1 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 15.5–17.5 · Ni 3.0–5.0 · Cu 3.0–5.0 · Nb+Ta 0.15–0.45
UNS S17400 AMS 5643
Precipitation-hardening stainless
2 The conditions — the H-number is the aging temperature in °F
| Condition | Aging temp | UTS (ksi) | Hardness (HRC) | 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 |
3
Key
properties
properties
UTS
190 ksi
0.2% YS
170 ksi
HARDNESS
HRC 40-44 (H900)
DENSITY
0.280 lb/in³
MACHINABILITY
45 / 100
SPEC
AMS 5643
4
Typical
uses
uses
Aerospace landing gear hardwareHydraulic valve bodiesPump shaftsDefense ordnanceMarine
5 Machinist's note — order of operations
- ✓ Machine in Condition A (solution annealed, ~33 HRC): rough & semi-finish, then heat-treat to the H-condition the drawing calls out.
- ✓ H900 aging CONTRACTS ~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.
Drawing says H900? Machine it in Condition A, age at 900 °F, then passivate. Full datasheet: trueprecisionmachining.com/engineering/datasheets/stainless-17-4ph