Bioactive manganese (Mn)-doped ceramic coatings for intraosseous titanium (Ti) implants are developed. Arc plasma deposition procedure is used for coatings preparation. X-ray Diffraction, Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy, and Electron Paramagnetic Resonance (EPR) methods are applied for coatings characterization. The coatings are homogeneous, composed of the main phase α-tricalcium phosphate (α-TCP) (about 67%) and the minor phase hydroxyapatite (about 33%), and the Mn content is 2.3 wt%. EPR spectroscopy demonstrates that the Mn ions are incorporated in the TCP structure and are present in the coating in Mn²⁺ and Mn³⁺ oxidation states, being aggregated in clusters. The wetting contact angle of the deposited coatings is suitable for cells’ adhesion and proliferation. In vitro soaking in physiological solution for 90 days leads to a drastic change in phase composition; the transformation into calcium carbonate and octacalcium phosphate takes place, and no more Mn is present. The absence of antibacterial activity against Escherichia coli, Enterococcus faecalis, and Pseudomonas aeruginosa bacteria strains is observed. A study of the metabolic activity of mouse fibroblasts of the NCTC L929 cell line on the coatings using the MTT (dye compound 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test demonstrates that there is no toxic effect on the cell culture. Moreover, the coating material supports the adhesion and proliferation of the cells. A good adhesion, spreading, and proliferative activity of the human tooth postnatal dental pulp stem cells (DPSC) is demonstrated. The developed coatings are promising for implant application in orthopedics and dentistry.

Phosphate coatings have been produced by plasma-spraying hydroxyapatite (HA) and tricalcium phosphate (TCP) powders onto Ti substrates at initial temperatures of 20, 300, and 550°C, followed by hydrothermal treatment (HTT) at 650°C, and the variation in the phase composition of the coatings has been examined in relation to the phase composition of the plasma-sprayed powders: 100 wt % HA, 100 wt % α‑TCP, and 100 wt % β-TCP. The as-prepared coatings produced by plasma-spraying the HA powder consisted of 87–91 wt % HA and 9–13 wt % CaO, and after HTT their phase composition was 89–93 wt % HA and 7–11 wt % CaO. The coatings produced by plasma-spraying the α-TCP powder at initial substrate temperatures from 20 to 550°C consisted entirely of a crystalline α-TCP phase. The coatings produced by plasma-spraying the β-TCP powder consisted of both β-TCP and α-TCP, and the content of the latter phase decreased from 100 to 80% as the substrate temperature was raised from 20 to 550°C. After HTT, the coatings contained 26–28% HA, independent of the phase composition of the starting TCP powders.

The analysis of modern approaches in choosing compositions of cermets based on TiC carbide and Ni matrix doped with additional Mo, W, Cr, Nb, and Ta carbides is carried out. The hardness and transverse strength of the cermets based on TiC carbide and Ni matrix increases with the use of additional Mo, W, Cr carbides owing to the formation of an annular zone around TiC. The calculated microhardness of carbides in the cermet increases with an increase in their volume fraction and with the use of Mo, W, and Cr carbides. On the basis of an analysis of the literature, TiC–Cr₃C₂–WC–TiB₂–SiC–Mo–B–Si–Ni cermets with additional carbon content for plasma coatings are proposed and studied. Mechanical alloying and liquid phase sintering at temperatures of 950, 1250, and 1450°C are used to evenly distribute the carbides in the base phase and to establish strong bonds between them with high values of microhardness, up to 2438 kgf/mm² at a load on the indenter of 20 G and 2030 kgf/mm² at a load on the indenter of 200 G. The maximum values of microhardness are obtained at higher sintering temperatures at which the minimum content of oxygen is fixed. The positive effect of carbides based on W, Mo, and Cr on the organization of a strong titanium carbide compound with a base phase is confirmed experimentally, which is proved by the calculated value of the contribution of microhardness of TiC carbide to the cermet microhardness. At a volume fraction of the carbides of 77% and a load on the indenter of 20 G, the contribution of microhardness of the carbide is equal to 2906 kgf/mm², which is close to the TiC hardness of 3200 kgf/mm². This contribution of microhardness is equal to 2145.5 kgf/mm² at a load on the indenter of 200 G.

Five cermet coatings based on carbides 45TiC–10Cr₃C₂–5WC with different contents of additional carbon (0, 1.4, 2, and 2.8 wt %) were formed by plasma spraying with local protection. In four cermets, the matrix was based on Ni–20Cr. In one cermet, the alloy used was 38.5Co–32Ni–21Cr–8Al–0.5Y. All matrices were supplemented with Mo. Powders for spraying were obtained by crushing cakes. In the particles of the obtained powders, carbides were distributed relatively uniformly; in coatings, this was noticeable to a lesser extent. After liquid-phase sintering, WC and Mo were not fixed in cermets; part of the Cr₃C₂ carbide transformed into another structural state. The initial carbides in the cake and coating partially dissolved and, upon solidification and together with matrix elements and additional carbon, formed an annular zone around the initial TiC carbide, decreasing its lattice period. XRD fixed TiMoC₂ carbide in annular zone, the content of which was higher than the content of TiC carbide in the initial mixture. The content of the initial carbides in the coatings, measured by optical microscopy, decreased from 71 vol % in the powder to 48 vol % at the minimum plasma power and to 36 vol % at the maximum power. The average total TiMoC₂ content of carbides in coatings according to X-ray data in four cermets was 76 wt %, higher than their content in spraying powders (72 wt %) owing to higher spray hardening rates. The average microhardness for all coatings was 22.01 GPa at an indenter load of 20 gf, which was lower than the average microhardness for all powders (23.51 GPa). At an indenter load of 200 gf; the average microhardness for all coatings of 15.88 GPa corresponded to the average microhardness for all powders (15.17 GPa).