Plasma enhanced chemical vapour deposition (PECVD) at atmospheric pressure (AP) of organosilicon films for adhesion promotion on Ti15V3Cr3Sn3Al and Ti6Al4V

The recent generation of aircraft is manly built out of CRFP (Carbon fiber reinforced plastic). To ensure galvanic compatibility Titanium alloys are used at connecting points to metallic structures. The increased use of Titanium alloys due to their good mechanical properties has highlighted the need for structural bonding as joining method to combine Titanium with CFRP. However, long-term stable adhesion on Titanium is still an issue. Currently mainly wet-chemical processes are applied to improve adhesion on Titanium alloys. Since wet-chemical treatments often comprise the use of hazardous chemicals dry environmentally friendly surface functionalization processes are pushed more into focus. PECVD (Plasma enhanced chemical vapour deposition) at AP (Atmospheric pressure) seems to be favorable for the deposition of silicon dioxide films as an adhesion promoter layer. In the present work, the deposition of silicon dioxide adhesion layer (from HMDSO (Hexamethyldisiloxane) as precursor) on titanium alloys is described for a linearly extended and scalable DC arc plasma source (LARGE). The wedge test is used to evaluate the adhesion properties of coated titanium samples in comparison to the standard used NaTESi anodizing process. The results show that the atmospheric pressure plasma process leads to good long-term durability and to high bonding strength which is comparable to the used standard pre-treatments.