DED 공정을 이용한 SCM440 기저부 위 G6 분말 적층시 기저부 형상과 적층 전략이 적층 영역 열-기계 특성에 미치는 영향

Abstract

Directed energy deposition (DED) processes can create three-dimensional metallic parts through layer-by-layer deposition of metallic materials with types of powder and wire on the metallic substrate. A rapid temperature change is taken place in the vicinity of the deposited region for the deposition. The rapid temperature change subsequently provokes an excessive residual stress in the vicinity of the deposited region. Especially, in the section where the deposition shape changes rapidly, the stress concentration phenomenon occurs and the deformation and cracking tend to intensify. The goal of this study is on the influence of the substrate shape and the deposition strategy on thermo-mechanical characteristics of the deposited region to deposit G6 powders on SCM440 substrate using a DED process. In addition, we would like to select an optimal substrate shape and the deposition strategy to reduce residual stress. Characteristic data related to the formation of the deposited region and corresponding deposition conditions for the FE model are provided by DN solutions Inc.. To select a finite element analysis model according to substrate shape, candidates were selected for substrate inclination angle, deposition height, and deposition length, and a 2D analysis model for straight lines and curves was designed according to the Z-axis direction. The validity of the two-dimensional interpretation was derived through the comparison of two-dimensional and three-dimensional interpretations. Temperature-dependent thermo-mechanical properties of G6 and SCM440 considering phase changes are obtained from JMat Pro. Software. The laser beam is assumed to be moving volumetric heat source with gaussian intensity distribution in a plane and penetration depth. Residual stress was predicted and compared according to substrate shape through thermal-mechanical analysis, and the reason for high residual stress was investigated through thermal history. For two-dimensional analysis according to the deposition strategy, the residual stress distribution was confirmed and the displacement was compared through thermal-mechanical analysis by adjusting the deposition path, interpass time, interlayer time, and distance to the reference point. Finally, a finite element analysis model was created according to the pores generated between deposition, and the changes in internal stress during product damage were compared and analyzed by comparing the existing analysis model and thermal-mechanical characteristics.