Development of a High Integrity Interlayer Joining Technology for High Temperature Aerospace Applications

The purpose of this PhD project was the continual development of the powder interlayer bonding technique for high temperature alloys, more specifically Ti-6Al-2Sn-4Zr-6Mo. The application of this technology is for the potential use as a joining and repair technology on BLISKs. The requirement of extended life cycles for aerospace components such as this is important for the viability of technologies which aim to further improve efficiency within the gas turbine engine. The principle of interlayer bonding is on the utilisation of powder based interlayer which is used to improve bond integrity between two surfaces.Research during this thesis programme has resulted in the development of an interlayer bonding technique that allows for the evaluation of using an inert gas environment, instead of traditional vacuum systems, with a focus on how this technology would eventually be implemented on more complex geometries. The use of argon shielding gas provided the required environment to limit the oxidation of titanium at elevated temperature required for bonding. The results allowed for the mechanical performance of the interlayer bonds to be evaluated, along with the effects of using a post bond heat anneal, with the properties of interlayer bonded Ti-6246 showing only a slight reduction in room temperature properties in comparison to the base material.Preliminary research was also conducted on evaluating the possibility of joining dissimilar titanium alloys, with a focus on Ti-6246 and Ti-6242. With the right balance of the key bonding parameters it was possible to create low porosity bonds between the alloy systems with the tensile results again showing a small debit in strength.The final stages of the programme focused on the potential use of alternate interlayers, including different morphology of alloyed titanium powder as well as Commercially Pure powder and foil with potentially further avenues of research available to investigate.