Steel Nitralloy 135
Nitralloy 135 (34CrAlMo5-10) is the classic US aluminium-chromium-molybdenum nitriding steel of the SAE J412 type, developed for the Nitralloy gas-nitriding process and giving one of the highest attainable case hardnesses.
Reference datasheet — Nitralloy 135 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the QT28-32 condition
Nitralloy 135 tempers and conditions
Nitralloy 135 is supplied in 9 conditions, soft to hard. QT28-32 is the default FabDigit quotes; the values on this page are for it.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Choose for deep machining, cold sawing or subsequent full heat treatment by the user. | 500 | 760 | 22 | 220 HB | — |
Hot rolled | Mill delivery condition for oversize stock that the user will anneal or Q&T themselves. | 580 | 900 | 16 | 27 HRC | 7.8 % IACS |
Normalized | Homogenised structure for forgings before final quench and temper; not a service condition for nitriding. | 620 | 930 | 18 | 28 HRC | 7.8 % IACS |
Cold drawn | Small-diameter bar with good size tolerance and straightness for screw-machine work prior to heat treatment. | 650 | 830 | 12 | 22 HRC | 7.8 % IACS |
Q&T to 24–28 HRC | Pick when core toughness and easier finish machining outrank core strength (large shafts, thick sections). | 690 | 860 | 19 | 26 HRC | — |
Q&T plus stress relief after rough machining | Specify for precision parts (spindles, extruder screws) to minimise distortion during the long nitriding cycle. | 800 | 950 | 17 | 30 HRC | 7.8 % IACS |
QT28-32Default Q&T to 28–32 HRC | The stocked default: quenched and tempered above the nitriding temperature so the core is dimensionally stable during gas nitriding. | 815 | 965 | 17 | 31 HRC | — |
Q&T + gas nitrided | The functional end condition: extremely hard, wear- and scuff-resistant surface with high fatigue strength on a tough Q&T core. | 815 | 965 | 14 | 67 HRC | — |
Q&T to 32–36 HRC | Use when the nitrided case must be supported by a strong core (small gears, high-load screws, thin sections). | 950 | 1,100 | 15 | 34 HRC | — |
What is Nitralloy 135?
Nitralloy 135 (34CrAlMo5-10) is the classic US aluminium-chromium-molybdenum nitriding steel of the SAE J412 type, developed for the Nitralloy gas-nitriding process and giving one of the highest attainable case hardnesses. Engineers specify it for precision hardened surfaces on quenched and tempered bar and forgings, with typical values of 815 MPa yield, 965 MPa tensile, 17 % elongation and 302 HB (31 HRC) and service to 500 °C. Machinability is low (score 35), the grade is effectively non-weldable, and the core steel has no corrosion resistance of its own. Nitralloy N is the alternative where core toughness matters more than peak case hardness. Nitralloy 135 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,425°C (2,597 °F). Nitralloy 135 has a yield strength of 815 MPa (118 ksi) and a tensile strength of 965 MPa (140 ksi) — stronger than 87% of steel grades. Elongation at break is 17% and the elastic modulus is 210 GPa (30.5 Msi).
What is Nitralloy 135 used for?
- aircraft gears
- precision shafts
- cam followers
- gauge components
Advantages
- High service temperature — 500°C (932 °F), better than 90% of steel grades
- High strength — 815 MPa (118 ksi), better than 87% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Difficult to weld — 15/100, worse than 91% of steel grades
- Limited formability — 15/100, worse than 87% of steel grades
- Difficult to machine — 35/100, worse than 84% of steel grades
- Poor heat conductor — 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades
Nitralloy 135 properties
Typical room-temperature values for Nitralloy 135-QT28-32; bars are the position among steel grades.
Physical3
Nitralloy 135 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
Nitralloy 135 has a yield strength of 815 MPa (118 ksi) and a tensile strength of 965 MPa (140 ksi) — stronger than 87% of steel grades. Elongation at break is 17% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
Nitralloy 135 is rated for continuous service to 500°C (932 °F). It conducts heat at 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
Nitralloy 135 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of Nitralloy 135 takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability8
Nitralloy 135's machinability is fair (35/100, worse than 84% of steel grades); weldability poor (15/100); formability poor (15/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. Nitralloy 135 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Nitralloy 135
Is Nitralloy 135 easy to machine?
Rough and finish machine in the Q&T (28–32 HRC) condition with carbide tooling and rigid setups; leave 0.03–0.08 mm for post-nitride grinding since the nitrided case can only be ground or lapped.
Can Nitralloy 135 be welded?
Effectively non-weldable in service parts — the ~1 % Al plus Cr-Mo content promotes cracking and destroys the nitriding response; if unavoidable, use high preheat, matching Cr-Mo filler and full re-heat-treatment.
Can Nitralloy 135 be formed, bent or molded?
Hot forge at 1050–1150 °C with slow cooling and immediate anneal; cold forming is impractical in any hardened condition.
Nitralloy 135 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CNitralloy 135 Modified is narrower, 0.38–0.43 | 0.35 – 0.45 | 0.4 |
| Mn | 0.4 – 0.7 | 0.55 |
| Si | 0.2 – 0.4 | 0.3 |
| Cr | 1.4 – 1.8 | 1.6 |
| AlNitride former responsible for the very high case hardness | 0.85 – 1.3 | 1.05 |
| MoNitralloy 135 Modified (135M) raises Mo to 0.30–0.45 | 0.15 – 0.25 | 0.2 |
| Niresidual | ≤ 0.3 | |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on Nitralloy 135?
Nitride at 500–530 °C after stress relief; strip the brittle white layer by lapping/polishing where fatigue matters, then oil, black-oxide or phosphate for rust protection (the steel itself has no corrosion resistance).
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel Nitralloy 135 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 34CrAlMo5-10
How much does Nitralloy 135 cost?
Nitralloy 135 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Nitralloy 135 — frequently asked
What is Nitralloy 135 used for?
Nitralloy 135 is typically used for aircraft gears, precision shafts, cam followers and gauge components. In short: classic US Nitralloy grade; maximum gas-nitrided case hardness; aerospace precision nitriding steel.
What is the yield strength of Nitralloy 135?
Nitralloy 135 has a typical yield strength of 815 MPa (118 ksi) and a tensile strength of 965 MPa (140 ksi) — stronger than 87% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is Nitralloy 135 easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% of steel grades). Rough and finish machine in the Q&T (28–32 HRC) condition with carbide tooling and rigid setups; leave 0.03–0.08 mm for post-nitride grinding since the nitrided case can only be ground or lapped.
Can Nitralloy 135 be welded?
Not readily — weldability is rated poor (15/100). Effectively non-weldable in service parts — the ~1 % Al plus Cr-Mo content promotes cracking and destroys the nitriding response; if unavoidable, use high preheat, matching Cr-Mo filler and full re-heat-treatment.
What surface finishes work on Nitralloy 135?
Nitride at 500–530 °C after stress relief; strip the brittle white layer by lapping/polishing where fatigue matters, then oil, black-oxide or phosphate for rust protection (the steel itself has no corrosion resistance).
Can Nitralloy 135 be formed, bent or molded?
Hot forge at 1050–1150 °C with slow cooling and immediate anneal; cold forming is impractical in any hardened condition.
What is the maximum service temperature of Nitralloy 135?
Nitralloy 135 is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Nitralloy 135 QT28-32 and Nitralloy 135-A?
QT28-32 is the default condition — the stocked default: quenched and tempered above the nitriding temperature so the core is dimensionally stable during gas nitriding. A: choose for deep machining, cold sawing or subsequent full heat treatment by the user. Yield strength is 815 MPa in QT28-32 versus 500 MPa in A.
How much does Nitralloy 135 cost?
Nitralloy 135 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- SAE J412 / SAE J404 — Nitriding steels (Nitralloy types) — SAE International (2018)
- EN 10085 — Nitriding steels (34CrAlMo5-10, 1.8507) — CEN (2001)
- GB/T 3077 (38CrMoAl) — SAC (2015)
- ASM Handbook Vol.4 — Heat Treating (Nitriding) — ASM International (1991)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- Nitriding steel bar datasheets (Böhler/voestalpine, Ovako, Baosteel 38CrMoAl) — various producers (2023)
- Mysteel / 1688 38CrMoAl (2026)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.