## 2 Materials and Methods  
The coating was deposited on ERTi-1 titanium alloy plates (99.58-99.90% Ti; ASME SFA-5.16/SFA-5.16M [22]). The plate size was 16 \(\times\) 8 \(\times\) 2 mm (Figure 1a). Before the deposition of the coatings, the samples were prepared, including washing in a special solution with ultrasonic stimulation, rinsing in purified water, drying with a stream of purified heated air and final wiping with highly purified medical alcohol.  
Figure 1: General view of samples with deposited coatings (scratch test grooves are visible) (**a**) and general setup diagram and sample arrangement (**b**): 1—chamber; 2—rotary table (not rotated during coating deposition); 3—Controlled Accelerated Arc (CAA-PVD) system evaporator (with titanium cathode); 4—filtered cathodic vacuum arc deposition (FCVAD) system evaporator (with aluminum cathode); 5—vacuum system; 6—gas leak.  
For coating deposition, a modernized VIT-2 PVD installation (IDTI RAS--MSUT <<STANKIN>>, Moscow, Russia) [23; 24; 25; 26; 27] (Figure 1b) was used, in which two types of innovative evaporators are used:  
* An evaporator of the filtered cathodic vacuum arc deposition (FCVAD) system [28], allowing for the effective (up to 98%) separation of microparticles. This evaporator was used for aluminum (99.80% Al) cathodes due to the high generation of microparticles during aluminum evaporation.
* Evaporators of the Controlled Accelerated Arc (CAA-PVD) system were used to install a titanium (99.95% Ti) cathode [5; 29; 30].  
The arrangement of the samples in the chamber is shown in Figure 1a. The sample designated as T2 was located opposite the FCVAD evaporator with an aluminum cathode, the sample designated as T7 was installed in an intermediate position between the evaporators with aluminum and titanium cathodes (at an angle of 45\({}^{\circ}\) to the central axes of these evaporators) and the sample designated as T12 was installed opposite the titanium cathode. The samples were installed in the chamber according to the described scheme, then evacuation and preliminary etching in an inert gas environment (Ar) at a pressure of 0.20 Pa and an arc current of 100-150 A were carried out. Then, argon was removed and nitrogen (N) was supplied, final etching was carried out with a gas plasma flow (N) and then the coating was deposited for 30 min at a nitrogen pressure of 0.42 Pa, a bias voltage on the substrate of \(-\)150 V and arc currents by the cathodes of 65 A (for Ti) and 160 A (for Al).  
To study the internal structure of the samples, a JEM 2100 transmission electron microscope (TEM) (JEOL, Tokyo, Japan) was used; to study the composition of the samples, an INCA energy-dispersive X-ray system (EDX) (OXFORD Instruments, Oxford, UK) was used.  
Hardness was measured with a Nanovea SV-500 tester (Nanovea, Irvine, CA, USA) using a Berkovich pyramidal indenter at a load of 20 mN. Hardness was determined as the average value of the results of 40 measurements.  
Scratch testing was performed on a Nanovea SV-500 tester (Nanovea, Irvine, CA, USA) according to the ASTM \"Standard Test Method for Adhesion Strength and Mechanical Failure Modes of Ceramic Coatings by Quantitative Single Point Scratch Testing\" [31], in the load range of 0-40 N, using a conical diamond indenter with an angle of 120\({}^{\circ}\) and a radius of 100 \(\upmu\)m.  
Since measuring the hardness of coatings (superhard film on a significantly softer substrate) presents certain difficulties (associated, among other things, with the heterogeneity and anisotropy of the coating), 30 measurements were taken for each coating, obviously unreliable (too high or too low) values were discarded (no more than 5), then the average value and the spread of values were determined.