**1. Introduction**

There is a multitude of technological processes that allow the modification of the physico-chemical and mechanical properties of the surfaces in order to increase the performance in operation, the service life, or the esthetic aspect, [1–3].

The improving the surface properties, by thermal spraying, is carrying out by depositing new materials on the existing surface in order to give it new properties. Therefore, "thermal spray" is a general term that groups a set of processes, by which a material is melted under the action of a heat source, then is projected using a carrier gas on the surface of a part [4–6].

Coating via thermal spraying consists of the acceleration of fine particles from a certain metallic material, in a molten or semi-molten state, onto a specially prepared surface. The sprayed material is called coating material (CM) and the surface on which the deposition is made is called substrate (S), [7–10]. The layer produced by thermal spraying becomes a constituent part of the base material and gives it specific properties: hardness, corrosion resistance, wear resistance or new functional properties (chemical, electrical, magnetic).
