Wire-based Directed Energy Deposition (W-DED) using a blue diode laser was developed to achieve a low-dilution pure copper layer with high energy efficiency. To clarify the dominant factor of the dilution of the layers, pure copper layers were formed on SUS304 substrates using a W-DED system with a blue diode laser where the wire feed rate and the laser power density were varied. As a result, a pure copper layer with a dilution ratio of 0.1% was formed with an energy efficiency of 30.8×10^－3mm³/J at a wire feed rate of 450 mg/s and a laser power density of 7.7×10⁴ W/cm². Furthermore, when forming this layer, more than 90% of the heat input required for wire melting was provided by direct heat input from the laser. On the other hand, when more than 50% of the heat input required for wire melting was provided by the heat conduction from the molten pool, only layers with high dilution ratio were obtained with low energy efficiency. Therefore, a low-dilution pure copper layer was formed with high energy efficiency when the direct heat input from laser accounts for the majority of wire melting.

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