Micro-Cracking in Medium-Carbon Steel Layers Additively Deposited on Gray Cast Iron Using Directed Energy Deposition

• Published in: Metals and materials international Vol. 26; no. 5; pp. 708 - 718
• Main Authors: Lee, Seulbi, Kim, Jaewoong, Shim, Do-Sik, Park, Sang-Hu, Choi, Yoon Suk
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Institute of Metals and Materials 01.05.2020; Springer Nature B.V; 대한금속·재료학회
• Subjects: Carbon steel; Characterization and Evaluation of Materials; Chemistry and Materials Science; Chromium molybdenum vanadium steels; Cooling; Crack initiation; Deposition; Electron probes; Engineering Thermodynamics; Exposure; Finite element method; Fracture mechanics; Graphitization; Gray iron; Heat and Mass Transfer; Heat treating; Hot work tool steels; Machines; Magnetic Materials; Magnetism; Manufacturing; Martensite; Materials Science; Medium carbon steels; Metallic Materials; Microcracks; Microscopy; Microstructure; Multilayers; Multiscale analysis; Processes; Scanning electron microscopy; Scanning transmission electron microscopy; Solid Mechanics; Solidification; Substrates; Thermal analysis; 재료공학; Directed energy deposition (DED); Thermal FEM; Micro-cracking; Microstructure analysis; Cast iron
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-019-00589-5

Single track and multi-layers of medium-carbon steel (AISI H13) powders were additively deposited on gray cast iron using a directed energy deposition (DED) technique. Multi-scale microstructure characterization using a scanning electron microscopy, an electron probe micro-analyzer and a scanning transmission electron microscopy, and the thermal analysis using finite element method were performed to understand the mechanism for the micro-crack formation, which was found at the single, double and triple layers of medium-carbon steel powders, except for the single track, deposited on a cast iron substrate. The crack formation mechanism was thoroughly investigated by combining the layer-by-layer chemistry variations and the resulting microstructural evolution upon exposure to thermal cycles during the DED process. It was concluded that micro-cracking was accompanied by the initiation of the local graphitization and the formation of plate martensite in the vicinity, which seemed to be kinetically facilitated by an indirect exposure to multiple heating–cooling thermal cycles, not by a direct exposure to a melting-cooling (solidification) cycle. Graphic Abstract