Direct metal deposition by diode laser – Modelling the effect of increased beam coupling Available to Purchase

The recent emergence of high powered diode laser direct metal deposition (DMD) as an alternative to the more established CO₂- and Nd:YAG-powered methods has the potential to make it a generally more energy efficient and industrially accessibly process. Not only does the diode laser itself consume less energy, but the coupling between the incident laser radiation and metallic feed stock, melt pool and solid substrate material is enhanced. The overall effect, however, is not a simple increase of efficiency, but a redistribution of the input process energy, and resulting changes in the major dependent process variables. In this work, coaxial DMD systems using these three main laser types are modelled analytically in terms of energy balances. Novel modelling methods and empirical matching to experimental results are used to derive a series of equations, from which the power distribution, pool length and mean pool temperature can be derived for different initial laser powers and properties. The model is applied to a real system and predicts results in good agreement with experimental values. The model highlights reflection from the melt pool and conduction to the substrate as the major energy distribution pathways. The differences in melt pool geometry and temperature obtained with the different lasers are significant and explain the higher build rates and high thermal load on the substrate found when using a high power diode laser (HPDL).