PH 15-7 Mo stainless steel 15-7 PH

spore: profile
id: stainless-15-7ph
spore_version: 0.2
family: stainless-precipitation-hardening
name: PH 15-7 Mo stainless steel
abbreviation: 15-7 PH
role: Semi-austenitic precipitation-hardening stainless steel for high-strength springs, rings and aircraft parts
category: metals
type: steels-and-stainless
summary: |
  PH 15-7 Mo (UNS S15700, AISI Type 632, AMS 5520) is a chromium-nickel-molybdenum-aluminium stainless steel that is formed in a soft austenitic condition (Condition A) and then hardened by low-temperature heat treatment. The ATI datasheet prints a density of 7.67 g/cm3 for the RH 950 and TH 1050 conditions and 7.80 g/cm3 for Condition A, and an RH 950 yield strength of 220,000 psi (1515 MPa) with an ultimate tensile strength of 245,000 psi (1690 MPa). The Ulbrich datasheet gives a Condition C minimum tensile strength of 200 ksi (1380 MPa). The 1969 NASA test in 3.5 percent salt solution found the alloy susceptible to stress corrosion cracking in every condition except CH 900.
best_for: Springs, retaining rings and seal rings that need high strength with a low-distortion hardening heat treatment (ATI and Ulbrich list these uses)
weakest_at: 'Stress corrosion cracking in salt water: the 1969 NASA test found the alloy cracked in all conditions except CH 900, and corrosion resistance is below Type 304 (ATI)'
identity:
  formula: Fe balance; Cr 14.00-16.00, Ni 6.50-7.75, Mo 2.00-3.00, Al 0.75-1.50, C 0.09 max, Mn 1.00 max, Si 1.00 max, P 0.040 max, S 0.030 max (wt %, AMS 5520 chemistry as printed)
  source: ati-15-7
  where: Chemical in Weight Percent per AMS 5520 table; the same limits are printed by Ulbrich and Aircraft Materials
  designations:
    - system: UNS
      code: S15700
      source: ati-15-7
      where: Introduction, grade line '(S15700, AISI Type 632)'
    - system: AISI
      code: '632'
      source: ati-15-7
      where: Introduction, 'AISI Type 632'
    - system: AMS
      code: '5520'
      note: sheet, strip and plate
      source: ati-15-7
      where: Specifications and Certificates table
    - system: AMS
      code: '5657'
      note: bars and forgings
      source: ati-15-7
      where: Specifications and Certificates table
    - system: ASTM
      code: A693
      note: plate, sheet and strip
      source: ulbrich-15-7mo
      where: Header line 'AMS 5520, ASTM A693'
    - system: ASTM
      code: A 564
      note: bars, wire and shapes
      source: ati-15-7
      where: Specifications and Certificates table
    - system: EN
      code: '1.4532'
      note: page lists the composition band Cr 14.0-16.0 and Al 0.70-1.50; Ni and Mo limits are not printed on that page
      source: totalmateria-1055880
      where: Page title 'EN 1.4532 Stainless steels' and composition table
tags:
  environments: []
  stresses: []
  applications:
    - structures
    - mechanisms
properties:
  - benchmark: density
    label: Density, Condition A
    value: 7.8
    unit: g/cm3
    scope: material
    conditions:
      condition: A (annealed, mostly austenite)
      unit_in_source: 0.280 lbs/in3 in the Ulbrich datasheet; 0.282 lbs/in3 in the ATI datasheet
    method: Value printed in the Ulbrich datasheet (typical values, revision 2015)
    status: ground
    source: ulbrich-15-7mo
    where: 'Physical Properties, ''Density: (Cond. A), 0.280 lbs/in3, 7.80 g/cm3'''
  - benchmark: density
    label: Density, RH 950 condition
    value: 7.67
    unit: g/cm3
    scope: material
    conditions:
      condition: RH 950 (precipitation-hardened from Condition A via sub-zero conditioning)
      unit_in_source: 0.277 lbs/in3
    method: Value printed in the ATI typical-values datasheet (2014)
    status: ground
    source: ati-15-7
    where: Physical Properties table, Density row, RH 950 column
  - benchmark: elastic_modulus
    label: Modulus of elasticity, all conditions (ATI typical)
    value: 28
    unit: 10^6 psi
    scope: material
    conditions:
      condition: Conditions A, RH 950 and TH 1050 (the same value is printed for each)
      test: tension
      unit_in_source: 28 x 10^6 psi printed; the metric value (195) is printed in parentheses without a unit label
    method: Typical value printed in the ATI datasheet; the datasheet says data are typical and not for design
    status: ground
    source: ati-15-7
    where: Mechanical Properties, Elastic Modulus (Typical Values) table
  - benchmark: elastic_modulus
    label: Modulus of elasticity (Ulbrich)
    value: 200
    unit: GPa
    scope: material
    conditions:
      test: tension
      unit_in_source: 29.0 x 10^3 ksi (200 x 10^3 MPa)
      condition: not stated; the page gives one value
    method: Value printed in the Ulbrich datasheet; differs from the ATI value (28 x 10^6 psi) by about 2 percent
    status: ground
    source: ulbrich-15-7mo
    where: Modulus of Elasticity section
  - benchmark: cte
    label: Mean coefficient of thermal expansion, Condition A, 21 to 93 C
    value: 14.4
    unit: 10^-6/C
    scope: material
    conditions:
      condition: A
      temperature_range: 70 to 200 F (21 to 93 C)
      unit_in_source: 8.0 x 10^-6 per degF
    method: Mean coefficient printed in the ATI datasheet; Ulbrich prints the same value in its own table
    status: ground
    source: ati-15-7
    where: Physical Properties, Linear Coefficient of Thermal Expansion, Condition A, 70 to 200 F row
  - benchmark: cte
    label: Mean coefficient of thermal expansion, RH 950, 21 to 316 C
    value: 10.1
    unit: 10^-6/C
    scope: material
    conditions:
      condition: RH 950
      temperature_range: 70 to 600 F (21 to 316 C)
      unit_in_source: 5.6 x 10^-6 per degF
    method: Mean coefficient printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Physical Properties, Linear Coefficient of Thermal Expansion, RH 950, 70 to 600 F row
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 93 C
    value: 16.2
    unit: W/m-K
    scope: material
    conditions:
      temperature: 200 F (93 C)
      condition: not stated in the source
      unit_in_source: 112 BTU/hr/ft2/in/degF
    method: Value printed in the Ulbrich datasheet alongside the BTU value
    status: ground
    source: ulbrich-15-7mo
    where: Physical Properties, Thermal Conductivity, at 200 F (93 C) row
  - benchmark: electrical_resistivity
    label: Electrical resistivity, annealed or hardened
    value: 82
    unit: microhm-cm
    scope: material
    conditions:
      condition: annealed or hardened (the source gives one value for both)
      qualifier: printed as approximately
    method: Value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Physical Properties, Electrical Resistivity row
  - benchmark: yield_strength
    label: 0.2 percent yield strength, Condition A
    value: 380
    unit: MPa
    scope: material
    conditions:
      condition: A (annealed)
      form: sheet and strip
      unit_in_source: 55,000 psi
    method: Typical room-temperature value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), Sheet and Strip, 0.2% Yield Strength row, Condition A column
  - benchmark: yield_strength
    label: 0.2 percent yield strength, RH 950
    value: 1515
    unit: MPa
    scope: material
    conditions:
      condition: RH 950
      form: sheet and strip
      heat_treatment: solution treat 1950 F, air cool; austenite conditioning at 1750 F, hold 10 minutes, then sub-zero at -100 F for 8 hours; precipitation harden at 950 F for 90 minutes (Aircraft Materials, ATI)
      unit_in_source: 220,000 psi
    method: Typical room-temperature value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), Sheet and Strip, 0.2% Yield Strength row, RH 950 column
  - benchmark: yield_strength
    label: 0.2 percent yield strength, TH 1050
    value: 1380
    unit: MPa
    scope: material
    conditions:
      condition: TH 1050
      form: sheet and strip
      heat_treatment: austenite conditioning at 1400 F for 90 minutes; precipitation harden at 1050 F for 90 minutes (ATI)
      unit_in_source: 200,000 psi
    method: Typical room-temperature value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), 0.2% Yield Strength row, TH 1050 column
  - benchmark: yield_strength
    label: 0.2 percent yield strength at 316 C, RH 950
    value: 1225
    unit: MPa
    scope: material
    conditions:
      condition: RH 950
      temperature: 600 F (316 C)
      test: short-time tension, S15700
      unit_in_source: 178,000 psi
    method: Short-time elevated-temperature value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Elevated Temperature Properties, 600 F row, RH 950 S15700 column
  - benchmark: yield_strength
    label: 0.2 percent yield strength, Condition C minimum
    value: 1205
    unit: MPa
    scope: material
    conditions:
      condition: C (cold worked, martensitic before ageing)
      unit_in_source: 175 ksi min
    bound: lower
    method: Minimum value printed in the Ulbrich datasheet
    status: ground
    source: ulbrich-15-7mo
    where: 'Properties: Condition C, Yield Strength row'
  - benchmark: ultimate_tensile_strength
    label: Ultimate tensile strength, Condition A
    value: 860
    unit: MPa
    scope: material
    conditions:
      condition: A (annealed)
      form: sheet and strip
      unit_in_source: 125,000 psi
    method: Typical room-temperature value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), Ultimate Tensile Strength row, Condition A column
  - benchmark: ultimate_tensile_strength
    label: Ultimate tensile strength, RH 950
    value: 1690
    unit: MPa
    scope: material
    conditions:
      condition: RH 950
      form: sheet and strip
      unit_in_source: 245,000 psi
    method: Typical room-temperature value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), Ultimate Tensile Strength row, RH 950 column
  - benchmark: ultimate_tensile_strength
    label: Ultimate tensile strength, TH 1050
    value: 1450
    unit: MPa
    scope: material
    conditions:
      condition: TH 1050
      form: sheet and strip
      unit_in_source: 210,000 psi
    method: Typical room-temperature value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), Ultimate Tensile Strength row, TH 1050 column
  - benchmark: ultimate_tensile_strength
    label: Ultimate tensile strength, Condition C minimum
    value: 1380
    unit: MPa
    scope: material
    conditions:
      condition: C (cold worked)
      unit_in_source: 200 KSI min
    bound: lower
    method: Minimum value printed in the Ulbrich datasheet
    status: ground
    source: ulbrich-15-7mo
    where: 'Properties: Condition C, Ultimate Tensile Strength row'
  - benchmark: ultimate_tensile_strength
    label: Ultimate tensile strength, RH 950 (Aircraft Materials, 0.020 to 0.1875 in)
    value: 225
    unit: ksi
    scope: material
    conditions:
      condition: RH 950 (AMS 5520)
      thickness: 0.020 to 0.1875 in
      note: Aircraft Materials labels this alloy 15-7 Mo; the RH 950 value is 20 ksi below the ATI typical value of 245,000 psi
    method: Value printed in a typical-properties table (not a specification minimum)
    status: ground
    source: aircraftmaterials-15-7
    where: Typical Mechanical Properties table, Alloy 15-7 Mo, RH950 (AMS 5520), 0.020-0.1875 row
  - benchmark: elongation
    label: Elongation, Condition A
    value: 30
    unit: '%'
    scope: material
    conditions:
      condition: A (annealed)
      form: sheet and strip
      gauge: in 2 in
    method: Typical value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), Elongation row, Condition A column
  - benchmark: elongation
    label: Elongation, RH 950
    value: 6
    unit: '%'
    scope: material
    conditions:
      condition: RH 950
      form: sheet and strip
      gauge: in 2 in
    method: Typical value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), Elongation row, RH 950 column
  - benchmark: hardness
    label: Hardness, Condition A
    value: 88
    unit: HRB
    scope: material
    conditions:
      condition: A (annealed)
      form: sheet and strip
    method: Typical value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), Hardness Rockwell B row, Condition A column
  - benchmark: hardness
    label: Hardness, RH 950
    value: 48
    unit: HRC
    scope: material
    conditions:
      condition: RH 950
      form: sheet and strip
    method: Typical value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), Hardness Rockwell C row, RH 950 column
  - benchmark: hardness
    label: Hardness, TH 1050
    value: 43
    unit: HRC
    scope: material
    conditions:
      condition: TH 1050
      form: sheet and strip
    method: Typical value printed in the ATI datasheet
    status: ground
    source: ati-15-7
    where: Room Temperature Properties (Typical Values), Hardness Rockwell C row, TH 1050 column
corrosion:
  - environment: 3.5 percent salt solution, alternate immersion (general service of space vehicles before launch, as described by NASA)
    headline: In the 1969 NASA test, PH 15-7 Mo cracked under stress in every condition except CH 900, which the report calls reportedly highly resistant.
    effect: The report ranks PH 15-7 Mo and 17-7 PH as susceptible to stress corrosion cracking in all conditions except 17-7 PH CH 900. The authors add that PH 15-7 Mo is reportedly highly resistant in CH 900, and that PH 15-7 Mo is more resistant than 17-7 PH and the TH condition is more resistant than RH. Transverse grain direction was more susceptible than longitudinal, and hardening at 950 F was more susceptible than 1100 F.
    rating: severe
    conditions:
      exposure: alternate immersion in 3.5 percent salt solution
      stress: loaded specimens; load levels are in the full report
      product_forms: sheet and bar
    source: nasa-tm-53910
    where: Abstract, results paragraph; Conclusion 2; Discussion of PH 15-7 Mo and 17-7 PH
  - environment: General corrosion in service (no test condition given in the source)
    headline: Corrosion resistance is better than the 400-series hardenable stainless steels and not quite as good as Type 304.
    effect: Ulbrich says the TH 1050 and RH 950 conditions are superior to Alloys 410, 420 and 431 and not quite as good as 304, and refers users to NACE for recommendations. ATI says the alloy approaches Type 304 in most media and is superior to the hardenable 400-series grades. Neither source prints a corrosion rate.
    rating: moderate
    conditions:
      basis: qualitative statements in two datasheets; no test data printed
    source: ulbrich-15-7mo
    where: Additional Properties, Corrosion Resistance
risks:
  hazards:
    - text: PubChem's GHS summary for nickel metal (an element, not this alloy) lists H317 (may cause an allergic skin reaction), H351 (suspected of causing cancer), H372 (causes damage to organs through prolonged or repeated exposure) and H412. No alloy-specific safety data sheet for 15-7 PH was opened in this run.
      ghs:
        - H317
        - H351
        - H372
        - H412
      source: pubchem-nickel
      where: GHS Hazard Statements, CID 935 (Nickel)
  failure_risks:
    - mode: Stress corrosion cracking in salt water
      trigger: Tensile stress with exposure to 3.5 percent salt solution (alternate immersion, 1969 NASA test)
      consequence: The 1969 test found cracking in every heat-treated condition except CH 900, so part life can be shorter than the strength suggests in a salt environment.
      severity: high
      source: nasa-tm-53910
      where: Abstract; Conclusion 2
    - mode: Low ductility in the cold-worked condition
      trigger: Use in Condition C (cold worked and aged, the highest-strength condition)
      consequence: Ulbrich prints a minimum elongation of 1 percent for Condition C, so the part has little ability to yield before fracture.
      severity: moderate
      source: ulbrich-15-7mo
      where: 'Properties: Condition C, Elongation row'
  side_effects:
    - text: Molybdenum raises the ferrite content of the weld deposit compared with ATI 17-7 PH, according to ATI.
      affects: Welded joints
      source: ati-15-7
      where: Weldability section
    - text: 'Magnetic permeability changes with condition: weakly ferromagnetic when annealed and strongly ferromagnetic when heat treated, according to Ulbrich and ATI.'
      affects: Parts that must be non-magnetic or that sit near magnetic sensors
      source: ati-15-7
      where: Physical Properties, Magnetic Permeability row
  handling:
    - text: Inert-gas welding protects the aluminium that the precipitation reaction depends on; ATI says this is why inert-gas methods are used.
      source: ati-15-7
      where: Weldability section
    - text: Ulbrich refers welders to the SSINA publication 'Welding of Stainless Steels and Other Joining Methods' for best results.
      source: ulbrich-15-7mo
      where: Welding section
  mitigations:
    - text: ATI says the alloy needs no preheat or post-weld anneal, unlike conventional hardenable stainless steels.
      source: ati-15-7
      where: Weldability section
uses:
  - application: mechanisms
    device: Springs and spring-type parts
    example: ATI says the alloy has been used in aerospace and many spring-type applications that need high strength.
    source: ati-15-7
    where: Introduction
  - application: mechanisms
    device: Seal rings and retaining rings
    example: Ulbrich lists seal rings, retaining rings and springs among its applications for 15-7Mo.
    source: ulbrich-15-7mo
    where: Applications list
  - application: structures
    device: Aircraft components
    example: Ulbrich lists aircraft components as an application; ATI describes the alloy as used in aerospace.
    source: ulbrich-15-7mo
    where: Applications list
supply:
  - subject: Chromium
    producers:
      - country: South Africa
        share_percent: 45.1
        year: 2025
      - country: Turkey
        share_percent: 17.6
        year: 2025
      - country: Kazakhstan
        share_percent: 13.7
        year: 2025
      - country: India
        share_percent: 5.9
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (listed as 'Chromium, used in stainless steel')
        listed: true
      - list: EU critical raw materials list (chromium not mentioned on the Commission page)
        listed: false
    recycling: 'USGS: recycled chromium from stainless-steel scrap accounted for 21 percent of apparent consumption in 2025.'
    substitutes:
      - 'USGS: chromium has no substitute in stainless steel, the leading end use.'
    source: usgs-mcs2026-chromium
    where: 'World Mine Production table, 2025e (world total 51,000 as printed; shares calculated by Space Mushroom); Recycling; Substitutes. Critical list: USGS 2025 List page.'
  - subject: Nickel
    producers:
      - country: Indonesia
        share_percent: 66.7
        year: 2025
      - country: Philippines
        share_percent: 6.9
        year: 2025
      - country: Russia
        share_percent: 5.1
        year: 2025
      - country: Canada
        share_percent: 3.6
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (listed as 'Nickel, used to make high-strength steel, and rechargeable batteries')
        listed: true
      - list: EU critical raw materials list (the Commission page says nickel is included as a strategic raw material, though it does not meet the CRM thresholds)
        listed: true
    recycling: 'USGS: nickel recovered from scrap accounted for about 60 percent of apparent consumption in 2025.'
    substitutes:
      - 'USGS: low-nickel, duplex or ultrahigh-chromium stainless steels have been substituted for austenitic grades in construction.'
    source: usgs-mcs2026-nickel
    where: 'World Mine Production table, 2025e (world total 3,900,000 as printed; shares calculated by Space Mushroom); Recycling; Substitutes. Critical list: USGS 2025 List page and EU Commission page.'
  - subject: Molybdenum
    producers:
      - country: China
        share_percent: 37.3
        year: 2025
      - country: Chile
        share_percent: 16.2
        year: 2025
      - country: United States
        share_percent: 15.4
        year: 2025
      - country: Peru
        share_percent: 15
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (molybdenum not listed)
        listed: false
      - list: EU critical raw materials list (molybdenum not mentioned on the Commission page)
        listed: false
    recycling: 'USGS: molybdenum is recycled through catalysts, ferrous scrap and superalloy scrap; recycled molybdenum may be as much as 30 percent of apparent supply.'
    substitutes:
      - 'USGS: there is little substitution for molybdenum in steels; potential substitutes include boron, chromium, niobium and vanadium.'
    source: usgs-mcs2026-molybdenum
    where: World Mine Production table, 2025e (world total 260,000 as printed; shares calculated by Space Mushroom); Recycling; Substitutes
documents:
  - title: ATI 15-7 Technical Data Sheet (Semi-Austenitic Stainless Steel, UNS S15700), version 1
    type: datasheet
    url: https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/precipitationhardening/ati_15-7_tds_en_v2.pdf
    year: 2014
  - title: Ulbrich 15-7 MO Stainless Steel, UNS S15700 (wire, bar and sheet datasheet)
    type: datasheet
    url: https://www.ulbrich.com/uploads/data-sheets/15-7-MO-Stainless-Steel-Wire-UNS-S15700.pdf
    year: 2015
  - title: 'NASA Technical Memorandum: Stress Corrosion Cracking Evaluation of Several Precipitation Hardening Stainless Steels (Report No. 53910)'
    type: report
    url: https://ntrs.nasa.gov/api/citations/19690028850/downloads/19690028850.pdf
    year: 1969
  - title: PubChem compound record, Nickel (CID 935), GHS classification
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Nickel
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Chromium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Nickel'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Molybdenum'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf
    year: 2026
gaps:
  - No melting range found for 15-7 Mo in a source opened in this run (the ATI and Ulbrich datasheets do not print one).
  - No alloy-specific safety data sheet for 15-7 PH was opened. The hazard entry rests on PubChem's element-level GHS summary for nickel; the chromium and welding-fume hazards for this alloy were not verified.
  - The EN name (X8CrNiMoAl15-7-2) was not printed as this grade's name on the source page; only the EN 1.4532 number is listed, with the composition note.
  - Modulus and RH 950 strength differ between sources (ATI 28 x 10^6 psi; Ulbrich 200 GPa; Aircraft Materials 225 ksi against ATI 245,000 psi). Each value is kept with its own source and none is chosen as the right one.
  - No fatigue, fracture toughness, Charpy or long-term ageing data from a datasheet opened in this run. The 1968 NASA report that lists 15-7 Mo tables was not read.
  - The Ulbrich datasheet gives no condition for its thermal conductivity value, and ATI's thermal conductivity table layout was not read clearly enough to use.
  - Aluminium and iron supply shares were not gathered for this profile (USGS aluminium and iron pages were not read).
  - No space, vacuum or flight result for 15-7 PH was found; the NASA sources found are a 1969 corrosion test and a 1968 propulsion study that was not opened.
  - 'Corrosion is not quantified: the only salt-water result is the 1969 NASA qualitative test, and the NASA statement about CH 900 is internally inconsistent in the report.'
sources:
  ati-15-7:
    title: ATI 15-7 Technical Data Sheet (Semi-Austenitic Stainless Steel, UNS S15700)
    id: ATI 15-7 TDS, version 1 (2/14/2014)
    url: https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/precipitationhardening/ati_15-7_tds_en_v2.pdf
    year: 2014
    kind: datasheet
    license: supplier document, linked not reproduced
  ulbrich-15-7mo:
    title: 15-7 MO Stainless Steel, UNS S15700 (Ulbrich Stainless Steels and Special Metals)
    id: Ulbrich datasheet, revision 6.1.2015
    url: https://www.ulbrich.com/uploads/data-sheets/15-7-MO-Stainless-Steel-Wire-UNS-S15700.pdf
    year: 2015
    kind: datasheet
    license: supplier document, linked not reproduced
  aircraftmaterials-15-7:
    title: PH 15-7 Mo Stainless Steel (AMS 5520 / UNS S15700)
    id: Aircraft Materials data page
    url: https://mail.aircraftmaterials.com/data/alstst/15-7.html
    year: 2026
    kind: web
    license: supplier page, linked not reproduced
  nasa-tm-53910:
    title: Stress Corrosion Cracking Evaluation of Several Precipitation Hardening Stainless Steels (NASA Technical Memorandum, Report No. 53910)
    id: NTRS 19690028850; Humphries and Nelson, Astronautics Laboratory, 12 September 1969
    url: https://ntrs.nasa.gov/api/citations/19690028850/downloads/19690028850.pdf
    year: 1969
    kind: report
    license: public domain (NASA)
  totalmateria-1055880:
    title: EN 1.4532 Stainless steels (Total Materia)
    id: EN 1.4532, EN 10088-2 (1995)
    url: https://www.totalmateria.com/en-us/material/1055880
    year: 2026
    kind: database
    license: database page, linked not reproduced
  pubchem-nickel:
    title: PubChem compound record, Nickel (CID 935), GHS classification
    id: CID 935
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Nickel
    year: 2026
    kind: database
    license: public domain (NCBI)
  usgs-mcs2026-chromium:
    title: 'Mineral Commodity Summaries 2026: Chromium'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-nickel:
    title: 'Mineral Commodity Summaries 2026: Nickel'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-molybdenum:
    title: 'Mineral Commodity Summaries 2026: Molybdenum'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-crit2025:
    title: About the 2025 List of Critical Minerals (USGS, final list of 60 minerals)
    id: Final 2025 List of Critical Minerals, November 2025
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
    kind: web
    license: public domain (USGS)
  ec-crm:
    title: Critical raw materials (European Commission)
    id: Regulation (EU) 2024/1252 (as cited on the Commission page)
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    year: 2024
    kind: web
    license: European Commission web page
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 23
  unreachable: 0
  caveats: 2
  note: 'Written from pages read in this run: ATI and Ulbrich datasheets (PDF text), Aircraft Materials and Total Materia pages, the 1969 NASA memorandum (PDF text), PubChem nickel record, and USGS 2026 commodity summaries. Designations, properties and supply shares are as printed; shares are calculated from the printed world totals.'
story:
  recipe:
    line: PH 15-7 Mo is an iron-based alloy. Its composition in weight percent is the AMS 5520 limit set printed by ATI, Ulbrich and Aircraft Materials. It is melted and formed in the annealed Condition A, then hardened by low-temperature heat treatment; the melting route is not described in the sources opened.
    parts:
      - name: Iron
        symbol: Fe
        share: balance, printed as Balance in the ATI composition table
        role: The matrix; the other elements dissolve in it.
      - name: Chromium
        symbol: Cr
        share: 14.00 to 16.00 wt %
        role: Gives the stainless steel its corrosion resistance. Ulbrich ranks the hardened condition above the 400-series grades but below 304.
      - name: Nickel
        symbol: Ni
        share: 6.50 to 7.75 wt %
        role: Keeps the alloy austenitic in Condition A so that it can be formed easily before hardening.
      - name: Molybdenum
        symbol: Mo
        share: 2.00 to 3.00 wt %
        role: Replaces about 2 percent of the chromium found in 17-7 PH. ATI says this gives somewhat higher room and elevated temperature strength.
      - name: Aluminium
        symbol: Al
        share: 0.75 to 1.50 wt %
        role: The reactive element that drives the precipitation hardening reaction. ATI says inert-gas welding is needed to keep it from being lost.
      - name: Carbon
        symbol: C
        share: 0.09 wt % maximum
        role: Kept low; it is an impurity limit in the AMS 5520 chemistry.
  risk_groups:
    - title: For people
      level: 0
      verdict: Not classified here; nickel is the main concern
      lead: No alloy-specific safety data sheet was opened. The only hazard source is the PubChem summary for nickel metal, which the alloy contains.
      points:
        - label: Nickel
          line: PubChem's summary for nickel metal lists H317 (allergic skin reaction), H351 (suspected of causing cancer), H372 (organ damage from repeated exposure) and H412 (long-lasting harm to aquatic life).
        - label: Dust and fume
          line: Grinding and welding can make fume. The alloy-specific hazard data for this fume were not verified in this run.
    - title: Handling and storage
      points:
        - label: Welding
          line: ATI says the alloy welds with inert-gas methods, protecting the aluminium, and needs no preheat or post-weld anneal.
        - label: Conditioning
          line: RH 950 needs a sub-zero step at -100 F for 8 hours after the austenite conditioning, according to Aircraft Materials and ATI.
  why: PH 15-7 Mo is a precipitation-hardening stainless steel. It is easy to form while soft, because it is mostly austenitic in Condition A (annealed). It is then hardened by a low-temperature heat treatment that turns part of the austenite into martensite and ages it. ATI notes that this route gives minimum distortion compared with quench-and-temper hardening. The result is a steel with a yield strength of 1515 MPa in RH 950, and that strength comes with a good balance of corrosion resistance for a hardenable grade.
  uses:
    - where: Springs and retaining rings
      line: ATI and Ulbrich both list springs, seal rings and retaining rings as uses. ATI says the alloy has been used in aerospace and many spring-type applications that need high strength.
    - where: Aircraft components
      line: Ulbrich lists aircraft components as an application. ATI describes the alloy as used in aerospace work.
    - where: Hot-strength applications
      line: 'ATI says the alloy keeps useful strength at elevated temperature: RH 950 gives a yield strength of 1225 MPa at 316 C (600 F) in the short-time test it prints.'
  can_do:
    - label: Strength
      benchmark: ultimate_tensile_strength
      value: 1690 MPa
      line: In RH 950 the ATI typical ultimate tensile strength is 1690 MPa (245,000 psi), against 860 MPa in Condition A. Ulbrich prints a Condition C minimum of 1380 MPa.
    - label: Hardness
      benchmark: hardness
      value: 48 HRC
      line: ATI prints 48 HRC for RH 950 and 43 HRC for TH 1050, against 88 HRB in Condition A.
    - label: Density
      benchmark: density
      value: 7.67 g/cm3
      line: The ATI datasheet prints 7.67 g/cm3 for RH 950 and TH 1050, and 7.80 g/cm3 for Condition A.
    - label: Stiffness
      benchmark: elastic_modulus
      value: 28 x 10^6 psi
      line: The ATI datasheet prints a modulus of 28 x 10^6 psi (195 in its metric column), and Ulbrich prints 200 GPa. The two datasheets differ by about 2 percent.
  compare: PH 15-7 Mo is the molybdenum-bearing version of 17-7 PH, and ATI says it is somewhat stronger at room and elevated temperature than 17-7 PH. Its corrosion resistance is better than the 400-series hardenable grades, but the 1969 NASA test found it prone to stress corrosion cracking in every condition except CH 900. Its hardness and strength in RH 950 are higher than in TH 1050.
  compare_rows:
    - label: Ultimate tensile strength in RH 950
      benchmark: ultimate_tensile_strength
    - label: Yield strength in RH 950
      benchmark: yield_strength
    - label: Density
      benchmark: density
  handling:
    - The composition and condition must match the purchase specification; ATI prints typical values and says they are not for design.
    - Weld with inert gas to protect the aluminium, and expect a higher ferrite content in the weld than with 17-7 PH.
    - 'Avoid salt environments under stress: the 1969 NASA test cracked the alloy in every condition except CH 900.'
    - Keep the sub-zero step in RH 950 and the aging temperature to the stated limits, because higher or longer ageing lowers strength.
  good_for:
    - High strength at a low distortion heat treatment. ATI notes that low-temperature hardening keeps distortion small.
    - Springs, rings and aircraft parts that need strength above that of 304 and that will not be exposed to salt water under stress.
  watch_out:
    - Stress corrosion cracking. The 1969 NASA test found cracking in every condition except CH 900.
    - Low ductility in CH 900 (1 percent minimum elongation in Ulbrich's Condition C).
    - Corrosion resistance is below Type 304 in most media, according to ATI.
  verdict: PH 15-7 Mo gives high strength for springs and rings. Salt-water stress corrosion is the main reason to specify with care, and the strength data differ by supplier, so the mill certificate should govern.