Optimization of bead spacing during laser cladding of ZE41A-T5 magnesium alloy castings

A 4 kW Nd:YAG laser system was employed to clad 6.2-mm ZE41A-T5 aerospace magnesium alloy castings at various bead spacings using 1.5-mm filler. An operating window between the bead spacing and the elevated defocusing distance was determined based on theoretical analyses and experimental investigation. Based on the profile characteristics of single beads, this window can be used to determine the optimum bead spacing and the elevated defocusing distance for single layer cladding, and the layer distance for multi-layer cladding. It was found that, at low bead spacing and low elevated defocusing distance, surface overlaps or protrusions may occur. To avoid these defects, one method is to clad using optimized bead spacing. Another method is to elevate the defocusing distance together with the filler in order to melt the wire before it touches the previous bead surface. The results indicated that by using the elevated defocusing distance, it was possible to significantly expand the operating window.