Laser absorption within a powder layer and the numerical modeling of heat transfer during the laser cladding process

In previous experimentation, it has been shown that laser energy incident onto a powder layer is absorbed within the layer; however, when modeling a powder based laser deposition process, it is common practice to assume surface loading only. The current work explores incorporating through thickness absorption into an existing thermal model. The absorption model is based upon an analytical relationship derived through consideration of conservation of energy to describe the amount of laser energy absorbed within pre-placed powder during the laser deposition process. The relationship may be used to define internal absorption due to scattering within the powder layer regardless of the beam shape and energy distribution if the attenuation coefficient and bulk absorption is known. The internal absorption model is incorporated into a thermal numerical model to predict temperature profiles, heating and cooling rates, and melt depths during the cladding process. Experiments were completed to validate the numerical model. Temperature profiles and melt depths obtained during the experiment are then compared to model output and discussed.