17-4PH UNS S17400/W.Nr:1.4542 stainless steel
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17-4PH UNS S17400/W.Nr:1.4542 stainless steel is a precipitation hardening (PH) stainless steel with high strength, good corrosion resistance and good dimensional stability after heat treatment.
Standards and Certifications
ASTM standards: ASTM A564 (bars), ASTM A705 (forgings).
EN standards: EN 10088-3 (plates), EN 10272 (bars).
1. Material Composition
| Element | Content (%) |
|---|---|
| C | ≤0.07 |
| Cr | 15.5–17.5 |
| Ni | 3.0–5.0 |
| Cu | 3.0–5.0 |
| Nb + Ta | 0.15–0.45 |
| Mn | ≤1.0 |
| Si | ≤1.0 |
| S | ≤0.03 |
| P | ≤0.04 |
2. Mechanical Properties
Properties vary by heat treatment condition (e.g., H900, H1025, H1150). Typical values:
| Condition | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) | Hardness (HRC) |
|---|---|---|---|---|
| H900 | ≥1170 | ≥1310 | ≥10 | 40–45 |
| H1025 | ≥1000 | ≥1070 | ≥12 | 35–40 |
| H1150 | ≥795 | ≥930 | ≥16 | 30–35 |
| Annealed | ≥380 | ≥760 | ≥25 | ≤30 |
3. Heat Treatment
Solution Annealing:
Heat to 1040–1065°C (1900–1950°F), quench in water or air.
Age Hardening:
H900: 480°C (900°F) for 1–4 hours → maximum strength.
H1025: 550°C (1025°F) for 4 hours → balance of strength and ductility.
H1150: 620°C (1150°F) for 4 hours → highest ductility.
4. Corrosion Resistance
General Corrosion: Similar to 304 stainless steel in oxidizing environments.
Pitting/Crevice Corrosion: Improved resistance compared to 304 due to higher Cr and Mo (if present), but less than 316.
Stress Corrosion Cracking (SCC): Resistant to SCC in chloride environments when properly heat-treated.
What is the difference between 17-4PH stainless steel and 304 stainless steel?
17-4PH stainless steel exhibits corrosion resistance comparable to 304 stainless steel under solid solution and medium temperature aging conditions, especially in the atmosphere, fresh water and dilute acid environments. Its corrosion resistance is better than that of traditional martensitic stainless steel (such as 431), but it is sensitive to high temperature sensitization and Cl⁻ environment. By optimizing the heat treatment process, controlling the sulfur content and surface modification, its reliability under complex working conditions can be further improved.
