A high-efficiency additive manufacturing technology that combines a high-power diode laser with a large-rectangle spot (beam width of 11 mm) and a hot-wire system was developed. The hot-wire system can generate Jo ule heat by wire current and heat a filler to its melting point independently from the main heat source of a high-power diode laser. A simple calculation method to derive the appropriate hot-wire current of Z3321-YS308L was proposed with verification by hot-wire feeding experiments without laser irradiation at various wire currents. The effect of process parameters, such as laser power, process speed, and the wire feeding rate (wire feeding speed/process speed) on bead characteristics was investigated by cross-sectional evaluations on three-layer depositions. High-speed imaging observations of wire melting and molten pool formation showed that the energy density input and the wire feeding rate were dominant parameters in terms of bead formation and hot-wire feeding stability. A 50-mm-high, 8-mm-wide, and 250-mm-long sample was fabricated by using appropriate process conditions, and tensile tests were performed by using a sub-sample from the large sample.

The aim of this research was to develop a high-efficiency and high-material-use additive manufacturing technology using the hot-wire laser method. In this study, the optimization of process conditions using a combination of a high-power diode laser with a relatively large rectangular laser spot and a hot-wire system was investigated. The effects of process parameters such as laser power, process speed, and wire feeding rate (wire feeding speed/process speed) on a bead appearance and cross-sectional characteristics (e.g., effective width, effective height, maximum height, and near net shape rate) were studied in detail. The process phenomena during the multi-layer deposition were investigated by in situ observation via a high-speed camera.

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