EP0561179A2 - Legierung für eine Gasturbinenschaufel - Google Patents

Legierung für eine Gasturbinenschaufel Download PDF

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Publication number
EP0561179A2
EP0561179A2 EP93102779A EP93102779A EP0561179A2 EP 0561179 A2 EP0561179 A2 EP 0561179A2 EP 93102779 A EP93102779 A EP 93102779A EP 93102779 A EP93102779 A EP 93102779A EP 0561179 A2 EP0561179 A2 EP 0561179A2
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EP
European Patent Office
Prior art keywords
alloy
gamma prime
titanium
aluminum
nickel
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93102779A
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English (en)
French (fr)
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EP0561179A3 (en
Inventor
Sastry Cheruvu Narayana
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CBS Corp
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Westinghouse Electric Corp
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Publication date
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Publication of EP0561179A2 publication Critical patent/EP0561179A2/de
Publication of EP0561179A3 publication Critical patent/EP0561179A3/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
    • C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium

Definitions

  • the current invention relates to an alloy suitable for use in making gas turbine components, such as the rotating blades in the turbine section of a gas turbine. More specifically, the current invention concerns a nickel-based alloy having a sufficiently high chromium content for good corrosion resistance yet maintaining high strength when used to make a directionally solidified turbine blade casting.
  • a gas turbine employs a plurality of rotating blades in its turbine section. Such blades are exposed to gas at temperatures in excess of 1100°C (2000°F) and subjected to high stress. Consequently, the alloys from which such blades are cast must, after suitable heat treatment, have very high stress rupture strength and sufficient metallurgical stability to maintain this strength for many thousands of hours of operation. Such alloys must also have sufficient ductility to withstand the large thermal stresses imposed on turbine blades. In addition, as a result of impurities in the fuel and combustion air, the gases to which the blades are exposed contain corrosive compounds, such as sulfides and chlorides. Consequently, such blade alloys must also have good high temperature corrosion resistance, as well as oxidation resistance.
  • high temperature corrosion resistance is provided by the incorporation of substantial amounts of chromium into turbine blade alloys.
  • High chromium content inhibits the basic fluxing of the alloy by forming a continuous chromia scale that is not susceptible to solution and reprecipitation from a Na2SO4 melt, thereby providing an effective barrier for the alloy.
  • chromium combines with sulfur to form high melting point sulfides, thereby inhibiting degradation due to sulfidation.
  • a minimum level of 15% chromium is considered necessary for good high temperature corrosion resistance.
  • One nickel-based alloy used with some success for a number of years in gas turbine blades, is manufactured by the International Nickel Company and known commercially as IN-738.
  • the manufacturer recommends that the electron vacancy number for this alloy not exceed 2.36.
  • This alloy is disclosed in U.S Patent No. 3,459,545 (Bleber), hereby incorporated by reference in its entirety.
  • Figure 1 shows a graph of time to rupture versus stress at three temperature levels for both conventionally cast -- that is, having an equiaxed grain structure -- and directionally solidified IN-738 test specimens.
  • data at both the 870°C (1600°F) and 925°C (1700°F) temperature levels indicates that the rupture life of the directionally solidified specimens is worse than that of the conventionally cast specimen above a stress level of about 275 N/mm2 (40 KSI).
  • one popular alloy used in directionally solidified blades known commercially as GTD-111, has a typical composition in weight percent of Chromium 14.0, Cobalt 9.5, Aluminum 3, Titanium 4.9, Tantalum 2.8, Tungsten 3.8, Molybdenum 1.5, Boron 0.01, Carbon 0.1 and the balance Nickel, as disclosed by R. Viswanathan in "Damage Mechanisms and Life Assessment of High-Temperature Components," published by the American Society of Metals (1989).
  • the benefits of directional solidification have been obtained by reducing the 16% chromium level used in IN-738 to only 14%. Unfortunately, as previously discussed, such relatively low levels of chromium result in inadequate corrosion resistance.
  • the present invention resides in a nickel-based alloy for a gas turbine blade, comprising the following elements in weight percent: Chromium 14.75 to 16.0 Cobalt 8.0 to 8.5 Aluminum 3.4 to 4.0 Titanium 3.4 to 4.3 Aluminum plus Titanium 7.7 to 8.3 Tantalum 1.75 to 2.7 Tungsten 2.0 to 4.0 Carbon .05 to .12 Nickel Balance.
  • FIG. 2 a rotating blade 1 used in the turbine section of a gas turbine.
  • the current invention is directed to an alloy, referred to as OM 200, from which such blades may be cast, especially using a directional solidification casting process.
  • the current invention is directed to an alloy comprising the following elements in weight percent: Chromium 14.75 to 16.0, Cobalt 8.0 to 8.5, Aluminum 3.4 to 4.0, Titanium 3.4 to 4.3, Aluminum plus Titanium 7.7 to 8.3, Tantalum 1.75 to 2.7, Tungsten 2.0 to 4.0, Carbon .05 to .12, Columbium up to .5, Molybdenum up to 2.0, and the balance Nickel.
  • the alloy of the current invention may also comprise impurities and incidental elements generally associated with nickel-based alloys, such as Zirconium up to .06 and Boron up to .015 percent by weight.
  • the alloy of the current invention consists essentially of the following elements in weight percent: Chromium about 15.5, Cobalt about 8.0, Aluminum about 4.0, Titanium about 3.8, Aluminum plus Titanium about 7.8, Tantalum about 2.7, Tungsten about 2.6, Molybdenum 0.5, Carbon about 0.08 and the balance Nickel.
  • Corrosion resistance in nickel-based alloys is provided primarily by chromium.
  • Nickel-based alloys used for gas turbine components are strengthened by three mechanisms --(i) solid solution strengthening, (ii) strengthening resulting from the presence of carbides and (iii) gamma prime strengthening.
  • Solid solution strengthening is provided by molybdenum, chromium and tungsten and, to a lesser extent, by cobalt, iron and vanadium.
  • Gamma prime strengthening is provided primarily by aluminum and titanium, which strengthen the austenitic matrix through the precipitation of Ni3(Al and/or Ti), an fcc intermetallic compound.
  • the aluminum in gamma prime can be replaced by tantalum and columbium.
  • the amount of gamma prime in an alloy can be determined as discussed below with respect to the determination of the electron vacancy number N v .
  • the amount of gamma prime, in weight percent, in four heats of the alloy according to the current invention shown in Table I are approximately 52, 54, 56 and 54, respectively.
  • the aforementioned preferred composition of the alloy according to the current invention has approximately 56% gamma prime.
  • the amount of gamma prime in IN-738 is approximately 50% by weight. (It should be noted that the aforementioned variation in the gamma prime content among the four heats of the alloy according to the current invention did not adversely affect corrosion resistance or stability.)
  • nickel-based alloys undergo microstructural changes.
  • Such changes include gamma prime coarsening, which adversely affects the strength of the alloy, and the transformation of gamma prime into unwanted topologically close-packed secondary phases, such as plate or needle-like sigma, eta, etc.
  • the formation of these plate-like phases adversely affects both strength and toughness. Consequently, in order to ensure that high strength and toughness are maintained for many thousands of hours of operation at elevated temperature, the composition of the strengthening elements must be carefully balanced, as explained below, so that the alloy has a certain degree of microstructural stability.
  • the atomic percent of each element in the matrix to be substituted into this equation is determined by converting the composition from weight percent to atomic percent and assuming that (i) one-half the carbon forms MC in the order of TaC, CbC, TiC, (ii) the remaining carbon forms M23C6 with the M comprising twenty three atoms of Cr, (iii) boron is combined as Mo3B2, (iii) gamma prime is Ni3(Al, Ti, Ta, Cb), and (iv) the residual matrix consists of the atomic percent minus those atoms contained in the carbides, the boride and the gamma prime reaction so that the total of the remaining atomic percentages gives the atomic concentration in the matrix.
  • the composition is adjusted so that, in addition to obtaining high strength, the electron vacancy number of the alloy does not exceed about 2.4. In the preferred composition of the alloy the electron vacancy number is equal to about 2.4.
  • the aluminum in gamma prime can be replaced by columbium and/or tantalum, as well as titanium.
  • the stability of these compounds in order of decreasing stability is Ni3Al, Ni3Ti and Ni3Cb(orTa).
  • the titanium/aluminum ratio plays a major role in gamma prime coarsening.
  • the titanium/aluminum ratio also plays a major role in the transformation of gamma prime into the aforementioned unwanted plate-like phases.
  • the titanium/aluminum ratio is generally maintained below 2:1 (by weight).
  • the transformation of gamma prime into unwanted needle or plate-like phases can also be retarded by the addition of tungsten.
  • the amounts of aluminum, titanium, tantalum, columbium and molybdenum have been balanced so as to attain high strength when the alloy is directionally solidified while maintaining good microstructural stability.
  • this result has been achieved without the need to reduce the chromium content, and, therefore, without impairing corrosion resistance, as had heretofore been thought necessary by those skilled in the art.
  • the content of aluminum and titanium has been increased, when compared with IN-738, to a minimum of 3.4% for each, with the minimum combined aluminum plus titanium content being 7.7%.
  • the maximum amounts of aluminum and titanium are 4.0% and 4.3%, respectively, with the maximum aluminum plus titanium content being 8.3%.
  • the amounts of columbium and molybdenum have been reduced so that the optimum composition includes no columbium and only 0.5% molybdenum. At most only 0.5% columbium and 2.0% molybdenum are permitted in the alloy of the current invention. Chromium, however, has been maintained in the range of 14.75% to 16%, so that adequate corrosion resistance is maintained. Tungsten is maintained in the range of 2.0% to 4.0% and tantalum in the range of 1.75% to 2.7%. Zirconium and boron are limited to 0.06% and 0.015%, respectively, with none of either of these elements being present in the most preferred composition. Carbon is maintained in the 0.05% to 0.12% range. Moreover, as previously discussed, in the alloy according to the current invention, the elements are adjusted within the aforementioned ranges so that the electron vacancy number is maintained at no more than about 2.4, thereby ensuring that adequate microstructural stability is achieved.
  • the strength of the alloy according to the current invention when cast by a directional solidification process is high, despite its relatively high chromium content.
  • good microstructural stability of the alloy according to the current invention has been achieved by considerably reducing the levels of columbium and molybdenum, when compared to IN-738, so that the amounts of aluminum and titanium can be increased without driving the electron vacancy number too high.
  • IN-6203 is a nickel-based alloy having a nominal composition in weight percent of Chromium 22.0, Cobalt 19.0, Aluminum 2.3, Titanium 3.5, Tantalum 1.10, Columbium 0.80: Tungsten 2.00, Boron 0.01, Carbon 0.15, Zirconium 0.10, Hafnium 0.75 and the balance Nickel.
  • Turbine blades cast from the alloy of the current invention are advantageously made by vacuum-induction melting and vacuum casting using a directional solidification process.
  • Directional solidification causes the grain boundaries to be oriented substantially parallel to the principal stress axis of the blade with almost no grain boundaries oriented normal to the principal stress axis.
  • Techniques for directional solidification are well known in the art -- see, for example, U.S. Patent Nos. 3,260,505 (Ver Snyder), 3,494,709 (Piearcey) and 3,897,815 (Smashey), hereby incorporated by reference in their entirety.
  • the gamma prime distribution depends on heat treatment, as well as composition.
  • the standard heat treatment for nickel-based alloys such as IN-738 -- i.e., a solution treatment followed by an aging treatment -- produces duplex gamma prime comprised of coarse, cuboidal primary gamma prime and fine, spherical gamma prime in approximately equal amounts.
  • the coarse gamma prime is undesolved gamma prime that did not go into solution during the solution treatment.
  • the amount of coarse gamma prime present in the alloy depends on the degree by which the solution temperature is below the gamma prime solvus temperature, at which all of the gamma prime goes into solution -- that is, the lower the solution temperature, the greater the amount of coarse gamma prime.
  • the fine gamma prime forms during the aging treatment, the amount depending on the amount of gamma prime that did not go into solution during solution treatment.
  • the solvus temperature should be considerably below the incipient melting temperature.
  • aluminum, titanium, tantalum and columbium increase the gamma prime volume fraction, and therefore, strength, as previously discussed, they also have the effect of raising the solvus temperature and decreasing the incipient melting temperature, thereby narrowing the heat treatment window.
  • the gamma prime solvus and incipient melting temperatures for three melts of the alloy according to the current invention are shown in Table VI. These temperatures were determined using the differential thermal analysis and gradient bar -- i.e., metallography -- method, in which the bar was exposed to various temperatures in the 1066°C (1950°F) to 1427°C (2300°F) temperature range for four hours and then fan cooled. As can be seen, the solvus temperature varies from 1211°C to 1229°C. By comparison, the solvus temperature for IN-738 is approximately 1204°C (2200°F).
  • the as-cast blades may be heat treated in any of four ways -- (i) solution treating for 2 hours at 1121°C (2050°F), followed by aging for 24 hours at 843°C (1550°F), (ii) solution treating for 4 hours at 1149°C (2100°F), followed by aging for 24 hours at 843°C (1550°F), (iii) solution treating for 4 hours at 1204°C (2200°F), resolution treating for 2 hours at 1121°C (2050°F), followed by aging for 24 hours at 843°C (1550°F), and (iv) solution treating for 4 hours at 1204°C (2200°F), resolution treating for 4 hours at 1149°C (2100°F), followed by aging for 24 hours at 843°C (1550°F).

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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)
EP19930102779 1992-03-18 1993-02-23 Gas turbine blade alloy Withdrawn EP0561179A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US85414292A 1992-03-18 1992-03-18
US854142 1992-03-18

Publications (2)

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EP0561179A2 true EP0561179A2 (de) 1993-09-22
EP0561179A3 EP0561179A3 (en) 1993-11-10

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EP19930102779 Withdrawn EP0561179A3 (en) 1992-03-18 1993-02-23 Gas turbine blade alloy

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EP (1) EP0561179A3 (de)
JP (1) JPH0617171A (de)
KR (1) KR930019844A (de)
CN (1) CN1076508A (de)
AU (1) AU3380093A (de)
CA (1) CA2091827A1 (de)
MX (1) MX9301280A (de)
TW (1) TW222017B (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0709477A1 (de) * 1994-10-31 1996-05-01 Mitsubishi Steel Mfg. Co., Ltd. Schweissbare und hitzebeständige Legierung auf Nickelbasis
US5882586A (en) * 1994-10-31 1999-03-16 Mitsubishi Steel Mfg. Co., Ltd. Heat-resistant nickel-based alloy excellent in weldability
EP2805784A1 (de) * 2013-05-24 2014-11-26 Rolls-Royce plc Nickellegierung
US10227678B2 (en) 2011-06-09 2019-03-12 General Electric Company Cobalt-nickel base alloy and method of making an article therefrom
US11193187B2 (en) 2009-08-20 2021-12-07 Aubert & Duval Nickel-based superalloy and parts made from said superalloy
US12024758B2 (en) 2009-08-20 2024-07-02 Aubert & Duval Nickel-based superalloy and parts made from said superalloy

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10266926B2 (en) 2013-04-23 2019-04-23 General Electric Company Cast nickel-base alloys including iron
WO2018148110A1 (en) * 2017-02-08 2018-08-16 Borgwarner Inc. New alloys for turbocharger components

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3459545A (en) * 1967-02-20 1969-08-05 Int Nickel Co Cast nickel-base alloy
GB2024858A (en) * 1978-07-06 1980-01-16 Inco Europ Ltd Hightemperature nickel-base alloys
GB1572320A (en) * 1977-05-03 1980-07-30 United Technologies Corp Gas turbine blade tip alloy
EP0387976A2 (de) * 1989-03-15 1990-09-19 Institute Of Metal Research Academia Sinica Superlegierungen und Verfahren zur Verbesserung der Eigenschaften von Superlegierungen

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3459545A (en) * 1967-02-20 1969-08-05 Int Nickel Co Cast nickel-base alloy
GB1572320A (en) * 1977-05-03 1980-07-30 United Technologies Corp Gas turbine blade tip alloy
GB2024858A (en) * 1978-07-06 1980-01-16 Inco Europ Ltd Hightemperature nickel-base alloys
EP0387976A2 (de) * 1989-03-15 1990-09-19 Institute Of Metal Research Academia Sinica Superlegierungen und Verfahren zur Verbesserung der Eigenschaften von Superlegierungen

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0709477A1 (de) * 1994-10-31 1996-05-01 Mitsubishi Steel Mfg. Co., Ltd. Schweissbare und hitzebeständige Legierung auf Nickelbasis
US5882586A (en) * 1994-10-31 1999-03-16 Mitsubishi Steel Mfg. Co., Ltd. Heat-resistant nickel-based alloy excellent in weldability
US11193187B2 (en) 2009-08-20 2021-12-07 Aubert & Duval Nickel-based superalloy and parts made from said superalloy
US12024758B2 (en) 2009-08-20 2024-07-02 Aubert & Duval Nickel-based superalloy and parts made from said superalloy
US10227678B2 (en) 2011-06-09 2019-03-12 General Electric Company Cobalt-nickel base alloy and method of making an article therefrom
EP2805784A1 (de) * 2013-05-24 2014-11-26 Rolls-Royce plc Nickellegierung

Also Published As

Publication number Publication date
CN1076508A (zh) 1993-09-22
JPH0617171A (ja) 1994-01-25
CA2091827A1 (en) 1993-09-19
KR930019844A (ko) 1993-10-19
AU3380093A (en) 1993-09-23
EP0561179A3 (en) 1993-11-10
TW222017B (de) 1994-04-01
MX9301280A (es) 1993-09-01

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