*2.1. Coatings Preparation*

Both coatings were prepared by the cathodic arc deposition process. For TiCN, one Ti cathode (99.99% purity) was used, while for TiSiCN, a Ti+Si cathode (85 at.% Ti and 15 at.% Si; 99.9% purity) was used. The cathodes were supplied from Cathay Advanced Materials Limited, Guangdong, China. The coatings were prepared using both CH4 and N2 as reactive gases (99.999% purity, Linde). The position of each cathode inside the deposition chamber was the same as those described in [33]. In order to guarantee the uniform thickness of the coatings, the substrate holder was rotated by 15 rot/min. The CoCr substrates (ASTM F75 CoCr alloy) were cut into 12 mm discs and polished up to Ra roughness of 46.9 ± 5.9 nm. Each substrate was ultrasonically cleaned in trichloroethylene and flushed with dry nitrogen, and then introduced in the deposition chamber. To eliminate any impurity, the substrates were sputter etched with Ar<sup>+</sup> ions (1 keV) for 15 min. The deposition parameters are listed in Table 1, and were maintained constant during all deposition runs. The same negative substrate bias voltage was applied on both cathodes and the substrate temperature was around 320 ◦C. The thickness of the coatings was around 2.5 μm.


**Table 1.** Conditions for the developed coatings.
