Laser beam - Material interaction and thermal absorption model validation

A thermo-absorption model for calculation of the heat transfer is proposed and experimentally validated for a laser directed energy deposition process. The bulk absorption (ß) may be defined as the ratio of the total power absorbed by the substrate (P_abs) to the laser power presented to the substrate (P_i). When combined with a value for exposure time, these terms may describe the energy absorbed and energy presented, respectively. The laser energy presented to the substrate may be accurately measured with a beam calorimeter, while the energy absorbed by the substrate can be obtained through process calorimetry measurements. Alloys Ti-6A1-4V and Inconel 625 were both evaluated using the process, and the tests were conducted at laser powers ranging from 1 kW to 2 kW. Experimental results determined the bulk absorption coefficient for the process with and without powder flow during laser deposition.