*2.2.6 Analysis of 97MXC coatings adhesion*

The adherence of the deposits obtained by thermal spraying is defined as being the force necessary detaching the layer from the substrate. The studies carried out by Haraga et al. [47] have demonstrated that the adhesion of the coatings is predominantly mechanical and is due to the solidification of the sprayed liquid particles or to the deformation of the semi-viscous particles on the substrate asperities. The adhesion of the deposits was determined by the traction test - in accordance with EN 582.

**Figure 18** presents the adhesion variation of the deposits with the pressure of the compressed air passing through the primary circuit. It is noticed that at low values of the compressed air pressure the layer adhesion to substrate has low values. It can observe that for the same value of the compressed air pressure which passes through the primary circuit adhesion values of the deposit vary with the current intensity.

Thus, for the same pressure value, the adhesion of the 97MXC coatings obtained at I = 250A is superior to the one of the other coatings obtained at I = 200A and I = 220A, in the same technological conditions. Knowing that by the increasing of the current intensity of the electric arc temperature increases, we can suggest that, at high values of the current intensity, the drop formed in the electric arc is atomized into small particles with reduced inertia. Studies carried out by Toma et al. [33], have demonstrated that the high pressure of the compressed air favors the

**Figure 18.**

*Variation in the adhesion of 97MXC deposits with the compressed air pressure passing through the primary circuit.*

increase of the impact velocity of the particles with the substrate surface, respectively their better fixation in the surface roughness. This aspect determines the increasing the adhesion of the 97MXC deposits with the increase of the compressed air pressure.
