Optimization of Process Conditions for Additive Manufacturing Technology Combining High-Power Diode Laser and Hot Wire

Abstract

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.

A Review on Wire-Laser Directed Energy Deposition: Parameter Control, Process Stability, and Future Research Paths

“…Liu et al reported the same instabilities as Zhu et al [108] in preheating with different voltages by noting that at a high voltage, arcing occurred, and large spatters were generated [191,192]. They also compared the influence of increasing laser power and preheating voltage on the process stability and geometrical appearance of the beads.…”

“…Similarly, Huang et al [47] confirmed the height increase with an increase in WFS in aluminum alloy. However, an increased mass of wire resulted in an augmented melt pool volume per unit length and, consequently, increased bead width [108]. Such deviations exist in the literature when utilizing various materials with increasing WFS.…”

“…To regulate the deposition rate, speed ratio or K value have been used in literature to correlate WFS and TS (Equation ( 6)) [25,62,[108][109][110].…”

“…As laser power increases, the melt pool temperature increases significantly; therefore, a larger melt pool is formed due to the remelting of the substrate. Simultaneously, the solidification rate of the melt pool diminishes, causing the molten metal to flow outward before cooling [47,56,108,110].…”

“…The wire-resistant current, a crucial factor influencing wire melting and feeding, is addressed by Zhu et al It is observed that when the current is too low, i.e., when the wire tip temperature is below the melting temperature, the hot-wire tip sticks on the surface frequently (Figure 30a). On the other hand, when the wire current is too high, fusing and spattering occurs because the hot-wire temperature reaches its melting point before contacting the substrate (Figure 30c) [108]. Huang et al conducted an experiment studying the melting behavior of pre-heated aluminum alloy wire using resistance heating.…”