17-4PH Stainless Steel (UNS S17400): Properties, Heat Treatment & Applications
AMS 5643 / ASTM A564 · Published: 2026-06-01 · Updated: 2026-06-02
17-4PH is a martensitic precipitation-hardening stainless steel that combines high strength (up to 1,240 MPa yield) with corrosion resistance comparable to Type 304. The precipitation hardening mechanism — copper-rich epsilon-phase precipitates...
17-4PH is a martensitic precipitation-hardening stainless steel that combines high strength (up to 1,240 MPa yield) with corrosion resistance comparable to Type 304. The precipitation hardening mechanism — copper-rich epsilon-phase precipitates formed during aging at 480-620°C — enables strength levels unattainable by conventional martensitic (410, 420) or austenitic (304, 316) grades. 17-4PH is the most widely used precipitation-hardening stainless steel, serving in aerospace structural components, pump shafts, valve stems, and food processing equipment.
Heat treatment involves two steps: 1) solution annealing at 1,040°C for 30 minutes followed by air cooling or oil quenching (transforms to martensite), and 2) aging at one of several conditions — H900 (480°C, highest strength), H1025 (550°C, balanced), H1150 (620°C, highest toughness). Condition H900 provides peak strength but with notch sensitivity in hydrogen environments; H1150 provides the best combination of strength and environmental cracking resistance. The material is weldable in the solution-annealed condition but post-weld aging is required to develop full strength.
Quick Facts
| Category | Stainless Steel |
| Standard | AMS 5643 / ASTM A564 |
| Density | 7800 kg/m³ |
| Yield Strength | 1,100-1,240 MPa (Condition H900-H1025) |
| Tensile Strength | 1,310-1,380 MPa |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| UNS S17400 | Compare |
| X5CrNiCuNb16-4 (EN 1.4542) | Compare |
| SUS 630 (JIS) | Compare |
Related Materials
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Frequently Asked Questions
What is the difference between 17-4PH and 15-5PH?
17-4PH and 15-5PH have nearly identical mechanical properties and corrosion resistance. The key difference: 15-5PH is produced by vacuum arc remelting (VAR) which provides cleaner microstructure with fewer inclusions. 15-5PH is specified when transverse mechanical properties (ductility, impact) are critical — the cleaner microstructure provides superior transverse toughness compared to 17-4PH.
References & International Standards
- ASTM International. Standard Specifications for Steel & Metal Alloys. astm.org
- International Organization for Standardization (ISO). Metallic Materials — Cross-Reference Database. iso.org
- American Iron and Steel Institute (AISI). Steel Grade Designations & Equivalents. steel.org
- European Committee for Standardization (CEN). EN Steel Standards & Numbering System. cencenelec.eu