as well as the workpiece and melt pool temperatures.