Excellent Mechanical Strength and Corrosion Resistance of 17-4PH Stainless Steel
17-4PH stainless steel is a precipitation-hardening martensitic stainless steel known for its excellent combination of high strength, good corrosion resistance, and outstanding mechanical properties up to 600 °F (316 °C). It is widely used in aerospace, chemical, marine, and energy industries for components requiring high strength and moderate corrosion resistance.
This article introduces the composition, properties, and key applications of 17-4PH to support effective material selection in engineering and manufacturing.
What is 17-4PH Stainless Steel?
17-4PH (UNS S17400, ASTM A564 Type 630) is a chromium-nickel-copper steel that gains strength through precipitation hardening. The “17-4” stands for 17% chromium and 4% nickel content. After heat treatment, it achieves high tensile strength and hardness, with minimal distortion during aging.
It combines the corrosion resistance of austenitic grades with the strength of martensitic steels, making it a popular choice in critical mechanical and structural applications.
17-4PH Equivalent Grades
| Standard / System | Equivalent Designation |
| UNS | S17400 |
| ASTM / ASME | ASTM A564, A693, A705 |
| EN / DIN | 1.4542 / X5CrNiCuNb16-4 |
| SAE | Type 630 |
| JIS | SUS 630 |
17-4PH Chemical Composition
| Element | Content (%) |
| Chromium (Cr) | 15.0 – 17.5 |
| Nickel (Ni) | 3.0 – 5.0 |
| Copper (Cu) | 3.0 – 5.0 |
| Niobium (Nb) + Tantalum (Ta) | 0.15 – 0.45 |
| Carbon (C) | ≤ 0.07 |
| Manganese (Mn) | ≤ 1.0 |
| Silicon (Si) | ≤ 1.0 |
| Phosphorus (P) | ≤ 0.040 |
| Sulfur (S) | ≤ 0.030 |
17-4PH Mechanical Properties (Typical, H900 Condition)
| Property | Typical Value |
| Tensile Strength | ~1310 MPa |
| Yield Strength | ~1170 MPa |
| Elongation | ~10% |
| Hardness (HRC) | ~40 |
Note: Mechanical properties vary depending on heat treatment condition (H900, H1025, H1150, etc.)
17-4PH Physical Properties
| Property | Value |
| Density | 7.75 g/cm³ |
| Melting Point | ~1400 °C |
| Thermal Conductivity | 18 W/m·K (at 100 °C) |
| Electrical Resistivity | ~0.80 µΩ·m |
| Modulus of Elasticity | ~200 GPa |
| Service Temperature Range | Up to 316 °C (600 °F) |
Applications of 17-4PH Stainless Steel
- Aerospace Components: Shafts, fasteners, turbine parts.
- Chemical Processing Equipment: Valves, pump shafts, and agitators.
- Nuclear and Power Generation: Steam and gas turbine parts.
- Oil and Gas Industry: Downhole tools, connectors.
- Medical Equipment: Surgical tools and orthopedic implants.
- Marine Applications: Propeller shafts, bolts, and structural parts.
Advantages of 17-4PH
- High strength and hardness after heat treatment.
- Good corrosion resistance, comparable to 304 in many environments.
- Excellent mechanical properties up to 600 °F (316 °C).
- Good machinability and weldability in solution-annealed condition.
- Dimensional stability during aging and hardening treatments.
Limitations of 17-4PH
- Lower corrosion resistance than 316L in chloride-rich or highly acidic environments.
- Not suitable for very high-temperature service (above ~600 °F).
- Sensitive to hydrogen embrittlement in some applications.
- Requires precise heat treatment to achieve target properties.
17-4PH vs Other Stainless Steels
| Feature | 304 / 316 | 17-4PH | Duplex 2205 |
| Strength | Low–Med | High | High |
| Corrosion Resistance | High | Medium | High |
| Heat Treatable | No | Yes | No |
| Magnetic | Non-mag | Magnetic | Slightly magnetic |
| Weldability | Excellent | Good | Moderate |
Summary
17-4PH stainless steel is a versatile and widely used precipitation-hardened alloy that offers a unique combination of strength, hardness, and corrosion resistance. It performs well in demanding environments and is easily fabricated and heat-treated.
MT.BOLTS provides 17-4PH fasteners, rods, and components for aerospace, marine, energy, and mechanical industries. Contact us for custom parts, technical support, or to request a quote.
