There is a synergy between welding and additive manufacturing with reference to spatial and temporal variations of heat transfer. In this research, in-situ measurements of heat transfer conditions are considered as a viable qualification methodology for additive manufacturing (AM). Infrared imaging (IR) was performed within a laser powder bed fusion (L-PBF) AM machine equipped with an IR camera. Infrared thermal signatures as a function of space and time, while processing Ti6Al4V and 316L stainless steel powders, were extracted and analysed. The analyses correlated the defect evolution at low- and high-heat input conditions to thermal decay and integrated intensities. The IR based results were validated by processing a 316L cylinder with engineered porosities and detecting the same with ground truth data from computed tomography.