**Jose Exequiel Ruiz \*, Magdalena Cortina, Jon Iñaki Arrizubieta and Aitzol Lamikiz**

Department of Mechanical Engineering, University of the Basque Country, Plaza Torres Quevedo 1, 48013 Bilbao, Spain; magdalena.cortina@ehu.eus (M.C.); joninaki.arrizubieta@ehu.eus (J.I.A.); aitzol.lamikiz@ehu.eus (A.L.) **\*** Correspondence: joseexequiel.ruiz@ehu.eus; Tel.: +34-946-017-347

Received: 28 June 2018; Accepted: 6 August 2018; Published: 9 August 2018

**Abstract:** The use of the Laser Metal Deposition (LMD) technology as a manufacturing and repairing technique in industrial sectors like the die and mold and aerospace is increasing within the last decades. Research carried out in the field of LMD process situates argon as the most usual inert gas, followed by nitrogen. Some leading companies have started to use helium and argon as carrier and shielding gas, respectively. There is therefore a pressing need to know how the use of different gases may affect the LMD process due there being a lack of knowledge with regard to gas mixtures. The aim of the present work is to evaluate the influence of a mixture of argon and helium on the LMD process by analyzing single tracks of deposited material. For this purpose, special attention is paid to the melt pool temperature, as well as to the characterization of the deposited clads. The increment of helium concentration in the gases of the LMD processes based on argon will have three effects. The first one is a slight reduction of the height of the clads. Second, an increase of the temperature of the melt pool. Last, smaller wet angles are obtained for higher helium concentrations.

**Keywords:** LMD; laser metal deposition; shielding gas; argon; helium; additive manufacturing; Inconel 718; melt pool temperature
