Titanium alloys and titanium aluminides are being considered as key materials for the manufacture of lightweight compressors and turbines in modern aircraft and rocket engines. The joining technology that provides reliable work above 500 deg C is needed to fabricate functional turbine components. Only then, the full high-temperature strength capabilities of TiAl alloys and titanium matrix composites can be exploited. Two filler metals were tested for brazing heat-resistant joints at 1180-1200 deg C: TiBraze1200 (Ni-27Ti-10AI) and TiBraze375 (Ti-37.5Zr-15Cu-10Ni) in the form of transfer tape. Microstructure and shear strength of the brazed joints were studied at 540-800 C deg. Brazing at the temperature substantially above the liquidus of the filler metals resulted in a noticeable gain of both the high temperature and room temperature strengths. Joints of hot-pressed titanium aluminide brazed by Ti-37.5Zr-15Cu-10Ni filler metal exhibited shear strength at 800 deg C as high as 41.6-47.3 ksi (287-326 MPa) and 63-68 ksi (435-469 MPa) at 650 deg C. Some other methods for improving hot strength of titanium-based alloys are also discussed, particularly: (a) application of composite filler metals and (b) pre-coating of surfaces to be brazed to prevent early oxidation and promote wetting.
Heat-resistant brazing filler metals for joining titanium aluminide and titanium alloys
2006
6 Seiten, 5 Bilder, 2 Tabellen, 5 Quellen
Aufsatz (Konferenz)
Englisch
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