Stellite 21로 하드페이싱된 열간 단조 금형의 열응력제어층 설계 연구

Abstract

Hardfacing process using metal 3D printing is being studied to improve the life of the die during the hot forging process. At this time, thermal fatigue can occur because of thermal expansion coefficient differences between two materials; substrate and hardfaced layer and the concept of a thermal stress control layer(TSCL) is introduced to solve this problem. In this study, we would like to select position and thickness of hardfaced layer and predict the proper shape, mixing ratio of Stellite 21 and thickness of TSCL for harfaced hot forging die via axi-symmetric finite element analysis. As a result of wear test of hardfaced die based on the results of wear analysis, it was confirmed that the die life was increased. The initial shape of TSCL for finite element analysis was selected by deposited certain region. The thickness of TSCL ranges from 1~2 mm. The results of each design were analyzed by deviation of maximum principal stress used to observe the possible separation at the interface. The proper design was selected as 50% of Stellite 21 mixing ratio and 1 mm thickness, but the thermal stress at the boundary of interface occurred large value. In order to this problem, the finite element analysis was performed by changing the shape of TSCL to deposit as a whole region on the substrate. Based on the results of deviation of maximum principal stress at the interface, a proper design was derived. As a result, it was found that the thickness was 1 mm and the Stellite 21 mixing ratio was 50%.