J. W. Newkirk, Z. Fan, F. Liou, Missouri University of Science & Technology, Rolla, MO; H. N. Chou, K. Slattery, Boeing Phantom Works, St. Louis, MO; M. E. Kinsella, AFRL/RXLMP, Wright-Patterson AFB, OH
Direct laser deposition is a solid freeform fabrication process that has the capability of direct fabrication of metal parts. The part is fabricated in a layer-by-layer manner in a shape that is dictated by the CAD solid model. A primary objective of laser deposition is to achieve porosity free deposited layers with good metallurgical bonding and minimal dilution. Of the common defects in laser deposition, lack-of-fusion (LOF) is the most damaging since it may act as a crack under certain loading conditions. This work presents prediction of LOF using a comprehensive heat transfer/fluid dynamics coupled model. This model is used to simulate the coupled, interactive transport phenomena between laser, powder, and the substrate during the laser deposition process. The simulation involves laser material interaction, free surface evolution, droplet formation, transfer and impingement onto the substrate, and melt-pool dynamics. Transient temperature and velocity distributions of the falling particles and melt pool as well as melt pool geometry are calculated in a single model, using the continuum formulation and the volume of fluid technique. Experimental validation of model predictions is also presented.
Summary: Direct laser deposition is a solid freeform fabrication process that has the capability of direct fabrication of metal parts. The part is fabricated in a layer-by-layer manner in a shape that is dictated by the CAD solid model. A primary objective of laser deposition is to achieve porosity free deposited layers with good metallurgical bonding and minimal dilution. Of the common defects in laser deposition, lack-of-fusion (LOF) is the most damaging since it may act as a crack under certain loading conditions. This work presents prediction of LOF using a comprehensive heat transfer/fluid dynamics coupled model. This model is used to simulate the coupled, interactive transport phenomena between laser, powder, and the substrate during the laser deposition process. The simulation involves laser material interaction, free surface evolution, droplet formation, transfer and impingement onto the substrate, and melt-pool dynamics. Transient temperature and velocity distributions of the falling particles and melt pool as well as melt pool geometry are calculated in a single model, using the continuum formulation and the volume of fluid technique. Experimental validation of model predictions is also presented.
