DMT 공정을 이용한 초합금 분말과 S45C 강의 이종재료 적층 시 적층 특성 고찰

Abstract

A directed energy deposition (DED) process is a representative metal additive manufacturing (AM) technology to create a three-dimensional (3D) part with different materials. The quality of the fabricated part with different materials is greatly dependent on deposition characteristics between the deposited region and the substrate. The objective of this thesis is to investigate dissimilar deposition characteristics between super-alloy powders and S45C steel using a laser-aided direct metal rapid tooling (DMT) process through finite element analyses (FEAs). Inconel 625 and Stellite21 super-alloys are chosen as materials of deposited powders. A 3D FE model is created to simulate a thermo-mechanical phenomenon in the vicinity of the deposited region during deposition and cooling. The laser is assumed to be a volumetric heat flux with the gaussian distribution in a plane and the penetration depth. Temperature dependent thermal and mechanical properties, including effects of a phase change, are adopted. A proper efficiency of the heat flux is estimated by comparison of results of FEAs and those of experiments. Repeated FEAs are carried out using a commercial software SYSWELD. FEAs are performed for cases of in-plane deposition, including a single line, a double line and multiple lines, and out-of-plane depositions. From the results of FEAs, the influence of the deposition path, the deposited material and the interpass time on temperature, micro structure and residual stress distributions in the vicinity of the deposited region is examined. In addition, the effects of the hardness of the substrate on microstructure and residual stress distributions in the substrate are discussed.