Titanium and titanium alloys have an outstanding combination of strength-to-weight ratio and corrosion resistance. Thus, they are frequently the material of choice for the aerospace and biomedical industries. However, applications such as electrical housing and feed-throughs are limited by the difficulty in producing suitable glass-to-metal seals (in terms of strength, hermiticity and humidity resistance). For example, conventional silicate sealing glasses are readily reduced by titanium to form deleterious titanium silicides along the interface. These phases are incompatible with the production of a robust glass-to-metal seal. Investigation into boroaluminate glasses have shown they are capable of overcoming these issues, whilst forming the desired hermetic seal. In this work a range of borate based glasses have been examined as candidate compositions for a sealing system comprising a Ti-6Al-4V alloy housing and a single pin of an appropriate alloy (Alloy 52, Alloy 48 or Kovar). A number of glass compositions were identified and characterised using dilatometry, DTA/DSC, XRD and electron microscopy. Optimised sealing procedures were then established and the bonds assessed as a function of hermiticity and microstructure.
