Treatments and surface coatings for tribological usage

During operation, the surfaces of mechanical components are subjected to mechanical, thermal and/or physicochemical stress.

Mechanical stresses translate into stresses that become maximum near surfaces, as in the case of bending or torsional stresses. In addition, surface irregularities - shape and roughness - can lead to stress concentrations that create additional zones of fragility.

Thermal stresses can originate from the general environment or from the heat generated by friction in the contact.

Physico-chemical stresses are caused by environmental aggression from the outside world, which can lead to corrosion, oxidation or, in certain circumstances, embrittlement.

For components with tribological functions, these stresses are supplemented by those generated by contact actions, which may be of mechanical, thermal, electrical or physicochemical origin.

It is therefore important that the properties of the surface layers are superior to those required for bulk materials. Achieving high-level properties across the entire component volume would require materials that are too costly and difficult to process, or could even lead to disadvantages such as embrittlement or a lack of component flexibility.

These difficulties can be solved by surface treatments or coatings, which give surfaces properties that ensure satisfactory resistance to the various types of stress to which they are subjected, while retaining materials with lower core properties, which are less costly or easier to process.

Over the last few decades, surface treatments and coatings have been developed and modified to offer a wide range of possibilities for improving the mechanical properties of components, their resistance to physicochemical aggression, or their properties for fulfilling tribological functions. The aim of this dossier is to bring together the elements needed to achieve the latter.