**2.3. Morphological and tribological characterization**

Crystalline phases were identified by powder X-ray diffraction (XRD) using a Bruker diffrac‐ tometer model D8 Advance (Bragg-Brentano arrangement, Cu rotating anode). The samples were evaluated over the 2θ range from 30° to 95° at a rate of 0.2° s-1.

Glow discharge spectrometer (GDS) (Leco, Mod. 850A) was employed to obtain elemental composition of the coatings as a function of depth into the coatings.

The coatings hardness value was the average of ten measurements obtained on a Matsuzawa MXT-α7 on the Vickers scale with a load kept at 10 g for 15 s.

A reciprocating ball-on-disk tribometer (CSM tribometer instruments) was used to wear tests. All tests were nonlubricated and carried out under dry at 25 °C temperature and relative humidity of 39%. A 3-mm AISI 8620 ball bearing was used as the counter body under a 2-N load at a sliding speed of 1 cm s-1. The friction coefficient of the three wear tests was recorded, and the wear volume was measured according to the ASTM G99 standard method.
