Experimental study of a titanium cold sprayed layer on an aluminum substrate

In the manufacturing of metal components both wear and corrosion have to be considered. In particular corrosion is a very important problem in the aeronautic field, were the aluminum alloys are widespread used, but are affected by several corrosion typologies. Furthermore nowadays carbon fiber reinforced plastics (CFRP) are finding an increasing use, but they can induce galvanic corrosion phenomena when coupled with aluminum alloys. To overcome this problem corrosion resistant coating are used on aluminum components. Otherwise titanium alloys have a very high corrosion resistance and furthermore no galvanic corrosion phenomena arise when coupled with CFRP. On these premises the realization of a titanium coating on aluminum components could allow the use of aluminum alloys coupled with CFRP and improve the corrosion resistance of the above mentioned alloys. The aim of this paper is to study a titanium coating builded on an aluminum substrate by means of the cold spray technique. This technique allows to produce near fully dense coatings. Despite the promise this technique has shown, questions remain about the quality of the material deposited in terms of adhesion strength of coating to substrate, and cohesion strength between cold sprayed particles that make up the coating. In this paper titanium coatings on AA 6082 substrate were carried out and tested. In particular pure titanium powder were used to build up the coating. An experimental campaign was carried out including mechanical, microstructural and electrochemical tests. Furthermore sliding tests, by means of a pin-on-disk apparatus, were carried out in order to study the wear properties of the coating. The results obtained showed a quite compact coating with few porosity, moreover the coating showed a good internal cohesion and a good adhesion with the aluminum substrate, also the electrochemical properties were interesting.