US3785809A - Nickel-base superalloy - Google Patents

Nickel-base superalloy Download PDF

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US3785809A
US3785809A US00153444A US3785809DA US3785809A US 3785809 A US3785809 A US 3785809A US 00153444 A US00153444 A US 00153444A US 3785809D A US3785809D A US 3785809DA US 3785809 A US3785809 A US 3785809A
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alloy
nickel
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US00153444A
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A Cox
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RTX Corp
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United Aircraft Corp
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C19/00Alloys based on nickel or cobalt
    • C22C19/03Alloys based on nickel or cobalt based on nickel
    • C22C19/05Alloys based on nickel or cobalt based on nickel with chromium
    • C22C19/051Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
    • C22C19/057Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being less 10%

Definitions

  • the present invention relates in general to the cast, precipitation-hardening nickel-base superalloys and, in particular, to such alloys having application to gas turbine engine blades and vanes.
  • Alloy A has a nominal composition comprising, in percent by weight, chromium, cobalt, 3 molybdenum, 4.5 titanium, 5.5 aluminum, 1 vanadium, 0.17 carbon, 0.015 boron, 0.06 zirconium, balance nickel.
  • the present invention contemplates an alloy comprising, in percent by weight, 9-10 chromium, 9.5l0.5 cobalt, 0-5 molybdenum, 1-5 tungsten, 3.5-5.5 titanium, 3-7 aluminum, 0.5-l.5 vanadium, 0.005-0.025 boron, 0.03-0.l zirconium, 0-0.25 carbon, balance essentially nickel.
  • a particular preferred embodiment hereinafter referred to as FA-375, consists essentially of, in percent by weight, 9-10 chromium, 9.5-l0.5 cobalt, 2-3 molybdenum, 3.5-4 tungsten, 4-4.5 titanium, 5-5.5 aluminum, 0.7-1 .2 vanadium, 0.015-0.025 boron, 0.04-0.08 zirconium, 0-0.20 carbon (0.15-0.20 for polycrystalline fonn), balance essentially nickel.
  • the following maximums are maintained, 0.50 iron, 0.20 manganese, 0.01 phosphorous, 0.01 sulfur and 0.2 silicon.
  • a small amount of hafnium, up to 2.5 weight percent, may optionally be added to the alloy.
  • the alloy is adapted to directional solidification techniques, including those suggested by VerSnyder U.S. Pat. No.
  • the nickel component is used to set the particular crystal lattice, austenite type, or face-centered cubic system from In directional casting and the production of columnar-grain articles, the slow solidification rates associated therewith have revealed, in some instances, evidence of precracked MC-type carbides which may act as failure sites in fatigue. Accordingly, in such processes low carbon contents are preferred.
  • I-Iafnium an expensive rare-earth element, has been shown to provide some improvements in alloy castability and has given evidence of improved creep-rupture ductility.
  • the sigma phase is usually identified as an intermetallic compound of topologically close-packed morphology. It precipitates, often in usage, as hard brittle platelets which form the natural sites in the alloy for mechanical weakness. In alloys of the present type, the susceptibility to sigma phase formation has been found to be directly dependent upon the concentrations in solid solution of chromium,cobalt, iron, molybdenum and the like.
  • the as-cast microstructure of the polycrystalline FA-375 alloy proved typical of the rich nickel-base superalloys, i.e., a high volume percentage of the secondary 7' phase with associated regions of a eutectic 'y-y. Similarly dispersed, though in low volume percent, were carbides of the MC-type. Gross segregation was not evident.
  • the effect of heat treatment on the alloys was pronounced. and, in most respects, followed basic correlations between microstructure and mechanical properties.
  • the preferred heat treatment cycle for the equiaxed grain FA-375 alloy contemplates: solution heat treatment at l,950-2,000F in vacuum of dry TemP- 01% argon or hydrogen for four hours with subsequent cool- 5 RT 120.200 137.600 6.5 m mg at a rate equ1valent to an cool or faster plus precipi- 5 s tation at l,600F i 25.
  • the preferred heat treatment L200 152300 for the columnar grain FA-375 alloy contemplates: so- 1600 105,800 118,500 6.0 9.0
  • Creep and Creep Rupture (Equiaxed Grain) Stress Time RT 137,600 160,100 9.0 13.8 Alloy Temp. F. p.s.i. to 1% hrs. Life, Hrs. 40

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)

Abstract

A cast, precipitation-hardening alloy, applicable to turbine blades and vanes operating in the 1,200*-1,900* F. temperature range, of a nominal composition, by weight, of 9.5 percent chromium, 10 percent cobalt, 2.5 percent molybdenum, 3.7 percent tungsten, 4.2 percent titanium, 5.2 percent aluminum, 1 percent vanadium, 0.015 percent boron, 0.06 percent zirconium, balance nickel. The invention herein described was made in the course of or under a contract with the Department of the Air Force.

Description

[111 3,785,809 1451 Jan. 15, 1974 1 NICKEL-BASE SUPERALLOY [75] Inventor: Arthur R. Cox, Lake Park, Fla.
[73] Assignee: United Aircraft Corporation, East Hartford, Conn.
1 Filed! June 15, 1971 Appl. No.: 153,444
[52] US. Cl. 75/171, 148/325 [51] Int. Cl. .r C22C 19/00 [58] Field of Search 75/171, 170; 148/32, 148/325 [56] References Cited UNITED STATES PATENTS 3,061,426 10/1962 Bieber 75/171 3,642,469 2/1972 Ross et a1. 75/171 3,415,641 12/1968 Ross 75/171 5/1968 MacFarlane et a1 75/171 3,260,505 7/1966 Ver Snyder 75/171 Primary ExaminerRichard 0. Dean Att0rneyRichard N. James [5 7 ABSTRACT A cast, precipitation-hardening alloy, applicable to turbine blades and vanes operating in the l,200-l,900 F. temperature range, of a nominal composition, by weight, of 9.5 percent chromium, 10 percent cobalt, 2.5 percent molybdenum, 3.7 percent tungsten, 4.2 percent titanium, 5.2 percent aluminum, 1 percent vanadium, 0.015 percent boron, 0.06 percent zirconium, balance nickel.
The invention herein described was made in the course of or under a contract with the Department of the Air Force.
2 Claims, No Drawings 1 NICKEL-BASE SUPERALLOY BACKGROUND OF THE INVENTION The present invention relates in general to the cast, precipitation-hardening nickel-base superalloys and, in particular, to such alloys having application to gas turbine engine blades and vanes.
One of the advanced nickel-base superalloys which is utilized in gas turbine engine blading is that described in the patent to Bieber 3,061,426. This alloy, hereinafter identified as Alloy A, has a nominal composition comprising, in percent by weight, chromium, cobalt, 3 molybdenum, 4.5 titanium, 5.5 aluminum, 1 vanadium, 0.17 carbon, 0.015 boron, 0.06 zirconium, balance nickel.
To meet the ever-increasing demands of the engine designer further strength increases in these alloys are required. In particular, increased creep resistance is of fundamental importance. However, despite the knowledge that the addition of patent strengthening elements such as tungsten would possibly impart the desired improvements, it has been found that the above alloy, as constituted. could not be enriched in such elements because the composition would be forced into sigma formation and a consequent unacceptable embrittlement.
SUMMARY OF THE INVENTION The present invention contemplates an alloy comprising, in percent by weight, 9-10 chromium, 9.5l0.5 cobalt, 0-5 molybdenum, 1-5 tungsten, 3.5-5.5 titanium, 3-7 aluminum, 0.5-l.5 vanadium, 0.005-0.025 boron, 0.03-0.l zirconium, 0-0.25 carbon, balance essentially nickel.
A particular preferred embodiment, hereinafter referred to as FA-375, consists essentially of, in percent by weight, 9-10 chromium, 9.5-l0.5 cobalt, 2-3 molybdenum, 3.5-4 tungsten, 4-4.5 titanium, 5-5.5 aluminum, 0.7-1 .2 vanadium, 0.015-0.025 boron, 0.04-0.08 zirconium, 0-0.20 carbon (0.15-0.20 for polycrystalline fonn), balance essentially nickel. In addition, the following maximums are maintained, 0.50 iron, 0.20 manganese, 0.01 phosphorous, 0.01 sulfur and 0.2 silicon. A small amount of hafnium, up to 2.5 weight percent, may optionally be added to the alloy.
In addition to polycrystalline castings, the alloy is adapted to directional solidification techniques, including those suggested by VerSnyder U.S. Pat. No.
DESCRIPTION OF THE PREFERRED EMBODIMENTS In alloys of the general type described, the nickel component is used to set the particular crystal lattice, austenite type, or face-centered cubic system from In directional casting and the production of columnar-grain articles, the slow solidification rates associated therewith have revealed, in some instances, evidence of precracked MC-type carbides which may act as failure sites in fatigue. Accordingly, in such processes low carbon contents are preferred. I-Iafnium, an expensive rare-earth element, has been shown to provide some improvements in alloy castability and has given evidence of improved creep-rupture ductility.
The provision of an alloy with improved creep strength is not achieved merely by the addition of known strengthening elements to a given alloy formation. As previously described, Alloy A to commercial specification chemistry has proven intolerant of the addition of further strengthening elements because such enrichment has led to the formation of the detrimental sigma phase.
The sigma phase is usually identified as an intermetallic compound of topologically close-packed morphology. It precipitates, often in usage, as hard brittle platelets which form the natural sites in the alloy for mechanical weakness. In alloys of the present type, the susceptibility to sigma phase formation has been found to be directly dependent upon the concentrations in solid solution of chromium,cobalt, iron, molybdenum and the like.
In the alloy of the present invention, substantial improvements in creep resistance have been obtained without any evidence of sigma phase precipitation. Sigma has not, in fact, been observed after engine operation and exposure of the alloy to 1,040 hours at 1,600F.
A number of alloys were run to a variety of chemistries and varying heat treatments. Each casting was xrayed to determine soundness and freedom from inclusions, and macro-etched for grain size and uniformity. Both polycrystalline and columnar-grained castings were actually engine tested.
The as-cast microstructure of the polycrystalline FA-375 alloy proved typical of the rich nickel-base superalloys, i.e., a high volume percentage of the secondary 7' phase with associated regions of a eutectic 'y-y. Similarly dispersed, though in low volume percent, were carbides of the MC-type. Gross segregation was not evident.
Initial 'y phase solutioning, as observed by electron microscopy was evident at approximately 2,100F. and quite apparent by optical microscopy at 2,150F. Alloy homogenization was readily noticeable as the exposure temperature was raised toward that of melting. Incipient melting and eutectic dissolution began at 2,250F. and no degeneration of the primary carbides was observed for any exposure.
The effect of heat treatment on the alloys was pronounced. and, in most respects, followed basic correlations between microstructure and mechanical properties. Three basic heat treatment cycles were investigated. The first involved partial 'y' solutioning (2,200F/4 hrs.); reprecipitation and 'y' overage (2,000F./4hrs.) and final precipitation (l,600F./12 hrs.). The second involved the first and third cycles of the above, i.e., 2,200F. solutioning and 1,600F. final precipitation. The third utilized only the latter two cycles overaging and final precipitation.
The number three cycle was found to produce optimum levels of strength and ductility for the alloy when cast into random polycrystalline form. The number two cycle was found best when the alloy was directionally solidified. Thus the preferred heat treatment cycle for the equiaxed grain FA-375 alloy contemplates: solution heat treatment at l,950-2,000F in vacuum of dry TemP- 01% argon or hydrogen for four hours with subsequent cool- 5 RT 120.200 137.600 6.5 m mg at a rate equ1valent to an cool or faster plus precipi- 5 s tation at l,600F i 25. The preferred heat treatment L200 152300 for the columnar grain FA-375 alloy contemplates: so- 1600 105,800 118,500 6.0 9.0
o o lut1on heat treatment at 2.175 2,200 F for hours 1n 800 58,600 75,500 To M same env1ronment as above plus prec1p1tat1on at 10 7 I H m a 1,600F i 25.
in testing, no structural change was observed after 890 hours at 1,400F. under a continuously applied ,5 load of 85,000 p.s.i. After 54 hours at 1,800F. and Table m 29,000 p.s.i., the only change is phase coalescence aligning in the direction of applied stress. After 1,040 Tens": Raul (Cmumna' Grain) h o l l d f 11.1. 22001=./4 hrs. l600F./l2 hrs.
ours at 1,000 F. under a continuous y app ted 0a 0 Temp 4 01% UTS' Ni 40,000 p.s.1., only phase coalescence and anmhilatlon of the fine precipitate was observed. Had the alloy been RT 133900 1641600 prone toward sigma formation, this test would have 1300 64,750 79,800 13.7 32.2 provided opportunity for its presence. However, none was detected. W
' Table 1v Creep-Rupture Test Results (Columnar Grain) Stress Time Final Temp. "F. p.8.i. to l%,hrs. Life, hrs. Prior EL,% EL,%
V The results of mechanical te stiiig JWe alToTre a 4 m TablEV WM 7 summarized in the following tables.
Tensile Test Results Table I Columnar Grain, Carbon less than 200 p.p.m.
Temp. F. 0.2% (S UTS, p.s.i. EL,% RA,%
Creep and Creep Rupture (Equiaxed Grain) Stress Time RT 137,600 160,100 9.0 13.8 Alloy Temp. F. p.s.i. to 1% hrs. Life, Hrs. 40
A-375 0 000 74 i A :28 333 $2: 1600 109,600 135,700 12.5 30.2 M375 1600 50,000 133 338 Alloy A 600 49,600 36 so 1800 78,600 89,900 7.5 28.0 FA-375 1700 35,000 82 215 Alloy A 1700 34,300 20 62 2000 37350 491800 FA-375 1800 29,000 17 53 Alloy A 1800 28,400 6 40 FA-375 1800 22,000 255 Alloy A 1800 21,500 42 T able vl W Creep-Rupture Test Results Columnar Grain, Carbon below 200 p.p.m. Stress Time Final Temp. F. p.s.i. to 1%, hrs. Life, hrs. Prior EL,% EL,%
Table II Tensile Test Results (Equiaxed Grain) Iii thersw aiigmsilai summary it will be noted in particular that the creep and creep-rupture strengths of the alloy of the present invention are vastly superior to those of Alloy A. As directionally solidified, the FA-S- 75 alloy is the strongest alloy of this type in its density range. Thus, there has been provided a cast, precipitation hardening nick'elbase superalloy having specific utility in gas turbine engine blades and vanes, and incorporation of such blades and vanes in production hardware is currently in process.
scribed in detail in connection with specific examples and preferred embodiments, the invention in its broader aspects is not limited thereto, but departures may be made therefrom within the scope of the accompanying claims without departure from the principles of the invention and without sacrificing its chief advantages.
' l0 Although the invention has been specifically de- What is claimed is:
long term stability under conditions of high stress at temperatures in excess of l,650F.
2. "rheiiib'y'dr claim 1 wherein: Y the alloy microstructure as cast is characterized by a columnar grained microstructure aligned substantially in the direction of solidification.
* i il

Claims (1)

  1. 2. The alloy of claim 1 wherein: the alloy microstructure as cast is characterized by a columnar grained microstructure aligned substantially in the direction of solidification.
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5972289A (en) * 1998-05-07 1999-10-26 Lockheed Martin Energy Research Corporation High strength, thermally stable, oxidation resistant, nickel-based alloy
US20040229072A1 (en) * 2002-12-16 2004-11-18 Murphy Kenneth S. Nickel base superalloy
US20070077143A1 (en) * 2005-10-04 2007-04-05 General Electric Company Bi-layer tip cap
US20080213099A1 (en) * 2006-08-25 2008-09-04 Shinya Imano Ni-Fe BASED FORGING SUPERALLOY EXCELLENT IN HIGH-TEMPERATURE STRENGTH AND HIGH-TEMPERATURE DUCTILITY, METHOD OF MANUFACTURING THE SAME, AND STEAM TURBINE ROTOR
EP2450126A2 (en) 2010-11-05 2012-05-09 United Technologies Corporation Die casting system and method utilizing high melting temperature materials

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5972289A (en) * 1998-05-07 1999-10-26 Lockheed Martin Energy Research Corporation High strength, thermally stable, oxidation resistant, nickel-based alloy
US20040229072A1 (en) * 2002-12-16 2004-11-18 Murphy Kenneth S. Nickel base superalloy
US20070077143A1 (en) * 2005-10-04 2007-04-05 General Electric Company Bi-layer tip cap
US7556477B2 (en) * 2005-10-04 2009-07-07 General Electric Company Bi-layer tip cap
US20080213099A1 (en) * 2006-08-25 2008-09-04 Shinya Imano Ni-Fe BASED FORGING SUPERALLOY EXCELLENT IN HIGH-TEMPERATURE STRENGTH AND HIGH-TEMPERATURE DUCTILITY, METHOD OF MANUFACTURING THE SAME, AND STEAM TURBINE ROTOR
US8512488B2 (en) * 2006-08-25 2013-08-20 Hitachi, Ltd. Ni—Fe based forging superalloy excellent in high-temperature strength and high-temperature ductility, method of manufacturing the same, and steam turbine rotor
EP2450126A2 (en) 2010-11-05 2012-05-09 United Technologies Corporation Die casting system and method utilizing high melting temperature materials

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