AISI 17-4PH Precipitation Hardening Stainless Steel — Properties, Heat Treatment & Equivalents
ASTM A564 Grade 630 (UNS S17400) · Published: 2026-06-14 · Updated: 2026-06-17
17-4PH is the most widely used precipitation hardening stainless steel, combining high strength (comparable to many alloy steels), excellent corrosion resistance (approaching 304 in many environments), and good fabrication characteristics. Its...
17-4PH is the most widely used precipitation hardening stainless steel, combining high strength (comparable to many alloy steels), excellent corrosion resistance (approaching 304 in many environments), and good fabrication characteristics. Its unique combination of properties comes from a martensitic matrix strengthened by copper-rich precipitates formed during aging.
The H900 condition (aged at 480°C/900°F) delivers the highest strength — approximately 1,240 MPa yield — but with reduced toughness and increased susceptibility to stress corrosion cracking in chloride environments. The H1150 condition (aged at 620°C/1150°F) sacrifices approximately 25% of the peak strength but dramatically improves toughness, ductility, and stress corrosion cracking resistance. Most aerospace applications specify H1025 or H1075 as a balanced compromise.
Key applications: aerospace structural components, pump shafts, valve stems, marine propeller shafts, nuclear waste containers, and food processing equipment where both strength and corrosion resistance are required. Not recommended for service above 315°C (600°F) — the copper precipitates coarsen and strength drops rapidly.
Quick Facts
| Category | Stainless Steel |
| Standard | ASTM A564 Grade 630 (UNS S17400) |
| Density | 7750 |
| Yield Strength | 1,100-1,240 MPa (H900 to H1150 conditions) |
| Tensile Strength | 1,310-1,380 MPa |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| EN 1.4542 | Compare |
| X5CrNiCuNb16-4 | Compare |
| JIS SUS630 | Compare |
| GB 0Cr17Ni4Cu4Nb | Compare |
Related Materials
🧮 Material Weight Calculator
Calculate the weight based on this material's density: 7750
Frequently Asked Questions
17-4PH vs 15-5PH — what's the difference?
15-5PH (UNS S15500) is a variant with a modified composition that improves transverse toughness — the Cr and Ni are adjusted to eliminate delta ferrite stringers that reduce toughness in the short-transverse direction. For applications where the material will be stressed in multiple directions (e.g., fittings, forgings with complex geometry), 15-5PH is preferred. For simpler geometries loaded primarily in the longitudinal direction, 17-4PH performs equivalently at lower cost.
Can 17-4PH be used in contact with salt water?
It depends on the aging condition and the specific environment. In the H1150 condition, 17-4PH has good resistance to marine atmospheric corrosion. However, it is susceptible to pitting and crevice corrosion in stagnant seawater and to stress corrosion cracking in warm chloride environments — particularly in the higher-strength H900 condition. For critical marine fasteners, consider Nitronic 50 (UNS S20910) or a duplex stainless steel instead.
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