Heat accumulation in laser Additive Manufacturing processes and its effect on local solidification

Abstract

Laser based additive manufacturing creates parts layer-by-layer and offers increased design freedom in comparison to traditional manufacturing. However, the repeated application of energy frequently revisits previous deposited layers, which leads to heat accumulation and may result in microstructural inhomogeneity and anisotropic mechanical properties. Here we present a theoretical model which is applied to capture the heat evolution and accumulation during laser direct energy deposition and laser powder bed fusion processes. Infrared imaging from literature is used to validate the model. The model captures the effect of the consecutive deposition of the individual layers and shows its influence on heat accumulation. It demonstrates that heat accumulation leads to noticeable change in local solidification rate and temperature gradient, which results in significant variation in local grain structure. The predictions of the model allows for the development of process optimization strategies for the control of local microstructure evolution.