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The Case for FNC with Post Ox

Liquid Nitriding

FNC - Post Ox
Liquid Nitride Sample Part

what is this process?

Liquid nitriding immerses parts into a molten salt bath (typically cyanates and other salts). This allows for the diffusion of nitrogen and carbon into the surface of the part.

 FNC Sample Part

What is this process?

Ferritic NitroCarburizing (FNC) uses ammonia and other gases in a controlled and continuously monitored environment to supply the nitrogen and carbon for diffusion into the part.

400X Nital Etch

400X  Nital Etch. Liquid Nitride: Compound and Diffusion Layers

Why has liquid nitriding been so popular?

  1. High surface hardness and wear resistance.
  2. Enhanced fatigue resistance.
  3. Enhanced corrosion resistance.
  4. Reduced risk of distortion.
  5. Lustrous black finish.
 FNC 400X Nital Etch

400X  Nital Etch. FNC: Compound and Diffusion Layers

what are the similarities to liquid nitriding?

  1. High surface hardness and wear resistance.
  2. Enhanced fatigue resistance.
  3. Enhanced corrosion resistance.
  4. Reduced risk of distortion.
  5. Attractive charcoal-gray finish.


Packers Plus and NOV have approved this process as an acceptable alternative to Liquid Nitriding.

sample case depth: Liquid Nitriding


Liquid Nitride Case Depth
Typical Case Depth Report with QPQ (AISI 4140HT)

Sample CAse Depth: FNC with Post Ox



Typical Case Depth Report with FNC (AISI 4140HT)

Concerns with Liquid Nitriding

  1. Operator safety is a top concern with this
    technology due to processing parts in molten salts.
  2. This is an old technology. This legacy process
    is not being renewed or updated.
  3. Managing, containing, and disposing of the salt waste creates various environmental concerns and costs.
  4. High labour input increases the cost of this process.

Advantages of fnc-post ox

  1. Atmosphere continuously monitored with hydrogen sensors.
  2. Kn, the nitriding potential, is controllable and adjustable.
  3. Less porous, higher quality compound layer.
  4. Continuous data logging for traceability and quality control.
  5. No hazardous solids or wastewater disposal, and safer operating conditions for our staff.
  6. Larger capacity furnace.
  7. Lower cost.
Liquid Nitride Furnace

liquid nitrIding - permanently decommissioned

Industry standard no longer being updated.

 Gas Nitrider 2 FNC

fnc - post ox process capacity

75" long

39" diameter

3000 pounds


What does it all mean?


FNC is the modern, environmentally preferred alternative to Liquid Nitriding and offers greater process control, equivalent to better part properties, and lower costs.


Our FNC process is not yet available for use with stainless steels, but a solution is being developed.


Case Depth Report Comparison:



Contact Thermex for more information on our FNC - Post Ox



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