Characterization and modeling of deposition geometry in directed energy deposition over inclined surfaces

摘要

Directed Energy Deposition (DED) is setting a relatively new trend for the repair and restoration of high value components. Repair of these components necessitates contoured depositions due to the complexity in the geometry. This further demands depositions at various inclination angles. The influence of inclination angle needs to be studied so as to predict the final deposition geometry which will be a function of the powder loss and the melt-flow. Therefore, this study is aimed at exploring the effect of inclination angle on the powder catchment efficiency and shape evolution of the deposited track. Asymmetry is observed in the cross-section of the deposited track while carrying out the DED at an inclination. A two-dimensional transient heat transfer model with fluid flow has been developed to predict the temperature distribution, track melt pool boundary during the deposition process. The solidification and the arrest of the melt pool flow is accounted by employing the enthalpy porosity model. The model is used to predict the deposition geometry. Predicted deposition geometry values agree reasonably well with the experimental results. This model is used to recognize the factors contributing towards this asymmetry during the deposition at inclination. The study reveals that there is a substantial drop in the powder catchment efficiency from 66% to 19% as the inclination angle is increased from 0o to 75o. In order to have uniform clad, increasing mass flow rate is a viable option as the catchment efficiency is almost unchanged with increasing mass flow rate.