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Nitriding hardens the outer surface of a metal by diffusing nitrogen into it under heat. It is a heat-treating process, but the temperatures required for nitriding are lower than other heat treatment techniques, and it takes much longer in the furnace..

Nitriding is suitable for surface hardening medium- and high-carbon steel alloys. It’s also effective with ferritic stainless steels such as 420, and precipitation hardening steels such as 17-4. In addition to surface hardening, nitriding improves several other properties of the alloy, including wear and corrosion resistance. Nitriding is a preferred hardening method for many components used by the automotive, firearms, die fabrication, and tool-making industries.  

Thermo-Fusion is an ISO 9001:2015 and AS9100D certified company based in the San Francisco Bay Area. We have been providing nitriding and other metallurgical services for more than 50 years.


Materials Used in Nitriding

The nitriding process forms alloy nitride precipitates at the surface layer of a metal by infusing free nitrogen into the metal. Aluminum, chromium, molybdenum, titanium, tungsten, and vanadium easily combine with nitrogen at high temperatures to form nitrides of the respective metals. Low-carbon alloys of steel containing these metals are typically good candidates for nitriding. The primary steel alloys used for nitriding include:

  • -SAE 4130
  • -SAE 4140
  • -SAE 4150
  • -SAE 4340
  • -AISI 8640
  • -17-4 (aka SAE 630)
  • -15-5
  • -400 series stainless steel
  • -Nitralloy 135®

Thermo-Fusion offers nitriding of all the steel alloys listed above.

Nitriding Applications

Nitriding is a hardening process favored by metallurgists because it is a relatively low-temperature technique, which mitigates the risk of part distortion. Nitriding is widely used for surface hardening of components such as:

  • -Bearings
  • -Cylinder liners
  • -Dies
  • -Feed screws
  • -Gears
  • -Orifice disks
  • -Piston rings
  • -Shafts
  • -Splines
  • -Spray nozzles
  • -Valves

Advantages of Nitriding

The temperatures used in nitriding are not high enough to warp and distort metal parts. Additionally, nitriding allows slow cooling of the components, which also avoids distortion. Nitriding increases the specific volume of steel at the surface of the alloy, producing the following benefits:

  • -Produces a high hardness of 700-1000 HV (60+ HRC) for operating temperatures below 1000 °F
  • -A reduced coefficient of friction, improving both fatigue life and time to failure for rolling contact fatigue
  • -Enhanced scuff and wear resistance
  • -Increases anti-galling, anti-welding, and anti-seizing properties
  • -Higher corrosion resistance

Thermo-Fusion undertakes small and large nitriding jobs as well as development projects. We offer a variety of other metallurgical services as well, including:

  • -Annealing
  • -Brazing (hydrogen, torch, vacuum, air)
  • -Carburizing
  • -Cryogenic treating
  • -Hardening (case, through, vacuum, flame)
  • -Heat treating
  • -Induction annealing and hardening
  • -Stress relief

Our  Thermo-Fusion team has extensive experience in engineering and manufacturing processes. We maintain the highest quality standards and exceed our customers’ expectations for timely delivery and prompt service. We are a proud member of many industry associations, including the Metal Treating Institute (MTI), Society of Manufacturing Engineers (SME), and American Welding Society (AWS).

Contact us today to find out more about Thermo-Fusion and our capabilities.