TWI Industrial Member Report Summary 729/2001
L J Ecclestone and D R Ormston
Background
Brazing has been demonstrated as a successful technique for producing ceramic-ceramic and ceramic-metal joints for use at ambient and moderate temperatures.
At higher temperatures, or when joining materials with significant mismatch in coefficient of thermal expansion (CTE), the interfacial stresses developed become higher, and hence the production of high strength joints becomes more problematic.
The increasing use of high temperature superalloys has developed a market need for improved joining methods for high temperature applications. There are, however, only a limited number of commercially available high temperature braze alloys. The joining of dissimilar materials using these alloys is especially problematic due to the likely differences in CTE, and the increased potential for stress development as the filler metal solidifies on cooling at a higher temperature than conventional braze alloys such as Ag-Cu.
The goal of the project is to incorporate particulate reinforcement into braze alloys for both moderate and high temperature service, to investigate the potential benefits of increased joint strength and stress management that such reinforcement could afford.
Objectives
- Develop and measure the strength of ceramic-ceramic joints fabricated with composite braze alloys suitable for moderate temperature service ( ie less than 450°C).
- Develop and measure the strength of ceramic-metal joints fabricated with composite braze alloys suitable for moderate temperature service ( ie less than 450°C).
- Develop and measure the strength of ceramic-ceramic and ceramic-metal joints fabricated with composite brazes suitable for high temperature service ( ie 800-1000°C).