Evaluation of Powder Properties on the Performance of Cold Sprayed Ti6Al4V for Aerospace Repairs

The information presented in this paper is part of the work conducted within the CORSAIR project, an EU funded collaboration, which aims to improve the performance, reliability and flexibility of the existing cold spray systems for repair applications. Within the consortium are aerospace companies, materials suppliers, equipment manufacturers and end users, working together to produce guidelines on material specification and process development for the validation of the cold spray process for the maintenance and repair of aeronautical components.

The quality of a cold spray coating is heavily dependent on the characteristics of the powder, with feedstock selection being a crucial step in the production of high quality, repeatable and reliable coatings. Within this work, several commercially available Ti-6Al-4V powders were characterised with respect to their chemical composition, oxygen content and physical properties (particle morphology, shape factor, size distribution, apparent density). Cold spray deposited coatings produced from these were analysed and evaluated through a combination of microstructural evaluation and mechanical testing, with the aim of correlating the chemical and mechanical characteristics of the powder to the reliability, strength and quality of the coating.

The results demonstrated that powder feed stocks with higher contents of fine particles tended to produce denser coatings with higher deposition efficiency, with a powder cut of -32µm producing the densest coatings. Deposition of coatings using a single pass at low gun traverse speed (230 mm.s^-1) resulted in denser and harder coatings than those deposited using multiple passes at higher speed (700 mm.s^-1). Deposition at a 60 degree spray angle with the substrate led to softer and less dense coatings than deposition normal to the substrate.