TWI Industrial Member Report Summary 536/1995
P L Threadgill
Ordered intermetallic alloys have generated considerable interest in many industrial sectors, due to their good mechanical properties at high temperatures, good oxidation/corrosion resistance, and low density. Progress in developing alloys with improved properties continues at a rapid pace, and with it the need to develop appropriate joining techniques.
Alloys based on TiAl are of very great interest to aircraft engine manufacturers, since their use will lead to very significant weight savings. They are also of interest in the automotive industry, for turbo impellers and exhaust valves.
Nickel aluminides based on Ni3A1 have many potential uses in corrosive environments, particularly in the presence of chlorides. They are also being developed for turbo impellers, furnace furniture, and several other niche markets. NiAl has generated much interest as a less dense replacement for nickel superalloys, but further alloy development is required to improve its ductility and high temperature mechanical properties. Iron aluminides are being considered for low density power shafts, and for corrosion resistance in high sulphur environments, for example many furnace and superheater components. Along with nickel aluminides, iron aluminides have a promising future as a coating.
The present work extends TWI's knowledge of joining these alloys, in terms of compatible processes, understanding of microstructures, and determination of properties.
The objectives of the work are as follows:
- Investigate methods of joining additional nickel, iron and titanium based intermetallic alloys
- Evaluate the data in the light of existing knowledge, to further develop understanding of the welding behaviour of these alloys.