Cold Spray Deposition of Titanium onto Aluminium Alloys

The aluminium alloy 7075-T6 is widely used in aeronautic engineering due to its high mechanical resistance to weight ratio. Depending upon the environmental conditions, many types of corrosion mechanisms have been found to occur in aircraft structural aluminium alloys. A possible solution to improve the alloy’s behaviour is the deposition of a pure Titanium coating. At present the deposition of Titanium is limited to processes such as Electroplating, Chemical Vapour Deposition and Vacuum Plasma Spray. These traditional approaches are generally slow and expensive, while the common thermal spray processes have two major limitations which are the presence of porosity and oxides in the spray-deposited material. Since Titanium is a metal very sensitive to oxidation, it is proposed in the present work to deposit it onto Aluminium substrates by a novel thermal spray process known as “Cold Spray”. In this work, the influence of the gas pressure and temperature, and the powder feeding rate on the cold spray process and in the final coating characteristics was studied, and a dense pure titanium coating onto aluminium 7075 substrates, with thickness higher than 300μm and no microstructural changes was easily and fast obtained. It was possible to conclude that after optimization, the cold spray process when compared to the conventional thermal spray techniques, results in coatings with very good properties and cost-time effective (higher coating thickness can be achieved in less time and with less money investment), making it ideal for industrial applications. A liga de alumínio 7075-T6 é amplamente utilizada na aeronáutica devido à sua elevada rela o resistência mecanica/peso. Porém está sujeita a diversas formas de corros o resultantes dos diferentes ambientes em que se encontra inserida. Uma possível solu o para melhorar o comportamento desta liga em situa es de corros o é o seu revestimento com uma camada de titanio puro. Porém, uma vez que o titanio é um metal extremamente sensível à oxida o, a sua deposi o no estado puro encontra-se limitada a processos como a Electrodeposi o, Chemical Vapour Deposition ou Vacuum Plasma Spray, que s o técnicas lentas e dispendiosas. Este trabalho prop e a deposi o deste metal num substrato de alumínio 7075 através de uma tecnologia inovadora de deposi o a frio conhecida como Cold Spray. A influência de diferentes parametros de deposi o é estudada (temperatura e press o do gás de processo, velocidade de alimenta o do pó) e foi possível obter um revestimento de titanio puro superior a 300μm, de forma rápida e fácil, s