Process Parameters Optimisation for Mitigating Residual Stress in Dual-Laser Beam Powder Bed Fusion Additive Manufacturing

Abstract

Laser beam powder bed fusion (PBF-LB) additive manufacturing (AM) is an advanced manufacturing technology that manufactures metal components in a layer-by-layer manner. The thermal residual stress (RS) induced by the repeated heating–melting–cooling–solidification processes of AM is considered to limit the wider uptake of PBF-LB. A dual-laser beam PBF-LB strategy, with an additional auxiliary laser and reduced power, working in the same powder bed simultaneously, was recently proposed to lower RS within the manufactured components. To provide insights into the optimum PBF-LB AM configurations and process parameters for dual-laser PBF-LB, this study proposed three different coordinated heating strategies (i.e., parallel heating, post-heating, and preheating) of the auxiliary heat source. The temperature fields and RS of dual-laser beam PBF-LB, for Ti-6Al-4V with different process parameters, were computationally investigated and optimized by the thermo-mechanically coupled 3D models. Compared with the single beam PBF-LB, parallel heating, post-heating, and post-heating strategies were proved as effective approaches to reduce RS. Among these, the preheating scanning is predicted to be more effective in mitigating RS, i.e., up to a 10.41% RS reduction, compared with the single laser scanning. This work could be beneficial for mitigating RS and improve the mechanical properties of additively manufactured metal components.

Effects of Preheating on Thermal Behavior in Inconel 718 Processed by Additive Manufacturing

“…This stress has some effects on the material properties [4]. Different techniques have been adopted to improve the mechanical properties of additive-manufactured materials by changing their microstructures, such as base Thermo 2024, 4 plate preheating, optimizing process parameters, building direction, and the laser scanning strategy [5].…”

“…Thermo 2024, 4 49 properties [4]. Different techniques have been adopted to improve the mechanical properties of additive-manufactured materials by changing their microstructures, such as base plate preheating, optimizing process parameters, building direction, and the laser scanning strategy [5]. Superalloy IN718 (Inconel 718) is a common nickel-based superalloy with an outstanding mechanical performance [6].…”

“…It is therefore necessary to control the interdendritic Nb segregation, which results in the formation of the Laves phase. Subsequently, after heat treatment, it transforms into the 𝛿-phase [5]. Microsegregation of Nb and Mo can be observed after laser irradiation in SLM, resulting in the precipitation of the interdendritic brittle Laves phase [8].…”

“…Base plate preheating can reduce the residual stress [10] and change the mechanical properties [11]. This will also result in low Nb segregation [5]. Additionally, base plate preheating can heat the powder, leading to a reduction in the possibility of oxidation as moisture is eliminated from the powder [3].…”