Stainless Steel 15-5PH (UNS S15500)

15-5PH stainless steel is a chromium-nickel-copper precipitation-hardening stainless steel with a martensitic structure. It is widely used where high strength, hardness, dimensional stability, and better toughness than 17-4PH are required. The alloy is commonly identified as UNS S15500, XM-12, 15Cr-5Ni, and in European references as 1.4545 / X5CrNiCu15-5. Carpenter describes 15Cr-5Ni as a martensitic precipitation-hardening stainless steel with high strength, hardness, and excellent corrosion resistance, chemically balanced to reduce delta ferrite and improve transverse toughness and ductility.

Compared with 17-4PH, 15-5PH is often selected for parts requiring better transverse toughness, better ductility in larger sections, and reliable mechanical performance after single-step low-temperature aging. Service Steel Aerospace notes that 15-5PH offers high strength, high hardness, excellent corrosion resistance, better transverse toughness and ductility than 17-4PH, and is readily weldable.

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15-5PH At a Glance

Key Attribute	Value
Material	15-5PH Stainless Steel
UNS Number	S15500
Common Names	15-5PH, PH15-5, XM-12, 15Cr-5Ni
EN / W.Nr.	1.4545 / X5CrNiCu15-5
Material Type	Martensitic Precipitation-Hardening Stainless Steel
Density	Approx. 7.75–7.82 g/cm³
Main Advantage	High Strength, Good Corrosion Resistance & Improved Transverse Toughness
Typical Heat Treatment	Condition A, H900, H925, H1025, H1075, H1100, H1150, H1150M
Main Industries	Aerospace, Valves, Oil & Gas, Chemical Processing, Precision Engineering
Comparable Grades	17-4PH, 13-8Mo, 304, 316L

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Features of 15-5PH

Feature	Benefit
Precipitation-hardening stainless steel	Achieves high strength and hardness through aging heat treatment.
High tensile and yield strength	Suitable for load-bearing components, shafts, gears, valve parts and aerospace hardware.
Improved transverse toughness	Offers better toughness and ductility than 17-4PH in many applications.
Good corrosion resistance	Performs well in many atmospheric, mild chemical and industrial environments.
Multiple aging conditions	Allows engineers to balance strength, hardness, ductility and toughness.
Good machinability	Suitable for precision machining, CNC components and complex mechanical parts.
Good weldability	Can be welded with proper procedures and post-weld heat treatment when required.
Dimensional stability	Useful for precision parts requiring reliable performance after heat treatment.

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Chemical Composition of 15-5PH

Element	Composition
Carbon (C)	≤ 0.07%
Manganese (Mn)	≤ 1.00%
Phosphorus (P)	≤ 0.040%
Sulfur (S)	≤ 0.030%
Silicon (Si)	≤ 1.00%
Chromium (Cr)	14.00–15.50%
Nickel (Ni)	3.50–5.50%
Copper (Cu)	2.50–4.50%
Niobium / Columbium + Tantalum	0.15–0.45%
Iron (Fe)	Balance

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Physical Properties of 15-5PH

Property	Typical Value
Density	Approx. 7.75–7.82 g/cm³ / 0.280–0.283 lb/in³
Melting Range	Approx. 1404–1440°C / 2560–2625°F
Electrical Resistivity	Approx. 0.77–0.80 μΩ·m
Thermal Conductivity	Approx. 17.8–18.4 W/m·K
Specific Heat Capacity	Approx. 460 J/kg·K / 0.110 BTU/lb·°F
Modulus of Elasticity	Approx. 196–200 GPa / 28.5–29.0 × 10⁶ psi

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Mechanical Properties of 15-5PH

The mechanical properties of 15-5PH stainless steel depend strongly on heat treatment condition. H900 provides the highest strength and hardness, while H1025, H1075, H1100, H1150 and H1150M provide improved ductility and toughness with lower strength.

Condition	Tensile Strength	Yield Strength	Elongation	Hardness
H900	Approx. 190 ksi / 1310 MPa	Approx. 170 ksi / 1170 MPa	Approx. 6–10%	Approx. 388 HB / HRC 40
H925	Approx. 170 ksi / 1170 MPa	Approx. 155 ksi / 1069 MPa	Approx. 7–11%	Approx. HRC 38
H1025	Approx. 155 ksi / 1069 MPa	Approx. 145 ksi / 1000 MPa	Approx. 8–12%	Approx. 331 HB / HRC 35
H1075	Approx. 145 ksi / 1000 MPa	Approx. 125 ksi / 862 MPa	Approx. 9–13%	Approx. 311 HB / HRC 32
H1100	Approx. 140 ksi / 965 MPa	Approx. 115 ksi / 793 MPa	Approx. 10–14%	Approx. HRC 30–35
H1150	Approx. 135 ksi / 931 MPa	Approx. 105 ksi / 724 MPa	Approx. 11–16%	Approx. 277 HB / HRC 28
H1150M	Approx. 115 ksi / 793 MPa	Approx. 75 ksi / 517 MPa	Approx. 14–18%	Approx. 255 HB / HRC 25

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Corrosion Resistance

15-5PH stainless steel provides good general corrosion resistance in many atmospheric, industrial, and mildly chemical environments. Its corrosion resistance is generally comparable to 17-4PH and, in many media, close to Type 304 stainless steel.

For optimum corrosion resistance, the material should be properly heat treated, cleaned, descaled, and passivated after fabrication. Surface contamination, heat tint, scale, or embedded iron particles may reduce corrosion performance.

Environment	Performance	Notes
Atmospheric Exposure	Good	Suitable for many structural and precision components.
Humidity	Good to Excellent	Clean and passivated surfaces provide better performance.
Mild Chemical Media	Good	Performance depends on concentration, temperature, and exposure time.
Salt Spray	Moderate to Good	Surface finish and passivation are important.
Seawater	Restricted	Not recommended for continuous seawater service where pitting and crevice corrosion are critical.
Nitric Acid	Good	Suitable in selected concentrations and temperatures.
Sulfuric Acid	Restricted	Corrosion testing is recommended before use.
Chloride-Rich Environments	Limited	Use with caution in severe chloride, stagnant or crevice conditions.

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High Temperature Performance

15-5PH stainless steel offers useful oxidation resistance and strength retention at moderate elevated temperatures, but it is not a dedicated high-temperature alloy. Long-term exposure to elevated temperatures may reduce toughness or change mechanical properties, especially when service temperatures approach or exceed aging temperatures.

Temperature Factor	Performance Consideration
Oxidation Resistance	Good up to approximately 593°C / 1100°F in suitable environments.
Strength Retention	Good at moderate elevated temperatures, depending on heat treatment condition.
Long-Term Exposure	May reduce toughness or affect aged mechanical properties.
Short-Term Exposure	Can be considered if the service temperature remains below the aging temperature.
Engineering Recommendation	Evaluate service temperature, exposure time, load and required toughness before selection.

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Available Forms

J&A Alloy can supply 15-5PH stainless steel in standard and custom forms according to ASTM, AMS, ASME, EN and customer project requirements.

Available Form	Supply Options
Round Bar	Hot rolled, forged, peeled, turned, ground and polished.
Flat Bar	Cut-to-size, forged or machined according to drawing.
Square Bar	Standard or custom dimensions available.
Plate	Solution treated or aged condition, custom thickness available.
Sheet / Strip	Suitable for aerospace, precision parts, and formed components.
Forgings	Discs, rings, shafts, blocks, and near-net-shape components.
Billet / Ingot	For conversion, forging, or special-size production.
Wire	Available for selected fasteners, springs, and special applications.
Custom Machined Parts	CNC machining, cutting, heat treatment, and inspection support available.

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Applications of 15-5PH

15-5PH stainless steel is used in industries that require a combination of high strength, good corrosion resistance, good toughness, and reliable heat-treated properties.

Industry	Typical Components	Why 15-5PH Is Used
Aerospace	Structural parts, fittings, actuator parts, fasteners, and precision components.	High strength, good toughness, and aerospace specification availability.
Valve & Fluid Control	Valve stems, valve bodies, shafts, fittings, and high-strength valve parts.	High hardness, corrosion resistance, and dimensional stability.
Oil & Gas	Shafts, couplings, pressure-related components, and downhole parts.	Strength, toughness, and moderate corrosion resistance.
Chemical Processing	Pump parts, fittings, connectors and mechanical components.	Good corrosion resistance with high mechanical strength.
Nuclear	Reactor components and precision mechanical parts.	Reliable mechanical properties and good toughness.
General Engineering	Gears, shafts, fasteners, machine components and wear-resistant parts.	High strength-to-weight performance and good machinability.

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15-5PH vs 17-4PH

Item	15-5PH Stainless Steel	17-4PH Stainless Steel
UNS Number	S15500	S17400
Material Type	Martensitic precipitation-hardening stainless steel	Martensitic precipitation-hardening stainless steel
Strength	High strength after aging	High strength after aging
Transverse Toughness	Generally better	Good, but usually lower than 15-5PH
Ductility	Generally better in critical sections	Good
Corrosion Resistance	Similar to 17-4PH in many environments	Good general corrosion resistance
Best Use	High-strength parts requiring better toughness and ductility	General high-strength PH stainless applications

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15-5PH vs 13-8Mo

Item	15-5PH Stainless Steel	13-8Mo Stainless Steel
Strength Level	High	Very high depending on condition
Toughness	Good, better than 17-4PH in transverse direction	Excellent toughness for critical aerospace applications
Corrosion Resistance	Good general corrosion resistance	Good corrosion and stress-corrosion resistance
Cost	Usually more economical	Usually higher cost
Typical Selection	Valves, shafts, gears, aerospace parts and general high-strength components	Critical aerospace and high-performance applications

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15-5PH vs 304 Stainless Steel

Item	15-5PH Stainless Steel	304 Stainless Steel
Material Type	Martensitic precipitation-hardening stainless steel	Austenitic stainless steel
Strength	Much higher after aging	Moderate
Hardness	High	Low to moderate
Corrosion Resistance	Good general corrosion resistance	Good general corrosion resistance
Weldability	Good with proper procedure and heat treatment	Excellent
Best Use	High-strength mechanical parts	General corrosion-resistant fabrication

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Welding & Fabrication

15-5PH stainless steel can be welded and fabricated using suitable procedures. For critical applications, welding should be performed using qualified procedures, and post-weld heat treatment should be selected according to the required final strength, hardness, and toughness.

For best corrosion resistance, scale, heat tint, oxide, and contamination should be removed after hot working, welding, or machining. Passivation is recommended for components exposed to corrosive environments.

Process	Recommendation
Welding	Use qualified welding procedures. Post-weld heat treatment may be required to restore final mechanical properties.
Machining	Can be machined in solution-treated or aged condition. Rigid tooling and suitable cutting parameters are recommended.
Forging	Good forgeability. Controlled heating, working temperature and cooling are important.
Heat Treatment	Solution treatment followed by aging conditions such as H900, H1025, H1075, H1100, H1150 or H1150M.
Cold Working	Limited compared with austenitic stainless steels. Intermediate heat treatment may be needed for severe forming.
Surface Finishing	Pickling, polishing and passivation are recommended where corrosion resistance is important.

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Standards & Equivalent Grades

Category	Designation / Standard
UNS	S15500
Common Grade Names	15-5PH, PH15-5, 15Cr-5Ni, XM-12
ASTM	ASTM A564 Grade XM-12, ASTM A705 Grade XM-12, ASTM A484
ASME	ASME SA564
AMS	AMS 5659, AMS 5862, AMS 5826
EN / DIN Reference	1.4545 / X5CrNiCu15-5
Aerospace Melting Route	VAR or ESR depending on specification requirement
Material Family	Precipitation-Hardening Stainless Steel

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Frequently Asked Questions

What is 15-5PH stainless steel?

15-5PH stainless steel is a martensitic precipitation-hardening stainless steel containing chromium, nickel, copper and niobium. It is designed for high strength, good hardness, good corrosion resistance and improved toughness compared with 17-4PH.

Is 15-5PH the same as UNS S15500?

Yes. 15-5PH stainless steel is commonly designated as UNS S15500. It is also known as XM-12, PH15-5, 15Cr-5Ni and 1.4545 / X5CrNiCu15-5.

What is the difference between 15-5PH and 17-4PH?

Both 15-5PH and 17-4PH are precipitation-hardening stainless steels. 15-5PH is generally selected when better transverse toughness and ductility are required, while 17-4PH is widely used for general high-strength stainless steel applications.

What is the best heat treatment condition for 15-5PH?

The best heat treatment depends on the application. H900 provides the highest strength and hardness. H1025, H1075, H1100, H1150 and H1150M provide lower strength but better ductility and toughness.

Can 15-5PH stainless steel be welded?

Yes. 15-5PH stainless steel can be welded with proper welding procedures. For critical components, post-weld heat treatment should be considered to achieve the required mechanical properties.

Is 15-5PH suitable for seawater?

15-5PH has good general corrosion resistance, but it is not normally recommended for continuous seawater service where pitting and crevice corrosion are critical. For severe marine environments, duplex stainless steel, super duplex stainless steel or nickel alloys may be more suitable.

What forms of 15-5PH stainless steel are available?

J&A Alloy can supply 15-5PH stainless steel in round bar, flat bar, square bar, plate, sheet, forgings, billets, rings, wire and custom-machined components.

Which industries use 15-5PH stainless steel?

15-5PH is widely used in aerospace, valve manufacturing, oil & gas, chemical processing, nuclear, marine-related equipment, precision engineering, and high-strength mechanical components.

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Why Choose J&A Alloy

J&A Alloy supplies 15-5PH stainless steel for customers who need high-strength precipitation-hardening stainless materials with reliable documentation, flexible product forms, and engineering support.

J&A Alloy Advantage	What You Get
Material Expertise	Support for grade selection, heat treatment condition selection, and equivalent standard comparison.
Multiple Product Forms	Bars, plates, sheets, forgings, billets, rings, wire, and custom-machined parts.
Specification-Based Supply	Materials can be supplied according to ASTM, AMS, ASME, UNS, EN, and customer project specifications.
Quality Documentation	MTC / EN 10204 3.1, chemical analysis, mechanical test report and inspection documents available upon request.
Custom Processing	Cutting, machining, heat treatment coordination, surface finishing and export packaging support.
Application-Oriented Service	Material recommendations for aerospace, valve, oil & gas, chemical processing and precision engineering applications.

 

Contact J&A Alloy for 15-5PH stainless steel bar, plate, forging, sheet, billet or custom component inquiries. Our team can support material selection, equivalent grade comparison, heat treatment condition selection and export-ready supply.