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US3166409A - Silicon-niobium alloys - Google Patents

Silicon-niobium alloys Download PDF

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Publication number
US3166409A
US3166409A US284378A US28437863A US3166409A US 3166409 A US3166409 A US 3166409A US 284378 A US284378 A US 284378A US 28437863 A US28437863 A US 28437863A US 3166409 A US3166409 A US 3166409A
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Prior art keywords
niobium
oxidation
atomic percent
alloys
test
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US284378A
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Hubbard Roger Thomas John
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Imperial Metal Industries Kynoch Ltd
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Imperial Metal Industries Kynoch Ltd
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
    • C04B35/58085—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicides
    • C04B35/58092—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicides based on refractory metal silicides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/06—Metal silicides
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
    • C04B35/58085—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
    • C22C27/02—Alloys based on vanadium, niobium, or tantalum

Definitions

  • This invention relates to niobium alloys. ly concerned with oxidation resistant alloys.
  • niobium alloys which retain their mechanical properties at high temperatures, but they are not resistant to oxidation.
  • the most oxidation resistant strong niobium alloys are at least ten times more resistant to oxidation than pure niobium, but their oxidation rates are still about fifty times higher than could be tolerated inservice.
  • niobium alloys which have sufficiently low oxidation rates are generally based on brittle intermetallic compounds. However, most of these alloys oxidise more rapidly at intermediate temperatures than at high temperatures, producing a low temperature oxidation rate peak. This peak may be shown by isothermal and slow thermal cyclic testing, both of which conditions may be encountered in service.
  • One object of the present invention is to improve the high temperature oxidation resistance and to reduce the oxidation rate peak of niobium disilicide by ternary alloying additions.
  • the present invention provides alloys based on the intermetallic compound niobium disilicide, in which part of the niobium is replaced by at least one of the metals aluminum, chromium, iron or titanium, these addition elements being present in such amounts as to maintain the disilicide stoichiometry of the compound.
  • the alloys of the present invention are of the composition represented by the formula MSi Where M is niobium plus at least one of the addition elements listed, to a total of 33 /3 atomic percent.
  • the silicon content is always about 66 /3 atomic percent and preferably does not vary by more than plus or minus two atomic percent.
  • All the alloys exemplified are based on the intermetallic compound niobium disilicide containing 33 /3 atomic percent niobium and 66% atomic percent silicon.
  • composition of the alloys is of the general form MSi deteriorate due to severe oxidation and thickening of the where M represents niobium plus one of the addition elements aluminum, chromium, iron, titanium, the total atomic percentage of M being 33 /3 .For comparison, results are also given for niobium disilicide without addition.
  • Test 1 was performed as follows:
  • This test indicates the formation of an initial high temperature oxide film on the surface. After the film has been formed the rate of oxidation is reduced.
  • Test 2 was performed as follows:
  • This test was designed to show the oxidation rate at a constant temperature of 1200 C. after an initial oxide film has been formed.
  • Test 3 was performed as follows:
  • Test 1(f) This test shows the behaviour on heating and cooling and is the most significant test, since it indicates the resistance to oxidation over a range of temperatures under conditions of heating and cooling typical of those encountered in service.
  • Test 4 was performed as follows:
  • Alloys containing more than 10 atomic percent of aluminium contain low melting point phases which were exuded as globules on the surface during oxidation at 1100 C. and 1200 C. Alloys containing 3 /3 and 6 /3 atomic percent chromium formed an oxide film which spalled on cooling to room temperature. Alloys containing up to 6% atomic percent of titanium suffered from spalling of the oxide scale.
  • the alloys of the present invention are brittle and diflicult to fabricate but they can be employed in the cast 4.
  • a niobium-silicon alloy consisting essentially of form or used as oxidation resistant coatings on other nio 64 /3 to 68% atomic percent silicon, 1% to 23 /3 atomic bium alloys. a percent iron and the balance niobium.
  • N Negligible oxidation, weightgain less than 0.1 mgJcm. during test.
  • Condition of Film- VG Very good adherent uniform film.
  • SL Film spelled in places due to localised oxidation.
  • I GL Good film, but some slight localised oxidation due to inhomogeneity.
  • F Glassy film of silica or silicate.
  • S1 Severe spelling on cooling to room temperature.
  • S Slight spalling I claim: 35 5.
  • a niobium-silicon alloy consisting essentially of 1.
  • a niobium-silicon alloy consisting essentially of: 64 /3 to 68% atomic percent silicon, 6 /3 to 23 /3 atomic 64% to 68 /3 atomic percent silicon, an addition agent sepercent titanium and the balance niobium. lected from the group consisting of 1% to 10 atomic aluminum, 1 /3 to 23 /3 atomic percent chromium, 1 /3 to References C'ted b the Examin 23 /3, atomic percent iron and 6% to 23 /3 atomlc percent 40 l y 7 er titanium, and the balance essentially niobium.
  • a niobium-silicon alloy consisting essentially of 2,169,193 8/39 Cornstock 75--134.3 64 /3 to 68 /3 atomic percent silicon, 1% to 10 atomic 2,939,785 6/66 Weatherly et a1. 75-474 percent aluminum and the balance niobium.
  • a niobium-silicon alloy consisting essentially of DAVID RECK Pnmary Examiner 64 /3 to 68% atomic percent silicon, 1 /3 to 23% atomic WINSTON PQUGLAS, Examiner, percent chromium and the balance niobium. i l

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Structural Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Inorganic Chemistry (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Ceramic Products (AREA)

Description

United States Patent Office R 3,166,409 Patented Jan. .19, 196.5
This invention relates to niobium alloys. ly concerned with oxidation resistant alloys.
There are niobium alloys which retain their mechanical properties at high temperatures, but they are not resistant to oxidation. The most oxidation resistant strong niobium alloys are at least ten times more resistant to oxidation than pure niobium, but their oxidation rates are still about fifty times higher than could be tolerated inservice.
Those niobium alloys which have sufficiently low oxidation rates are generally based on brittle intermetallic compounds. However, most of these alloys oxidise more rapidly at intermediate temperatures than at high temperatures, producing a low temperature oxidation rate peak. This peak may be shown by isothermal and slow thermal cyclic testing, both of which conditions may be encountered in service.
One of the most oxidation resistant binary intermetallic compounds of niobium in the disilicide Nbsi which is fairly resistant to high temperature oxidation but suffers from an oxidation rate peak at 1000-1050" C.
One object of the present invention is to improve the high temperature oxidation resistance and to reduce the oxidation rate peak of niobium disilicide by ternary alloying additions.
Accordingly the present invention provides alloys based on the intermetallic compound niobium disilicide, in which part of the niobium is replaced by at least one of the metals aluminum, chromium, iron or titanium, these addition elements being present in such amounts as to maintain the disilicide stoichiometry of the compound. Thus the alloys of the present invention are of the composition represented by the formula MSi Where M is niobium plus at least one of the addition elements listed, to a total of 33 /3 atomic percent. The silicon content is always about 66 /3 atomic percent and preferably does not vary by more than plus or minus two atomic percent.
We have found that such alloys possess high oxidation resistance both at elevated temperatures and at lower temperatures and are resistant to oxidation during cycles of heating and cooling, especially after a high temperature oxide film has been formed.
We have found that small additions of the metals listed are effective and that the improvement in properties is maintained when over half of the niobium has been replaced. In particular we have found that up to 23% atomic percent of the addition elements reduces the rate of' oxidation. Although some improvement in oxidation resistance is obtained over the whole range there are certain limitations to the amounts of addition for optimum beneficial effect. Alloys containing aluminum in excess of about have low melting point constituents which are exuded on the surface at high temperatures. Alloys containing less than about 6% atomic percent titanium It is especial- Properties of certain alloys exemplifying the invention are listed in the accompanying table.
All the alloys exemplified are based on the intermetallic compound niobium disilicide containing 33 /3 atomic percent niobium and 66% atomic percent silicon. The
. composition of the alloys is of the general form MSi deteriorate due to severe oxidation and thickening of the where M represents niobium plus one of the addition elements aluminum, chromium, iron, titanium, the total atomic percentage of M being 33 /3 .For comparison, results are also given for niobium disilicide without addition.
Test 1 was performed as follows:
This test indicatesthe formation of an initial high temperature oxide film on the surface. After the film has been formed the rate of oxidation is reduced.
Test 2 was performed as follows:
'(a) Samples from Test 1 (i.e., with an adherent oxide film present). (12) Heated for 24 hours at 1200 C. (0) Results expressed as weight gain per unit surface area er hour (mg/sq. cm./hr.).
This test was designed to show the oxidation rate at a constant temperature of 1200 C. after an initial oxide film has been formed.
Test 3 was performed as follows:
(a) Samples from Test 2.
(b) Heated at 1200 C..for 15 min.
(0) Cooled to 600 C. in 60 min.
(d) Heated from 600 C. to 1200? C. at 6 C./min. (e) Results expressed as in Test 1(f) This test shows the behaviour on heating and cooling and is the most significant test, since it indicates the resistance to oxidation over a range of temperatures under conditions of heating and cooling typical of those encountered in service.
Test 4 was performed as follows:
(a) Samples from Test 3. (b) Heated for hrs. at 1100 C. (0) Results expressed as in Test 2(a) This test shows the long-term oxidation characteristics including the effect of oxygen contamination, the possibility of the oxide film spalling off if it becomes too thick, and the presence of low melting point constituents.
It will be seen from the results that all the alloys listed are more resistant to oxidation than niobium disilicide. The rate of oxidation of niobium disilicide itself is less than that of niobium by a factor of about 50. The properties revealed by Test 3 are particularly significant.
Alloys containing more than 10 atomic percent of aluminium contain low melting point phases which were exuded as globules on the surface during oxidation at 1100 C. and 1200 C. Alloys containing 3 /3 and 6 /3 atomic percent chromium formed an oxide film which spalled on cooling to room temperature. Alloys containing up to 6% atomic percent of titanium suffered from spalling of the oxide scale.
The alloys of the present invention are brittle and diflicult to fabricate but they can be employed in the cast 4. A niobium-silicon alloy consisting essentially of form or used as oxidation resistant coatings on other nio 64 /3 to 68% atomic percent silicon, 1% to 23 /3 atomic bium alloys. a percent iron and the balance niobium.
Atomic percent Test 1 Test 2 Test 3 Test; 4 p
' V Condition Addition Addition Oxidation Oxidation Oxidation Oxidation of film element Nb i1% Si =i:2% element rate, mg./ rate, mg./ rate, ing./ rate, mg./ i :l:%% sq. cmJhr. sq. cmJhr. sq. cm./l1r. sq. cm./hr.
31% 66% 1% 0. 11 O. 019 N N VG Al 30 66% 3% 0.12 N N Nv VG 26% 66% 6% 0. 11 0. 03 0. 03 0. 014 GL 31% 66% 1% 0. 10 0. 014 0. 06 0.015 GL 66% 3% 0. 22 0.03 0. 10 SL Or 66% 6% 0. 12 N N 0. 03 SL 23% 66% 10 0.17 0.05 N 0.003 VG 16% 66% 16% 0. 21 0. O 0. 09 0. 002 VG 10 66% 23% 0. 35 0. 076 0. 04 0. 022 S 31% 66% 1% 0. N N -Q VG 30 66% 3% O. 48 N N 0. 001 GL 26% 66%. 6% 0.29 N 0.06 0. 001 G Fe 23% 66% 0. 0. 03 0. 02 0. 006 GL 16% 66% 16% 0. 17 0. 03 0. 02 N GL 66% 23% 0.30 0. 6 22 0. 022 0. 60* F 66% 33% N N .r F
26% 66% 6% 0. 11 p 0. 01 0. 07 0. 68 S1 23% 66% 10 0. 13 0. 01 0.02 0. 603 GL Ti 16% 66% 16% 0. 18 0. 02 0. 09 N VG 10 66% 23% 0. 08 0. 034 N N F 66% 33% N N F N=Negligible oxidation, weightgain less than 0.1 mgJcm. during test. Condition of Film- VG=Very good adherent uniform film. SL=Film spelled in places due to localised oxidation. I GL=Good film, but some slight localised oxidation due to inhomogeneity. F= Glassy film of silica or silicate. S1=Severe spelling on cooling to room temperature. S =Slight spalling I claim: 35 5. A niobium-silicon alloy consisting essentially of 1. A niobium-silicon alloy consisting essentially of: 64 /3 to 68% atomic percent silicon, 6 /3 to 23 /3 atomic 64% to 68 /3 atomic percent silicon, an addition agent sepercent titanium and the balance niobium. lected from the group consisting of 1% to 10 atomic aluminum, 1 /3 to 23 /3 atomic percent chromium, 1 /3 to References C'ted b the Examin 23 /3, atomic percent iron and 6% to 23 /3 atomlc percent 40 l y 7 er titanium, and the balance essentially niobium. UNITED STATES PATENTS 2. A niobium-silicon alloy consisting essentially of 2,169,193 8/39 Cornstock 75--134.3 64 /3 to 68 /3 atomic percent silicon, 1% to 10 atomic 2,939,785 6/66 Weatherly et a1. 75-474 percent aluminum and the balance niobium.
3. A niobium-silicon alloy consisting essentially of DAVID RECK Pnmary Examiner 64 /3 to 68% atomic percent silicon, 1 /3 to 23% atomic WINSTON PQUGLAS, Examiner, percent chromium and the balance niobium. i l

Claims (1)

1. A NIOBIUM-SILICON ALLOY CONSISTING ESSENTIALLY OF: 64 2/3 TO 68 2/3 ATOMIC PERCENT SILICON, AN ADDITION AGENT SELECTED FROM THE GROUP CONSISTING 1 2/3 TO 10 ATOMIC ALUMINUM, 1 1/3 TO 23 1/3 ATOMIC PERCENT CHROMIUM, 1 1/3 TO 23 1/3 ATOMIC PERCENT IRON AND 6 2/3 TO 23 1/3 ATOMIC PERCENT TITANIUM, AND THE BALANCE ESSENTIALLY NIOBIUM.
US284378A 1962-06-01 1963-05-31 Silicon-niobium alloys Expired - Lifetime US3166409A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1229146A3 (en) * 2001-02-02 2004-03-31 General Electric Company Oxidation resistant coatings for niobium-based silicide composites
US20120238439A1 (en) * 2009-08-21 2012-09-20 Massachusetts Institute Of Technology Silicon-rich alloys

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2169193A (en) * 1938-01-06 1939-08-08 Titanium Alloy Mfg Co Chromium-titanium-silicon alloy
US2939785A (en) * 1956-12-04 1960-06-07 Union Carbide Corp Refractory metal and silicon selfhealing high temperature alloy

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2169193A (en) * 1938-01-06 1939-08-08 Titanium Alloy Mfg Co Chromium-titanium-silicon alloy
US2939785A (en) * 1956-12-04 1960-06-07 Union Carbide Corp Refractory metal and silicon selfhealing high temperature alloy

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1229146A3 (en) * 2001-02-02 2004-03-31 General Electric Company Oxidation resistant coatings for niobium-based silicide composites
US20120238439A1 (en) * 2009-08-21 2012-09-20 Massachusetts Institute Of Technology Silicon-rich alloys

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