Influence of metal structure on mechanical characteristics in high-speed coating layer fabricated via Directed Energy Deposition

Directed energy deposition (DED) is an additive manufacturing process wherein a metal powder is fed through a nozzle onto a baseplate, melted, and solidified using a laser. Potential applications of DED have been actively discussed. In this study, laser-based DED (DED-LB) was applied as a high-speed metal-coating technique to a cylindrical pipe. The mechanical properties of DED-fabricated objects were strongly affected by processing parameters such as laser power, powder feed rate, and rotational speed of the cylindrical pipe when using 20MnCr5 and M2 as the coating materials. Hardness measurements showed that the hardness of 20MnCr5 increased with a high heat input, whereas that of M2 increased with a low heat input. The two metals exhibited opposite trends in terms of hardness variation because of the differences in their transformation points. This study analyzed a layer coated with DED-LB from the viewpoint of metal morphology.