Influence of shielding gas flow on the μLMWD of biodegradable Mg alloy and permanent stainless steel for additive manufacturing of biomedical implants

Wire feedstocks can be potentially used in additive manufacturing of customized biomedical implants. Micro laser metal wire deposition (µLMWD) can provide the dimensional resolution through the use of pulsed wave laser emission with small wire diameters (0.5 mm). Concerning the high reactivity of the biodegradable Mg alloys, the use of a wire feedstock can provide relatively safer option compared to powders. The local shielding of the process environment by an inert gas is of paramount importance for both biodegradable Mg alloys but also permanent implant materials such as stainless steel. In this work, the deposition feasibility via µLMWD of a biodegradable Mg alloy with Dy as the main alloying element (Resoloy) is studied along with a comparison with AISI 316, which has good processability. A shielding chamber was employed with oxygen content measurements during the process in order to reveal the oxygen take up or release during the process. An experimental study was employed to reveal the role of the process atmosphere on the process stability of Resoloy and AISI 316 deposits. Multiple layer deposits of the biodegradable Mg alloy were demonstrated. The results indicate that the highly reactive Mg alloy goes through a continuous oxygen intake and release during the deposition, while stainless steel mainly takes up oxygen from the environment. The deposition of multi-layered Resoloy specimens was proven to be possible to the less amount of surface oxide generated with the global shielding employed.