**2.1 Tribological experimental details**

The tribological characterization of the coatings was performed under ASTM G99-17 standard, using a Microtest MT 4001-98 tribometer. This equipment consists of a rotating platform, with controlled speed on which the test sample is adjusted in an environment with or without lubricant. On this surface, a mechanical arm which contains a counterpart (100Cr6 or Steel 440) with a spherical shape of 6 mm in diameter in direct contact with the surface under study is adjusted. A load applied to the counterpart (5 N) is adjusted on this mechanical arm; with an angular velocity of 160 rpm and linear velocity of 0.1 m/s and other parameters of each tribological test are presented in **Table 1**. In addition, a JEOL model JSM-6490LVTM scanning electron microscopy (SEM) was used to observe the wear track. The adhesive characterization of the coatings was performed under ASTM G171-03 standard, using a Microtest MTR2 equipment, the parameter used in the test were; a sliding distance of 6 mm, variable load from 0 to 90 N and a sliding velocity of of 1.97 mm/min using a Rockwell C indenter. In addition, the identification of cohesive failure (Lc1) and adhesive failure (Lc2) was performed using the NANOVEA SCRATCH TESTER software, which analyzes the change of the friction coefficient versus load or distance, and the results were corroborated by optical micrographs and SEM micrographs of the scratch tracks. The coatings thickness and the wear scratch images were obtained by using a KLA Tencor D-120 profilometer; the thickness of all the coatings was 3 μm [6, 9].

