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Liquid Nitriding (Salt Bath Nitriding):
Frequently Asked Questions

Liquid Nitriding Properties / Miscellaneous

22: How does the surface hardness of LN parts compare to those of gas or plasma nitrided parts? Chrome plating? Nickel Plating?
Hardness levels produced by gas, plasma, or Liquid Nitriding are similar, ranging from between 600-1200 HV (60-70+ HRC). Hardness produced by nickel plating may be between 60 -65 HRC; hard chrome plating is around 70 HRC. Please note that surface hardness is usually measured on the Vickers scale (HV) rather than the conventional Rockwell C (HRC) scale.
     
23:   How does the salt spray corrosion resistance of LN parts compare to those of gas or plasma nitrided parts? Chrome plating? Nickel Plating?
The corrosion resistance produced by Liquid Nitriding will exceed that of gas or plasma nitrided parts, as well as, chrome and nickel plated parts, assuming equivalent layer depths. Hence, ARCOR® Liquid Nitriding/ QPQ processes are preferred by industries such as Oil & Gas where components experience both harsh erosion and corrosion environments. Also, automotive and industrial machinery components operating with minimal lubrication can experience significant performance improvements when treated with ARCOR® Liquid Nitriding.
     
24:   What is micro-porosity? What are its pros and cons?
Micro-porosity is a zone of micro-voids in the compound layer, formed mostly by excess nitrogen. This porous zone is beneficial as a reservoir for oils and lubricants, and is an effective break-in surface for mating components. However, if excessive, the porous zone can reduce corrosion resistance, and even compromise the strength of the compound layer itself. Hence it is important to control the distribution, morphology and extent of micro-porosity within the compound layer. The ARCOR® Liquid Nitriding process produces an optimum degree of micro-porosity.
     
25:   What is post-Nitriding impregnation? Why is this done?
TS USA offers the option of post-nitriding impregnation utilizing various proprietary oils or aqueous polymers to further enhance the corrosion resistance of the nitrided component. The controlled and customizable surface porosity generated by the ARCOR® Liquid Nitriding process is very effective in retaining the impregnated fluid and increasing the level of corrosion protection. This impregnation also provides additional surface lubricity which is very beneficial during the break-in operating phase of the component.
     
26:   Are there different kinds of impregnation?
Impregnation of Liquid Nitrided components involves the use of solvent-based or water soluble oils, or, aqueous polymers only. Many of the specific impregnation chemistries used by TS USA are proprietary and in combination with the appropriate ARCOR® treatment, can provide up to 1000 hours of salt spray resistance for specific component geometries and materials.
     
27:   What are the typical post-Nitriding polishing processes and what determines which one is selected?
Polishing methods used on Liquid Nitrided components are selected based upon the surface finish requirement and component size/design. Those methods include centerless polishing, vibratory polishing, soft shot blasting and glass bead blasting.
     
28:   How much is the surface roughness expected to increase after Nitriding?
Post-nitriding surface roughness will depend upon the specific nitriding process/chemistry, component material, cooling method, and nitride layer depth. However, typically, a Ra increase of 8-15 µin (0.4 µm) may be expected. Certain ARCOR® treatments result in lower surface roughness than conventional liquid nitriding.