In Additive manufacturing, the size and homogeneity of the melt pool are crucial to understanding some common defects in the product such as intra-layer porosities and balling defects. Here, we study the dynamic behavior of the melt pool during the Selective Laser Melting (SLM) process of CMSX-4 Nickel superalloy with the help of macroscopic CFD simulations. To include the effects of powder inhomogeneities and get a realistic distribution of powder layer on the bed-chamber, the CFD model is coupled to a DEM (Discrete Element Method) solver. The coupled model is implemented in the open source CFD software package OpenFOAM and the model is validated with experimental studies performed on powder bed under SLM conditions.

With the help of coupled model, we have investigated the effect of key process parameters such as laser power, the scanning speed of the laser, powders size, and powder shape on the size and homogeneity of the melt pool. From the simulation results, it has been discovered that a deep and narrow keyhole is created by high laser power and slow scanning speed which leads to creating porosity. The Balling defects are caused by a small melt pool that with fast scanning speed and low laser power is generated.