Effect of Mixing N2/He as Cold Spray Atomizing Gas on Ti6Al4V Properties

Additive Manufacturing of metals is a ground-breaking approach to manufacturing. Significant developments have been occurring during the last 5 years, mainly in the aerospace industry, where the Ti6Al4V alloy is widely applied. Cold Spray (CS) is a thermal spray process recognized by its principles, accelerating the particles to high velocity, but relatively low temperatures, which is a tremendous attraction to produce the oxygen-sensitive Ti alloys. Ti6Al4V presents a challenge for the low-temperature spraying process because it has low deformation and, consequently, higher porosity than other ductile sprayed materials, such as Al or Cu. An alternative presented in the literature to avoid it is the use of He as CS working gas, aiming even higher velocity of particles; however, He is much more expensive than N2, making unfeasible its use on an industrial scale.

This work evaluates the effect of mixing He/N2 in different ratios as CS working gas on the Ti6Al4V characteristics. The samples were evaluated by microstructural characteristics, porosity, microhardness, and deposition efficiency, besides a critical assessment of the part shape geometry and layer thickness. An exciting result was that not the highest content of He in the gas mixing promoted the best overall effect.