15-5 PH Stainless Steel
Also: 15-5PH, UNS S15500, XM-12, 1.4545, X5CrNiCu15-5, Armco 15-5 PH, ferrite-free 17-4
15-5 PH is the remelted, ferrite-free cousin of 17-4 PH: the same strength and aging cycles with better toughness across the grain. Chosen for forgings and thick sections.
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At a glance
| Density | 7.8 g/cm³ (0.282 lb/in³) |
|---|---|
| Tensile strength | H900 1310-1380 MPa (190-200 ksi); H1025 1070-1170 MPa (155-170 ksi); H1150 930-1000 MPa (135-145 ksi); Condition A about 1000 MPa (145 ksi) |
| Yield strength | H900 1170-1275 MPa (170-185 ksi); H1025 1000-1140 MPa (145-165 ksi); H1150 725-860 MPa (105-125 ksi); Condition A about 760 MPa (110 ksi) |
| Hardness | H900 40-47 HRC; H1025 35-38 HRC; H1150 28-33 HRC; Condition A about 33 HRC (363 HB maximum) |
| Elongation | H900 10-14%; H1025 12-15%; H1150 16-19%; Condition A about 10% |
| Modulus of elasticity | 196 GPa (28.5 Msi) |
| Thermal | Melts at 1400-1440 °C (2560-2625 °F); thermal conductivity ~18 W/m·K; expansion ~10.8 um/m·K; service to about 315 °C (600 °F) |
| Composition | Fe, 14-15.5% Cr, 3.5-5.5% Ni, 2.5-4.5% Cu, 0.15-0.45% Nb (+Ta), up to 0.07% C, up to 1% Mn, up to 1% Si |
Typical values, Aged conditions, ASTM A564 minimums to typical upper values: H900 = 482 °C (900 °F) 1 h; H1025 = 552 °C (1025 °F) 4 h; H1150 = 621 °C (1150 °F) 4 h; Condition A = solution annealed at 1040 °C (1900 °F). Confirm against the mill certificate and the purchase spec.
- MachinabilityFair
- The same as 17-4 PH, about 45-50% of B1112 in Condition A or the overaged conditions, with slightly more uniform chip behaviour because there are no ferrite stringers. Machine soft, age, finish critical features.
- WeldabilityGood
- Welds like 17-4 PH with ER630 or matching 15-5 filler and no preheat, and the ferrite-free structure gives a slightly tougher heat-affected zone. Weld soft, then age the assembly.
- FormabilityFair
- Sheet in Condition A is about 33 HRC: bend at 2-3t inside radius with heavy tonnage, then age. Nothing forms after aging.
- Corrosion resistanceGood
- About the same as 17-4 PH, near 304 in atmosphere and fresh water, below 316 in chlorides. Overaged conditions resist stress-corrosion and hydrogen cracking far better than H900. Passivate after machining.
15-5 PH is a martensitic precipitation-hardening stainless developed to fix the one weakness of 17-4 PH: the delta-ferrite stringers that leave large 17-4 bar and forgings brittle in the transverse direction. Slightly less chromium, a little more nickel and consumable-electrode remelting give a ferrite-free martensite with the same copper-precipitation strengthening. Condition A, H900, H1025, H1075, H1100 and H1150 mean the same temperatures, times and minimum properties as for 17-4 PH.
It is the aerospace default among the PH grades: AMS 5659 bar and forgings go into aircraft fittings, actuator and landing-gear components, helicopter parts, valve bodies and shafts, and it is the standard choice for thick plate and large forgings where 17-4 would fail an impact or transverse tensile test. It welds, forges, machines and passivates like 17-4 PH, and it is magnetic in every condition.
The trade is price and availability: 15-5 costs more than 17-4, comes from fewer mills, and is stocked in fewer sizes. For small bar, sheet and light forgings 17-4 PH is the same material at lower cost. Everything said about 17-4 PH conditions applies: never use Condition A in service, use H1025 or higher for toughness, H1150 or H1150M for chlorides and sour service.
Heat treatment
Identical to 17-4 PH: solution treat at 1040 °C (1900 °F) and cool below 32 °C (90 °F) for Condition A, then a single age at 482 °C (900 °F) 1 h for H900, or 4 h at 496, 552, 579, 593 or 621 °C (925, 1025, 1075, 1100 or 1150 °F) for H925 through H1150; H1150M is 760 °C (1400 °F) 2 h followed by 621 °C 4 h. Air cool; contraction of roughly 0.05-0.1% on aging. Follow AMS 2759/3.
Tempers and conditions
- Condition A (solution annealed, as purchased)
- H900
- H925
- H1025
- H1075
- H1100
- H1150
- H1150M (double overaged)
Stock forms
- Round and flat bar (Condition A)
- Forgings and forging stock
- Plate and sheet (Condition A)
- Investment castings (CB7Cu-2 equivalent)
- Metal 3D printing powder (limited)
Relative cost
Tier 4 of 5. About 1.2-1.5x 17-4 PH bar per pound because of remelting, and fewer stocked sizes; still well under titanium. Buy 17-4 PH for small bar and sheet unless the drawing or the transverse test says 15-5.
Typical applications
- Aircraft structural fittings, lugs and actuator components
- Landing-gear and flight-control parts
- Helicopter rotor and transmission components
- Large pump and valve shafts and bodies
- Nuclear and petrochemical fasteners and forgings
- Thick-section tooling and fixtures needing corrosion resistance
Process compatibility
How 15-5 PH takes each process, and what to specify. Each process links to its own guide and to the shops that do it.
| Process | Rating | Notes |
|---|---|---|
| CNC Machining | FairFair | Same practice as 17-4 PH: machine in Condition A or H1150 with coated carbide, age, then finish; allow 0.05-0.1% contraction. |
| CNC Milling | FairFair | Fittings and lugs from plate and bar; hard-mill H1025 details with sharp coated tooling and light radial engagement. |
| Forging | ExcellentExcellent | The reason to buy 15-5: forge at about 1150-1200 °C (2100-2200 °F), solution treat, and get sound transverse properties in large sections. |
| Heat Treating | ExcellentExcellent | One air-furnace age with no quench and little distortion; specify the condition and AMS 2759/3. |
| Vacuum Heat Treating | GoodGood | Solution anneal and age in vacuum for finished parts that must stay bright and clean. |
| Welding | GoodGood | ER630 or matching filler, no preheat; weld in Condition A or an overaged condition and age afterward. |
| Wire EDM | GoodGood | Profiles aged stock at any hardness without distortion; the route for H900 lugs and slots. |
| Passivation | ExcellentExcellent | ASTM A967 citric after aging and final machining, the standard aerospace call-out with AMS 2700. |
| Shot Peening | GoodGood | Peening after aging (AMS 2430) raises fatigue life of fittings and shafts; specify intensity and coverage. |
| Nondestructive Testing (NDT) | GoodGood | Aerospace forgings are routinely ultrasonic and penetrant inspected; specify AMS 2630 / ASTM E1417 when the part is fracture critical. |
| Press Brake Forming | FairFair | Condition A sheet bends at 2-3t with heavy tonnage; form first, then age. |
| Hot-Dip Galvanizing | Not recommendedNot recommended | Zinc does not bond to the passive oxide, adds nothing, and the bath temperature overages the alloy. |
Compare 15-5 PH
Design and sourcing tips
- Specify "15-5 PH per AMS 5659 (or ASTM A564 XM-12), Condition H1025" with the condition always named; Condition A is not a service condition.
- Use 15-5 when the part is a forging, is cut from plate or bar over about 75 mm (3") or is loaded across the grain; use 17-4 PH otherwise.
- Call transverse tensile or impact requirements on the drawing if they matter; that is the property 15-5 is bought for and the mill can certify it.
- Machine in Condition A or H1150, age, then finish-machine; allow 0.05-0.1% linear shrink.
- For chlorides, hydrogen or sour service, specify H1150 or H1150M and cap hardness at 33 HRC per NACE MR0175.
Frequently asked questions
- Is 15-5 PH stainless magnetic?
- Yes, in every condition. It is martensitic like 17-4 PH, so a magnet sticks in Condition A and after aging. Non-magnetic requirements need an austenitic grade.
- What is the difference between 15-5 PH and 17-4 PH?
- Both are copper-hardened martensitic stainless steels with the same aging cycles and the same minimum strengths per condition. 15-5 has slightly less chromium and more nickel and is consumable-electrode remelted, which removes the delta-ferrite stringers that make large 17-4 bar and forgings weak and brittle across the grain. Buy 15-5 for forgings and thick sections; 17-4 is cheaper for the rest.
- Can 15-5 PH be welded?
- Yes, by TIG, MIG and laser with ER630 or matching 15-5 filler and no preheat. Weld in Condition A or an overaged condition, then age the whole assembly so the weld and base metal end up at the same strength. The ferrite-free structure gives a slightly tougher weld zone than 17-4 PH.
- What hardness is 15-5 PH H1025?
- About 35-38 HRC, with a minimum tensile strength of 1070 MPa (155 ksi) and yield of 1000 MPa (145 ksi) per ASTM A564. H900 reaches 40-47 HRC and H1150 drops to 28-33 HRC; H1025 is the usual compromise between strength and toughness.
Processes that commonly use it
Related materials
Where to verify these values
- ASTM A564 and ASTM A693 (Type XM-12 minimums by condition)
- AMS 5659 and AMS 5862; AMS 2759/3 for heat treatment
- MMPDS design allowables
- Producer data sheets (Cleveland-Cliffs / AK Steel 15-5 PH, Carpenter Custom 15-5)
