In-situ heat treatment via preheating and liquid cooling during high-speed coating of gears by directed energy deposition

Automobile electrification has increased demand for higher-performance gears in drivetrains with specialized functional requirements beyond what conventional carburizing heat treatment can deliver. While carburizing is effective for mass production, it faces inherent limitations in achieving advanced material properties needed for next-generation applications. Therefore, this study proposes a high-speed coating method on rotational gear surfaces using directed energy deposition (DED). The proposed method can form the coating layer continuously and efficiently on the complex-shaped teeth of the gear, compared to the common method that forms coating along a complicated path matching the part’s geometry. Furthermore, a localized heat treatment system integrating laser preheating and liquid cooling is introduced to precisely control material characteristics of the coating layer. Experimental results demonstrate that this combined heat treatment achieves a crack-free, hard coating layer on preformed gears. This method shows significant potential for producing customized, high-performance gears for specialized applications in next-generation vehicles while reducing process complexity.