Controlled Liquid Ionic Nitriding / Salt Bath Nitriding Overview
Liquid nitriding is a subcritical surface enhancement process with one of the longest track records of success of any case hardening technology. It is widely used to enhance the wear and corrosion resistance of low alloy steels and stainless steels.
In a liquid nitriding bath which is maintained between 500 - 630°C (930 - 1165°F), nitrogen-bearing salts produce a controlled and highly uniform release of nitrogen at the interface of the workpiece. Nitrogen diffuses into, and chemically combines with, nitride-forming elements in the metal, producing, through a catalytic reaction, a tough, ductile compound layer with exceptional engineering and wear properties. This compound layer has wear properties that are 200% to 1000% greater than the original material, and greatly enhanced resistance to corrosion, galling and scuffing. Below the compound zone is another distinctive region, the diffusion zone. This results from the progressive diffusion of nitrogen and the formation of a solid solution of nitrogen in the base material. The diffusion zone contributes a critical fourth benefit of salt bath nitriding: substantial enhancement of fatigue strength, typically 20% to 100%.
| Property | Main Influence | |
|---|---|---|
| Compound Layer | Diffusion Layer | |
| Wear Resistance | X | |
| Scuffing Resistance | X | |
| Running Behavior | X | |
| Corrosion Resistance | X | |
| Hot Strength | X | X |
| Rotating Fatigue Strength | X | |
| Pressure Load-ability | X | |
| Rolling Fatigue Strength | X | |
Some of the benefits that can be realized through liquid nitriding treatments include:
- Superior wear resistance
- Excellent friction properties
- Good scuffing/seizure protection (adhesive wear) thanks to ceramic characteristics of the surface
- Excellent corrosion protection
- Good surface fatigue resistance
- Decorative black surface
- No deformation or distortion of the part; treatment done on finished parts
- Environmentally sound