November 16, 2018


Increasing numbers of industrial components are being subjected to high surface stresses and dynamic loads, requiring the use of special high-performance steels. Where high surface hardness and excellent fatigue strength are required and when the material is also subjected to high temperatures, nitriding technology offers the best case hardening option.

FOR REQUIREMENTS:High Fatigue Nitriding Grade
Nitralloy N/135
UNS: K24340

In this field, GKHW offers the best combination of core properties to withstand structural loads & damage tolerances and surface functions in the case hardened layer. The result on components gives one of the best solutions in the market for contact pressures and fatigue performances.

GKHW can also be used without nitriding and offers the triple advantage of an excellent combination of mechanical properties, high thermal fatigue and high thermal conductivity.

Benefits of GKHW

The use of GKHW covers all the gears design considerations and brings the highest value of this technology:

  • Exceptional fatigue bending performance
  • Very deep case requirement (0.8mm achieved in 120Hrs nitriding)
  • Limited influence of ageing during nitriding on core properties
  • Exceptional compromise of core hardness and damage tolerance
  • Surface metallurgy with limited depth and favorable compound layer
  • Weldable material (EBW for instance) giving the opportunity to avoid mechanical assembly

Typical Applications

GKHW is used to produce nitrided parts which need to be extremely stable after hardening and tempering. It is particularly suitable for producing parts that undergo special nitriding.

GKHW has been successfully used for decades in the most critical mechanical components within Aerospace, Motorsports, injection systems, firearms, retaining rings, etc.

  • Gears, spindles, machine-tool fittings
  • Crankshafts, precision parts, aircraft parts
  • Thrust rings, bearing races working up to 400 °C

Comparisons to Other Materials

GradeTechnology Case propertiesCore propertiesLf case hardened material (Mpa/KSI)
Operating temperature (°F)Top hardness (HRC)Case depth (mm/in)UTS (Mpa/KSI)YS0,2 (Mpa/KSI)K1c (MPa.Vm)
9310 RemeltedCarburizing300601.40/.0551150/167900/1311201050/152
AMS 6308390601.40/.0551172/170965/140126/
AMS 650984062.51.40/.0551578/2291370/19993/
AMS 6475Deep nitriding84065.500.45/.0181240/1801150/167//
 Heat TreatmentUTS0.2% YSEKVSurface Hardness
  (MPa / Ksi)(MPa / Ksi)(%)(J /
M50 VIM/VAR1100°C / Gas, -75°C, 3 x 550°C Through hardened to HRC: 60 – 63 
9310 VAR & VIM/VAR825°C / Oil, -75°C, 150°C1150/167900/13114140/10360
M50NIL1100°C / Oil, -75°C, 3 x 540°C1400/2031200/1741512/960
GKH Remelt (W) & VIM/VAR (YW)920°C, Oil, 600°C1250/1811060/15415130/9665.5
 920°C, Oil, 640°C1080/157900/13119170/12565.5
GKP Remelt (W) & VIM/VAR (YW)940°C, Oil, 600°C1430/2071280/1861450/3767
 940°C, Oil, 640°C1250/1811075/1561680/5967

Chemical Composition


Stocking Sizes

Bar: 5.512″ & 6.299″ (140mm & 160mm)

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