Niobium alloys (Nb-1Zr, C-103, FS-85) Nb alloys

spore: profile
id: niobium-alloys
spore_version: 0.2
family: refractory-metals
name: Niobium alloys (Nb-1Zr, C-103, FS-85)
abbreviation: Nb alloys
role: refractory niobium alloys for rocket and thruster nozzles, load-free thermal shields and alkali-metal containment
category: metals
type: refractory-metals
summary: |
  Three niobium alloys are profiled here. C-103 (Nb-10Hf-1Ti, UNS R04295) is the high-stress grade for rocket nozzles: Smiths High Performance gives a minimum yield strength of 124 MPa at 1093 °C in vacuum for fully recrystallised material, and a density of 8.850 g/cm3 at 20 °C. Nb-1Zr (UNS R04261) is the older, cheaper grade: ATI gives a density of 8.57 g/cm3 and a melting point of 2410 ±10 °C, and calls it suitable for low-load thermal shields. FS-85 (Cb + 28Ta + 10W + 1Zr) was tested by NASA Lewis for alkali-metal containment, where 1 percent creep strain took 775 h at 2000 °F and 10,000 psi. No datasheet was read for a Nb-Ta binary grade in this run.
best_for: 'Hot load-bearing nozzles: C-103 keeps a minimum yield strength of 124 MPa at 1093 °C in vacuum (Smiths datasheet, minimum values)'
weakest_at: 'Oxidation in air: all three need a protective coating above about 400 °C (Wikipedia). Niobium supply is concentrated in Brazil, which mines about 93 % of world niobium (USGS 2026).'
identity:
  formula: 'C-103: Nb with 9.0 to 11.0 mass % Hf and 0.7 to 1.3 mass % Ti, maximum 0.7 Zr, 0.5 Ta and 0.5 W in mass % (Stainless SA chemical analysis).Nb-1Zr: Nb with 1 % Zr (ATI). FS-85: Cb + 28Ta + 10W + 1Zr, nominal (NASA TN D-2885 title)'
  source: ati-nb1zr
  where: 'Title block: ATI Nb1Zr Alloy (Type 3 and 4), Niobium Alloy, UNS R04261'
  designations:
    - system: UNS
      code: R04261
      source: ati-nb1zr
      where: 'Title block: ATI Nb1Zr Alloy, UNS R04261'
    - system: UNS
      code: R04295
      source: stainless-c103
      where: 'Header block: NIOBIUM C-103, UNS R04295'
    - system: Trade name
      code: C-103
      source: smiths-c103
      where: 'Title block: Niobium C-103, proprietary product of Materion'
    - system: Trade name
      code: Nb1Zr
      source: ati-nb1zr
      where: 'Title block: ATI Nb1Zr Alloy'
    - system: Trade name
      code: FS-85
      source: nasa-fs85
      where: 'Report title: Creep behavior of a columbium alloy, FS-85'
    - system: ASTM
      code: B654
      note: plate, sheet and strip
      source: stainless-c103
      where: 'Standards line: ASTM B652, B654, B655'
    - system: ASTM
      code: B655
      note: bar and wire
      source: stainless-c103
      where: 'Standards line: ASTM B652, B654, B655'
    - system: AMS
      code: '7852'
      note: sheets and plates, C-103
      source: stainless-c103
      where: 'Standards line: AMS 7852 (sheets and plates)'
    - system: AMS
      code: '7857'
      note: rods and wires, C-103
      source: stainless-c103
      where: 'Standards line: AMS 7857 (rods and wires)'
tags:
  environments: []
  stresses: []
  applications:
    - propulsion-and-tanks
    - heat-shields
    - structures
properties:
  - benchmark: density
    label: Density, C-103
    value: 8.85
    unit: g/cm3
    scope: material
    conditions:
      grade: Niobium C-103
      temperature: 20 °C
      unit_in_source: 8.850 gm/cubic cm
    method: Value printed in the physical properties table of the Smiths High Performance datasheet, metric column
    status: ground
    source: smiths-c103
    where: Page 2, Physical Properties table, Density row, metric value 8.850 gm/cubic cm
  - benchmark: melting_point
    label: Melting point, C-103
    value: 2350
    unit: °C
    scope: material
    conditions:
      grade: Niobium C-103
      tolerance: plus or minus 50 °C as printed
    method: Value printed in the physical properties table of the Smiths High Performance datasheet, with a tolerance of plus or minus 50 °C
    status: ground
    source: smiths-c103
    where: Page 2, Physical Properties table, Melting Point row, 2350 ± 50 °C
  - benchmark: thermal_conductivity
    label: Thermal conductivity, C-103 at 811 °C
    value: 38.1
    unit: W/(m·K)
    scope: material
    conditions:
      grade: Niobium C-103
      temperature: 811 °C (1600 °F)
      unit_in_source: 22.0 Btu/hr-ft2-°F/ft, with 38.1 printed in W/m°C
    method: Value printed in parentheses in the Smiths High Performance thermal properties table; W/m°C is numerically the same as W/(m·K)
    status: ground
    source: smiths-c103
    where: Page 2, Thermal Properties table, K column, 1600°F (811°C) row
  - benchmark: thermal_conductivity
    label: Thermal conductivity, C-103 at 1304 °C
    value: 44.7
    unit: W/(m·K)
    scope: material
    conditions:
      grade: Niobium C-103
      temperature: 1304 °C (2380 °F)
      unit_in_source: 25.8 Btu/hr-ft2-°F/ft, with 44.7 printed in W/m°C
    method: Value printed in parentheses in the Smiths High Performance thermal properties table; W/m°C is numerically the same as W/(m·K)
    status: ground
    source: smiths-c103
    where: Page 2, Thermal Properties table, K column, 2380°F (1304°C) row
  - benchmark: yield_strength
    label: Yield strength, C-103 at room temperature (minimum)
    value: 276
    unit: MPa
    scope: material
    conditions:
      grade: Niobium C-103
      temper: fully recrystallized
      atmosphere: air
      basis: minimum value
      unit_in_source: 40 ksi (276)
    method: Minimum value printed in the mechanical properties table of the Smiths High Performance datasheet, for tensile testing when fully recrystallized
    status: ground
    source: smiths-c103
    where: Page 2, Mechanical Properties (minimum) table, RT row, YS ksi (MPa) column
  - benchmark: yield_strength
    label: Yield strength, C-103 at 538 °C (minimum)
    value: 172
    unit: MPa
    scope: material
    conditions:
      grade: Niobium C-103
      temper: fully recrystallized
      atmosphere: vacuum
      temperature: 538 °C (1000 °F)
      basis: minimum value
      unit_in_source: 25 ksi (172)
    method: Minimum value printed in the mechanical properties table of the Smiths High Performance datasheet
    status: ground
    source: smiths-c103
    where: Page 2, Mechanical Properties (minimum) table, 1000°F (538°C) row, YS ksi (MPa) column
  - benchmark: yield_strength
    label: Yield strength, C-103 at 1093 °C (minimum)
    value: 124
    unit: MPa
    scope: material
    conditions:
      grade: Niobium C-103
      temper: fully recrystallized
      atmosphere: vacuum
      temperature: 1093 °C (2000 °F)
      basis: minimum value
      unit_in_source: 18 ksi (124)
    method: Minimum value printed in the mechanical properties table of the Smiths High Performance datasheet
    status: ground
    source: smiths-c103
    where: Page 2, Mechanical Properties (minimum) table, 2000°F (1093°C) row, YS ksi (MPa) column
  - benchmark: yield_strength
    label: Yield strength, C-103 at 1371 °C (minimum)
    value: 55
    unit: MPa
    scope: material
    conditions:
      grade: Niobium C-103
      temper: fully recrystallized
      atmosphere: vacuum
      temperature: 1371 °C (2500 °F)
      basis: minimum value
      unit_in_source: 8 ksi (55)
    method: Minimum value printed in the mechanical properties table of the Smiths High Performance datasheet
    status: ground
    source: smiths-c103
    where: Page 2, Mechanical Properties (minimum) table, 2500°F (1371°C) row, YS ksi (MPa) column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, C-103 at room temperature (minimum)
    value: 386
    unit: MPa
    scope: material
    conditions:
      grade: Niobium C-103
      temper: fully recrystallized
      atmosphere: air
      basis: minimum value
      unit_in_source: 56 ksi (386)
    method: Minimum value printed in the mechanical properties table of the Smiths High Performance datasheet
    status: ground
    source: smiths-c103
    where: Page 2, Mechanical Properties (minimum) table, RT row, UTS ksi (MPa) column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, C-103 at 1093 °C (minimum)
    value: 172
    unit: MPa
    scope: material
    conditions:
      grade: Niobium C-103
      temper: fully recrystallized
      atmosphere: vacuum
      temperature: 1093 °C (2000 °F)
      basis: minimum value
      unit_in_source: 25 ksi (172)
    method: Minimum value printed in the mechanical properties table of the Smiths High Performance datasheet
    status: ground
    source: smiths-c103
    where: Page 2, Mechanical Properties (minimum) table, 2000°F (1093°C) row, UTS ksi (MPa) column
  - benchmark: elongation
    label: Elongation at room temperature, C-103 (minimum)
    value: 20
    unit: '%'
    scope: material
    conditions:
      grade: Niobium C-103
      temper: fully recrystallized
      atmosphere: air
      basis: minimum value
    method: Minimum value printed in the mechanical properties table of the Smiths High Performance datasheet
    status: ground
    source: smiths-c103
    where: Page 2, Mechanical Properties (minimum) table, RT row, Elongation (%) column
  - benchmark: elongation
    label: Elongation at 1093 °C, C-103 (minimum)
    value: 30
    unit: '%'
    scope: material
    conditions:
      grade: Niobium C-103
      temper: fully recrystallized
      atmosphere: vacuum
      temperature: 1093 °C (2000 °F)
      basis: minimum value
    method: Minimum value printed in the mechanical properties table of the Smiths High Performance datasheet
    status: ground
    source: smiths-c103
    where: Page 2, Mechanical Properties (minimum) table, 2000°F (1093°C) row, Elongation (%) column
  - benchmark: elastic_modulus
    label: Young's modulus, C-103 at 20 °C
    value: 90
    unit: GPa
    scope: material
    conditions:
      grade: Niobium C-103
      temperature: 20 °C
      unit_in_source: 90 x 10 3 MPa
    method: Value printed in the physical properties at 20 °C section of the Stainless SA datasheet; 90 x 10 3 MPa is 90 GPa
    status: ground
    source: stainless-c103
    where: Physical properties at 20 °C, Young's modulus line
  - benchmark: density
    label: Density, Nb-1Zr
    value: 8.57
    unit: g/cm3
    scope: material
    conditions:
      grade: Nb-1Zr (UNS R04261)
      temperature: not stated in the ATI datasheet
    method: Value printed in the physical properties table of the ATI Nb1Zr datasheet, which says its data are typical
    status: ground
    source: ati-nb1zr
    where: Table 7, Physical Properties, Density row, 8.57 gms./cu. cm.
  - benchmark: melting_point
    label: Melting point, Nb-1Zr
    value: 2410
    unit: °C
    scope: material
    conditions:
      grade: Nb-1Zr (UNS R04261)
      tolerance: plus or minus 10 °C as printed
    method: Value printed in the physical properties table of the ATI Nb1Zr datasheet, with a tolerance of plus or minus 10 °C
    status: ground
    source: ati-nb1zr
    where: Table 7, Physical Properties, Melting Point row, 4365 ± 15 °F or 2410 ± 10 °C
  - benchmark: creep_time_to_1_percent_strain
    label: Time to 1 percent creep strain, FS-85 at 2000 °F
    value: 775
    unit: h
    scope: material
    conditions:
      grade: FS-85 (Cb + 28Ta + 10W + 1Zr), recrystallized sheet
      temperature: 2000 °F
      stress: 10000 psi
      atmosphere: vacuum, 10 to the minus 6 to 10 to the minus 7 torr
    method: Value printed in the summary of the NASA Lewis report TN D-2885, creep tested in vacuum
    status: ground
    note: The canonical property list has no creep-time name, so the snake_case name creep_time_to_1_percent_strain is used.
    source: nasa-fs85
    where: Summary, first paragraph, 1-percent strain being achieved in 775 hours
  - benchmark: creep_time_to_1_percent_strain
    label: Time to 1 percent creep strain, FS-85 at 2100 °F
    value: 355
    unit: h
    scope: material
    conditions:
      grade: FS-85 (Cb + 28Ta + 10W + 1Zr), recrystallized sheet
      temperature: 2100 °F
      stress: 10000 psi
      atmosphere: vacuum, 10 to the minus 6 to 10 to the minus 7 torr
    method: Value printed in the summary of the NASA Lewis report TN D-2885, creep tested in vacuum
    status: ground
    note: The canonical property list has no creep-time name, so the snake_case name creep_time_to_1_percent_strain is used.
    source: nasa-fs85
    where: Summary, first paragraph, 355 and 50 hours at 2100 and 2200 °F
  - benchmark: creep_time_to_1_percent_strain
    label: Time to 1 percent creep strain, FS-85 at 2200 °F
    value: 50
    unit: h
    scope: material
    conditions:
      grade: FS-85 (Cb + 28Ta + 10W + 1Zr), recrystallized sheet
      temperature: 2200 °F
      stress: 10000 psi
      atmosphere: vacuum, 10 to the minus 6 to 10 to the minus 7 torr
    method: Value printed in the summary of the NASA Lewis report TN D-2885, creep tested in vacuum
    status: ground
    note: The canonical property list has no creep-time name, so the snake_case name creep_time_to_1_percent_strain is used.
    source: nasa-fs85
    where: Summary, first paragraph, 355 and 50 hours at 2100 and 2200 °F
corrosion:
  - environment: Air at high temperature, uncoated niobium-base alloys
    headline: Niobium alloys oxidise in air above about 400 °C, so a protective coating is needed for hot service.
    effect: Wikipedia states that because niobium is oxidized at temperatures above 400 °C, a protective coating is necessary for these applications to prevent the alloy from becoming brittle. The same article says niobium oxidizes in Earth's atmosphere very slowly at lower temperatures.
    rating: severe
    conditions:
      basis: air; the 400 °C threshold is a general statement in the Wikipedia article, not a test at a stated exposure time
      alloy: niobium-base alloys, as a class
    source: wikipedia-niobium
    where: Alloys section, paragraph introducing the niobium-based alloys, with the statement about coatings and brittleness
  - environment: Hydrofluoric acid and hot alkali solutions
    headline: Hydrofluoric acid and hot alkali metal hydroxide solutions attack niobium.
    effect: Wikipedia states that niobium is attacked by hydrofluoric acid and hydrofluoric/nitric acid mixtures, and is also attacked by hot, saturated alkali metal hydroxide solutions.
    rating: moderate
    conditions:
      basis: general statement in the Wikipedia article; no concentration or temperature read for these attacks
      alloy: pure niobium as stated; the alloy grades were not tested for this in the sources read
    source: wikipedia-niobium
    where: Chemical properties, Corrosion paragraph
risks:
  hazards:
    - text: 'PubChem aggregates ECHA C&L notifications for niobium: H228 (Flammable solid, signal word Danger) appears in 34 % of the reports. The hazard applies to the element, not to a bulk alloy part.'
      ghs:
        - H228
      source: pubchem-niobium
      where: GHS Classification section, aggregated information from ECHA C&L notifications
    - text: The UVM copy of the Alfa Aesar niobium powder SDS classifies niobium as Flammable solids, Category 1 (H228), with signal word Danger and precautionary statement P210. This describes the powder form, not the bulk alloy.
      ghs:
        - H228
      source: uvm-niobium-sds
      where: Section 2.1 and 2.2, Flammable solids Category 1, H228, P210
  failure_risks:
    - mode: Air oxidation of unprotected niobium alloy at high temperature
      trigger: Exposure to air above about 400 °C without a protective coating
      consequence: Wikipedia states that the alloy becomes brittle without a protective coating. No exposure duration is printed in that statement.
      severity: critical
      source: wikipedia-niobium
      where: Alloys section, statement about oxidation above 400 °C and brittleness
    - mode: Interstitial gas pickup in C-103
      trigger: Oxygen, nitrogen, hydrogen or carbon above the maximum limits of the grade
      consequence: Wikipedia states that the reaction products with hydrogen, nitrogen and oxygen are frequently interstitial and nonstoichiometric. The Stainless SA datasheet sets maximum limits of 0.0225 mass % O, 0.0150 mass % N, 0.0010 mass % H and 0.015 mass % C.
      severity: moderate
      source: stainless-c103
      where: Typical chemical analysis table, maximum rows for Carbon, Hydrogen, Nitrogen and Oxygen
    - mode: Creep deformation of FS-85 at high temperature under load
      trigger: Load of 10000 psi at 2000 to 2200 °F in vacuum for hundreds of hours
      consequence: The NASA report shows 1 percent creep strain in 775 h at 2000 °F, 355 h at 2100 °F and 50 h at 2200 °F. The report says allowable creep strain, not rupture life, is the design limit for FS-85.
      severity: high
      source: nasa-fs85
      where: Summary, first paragraph; section on rupture and elongation, which notes FS-85 is very ductile
  side_effects: []
  handling:
    - text: Keep niobium powder away from heat and ignition sources, and use a Class D extinguisher, not water or foam (UVM SDS, P210 and Section 5.1).
      source: uvm-niobium-sds
      where: Section 2.2 P210, and Section 5.1 Extinguishing media
    - text: Specify the oxygen, nitrogen, hydrogen and carbon limits on the order. The Stainless SA datasheet gives the C-103 maxima.
      source: stainless-c103
      where: Typical chemical analysis table, maximum rows
  mitigations:
    - text: Heat treatment of FS-85 sheet in vacuum (1 h at 2600 °F, 10 to the minus 6 torr) gave a maximum contamination of 15 parts per million by weight, with no significant weight change. This was a lab check, not a service limit.
      source: nasa-fs85
      where: Material and specimen preparation section, weight-change paragraph
uses:
  - application: propulsion-and-tanks
    device: High-thrust rocket nozzle in C-103
    example: Smiths High Performance lists rockets and steering nozzles for missiles, and Stainless SA lists high-thrust rocket nozzles as the main application for C-103 up to 1480 °C.
    source: smiths-c103
    where: Applications list on page 1; Stainless SA C-103 introduction paragraph
  - application: propulsion-and-tanks
    device: Liquid-rocket thruster nozzle, Apollo Lunar Module descent engine
    example: Wikipedia states that C-103 is used for liquid-rocket thruster nozzles, including the descent engine of the Apollo Lunar Modules.
    source: wikipedia-niobium
    where: Alloys section, paragraph on C-103 and its uses
  - application: heat-shields
    device: Load-free thermal shield in Nb-1Zr
    example: ATI states that Nb1Zr can be used where a high-temperature material is needed with low loads, such as a load-free thermal shield, and that it is less expensive than the higher-strength alloys.
    source: ati-nb1zr
    where: Introduction, paragraph on applications
  - application: propulsion-and-tanks
    device: Containment for alkali liquid metals in space electric-power systems, FS-85
    example: NASA Lewis states that columbium alloys are of interest as containment materials for alkali liquid metals in advanced space electric-power systems, and that FS-85 was tested for those long-duration, high-temperature conditions.
    source: nasa-fs85
    where: Introduction, first paragraph
supply:
  - subject: Niobium (mine production, feedstock for all three alloys)
    producers:
      - country: Brazil
        share_percent: 93
        year: 2025
      - country: Canada
        share_percent: 5
        year: 2025
    critical_lists: []
    recycling: The USGS says niobium was recycled when niobium-bearing steels and superalloys were recycled, but scrap recovery was small.
    substitutes:
      - 'USGS: ceramic matrix composites, molybdenum, tantalum and tungsten in high-temperature superalloy applications, with performance loss or higher cost possible.'
    source: usgs-mcs2026-niobium
    where: Events, Trends and Issues paragraph (Brazil about 93 %, Canada 5 %); World Mine Production and Reserves table (Brazil 104,000 t, 2025); Substitutes paragraph
  - subject: Niobium (United States import dependence)
    abundance: 'USGS: world resources of niobium are more than adequate to supply projected needs; most identified resources are pyrochlore in carbonatite deposits outside the United States.'
    producers:
      - country: Brazil (ferroniobium and niobium metal imports)
        share_percent: 65
        year: 2024
      - country: Canada (ferroniobium and niobium metal imports)
        share_percent: 31
        year: 2024
    critical_lists: []
    source: usgs-mcs2026-niobium
    where: Net import reliance row (100 % in 2025); Import Sources paragraph (Brazil 65 %, Canada 31 % of ferroniobium and niobium metal imports); World Resources paragraph
documents:
  - title: Smiths High Performance technical datasheet, Niobium C-103, revision 18.02.2025
    type: datasheet
    url: https://www.smithshp.com/assets/pdf/niobium/niobium-c-103-english.pdf
    year: 2025
  - title: Stainless SA datasheet, Niobium C-103 (UNS R04295)
    type: datasheet
    url: https://www.stainless.eu/wp-content/uploads/2024/11/Niobium-C103%C2%AE-EN.pdf
  - title: ATI Nb1Zr Alloy Technical Data Sheet (UNS R04261), version 1, 2012
    type: datasheet
    url: https://www.atimaterials.com/Products/Documents/datasheets/niobium-hafnium-tantalum-vanadium/niobium/niobium_1zr_alloy_v1.pdf
    year: 2012
  - title: NASA TN D-2885, Creep Behavior of a Columbium Alloy, FS-85, Titran and Hall, Lewis Research Center
    type: report
    url: https://ntrs.nasa.gov/api/citations/19650017052/downloads/19650017052.pdf
    year: 1965
  - title: 'USGS Mineral Commodity Summaries 2026: Niobium (Columbium)'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf
    year: 2026
  - title: 'Wikipedia: Niobium'
    type: database
    url: https://en.wikipedia.org/wiki/Niobium
    year: 2026
  - title: UVM copy of Alfa Aesar niobium powder safety data sheet (revision 2, 19 February 2021)
    type: sds
    url: https://www.uvm.edu/cosmolab/msds/niobiumpowdermsds.pdf
    year: 2021
  - title: PubChem compound record for niobium (CID 23936), GHS classification
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23936/JSON?heading=GHS+Classification
gaps:
  - 'Nb-1Zr room and elevated temperature tensile and yield strengths: the ATI datasheet mechanical table (Table 8) did not come through in the text extract, and no other Nb-1Zr datasheet with minimum values was opened in this run. The search snippets for a B392 listing were not used.'
  - 'Nb-1Zr Young''s modulus: ATI prints 10 x 10^6 psi (estimated) at room temperature. The PDF text extract shows the exponent as 106, so the value could not be matched against the source text and was not entered.'
  - 'Nb-Ta alloy: no datasheet for a specific Nb-Ta grade (for example Nb-10Ta) was read in this run. The search results gave only tantalum-rich KBI-type alloys and a theoretical 50:50 value, which were not used.'
  - 'FS-85 density, tensile and yield strength: the NASA TN D-2885 report covers creep only, and no other FS-85 datasheet was opened. FS-85 designation codes other than the trade name are not listed.'
  - Creep rows use the snake_case name creep_time_to_1_percent_strain, which is not in the property canon. Units are hours (h).
  - C-103 coefficient of thermal expansion and the thermal conductivity range from the Stainless SA datasheet are printed with decimal commas in the source text, so they were not entered.
  - Nb-1Zr thermal conductivity (24.2 BTU/(hr) (ft2) (°F/ft) at 25 °C) and specific heat (0.065 BTU/°F/lb) are printed in BTU units that the site unit registry does not hold, so they were not entered.
  - Stainless SA prints a C-103 density of 8.86 g/cm3, against 8.850 g/cm3 in the Smiths datasheet. Only the Smiths value is entered.
  - No atomic oxygen erosion, outgassing or total mass loss data for these alloys in space were found in the sources read.
  - Hafnium and titanium atomic weights were not read from NIST in this run, so the recipe gives only shares for those two elements.
  - 'Critical-mineral list status: the USGS 2026 niobium summary prints no critical-mineral list, and the EU critical raw materials list was not opened, so critical_lists is empty.'
  - Hazard data (PubChem, UVM SDS) describe elemental niobium and its powder. No hazard statement was found for bulk FS-85 or Nb-1Zr.
  - 'Mine production process, smelting of niobium concentrates: not read from a primary source.'
sources:
  smiths-c103:
    title: Niobium C-103 technical datasheet, Smiths High Performance, revision 18.02.2025
    id: Related specifications ASTM B652, B654, B655, AMS 7852, AMS 7857; C-103 a proprietary product of Materion
    url: https://www.smithshp.com/assets/pdf/niobium/niobium-c-103-english.pdf
    year: 2025
    kind: datasheet
    license: supplier datasheet (cited, not reproduced)
  stainless-c103:
    title: Niobium C-103 (UNS R04295) technical datasheet, Stainless SA, Dannemarie-sur-Crete
    id: UNS R04295; ASTM B652, B654, B655; AMS 7852, AMS 7857
    url: https://www.stainless.eu/wp-content/uploads/2024/11/Niobium-C103%C2%AE-EN.pdf
    kind: datasheet
    license: manufacturer datasheet (cited, not reproduced)
  ati-nb1zr:
    title: ATI Nb1Zr Alloy (Type 3 and 4) Technical Data Sheet, Allegheny Technologies, version 1 (2012)
    id: UNS R04261
    url: https://www.atimaterials.com/Products/Documents/datasheets/niobium-hafnium-tantalum-vanadium/niobium/niobium_1zr_alloy_v1.pdf
    year: 2012
    kind: datasheet
    license: manufacturer datasheet, data typical (cited, not reproduced)
  nasa-fs85:
    title: NASA TN D-2885, High-Temperature Creep Behavior of a Columbium Alloy, FS-85, Titran and Hall, Lewis Research Center
    id: NASA NTRS 19650017052
    url: https://ntrs.nasa.gov/api/citations/19650017052/downloads/19650017052.pdf
    year: 1965
    kind: report
    license: NASA public document
  usgs-mcs2026-niobium:
    title: Mineral Commodity Summaries 2026, Niobium (Columbium), February 2026
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  wikipedia-niobium:
    title: Niobium, Wikipedia (chemical properties, alloys, production and applications)
    url: https://en.wikipedia.org/wiki/Niobium
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  uvm-niobium-sds:
    title: Safety data sheet, niobium powder (Alfa Aesar product ALFAA40510), copy hosted by the University of Vermont, revision 2
    id: CAS 7440-03-1, EC 231-113-5, revision 19-Feb-2021
    url: https://www.uvm.edu/cosmolab/msds/niobiumpowdermsds.pdf
    year: 2021
    kind: datasheet
    license: supplier safety data sheet (cited, not reproduced)
  pubchem-niobium:
    title: 'PubChem compound record: Niobium (CID 23936), GHS Classification section'
    id: CID 23936, ECHA C&L Inventory aggregated notifications
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23936/JSON?heading=GHS+Classification
    kind: database
    license: PubChem (NCBI), public domain; sections attributed to ECHA
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 18
  unreachable: 0
  caveats: 3
  note: 'Values were read by an AI assistant on 2026-10-26 from the pages and PDFs named in each entry (PDFs extracted with pdftotext). Caveats: the C-103 mechanical values are minimums from one datasheet (Smiths), not typical values; the FS-85 values are creep times from a 1965 NASA report, not tensile or yield data; the Nb-Ta grade is not covered by a read datasheet.'
story:
  recipe:
    line: Niobium alloys are body-centred cubic niobium with small additions. C-103 is Nb with 9.0 to 11.0 mass % hafnium and 0.7 to 1.3 mass % titanium, plus maximum 0.7 % zirconium and 0.5 % each of tantalum and tungsten (Stainless SA chemical analysis). Nb-1Zr is niobium with 1 % zirconium (ATI). FS-85 is nominally Cb + 28Ta + 10W + 1Zr (NASA). Electron beam melting under vacuum is the method used by the two major niobium distributors (Wikipedia), because the metal reacts with oxygen and must be worked in vacuum.
    parts:
      - name: Niobium
        symbol: Nb
        atoms: 1
        atomic_weight: 92.906
        role: The base metal in all three alloys. The density and melting point of unalloyed niobium are in the niobium profile, not here.
      - name: Hafnium
        symbol: Hf
        share_note: 9.0 to 11.0 mass % in C-103 (Stainless SA)
        role: Alloying element in C-103 (Stainless SA lists it as the main alloying addition).
      - name: Titanium
        symbol: Ti
        share_note: 0.7 to 1.3 mass % in C-103 (Stainless SA)
        role: Minor alloying addition in C-103.
      - name: Zirconium
        symbol: Zr
        share_note: 1 % in Nb-1Zr (ATI); 1 in the FS-85 name (NASA)
        role: Creep strengthener, which ATI says greatly improved the creep strength of pure niobium.
      - name: Tantalum
        symbol: Ta
        share_note: 28 in the FS-85 name (NASA), nominal
        role: Alloying element in FS-85 (NASA).
      - name: Tungsten
        symbol: W
        share_note: 10 in the FS-85 name (NASA), nominal
        role: Alloying element in FS-85 (NASA).
  risk_groups:
    - title: For people
      lead: The powder is a flammable solid in the supplier safety data sheet. Bulk alloy parts have no hazard statement in the sources read.
      level: 1
      verdict: Flammable as powder, not hazardous as bulk alloy
      points:
        - label: Niobium powder
          line: The UVM copy of the Alfa Aesar safety data sheet classifies niobium powder as Flammable solid, Category 1 (H228), with the signal word Danger. PubChem's ECHA aggregate shows H228 in 34 % of the reports.
        - label: Bulk alloy
          line: No hazard statement was found in the sources read for C-103, Nb-1Zr or FS-85 in bulk form.
    - title: If it fails
      lead: The failure routes here are oxidation in air and gas pickup. The sources give no space test of either.
      points:
        - label: Oxidation
          line: The alloys need a protective coating above about 400 °C in air, or they become brittle (Wikipedia).
        - label: Gas pickup
          line: C-103 has maximum limits of 0.0225 mass % oxygen, 0.0150 mass % nitrogen and 0.0010 mass % hydrogen (Stainless SA).
  why: Niobium alloys keep strength at temperatures where most metals soften. C-103 keeps a minimum yield strength of 124 MPa at 1093 °C in vacuum (Smiths). Nb-1Zr is the older, cheaper grade for low-load parts, and ATI says it has been replaced in some applications by C-103 (ATI). FS-85 was tested by NASA Lewis for alkali-metal containment in space power systems, where 1 percent creep strain took 775 h at 2000 °F and 10,000 psi (NASA TN D-2885).
  uses:
    - where: Rocket nozzles
      line: C-103 is the thruster nozzle alloy for rockets and steering nozzles for missiles (Smiths, Stainless SA). Wikipedia names the Apollo Lunar Module descent engine.
    - where: Thermal shields
      line: ATI says Nb-1Zr is used for load-free thermal shields where a high-temperature material with low loads is needed.
    - where: Space power containment
      line: NASA Lewis tested FS-85 for containment of alkali liquid metals in space electric-power systems.
  can_do:
    - label: Carry load when hot
      value: 124 MPa yield at 1093 °C
      benchmark: yield_strength
      line: The minimum yield strength of recrystallized C-103 in vacuum is 124 MPa at 1093 °C, and 55 MPa at 1371 °C (Smiths).
    - label: Carry heat
      value: 38.1 W/(m·K) at 811 °C
      benchmark: thermal_conductivity
      line: C-103 has a thermal conductivity of 38.1 W/(m·K) at 811 °C and 44.7 W/(m·K) at 1304 °C (Smiths, printed as W/m°C).
    - label: Weight
      value: 8.85 g/cm3
      benchmark: density
      line: C-103 has a density of 8.85 g/cm3 at 20 °C (Smiths). Nb-1Zr has 8.57 g/cm3 (ATI).
    - label: Melting
      value: 2350 °C
      benchmark: melting_point
      line: C-103 melts at 2350 plus or minus 50 °C (Smiths). Nb-1Zr melts at 2410 plus or minus 10 °C (ATI).
  compare: Nb-1Zr is the cheaper, lower-strength grade. ATI says it is less expensive than the higher-strength alloys and is used where loads are low (ATI). C-103 is the stronger grade, with a minimum yield strength of 124 MPa at 1093 °C in vacuum (Smiths). FS-85 has no yield or tensile value in the report read, only creep times. The three rows below compare density, melting point and Young's modulus for the grades that have a value in the sources read.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Young's modulus
      benchmark: elastic_modulus
  handling:
    - Specify the oxygen, nitrogen, hydrogen and carbon limits on the order, as the C-103 datasheet does.
    - Keep niobium powder away from heat and ignition sources, and use a Class D extinguisher (UVM SDS).
    - Protect the alloys with a coating for any service above about 400 °C in air (Wikipedia).
  good_for:
    - 'High-temperature load in vacuum: 124 MPa minimum yield at 1093 °C for recrystallized C-103 (Smiths).'
    - 'Thruster and missile nozzles: C-103 is the alloy named for rocket and steering nozzles (Smiths, Stainless SA).'
    - 'Low-load thermal shields: Nb-1Zr at lower cost than C-103 (ATI).'
  watch_out:
    - 'Oxidation: all three need a protective coating for hot service in air (Wikipedia).'
    - 'Creep: FS-85 reaches 1 percent creep strain in 50 h at 2200 °F and 10,000 psi (NASA).'
    - 'Supply: Brazil mines about 93 % of world niobium, and the United States is 100 % net import reliant (USGS 2026).'
    - No space outgassing, erosion yield or radiation data for these alloys were found in the sources read.
  verdict: The niobium alloys C-103 and Nb-1Zr are the proven choices for hot structures in space hardware, with C-103 the stronger of the two (124 MPa minimum yield at 1093 °C in vacuum). They all oxidise in air above about 400 °C and need a coating, and the sources read give no tensile values for FS-85 and no Nb-Ta grade datasheet. Supply is concentrated in Brazil.