17-4 PH stainless steel 17-4 PH (UNS S17400, Type 630)

Fe balance, 15.0 to 17.5 Cr, 3.0 to 5.0 Ni, 3.0 to 5.0 Cu, 0.15 to 0.45 Nb plus Ta, max 0.070 C, max 1.00 Mn, max 1.00 Si, max 0.040 P, max 0.030 S (wt%)

Also known as UNS S17400, EN 1.4542, EN name X5CrNiCuNb16-4, AISI 630, JIS SUS630, AFNOR Z6CNU1704 · 16 more

17-4 PH is a martensitic, precipitation-hardening stainless steel with about 15 to 17.5 percent chromium, 3 to 5 percent nickel and 3 to 5 percent copper (Carpenter).

16 sources · Updated 2026-10-24 · CC BY 4.0

Evidence level

2 of 5

Lab-measured

Strength

1262 MPa

Stiffness

196 GPa

Hardness

36 HRC

Heat

316 °C

Recipe, share of the weight

  • Fe balance (the rest)Iron
  • Cr 15 to 17.5%Chromium
  • Ni 3 to 5%Nickel
  • Cu 3 to 5%Copper
  • Nb+Ta 0.15 to 0.45%Niobium plus tantalum
  • C 0 to 0.07%Carbon
  • Mn 0 to 1%Manganese
  • Si 0 to 1%Silicon
  • P 0 to 0.04%Phosphorus
  • S 0 to 0.03%Sulfur

Best for

High-strength fittings, fasteners, shafts and valve parts that need more strength than 304 and moderate corrosion resistance

Weakest at

Stress corrosion cracking and pitting in peak-aged (H900) material, and crevice corrosion in stagnant salt water

Risk at a glance

  • People None found. No safety data sheet for the alloy was read
  • If it fails High. Stress corrosion cracking at peak strength
  • Corrosion Severe. Carpenter rates sea water as Restricted on its four-level comparative scale.

Quick facts: 17-4 PH (UNS S17400, Type 630)

Key properties of 17-4 PH (UNS S17400, Type 630)
PropertyValueBasis
Density7.75 to 7.86 g/cm³3 sourced values across conditions
Yield strength725 to 1,262 MPa9 sourced values across conditions
Tensile strength930 to 1,365 MPa9 sourced values across conditions
Young's modulus196 to 201 GPa2 sourced values across conditions
Thermal conductivity17.9 to 22.6 W/(m·K)2 sourced values across conditions
Thermal expansion (CTE)11.2 to 13 ppm/K4 sourced values across conditions
Melting point1,404 to 1,440 °C1 sourced value
Specific heat419 to 460 J/(kg·K)2 sourced values across conditions
Electrical resistivity7.7e-7 to 9.8e-7 Ω·m2 sourced values across conditions
Maximum service temperature316 °C1 sourced value

What is the density of 17-4 PH stainless steel?

17-4 PH stainless steel has a density of 7.75 to 7.86 g/cm³. The range covers 3 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.

What is the thermal conductivity of 17-4 PH stainless steel?

17-4 PH stainless steel has a thermal conductivity of 17.9 to 22.6 W/(m·K). The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.

What is the coefficient of thermal expansion of 17-4 PH stainless steel?

17-4 PH stainless steel has a coefficient of thermal expansion of 11.2 to 13 ppm/K. The range covers 4 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.

What is the melting point of 17-4 PH stainless steel?

17-4 PH stainless steel has a melting point of 1,404 to 1,440 °C. The source and test conditions are listed in the properties table on this page.

What is the yield strength of 17-4 PH stainless steel?

17-4 PH stainless steel has a yield strength of 725 to 1,262 MPa. The range covers 9 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.

What are the other names and codes for 17-4 PH stainless steel?

17-4 PH stainless steel is also written as UNS S17400, EN 1.4542, EN name X5CrNiCuNb16-4, AISI 630, JIS SUS630, AFNOR Z6CNU1704. Each code is printed in the source listed beside it in the designations table.

What is 17-4 PH stainless steel used for?

Uses recorded in the sources include Aircraft and missile fittings; Bolts and fasteners; Jet engine stator vanes.

Why it exists

17-4 PH gives high strength from a simple one-step aging treatment, with corrosion resistance close to Type 304 in most media (Jacquet). Its weak point is that the highest strength comes with the greatest risk of stress corrosion cracking, so the aging condition is chosen for the environment as well as the load.

Where it's used

Aircraft and missile fittings

Carpenter lists aircraft and missile fittings for its 17-4 SELECT variant, and Steelforge lists forged aircraft fittings.

Bolts and fasteners

Austral Wright lists high-strength bolting and fasteners in aerospace and chemical plant use, and Jacquet lists AMS 7474 bolts.

Jet engine and pump parts

Ulbrich lists jet engine stator vanes, voestalpine lists pump shafts and rotors, and Steelforge lists valve parts and pump shafts.

Chemical, food and medical equipment

Ulbrich lists chemical, petrochemical and food processing equipment and surgical instruments, and Wikipedia lists medical devices and firearms.

Recipe

Fe balance, 15.0 to 17.5 Cr, 3.0 to 5.0 Ni, 3.0 to 5.0 Cu, 0.15 to 0.45 Nb plus Ta, max 0.070 C, max 1.00 Mn, max 1.00 Si, max 0.040 P, max 0.030 S (wt%)

17-4 PH is an iron-based martensitic precipitation-hardening stainless steel, UNS S17400 (AISI 630), made to the composition limits in the identity record with iron as the balance. It is supplied in the annealed condition, after a high-temperature solution treatment. One aging step at 480 to 620 C (900 to 1150 F) precipitates a copper-based phase that gives the strength (Austral Wright; Jacquet). Product forms are bar, sheet, plate, wire and forgings.

What 17-4 PH (UNS S17400, Type 630) is made of
IngredientShare of the weightWhat it does
Iron Fe balance (the rest) Matrix of the alloy, martensitic when annealed.
Chromium Cr 15 to 17.5% Gives the passive film that resists rust; corrosion close to Type 304 in most media (Jacquet).
Nickel Ni 3 to 5% Part of the chromium-nickel-copper martensitic alloy (Carpenter: about 17 percent Cr and 4 percent Ni).
Copper Cu 3 to 5% Forms a copper-based phase on aging, which gives the high strength (Austral Wright).
Niobium plus tantalum Nb+Ta 0.15 to 0.45% Columbium plus tantalum, a listed alloying addition (Jacquet; Carpenter).
Carbon C 0 to 0.07% Kept low; Carpenter gives a maximum of 0.070 percent.
Manganese Mn 0 to 1% Residual element, maximum 1.00 percent.
Silicon Si 0 to 1% Residual element, maximum 1.00 percent.
Phosphorus P 0 to 0.04% Impurity held low, maximum 0.040 percent.
Sulfur S 0 to 0.03% Impurity held low, maximum 0.030 percent.

Weight shares are as printed in the sources.

What it can do

Strength

1262 MPa

measured

Minimum yield is 1170 MPa in H900 and 725 MPa in H1150 for ASTM A564 bar (Austral Wright). Typical yield for cold-finished bar is 1262 MPa in H900 (Carpenter).

Stiffness

196 GPa

measured

Elastic modulus is 196 GPa in all conditions (Jacquet), and Austral Wright prints 200 to 201 GPa in tension.

Hardness

36 HRC

measured

Typical hardness is 44 HRC in H900 and 33 HRC in H1150 for cold-finished bar (Carpenter). Minimum hardness is 40 HRC in H900 (Austral Wright).

Heat

316 °C

measured

High strength is kept to about 316 C (600 F) (Jacquet).

How it compares

Jacquet says the corrosion resistance of 17-4 PH is comparable to Type 304 in most media and superior to the hardenable 400 series. Carpenter says its 17-4 SELECT variant approaches Type 304 in most corrodents and is better than the 400 series, while Carpenter's card calls the corrosion resistance moderate. Jacquet also says H900 gives the highest strength of this family, slightly below other precipitation-hardening grades that need more heat-treatment steps.

The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details. Other materials are shown beside it; each was measured under its own conditions, so open its page before comparing closely. Compare every grade in the family.

Benchmarks
Measurement17-4 PH (UNS S17400, Type 630)17-7 PH (UNS S17700, EN 1.4568, Type 631)15-7 PH
Capacity and energy
charpy impact energy20 J54no datano data
charpy impact energy41 J55no datano data
Thermal behavior and safety
melting point1404 °C81404 to 1440 °Cno data
Thermal conductivity17.9 W/m.K916.9 W/(m·K)16.2 W/m-K
Thermal conductivity22.6 W/m.K1016.9 W/(m·K)16.2 W/m-K
specific heat419 J/kg.K11no datano data
specific heat460 J/kg.K12no datano data
Physical and electrical
Density7.75 g/cm³17.81 g/cm³7.8 g/cm³
Density7.81 g/cm³27.81 g/cm³7.8 g/cm³
Density7.86 g/cm³37.81 g/cm³7.8 g/cm³
electrical resistivity98 microhm-cm1780 µΩ·cm82 microhm-cm
electrical resistivity77 microhm-cm1880 µΩ·cm82 microhm-cm
hardness rockwell c36 HRC29no datano data
hardness rockwell c44 HRC30no datano data
hardness rockwell c38 HRC31no datano data
hardness rockwell c33 HRC32no datano data
hardness rockwell c40 HRC51no datano data
hardness rockwell c35 HRC52no datano data
hardness rockwell c28 HRC53no datano data
Other measurements
elastic modulus196 GPa4200 GPa28 10^6 psi
elastic modulus200 GPa5200 GPa28 10^6 psi
shear modulus77.2 GPa6no datano data
poissons ratio0.272 -7no datano data
Thermal expansion (CTE)11.3 10-6/°C1317.3 µm/(m·°C)14.4 10^-6/C
Thermal expansion (CTE)11.7 10-6/°C1417.3 µm/(m·°C)14.4 10^-6/C
Thermal expansion (CTE)13 10-6/°C1517.3 µm/(m·°C)14.4 10^-6/C
Thermal expansion (CTE)11.2 10-6/°C1617.3 µm/(m·°C)14.4 10^-6/C
Maximum service temperature316 °C19no datano data
yield strength1262 MPa20310 MPa380 MPa
yield strength1117 MPa21310 MPa380 MPa
yield strength869 MPa22310 MPa380 MPa
ultimate tensile strength1365 MPa23827 MPa860 MPa
ultimate tensile strength1158 MPa24827 MPa860 MPa
ultimate tensile strength993 MPa25827 MPa860 MPa
elongation15 %2635 %30 %
elongation16 %2735 %30 %
elongation20 %2835 %30 %
yield strength760 MPa33310 MPa380 MPa
yield strength1240 MPa34310 MPa380 MPa
yield strength860 MPa35310 MPa380 MPa
ultimate tensile strength1030 MPa36827 MPa860 MPa
ultimate tensile strength1340 MPa37827 MPa860 MPa
ultimate tensile strength1000 MPa38827 MPa860 MPa
elongation8 %3935 %30 %
elongation10 %4035 %30 %
elongation10 %4135 %30 %
yield strength1170 MPa42310 MPa380 MPa
yield strength1000 MPa43310 MPa380 MPa
yield strength725 MPa44310 MPa380 MPa
ultimate tensile strength1310 MPa45827 MPa860 MPa
ultimate tensile strength1070 MPa46827 MPa860 MPa
ultimate tensile strength930 MPa47827 MPa860 MPa
elongation10 %4835 %30 %
elongation12 %4935 %30 %
elongation16 %5035 %30 %
elongation5 %5635 %30 %
elongation5 %5735 %30 %
elongation8 %5835 %30 %

Why choose it, and why not

Good for

  • Fittings, fasteners and shafts where strength matters and exposure is mild, such as rural and mild industrial air (Austral Wright).
  • Parts that can be aged to H1150 or double-aged for NACE sour service (voestalpine).

Watch out for

  • Peak-aged H900 material is most prone to stress corrosion cracking. Age higher when chloride or sour service is possible (Jacquet; Carpenter).
  • Crevice corrosion in stagnant salt water, and Restricted for sea water in Carpenter's table (Wikipedia; Carpenter).
  • Annealed material is brittle and should not be used. Plasma torch cutting can crack it (Jacquet).

17-4 PH is the strong, moderately corrosion-resistant choice when a one-step age can set the strength. The aging condition is the design decision: H900 gives the most strength and the most stress corrosion risk, and H1150 gives more toughness and margin. For sea water or sour service, choose an overaged or NACE-listed condition and check the data for that condition.

Technical details

For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.

Other names and standards

The same grade under other systems, as datasheets and standards print them. Each code was checked against the page it comes from.

Other names and standards
SystemCodes
UNSS17400
EN1.4542
EN nameX5CrNiCuNb16-4
AISI630
JISSUS630
AFNORZ6CNU1704
ASTMA564 (bars, wire and shapes), A693 (sheet, plate and strip), A705 (forgings), F899 (when fully aged)
ASMESA-564, SA-693 (plate, sheet and strip), SA-705 (forgings)
AMS5604 (sheet, strip and plate), 5643 (bars, forgings, tubing and rings), 5622, 5642 (bar), 5523, 7474 (bolts)
MILMIL-S-25043
Trade nameCustom 630, 17-4 PH

Notes

The method, full conditions and any caveat for the numbered rows above.

Notes for the numbered rows
#MeasurementMethodConditionsCaveat
1DensityPhysical properties table, Density in g/cm3 row, Condition A columncondition Condition A (annealed)basis typical, room temperatureform sheet, strip, plate and long products—
2DensityPhysical properties table, Density in g/cm3 row, H 900 columncondition H900basis typical, room temperatureform sheet, strip, plate and long products—
3DensityPhysical properties table, Density in g/cm3 row, H 1150 columncondition H1150basis typical, room temperatureform sheet, strip, plate and long products—
4elastic modulusMechanical properties table, Modulus of Elasticity row, GPa value in parenthesescondition all conditions printed (Condition A, H900, H1075, H1150)basis modulus of elasticity, printed as 28.5 x 10^6 psi (196 GPa)—
5elastic modulusPhysical properties table, Modulus of Elasticity tension row, minimum and maximum as printedcondition tension, printed as a range across conditionsbasis modulus of elasticity, tension—
6shear modulusMechanical properties table, Modulus of Rigidity row, GPa value in parenthesescondition all conditions printed (Condition A, H900, H1075, H1150)basis modulus of rigidity, printed as 11.2 x 10^6 psi (77.2 GPa)—
7poissons ratioPhysical properties table, Poisson's ratio rows, value as printedcondition H900, H1075 and H1150 (same value printed for each)basis room temperature—
8melting pointPhysical properties table, Melting Range row, Celsius range as printedbasis melting range as printed, no solidus or liquidus splitunit in source 2560-2625 F (1404-1440 C)—
9Thermal conductivityPhysical properties table, Thermal Conductivity row, W/m.K value as printedcondition H900temperature 149 C (300 F)unit in source 124.0 Btu-in/hr/ft2/F at 300 F—
10Thermal conductivityPhysical properties table, Thermal Conductivity row, W/m.K value as printedcondition H900temperature 482 C (900 F)unit in source 157.0 Btu-in/hr/ft2/F at 900 F—
11specific heatPhysical properties table, Mean Specific Heat row, J/kg.K value as printedcondition not split by condition in the tabletemperature 0 to 100 C (32 to 212 F)unit in source 0.1000 Btu/lb/F—
12specific heatSpecific Heat (Annealed Condition) table, J/kg.K value as printedcondition Condition A (annealed)temperature 0 to 100 C (32 to 212 F)unit in source 0.11 Btu/lb/F—
13Thermal expansion (CTE)Physical properties table, mean linear CTE at +70 to 800 F row, metric value in parentheses, Condition A columncondition Condition Atemperature 21 to 427 C (70 to 800 F)—
14Thermal expansion (CTE)Physical properties table, mean linear CTE at +70 to 800 F row, metric value in parentheses, H 900 columncondition H900temperature 21 to 427 C (70 to 800 F)—
15Thermal expansion (CTE)Physical properties table, mean linear CTE at +70 to 800 F row, metric value in parentheses, H 1150 columncondition H1150temperature 21 to 427 C (70 to 800 F)—
16Thermal expansion (CTE)Mean Coefficient of Thermal Expansion table (annealed condition), value printed in μm/m·°C, which equals 10-6/°Ccondition Condition A (annealed)temperature 21 to 427 C (70 to 800 F)unit in source μm/m·°C—
17electrical resistivityPhysical properties table, Electrical Resistivity row, value as printedcondition Condition A (annealed)temperature room temperature—
18electrical resistivityPhysical properties table, Electrical Resistivity row, value as printedcondition H900temperature room temperature—
19Maximum service temperatureIntroduction text, Celsius value in parentheses as printedbasis statement that high strength is maintained to approximately 600 F (316 C)—
20yield strengthTypical mechanical properties table, 0.2 percent yield strength in MPa columncondition H900basis typical, room temperature, 0.2 percent offsetform bar, cold finished—
21yield strengthTypical mechanical properties table, 0.2 percent yield strength in MPa columncondition H1025basis typical, room temperature, 0.2 percent offsetform bar, cold finished—
22yield strengthTypical mechanical properties table, 0.2 percent yield strength in MPa columncondition H1150basis typical, room temperature, 0.2 percent offsetform bar, cold finished—
23ultimate tensile strengthTypical mechanical properties table, ultimate tensile strength in MPa columncondition H900basis typical, room temperatureform bar, cold finished—
24ultimate tensile strengthTypical mechanical properties table, ultimate tensile strength in MPa columncondition H1025basis typical, room temperatureform bar, cold finished—
25ultimate tensile strengthTypical mechanical properties table, ultimate tensile strength in MPa columncondition H1150basis typical, room temperatureform bar, cold finished—
26elongationTypical mechanical properties table, elongation columncondition H900basis typical, elongation in 2 in (50.8 mm)form bar, cold finished—
27elongationTypical mechanical properties table, elongation columncondition H1025basis typical, elongation in 2 in (50.8 mm)form bar, cold finished—
28elongationTypical mechanical properties table, elongation columncondition H1150basis typical, elongation in 2 in (50.8 mm)form bar, cold finished—
29hardness rockwell cTypical mechanical properties table, Rockwell C hardness columncondition Condition A (annealed and cold finished)basis typical, room temperature, Brinell 352 as printedform bar, cold finished—
30hardness rockwell cTypical mechanical properties table, Rockwell C hardness columncondition H900basis typical, room temperature, Brinell 420 as printedform bar, cold finished—
31hardness rockwell cTypical mechanical properties table, Rockwell C hardness columncondition H1025basis typical, room temperature, Brinell 352 as printedform bar, cold finished—
32hardness rockwell cTypical mechanical properties table, Rockwell C hardness columncondition H1150basis typical, room temperature, Brinell 311 as printedform bar, cold finished—
33yield strengthMechanical properties table, 0.2 percent offset yield strength in MPa rowcondition Condition Abasis typical, room temperature, 0.2 percent offsetform sheet, strip, plate and long products—
34yield strengthMechanical properties table, 0.2 percent offset yield strength in MPa rowcondition H900basis typical, room temperature, 0.2 percent offsetform sheet, strip, plate and long products—
35yield strengthMechanical properties table, 0.2 percent offset yield strength in MPa rowcondition H1150basis typical, room temperature, 0.2 percent offsetform sheet, strip, plate and long products—
36ultimate tensile strengthMechanical properties table, Ultimate Tensile Strength in MPa rowcondition Condition Abasis typical, room temperatureform sheet, strip, plate and long products—
37ultimate tensile strengthMechanical properties table, Ultimate Tensile Strength in MPa rowcondition H900basis typical, room temperatureform sheet, strip, plate and long products—
38ultimate tensile strengthMechanical properties table, Ultimate Tensile Strength in MPa rowcondition H1150basis typical, room temperatureform sheet, strip, plate and long products—
39elongationMechanical properties table, Elongation row, percentage in 2 incondition Condition Abasis typical, elongation in 2 inform sheet, strip, plate and long products—
40elongationMechanical properties table, Elongation row, percentage in 2 incondition H900basis typical, elongation in 2 inform sheet, strip, plate and long products—
41elongationMechanical properties table, Elongation row, percentage in 2 incondition H1150basis typical, elongation in 2 inform sheet, strip, plate and long products—
42yield strengthMinimum properties table, 0.2 percent proof stress MPa (min) columncondition H900basis minimum, ASTM A564 bar tableheat treatment 480 C, 1 h, air coolform bar and shapes—
43yield strengthMinimum properties table, 0.2 percent proof stress MPa (min) columncondition H1025basis minimum, ASTM A564 bar tableheat treatment 550 C, 4 h, air coolform bar and shapes—
44yield strengthMinimum properties table, 0.2 percent proof stress MPa (min) columncondition H1150basis minimum, ASTM A564 bar tableheat treatment 620 C, 4 h, air coolform bar and shapes—
45ultimate tensile strengthMinimum properties table, tensile strength MPa (min) columncondition H900basis minimum, ASTM A564 bar tableheat treatment 480 C, 1 h, air coolform bar and shapes—
46ultimate tensile strengthMinimum properties table, tensile strength MPa (min) columncondition H1025basis minimum, ASTM A564 bar tableheat treatment 550 C, 4 h, air coolform bar and shapes—
47ultimate tensile strengthMinimum properties table, tensile strength MPa (min) columncondition H1150basis minimum, ASTM A564 bar tableheat treatment 620 C, 4 h, air coolform bar and shapes—
48elongationMinimum properties table, elongation percent (min) columncondition H900basis minimum, ASTM A564 bar tableform bar and shapes—
49elongationMinimum properties table, elongation percent (min) columncondition H1025basis minimum, ASTM A564 bar tableform bar and shapes—
50elongationMinimum properties table, elongation percent (min) columncondition H1150basis minimum, ASTM A564 bar tableform bar and shapes—
51hardness rockwell cMinimum properties table, Hardness Rockwell C (min) columncondition H900basis minimum, ASTM A564 bar tableform bar and shapes—
52hardness rockwell cMinimum properties table, Hardness Rockwell C (min) columncondition H1025basis minimum, ASTM A564 bar tableform bar and shapes—
53hardness rockwell cMinimum properties table, Hardness Rockwell C (min) columncondition H1150basis minimum, ASTM A564 bar tableform bar and shapes—
54charpy impact energyMinimum properties table, Impact Charpy VJ (min) columncondition H1025basis minimum, ASTM A564 bar table, Charpy V-notchform bar and shapes—
55charpy impact energyMinimum properties table, Impact Charpy VJ (min) columncondition H1150basis minimum, ASTM A564 bar table, Charpy V-notchform bar and shapes—
56elongationHeat treat capabilities (aged) table, elongation mincondition H900basis minimum, wire datasheetform wire—
57elongationHeat treat capabilities (aged) table, elongation mincondition H1025basis minimum, wire datasheetform wire—
58elongationHeat treat capabilities (aged) table, elongation mincondition H1150basis minimum, wire datasheetform wire—

Corrosion and compatibility

What happens when it meets other materials and environments.

Corrosion and compatibility
EnvironmentConcernWhat happens
Sea water severe Carpenter rates sea water as Restricted on its four-level comparative scale.1
Salt spray (NaCl) low Carpenter rates salt spray as Good.2
Humidity low Carpenter rates humidity as Excellent.3
Nitric acid low Carpenter rates nitric acid as Good.4
Sulfuric acid severe Carpenter rates sulfuric acid as Restricted.5
Sour oil and gas severe Carpenter rates sour oil and gas as Restricted.6
Sea coast atmosphere and salt water service not rated Sea coast air causes slow light rusting and pitting; salt water use relies on cathodic protection.7
Crevice corrosion in stagnant salt water not rated Crevice corrosion can occur in stagnant salt water.8
General corrosion in most media low Corrosion resistance is comparable to Type 304 in most media and superior to the 400 series.9
Peak-aged material in chloride service not rated Peak-aged material is more susceptible to stress corrosion cracking.10
Hardening temperature and stress corrosion cracking not rated Good stress corrosion resistance comes from hardening at 1025 F (552 C) or higher.11
Overaged condition and stress corrosion cracking not rated Overaging improves resistance to stress corrosion cracking.12
Annealed (untempered martensite) material not rated Annealed material is more sensitive to hydrogen embrittlement and chloride cracking than aged material.13
Sour (NACE) service not rated H1150M and DH1150 are stocked for NACE service.14
Corrosion details
#EnvironmentDetailsTest conditions
1 Sea water On Carpenter's comparative scale (Excellent, Good, Moderate, Restricted) sea water is Restricted for 17-4 SELECT, which carries the same UNS S17400 type. The scale is for comparison only and says corrosion testing is recommended. The site rating is mapped as Restricted to severe. medium sea waterscale Carpenter comparative rating
2 Salt spray (NaCl) On Carpenter's comparative scale the salt spray entry for 17-4 SELECT is Good, mapped here to low. medium salt spray (NaCl)scale Carpenter comparative rating
3 Humidity On Carpenter's comparative scale the humidity entry for 17-4 SELECT is Excellent, mapped here to low. medium humid airscale Carpenter comparative rating
4 Nitric acid Carpenter's comparative table gives 17-4 SELECT a Good rating in nitric acid, mapped here to low. The table says factors such as temperature, concentration and pH change the result. medium nitric acidscale Carpenter comparative rating
5 Sulfuric acid Carpenter's comparative table gives 17-4 SELECT a Restricted rating in sulfuric acid, mapped here to severe. medium sulfuric acidscale Carpenter comparative rating
6 Sour oil and gas Carpenter's comparative table rates sour oil and gas as Restricted for 17-4 SELECT, mapped here to severe. Use the NACE-listed aged conditions for sour service (see the mitigations). medium sour oil and gasscale Carpenter comparative rating
7 Sea coast atmosphere and salt water service Austral Wright says 17-4PH develops overall light rusting and pitting slowly in sea coast atmospheres, and that it is used successfully in salt water as boat shafting with cathodic protection. medium sea coast atmosphere; salt water with cathodic protection
8 Crevice corrosion in stagnant salt water Wikipedia says 17-4 is susceptible to crevice corrosion in stagnant salt water, and that its corrosion resistance and machinability are comparable to 304. medium stagnant salt water in crevices
9 General corrosion in most media Jacquet states that corrosion resistance is comparable to Type 304 stainless steel in most media and superior to the hardenable 400 series stainless steels. Carpenter's card describes the corrosion resistance as moderate. medium most media
10 Peak-aged material in chloride service Jacquet says 17-4 is more susceptible to stress corrosion cracking at peak strength. Where chloride stress corrosion cracking is possible, the alloy should be precipitation hardened to the lowest hardness compatible with the use, by heat treating at the highest temperature that still gives the minimum properties. condition H900 and other peak-aged conditionsmedium chloride
11 Hardening temperature and stress corrosion cracking Carpenter says good resistance to stress corrosion cracking is gained by hardening at 1025 F (552 C) and higher, and that 17-4 SELECT withstood corrosive attack better than the 400 series hardenable stainless steels. temperature 1025 F (552 C) and higher for aging
12 Overaged condition and stress corrosion cracking Wikipedia says overaging, meaning aging beyond the peak strength condition, improves resistance to stress corrosion cracking. condition overaged (beyond peak strength)
13 Annealed (untempered martensite) material Jacquet says annealed 17-4 has untempered martensite, which may fail by unpredictable brittle fracture and is more sensitive to hydrogen embrittlement and chloride stress corrosion cracking than aged material. condition Condition A (annealed)
14 Sour (NACE) service voestalpine says it stocks several conditions of 17-4, including H1150M and DH1150, for NACE service. The page gives no crack threshold data. condition H1150M and DH1150 (double-aged)

Risks and side effects

Hazards to people, what happens when a cell overheats, and how the material is handled and stored.

For people

The PubChem records below cover elemental nickel, chromium and copper, not the finished 17-4 PH alloy.

Nickel
PubChem lists elemental nickel as Danger, with H317 (skin sensitiser), H351 (suspected carcinogen) and H372 (organ damage on repeated exposure).
Chromium
PubChem lists elemental chromium as Danger with H317, H319 and H334 in notifications that carry hazard codes.
Copper
PubChem lists elemental copper as Warning, with H400 and H410 for aquatic life.
Workshop
Check the supplier safety data sheet before cutting, grinding or welding this alloy.

In the environment

Crevice corrosion and stress corrosion cracking are the main failure routes in service.

Sea water
Carpenter rates sea water as Restricted for 17-4 SELECT. Austral Wright uses it in salt water as boat shafting only with cathodic protection.
Crevices
Wikipedia says it is susceptible to crevice corrosion in stagnant salt water.
Sour service
Carpenter rates sour oil and gas as Restricted. voestalpine stocks H1150M and DH1150 for NACE service.

Heat treatment and fabrication

The highest strength comes from the H900 condition, which is also the most prone to stress corrosion cracking.

Peak aging
Jacquet says 17-4 is more susceptible to stress corrosion cracking at peak strength, so the lowest hardness compatible with the use is preferred.
Annealed
Untempered martensite in the annealed condition may fail unpredictably and is more sensitive to hydrogen embrittlement (Jacquet).
Torch cutting
Plasma torch cutting of annealed plate can crack the metal, especially plate thicker than about 1 inch (Jacquet).

Test details
The original wording and numbers from the sources, for readers who want them.

Failure risks

Failure risks
FailureTrigger and consequence
Stress corrosion cracking at peak strengthhigh severityChloride or other corrosive exposure with H900 or other peak-aged material under tensile stressBrittle cracking in service; Jacquet says to age to the lowest hardness compatible with the use
Brittle fracture of material left in the annealed conditionhigh severityService or fabrication in Condition A (annealed) without an aging treatmentUntempered martensite may fail unpredictably and is more sensitive to hydrogen embrittlement and chloride cracking
Crevice and pitting corrosion in salt watermoderate severityStagnant salt water, crevices, or sea coast atmosphereCrevice corrosion in stagnant salt water; slow light rusting and pitting in sea coast air
Cracking during plasma torch cuttingmoderate severityPlasma torch cutting of material in the as-annealed condition, especially plate thicker than about 1 inch (25.4 mm)Cracks that may propagate far into the base metal
Loss of strength from overagingmoderate severityAging above the specified temperature or for too longThe precipitation reaction passes peak strength, so strength and hardness fall

Handling and storage

  • Do not put annealed (Condition A) material into service; age it to a specified H condition first.
  • Choose the aging temperature for stress corrosion as well as strength. Hardening at 1025 F (552 C) or higher gives good stress corrosion resistance.
  • Severe cold working should be done in the H1150 condition, and the part should be re-aged after cold forming.
  • Multipass welds must be solution annealed before aging; single-pass welds are precipitation hardened after welding.
  • Oxyacetylene welding is not recommended because carbon pick-up can occur in the weld; use a 17-4PH type filler.
  • Before plasma torch cutting, age the material at 1150 F (621 C) or higher to lower the cracking risk, then re-solution anneal and re-age after machining.
  • Avoid protective atmospheres containing carbon or nitrogen during heat treatment; they can soften the surface.

Mitigations

  • For NACE sour service, use the H1150M or double-aged DH1150 conditions, which voestalpine stocks for that service.
  • Clean and passivate after fabrication, and remove scale, lubricants and drawing coatings, which Carpenter says matter for corrosion resistance.
  • Overaging, meaning aging beyond the peak strength condition, improves resistance to stress corrosion cracking.

Supply and geography

How common the raw materials are and where they come from.

Nickel production by country (world mine, 2025 estimate)

World mine production 3,900,000 t in 2025 (estimated); world reserves more than 140,000,000 t, of which Indonesia 62,000,000 t (USGS 2026).

Top producers (2025)
Indonesia 66.7%, Philippines 6.9%, Russia 5.1%, New Caledonia 3.6%, Canada 3.6%, China 3.1%
Recycling
Nickel recovered from scrap accounted for about 60% of US apparent consumption in 2025; most secondary nickel is stainless-steel scrap.
Substitutes
Low-nickel, duplex or ultrahigh-chromium stainless steels replace austenitic grades in construction; Titanium alloys can substitute for nickel or nickel-base alloys in corrosive environments

Nickel use in the United States

Stainless and alloy steel and nickel-containing alloys typically account for more than 85% of domestic consumption. US net import reliance 41% of apparent consumption in 2025 (estimated).

Recycling
Recycled nickel 60% of US apparent consumption in 2025.

Chromium production by country (world mine, 2025 estimate)

World mine production 51,000 thousand t gross weight in 2025 (estimated); world resources greater than 12 billion t of shipping-grade chromite, with 95% of chromium resources in Kazakhstan and southern Africa.

Top producers (2025)
South Africa 45.1%, Turkey 17.6%, Kazakhstan 13.7%, India 5.9%, Brazil 3.9%, Zimbabwe 3.9%
Recycling
Recycled chromium in stainless-steel scrap receipts was 21% of US apparent consumption in 2025.
Substitutes
Chromium has no substitute in stainless steel, the leading end use

Chromium import reliance

US net import reliance 79% of apparent consumption in 2025 (estimated).

Copper production by country (world mine, 2025 estimate)

World mine production 23,000 thousand t in 2025 (estimated); world reserves 980,000 thousand t (USGS 2026).

Top producers (2025)
Chile 23%, Congo (Kinshasa) 13.9%, Peru 11.7%, China 7.8%, Russia 5.7%
Critical mineral lists
U.S. Final 2025 List of Critical Minerals (Federal Register, 7 November 2025): listed
Recycling
Old scrap converted to refined metal provided about 160,000 t of copper in 2025, and copper from scrap contributed about 30% of US supply.
Substitutes
Aluminum substitutes for copper in electrical equipment and power cable; titanium and steel are used in heat exchangers

Copper use and import reliance in the United States

US net import reliance 57% of apparent consumption in 2025 (estimated). Building construction takes 42% of copper and copper alloy products, electrical and electronic products 23%.