Analysis and modeling of melt pool morphology for high power diode laser cladding with a rectangle beam spot

Abstract

Dynamic behavior of a melt pool reflects the internal heat transfer, convection and mass addition in laser cladding, and it is closely related to the complex geometry and quality of the cladding layer. A machine vision system was built to directly detect and measure the melt pool morphology in wide-track laser cladding by high power diode laser (HPDL) with a rectangle beam spot (RBS). The captured images were processed with image processing technology to obtain the geometry profile and the characteristic parameters of the melt pool such as width (Wm), length (Lm) and area (Am). A full factorial experiment with pre-placed powder method was conducted to obtain the correlation between the geometrical characteristics and the process parameters. The effect of the process parameters including laser power, powder thickness and scanning speed on the Wm, Lm and Am were analyzed in detail. A nonlinear fitting model was used to fit the relationship between the process parameters and the geometrical characteristics. And a mathematically defined curve was adopted to describe the melt pool geometry profile. The above model was confirmed by all the experiments. The results indicated that the Wm, Lm and Am will increase with increasing laser power, while increasing scanning speed will cause the decreasing of the melt pool size. Moreover, the Wm and Lm can be predicted by the process parameters, and the melt pool contour profile can be well described as the curve.