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Laser-engineered net shaping (LENS) is a rapid direct manufacturing process. The LENS process can be analyzed as a sequence of discrete events, given that it is a layer-by-layer process. The thermal history associated with the LENS process involves numerous reheating cycles. In this article, the thermal behavior during laser deposition with LENS is simulated numerically by using the alternate-direction explicit (ADE) finite difference method (FDM). The simulation results showed that deposited material experiences a significant rapid quenching effect during the initial stages of deposition and can attain a very high cooling rate. With an increase in deposit thickness, the rapid quenching effect decreases and eventually disappears. The effects of the processing parameters on the thermal behavior of deposited materials were also simulated and analyzed. The objective of this study is to provide insight into the thermal history during the LENS process, where the ability to correlate process parameters to microstructural evolution is a motivating force.

The thermal behavior during laser-engineered net shaping (LENS) processing was numerically simulated using the alternate direction explicit finite difference method in Part I of this work. In this article, Part II, the numerical simulation results were compared to experimental results obtained with LENS-deposited 316L stainless steel. In particular, the cooling rate that is present during LENS deposition was established on the basis of dendrite arm spacing (DAS) measurements with and without a melt pool sensor (MPS) and a Z-height control (ZHC) subsystem. The microstructure of the deposited materials was characterized and analyzed, and the corresponding microhardness was measured as a function of distance from the substrate. The influence of thermal history on microstructure evolution was analyzed and discussed based on both modeling and experimental results. The results discussed in this article suggest relatively good agreement between experiments and modeling.

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