17-4 PH Stainless vs 316 Stainless
17-4 PH and 316 are both stainless, but they serve opposite priorities. 17-4 PH is a precipitation-hardening martensitic grade that heat-treats to very high strength, while 316 is a soft austenitic grade built for maximum corrosion resistance. Engineers weigh them when a part must be both strong and corrosion-resistant — and must decide which property to favor.
The verdict
Choose 17-4 PH when you need high strength and hardness in a corrosion-resistant part — it heat-treats to ~1000 MPa yield and 38 HRC, vastly stronger than 316. Choose 316 when corrosion resistance is paramount, especially in chloride/marine/chemical service, or when you need high ductility and good weldability — 316 carries 2-3% molybdenum and a higher corrosion rating but only ~240 MPa yield.
Side-by-side data
| Property | 17-4 PH Stainless | 316 Stainless |
|---|---|---|
| Category | Stainless Steel | Stainless Steel |
| Density (g/cm³) | 7.8 | 8.0 |
| Tensile strength (MPa) | 1070 | 515 |
| Yield strength (MPa) | 1000 | 240 |
| Elongation (%) | 10 | 40 |
| Hardness | 38 HRC | 217 HB |
| Max service temp (°C) | 300 | 870 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 18 | 16 |
| Typically used for | High-strength corrosion-resistant parts | Marine, medical & chemical environments |
Which should you choose?
Choose 17-4 PH Stainless when…
- The part is a highly-stressed shaft, fastener, valve or pump component needing ~1000 MPa yield
- You need stainless corrosion resistance combined with high hardness (38 HRC)
- A single low-temperature aging step must set final properties with minimal distortion
- Wear resistance and fatigue strength matter more than chloride immunity
- Service stays moderate in temperature (rated to ~300°C)
- You can accept tougher machining (best done in solution-annealed condition)
Choose 316 Stainless when…
- Corrosion resistance is the priority — marine, medical, food or chemical exposure
- The part is formed, deep-drawn or extensively welded (40% elongation, easy welding)
- Chloride/pitting resistance matters — 316's 2-3% Mo gives the top corrosion rating
- Moderate strength is sufficient (240 MPa yield) and section size carries the load
- Non-magnetic behavior is needed (316 is austenitic; 17-4 is magnetic martensitic)
- High service temperature up to ~870°C is required
Key differences that matter
- 17-4 PH is precipitation-hardening martensitic; 316 is austenitic — different families with opposite strengths
- 17-4 PH is dramatically stronger: ~1000 MPa yield / 1070 MPa tensile and 38 HRC, vs 316's 240 MPa yield
- 316 has higher corrosion resistance, especially against chlorides, thanks to 2-3% molybdenum
- 316 is far more ductile (40% vs 10% elongation) and welds more easily
- 17-4 is magnetic; 316 is essentially non-magnetic
- 17-4 hardens via a simple low-temperature aging treatment with little distortion
- 316 tolerates much higher service temperature (~870°C vs ~300°C for 17-4 PH)
Need 17-4 PH Stainless or 316 Stainless parts made?
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Open the Material SelectorGet a Quote →Frequently asked questions
Is 17-4 PH stronger than 316?
Yes, by a large margin. After aging, 17-4 PH reaches roughly 1000 MPa yield and 1070 MPa tensile at 38 HRC, while 316 sits near 240 MPa yield and 515 MPa tensile. 17-4 is chosen specifically for high-strength, high-hardness parts; 316 is not a structural-strength grade.
Which is more corrosion resistant?
316. Its austenitic structure plus 2-3% molybdenum gives it the higher corrosion rating, particularly against chlorides and pitting in marine and chemical service. 17-4 PH is corrosion-resistant for a high-strength grade but its martensitic structure and lower alloying make it less resistant than 316, especially in salt environments.
Can 17-4 PH be hardened and 316 cannot?
Correct. 17-4 PH is precipitation-hardening: a low-temperature aging step (such as H900) precipitates copper-rich phases to reach high strength with minimal distortion. 316 is austenitic and cannot be hardened by heat treatment — it only strengthens through cold work, which still leaves it far softer than aged 17-4.
Is 316 easier to weld and form than 17-4 PH?
Yes. 316's 40% elongation and austenitic structure make it excellent for deep forming and routine welding. 17-4 PH has only ~10% elongation and is martensitic, so it forms poorly and welding requires care plus post-weld heat treatment to restore properties. For fabricated, formed parts 316 is the practical choice.
Is 17-4 PH magnetic?
Yes. 17-4 PH is martensitic and therefore ferromagnetic, so it responds to a magnet. 316 is austenitic and essentially non-magnetic. If a non-magnetic stainless is required — for instrumentation or certain medical uses — 316 fits, whereas 17-4 PH would not.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.