US3639180A - Niobium-base alloys - Google Patents

Niobium-base alloys Download PDF

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US3639180A
US3639180A US883424A US3639180DA US3639180A US 3639180 A US3639180 A US 3639180A US 883424 A US883424 A US 883424A US 3639180D A US3639180D A US 3639180DA US 3639180 A US3639180 A US 3639180A
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percent
carbon
silicon
alloy
hafnium
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US883424A
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Robert William Kelcher
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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
    • 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

  • Niobium-base alloys possess good high-temperature strength and in particular alloys containing tungsten up to about 30 percent, hafnium up to about 4 percent and carbon up to about 0.2 percent and sometimes also containing molybdenum and zirconium have good stress-rupture life, tensile properties and ductility.
  • a niobium'base alloy possessing a high-yield point and tensile strength at elevated temperature consists of -30 percent tungsten, 0.06-0.14 percent carbon, hafnium in an atomic ration of I.2-2.2:1 carbon, 0.0I0.l percent silicon and optionally up to 6 percent molybdenum replacing an equivalent atomic percentage of tungsten; and optionally up to 4 percent zirconium, balance niobium, and impurities.
  • the third requirement for the formation of an effective dispersion of silicon carbide is a network of dislocations for the silicon carbide to nucleate on. If few dislocations are present then nucleation of silicon carbide is difficult because of its complex structure, and a small number of coarse particles form with little effect on strength.
  • the first step in the development of optimum properties is a solution treatment. This dissolves the silicon and some of the carbon; during cooling the carbon which was in solution, precipitates out in ametastable form, either as Nb C needles or NbC plates.
  • the material is worked to generate dislocations within the metal.
  • a fine precipitate forms on the dislocations, and it is this precipitate which is responsible for the strengthening effect by hindering the movement of the dislocations.
  • the precipitate particles are very small (about A. diameter) and have not been positively identified, but are believed to be silicon carbide rather than hafnium carbide, as hafnium carbide particles 120 A. in diameter would be coherent with the matrix and show strain fields when observed by transmission electron microscopy, whereas no strain fields have been observed. Silicon carbide would not be expected to show strain fields as its structure is very different from the simple body centered cubic structure of niobium and for these reasons it is assumed that the precipitate is silicon carbide.
  • Silicon has little effect below 100 p.p.m. and alloys will be too brittle if they contain more than 500 p.p.m. with the optimum hafniumzcarbon atomic ratio. However, with higher hafnium:carbon ratio, the silicon content can exceed 500 p.p.m. without causing brittleness and the silicon contents over which the benefits are obtained are I00-L000 p.p.m., the preferred range being -500 p.p.m.
  • the maximum hafniumacarbon atomic ratiowhich can be tolerated is 22:1 and the minimum is 1.2:l but preferably the range lies within these limits, the hafnium being l.52.0:l carbon.
  • the solution treatment temperature depends upon the hafniumzcarbon ratio of the alloy and the tungsten content and increases as these parameters increase.
  • the minimum temperature for an alloy having a nominal composition of niobium, 17 percent tungsten, 3.5 percent hafnium, 0.12 percent carbon (SU 3 l is 1,600 C. and the maximum, which is determined by the onset of brittleness caused by the presence of excessive carbide at the grain boundaries is about 1,750 C.
  • the alloy is heated at these temperatures for about 1 hour.
  • Working is applied to the alloy while in the solution-treated condition and should be between 10 percent and 50 percent reduction at a working temperature of l00800 C.
  • the preferred amount of working is 15-25 percent at 200-800 C. for Su 31.
  • the alloy After working, for example to effect final shaping as in a turbine blade, the alloy is aged between 950-l,l50 C., preferably l,lO0 C. for 5 hours. Below 950 C., the formation of silicon carbide is too slow and above 1,150 C. the precipitate overages.
  • the general efiect of increasing silicon content is to raise the proof and ultimate strengths of the alloy by about the same extent for all levels within the range of silicon content, as shown by the slope of the lines in FIG. 1.
  • the ultimate tensile strength varies with the silicon content and with the hafnium-carbon ratio as shown in the Table.
  • Sample 6 of the Table shows for comparison purposes an alloy having a hafniumwarbon ratio in excess of the maximum specified in the present invention and it will be noted that there is a large decrease in ultimate strength compared with sample 5, although the silicon content is greater than in sample 5.
  • lam W"- F 10. 2 shows the effect of silicon content on ultimate tensile strength in graphical form based on the tests reported in the Table. From the curve it will be seen that below about 120 p.p.m. silicon has little effect but above 120 p.p.m. its effect increases rapidly. Those samples having hafniumzcarbon ratios below 2:1 fall very close to the curve, but the single result for the sample having a hafniumzcarbon ratio of 2.3:1 is located well away from the curve, thus indicating the criticality of the hafniumzcarbon ratio.
  • alloys with higher hafnium:carbon ratios are weakercompare samples 1 and 2 in the Table-and at a very high hafniumzcarbon ratio of 2.3:1 (sample 6) the strengthening effect of silicon is nullified because no carbon is available for reaction with the silicon to form silicon carbide.
  • the ultimate tensile strength can be raised by increasing the solution treatment temperature. For example, sample increased its strength from 69.4 to 74 hectobars (hbars (45.1 to 48 tonf/in?) when the solution treatment temperature was increased from 1,600 to 1,700 C. all other parameters remaining constant.
  • FIG. 3 shows the effect of silicon on elongation and reduction in area values
  • FIG. 4 shows the influence of silicon on the stress rupture properties of the alloy SU 31.
  • the alloys were in the heat-treated, worked and aged condition.
  • Tungsten may be varied within the range specified and the effect of the variations is that the strength levels are raised or lowered in proportion to the amount of tungsten present.
  • tensile strength at elevated temperature consisting of 10-30 percent tungsten, 0.06-0.14 percent carbon, hafnium in an atomic ratio of 1.2-2.2:1 carbon, 0.01-0.l percent silicon and optionally up to 6 molybdenum replacing an equivalent atomic percentage of tungsten; and optionally up to 4 percent zirconium, balance niobium and impurities, said alloy exhibiting a microstructure wherein the silicon is present as silicon carbide precipitated on a network of dislocations within the alloy.
  • a method for producing a niobium-base alloy possessing a high-yield point and tensile strength at elevated temperature comprising: heating an alloy consisting of 10-30 percent tungsten, 0.06-0.14 percent carbon, hafnium in an atomic ratio of 1.2-2.2:1 carbon, 0.01-0.1 percent silicon, up to 6 percent molybdenum replacing an equivalent atomic percentage tungsten, and up to 4 percent zirconium, balance niobium and impurities to a temperature in the range 1,600 to 1,7S0 C., to dissolve the silicon and carbon; cooling to precipitate carbon in metastable form; working said alloy to effect a reduction of 10 percent to 50 percent at a temperature of to 800 C.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Carbon And Carbon Compounds (AREA)
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US883424A 1968-12-19 1969-12-09 Niobium-base alloys Expired - Lifetime US3639180A (en)

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US (1) US3639180A (enrdf_load_stackoverflow)
DE (1) DE1963801C3 (enrdf_load_stackoverflow)
FR (1) FR2026600A1 (enrdf_load_stackoverflow)
GB (1) GB1251828A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4836849A (en) * 1987-04-30 1989-06-06 Westinghouse Electric Corp. Oxidation resistant niobium alloy
CN100348756C (zh) * 2005-12-27 2007-11-14 北京航空航天大学 一种单相铌钨铪超高温合金材料
US11198927B1 (en) 2019-09-26 2021-12-14 United States Of America As Represented By The Secretary Of The Air Force Niobium alloys for high temperature, structural applications
US11846008B1 (en) 2019-09-26 2023-12-19 United States Of America As Represented By Secretary Of The Air Force Niobium alloys for high temperature, structural applications

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8719877D0 (en) * 1987-08-22 1987-09-30 Wellcome Found Antiviral compounds
CN116288092B (zh) * 2023-03-29 2024-05-10 西北有色金属研究院 一种改善铌合金铸锭热加工性能的热处理方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB889099A (en) * 1959-06-11 1962-02-07 Gen Electric Improvements in columbium-tungsten-titanium alloys
GB1013220A (en) * 1963-01-04 1965-12-15 Imp Metal Ind Kynoch Ltd Niobium-base alloys

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB889099A (en) * 1959-06-11 1962-02-07 Gen Electric Improvements in columbium-tungsten-titanium alloys
GB1013220A (en) * 1963-01-04 1965-12-15 Imp Metal Ind Kynoch Ltd Niobium-base alloys

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4836849A (en) * 1987-04-30 1989-06-06 Westinghouse Electric Corp. Oxidation resistant niobium alloy
CN100348756C (zh) * 2005-12-27 2007-11-14 北京航空航天大学 一种单相铌钨铪超高温合金材料
US11198927B1 (en) 2019-09-26 2021-12-14 United States Of America As Represented By The Secretary Of The Air Force Niobium alloys for high temperature, structural applications
US11846008B1 (en) 2019-09-26 2023-12-19 United States Of America As Represented By Secretary Of The Air Force Niobium alloys for high temperature, structural applications

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FR2026600A1 (enrdf_load_stackoverflow) 1970-09-18
GB1251828A (enrdf_load_stackoverflow) 1971-11-03
DE1963801A1 (de) 1970-07-09
DE1963801B2 (de) 1974-01-03
DE1963801C3 (de) 1974-08-01

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