EP0218379B1 - Legierungen auf Nickelbasis für Verwendung bei hohen Temperaturen - Google Patents

Legierungen auf Nickelbasis für Verwendung bei hohen Temperaturen Download PDF

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EP0218379B1
EP0218379B1 EP19860306987 EP86306987A EP0218379B1 EP 0218379 B1 EP0218379 B1 EP 0218379B1 EP 19860306987 EP19860306987 EP 19860306987 EP 86306987 A EP86306987 A EP 86306987A EP 0218379 B1 EP0218379 B1 EP 0218379B1
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Prior art keywords
alloys
alloy
nickel
temperature
properties
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English (en)
French (fr)
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EP0218379A1 (de
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Noel Arthur Burley
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Bell IRH Pty Ltd
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Bell IRH Pty Ltd
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Priority claimed from AU62404/86A external-priority patent/AU581342B2/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
    • C22C19/058—Alloys based on nickel or cobalt based on nickel with chromium without Mo and W
    • 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%

Definitions

  • This invention relates to nickel-based alloys for high-temperature service.
  • the most common alloys conventionally used for the particular application of sheathing materials of metal-sheathed mineral-insulated conductor cables are various grades of stainless steel and inconel. These alloys are significantly deficient in one or more of the properties required for such an application.
  • alloys which have actual or potential application as sheathing for metal-sheathed mineral-insulated cables such as stainless steel, inconel, nicrosil and nisil, are deficient in some or all of the aspects of very high resistance to gas corrosion, ultra-high thermoelectric stability, very high tensile strength and retention of strength at the highest application temperatures involved.
  • the present invention provides a nickel-based alloy consisting of, by weight, 13.5 % to 14.5 % chromium, 1.0 % to 1.5 % silicon, and the balance nickel, apart from impurities, characterized in that it also contains at least one element selected from molybdenum, tungsten, niobium, and tantalum, in concentration by weight molybdenum: up to 5.0 % maximum, tungsten : up to 1.0 % maximum, niobium : up to 3.0 % maximum, and tantalum : up to 2.0 % maximum, and optionally up to 0.5 % magnesium and/or up to 0.2 % cerium.
  • the alloys of the present invention possess a comprehensive range of enhanced properties at high temperatures and are therefore suitable for a wide variety of applications among which may be mentioned structural components of solid form in a variety of sections including tubular sections for furnaces, retorts and other heated enclosures of many kinds, protective sheathing for a number of devices including thermocouples, thermocouple cables, resistive heating elements, heat sensing and heat tracing cables, as well as igniter devices, rocket nozzles and other components for many other applications.
  • a particular application of the alloys of this invention is for the sheathing material of mineral-insulated metal-sheathed electrical conductor cable for thermocouples and other devices including thermocouples where the sheath forms one of the thermoelement conductors of the thermocouple.
  • the alloys of this invention have improved high-temperature properties and are characterized, in particular, by possessing properties including :
  • the alloys of this invention may be used as cast, and in the hot-worked, cold-worked or fully annealed conditions. While these alloys have excellent properties in both the cast and wrought conditions, these properties can be improved and stabilized by annealing treatments at temperatures above their minimum recrystallization temperatures. This stabilization applies particularly to their thermoelectric properties.
  • the alloys of the present invention possess a comprehensive range of these enhanced properties, they are suitable for a wide variety of applications at high temperatures. These applications may occasionally require only one or a combination of the improved properties.
  • the excellent resistance to high-temperature gas corrosion and excellent high-temperature tensile strength of the new alloys are important properties for load bearing structural components in furnaces, retorts, reactor vessels, heated enclosures of many kinds, gas turbine engines, rocket nozzles and a wide range of similar equipment.
  • the ultra-high thermoelectric stability of the new alloys is important for wires and tubes for thermoelement conductors and protective sheathing, respectively, for thermocouples particularly of the metal-sheathed mineral-insulated type of construction.
  • a particular application of the new alloys is in mineral-insulated metal-sheathed conductor cables for thermocouples, heater elements, heat sensing and heat tracing cables, stagnation probe transducers for gas turbine engines, gas flues, and like applications. It is in such applications that the unique combination of excellent properties at high temperature of the alloys of this invention of gas-corrosion resistance, thermoelectric stability and retained high tensile strength are of optimum benefit In some of these applications a combination of the highest possible values of these properties is essential.
  • the alloy microstructure must comprise only one equilibrium phase which is a terminal solid-solution.
  • the base ternary alloy of nickel-chromium-silicon in the concentration ratios described in the preferred embodiments of Table 1, is of such single solid-solution equilibrium structure.
  • the addition of the preferred strengthening elements molybdenum, tungsten, niobium and tantalum does not exceed limits of solid solubility in the ternary Ni-Cr-Si base alloy. Therefore no second phases, either solid- solutions or intermetallic compounds, are formed.
  • the preferred alloys are amenable to both hot and cold mechanical working to change their shape because they possess adequate cold ductility, and that their microstructural recrystallization temperatures are about 800 °C so they can readily be softened by annealing above this temperature when they are work hardened by cold deformation. Furthermore, any property variations across a section of the preferred alloys due to compositional inhomogeneities in as-cast structures can be readily minimized by homogenizing heat- treatments.
  • compositions of the alloys in the present invention require the careful selection of component elements of very high purity and the achievement of the correct proportions of each by adequate control of melting and casting techniques. In all cases the effects of one component element depend on those of the others and hence there is a synergistic interdependence of the elements within the overall compositions. In general, concentrations of alloying elements outside the compositional ranges specified for the alloys of this invention cause degradation of the optimum levels of property values of gas-corrosion resistance, thermoelectric stability and tensile strength, all at high temperatures.
  • Nickel-chromium-silicon alloys of the single solid-solution phase type in the concentration ranges (9 to 15) % wt. Cr and (0.3 to 1.5) % wt. Si show relatively high thermoelectric stability at elevated temperatures in air.
  • the actual degrees of instability of thermoelectromotive force output and Seebeck coefficient are functional not only upon temperature of exposure and the oxygen partial pressure of the air, but also upon the specific solute concentrations of chromium and silicon in the base nickel.
  • the highest degree of stability of thermoelectromotive force is achievable only by selecting optimum critical concentrations of chromium and silicon in nickel.
  • Figure 1 shows the degree of thermoelectric instability exhibited by the most common Ni-Cr-Si alloys used as thermocouple thermoelements, namely the Ni-9.3 % wt. Cr-0.4 % wt.Si alloy designated type KP by the Instrument Society of America. This instability is expressed as drift in thermoelectromotive force in microvolt as a function of time of exposure in air at 1 200 °C.
  • the figure also shows the greatly enhanced thermoelectric stability of the base Ni-Cr-Si alloy which is the preferred embodiment of this invention.
  • the drift in the thermoelectromotive force of the type KP alloy after 700 hours is about minus 400 microvolt at 1 200 °C, but the Ni-Cr-Si base alloy which is the preferred embodiment of this invention shows virtually no drift in thermoelectromotive force even at the higher temperature of 1 250 °C.
  • Figure 2 shows the degree of oxidation occurring in the same type KP alloy after exposure for 800 hours in air at 1 200 °C. It is evident that not only is there massive external scale developed on the surface of the alloy but also that a process of internal oxidation has resulted in the massive precipitation of oxide particles of the component elements chromium and silicon in the internal matrix of the alloy. We have found that this latter process of internal oxidation produces gross changes in the solute concentrations of chromium and silicon and it is these changes in concentration, which are temporally progressive, that are the cause of the relatively high degree of instability of thermoelectromotive force in the KP alloys under the stated conditions.
  • the preferred strengthening elements of this invention namely molybdenum, tungsten, niobium and tantalum, either in the single or the combined concentrations of the preferred embodiments, will not deleteriously affect the oxidation resistance of these preferred alloys in any significant way.
  • Figure 3 shows the tensile strength of the Ni-Cr-Si base alloy which is the preferred embodiment of this invention as a function of temperature in the fully annealed condition. Whilst the tensile strength of this alloy above 1 000 °C is adequate for many general purposes for which the alloys of this invention are intended, there are a number of critical applications in the nuclear, aerospace, electronics and general engineering fields for which the strength values shown in Figure 2 are inadequate.
  • the Ni-Cr-Si alloy which is the base alloy of this invention is significantly strengthened at high temperatures by the addition of small amounts of one or more of the elements molybdenum, tungsten, niobium and tantalum.
  • Table 4 summarizes the results of another experiment, in which the base alloy was nicrosil.
  • the alloys of the present invention were compared with inconel-600 and stainless steel-310.
  • Inconel-600 is about 23 % weaker than nicrosil and nearly 60 % weaker than NPX-3.
  • Stainless steel-310 is about 25 % stronger than nicrosil, but is about 35 % weaker than NPX-3.
  • Nicrosil is more oxidation resistant than either stainless steel-310 or inconel-600. There is some evidence to suggest that niobium improves the oxidation resistance of Ni-Cr-Si alloys, particularly in atmospheres of low oxygen partial pressure.
  • the strengthening elements namely Mo, W, Nb and Ta, when added to the preferred base alloy of Ni-Cr-Si, in any combination, have effects one with another as stated above. These elements are therefore interchangeable to a certain degree. Alloys of the invention may therefore be compositionally variant in respect of their Mo, W, Nb and Ta contents to a greater degree than is indicated by the preferred embodiments described in Table 1. A second group of preferred embodiments of the alloys of this invention are therefore described as follows :
  • An important feature of the alloys of this invention is that the kinetic processes governing the variation of the size and shape of their crystal grains must occur with sufficiently high velocity to make possible a predetermined choice of grain size by a simple heat treatment in which the parameters of temperature and (relatively short) time are mutually variable. This is because in different applications of the alloys different average grain sizes are desirable even obligatory.
  • Figure 4 shows that the grain sizes of the Ni-Cr-Si base alloy of the preferred embodiments of this invention are inherently readily variable as a function of temperature.
  • the strengthening elements Mo, W, Nb, and Ta, of this invention do not have unduly large inhibitory effects either in the elevation of recrystallization temperatures or in the rates of grain growth in individual alloy embodiments.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Continuous Casting (AREA)

Claims (10)

1. Legierung auf Nickelbasis, welche aus 13,5 bis 14 Gew.-% Chrom, 1,0 bis 1,5 Gew.-% Silizium und als Rest, abgesehen von Verunreinigungen, Nickel enthält, dadurch gekennzeichnet, daß sie ferner mindestens ein Element enthält, das aus Molybdän, Wolfram, Niob und Tantal ausgewählt ist, und zwar in einer Gewichtskonzentration von Molybdän : bis zu 5,0 % maximal, Wolfram : bis zu 1,0 % maximal, Niob : bis zu 3,0 % maximal, und Tantal : bis zu 2,0 % maximal, sowie wahlweise bis zu 0,5 % Magnesium und/oder bis zu 0,2 % Cer.
2. Legierung nach Anspruch 1, mit der folgenden Gewichtszusammensetzung :
Figure imgb0007
und als Rest, abgesehen von Verunreinigungen, Nickel.
3. Legierung nach Anspruch 2 welche 1,0 % Mo, 0,5 % W, 1,0 % Nb und 1,0 % Ta enthält.
4. Legierung nach Anspruch 1, welche 3,0 % Mo und 1,0 % W enthält.
5. Legierung nach Anspruch 1, welche bis zu 0,2 % Magnesium und/oder bis zu 0,2 % Cer enthält.
6. Legierung nach Anspruch 1, welche von 0,10 bis 0,20 % Magnesium enthält.
7. Legierung nach Anspruch 1, welche von 0,02 % bis 0,06 % Cer enthält.
8. Legierung nach Anspruch 1, welche bis zu 0,15 % Magnesium enthält.
9. Legierung nach Anspruch 1, welche bis zu 0,04 % Cer enthält.
10. Legierung nach einem der Ansprüche 1 und 2 bis 4, welche 0,15 % Magnesium und 0,04 % Cer enthält.
EP19860306987 1985-09-12 1986-09-10 Legierungen auf Nickelbasis für Verwendung bei hohen Temperaturen Expired EP0218379B1 (de)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
AU2397/85 1985-09-12
AUPH239785 1985-09-12
AU2587/85 1985-09-24
AUPH258785 1985-09-24
AUPH579286 1986-05-07
AU5792/85 1986-05-07
AU62404/86A AU581342B2 (en) 1985-09-12 1986-09-04 Nickel based alloys with chromium for high temperature applications

Publications (2)

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EP0218379A1 EP0218379A1 (de) 1987-04-15
EP0218379B1 true EP0218379B1 (de) 1989-12-13

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU613902B2 (en) * 1987-05-14 1991-08-15 Nicrobell Pty Limited Stable high-temperature thermocouple cable
AU622856B2 (en) * 1987-10-23 1992-04-30 Nicrobell Pty Limited Thermocouples of enhanced stability

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB108164A (en) * 1916-04-26 1917-07-26 Alfred Ernest White Improvements in and relating to Metal Alloys.
GB507167A (en) * 1937-12-10 1939-06-12 British Driver Harris Co Ltd Improvements relating to alloys, particularly for resistance wire for electric fires, heaters and the like
US2422489A (en) * 1945-06-02 1947-06-17 Int Nickel Co Welding electrode
GB766392A (en) * 1953-11-12 1957-01-23 Kanthal Ab Electric resistors and alloys for use therein
US3841868A (en) * 1972-12-22 1974-10-15 Howmedica Nickel alloys

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