5. Conclusions

A variety of coatings have been presented in this article: polymers, metals and ceramics used under very different conditions. Indeed, there is no universal coating capable of solving every tribological problem. However, we have not covered all the problems encountered in practice, such as the electronic properties of certain films.

As we have seen, friction properties depend on the physical chemistry of the antagonists. Mechanical properties also play a role in friction and wear. For this reason, a reading of the examples presented can follow the following classification:

• soft coatings on hard substrates, which can be described as lubricants for the substrate. This category includes Teflon coatings, ski waxes, polyurethane floor coatings, thin layers of soft metals, coatings for polymer shaping and solid lubricants for forging;...