Silicon sputtering as a surface treatment to titanium alloy for bonding with PEKEKK

Thermoplastics, having strong polar or hydrogen bonding groups, are potential candidates for thin film bonding. In this investigation, a thermoplastic polymer poly(ether ketone ether ketone ketone) (PEKEKK) is used as an adhesive to bond the titanium alloy (Ti–6Al–4V). The titanium alloy is silicon-sputtered to improve the bond strength to PEKEKK. The bond strengths of butt-joined specimens prepared using silicon-sputtered, silane-coated, sodium hydroxide-anodized round bars of titanium alloy as adherends are determined and compared with that of untreated titanium alloy round bars. Of the various thicknesses of silicon layers studied, layers that are 200 Å thick proved to have a more durable bond, as demonstrated by soak test results in Ringer’s solution. It is observed that silicon sputtering enhances the bond strength of titanium alloy/PEKEKK butt joints and provides a more resistant interface to intruding water. The combination of anodization followed by silicon sputtering further improves the durability of the bond. It is confirmed by XPS analysis that fracture does not take place between the silicon and the titanium substrate. Wetting studies by contact angle method using water as test liquid, indicate significantly better wetting after silicon sputtering for Ti–6AL–4V adherends.