Transient Liquid Phase Bonding of Single Crystal Ni3Al-Based Intermetallic Alloy

Conventional heat-resistant structural materials such as nickel-based superalloys that are used in aircraft and power generation gas turbines have nearly reached their upper temperature limit of application and, as such, research has been focused on alternative materials that are lighter and stronger, and have a higher temperature capability than the superalloys. Intermetallic-based alloys, such as, nickel aluminides, have evolved as prime alternate materials in this regard, and have been the subject of intense study for the past few decades. Their application, however, is contingent on the development of appropriate joining techniques, which is crucial to their cost-effective application in the fabrication and repair of service-damaged components In the present work, a study was performed on transient liquid phase (TLP) bonding of a single crystal (SX) Ni₃Al-based intermetallic alloy designed and successfully tested as aircraft engine material but extremely difficult to weld by conventional welding techniques. The influence of process parameters on the microstructure of TLP joint in the material, including a successful use of composite powder mixture of a brazing alloy and a gap-filler alloy as the interlayer material, aimed at reducing substrate erosion but which has been generally reported to be unsuitable for SX materials, will be presented and discussed.