적층부와 기저부 국소 특징 형상이 DED 공정으로 제작된 인코넬 718 제품의 열-기계 특성에 미치는 영향에 관한 연구

Abstract

Directed Energy Deposition (DED) process is one of the additive manufacturing that can produce three-dimensional product, repair and remanufacturing product by depositing new layer using high density energy source such as laser. DED process is occurred thermal characteristic imbalance and residual stress because of repeated thermal history of rapid heating and cooling. The goal of this research work is to investigate the effect of local characteristic shape of the deposited region and the substrate on thermo-mechanical behaviors of the Inconel 718 part fabricated by DED process using finite element analyses (FEAs) and experiments. The deposition experiments are LENS CNC VESTA 1300 (OPTOMEC) carried out using apparatus and DABO MDR-60 (MAXROTEC). Materials of the deposition powder and the substrate are Inconel 718 and S45C, respectively. Thermo-mechanical analyses are performed to investigate variation of thermal and residual stress characteristics during the deposition. Through the comparision of the results of FEAs and those of experiments from the view point of thermal history, proper FE models are obtained. Temperature histories are measured by thermocouple (OMEGA) and data logger (GRAPHTEC) to estimate a proper heat sink coefficient of the FE models for different deposition conditions. The influence of the chamfer angle and the fillet radius of a thin wall on the substrate examined to residual stress distribution in the vicinity of the deposition region obtain suitable chamfer angle and fillet radius of the deposited region. The effects of the substrate geometry for the repair and the deposition strategy on the residual stress distributions in the vicinity of the repaired region by DED process. In addition, substrate design the influence of radius of curvature of the substrates with a double curvature geometry on the residual stress distributions in the vicinity of the deposited region to predict a proper radius of curvature of the substrate. In the future, further experiments and FE analyses are necessary to predict optimum substrate design and deposition strategy to repair the metallic part using a DED process.