135 Mod
Request a quote for 135 ModNitralloy 135 Modified is the classic aluminum bearing nitriding steel. Aluminum in the chemistry forms very hard, very stable nitrides during gas nitriding, producing a surface in the 60 to 70 HRC range over a tough quenched and tempered core, with minimal distortion because nitriding runs below the tempering temperature.
That combination suits gears, shafts, cylinders and any part that must resist wear and surface fatigue while keeping dimensional accuracy achieved before the final thermal process.
We supply Nitralloy 135 Mod vacuum melted as bar and forging billet, in annealed or heat treated condition for machining ahead of nitriding.
Sizes and stock
- Round bar: through 8" DIA
- Custom shapes and forgings: per request
Processing capabilities
- Vacuum melted (VAR / VIM-VAR) stock with full melt traceability
- Normalize, anneal, quench and temper to the ordered condition
- Saw cutting, trepanning, gun drilling and rough machining
- Magnetic particle and ultrasonic inspection to AMS 2301 / AMS 2154 on request
Specifications
Material is released to the applicable specification with mill test reports and, on request, independent lab verification.
Why engineers specify 135 Mod
- Very high nitrided case hardness with an excellent wear surface
- Low distortion because nitriding occurs below the temper temperature
- Tough quenched and tempered core beneath the case
- Good fatigue strength for gear and shaft duty
Nominal chemistry
Percent by weight, nominal composition per the governing specification. The mill test report for your heat is the controlling document.
Typical mechanical properties
| Condition | Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|---|
| Q&T core | 135 ksi min | 110 ksi min | 15% min | 28-34 HRC |
| Nitrided case | - | - | - | 60-70 HRC surface |
Typical published values for reference only, not for design. Properties vary with section size, product form and processing. Order to the specification and condition your drawing requires.
Typical applications
- Gears, pinions and splines
- Cam and crank shafts
- Cylinder liners and hydraulic components
- High fatigue rotating hardware
Fabrication notes
Machining
Best machined in the annealed or normalized-and-tempered condition, then heat treated to final strength. Rough machining before hardening, with a finish pass after temper, controls distortion on long or thin sections. We can supply rough turned, trepanned or gun drilled stock so your first operation starts closer to net shape.
Welding
Weldable with low hydrogen practice, preheat appropriate to carbon equivalent and section size, and a post weld stress relief or full re-heat treat. For high strength conditions the weld and heat affected zone should be re-treated to restore properties.
Forming
Hot work in the annealed condition. Cold forming is limited at high hardness, so bend and form before hardening and follow with stress relief where the geometry is tight.
135 Mod compared with similar grades
4340
Through hardening rather than case hardening; no nitride forming aluminum.
4320 / 9310
Carburizing grades that build a case by carbon diffusion, generally with deeper cases and more distortion.
Designations and cross reference
- Material family
- Alloy Steels
Working from an obsolete, foreign or superseded designation? Send it over and we will cross reference it to a current grade and specification.
Quality, testing and traceability
Supplied aircraft quality with mill test reports, melt and heat traceability, and, on request, magnetic particle inspection to AMS 2301 or AMS 2300, ultrasonic inspection to AMS 2154, chemical assay, hardness and full mechanical testing.
We are AS9100D and ISO 9001:2015 registered. If our stock does not already carry the inspection your specification requires, we can quote the material with that work performed. More on our quality system
Available forms
Custom sizes converted from billet, plus saw cut, waterjet and near-net blanks. See custom conversions
135 Mod frequently asked questions
What is 135 Mod?
Nitralloy 135 Modified is the classic aluminum bearing nitriding steel. Aluminum in the chemistry forms very hard, very stable nitrides during gas nitriding, producing a surface in the 60 to 70 HRC range over a tough quenched and tempered core, with minimal distortion because nitriding runs below the tempering temperature.
What forms is 135 Mod available in?
We supply 135 Mod in bar, forging. Custom sizes are converted from billet, and we can provide saw cut, waterjet or near net blanks so material arrives closer to your finished part.
What specifications can 135 Mod be supplied to?
Commonly ordered specifications include AMS 6472, AMS 6470, AMS 6471. Material is released to the specification and condition on your purchase order, with mill test reports supplied as standard.
What conditions can 135 Mod be ordered in?
We can supply Q&T core, Nitrided case. If our stock is not already in the condition you need, we can quote it with the heat treatment performed before shipment.
Can you cut 135 Mod to size?
Yes. Saw cutting, waterjet, laser and shearing are available, along with trepanning, gun drilling, lathe turning and CNC machining, so you can order blanks or rough machined pieces rather than full lengths.
Do you provide test reports and additional testing on 135 Mod?
Every order ships with mill test reports and heat traceability. If your print calls for ultrasonic inspection, penetrant dye, magnetic particle, chemical assay, micrography, hardness or mechanical testing and our stock does not already carry it, we can quote the material with that work performed.
Can 135 Mod be supplied to DFARS domestic melt requirements?
Tell us at quote stage if the order is DFARS or domestic melt restricted and we will confirm availability against that requirement before you commit.
What do you need to quote 135 Mod?
Grade, form, dimensions, quantity, specification and condition, plus any testing or certification requirements and the date you need it. Send a drawing if you have one. Quotes are typically ready within 24 hours.
How does 135 Mod compare with 4340?
Through hardening rather than case hardening; no nitride forming aluminum.