*3.2.2. Size of the particles and second phase*

The particles can create a dispersion-hardening effect so that they hinder the formation of dislocation in the grain, and act as pinning agents. Analogically, they can also hinder grain growth caused by annealing [8].

Reduction in the size of the particles in the composite coating increase the abrasion resistance. The reason for this case is less delimitation of the particles in the metal matrix. In a study on Cr-Al2O3 composite coatings, researchers indicated the reduction in the wear strength and brittleness when the amount of the particles was too big [10].

Another way to reduce the wear loss of surfaces moving relatively is to decrease the friction coefficient or lubrication. SiC particles create a lubricant film on the surface of Ni-SiC coatings. Because of the lubrication the wear resistance of the composite structure increases up to 2-3 times of a pure Ni coating. This has been proved by similar studies [10].
