Steel M50NiL-HT (Hardened & Tempered)
Heat-treated state
Use for through-hardened shafts, cages or test coupons where case hardness is not required but high core toughness is.
Values for the 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-HTDefault 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 | — |
HTThis page 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-HT?
M50NiL-HT is M50NiL heat treated to HT — use for through-hardened shafts, cages or test coupons where case hardness is not required but high core toughness is. M50NiL-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 13% and the elastic modulus is 203 GPa (29.4 Msi). M50NiL-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). CARB-HT is the default condition FabDigit quotes; HT is available on request or by drawing note.
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 — 15/100, worse than 98% 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-HT properties
Typical room-temperature values for M50NiL-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-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-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 13% and the elastic modulus is 203 GPa (29.4 Msi).
Thermal6
M50NiL-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-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-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-HT's machinability is poor (15/100, worse than 98% of steel grades); weldability not recommended (12/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M50NiL-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-HT — frequently asked
What is M50NiL-HT used for?
M50NiL-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-HT?
M50NiL-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-HT easy to machine?
Not especially — machinability is rated poor (15/100, worse than 98% 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-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-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-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-HT?
M50NiL-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.