Ceramics are defined as non-metallic, inorganic materials. Hardness and thermal insulation are commonly recognized properties. Chosen correctly, it's true: Ceramic coatings can resist wear, insulate from heat, even promise dimensional and chemical stability. Nitrides. Oxides. Carbides. Borides. When do you use them? How do you choose?
Especially when physical, chemical and mechanical properties vary among them.
No different than selecting a metal or polymer coating, the answer is simple: Understand the environment.
For example, where possible, avoid tension. Base material properties subject to plastic deformation or cyclic stress can lead to fracture. Even if you have polished and allowed for more "friendly" flat-to-flat contact between surfaces.
Thermal cycles, too, can affect fatigue strength. So be sure your design allows for heat liberation by the counter-face, or other transfer path.
Generally, the harder materials are carbide-based. Followed by oxides, known mostly for their low thermal conductivity. And nitrides, used for their chemical stability and surface compatibility in motion, rubbing against other materials.
Have you identified your current failure mode?
Is it adhesive wear? If higher contacting pressures present no issue, choose the harder material. For abrasive or erosive wear, consider critical (shear) angle, ceramic hardness, and toughness of the parent material. Size and shape of the abrasive impingement, too, can affect contact load, and whether burring or deformation occurs.
For tribological needs, it's also about lower friction. Materials of a carbonaceous nature can be ideal.
Maybe it's an engine you need to coat. Or a piston, header, exhaust or manifold requiring a ceramic coating. Just know your base material choice is equally important. Metallurgy, hardness, toughness and thermal stability can all help shape the success of your ceramic coating.