A. O. Volkhonskii

Properties of nanostructured TiN-Ni ceramic-metal coatings obtained by ion-plasma vacuum-arc method

Physicomechanical and tribological properties of TiN-Ni ceramic-metal coatings prepared by ion-plasma vacuum-arc deposition are investigated. It is established that the hardness (H) increases from 23 to 54 GPa with the Ni content from 0 to 12 at %, which is determined by the influence of the nanostructured nitride component of coatings. Coefficients HE−1 and H3E−2, which characterize the material resistance against the elastic and plastic failure deformation, reach 0.104 and 0.567 GPa, respectively. The further increase in the nickel concentration in coatings to 26 at % leads to a decrease in H to 23–25 GPa, which is associated with the influence of the increasing amount of soft plastic metal and the formation of noticeable porosity in the bulk of coatings. The friction coefficient of studied coatings is 0.45, against 0.58 (for the TiN coating) and 0.72 (for the hard-alloy base). The cohesion failure mechanism of TiN-Ni nanostructured coatings (CNi = 2.8–12 at %) is established, and critical loads which characterize the appearance of the first crack (13.5–14.2 N) and the local coating attrition up to the substrate (61.9–64.4 N) are determined. The complete attrition of coatings does not occur up to a load of 90 N, which points to their high adhesion strength. The developed nanostructured ceramic-metal coatings are characterized by high heat resistance up to 800°C.

Influence of deposition parameters of the Ti-Al-N/Zr-Nb-N-Cr-N multilayered nanostructured coating obtained by the arc-PVD method on their physicomechanical, tribological, and operational properties

Physicomechanical, tribological, and operational properties of the Ti-Al-N/Zr-Nb-N-Cr-N multilayered coatings obtained by the arc-PVD method are investigated. Dependences between the controlled deposition parameters (the bias potential across the substrate and the revolution rate of the sample relative to sputtered cathodes) and the characteristics of the coatings having hardness up to 37 GPa and adhesion strength of over 100 N are established. Comparative investigations into the tribological properties of multilayered coatings of various compositions showed that the developed coatings are characteristic of the lowest friction factor. A cutting tool with such coatings possesses high resistance properties in conditions of the interrupted and continuous cutting of gray cast iron (SCh30) and steels (St. 45, X18H10T).

Phase composition, structure, and mechanical properties of arc PVD Mo–Si–Al and Mo–Si–Al–N coatings

Using an arc physical vapor deposition process, we have produced nanostructured Mo–Si–Al coatings with a uniform distribution of equiaxed grains 8–12 nm in size and Mo–Si–Al–N coatings with a multilayer structure and a modulation period from 22 to 25 nm. The former coatings consist of MoSi2 and Mo and the latter consist of Mo2N and amorphous Si3N4 and AlN. The hardness of the Mo–Si–Al–N and Mo–Si–Al coatings is 41 and 18 GPa, respectively; they are similar in resistance to elastic deformation; and the Mo–Si–Al–N coating has a considerably higher resistance to plastic deformation. The coatings have roughly identical coefficients of friction (~0.67–0.69 at 20°C and ~0.52–0.56 at 550°C), but the wear resistance of the Mo–Si–Al–N coating is higher by three and two orders of magnitude at 20 and 550°C, respectively. The coatings of the two systems exhibit good adhesion to the substrate and cohesive fracture. Partial wear of the Mo–Si–Al and Mo–Si–Al–N coatings in the course of scratch testing occurs at indentation loads of 80 and 63 N, respectively.

Phase formation in the Ti–Al–Mo–N system during the growth of adaptive wear-resistant coatings by arc PVD

Ti–Al–Mo–N coatings have been grown by arc PVD at different bias voltages, Vb, applied to the substrate and partial pressures of nitrogen reaction gas, p(N2), in the working chamber. The coatings have a nanocrystalline structure, with an average grain size on the order of 30–40 nm and a layered architecture made up of alternating layers based on a (Ti,Al)N nitride and Mo-containing phases of thickness comparable to the grain size. It has been shown that the phase composition of the coatings depends on Vb and p(N2): raising the energy of deposited ions by increasing Vb from–120 to–140 V, as well as raising p(N2) from 0.3 to 0.5 Pa, leads to a more complete molybdenum nitride formation during coating growth, which causes a transition from (Ti,Al)N–Mo–Mo2N compositions to (Ti,Al)N–Mo2N. Measurements of the binding energy of Mo 3d photoelectrons in metallic Mo and the Mo2N nitride by X-ray photoelectron spectroscopy have shown that the transition from the former phase to the latter is accompanied by a negligible energy shift.

Thermal stability, heat resistivity, and electrochemical corrosion resistance of (Ti,Al)N-Cu nanostructural coatings

Nanostructural ceramometallic ion-plasma vacuum-arc (Ti,Al)N-Cu coatings with Al content on the order of 1.5 at % and 3 at % Cu with the crystallite size of 15–20 nm and a thickness of 4 μm on the solid solution are characterized by heat resistance and thermal stability till 700°C. The presence of copper atoms in the coating leads to a slight increase in the density of the passive state current relatively the (Ti,Al)N ceramic coating, but it exerts no significant influence on the electrochemical behavior of the 3 at % (Ti,Al)N-Cu system in highly oxidized chloride solution. The studied coatings are different by a high tendency to self-passivation, low passive state current densities and high resistance to the pitting corrosion that almost does not occur because of the fast transition from the pitting origin into its repassivation. As in the acid condition, the composite exhibits a high electrochemical stability in the alkaline medium, being in the passive state.

Ceramic-metallic (TiN-Cu) nanostructured ion-plasma vacuum-arc coatings for cutting hard-alloy tools

The structure and properties of TiN-Cu coatings with a broad range of copper concentrations (CCu = 0.6–20 at %), which were fabricated by the ion-plasma vacuum-arc deposition on a TT10K8B hard-alloy tool, including its cutting resistant tests, were investigated. The introduction of copper into the coating composition diminishes crystallites of the nitride phase from 100 to 20 nm. The hardness of coatings increases from 20 to 40 GPa, with an increase in CCu to 7–8%. The further increase in the copper content, which is accompanied by diminishing crystallites of the nitride phase, is characterized by a decrease in hardness to 14–15 GPa, which is associated with the influence of soft plastic metal. Resistant cutting tests of steel 35KhGSA of removable multifaceted plates (RMP) with the TiN-Cu coatings indicate that the optimally selected composition (TiN-7-8 at % Cu) increases RMP resistance more than by a factor of 6 and 2.5 as compared with tools without the coating and with the TiN coating deposited according to the basic technology, respectively.

(Ti,Al)N–Ni nanostructured coatings: Thermal stability, heat resistance, electrochemical behavior, and adhesive strength with a substrate

In this work, thermal stability and oxidation resistance at temperatures up to 800°C are studied for (Ti,Al)N–(8–10 at %)Ni coatings with a thickness on the order of 4 µm and a crystallite size below 20 nm, which have been prepared via ion–plasma vacuum arc deposition. The composition and structural characteristics of coatings remain stable during 1-h heating in vacuum of 10–4 Pa at temperatures of 600 and 700°C. Heating at a temperature of 800°C leads to an increase in the crystallite size and a decrease in microstrains of a ceramic phase, which is accompanied by a reduction in the hardness of the coating from 51–53 to 31–33 GPa. The coatings are heat resistant up to 800°C and characterized by cohesive failure in scribing. The adhesive strength of coatings with a substrate exceeds 85 N. Studying electrochemical behavior reveals the high efficiency of (Ti,Al)N0.87–Ni coatings in corrosion protection of cutting tools in acid and alkaline environments.

Structure of nanocrystalline arc-PVD (Ti, Al)N coatings modified with nickel

The introduction of nickel into the composition of ion-plasma vacuum-arc (Ti, Al)N coatings refines nitride-phase crystallites from 100–120 to 15–18 nm when the nickel content is varied from zero to 12 at %. The size of nitride blocks is in agreement with that of ceramic-phase grains. Some (Ti, Al)N grains grow with the nickel content up to 30–35 nm. The structure changes from columnar to equiaxed during modifying the (Ti, Al)N coatings with nickel. Nickel in a coating is in an amorphous state (detected by X-ray diffraction) when its content is no more than 12–13 at %. A further increase in its content leads to the formation of the TiNi intermetallic compound, which results in structure porosity in the deposited coating. A transition zone forms at the boundary between a (Ti, Al)N–Ni coating and the VK6-alloy substrate, which is characterized by an element concentration gradient from the coating to the substrate and vice versa.

Structurization and phase formation in the course of preparing nanocomposite TiN–Ni ion-plasma vacuum–arc coatings and their thermal stability

Structure and phase formation in the course of fabricating composite ion–plasma vacuum-arc nanocrystalline TiN–Ni coatings are investigated in a broad range of nickel concentrations (from 0 to 26 at %). It is established that the introduction of Ni into the coating composition refines the nitride phase crystallites. The arithmetic mean size of TiN grains decreases from 100–120 to 15–18 nm upon varying the Ni concentration from 0 to 12 at % and normal particle-size distribution. The further increase in the Ni content is accompanied by the transition to the polymodal particle distribution with an increase in their arithmetic mean diameter to 27 nm for the third mode. Nickel in coatings at a concentration of 12–13 at % Ni is in the X-ray amorphous state. As the concentration increases above 13 at %, the TiNi intermetallic compound is formed in the composition of coatings. This phenomenon in turn causes the appearance of porosity in the structure of the deposited layer. The blocking role of nickel simultaneously weakens with the formation of the intermetallic compound, which manifests itself in the growth of separate TiN grains to 30–35 nm. The TiN–Ni coatings are characterized by the thermal stability of the structure and composition upon heating to 800°C.

The effect of deposition parameters of multilayered nanostructure Ti-Al-N/Zr-Nb-N/Cr-N coatings obtained by the arc-PVD method on their structure and composition

The structure and elemental and phase compositions of the Ti-Al-N/Zr-Nb-N/Cr-N multi-layered coatings obtained by the arc-PVD method are investigated. A three-cathode sputtering system including the Ti-Al, Zr-Nb, and Cr cathodes was used for their deposition. The controlled parameters of the process were the rotation speed of coated samples relative to sputtered cathodes, the current of the sputtering arc on the zirconium-niobium cathode, and the negative electric bias potential supplied to the substrate. These parameters varied within the limits from 1 to 3 rpm, from 135 to 170 A, and from −80 to −160 V, respectively. The possibility of forming multilayered coatings with a thickness of single layers at a level of ∼10 nm and their transfer from a multilayered structure to a single-layered one due to the variation in the deposition parameters is shown. The parametric dependences of the controlled parameters of the formation of coatings on their composition and structure components are found.