关键词: 定向能量沉积, 激光熔化沉积, 熔池, 形状精度, 增材制造

Abstract: Due to complex influence mechanisms and process features, low quality reliability, processing repeatability and adaptive control ability are important problems in laser-based direct energy deposition. Dynamic characteristics of molten pools are monitored by coaxial visual monitoring and present the influence mechanism of the dynamic characteristics on evolution behaviour of geometrical accuracy in laser-based direct energy deposition. Four typical processes are main objects investigated. In single-track single-layer cladding, contour profiles and special grayscale region area have a direct relationship with surface qualities and width stability of molten pools. In single-track multi-layers accumulation, geometry and characteristics of molten pool tails have important effect on the change of deposition widths. In multi-tracks single-layer overlap, gradual increasing widths of molten pools and different powders utilization ratios leads to a decrease of surface geometrical accuracy based on traditional overlap models. In single-track multi-layers overhang accumulation, molten pool areas in both sides and molten pool collapse indicate the evolutionary process of incline edges and the overhang maximum. The results show the dynamic characteristics of molten pools can be used to study the evolution behaviours of key geometrical accuracy, and helpful for building geometrical models. The dynamic characteristics of molten pools are also beneficial for the researches about process planning and real-time feedback control.

Key words: additive manufacturing, direct energy deposition, geometrical accuracy, laser melting deposition, molten pool