Ten minutes after spark plasma sintering of 10 different mixtures at 1700°C, 47 MPa, their relative density and flexural strength were analyzed in Minitab. Different regression models were obtained for each property. The behavior of relative density and flexural strength was explained by two quadratic models RD<sub>Q</sub> and FS<sub>Q</sub>, which were adequate with a statistical significance level of p = 0.05. Based on the models RD<sub>Q</sub> and FS<sub>Q</sub>, contour plots were made in the Al<sub>2</sub>O<sub>3</sub>-TiB<sub>2</sub>-TiC simplex for a visual representation of the predicted results. These contour plots show the zones corresponding to values of relative density > 99%, and flexural strength > 500 MPa. Combining these zones, it was possible to determine the region of the Al<sub>2</sub>O<sub>3</sub>-TiB<sub>2</sub>-TiC simplex, which simultaneously correspond to the relative density and flexural strength of sintered samples greater than 99%, and 540 MPa, respectively. The RD<sub>Q</sub> and FS<sub>Q</sub> models were additionally tested at three new points, revealing that additionally experimental values fit well into the predicted by Minitab intervals. Therefore, the RDQ and FSQ models can be used for the relative density and flexural strength prediction of Al<sub>2</sub>O<sub>3</sub> -TiB<sub>2</sub> -TiC composites sintered as described.

The properties of three Ti-TiN-(Ti,Cr,Al)N coatings, which have identical thickness and elemental composition, but a different scheme of ion etching by glow discharge plasma during the deposition process, were compared. Various etching times of the substrate before coating deposition were considered, as well as the use of additional etching during the deposition process and after coating deposition. It was found that additional etching in a glow discharge plasma during the deposition process and after completion of coating deposition increased the hardness by 100-300 HV units. Increasing the time of preliminary etching of the substrate surface before coating deposition from 5 to 10 minutes allows significant increase of the resistance to destruction during the scratch test (from 22 N to 38-40 N). Additional etching by glow discharge plasma during the deposition process and after coating deposition can increase the tool life by 30%. The coating deposited after pre-etching the substrate for 5 minutes, without additional etching operations, exhibits a brittle nature of failure combined with partial delamination from the substrate, while coatings pre-etched for 10 minutes maintain a strong adhesive bond to the substrate. Additional etching during the coating deposition process creates an interface that slows down the overall degradation of the coating during the cutting process, thus increasing the overall wear resistance of the tool.

A three-dimensional combustion synthesis model of the composite material in a titanium (Ti)-boron (B)-aluminum (Al) system, which takes into account the melting of all components, detailed kinetics of the process, evolution of the porosity, and dependence of the thermophysical properties on the structures and composition of the material, is proposed. It was found that the main phases were TiB<sub>2</sub> and TiAl in the final composite. The fraction of the other phases was less than 1%; preheating of the reaction mixture from 20°C to 300°C led to a slight increase in the intermetallic phases (about 1%) and a decrease in the boride phases. The results showed that the synthesis of the composite material with a composition of (1-a) · (Ti + Al) + a · (Ti + 2B) under the experimental conditions, in which a = 0-0.5, proceeded in the wave mode without twisting of the reaction front. The theoretical results were consistent with the experimental data.

ZrN, (Zr, Hf) N, and (Zr, Ti) N coatings were deposited on a Ti-6Al-4V titanium alloy substrate. Scanning and transmission microscopy showed that a defective layer 2-3 μm thick is formed during grinding of the titanium alloy. Microcracks and other surface defects are observed in this layer. Healing (sealing) of cracks and other surface defects is observed during coating deposition. It was found that crack sealing begins during ion etching and is completed during deposition of the adhesive and wear-resistant coating layers. Thus, the coating not only increases the surface hardness and wear resistance of the product, but also allows to some extent reduction of defects in the surface layer of the substrate.

The MAX phase (Ti<sub>2</sub>AlN) was synthesized by reaction sintering of Ti, TiN, Al precursors in vacuum in quartz ampoules. The effect of temperature on the formation of the Ti<sub>2</sub>AlN phase was estimated. The MAX phase with a minimum amount of impurities was obtained at 1300°C. The elemental and phase composition and structure of the synthesized samples were studied. According to the X-ray diffraction analysis, the obtained samples, along with the main phase Ti<sub>2</sub>AlN, contain impurity phases TiN, TiAl, Ti<sub>3</sub>Al. The results of electron microscopy show heterogeneity of the elemental composition of precursor particles, which differ in size and morphology. In well-formed crystallites of the MAX phase with a layered structure, the Ti/Al/N element ratio is close to the stoichiometric composition of Ti<sub>2</sub>AlN. The quality of the layered structure of Ti<sub>2</sub>AlN and the simplicity of the synthesis technique make the material promising for some applications, in particular, for obtaining 2D MXene (Ti<sub>2</sub>N) particles.

In this paper, we describe our work on the formation of silicon-carbon (Si-C) coatings by electron beam evaporation of a silicon carbide target in a medium vacuum using a forevacuum-pressure plasma-cathode electron source. The films obtained were characterized, which showed that the properties of the Si-C coatings were similar to those prepared by plasma-chemical methods.

The effectiveness of using ZrN and TiN coatings to increase wear resistance and to reduce the coefficient of friction on the working surfaces of parts made of titanium alloys are discussed. Even though the TiN coating has a slightly higher hardness, when studied by the pin-on-disk method with an indenter made of 52100 Bearing Steel, the sample with the ZrN coating showed noticeably better wear resistance. The ZrN-coated sample also provides a noticeable reduction in the friction coefficient (up to 0.25) compared to the uncoated sample and the TiN-coated sample. Thus, ZrN coating can be used effectively to increase the wear resistance of contact surfaces of parts made of titanium alloys.

ZrN, (Zr,Ti)N, (Zr,Hf)N, (Zr,Nb)N, (Ti,Zr,Hf)N, and (Ti,Zr,Nb)N coatings mechanical and corrosion properties were investigated in this work. Coatings were deposited by vacuum arc deposition technique on Ti-6Al-4V titanium alloy. Microhardness measurements, tribological and scratch tests, profilometry, electrochemical corrosion tests, and scanning electron microscopy were used as investigation techniques. The highest microhardness value (36.2 GPa) was observed for the (Zr,Hf,Ti)N coating, and the lowest value (12 GPa) for the (Zr,Nb)N coating. The highest critical forces Lc3 during scratch tests were found for coatings containing hafnium. It was revealed that the shape of anodic potential dependence on time during electrochemical corrosion tests in galvanostatic mode (3% NaCl environment) was strongly dependent on coating type. The time necessary to reach the maximum stable value of anodic potential can be an indirect parameter of corrosion resistance. (Zr,Nb,Ti)N coating demonstrated the best corrosion resistance in used test regimes.