Melt pool-level multi-output monitoring using an off-the-shelf color camera during multi-layer wire arc additive manufacturing of Alloy 718

Abstract

In this work, two-color thermography using a commercial color camera is applied to directly measure spatially and temporally resolved melt pool temperatures during deposition of Alloy 718 walls via cold metal transfer gas metal arc welding-based additive manufacturing. These measurements are used to extract layer-wise melt pool width and length as well as thermal gradient and cooling rate. Thin walls were fabricated using a wire feed speed 84.67 mm/s, travel speeds of 3.8 and 7.2 mm/s, and interlayer dwell times of 30, 180, and 300 s. The results demonstrate that two-color thermography can directly resolve and quantify layer-wise variations in melt pool geometry and solidification conditions. Shorter dwell time promoted progressive heat accumulation with build height, resulting in increased melt pool dimensions and reduced cooling rates and thermal gradients. In contrast, longer dwell time produced more consistent melt pool dimensions, indicating stabilized solidification conditions. The ability to extract these critical melt pool-level outputs using a single off-the-shelf color camera provides a scalable pathway for in situ monitoring and multi-input multi-output feedback control in wire arc additive manufacturing.