Nitralloy 135® Bar, Nitriding Steel AMS 6470, 6472, 2301
Nitralloy135® Bar B5EIA is a Chrome-Moly alloy steel with additions of aluminum typically used for nitrided parts requiring high surface hardness and heat resistance. Parts fabricated from Nitralloy 135® bar typically show less distortion in heat treating than similar parts fabricated from alloys requiring quenching and tempering to achieve similar surface hardness. This alloy may be heat treated in dissociated ammonia gas.
- Inventory & Specs
- Chemical Composition
- Physical Properties
- Mechanical Properties
- Datasheet
- Additional Info
- FAQs
Inventory Size Ranges for Nitralloy 135®
| Type | Thickness | AMS Standards | ASTM | Get a Quote |
|---|---|---|---|---|
| Bar | 2.000" - 7.000" | AMS 6470, AMS 6472, AMS 2301 | ASTM A 370, ASTM A 29, ASTM A 355 | Get a Quote |
Characteristics of Nitralloy135®
Nitralloy135® is specifically formulated to develop an extremely hard, wear‑resistant nitride case while maintaining a tough, ductile core. Its aluminum content is critical, forming strong nitrides that produce a dense, hardened surface during gas, salt-bath, or plasma nitriding. This alloy achieves very high case hardness (60+ HRC) without requiring quench‑and‑temper processes, reducing distortion and improving dimensional stability. Nitralloy135® has excellent wear resistance and fatigue strength due to its combination of aluminum, chromium, and molybdenum. This makes Nitralloy135® ideal for gears, shafts, cams, and aerospace drive components. While the outer case of this alloy becomes extremely hard, the core retains high tensile strength, good toughness and ductility, and stability under cyclic loads.
Working with Nitralloy135®
Nitralloy135® machines similarly to medium‑carbon alloy steels in its annealed or normalized condition, but its aluminum content slightly increases tool wear. It is recommended to machine before nitriding to avoid cutting the extremely hard nitride case. While welding is possible for this alloy, it must be approached with caution. The alloy's aluminum content and moderate hardenability increase the risk of cracking if welding heat is not controlled. Preheat and post‑heat processes may be required depending on part geometry. The key heat treatment streps for this alloy include forging, annealing, hardening, tempering, and nitriding.
Other industry standards we comply with:
- GE B5E1A S-22
- EN 10204
- Siemens Westinghouse PD-Spec 10305 HD SWPC AB
Common Trade Names
- Nitralloy®
- Nitrided steel®
Industry Applications for Nitralloy 135®
- Crankshafts
- Bolts
- Aircraft gears
- Pinions
Chemical Composition
| Element | Min | Max | |
|---|---|---|---|
| C | Carbon | 0.38 | 0.43 |
| Mo | Molybdenum | 0.30 | 0.40 |
| Mn | Manganese | 0.50 | 0.80 |
| Al | Aluminum | 0.95 | 1.30 |
| Si | Silicon | 0.20 | 0.40 |
| Ni | Nickel | - | 0.25 |
| Cr | Chromium | 1.40 | 1.80 |
| Cu | Copper | - | 0.35 |
| S | Sulfur | - | 0.025 |
| P | Phosphorous | - | 0.025 |
Physical Properties
| Property | Value |
|---|---|
| Density | 0.297 lb/in3 (8.22 g/cm3) |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | 112 ksi min |
| Yield Strength | at 0.2% offset 90 ksi min |
| Elong in 4D | 16% min |
| Reduction of Area | 50% min |
| Bars | typically provided in the quenched and tempered condition |
| Hardness | Up to 3.125" dia inclusive BHN 241/285 |
| Over 3.125" to 6.000" inclusive BHN 229/285 |
Datasheet
Additional Info
A Brief History of Nitralloy 135®
Nitralloy 135® originated as part of the early development of nitriding steels, created to meet industrial needs for materials with very hard, wear‑resistant surfaces and dimensionally stable cores. It was engineered as a chrome‑moly steel enhanced with aluminum additions, which promote nitride formation and enable a hardened case without quenching distortion. The alloy's modern form was refined through vacuum remelting technologies such as VAC‑ARC and VIM‑VAR, producing higher microcleanliness and improved fatigue resistance for aerospace‑grade performance.
How Nitralloy 135® was Developed
Nitralloy 135® was developed to create a nitriding steel with high case hardness, minimal distortion, and a strong, tough core, addressing shortcomings in traditional quench‑and‑temper alloy steels. Its chrome-moly base composition allowed for high strength and hardenability. The addition of aluminum significantly increases its nitride formation, enabling a dense hardened case during nitriding. The adoption of VAC-ARC and VIM-VAR remelting helped to ensure fine grain structure and predictable nitriding responses.
Early Applications of Nitralloy 135®
From its earliest commercial use, Nitralloy 135® was chosen for components demanding high surface hardness, fatigue strength, and tight dimensional tolerances, especially where quench‑related distortion would have been unacceptable. Common early applications included aircraft gears, drive components, crankshafts, camshafts, bolts, and precision fasteners.
How Nitralloy 135® is Used Today
Today, Nitralloy 135® remains a premier nitriding steel due to its combination of wear resistance, fatigue strength, core toughness, and dimensional stability. Modern applications include:
- Aerospace: Gears, pinions, shafts, bolts
- Industrial: Gears, crankshafts
Your Trusted Supplier of Nitralloy 135®
United Performance Metals offers Nitralloy 135® bar sizes 2.000" - 7.000". This product meets AMS 6470, AMS 6472, AMS 2301, ASTM A 370, ASTM A 29, and ASTM A 355 specifications.
Product FAQs
Aluminum (≈1.0–1.4%) is a powerful nitride former. It enables the formation of a dense and extremely hard nitrided case, improving wear resistance, fatigue life, and stability during nitriding.
After nitriding, Nitralloy 135® can achieve surface hardness above 60 HRC, making it suitable for heavy wear applications and long‑life components.
Nitralloy 135® achieves hardness trough nitriding, eliminating the distortion associated with quenching. This alloy provides a harder, deeper nitride case compared to other quench-and-tempered steels sue to its aluminum content. Additionally, Nitralloy 135® maintains a strong, ductile core while resisting wear and fatigue.