Titanium group powder metallurgy

Abstract

Methods and compositions relating to powder metallurgy in which an amorphous-titanium-based metal glass alloy is compressed above its glass transition temperature Tg with a titanium alloy powder which is a solid at the compression temperature, to produce a compact with a relative density of at least 98%.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of the filing date of U.S. Provisional Application No. 60 / 493,176 filed Aug. 7, 2003.FIELD OF THE INVENTION [0002] The present invention is directed to powder metallurgy, and more particularly, to high performance powder metallurgy for titanium group metal alloys. BACKGROUND OF THE INVENTION [0003] Titanium, zirconium and hafnium (Titanium Group) alloys have high utility, but are relatively difficult to fabricate because of their susceptibility to oxidation and reaction with other materials at their high melting and forging temperatures. [0004] Because of its relatively high temperature capability and high strength to weight ratio, titanium and its alloys are desirable for a variety of aerospace, industrial, marine, military and commercial applications where weight and / or high temperature performance are important, such as fan blades, compressor blades, discs, hubs and other components of turbine engin...

AI Technical Summary

Benefits of technology

[0013] In accordance with such methods, a relatively small amount of an amorphous metal alloy powder having a glass transition temperature at a temperature Tg and supercooled liquid state at a temperature at or above its glass transition temperature, is blended with or coated on a major amount of a titanium group metal alloy powder. The powder blend is compressed at a temperature substantially below the melting point and within the supercooled liquid range of the amorphous alloy, to decrease the porosity of the blend and increase the total surface area of the amorphous powder. In this regard, the porosity of the mixture is preferably decreased to less than about 3 volume percent by compaction or other compression. When using an independent BMG amorphous metal powder (e.g., not a uniform amorphous metal glass coating on crystalline metal particles, the surface area of the amorphous metal alloy is preferably increased by at least 50 percent, and more preferably at least 100 percent during the compression step. The blend may also contain reinforcing powders or fibers such as B, C, Al2O3, SiC, SiCN, TiC powders, filaments or fibers, which will be incorporated in the finished PM products. Desirably, the titanium group powders and amorphous metal powders should have a particle size of less than about 300 microns, preferably with a range of particle sizes to facilitate packing. For some blends, it is desirable that the mean particle size of the amorphous metal component be less than half that of the titanium group metal particles, to facilitate more uniform dispersion in the interstices of the titanium group particles. The titanium group and amorphous powder components may, respectively, be produced in any suitable manner, such as by inert gas atomization, or centrifugal atomization of a molten metal stream, mechanical grinding or milling, chemical reaction, precipitation from the vapor phase, and / or electrolytic or electrodes deposition aqueous from or non-aqueous electrolytes.

[0060] As indicated, titanium and its alloys are used as the matrix component in high performance metal-matrix composites (MMCs) for gas turbine engine components, including fan blades, fan frames, actuators, rotors, vanes, cases, ducting, shafts, and liners. Titanium-based metal matrix composites are important structural materials which are strong, temperature resistant, and relatively stiff for their relatively light weight.

Problems solved by technology

Titanium, zirconium and hafnium (Titanium Group) alloys have high utility, but are relatively difficult to fabricate because of their susceptibility to oxidation and reaction with other materials at their high melting and forging temperatures.

Powder metallurgy techniques include relatively simple procedures such as uniaxial powder compression in a mold followed by sintering at an elevated temperature somewhat below the melting point of the metal powder, as well as more complicated and expensive techniques such as hot isostatic pressing (HIPing) and metal injection molding (MIM).

However, it is difficult to economically eliminate porosity and achieve full density using strong titanium group metals, because their relatively high temperature performance and high yield strength, which are desirable in the final products, make compaction difficult during manufacture.

However, the finished, sintered parts retain considerable porosity, and carbide components from the thermoplastic binder.

Intermetallic compounds have a variety of attractive properties for high-temperature use, but have limited room-temperature ductility.

Unfortunately, properties of consolidated powders may be affected by the conventional compaction methods such as hot-pressing because the prolonged heating can lead to coarsening of the microstructure.

However, properties of consolidated metal alloy powders may also be adversely affected because prolonged and / or high-temperature heating may lead to coarsening of the microstructure, and / or undesired reaction with reinforcing fibers or filaments.

Images