Deposition Pattern Based Thermal Stresses in Single-Layer Laser Aided Direct Material Deposition Process

Despite enormous progress in laser aided direct metal/material deposition (LADMD) process many issues concerning the adverse effects of process parameters on the stability of a variety of properties and the integrity of microstructure have been reported. Comprehensive understanding of the transport phenomena and heat transfer analysis is essential to predict the thermally induced stresses in the deposited materials. A complete model that provides a quantitative relationship between process parameters, temperature history, phase transformation kinetics, and the thermal stresses is highly desirable. This paper examines the effect of deposition patterns and phase transformation kinetics on induced thermal stresses. The proposed model is based on the metallo-thermo-mechanical theory for sequentially coupled temperature, phase transformation, and stress/strain fields. Finite element analysis of various deposition processes illustrates the significant effect of deposition patterns on induced thermal stresses. Raster scan, spiral in-to-out, and spiral out-to-in patterns, in conjunction with their experimental verification, have been discussed in this paper. The existing model can easily accommodate any deposition pattern a user may want to study with slight modifications. The effect of substrate preheating on thermal stress is also studied and some reductions in thermal residual stress were observed. The importance of considering phase transformation effects is also verified through the comparison of the magnitudes of residual stresses with and without the inclusion of phase transformation kinetics. The simulation has been carried out for H13 tool steel deposited on a mild steel substrate.