Estimation of Bead Size and Catchment Efficiency in Laser Cladding

Abstract

This paper presents for the first time a set of closed-form predictions for the width, height, and catchment efficiency of laser-clad beads accounting for the distributed nature of the heat source and powder feed. These predictions are based only on known process parameters such as travel speed, laser power, powder feed rate, and material properties. The mathematical analysis is based on the methodology of asymptotics and blending, and the experimental work was performed in actual industrial conditions. To calculate the thermal efficiency of the process, a mathematical expression as a function of powder feed rate is framed, taking into consideration the shadowing due to the powder cloud. In calculating catchment efficiency, the fraction of powders falling on and ahead of the melt pool is calculated and the results reveal that the fraction falling ahead of the melt pool is negligible and does not contribute to the catchment. Predictions are quantitative and within the error expected for industrial conditions and tabulated material properties. Estimates of the height of the bead are greater than the measured height for every case by an average of 18%. Estimates of width and catchment efficiency are within the range of ± 10%, except for the cases of the low power and higher travel speed domains where a large deviation is observed.