Real-time monitoring of temperature history of molten pool and corresponding relationship with processing quality in LMD

Purpose: The purpose of this study is to investigate the changes in the processing parameters of laser melting deposition (LMD) on the temperature and morphology of the molten pool, and to provide control strategies and basis for further feedback control. Design/methodology/approach: This paper is based on LMD equipment and sets up an online monitoring device. The online monitoring device mainly includes an optical camera and a pyrometer. Evaluate the impact of changes in process parameters on the printing process by testing the macroscopic morphology, microstructure and mechanical properties of the samples. Findings: The changes in scanning speed mainly cause changes in the depth of the molten pool, without affecting the temperature of molten pool. Meanwhile, the change of laser power has a significant impact on the temperature of molten pool, as well as on the size and depth of molten pool. In addition, the change of temperature and dimensions of the molten pool would affect the temperature gradient and cooling rate, resulting in the difference between the final grain size and the number of equiaxed grains. Subsequently, these factors would affect the tensile properties and plastic toughness of the final formed parts. Originality/value: In others’ earlier and the authors’ experiments, they found that changes in scanning rate had little effect on the temperature and surface area of the melt pool, but they did not pay attention to this phenomenon. The authors’ have studied this phenomenon in experiments and provided an explanation.