Research on the temperature control strategy of thin-wall parts fabricated by laser direct metal deposition

Abstract

To solve the problem that the macro-size, microhardness, and mechanical properties of the laser direct metal deposition (DMD) of thin-walled parts are inconsistent due to the heat accumulation, an improved three-dimensional finite element heat propagation model was developed to simulate the temperature evolution of the single-pass multi-layer thin-walled parts.The results show that the heat accumulation is contributed to the transformation of the heat dissipation mechanism from three-dimensional to two-dimensional, while the residual heat of the former layer has no significant effect on the heat accumulation of the current layer. The optimized strategy of decreasing laser power gradually is more effective than the optimized strategy of increasing the time interval between layers in maintaining the stability of the molten pool. The integrated optimized strategy of parabolic-shape laser power decreasing and time interval of 5 s is the most effective method to reduce the heat accumulation in the DMD of thinwalled parts. The thin-walled parts with an optimized deposition process have a more uniform width, finer microstructure, and higher microhardness. This work provides theoretical guidance for reducing the heat accumulation during DMD thin-walled parts and is beneficial to improving the uniformity of mechanical properties of thin-walled parts.

Monitoring Variability in Melt Pool Spatiotemporal Dynamics (VIMPS): Towards Proactive Humping Detection in Additive Manufacturing

“…This phenomenon can be explained by the variations in emissivity associated with different phases of the material, which affect its heat radiation. According to the Stefan-Boltzmann law, the total radiation (P rad ) emitted by a body is a function of both its temperature (Temp) and its emissivity (ϵ), expressed as P rad = σϵATemp 4 , where σ represents the Stefan-Boltzmann constant. In the case of stainless steel, the liquid phase exhibits a lower emissivity compared to its solid counterpart [27], especially when the solid is oxidized [28].…”

“…This advantage of material delivery in DED comes with significant challenges. Unlike powder bed processes, where the powder is laid statically, the DED material's dynamic delivery complicates the heat dissipation [4,5]. The continuous and localized addition of material generates varying heat intensities and gradients, leading to a complex thermal profile within the heat-affected zones.…”

VIMPS: Physics-Based Spatiotemporal Indicator for Proactive Humping Detection in Metal Additive Manufacturing

“…This phenomenon can be explained by the variations in emissivity associated with different phases of the material, which affect its heat radiation. According to the Stefan-Boltzmann law, the total radiation (Prad) emitted by a body is a function of both its temperature (Temp) and its emissivity (ϵ), expressed as Prad = σϵATemp 4 , where σ represents the Stefan-Boltzmann constant. In the case of stainless steel, the liquid phase exhibits a lower emissivity compared to its solid counterpart [27] especially when the solid is oxidized [28].…”