17‑4 PH Fasteners: Complete Technical Properties – Tensile, Yield, Hardness, Torque, Fatigue, Heat Treatment & More

When specifying 17‑4 PH stainless steel fasteners, engineers need precise, reliable data on mechanical properties, heat treatment response, torque values, and environmental performance. As a specialist global manufacturer of 17‑4 PH bolting with over two decades of in‑house experience, RAYCHIN LIMITED presents this comprehensive technical reference. All data is drawn from actual production lots and international standards, providing you with the authoritative information required to design robust, safe bolted joints.

1. Mechanical Properties: Tensile Strength, Yield Strength & Hardness

17‑4 PH tensile strength and 17‑4 PH yield strength vary significantly with heat treatment condition. The table below presents typical values per ASTM A564 Type 630, which are verified on every RAYCHIN production lot.

17‑4 PH yield strength H900 reaches 170 ksi (1170 MPa)—making it one of the highest‑strength corrosion‑resistant fastener alloys available at room temperature. 17‑4 PH hardness H1025 typically falls between 34–42 HRC, providing an optimal balance of strength and toughness for aerospace structural and landing gear applications. RAYCHIN verifies hardness on 100% of fasteners in every shipment.

2. Torque Values & Bolt Tightening Torque Chart

Achieving the correct preload without galling requires accurate 17‑4 PH torque values. Because 17‑4 PH has a higher friction coefficient than carbon steel, lubrication significantly affects the torque‑tension relationship. RAYCHIN provides a conservative guideline based on 50% of yield strength with a lubricated nut factor K = 0.15.

These values assume clean threads with a nickel‑compatible anti‑seize compound. RAYCHIN can provide a detailed 17‑4 PH bolt tightening torque chart specific to your fastener geometry, coating, and target preload. Always use calibrated torque wrenches and a slow, steady application speed to avoid galling.

3. Fatigue Strength

17‑4 PH fatigue strength depends on condition, surface finish, and thread geometry. In rotating‑beam fatigue testing (smooth bar, room temperature), the endurance limit at 10⁷ cycles is approximately 620 MPa (90 ksi) for H900 and 520 MPa (75 ksi) for H1025. For threaded fasteners, the fatigue strength is lower due to stress concentration at the thread root. RAYCHIN's rolled‑after‑heat‑treatment threads introduce compressive residual stresses at the thread root, significantly improving fatigue life compared to cut threads—a critical advantage in rotating equipment, valve actuators, and aerospace structures.

4. Galling Resistance and Prevention

17‑4 PH galling resistance is moderate. The alloy's martensitic microstructure is less prone to galling than austenitic stainless steels (304/316), but its high strength means that significant contact pressures develop at the thread interface. Under high‑speed assembly or dry conditions, adhesive wear can still occur. RAYCHIN prevents galling through:

• Rolled threads—smoother surface finish than cut threads, reducing friction.
• Pre‑applied anti‑seize coatings—MoS₂, boron nitride, or cermet‑based solid film lubricants applied in‑house.
• Dissimilar nut material—pairing a 17‑4 PH bolt with a Nitronic 60 or Inconel 625 nut disrupts the metal‑to‑metal adhesion path.
• Slow, controlled tightening—no impact tools; use hydraulic or electric torque wrenches with continuous torque monitoring.

5. Machinability

17‑4 PH machinability is rated at approximately 40–50% of free‑cutting steel (B1112) in the solution‑annealed condition. After aging to H900 or higher, the material becomes significantly harder and more difficult to machine. RAYCHIN performs the majority of machining—turning, drilling, threading—in the solution‑annealed (Condition A) state, followed by vacuum aging to the specified condition. This process route preserves tool life and dimensional accuracy while guaranteeing the correct final mechanical properties. Our CNC machining centers are equipped with rigid setups, positive‑rake carbide tooling, and high‑pressure coolant delivery specifically optimized for precipitation‑hardened stainless steels.

6. Heat Treatment: Solution Anneal and Age

The 17‑4 PH heat treatment cycle is fundamental to achieving the required properties. The complete 17‑4 PH solution anneal and age sequence performed by RAYCHIN in vacuum furnaces is:

1. Solution annealing (Condition A): Heat to 1040°C ± 15°C (1900°F ± 25°F), hold for 30–60 minutes depending on cross‑section, followed by rapid oil or water quenching. This dissolves all copper‑rich precipitates and transforms the microstructure to a low‑carbon martensite with high dislocation density.
2. Precipitation aging: Reheat to the specified temperature for the desired condition—480°C (900°F) for H900, 552°C (1025°F) for H1025, 580°C (1075°F) for H1075, 620°C (1150°F) for H1150, or double‑age at 620°C for H1150D. The aging temperature directly controls the size and distribution of copper‑rich precipitates, which determine the final strength and hardness.

For H1150D, the double‑aging cycle transforms a portion of the martensite into stable, reversed austenite, which acts as a crack arrestor and is essential for sulfide stress cracking resistance in NACE MR0175 environments. RAYCHIN's vacuum aging furnaces are NADCAP‑accredited for aerospace work, and complete furnace charts are included with every certification package.

7. Maximum Temperature Use and Low Temperature Properties

17‑4 PH maximum temperature use depends on the heat treatment condition. In general:

• H900: Continuous service limited to about 315°C (600°F). Above this temperature, the copper‑rich precipitates rapidly coarsen and strength collapses.
• H1150 / H1150D: Can operate up to approximately 370°C (700°F) due to the more stable precipitate structure, though with lower initial strength.

For applications requiring high strength above 315°C, RAYCHIN recommends upgrading to A286 (up to 650°C) or Inconel 718 (up to 704°C).

17‑4 PH low temperature properties are excellent. The alloy retains good ductility and impact toughness down to -196°C (-320°F), with Charpy V‑notch values in the H1025 condition typically exceeding 40 J (30 ft‑lbf) at cryogenic temperatures. This makes 17‑4 PH suitable for LNG piping bolting, cryogenic valve components, and liquid oxygen pump fasteners. There is no ductile‑to‑brittle transition, and the fracture mode remains ductile.

8. Stress Corrosion Cracking and Hydrogen Embrittlement Resistance

17‑4 PH stress corrosion cracking resistance is strongly dependent on heat treatment condition and hardness. H900, with its high hardness (40–47 HRC), is susceptible to chloride SCC, particularly above 60°C in marine or chemical environments. H1025 and H1075 offer improved resistance due to their lower hardness and slightly more stable microstructure. H1150 and H1150D provide the best SCC resistance, which is why they are mandated for NACE MR0175 sour service and are preferred for chemical processing and nuclear applications.

17‑4 PH hydrogen embrittlement is a risk primarily in the high‑strength conditions (H900, H925). Atomic hydrogen, introduced through electrolytic plating processes or from cathodic protection systems in service, can diffuse into the martensitic matrix and cause delayed brittle fracture. RAYCHIN mitigates this by:

• Strictly avoiding electrolytic zinc or cadmium plating—we use only passivation (AMS 2700) or hydrogen‑free solid film lubricants.
• Baking when necessary—if any wet chemical process is used, fasteners are immediately baked at 190–220°C for 24 hours to drive out diffusible hydrogen.
• Recommending H1025 or lower hardness for applications with any hydrogen charging risk, such as subsea cathodic protection or sour gas exposure.

9. RAYCHIN's Technical Data Commitment

Every 17‑4 PH fastener shipment from RAYCHIN LIMITED is accompanied by a full quality dossier: chemical analysis (OES), tensile test results (yield, ultimate, elongation, reduction of area), hardness readings (100% verification), PMI report, and EN 10204 Type 3.1 certificate (Type 3.2 on request). Our application engineers are available to provide condition‑specific S‑N fatigue curves, stress‑relaxation data, and customized torque tables to support your design and procurement process.