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17-4PH

17-4PH is a typical martensitic precipitation-hardening stainless steel, combining corrosion resistance and ultra-high strength after aging heat treatment, widely used for high-load precision structural parts.

Typical Chemical Composition

  • Chromium (Cr): 15.0%–17.5% – Provides basic rust and oxidation resistance
  • Nickel (Ni): 3.0%–5.0% – Stabilizes matrix structure, improves toughness
  • Copper (Cu): 3.0%–5.0% – Main precipitation strengthening element to boost hardness and tensile strength during aging
  • Niobium (Nb): 0.15%–0.45% – Refines grains, inhibits carbide precipitation
  • Carbon (C): ≤0.07% – Low carbon to reduce intergranular corrosion
  • Balance: Iron with minor trace elements

Core Material Properties

  1. Adjustable High Strength & Hardness Strength and hardness can be customized via different aging temperatures (H900/H1025/H1075/H1150/H1175). The highest hardness reaches over 44 HRC, outstanding for wear-resistant and load-bearing components.
  2. Good Corrosion Resistance Corrosion performance is better than common 400-series martensitic stainless steel, close to 304 austenitic steel; resists atmospheric corrosion, fresh water and mild chemical media.
  3. Heat-Treatable Strengthening Feature It can be softened by solution treatment for forming/machining, then significantly hardened by low-temperature aging, which is its biggest advantage over 304/316.
  4. Moderate Formability Better ductility than fully martensitic stainless steel; suitable for MIM to produce complex small structural parts, no easy cracking during sintering.
  5. Magnetic Property Magnetic in all heat treatment states, not suitable for magnetic-sensitive electronic assemblies.
  6. Temperature Performance Maintains stable mechanical properties under medium-temperature working conditions; not recommended for long-term service above 315°C.

Machining & MIM Process Adaptability

  1. Metal Injection Molding (MIM) 17-4PH powder has stable flowability, achieves high density after debinding and sintering. Perfect for miniature gears, hinge shafts, tow hooks, medical load-bearing tools and automotive structural parts with complex thin-wall geometry.
  2. Compatible Surface Treatments Supports polishing, sandblasting, passivation, PVD coating, meeting both mechanical and decorative requirements.
  3. Standard Heat Treatment Flow Solution treatment (high temperature holding + rapid cooling) → low-temperature aging to precipitate copper-rich phases, greatly improving hardness, tensile strength and yield strength.

Advantages & Disadvantages

Advantages

  • Tunable ultra-high strength and hardness via aging heat treatment
  • Balanced corrosion resistance and mechanical performance, superior to 410/420 martensitic steel
  • Excellent dimensional stability after heat treatment, ideal for precision transmission parts
  • High toughness, resistant to impact fracture under heavy load

Disadvantages

  • Higher material cost than 304
  • Magnetic, cannot be used for magnetic interference-sensitive equipment
  • Inferior chloride corrosion resistance compared to 316, unsuitable for long-term salt spray coastal environments
  • Hardened state has reduced ductility, difficult for secondary bending forming

Typical Applications

  1. Power Transmission & Gear Systems: Gear shafts, lock cores, small transmission gears
  2. Automotive Parts: Tow hooks, high-strength interior structural brackets
  3. Audio Equipment: Load-bearing rotating hinges, structural brackets
  4. Medical Devices: High-torque surgical industrial tools, clamping forceps with heavy load
  5. Industrial Precision Hardware: High-strength connectors, hydraulic miniature valve parts