I processi CLIN fanno intervenire un numero molto limitato di parametri di trattamento: tempo di trattamento, temperatura di trattamento, chimica e pulizia dei bagni.
Alcuni parametri sono perfettamente controllati e offrono quindi un’eccellente ripetibilità e uniformità del trattamento.
CLIN processes use only a very limited number of treatment parameters: treatment times, treatment temperature chemistry and cleanness of the baths.
These parameters being perfectly controlled, they offer excellent repeatability and uniformity of treatment.
The main advantages of CLIN treatments compared with gas processes are:
Here are a few more detailed comparisons between CLIN processes and gas nitriding processes:
Cleanness of parts:
The cleanness of parts, for a CLIN process, has only moderate influence. Indeed, simple alkaline degreasing is sufficient.This is not the case for gas nitriding processes for which intensive cleaning is necessary before treatment.
A temperature variation of 20°C can create a variation of the thickness of the combination layer of 50%. It is therefore essential to control this parameter.
In a CLIN process, the temperature distribution is uniform and the transfer of heat very fast because it is produced by conduction. Indeed, the temperature difference between 2 distant points in the bath does not exceed 1°C.
This is not the case for gas processes, which cause a stream of cold gas slowly brought to temperature by radiation or convection to interact.The temperature differences for a same charge are then 10 to 20 times greater than CLIN processes. Gas processes are therefore more subject to deformation of parts during treatment and to a considerable dispersion of results.
The chemistry of CLIN processes is very stable even in intensive production. A daily regeneration and a regular chemical analysis are sufficient.
The nitrogen power of CLIN processes is about 1,000 times higher than that of gas nitrocarburizing processes. It is difficult to analyse the atmosphere inside a gas nitrocarburizing oven. Analysis is complex and approximate.
Gas treatment times are 3 to 6 times longer than CLIN treatment times.
The environment aspect of CLIN processes is more detailed here.
Gas processes, for their part, use a nitriding gas, Ammonia, classified as Toxic, Polluting and Corrosive.A quantity of nitriding gas corresponding to about 3 times the volume of the oven is necessary.
During the treatment, the ammonia does not dissociate totally and is discharged into the atmosphere via the oven's gas flues. The flue gases therefore have an ammonia concentration which can be very high as the figure below shows.