Applications of Gamma TiAl Intermetallics in Gas Turbine Engines
Speaker: Dr. Gopal Das, Pratt and Whitney Aircraft Engines
Series: Other Events
Location: J223 Equad
Date/Time: Friday, November 18, 2011, 12:00 p.m. - 1:00 p.m.
The light-weight gamma TiAl alloys have significant potential for use in gas turbine engines, land-based power generators and automobile industries. However, their advantageous low density, high-specific strength and stiffness, and burn resistance are offset by low ductility and fracture toughness. Recently, a new beta- stabilized gamma TiAl alloy, TNM, is undergoing critical evaluation for applications such as low pressure turbine (LPT) blades to replace ~ twice- heavier superalloys for advanced gas turbine engines. The TNM alloy solidifies via the beta-phase yielding a fine grained cast microstructure that consisting of lamellar (ï?§ +ï?¡2)-colonies and equiaxed ï?§ and ï?¢/B2 grains with low segregation and minor texture. The cast microstructure can be broken down by extrusion/and /or forging, followed by heat treatments to produce microstructures ranging from a duplex microstructure consisting of ï?§ï phase and lamellar (ï?§ +ï?¡2)-colonies to a fully lamellar (ï?§ +ï?¡2) microstructure. For LPT blades, the root area is exposed to lower temperature and requires high strength, ductility and fatigue strength while the airfoil area experiences higher temperature, where creep resistance is of critical importance. With controlled heat treatment of the wrought gamma TNM alloy, an optimized microstructure can be developed to satisfy the requirement of strength, ductility, and creep for LPT blade application. In this review, casting -related issues, cooling rates on microstructure, deformation mechanisms, environmental effects on gamma TiAl, joining, machining, repair of gamma TiAl, and NDE inspection will also be presented.