Maraging 250 Steel
18Ni maraging steel, tougher than 300
Typical values for the temper in the title
Maraging 250 is a grade in the 18Ni maraging family: very low carbon, about 18% nickel, cobalt and molybdenum. The number gives the nominal strength (250 ksi, about 1725 MPa).
Compared with Maraging 300 it has less cobalt and titanium, so strength is lower, but toughness and ductility are higher (about 11% elongation). It is used for aerospace and missile parts, loaded mechanism parts and die-casting dies.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | ≈1750 MPa (aged) | |
| Yield strength Rp0.2 | ≈1710 MPa (aged) | |
| Elongation A | ≈11% | |
| Modulus of elasticity E | 186 GPa | |
| Density ρ | 8.0 g/cm³ | |
| Hardness | ≈50 HRC (aged) | |
| Machinability | 70% (annealed, before aging) | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Ni nickel | 17.0–19.0 | martensitic matrix |
| Co cobalt | 7.0–8.5 | age strengthening |
| Mo molybdenum | 4.6–5.2 | strengthening precipitates |
| Ti titanium | 0.3–0.5 | strengthening precipitates |
| C carbon | max 0.03 | very low |
| Fe iron | balance |
Ranges per MIL-S-46850D. Properties per the SSA data sheet.
Conditions and heat treatment
Maraging steels are supplied annealed (relatively soft, about HRC 30–35), machined in that condition, and gain strength by a simple low-temperature aging, with very small dimensional change.
| Condition | Properties | When to choose it |
|---|---|---|
| Annealed | about HRC 30–35, easy to machine | machining |
| Aged (about 480 °C) | about 1750 MPa, about 50 HRC | the finished part |
Applications
- Aerospace and missile parts
- Loaded mechanism parts
- Die-casting dies
- High-strength shafts and springs
- Tooling
Fabrication
Aging
At about 480 °C for several hours, without quenching. The dimensional change is small and predictable, so finish machining can be done before aging.
Welding
Welds well for a steel of this strength (very low carbon). Age after welding.
Corrosion
Not stainless. Protect with a coating.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| Maraging 300 | 2050 / 2000 MPa | Excellent | Maraging 300: stronger, less tough · material page |
| Maraging 350 | ≈2360 MPa (aged) / ≈2320 MPa (aged) | Good — age after welding | Maraging 350: the strongest · material page |
| AerMet 100 | 1965 / 1725 MPa | Good — ER250 filler | AerMet 100: high strength and high toughness · material page |
Common mistakes
Choosing 300 when toughness is required
250 is tougher.
Quench hardening it like an ordinary steel
Maraging steel is strengthened by aging, not by quenching.
Leaving it unprotected
It rusts.
Equivalents, standards and supply
| DIN | 1.6354 (X2NiCoMo18-9-5) |
|---|---|
| Standards | AMS 6512 / MIL-S-46850 |
| Forms | bar · plate · forging |
| Producers | ATI (VascoMax) · Carpenter |
Learn more
Values are typical and for comparison only, and depend strongly on condition and diameter. For design, rely on the standard and on the mill certificate. Sources: SAE J403 and J404, ASTM A29, A322 and A519 (composition), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026