Melting behaviour of a powder bed under laser irradiation

In order to gain an in-depth understanding of the pulsed laser cladding process with a pre-placed powder bed, numerical models based on FEM have been developed. This paper reports the first phase of the work on modelling, which studied the melting behaviour of a powder bed at the particle level, i.e. individual powders and voids, were considered. The model employed fluid dynamics to simulate the temperature and the fluid velocity fields of a partially melted powder bed subjected to laser irradiation, taking into consideration, inter alia, melting of the powders and the effect of surface tension. In the model, the complication produced by the moving boundaries of solid/liquid and gas/liquid was successfully resolved by using the 'Volume of Fluid (VOF)/Continuum Surface Force (CSF)' capability of ANSYS. With this model, the major features regarding the temperature and velocity fields as well as the shape of the molten pool during melting of a powder bed were established. Inc.