Entropy generation analysis of turbulent transport in laser surface alloying process

Abstract

A numerical formulation involving second law of thermodynamics is examined for analysis of three-dimensional surface tension driven turbulent transport during laser materials processing. A modified k–ϵ model is used to address turbulent melt pool convection in the presence of a continuously evolving phase change interface. Phase change aspects are addressed using a modified enthalpy–porosity technique. It is revealed that both energetic and exergetic efficiencies increase with increasing laser power, and remain insensitive to changes in powder feedrate over the range of parameters chosen. However, the energetic efficiency is found to increase with increasing laser scanning speed whereas the exergetic efficiency shows a reverse trend. Accordingly, a tradeoff in the laser scanning speed can be sought for while designing the process parameters, in order to ensure a maximum utilisation of the thermodynamic potential offered by the intense laser heat source.