고탄소 공구강 분말의 직접 에너지 적층 공정 시 결함 방지를 위한 중간층 적용에 관한 연구

Abstract

In recent years, with the development of metal 3D printing technologies using a laser or an electron beam, technologies to reinforce the surface of metal components in various shapes, have been applied. In particular, direct energy deposition (DED), an additive manufacturing (AM) technique which is used to manufacture various 3D products by depositing materials on a metal substrate using a layer-by-layer method, has been researched as a technology to repair metal components and reinforce surfaces. This technology can produce parts with lower residual stress and mechanical properties when compared to the parts produced by conventional methods. It can also minimize the HAZ, which causes property degradation, and it has been commonly used for hardfacing by depositing high-hardness powder on the metal surface. Owing to these benefits, the DED process is expected to replace the conventional methods. The aim of this study is to obtain high surface hardness and a perfectly bonding between the AISI M2 deposits and a substrate utilizing a intermediate layer that is AISI P21. To prevent interfacial cracks between the M2 deposits and the substrate, the P21 powder is pre-deposited onto a SCM420 substrate, before the deposition of M2 powders. Interfacial cracks occurring between the deposits and substrate and changes in the microstructure of the intermediate layer were examined. The influence of intermediate layer on the mechanical properties was then analyzed on the deposited material. These properties were compared with those of the carburized SCM420. As a result of the bending test for evaluating the bonding strength, the crack at the interface did not propagate. Elongation and Absorbed energy were also remarkable. High wear resistance and tensile strength were obtained due to the M2 deposited layer on the surface. In the case of hardfacing with high carbon tool steel using P21 intermediate layer, it is confirmed that interfacial defects can be prevented by depositing an intermediate layer with ductile properties and then surface hardness was remarkable due to the M2 high carbon tool steel powder.