XM-13 is a molybdenum- and aluminium-bearing martensitic precipitation-hardening (PH) stainless steel. This datasheet presents the material within the American (ASTM / ASME / AMS / UNS) standard system.
With about 13% chromium, 8% nickel, 2.2% molybdenum and 1% aluminium and very low carbon, manganese, silicon, phosphorus and sulphur, 13-8Mo offers the highest toughness and best stress-corrosion-cracking resistance of the common PH stainless steels, combined with very high strength and good transverse properties. It is typically double-vacuum-melted (VIM + VAR) for high cleanliness. The molybdenum addition improves pitting resistance relative to 15-5PH and 17-4PH. The alloy is martensitic in the solution-treated condition and is strengthened by a single low-temperature ageing treatment that precipitates a nickel-aluminium phase.
Typical applications include aerospace structural and landing-gear components, valve and pump parts, shafts, fasteners, and high-strength corrosion-resistant components requiring maximum toughness.
Typical values, H1000 condition.
| Property | Value | Unit |
|---|---|---|
| Density | 7.76 | g/cm³ |
| Melting range | 1400–1440 | °C |
| Elastic modulus | 203 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 10.6 | µm/m·°C |
| Thermal conductivity (20 °C) | 14.0 | W/m·K |
| Specific heat (20 °C) | 460 | J/kg·K |
| Structure | Martensitic (precipitation-hardening) | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Iron | Fe | Balance | — | Base element |
| Chromium | Cr | 12.25 | 13.25 | Corrosion resistance; martensite former |
| Nickel | Ni | 7.5 | 8.5 | Toughness; martensite stability |
| Molybdenum | Mo | 2.0 | 2.5 | Pitting resistance; strength |
| Aluminium | Al | 0.90 | 1.35 | Precipitation-hardening phase (Ni-Al) |
| Manganese | Mn | — | 0.20 | Low (toughness) |
| Silicon | Si | — | 0.10 | Low (toughness) |
| Carbon | C | — | 0.05 | Low (toughness) |
| Phosphorus | P | — | 0.010 | Very low (toughness) |
| Sulphur | S | — | 0.008 | Very low (toughness) |
Typical values by ageing (H) condition, per ASTM A564 / AMS 5629 for UNS S13800.
| Condition | Tensile strength | 0.2% Yield | Hardness |
|---|---|---|---|
| H950 | ≥1520 MPa (220 ksi) | ≥1410 MPa (205 ksi) | ~47 HRC |
| H1000 | ≥1410 MPa (205 ksi) | ≥1310 MPa (190 ksi) | ~45 HRC |
| H1050 | ≥1340 MPa (195 ksi) | ≥1210 MPa (175 ksi) | ~43 HRC |
| H1100 | ≥1170 MPa (170 ksi) | ≥1070 MPa (155 ksi) | ~38 HRC |
Confirm against the mill test report. Elongation typically ≥10–14% depending on condition.
| Environment | Performance | Notes |
|---|---|---|
| Atmospheric / general | Good | Comparable to or better than 15-5PH |
| Chloride pitting | Moderate | Improved by molybdenum vs other PH grades |
| Stress-corrosion cracking | Very Good | Best SCC resistance of common PH grades |
| Mild acids | Good | At low concentrations |
| Seawater | Limited | Not recommended for prolonged exposure |
The molybdenum addition gives better pitting resistance than 15-5PH and 17-4PH; the high purity gives excellent toughness and SCC resistance.
A martensitic precipitation-hardening alloy; supplied in Condition A (solution-treated) and hardened by a single low-temperature ageing treatment.
Solution Treatment (Condition A) Approximately 925 °C followed by cooling to room temperature to form a martensitic structure.
Precipitation Hardening (Ageing) A single low-temperature ageing treatment precipitates a nickel-aluminium phase. The temperature sets the strength level: H950 (~510 °C) gives maximum strength; higher temperatures (H1000, H1050, H1100) progressively lower strength while increasing toughness. Air cool after ageing.
Weldable by common fusion methods; matching filler is used. A post-weld solution treatment and ageing restores full properties.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | Matching 13-8-type filler |
| GMAW / MIG | Good | Matching filler |
| EBW / laser | Good | Autogenous or matching filler |
Weld in the solution-treated condition; re-age after welding to restore strength.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Preferred condition | Condition A or over-aged for best machinability |
| Tooling | Carbide tooling; rigid setup |
| Coolant | Ample flood coolant |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | Limited in hardened conditions; form in Condition A |
| Hot forming | ~1150–950 °C; solution treat + age afterward |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Aerospace | Landing gear, structural fittings, actuators | Maximum toughness + high strength |
| Defence | High-strength structural components | Strength + SCC resistance |
| Oil & gas | Valve and pump components, shafts | Strength + pitting resistance |
| General industrial | High-strength fasteners, gears | Hardness + toughness |
| Product Form | ASTM Standard | ASME / AMS |
|---|---|---|
| Bar, wire, forgings and extrusions | ASTM A564 grade XM-13 | ASME SA-564 / AMS 5629 |
| Plate, sheet and strip | ASTM A693 grade XM-13 | AMS 5864 |
| Forgings | ASTM A705 grade XM-13 | ASME SA-705 |
| Welding consumables | Matching 13-8-type filler | — |
Molybdenum- and aluminium-bearing martensitic precipitation-hardening stainless steel. UNS S13800.
| XM Grade | Type | Cr % | Ni % | Best Used For |
|---|---|---|---|---|
| XM-13 | Martensitic PH (Mo-Al) | 12.25–13.25 | 7.5–8.5 | Highest-toughness PH; aerospace, SCC resistance |
| XM-12 | Martensitic PH (Cu) | 14–15.5 | 3.5–5.5 | High-strength PH (15-5PH type) |
| XM-16 | Martensitic PH | 11.5–13.5 | 4.5–5.5 | High-strength PH (Custom 455, different type) |
| XM-25 | Martensitic PH | 11.5–13 | 8–9 | High-strength PH (different type) |
| XM-27 | Ferritic | 25–27.5 | — | Corrosion-resistant ferritic (different type) |




