Steel M50NiL CARB-HT
Heat-treated state · default condition
CARB-HT = carburized, Hardened & Tempered
Standard aerospace bearing condition: hard wear-resistant case with compressive residual stress over a tough, spall-arresting core.
Values for the CARB-HT condition
Other M50NiL tempers and conditions
M50NiL is listed in 4 conditions; see the grade overview at M50NiL.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Supply condition for machining bearing rings and rollers before carburizing. | 620 | 900 | 18 | 21 HRC | — |
CARB-HTDefaultThis page Carburized, Hardened & Tempered | Standard aerospace bearing condition: hard wear-resistant case with compressive residual stress over a tough, spall-arresting core. | 1,250 | 1,500 | 12 | 61 HRC | — |
Hardened & Tempered | Use for through-hardened shafts, cages or test coupons where case hardness is not required but high core toughness is. | 1,250 | 1,500 | 13 | 45 HRC | — |
carburize/harden/temper followed by plasma or gas nitriding | Choose when extra surface hardness and scuffing/skid resistance are needed for high-DN or marginally lubricated bearings. | 1,250 | 1,500 | 11 | 66 HRC | 2.9 % IACS |
What is M50NiL CARB-HT?
M50NiL CARB-HT is M50NiL heat treated to CARB-HT — standard aerospace bearing condition: hard wear-resistant case with compressive residual stress over a tough, spall-arresting core. M50NiL CARB-HT has a yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,500 MPa (218 ksi) — stronger than 95% of steel grades. Elongation at break is 12% and the elastic modulus is 203 GPa (29.4 Msi). M50NiL CARB-HT has a density of 7.89 g/cm³ (0.285 lb/in³), heavier than 93% of steel grades. It melts at 1,400°C (2,552 °F).
Advantages
- Polishes to a fine finish — 85/100, better than 99% of steel grades
- High strength — 1,250 MPa (181 ksi), better than 95% of steel grades
Limitations
- Difficult to machine — 8/100, worse than 100% of steel grades
- Difficult to weld — 12/100, worse than 96% of steel grades
- High embodied carbon — 3.8 kg CO₂/kg, worse than 94% of steel grades
- Poor heat conductor — 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 92% of steel grades
- Limited formability — 15/100, worse than 87% of steel grades
M50NiL CARB-HT properties
Typical room-temperature values for M50NiL CARB-HT; 13 are specific to this condition. Other listed values are M50NiL reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
M50NiL CARB-HT has a density of 7.89 g/cm³ (0.285 lb/in³), heavier than 93% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
M50NiL CARB-HT has a yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,500 MPa (218 ksi) — stronger than 95% of steel grades. Elongation at break is 12% and the elastic modulus is 203 GPa (29.4 Msi).
Thermal6
M50NiL CARB-HT is rated for continuous service to 315°C (599 °F). It conducts heat at 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 92% of steel grades. Thermal expansion is 11.4 µm/m·K (6.33 µin/in·°F).
Electrical2
M50NiL CARB-HT has an electrical resistivity of 6×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is poor (18/100), better than 83% of steel grades.
Sustainability4
Producing a kilogram of M50NiL CARB-HT takes about 55 MJ of energy and emits 3.8 kg of CO₂ — more than 94% of steel grades. Typical recycled content is 15%.
Manufacturability6
M50NiL CARB-HT's machinability is not recommended (8/100, worse than 100% of steel grades); weldability not recommended (12/100); formability poor (15/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M50NiL CARB-HT
Is M50NiL easy to machine?
Machine all features in the spheroidize-annealed condition with rigid setups and coated carbide at modest speeds; after carburizing and hardening only grinding, honing and superfinishing (or EDM) are practical.
Can M50NiL be welded?
Not weldable in practice — high hardenability and secondary-hardening alloy content give brittle untempered martensite; joints are avoided in bearing components.
Can M50NiL be formed, bent or molded?
Hot forged/ring-rolled from VIM-VAR ingot at roughly 1050–1150 °C with slow cooling and immediate anneal; no cold forming after hardening.
What surface finishes work on M50NiL?
Vacuum carburize, harden, deep freeze and triple temper, then grind and superfinish raceways; protect with oil, phosphate or thin black-oxide/DLC since the 4% Cr gives no stainless behaviour.
M50NiL 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 |
|---|---|---|
| Clow carbon for case carburizing | 0.11 – 0.15 | 0.13 |
| Mn | 0.15 – 0.35 | 0.25 |
| Si | 0.1 – 0.25 | 0.2 |
| Cr | 4 – 4.25 | 4.1 |
| Nicore toughness / hardenability | 3.2 – 3.6 | 3.4 |
| Mosecondary hardening | 4 – 4.5 | 4.25 |
| Vcarbide former, grain refinement | 1.13 – 1.33 | 1.2 |
| P | ≤ 0.02 | — |
| S | ≤ 0.01 | — |
| Cu | ≤ 0.1 | — |
| Co | ≤ 0.25 | — |
| Fe | balance | — |
M50NiL CARB-HT — frequently asked
What is M50NiL CARB-HT used for?
M50NiL CARB-HT is typically used for aircraft engine mainshaft bearings, high-load rolling element bearings, helicopter transmission bearings, gas turbine accessory gearbox bearings, carburized bearing rings and rollers and high-speed spindle bearing races. In short: carburizing aerospace bearing steel; tough core, 61 HRC case; very difficult to machine.
What is the yield strength of M50NiL CARB-HT?
M50NiL CARB-HT has a typical yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,500 MPa (218 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is M50NiL CARB-HT easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 100% of steel grades). Machine all features in the spheroidize-annealed condition with rigid setups and coated carbide at modest speeds; after carburizing and hardening only grinding, honing and superfinishing (or EDM) are practical.
Can M50NiL CARB-HT be welded?
Not readily — weldability is rated not recommended (12/100). Not weldable in practice — high hardenability and secondary-hardening alloy content give brittle untempered martensite; joints are avoided in bearing components.
What surface finishes work on M50NiL CARB-HT?
Vacuum carburize, harden, deep freeze and triple temper, then grind and superfinish raceways; protect with oil, phosphate or thin black-oxide/DLC since the 4% Cr gives no stainless behaviour.
Can M50NiL CARB-HT be formed, bent or molded?
Hot forged/ring-rolled from VIM-VAR ingot at roughly 1050–1150 °C with slow cooling and immediate anneal; no cold forming after hardening.
What is the maximum service temperature of M50NiL CARB-HT?
M50NiL CARB-HT is rated for continuous use to about 315°C (599 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between M50NiL CARB-HT and M50NiL-ANN?
CARB-HT is the default condition — standard aerospace bearing condition: hard wear-resistant case with compressive residual stress over a tough, spall-arresting core. ANN: supply condition for machining bearing rings and rollers before carburizing. Yield strength is 1,250 MPa in CARB-HT versus 620 MPa in ANN.
Sources
- AMS 6278 — Steel Bars, Forgings and Tubing, 4.1Cr-3.4Ni-4.2Mo-1.2V, Consumable Electrode Vacuum Melted — SAE International (2018)
- GB/T 3203 (G13Cr4Mo4Ni4V) — SAC (2016)
- ASM Handbook Vol.18 — Friction, Lubrication and Wear Technology (rolling-element bearing steels) — ASM International (2017)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- M50NiL VIM-VAR bearing steel datasheet — Latrobe Specialty Metals / Carpenter Technology (2020)
- NASA Technical Memoranda on M50 and M50NiL bearing fatigue and fracture toughness — NASA Glenn Research Center (1995)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.