Alloys or metallic compositions – Titanium base – Aluminum containing
Patent
1990-02-25
1993-02-02
Roy, Upendra
Alloys or metallic compositions
Titanium base
Aluminum containing
148421, 420417, 420418, C22C 1400
Patent
active
051836351
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to titanium alloys based on or containing the ordered intermetallic compound Ti.sub.3 Al and having properties suitable for utilization in high temperature applications. The invention is particularly, though not exclusively, directed to materials for use as components in the compressor section of gas turbine engines.
Titanium based alloys have enjoyed significant usage as compressor section materials because of their strength to weight advantage over alternative materials such as steels. However existing commercial titanium alloys of the conventional titanium base type have limited temperature tolerance in terms of resistance to creep and resistance to oxidation. These limitations restrict the application of the established titanium alloys to the lower pressure stages of the compressor where components are not subjected to temperatures significantly above 540.degree. C. In the higher pressure stages of the compressor more refractory materials such as iron or nickel based superalloys are used despite the weight penalty they impose. There is a commercial drive towards the `all-titanium` compressor in order to save weight by elimination of iron or nickel based superalloy components. There is also a drive to increase the compressor pressure ratio in order to improve overall engine efficiency and this would impose an increased temperature burden on compressor section components.
DISCUSSION OF THE PRIOR ART
The established titanium alloys are based on a matrix consisting of one or the other, or a mixture of the two, of those phases found in pure titanium. These phases are the .alpha. phase which is the lower temperature phase end of hexagonal close-packed (hcp) structure and the .beta. phase which is of body centred cubic (bcc) structure. The .beta. phase is stable from the transus temperature of 882.degree. C. up to the melting point. Alloying additions change the temperature at which the .alpha. to .beta. transition occurs. Some elements lower the .beta. transus temperature and these are termed .beta. stabilizers. Others which raise the .beta. transus temperature are termed .alpha. stabilizers. The alloys are usually catergorised having regard to their predominant microstructure at room temperature and to the nature and proportions of the alloying ingredients, into the following groups: .alpha.-type alloys; .beta.-type alloys and .alpha.+.beta. type alloys. The .alpha. group also includes those alloys termed near-.alpha. alloys.
A digression is made here to explain that the atomic percent system is used in the main in this document in defining and describing the invention, compositions given in these terms being designated "at %". In commercial practice it is conventional to specify compositions in the weight percent system and that system is retained here when making reference to prior art alloys specified by weight in the source document. Compositions specified by weight are designated "wt %".
IMI 829 is a commercial alloy which is representative of the best of established gas turbine engine titanium alloys in terms of creep strength and oxidation resistance in regard to high temperature properties (IMI 829 is a trade designation of IMI Titanium). This near-.alpha. alloy has a nominal composition Ti-5.5Al-3.5Sn-3Zr-1Nb-0.25Mo-0.3Si (at %). The properties of this alloy are used as one baseline for comparison at various points in this specification. It is limited by high temperature oxidation and its deleterious effect on fatigue properties to applications not requiring exposure to temperatures of 550.degree. C. and above.
One of the alloying elements used in the established titanium-base alloys is aluminium, which is an .alpha. stabilizer. If aluminium is added to titanium in suitable proportion on ordered intermetallic compound Ti.sub.3 Al is formed. This is designated the .alpha..sub.2 phase and it has a ordered hcp structure. In the established alloys the aluminium content is restricted by reference to an empirical rule to a level beneath that at which
REFERENCES:
patent: 3411901 (1968-11-01), Winter
patent: 4292077 (1981-09-01), Blackburn et al.
patent: 4746374 (1988-05-01), Froes et al.
patent: 4788035 (1988-11-01), Gigliotti, Jr. et al.
Kerry Stephen
Restall, deceased James E.
Wood Michael I.
Roy Upendra
The Secretary of State for Defence in Her Britannic Majesty's Go
LandOfFree
Heat treatable Ti-Al-Nb-Si alloy for gas turbine engine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heat treatable Ti-Al-Nb-Si alloy for gas turbine engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heat treatable Ti-Al-Nb-Si alloy for gas turbine engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-5956