Evolution of molten pool morphology and prediction of inclined cladding layer morphology

Abstract

Laser cladding is a process in which multiple physical fields and multiple factors are coupled. Metal particles are fed into the melt pool to form a cladding layer through melting and solidification. The temperature and flow field in the melt pool affect the pool morphology, especially for inclined surface cladding, which ultimately affects the shape quality. In this study, based on a combination of experiments and simulations, the influence of the melt pool flow on the melt pool morphology in the laser cladding process is studied, the influence of the substrate sulfur concentration on the flow field is analyzed, and a prediction model for the morphology of the inclined clad layer is established. The results showed that the variation of the sulfur concentration on the melt pool surface significantly affected the Marangoni convection in the melt pool, which influenced the melt pool morphology. As the sulfur content decreased, the melt pool morphology evolved through three stages: circular arc melt pool morphology, bowl melt pool morphology, and double arc melt pool morphology. The melt pool morphology after solidification was between the melt pool morphologies produced by positive and negative values of the surface tension temperature coefficient. The model prediction results and the experimental results were in good agreement, and the relative errors of the width, height, and depth of the molten layer were within 8%. The agreement of the molten layer offset was poor, and the maximum relative error was 8.2%, which was because the effects of the powder and protective gas on the melt pool were neglected. The model can predict the values of the width, height, offset, and depth of the melt of the clad layer with the inclination of the substrate within an error range of 10%, which provides theoretical guidance for the study of the inclined formation mechanism and the optimization of the process parameters.