## 3 Results  
Table 1 provides the depth-averaged GDOES data for elemental compositions of coatings deposited on brass. Six groups of Cr-Al-Ti-B-N coatings were deposited. The deposition rate was \(\sim\)30 nm/min. All elements were distributed evenly across the coating's thickness of 3-4 \(\upmu\)m (Figure 1). In the B-free coating, the N content is below the saturation, e.g., 43.5% of N. However, the nitride's non-metallic sublattice probably also contains the oxygen and carbon, i.e., N + O + C = 48.3%, which is closer to stoichiometry. To avoid possible confusion, it should be noted that two sources of Ti atoms were used for deposition: TiB and Ti targets. Therefore, the coatings contained titanium even when the sputtering current on the TiB target was 0. An increase in the current supplied to the TiB target from 0 to 0.5 A led to higher concentrations of boron and lower concentrations of nitrogen in the coatings. It also somewhat decreased the measured Ti/Al ratio in the coating. This apparent increase in aluminum content is probably caused by the conditioning of the targets and formation of interlayers. The boundaries of interlayers are not clearly defined, and the signal from the interlayer might have got mixed into the calculation of average concentration values. XRD patterns (Figure 3) feature pronounced peaks at 2\(\theta\) = 70\({}^{\circ}\), which correspond to the Si substrate. FCC CrN-related peaks (111), (200), (220), (311) were located at 2\(\theta\) = 38.6\({}^{\circ}\); 44.8\({}^{\circ}\); 65.6\({}^{\circ}\); and 82.8\({}^{\circ}\). TiN peaks (111), (200), (220), and (311) TiN were detected at 2\(\theta\) = 37\({}^{\circ}\); 41\({}^{\circ}\); 63.3\({}^{\circ}\); and 78.1\({}^{\circ}\). AlN was not detected, suggesting the complete dissolution of aluminum in CrN and TiN. Coatings with 0-2.3 at.% feature no peaks of boron-based phases. Coatings with 7.3 at.% were X-ray amorphous, so no discrete peaks of nitride or boride phases could be discerned. A further increase of B content prompted the formation of the CrB\({}_{2}\)-based phase with a peak at 2\(\theta\) = 33.9\({}^{\circ}\). Crystalline sizes were calculated from peaks' broadening using the Scherrer's formula. The size of CrN crystallites calculated using (111), (200), (220), and (311) peaks was 17-19 nm in the boron-free coatings and decreased to 9-16 nm upon introduction of 2-2.3 at.% B in the coating. The size of TiN crystallites estimated on the basis of (111), (200), and (220) peaks in the baseline coatings and in the coatings with 0.4 at.% boron was \(d\) = 30-50 nm and was reduced by 40% in the coatings with 2 and 2.3% B (\(d\) = 13-28 nm). Coating P5 with 7.3% boron was X-ray amorphous. Coating with 10 at.% B had a fine structure, but the estimation of crystallite size was complicated by the overlapping of peaks on the related XRD pattern. Lattice parameters for FCC CrN were \(a\) = 0.405-0.410 nm, which is considerably lower as compared to the standard value (0.414 nm). The lattice parameter for TiN was \(a\) = 0.423 \(\pm\) 0.001 nm, which is relatively close to the standard of 0.424 nm. Nanoindentation data was used to plot the dependence of hardness (\(H\)), Young modulus (\(E\)), elastic recovery (\(W\)), as well as of \(H\)/\(E\) and \(H^{3}\)/\(E^{2}\) ratios on the boron content (Figure 4). Coatings P3 and P4 containing 2 and 2.3 at.% B were characterized by the max hardness \(H\) = 15 GPa, which decreased with the growing B concentration. The boron-free coating was characterized by relatively low hardness \(H\) = 10.4 GPa and elastic recovery \(W\) = 0.47, but possessed high Young modulus \(E\) = 190 GPa. \(H\)/\(E\) and \(H^{3}\)/\(E^{2}\) ratios for the investigated coatings were also highest for the coatings with a boron content of 2.3 at.% and decreased with further boron enrichment. Therefore, hardness and elastic-plastic characteristics were maximal for the coatings with 2 and 2.3 at.% B.  
Figure 3: XRD patterns for the Cr–Al–Ti–B–N coatings.