17-7PH Stainless Steel Bar
Semi-austenitic precipitation-hardening stainless steel bar for premium aerospace applications
17-7PH stainless steel bar combines the austenitic base structure with precipitation hardening to deliver exceptional strength exceeding 1,550 MPa while maintaining excellent toughness and corrosion resistance. Purpose-designed for critical aerospace components and high-reliability industrial applications.
Quick Specifications
- UNS Designation
- S17700
- Werkstoff Number
- 1.4568
- Yield Strength (RH950)
- 1,550 MPa (225 ksi) minimum
- Tensile Strength (RH950)
- 1,690 MPa (245 ksi) minimum
- Elongation (RH950)
- 8% minimum
- Density
- 7.80 g/cm³
Standards & Certifications
Product Description
17-7PH is a semi-austenitic precipitation-hardening stainless steel engineered for applications requiring the ultimate combination of high strength, exceptional toughness, and superior corrosion resistance. Unlike fully martensitic precipitation-hardening grades, 17-7PH develops its strength through a controlled transformation from austenite to martensite during cooling from solution treatment, followed by precipitation hardening. This unique metallurgical pathway creates a microstructure that combines the toughness and corrosion resistance advantages of austenite with the strength benefits of controlled precipitation hardening.
The chemical composition with 17% chromium, 7% nickel, and precisely controlled aluminum content results in superior stress corrosion cracking resistance compared to martensitic stainless steels. The material exhibits excellent toughness even at cryogenic temperatures, making it ideal for applications involving thermal cycling or exposure to extreme temperature variations. After solution treatment at elevated temperature and careful controlled cooling, the material develops a retained austenite phase that significantly enhances fracture toughness and fatigue resistance.
17-7PH achieves yield strengths exceeding 1,550 MPa in the RH950 condition while maintaining elongation above 8% and Charpy impact strength of 60+ joules. This exceptional combination of strength and toughness is difficult to achieve in other materials and explains the premium value of 17-7PH in critical aerospace applications where component failure is not an option. The material is immune to stress corrosion cracking in seawater and chloride solutions up to the highest achievable strength levels.
The controlled rolling and precise heat treatment processing of 17-7PH bars ensures exceptional internal cleanliness and uniform microstructure. Vacuum induction melting followed by vacuum arc remelting eliminates segregation and ensures that mechanical properties are consistent throughout the bar cross-section. This level of metallurgical quality is essential for aircraft components, high-reliability fasteners, and systems where component integrity is critical to operational safety.
Specifications
| UNS Designation | S17700 |
| Werkstoff Number | 1.4568 |
| Yield Strength (RH950) | 1,550 MPa (225 ksi) minimum |
| Tensile Strength (RH950) | 1,690 MPa (245 ksi) minimum |
| Elongation (RH950) | 8% minimum |
| Density | 7.80 g/cm³ |
| Yield Strength (Annealed) | 515 MPa (75 ksi) |
| Modulus of Elasticity | 200 GPa |
| Thermal Conductivity | 11.4 W/m·K at 20°C |
| Coefficient of Linear Expansion | 10.8 × 10⁻⁶ /°C (0-100°C) |
| Fatigue Strength (RH950) | 580 MPa at 10⁷ cycles |
| Hardness Range (RH950) | 43-49 HRC |
Chemical Composition
| Element | Content (%) |
|---|---|
| Chromium (Cr) | 16.0-18.0 |
| Nickel (Ni) | 6.5-7.75 |
| Molybdenum (Mo) | 2.0-3.0 |
| Aluminum (Al) | 1.0-1.4 |
| Carbon (C) | 0.09 max |
| Manganese (Mn) | 0.10 max |
| Silicon (Si) | 0.10 max |
| Phosphorus (P) | 0.010 max |
| Sulfur (S) | 0.008 max |
| Iron (Fe) | Balance |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength (Annealed) | 860 MPa |
| Reduction of Area (Annealed) | 55% minimum |
| Charpy Impact (V-notch, RH950) | 60-80 J at room temperature |
| Charpy Impact (V-notch, -196°C) | 50-65 J (cryogenic toughness) |
| Fracture Toughness (K₁c, RH950) | 70-85 MPa√m |
| Fatigue Crack Growth Rate | Excellent resistance to fatigue crack propagation |
Key Features & Advantages
Applications
Critical Aerospace Fasteners
Aircraft fasteners, structural bolts, and high-reliability fastening systems where absolute reliability and resistance to failure under combined mechanical and corrosive loads are mandatory requirements.
Aircraft Landing Gear
Landing gear actuators, rod ends, bushings, and structural components requiring exceptional strength, toughness, and fatigue performance during dynamic loading and severe thermal cycling.
Engine Rotor Shafts
Jet engine rotor shafts, bearing races, and critical rotating components where high strength, low density, and excellent fatigue properties are essential for long service life.
Missile and Ordnance Components
Missile body sections, guidance system components, and ordnance devices requiring maximum strength-to-weight ratio with exceptional reliability and immunity to stress corrosion cracking.
Submarine and Naval Equipment
Submarine structural elements, hull materials, and naval systems operating at depth with requirements for superior strength, toughness, and corrosion resistance in seawater environments.
Cryogenic Equipment
Cryogenic valve components, LNG equipment, and low-temperature vessels where toughness and mechanical reliability must be maintained at sub-zero operating temperatures.
Frequently Asked Questions
What makes 17-7PH superior to other high-strength stainless steels?
What is the RH950 condition and how is it achieved?
Is 17-7PH suitable for cryogenic applications?
How does 17-7PH perform compared to Inconel X-750 for aerospace applications?
What is the expected cost difference between 17-7PH and standard stainless steels?
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