5. Thermochemical treatments

5.1 Resilience and wear resistance

In mechanical engineering, it is often necessary for parts to have both high resilience and high wear resistance, as in the case of vehicle axles. However, these two fundamental requirements are generally at odds with each other, making it difficult to achieve them simultaneously. To solve this problem, thermochemical treatments have been developed to create heterogeneities in initially homogeneous parts. These treatments aim to significantly increase the hardness of a part's periphery without altering its internal hardness.

This is achieved by modifying the surface layer of a metal by diffusing an element such as carbon, nitrogen, etc., from its surface. This diffusion takes place at a high temperature, but does not exceed...