Engineering snapshot · Nº 03
What Is 17-4PH?
The aerospace workhorse stainless: alloy-steel strength with stainless-class corrosion resistance.
Digital MachineQuick-Turn CNC1
What it is
A precipitation-hardening martensitic stainless (UNS S17400): chromium–nickel–copper chemistry that gains its strength from a low-temperature copper-precipitate aging cycle, not from quench hardening.
The payoff: alloy-steel strength with stainless-class corrosion resistance. One bar stock, four service conditions.
Fe Bal. · Cr 15.0–17.5 · Ni 3.0–5.0 · Cu 3.0–5.0 · Nb+Ta 0.15–0.45
UNS S17400AMS 5643Precipitation-hardening stainless
Hardness vs aging temperature
Higher aging temperature: lower hardness, more toughness.
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The conditions: the H-number is the aging temperature in °F
| Condition | Aging temp | UTS min (ksi) | HRC (typ.) | Character |
|---|---|---|---|---|
| Cond. A | Solution annealed, no age | — | ~33 | Machine it here |
| H900 | 900 °F / 482 °C | 190 | 44 | Peak strength |
| H1025 | 1025 °F / 552 °C | 155 | 38 | Best balance |
| H1075 | 1075 °F / 580 °C | 145 | 36 | Marine + chloride |
| H1150 | 1150 °F / 621 °C | 135 | 33 | Toughest |
- Cond. AMachine it hereSolution annealed, no age · ~33 HRC
- H900Peak strength900 °F / 482 °C · UTS min 190 ksi · 44 HRC
- H1025Best balance1025 °F / 552 °C · UTS min 155 ksi · 38 HRC
- H1075Marine + chloride1075 °F / 580 °C · UTS min 145 ksi · 36 HRC
- H1150Toughest1150 °F / 621 °C · UTS min 135 ksi · 33 HRC
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Key properties
UTS (H900 min)
190 ksi
0.2% YS (H900 min)
170 ksi
Hardness
HRC 40-44 (H900)
Density
0.280 lb/in³
Machinability
45 / 100
Spec
AMS 5643
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Typical uses
- Aerospace landing gear hardware
- Hydraulic valve bodies
- Pump shafts
- Defense ordnance
- Marine
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Machinist's note: order of operations
- Machine in Condition A (solution annealed, ~33 HRC): rough and semi-finish, then heat-treat to the H-condition the drawing calls out.
- H900 aging contracts about 0.04–0.06%: a predictable shrinkage, not growth.
- Thin sections: leave 0.005–0.010″ finish stock for post-aging cleanup. Thicker work usually fits inside standard tolerance as aged.
- In our shop: we machine it; aging and passivation go through vetted partners, and hardness is verified in house afterward.
Drawing says H900? Machine it in Condition A, age at 900 °F, then passivate. Full datasheet: digitalmachine.com/engineering/datasheets/stainless-17-4ph