Thermochemical surface treatments - Presentation and classification

Surface treatments are a vast family of processes designed to enhance the mechanical performance of treated parts.

Thermochemical diffusion or carburizing treatments, mainly using carbon and nitrogen (carburizing commonly called "cémentation", "carbonitruration", "nitruration", "nitrocarburation"), are, along with surface hardening, the most widely used methods for strengthening mechanical parts made of iron-carbon alloys (steels and cast irons).

Thermochemical treatments, however, cover all the families of processes that lead to chemical transformation by diffusion of the surface zone of treated parts. The mass is modified, but the dimensions remain unchanged.

They are distinguished from :

• CVD (chemical vapor deposition) ;

• PVD (physical vapour deposition) ;

• PACVD (Plasma-Assisted Chemical Vapor Deposition).

These are deposited by condensation of a defined compound, without modifying the chemical nature of the substrate surface (with the exception of the nanometric adhesion zone).