Gas Nitrocarburizing VS. CLIN Technologies
Posted on Nov 07, 2024Nitrocarburizing is the most common thermochemical treatment, consisting in enrichment of the surface of ferrous materials with Nitrogen and a small amount of Carbon. The treatment is used to enhance the corrosion and wear resistance and tribological characteristics of parts.
There are a few methods of preforming Nitrocarburizing, depending on medium, each with unique advantages. This article will compare the main two industrialized processes of Gas nitriding and CLIN™ technologies.
Processes comparison
The main difference between both treatments is the physical medium used to allow nitriding: gaseous or liquid medium. Depending on the medium used, the process would be different, as synthesized in the following table:
| Gas nitriding | CLIN™ technologies | |
| Preparation | Organic solvent degreasing | Alkaline soap rinse degreasing |
| Application methods | Suspended parts in sealed gas chamber | Dips parts in molten salts |
| Temperature range | 500 – 740°C | 500 – 630°C |
| Temperature homogeneity | circa ± 15°C | circa ± 3°C |
| Thermal transfer | Convection | Conduction |
| Nitriding potential |  medium |  high |
| Treatment time | 6h – 24hours | 1h – 3hours |
| Environmental/waste | Gas exhaust cracking/burnt/released into atmosphere | Recycling of line wastes into new consumables directly usable |
| Material classification | Ammonia (anhydrous) | Cyanates and carbonates |
Their respective processing methods – being quite different – are responsible for the unique effects each have on treated part. The temperature homogeneity control is quite different between gas nitriding and CLIN™ technologies. This is due to the difference of medium, rather than gas, CLIN™ is based on liquid medium (molten salts). Liquid allows a better control of temperature homogeneity compared to gas. Also, liquid enables complex geometry treatment, as it spreads uniformly everywhere in the bath. This allows to have a better treatment homogeneity of the parts.
Parts are in direct contact with liquid and therefore use conduction for heat transfer. Gas uses convection which is not as efficient. This efficiency is also bonded with nitriding potential, directly linked to the chemical composition of the medium. Contrary to gas using Ammonia (NH3), CLIN™ technologies use cyanates (CNO–). These chemical compounds are more effective to create nitriding reactions, allowing fastest treatment times. Thus, the liquid medium of CLIN™ offers the fastest and most uniform nitriding treatment.
Regarding environment and wastes,ECO-CLIN™ innovation process is allowing a circular model by recycling, into new consumables directly usable on CLIN™ line. As a first step, most of Europe lines’ wastes are recycled by this time; the ambition of the group is to achieve zero final waste within its worldwide network.
Advantages and limitations of CLIN™ compared to gas
Advantages:
- Uniform compound layer thickness even on parts with complex geometry.
- Better dimensional control on parts.
- Minimal to no-distortion on parts.
- Better adhesive wear resistance, due to post-nitriding enhanced oxidizing step.
- Better oil retention.
- Enhanced corrosion resistance.
Limitations:
- Masking is most of the time not possible.
- Less deep nitrogen diffusion
From an economic perspective, both processes, gas or liquid, are competitive technology well known in various industries as construction, handling, automotive, energy, aeronautics and defence.
Availability of CLIN™ technologies
CLIN™ is globally available with TUFFTRIDE®, TENIFER® & QPQ® treatments licensed to the subcontract heat treatment trade. ARCOR® and SURSULF® are version of CLIN™ commercially available throughout our global TS network. Our CLIN™ technologies are allowing best mastering of liquid salt bath ferritic nitrocarburizing treatment, especially for materials such as Nickel Alloys.
TSUK are based in Birmingham and have the largest salt bath pots in the country. Please contact us for further technical information or request a quotation.