Alloying a hard phase with a solid lubricant : an approach concept for hard, self-lubricating PVD coatings for tribological applications

Friction and wear are not desired for many applications. One way to diminish the wear of a component is to coat it by Physical Vapor Deposition (PVD) with a thin, wear resistant hard coating. This approach has proved very successful for the past decades. Although increasing the wear resistance and thus the lifetime of the coated components, almost all wear resistant coatings used in industry nowadays do not solve the problems associated with friction, e.g. excessive heating, high energy losses, etc. Lubrication with various liquid and solid lubricants has been known to be a good solution to these problems for millennia. However, nowadays environmental and technical requirements reduce more and more the fields of application of the above mentioned lubrication methods. Therefore, it would be very beneficial for industry if high hardness, wear resistance and lubricating properties can be all combined in a coating. Thus both friction and wear problems will be diminished without the need to use external lubrication. In this work an effort is made to design a group of such PVD coatings by mixing doping a hard, wear resistant phase (TiN) with a well-known solid lubricant (MoS2). The mixing is made by sequential deposition of thin layers of both phases in order to realize a multilayer TiN/MoS2 structure and by co-deposition of both components in order to realize mixed-phase TiN+MoS2 coatings. The influence of the deposition conditions on the structure and the tribological and mechanical properties of the above mentioned coating architectures is studied. A conclusion about the feasibility of both concepts (multilayer and mixed coatings) is also made in this work.