CBS-50 NiL AMS 6278

CBS-50 NiL is a carburizing bearing and gear steel designed for service temperatures up to 600°F. It has high core fracture toughness properties compared to other bearing alloys. Because the CBS-50 NiL can be carburized, surface stresses are controlled to provide excellent rolling contact fatigue characteristics.

Common stock sizes: 4.500” to 8.000” diameters

Common Specifications:

  • AMS 6278
  • B50TF347
  • General Electric S-400 / S-SPEC-35
  • Pratt & Whitney LCS F-17

Industry Trade Names:

  • M50NIL
  • UNS K91231

Common Applications:

  • Aerospace bearings
  • Aerospace gears

Macrostructure Limits:

Class Condition Severity
1 Freckles A
2 White Spots A
3 Radial Segregation B
4 Ring Pattern B
Rockwell-Industries-CBS-50-NiL-ams-6278-image

Composition

Element Min. Max.
Carbon 0.11 0.15
Manganese 0.15 0.35
Silicon 0.10 0.25
Phosphorus -- 0.015
Sulfur -- 0.010
Chromium 4.00 4.25
Nickel 3.20 3.60
Molybdenum 4.00 4.50
Copper -- 0.10
Vanadium 1.13 1.33
Cobalt -- 0.25
Tungsten -- 0.15

VIM-VAR Melting Practice

Average grain size of ASTM No. 5 or finer

Maximum Total Depth of Decarburization, inch/pound units:

Nominal Diameter or Distance Between Parallel Sides Inches Total Depth of Decarburation Inch
Up to 0.500, incl 0.015
Over 0.500 to 1.000, incl 0.030
Over 1.000 to 2.000, incl 0.040
Over 2.000 to 3.000, incl 0.050
Over 3.000 to 4.000, incl 0.065
Over 4.000 to 5.000, incl 0.095