Cold Spraying of Armstrong Process Titanium Powder for Additive Manufacturing

Abstract

Titanium parts are ideally suited for aerospace applications due to their unique combination of high specific strength and excellent corrosion resistance. However, titanium as bulk material is expensive and challenging/costly to machine. Production of complex titanium parts through additive manufacturing looks promising, but there are still many barriers to overcome before reaching mainstream commercialization. The cold gas dynamic spraying process offers the potential for additive manufacturing of large titanium parts due to its reduced reactive environment, its simplicity to operate, and the high deposition rates it offers. A few challenges are to be addressed before the additive manufacturing potential of titanium by cold gas dynamic spraying can be reached. In particular, it is known that titanium is easy to deposit by cold gas dynamic spraying, but the deposits produced are usually porous when nitrogen is used as the carrier gas. In this work, a method to manufacture low-porosity titanium components at high deposition efficiencies is revealed. The components are produced by combining low-pressure cold spray using nitrogen as the carrier gas with low-cost titanium powder produced using the Armstrong process. The microstructure and mechanical properties of additive manufactured titanium components are investigated.

Sintering in global material perspective

“…As an example, in order to make AM (additive manufacturing) economical, cold gas dynamic spraying (CGDS) has been introduced, where powder characteristics have shown a similar effect as that of conventional pressing/sintering route. The use of Armstrog titanium powder (coral type morphology), with much more cost-effectiveness, applying a low temperature and a low pressure nitrogen as propellant gas [26] is an example. A post-deposition heat treatment (sintering) reduced porosity and internal stresses and improved mechanical properties,…”

A comparative review on cold gas dynamic spraying processes and technologies

“…At a supersonic velocity, particles impact and plastically deform on the substrate. The deformation process results in adhesion to the surface [5][6][7][8][9][10].…”

The influence of powder properties on the adhesion strength and microstructural evolution of cold sprayed Ti6Al4V single splats

“…Recently, Ti and Ti6Al4V powders with irregular morphology were manufactured using an Armstrong process, which is more economical compared to the PGA process [16,17]. Cold spraying these powders produces deposits that are more dense than deposits made with PGA powders [16,18]. In our previous study [18], the cohesive strength of coatings made with PGA and Armstrong powders was evaluated by multi-scale indentation.…”