Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
  • C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
  • C23C10/34—Embedding in a powder mixture, i.e. pack cementation
  • C23C10/36—Embedding in a powder mixture, i.e. pack cementation only one element being diffused
  • C23C10/38—Chromising
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/922—Static electricity metal bleed-off metallic stock
  • Y10S428/923—Physical dimension
  • Y10S428/924—Composite
  • Y10S428/926—Thickness of individual layer specified
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/922—Static electricity metal bleed-off metallic stock
  • Y10S428/9335—Product by special process
  • Y10S428/941—Solid state alloying, e.g. diffusion, to disappearance of an original layer
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12806—Refractory [Group IVB, VB, or VIB] metal-base component
  • Y10T428/12826—Group VIB metal-base component
  • Y10T428/12847—Cr-base component
  • Y10T428/12854—Next to Co-, Fe-, or Ni-base component

Definitions

• the present invention relates to alloys havingexcellent heatand corrosion resisting properties to combustion .gas produced from fuels containing high sulfur, such as .C-class heavy oil which contains about 3.5% sulfur as shown in K 20051960 1 18 (Japanese Industrial Standard). More particularly, it relates to alloys showing sufiicient anti-corrosive property .in the case where such gases contain some alkali compounds, said alloy having sufficient mechanical strength at high temperatures.
• composition of an alloy namely the kind of elements composing said alloy and proportions of such elements, is determined in accordance with the uses or ap plications for the alloy.
• composition of an alloy is determined according to the use so as to impartfavorable properties or performances requisite for uses of the alloys.
• properties there may be mentioned, for
• heat resistance i.e. tensile strength, shearing strength, yielding value and creap strength.
• Gas turbine blades are caused to revolve at a high velocity in contact with high temperature combustion gas.
• alloys for gas turbine blades are required to 3,664,765 Patented May 23, 1972 have three properties, i.e. sufficient mechanical strength at high temperatures above 800 0, sufficient heat resistance and sufiicient corrosion resistance to high temperature combustion gas and corrosive ash.
• alloys satisfying the above-mentioned three properties super alloys containing metal elements such as nickel, cobalt, chromium and the like in a high quantity, for instance, Inconel, Udimet, LON-155 (refer to Table I) and others are well known. These alloys have been widely used for turbine blades.
• the turbine blades made of the above-mentioned alloys are durable for a long period of time in the case where fuels containing low or no sulfur like natural gas are employed.
• the turbine blades made of the above described alloys are corroded or give rise to scales on their surfaces where fuels of high sulfur content, such as C-class heavy oil, are employed, thereby becoming frequently impossible to use in a short period of time.
• Sulfates of alkali metals are formed by reaction between sulfur oxides, such as S0 and S0 produced from combustion of S in the fuel, and alkali compounds contained in the fuel gas.
• Inconel-700 possesses sufiicient mechanical strength at high temperatures, suflicient heat resistance and suflicient corrosion resistance against high temperature combustion gases and possesses the above-mentioned three performances ordinarily requisite as alloy for turbine blades:
• Inconel-700 is not sufficiently resistant to combustion gases containing sulfur oxides and alkali compounds and is remarkably corroded in a relatively short period of time.
• alloys satisfying the hereinbefore described five performances can beobtained by forming a chromium diffusion layer by means of chromizing method on the surface of an alloy (hereintion so as not to scale, even when exposed to combustion 5 after referred to as base alloy) composed mainly of gas containing sulfur oxides and alkali compounds, in Cr, Ni and Co and having the following composition: addition to the said four performances in total.
• base alloy composed mainly of gas containing sulfur oxides and alkali compounds, in Cr, Ni and Co and having the following composition: addition to the said four performances in total.
• alloys The present invention is a novel proposition basedon having five Performances as dfiscfihed ahOVethe results of investigations as described above.
• a further object of the present invention is to make the seen by comparing Table I with Table II, these alloys cheap sulfur-containing fuel useful as a gas turbine fuel. contain, in some cases, some by-constituents which are The present inventors have also executed laborious not shown in Table I.
• alloy- A1 below 5 1 an alloy formed with an aluminum dif- T1 below 4 fusion layer on the surface of Inconel-700 (called alloy- A1 below 5 1) shows a better result in the accelerating test, as com- Fe below 4 pared with an alloy formed w1th a chromium diffusion W below 8 layer on the surface of Inconel-700 (called alloy-2), Nb below 4 While in the practical test, said alloy-1 shows far inferior v I below 1 result as compared with said alloy-2.
• alloy-2 shows a good result in the pracn tical test, the alloy having a chromium diffusion layer on Further, the detailed properties of the above described the surface of InconelX (called alloy-3) shows extremealloys are described in ly bad results.
• Engineering Alloys (the Fourth edition), by Norman At the present stage of the investigation, it is not E. Woldman, published by Reinhold Publishing Corp. definltely evident why the above-mentioned results (1) Chapman & Hall Ltd., London, and bal in Table I and and (2) are obtained. II means a balance, i.e. percent remainder left after other However, it has been proved from the result of exconstituents have been subduced from 100.
• the chromizing method is a method wherein the metal or alloy, that is, the substances to be treated (hereinafter simply referred to as a base alloy) is brought into contact with the vapor of CrX (wherein X is Cl, I or F), at high temperature, in a reducing atmosphere such as hydrogen gas, carbon monoxide gas or hydrocarbon or in a neutral atmosphere such as argon, to deposit Cr on the base alloy by decomposition of CrX and the thus deposited Cr diffuses and penetrates into the base alloy to form a Cr diffusion layer on the surface of the base alloy.
• a reducing atmosphere such as hydrogen gas, carbon monoxide gas or hydrocarbon or in a neutral atmosphere such as argon
• the diffusion layer obtained by the chromizing method has a high Cr content on the surface and the Cr content decreases gradually towards the base alloy, and the composition of the diffusion layer approaches rapidly to the composition of the base alloy on the boundary surface of both portions. Particularly good result can be obtained when the Cr content of the diffusioh layer is above 40% and the Cr content of the surface of the said layer is from 60 to 95%.
• the chromizing methods there are the following (1) powder method, and (2) gas method and the most widely used method is the former powder method.
• the powder method is a method wherein a base alloy is embedded in a mixture of finely divided powders of Cr or Cr-Fe alloy and a small quantity of NH X (wherein X is Cl, I or F) and heated in a reducing atmosphere such as a hydrogen stream.
• NH X reacts with fine powders of Cr or Cr-Fe alloy to produce CrX and CrX vapor thus produced comes into contact with the mother alloy to form the diffusion layer.
• a coagulation-preventing agent such as, for instance, kaolin or alumina is usually mixed in an amount of 0.5 to 2 times the quantity of Cr or Cr-Fe alloy powder with the Cr or Cr-Fe alloy powder in order to prevent the latter from adhering to the surface of the base alloy.
• NH X is NH Cl and about 2 to 4% of NH Cl is added to Cr or Cr-Fe alloy.
• the heating temperature ranges from 950 C. to 1100" C. and the heating time is in the range from 5 to hours.
• the gas method is a method wherein Cr or Cr-Fe alloy is caused to react with dry HCl at high temperature to produce CrCl and a chromium diffusion layer is formed by bringing the vapor of CrCl thus obtained into contact with a base alloy.
• a method called BDS method has been developed as one of the gas methods, wherein CrCl vapor generated is once absorbed in alumina or the like and the base alloy is embedded in alumina, in which CrCl thus obtained has been absorbed, and then heated.
• the BDS method is the most practical method of the gas methods.
• the me- 1 chanical strength of the base alloy can be restored by reheating the alloy' at a temperature somewhat higher than the chromizing temperature (for instance, at 1,170 C. for Inconel-700) for about 2 hours and cooling in air, and further reheating at a temperature somewhat lower than the chromizing temperature (for instance, at 820 C. for Inconel-700) for about 20 hours and cooling in air.
• the chromizing temperature for instance, at 1,170 C. for Inconel-700
• the chromizing temperature for instance, at 820 C. for Inconel-700
• a base alloy is embedded in a mixture of powders of alloy which is composed of 60% Cr and 40% Fe in weight of 10% of 30 to 40 mesh (Tyler sieve scale mesh), 20% of 40 to 60 mesh, 60% of 60 to mesh and 10% of 80 to mesh in size, fine alumina powder (about 30 to 60 mesh) in equal quantity of the alloy powder and 'NH Cl in the quantity of 3% of the alloy powder in weight, and then heated them in the hydrogen stream at the temperature and for the time shown in Table II.
• Mark in the composition represents by-constituents which are not shownin Table I of standard compositions or that the analytical values of composition of alloys available on the market are slightly different from the corresponding standard composition.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

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Cited By (5)

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• 1967
  • 1967-05-02 DE DE19671558440 patent/DE1558440A1/de active Pending
  • 1967-05-03 CH CH628067A patent/CH488820A/de not_active IP Right Cessation
• 1970
  • 1970-03-09 US US17014A patent/US3664765A/en not_active Expired - Lifetime

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