Turbine engines are used as the primary power source for various kinds of aircraft and other vehicles. The engines may also serve as auxiliary power sources that drive air compressors, hydraulic pumps, and industrial electrical power generators. Most turbine engines generally follow the same basic power generation procedure. Compressed air is mixed with fuel and burned, and the expanding hot combustion gases are directed against stationary turbine vanes in the engine. The vanes turn the high velocity gas flow partially sideways to impinge onto turbine blades mounted on a rotatable turbine disk. The force of the impinging gas causes the turbine disk to spin at high speed. Jet propulsion engines use the power created by the rotating turbine disk to draw more air into the engine, and the high velocity combustion gas is passed out of the gas turbine aft end to create forward thrust. Other engines use this power to turn one or more propellers, electrical generators, or other devices. Because fuel efficiency increases as engine operating temperatures increase, turbine engine blades and vanes are typically fabricated from high-temperature materials, such a high-temperature metal alloys.
Conventional high-temperature alloys are strengthened mainly by solid solution and precipitation mechanisms that hinder dislocation movement. As the desired service temperatures become increasingly higher and the service life becomes significantly longer, these alloys can eventually lose their strength as the precipitates become dissolved or coarsened, and the solid solute atoms become highly diffusive due to the greatly increased thermal agitation. Oxide dispersion strengthened (ODS) alloys, on the other hand, derive their high temperature strength mainly from a fine dispersion of oxides that are nearly insoluble in the matrix. This insolubility enables the oxide particles to hinder dislocation movements and thus retain strength up to temperatures near the matrix melting point. Furthermore, unlike precipitation strengthening, which requires high solubility of solute atoms at high temperatures and vice versa, the ODS mechanism is free from this temperature solubility requirement. ODS alloys are not produced by traditional melt metallurgy liquid metal exposures since the ODS particles will dissolve in a liquid metal state.
Such ODS alloys are currently produced by the mechanical alloying process, as illustrated in FIG. 1. Powders of oxide, elemental metals, and alloys are mixed in a high-energy ball mill to form composite powders with the dispersoid. Ingots are then obtained by hot extrusion. Alloys produced in this fashion, i.e. ODS alloys, have typically been used to produce directional property structures such as turbine blades and sheet materials for static structures. Unfortunately, it is very difficult to ball mill a highly alloyed material, containing a significant gamma prime volume fraction which is strong. Further, the material may itself become contaminated from the ball mill and ultimately compromise component integrity. In addition, the powder that is produced requires subsequent hot compaction or working to produce an acceptable microstructure and consistent mechanical properties.
Accordingly, it is desirable to provide improved methods for forming oxide dispersion-strengthened alloys. Further, it is desirable to provide such methods that do not require mechanical alloying. Furthermore, other desirable features and characteristics of the invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.