## 2 Materials and Methods  
Discs (\(\O\) 30 \(\times\) 5 mm) and pendants (40 \(\times\) 20 \(\times\) 2) were made from LS 59-1 grade brass by investment casting and used as substrates along with rectangular plates of monocrystalline (111) KEF-4.5 solar silicon and 12H18N10T steel. Cr-Al-Ti-B-N coatings were deposited using a UDP 850/4 magnetron sputtering device equipped with a CFUBMS system (Teer Coatings Ltd., Droitwich, UK). The elemental composition of the coatings was based on our previously published investigation of quarternary Cr-Al-Ti-N coatings with various contents of metallic components [44]. Deposition was carried out at \(\sim\)0.2 Pa pressure in Ar (99.998%) + N\({}_{2}\) (99.999%) atmosphere using four 90 mm \(\times\) 690 mm targets: Ti (99.99%), Al (99.99%), Cr (99.99%), TiB (81.6% Ti + 18.4% B). The TiB target (SHIM-4 grade) was manufactured by force SHS pressing. Before the deposition, all targets were conditioned for 10 min at 5 A current and 30 cm\({}^{3}\)/min Ar flow. To increase the adhesion and reduce the strain on the surface-coating interface, a thin Cr inter-layer was deposited in the Ar atmosphere. Al target was sputtered in impulse regime with frequency \(\
u\) = 50 kHz and impulse duration \(T\) = 200 microseconds. During the deposition of the Cr-Al-Ti-B-N layer, the Ar/N\({}_{2}\) flow was 30/30 cm\({}^{3}\)/min. Various currents (0; 0.5; 1; 1.5; 3; 5 A) were applied to the TiB target. All other targets were supplied with a constant 5 A current to prevent the over-heating and deterioration of brass substrates. The deposition duration was 90 min. During the deposition, substrates were rotated five times per minute. The residual pressure in the chamber was \(2.6\times 10^{-4}\) Pa. Cr-Al-Ti-B-N coatings were marked as \(\approx\)P1-6\(\approx\) (protective). To deposit the upper decorative Cr-Al-Ti-B-O-N layer, nitrogen was substituted by air in the supplied reactive gas mixture. Cr-Al-Ti-B-O-N coatings were marked as \(\propto\)D1-9\(\approx\) (decorative). The deposition process was preliminarily optimized in terms of gas flow and rotational speed. Chemical composition and element distribution profiles across the thickness of the coating were studied by glow discharge optical emission spectroscopy (GDOES) using Profiler 2 installation (\"Horiba Jobin Yvon\", Longjumeau Cedex, France). Microstructural analysis of the transverse fractures of coatings was performed on scanning electron microscope JSM-7600F (JEOL, Tokyo, Japan), equipped with the Oxford energy dispersive spectroscopy add-on. X-ray diffraction analysis (XRD) was performed on Bruker D8 installation using the monochromatic CuK\(\alpha\) radiation. Hardness (\(H\)), Young modulus (\(E\)) and elastic recovery (\(W\)) were measured by instrumental indentation at 4 mN load using Nano Hardness Tester (CSM Inst., Peseux, Switzerland) equipped with a Berkovich indentor. Tribometer (CSM Inst., Switzerland) was used for \"pin-on-disc\" tribological testing at an applied load of 1 N, 200 m distance and 10 cm/s linear velocity. Al\({}_{2}\)O\({}_{3}\) ball (\(d\) = 6 mm) was used as a counterpart. Coatings' abrasive resistance was estimated using a calowear-tester (NIITAvtoprom, Moscow, Russia). The 100 Cr6 steel ball (\(d\) = 27 mm) was used as a counterpart material. The slurry containing 15-\(\upmu\)m-sized diamond particles (Struers) was applied to the sample surface before tests. During the test duration (5 min), constant load (0.5 N) and ball rotation speed (153 rotations per minute) were applied. Coatings deposited onto LS 59-1 brass were subjected to sliding wear and abrasion testing. To ascertain the specific wear and abrasion impact, specimens were studied using optical profilometer Veeco WYKO NT1100 (Veeco, Plainview, NY, USA). Electrochemical testing was performed on potentiostat Voltalab PST050 (Radiomet analytical, Lyon, France ) in a thermostatic electrochemical cell equipped with AgCl comparative electrode, Lugin capillary and a secondary 1 cm\({}^{2}\) Pt electrode.