LENS 공정을 이용한 인코넬718 분말과 S45C 기저부의 이종 재료 적층에서의 적층 특성 분석

Abstract

A laser engineered net shaping (LENS) process is one of directed energy deposition (DED) processes. The LENS process has been widely used to deposit superalloy on a metallic substrate. The quality of the deposited region depends upon deposition characteristics between the deposited material and the substrate. The goal of this thesis is to investigate deposition characteristics of Inconel 718 powders condition is obtained from deposition experiments for a single bead. Using the proper deposition condition, several specimens with a large deposition area are fabricated. In order to simulate a thermo-mechanical behavior in the vicinity of the deposited region by a LENS process, a finite element (FE) model with a moving heat flux is developed using a SYSWELD. The heat source for the deposition depth. A gaussian distribution is adopted to simulate in-plane intensity distribution of the heat flux. Temperature dependent thermal and mechanical properties considering a phase change are applied to the FE model. Repeated FE analyses are carried out to investigate heat transfer phenomenon and residual stress evolution during deposition and cooling stages for cases of in-plane depositions, including a single bead, a double bead, a quintuple bead, and out-of-plane depositions with four layers. From the results of FE analyses, the effects of the deposition strategy on temperature distributions and thermal histories in the vicinity of the deposited region. In addition, the influence of the substrate hardness on residual stress distributions of the deposited region and the substrate is examined.