Hardness,adhesion strength,and tribological properties of adaptive nanostructured ion-plasma vacuum-arc coatings (Ti,Al)N–Mo<Subscript>2</Subscript>N

The properties of nanostructured multilayered coatings of the composition (Ti,Al)N–Mo₂N, which were fabricated by the ion-plasma vacuum-arc deposition (arc-PVD), are investigated. The thickness of coating layers is comparable with the grain size, which is about 30–50 nm. The coating hardness reaches 40 GPa with relative plastic deformation work of about 60%. It is established by measuring scratching that the cohesion destruction character of the coating occurs exclusively according to the plastic deformation mechanism, which evidences its high fracture toughness. The local coating attrition to the substrate takes place under a load on the order of 75 N. The coating friction coefficient in testing conditions according to the “pin-on-disc” layout using the Al₂O₃ counterbody under a load of 5 N is 0.35 and 0.50 at temperatures of 20 and 500°C, respectively. The coating is almost unworn because of the formation of MoO₃ oxide (the Magneli phase) operating as the solid lubricant in the friction zone. An increase in the friction coefficient and noticeable wear are observed with the further increase in the testing temperature, which is associated with the sublimation intensification of MoO₃ from the working surfaces and lowering its operational efficiency as the lubricant.     

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 (C _Cu = 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 C _Cu 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.     

Evaluation of Thermal Stability of Multilayered Nanostructured Coatings Based on Analysis of Diffusion Mobility of Components of the Layers

The thermal stability of multilayered nanostructured coatings is evaluated by analyzing the diffusion mobility of layer components. The possibility of increasing the thermal stability of multilayered coatings based on mutually soluble Ti–Al–N and Cr–N layers due to the introduction of an additional barrier layer based on Zr–N into a multilayered nanostructure is investigated in detail. Calculated diffusivities of basic metallic elements of the coating into corresponding nitride layers upon heating in a temperature range of 800–1000°C evidence the absence of noticeable diffusion spread of layer boundaries in the presence of the Zr–N-based barrier layer. For example, their values lower upon its introduction (it is found at t = 1000°C, cm²/s: D_Cr/TiN = 5 × 10^–17, D_cr/ZrN = 2 × 10¹⁸, \({D_{Ti/C{r_2}N}}\) = 9 × 10^–18, and D_Ti/ZrN = 3 × 10^–18). The physicomechanical properties of coatings do not vary upon their vacuum annealing at t < 900°C; however, they noticeably lower with a further increase in temperature due to the degradation of a multilayered coating structure during annealing.     

Fabrication of vacuum-arc Ti-Al-N coatings using multicomponent SHS-compacted cathodes

The results of experiments on the deposition of vacuum-arc Ti-Al-N coatings using aluminum-containing pressed cathodes based on nonstoichiometric titanium carbide TC_0.5 are presented. The composition and morphology of coatings are investigated using electron probe microanalysis and scanning electron microscopy. Hardness and elasticity modulus were determined using the nanoindentation method. It is established that carbon is absent in the coating, while the fraction of aluminum in it decreases compared with its content in the cathode material. A superhard coating with nanohardness H = 59 GPa and the Young modulus E = 475 GPa is obtained from the cathode with the calculated composition TiC_0.5-30%Al. By the ratio of hardness to the elasticity modulus, which equals H/E = 0.124, this coating is an amorphous-crystalline material. When using cathodes based on refractory nonstoichiometric titanium carbide, the content of the drop phase in coatings substantially lowers with no separation of the plasma flow. In general, the application of multicomponent SHS-compacted cathodes based on nonstoichiometric titanium carbide TiC_0.5 makes it possible to fabricate superhard nanocrystalline coatings according to the standard technology using a serial vacuum-arc installation.     

Wear-resistant Ti-Al-Si-C-N coatings produced by magnetron sputtering of SHS targets

The results of an investigation into hard wear-resistant nanostructured coatings in the Ti-Al-Si-C-N system produced by the magnetron sputtering of multicomponent composite targets with various ratios of metallic and nonmetallic elements are presented. Coatings are deposited in the reaction gas mixture with constant values of the substrate temperature and bias voltage. The structure of coatings is investigated using X-ray diffraction, glow-discharge optical emission spectroscopy, scanning and transmission electron microscopy. The mechanical and tribological properties are determined using the nanoindentation and scratch-testing methods, as well as using tribological tests according to the “pin-on-disc” scheme. The results of investigations show that the coatings are based on the fcc phase consisted of titanium carbonitride with an average crystallite size of 2–20 nm; the crystallites are arranged in an amorphous matrix. The coatings of optimal composition possess hardness of 40–50 GPa, a stable friction coefficient of <0.55, an adhesion strength of ≥50 N, and a wear rate of <1 × 10^?5 mm³/(N m).     

Physicomechanical and exploitation properties of nanostructured wear-resistant ion-plasma vacuum-arc coatings on the basis of multicomponent nitrides

This work is devoted to an investigation of the hardness (H), modulus of elasticity (E), and adhesion-cohesion strength of ion-plasma vacuum-arc coatings of the Ti-Cr-Al-N system. It is shown that the magnitudes of H and E are determined by the crystallite size and microdeformation level. The maximum values of hardness (up to 32 GPa) and modulus of elasticity (up to 700 GPa) correspond to coatings with a minimal crystallite size and maximal magnitude of microdeformatons. Wear of coatings is accompanied by the cohesion destruction. The adhesion strength of coatings is evaluated at about 90 N. The resistance of the cutting hard-alloy tool with coatings for the continuous and interrupted cutting of 38XHMA steel has been increased by a factor of 5.1 and 5.7, respectively.     

不同过渡层对CrCN涂层性能的影响

利用多弧离子镀技术,以乙炔和氮气为反应气体,在316 L不锈钢和单晶硅基体上设计3种不同的过渡层（无过渡层,Cr,CrN）制备CrCN涂层,通过X射线衍射仪（XRD）、扫描电镜（SEM）、纳米压痕仪、CSM划痕测试仪和UMT-3多功能摩擦磨损试验机等对3种涂层的微观结构、力学性能和摩擦学性能进行表征.结果表明： CrCN,Cr/CrCN及CrN/CrCN涂层的平均表面粗糙度分别为77.3 nm,74.5 nm及68.1 nm,整体表现出递减的趋势.CrCN,Cr/CrCN及CrN/CrCN涂层的结合力和硬度分别为20.5 N,43 N,61 N及17.4 GPa,21.4 GPa,24.1 GPa.较之于单层CrCN涂层, CrN/CrCN复合涂层的硬度及结合力提高最为显著,并对CrCN涂层起到强有力的支撑作用,从而在大气、去离子水、海水环境下表现出较低的摩擦系数及磨损率.     

Nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings for hard-alloy cutting tools

Nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings with various contents of chromium and nitrogen are obtained by the magnetron sputtering of multiphase composite targets. Their structure and phase composition are investigated by X-ray phase analysis, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and optical emission glow-discharge spectroscopy. The Ti-Cr-B-N and Ti-Cr-Si-C-N coatings are based on the fcc phase with texture (100) and crystallite size <25 nm. The Si₃N₄-based hexagonal phase was also revealed in the Ti-Cr-Si-C-N coatings. An investigation into the properties of coatings with the use of methods of nanoindentation, scratch testing, and by performing tribological tests showed that they have a hardness of up to 30 GPa, an adhesion strength no lower than 35 N, and their friction coefficient falls in the range of 0.35–0.57. Coatings also possess high thermal stability, resistance to oxidation, and corrosion stability in a 1N H₂SO₄ solution. The data obtained in tests of hard-alloy cutting tools indicate that the deposition of nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings increases its resistance by a factor of 11–17.     

Structure, mechanical and erosive properties of AlN-MoSi2 composite materials and their electrospark-deposited coatings

The paper examines the phase composition, structure, and properties of AlN-MoSi₂ alloys and associated electrospark-deposited coatings on titanium. It is shown that the most intensive erosion and mass transfer are characteristic of alloys containing 60–80 wt.% MoSi₂ and that the erosive characteristics essentially depend on the electrospark treatment parameters. A protective coating with a thickness of 30–40 µm and hardness to 1 GPa is formed on the substrate. There is a thermal impact area up to 300 µm deep and 1.4 GPa hard under the coating. The high-temperature holding of coated samples promotes the rapid formation of heat-resistance phases in the coating and the formation of a secondary structure in the thermal impact area. As a result, this area becomes thicker and the hardness of its material increases up to 1.9 GPa.     

Nanostructured Arc-PVD coatings based on titanium and chromium nitrides

Multicomponent nanostructured coatings based on Ti-Cr-Al-N nitrides with a crystallite size of 10?C100 nm are formed by arc physical vacuum deposition. The dependences of the structure and phase composition of the coatings on the deposition parameters, namely, the bias potential applied to a substrate and the arc current at a chromium cathode, are found. The appearance of chromium nitride phases in the coatings is accompanied by a decrease in the crystallite size. The hardness (up to 32 GPa) and the elastic modulus (up to 700 GPa) of the coatings are determined by both the crystallite size and the microstrains (up to 0.74%) induced by chemical heterogeneity in the coatings. The adhesion strength of the coatings is estimated at 90 N. Cutting hard-alloy tools with the grown coatings are characterized by a high resistance coefficient during continuous (up to 5.1) and discontinuous (up to 5.7) cutting of 38KhNMA steel.     

Correlation of microstructure and wear resistance of Al2O3-TiO2 coatings plasma sprayed with nanopowders

Correlation of microstructure and wear resistance of Al₂O₃-TiO₂ coatings plasma sprayed with nanopowders was investigated in this study. Four kinds of nanostructured Al₂O₃-13 wt pct TiO₂ coatings were fabricated by varying plasma-spraying parameters and were compared with an Al₂O₃-13 wt pct TiO₂ coating fabricated with conventional powders. The nanostructured coatings showed a bimodal microstructure composed of fully melted regions of γ-Al₂O₃ and partially melted regions, while the conventional coating mostly consisted of fully melted γ-Al₂O₃, together with some TiO₂-rich regions and unmelted Al₂O₃ powders. The wear test results revealed that the wear resistance of the nanostructured coatings was 3 or 4 times better than that of the conventional coating, because the preferential delamination seriously occurred along TiO₂-rich regions in the conventional coating. In the nanostructured coatings, TiO₂ was homogeneously dispersed inside splats and around, thereby leading to higher splat bonding strength and to better wear resistance over the conventional coating.     

Synthesis of nanostructured Cr3C2-25(Ni20Cr) coatings

On the basis of the nanocrystalline Cr₃C₂-25 (Ni20Cr) feedstock powders produced by mechanical milling, a nanostructured coating has been synthesized using high velocity oxygen fuel (HVOF) thermal spraying. The properties of the nanostructured coating were compared to those of the conventional coating of the same composition using scanning electron microscope (SEM), transmission electron microscope (TEM), and microhardness tests. The nanostructured Cr₃C₂-25 (Ni20Cr) coating synthesized in this study had an average carbide particle size of 24 nm. Discontinuous elongated amorphous phases were observed in the nanostructured coating. The conventional Cr₃C₂-25 (Ni20Cr) coatings produced using blended elemental powders exhibited an inhomogeneous microstructure. The observed homogeneity of the nanostructured coating is attributed, in part, to the microstructural improvement of the starting powder. The nanostructured Cr₃C₂-25 (Ni20Cr) coating yielded an average microhardness value of 1020 DPH₃₀₀, which corresponds to a 20 pct increase in microhardness over that of the conventional coating. The nanostructured Cr₃C₂-25 (Ni20Cr) coating also exhibited a higher apparent fracture toughness relative to that of the conventional coating. The apparent mechanical property improvements in the nanostructured coating were thought to result from the uniformity of the microstructure and the high performance associated with a nanostructured structure. In addition, the mechanism that is present during the milling of a system containing nondeformable particles is discussed in light of the TEM observations.     

Corrosion resistance of cermets based on titanium nitride

Conclusions The corrosion resistance of the cermets based on TiN with (Ni, Mo, Cr)-binder containing 10–15% Cr, is higher than that of KKhN-15 alloy and MNTs-20 German silver in solutions of acids: 5% HCl, 7% HNO₃ and 10% H₂SO₄.The resistance of the cermets based on titanium nitride is 5% HC1 decreases in the sequence: TiN-Cr > TiN-Ni, Mo, Cr > TiN > TiN-Ni, Cr > TiN-Ni, Mo > TiN-Ni.The corrosion resistance of the TiN-Cr cermets is slightly higher than the resistance of TiN. This is associated with the formation of the double nitride (Ti, Cr)N.Alloying theTiN-(Ni, Mo) cermet with 10–15% chrome results in high corrosion resistance and satisfactory physicomechanical properties.The corrosion resistance of the alloys with a high binder content (>25%) decreases as a result of its preferential dissolution which leads to separation of the titanium nitride grains. In addition to selective dissolution of nickel and molybdenum, the corrosion process in these alloys is also determined by dissolution of chrome.Translated from Poroshkovaya Metallurgiya, No. 1(337), pp. 77–81, January, 1991.     

Preparation and control mechanism of anisotropic Sm-Pr-Co/Co nanocomposites with unusual continuous soft-phase coatings

To produce nanocomposite materials with high magnetic properties, studies concerning nanostructural processing technologies and control mechanisms are urgently required in aspects of achieving perfect alignment of the hard phase while keeping desired sizes and distributions of the soft phase. In the present study, a designed low-rate electroless deposition method is found to be an effective way in producing strong textured anisotropic Sm-Pr-Co/Co nanocomposites with unusual continuous soft-phase coatings when assembling Co particles on the ball-milled anisotropic Sm-Pr-Co hard phase. The average particle size of the soft-phase coatings is 18–50 nm and the obtained Sm-Pr-Co/Co composites exhibit a high intrinsic coercivity of H_ci = 748 kA/m with an enhanced remanence of M_r = 79 A·m²/g, as compared to H_ci = 836 kA/m and M_r = 68 A·m²/kg for uncoated Sm-Pr-Co hard phase. Moreover, the coating process study reveals a nucleation control mechanism for the formation of the continuous coating structures. Down-sized Sm-Pr-Co/Co nanocomposites with tailored size below 300 nm or even below 100 nm were also produced by this designed method. This study is of theoretical and practical importance for developing advanced nanostructures including the next generation permanent magnets.     

Microstructure and Mechanical Properties of Yttria-Stabilized Zirconia Coatings Produced by Eletrophoretic Deposition and Microwave Sintering

Y₂O₃-stabilized zirconia coatings were deposited on superalloy K17 substrates at room temperature by the eletrophoretic deposition technique followed by two different sintering methods. Scanning electron microscopy, X-ray diffraction (XRD), and nanoindentation techniques were employed to characterize morphological, structural, and mechanical properties of the coatings. Finer and more uniform microstructures were observed in the microwave sintered coatings. For the conventionally sintered coatings, the monoclinic phase was observed. The microwave sintered coatings of Y₂O₃-stabilized zirconia contain mainly cubic/tetragonal phases with some metastable phase present. In comparison with the hardness of 3.1 GPa and elastic modulus of 83.5 GPa for conventional sintered coating, the hardness and elastic modulus for microwave sintered coating rapidly increased to 4.3 and 172.7 GPa, respectively. Such coatings have potential in being used as thermal barrier coatings (TBCs) on superalloy substrates.     

Wear-resistant P/M titanium carbide - iron coatings

Conclusions In thw work described the electric contact sinter-bonding process was employed for applying, to type 45 steel, TiC-iron composite coatings exhibiting high hardness (up to 550 HV), low porosity (0.45%), and good adhesion to their bases (up to 12 · 10⁷ N/m²). The abrasive wear resistance of the materials of these coatings proved to be twice as high as that of quenched type 45 steel. The electric contact s inter-bonding method of application of coatings enables uncomminuted coarse powders to be employed and ensures high rates of coating application (the optimum sinter-bonding time is 0.16–0.18 sec, the weight rate of coating application being 5 kg/h). Coatings applied by the electric contact sinter-bonding method can be employed for building up worn surfaces of components of, e.g., agricultural machines.Translated from Poroshkovaya Metallurgiya, No. 11(215), pp. 39–42, November, 1980.     

Structure and properties of thin ceramic coatings in the system AlN-TiCrB2

The structure, composition and properties of coatings on Si, Al₂O₃ and GaAs single crystals prepared by radio-frequency magnetron sputtering of a AlN-TiCrB₂ target prepared by powder metallurgy are studied. Coating phase composition is different from that of the target material due to oxidation of aluminum nitride and its dissociation under ion bombardment conditions. The coatings have a very fine structure and marked resistance to high-temperature oxidation due to formation of solid solutions in the systems Al₂O₃-TiO₂-Cr₂O₃ and Al₂O₃-B₂O₃. The increase in mass of the target material at 1300°C is 1.4 mg/cm². After high-temperature oxidation the reinforced fine structure of the coating forms as interwoven Al₂O₃ fibers. Coatings of (AlN-TiCrB₂)-Al₂O₃ and (AlN-TiCrB₂)-GaAs are thermally stable up to 900°C and have a high microhardness (H _μ) and crack resistance (K_Ic = 4.7–3.3 MN/m^3/2). With an increase in annealing temperature (T ≥ 1000°C) coating mechanical properties worsen, but their adhesive strength increases. The AlN-TiCrB₂ target material may be recommended for preparing wear-and corrosion-resistant coatings on tools, and also on critical components operating under extreme conditions. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(449), pp. 39–47, May–June, 2006.     

Improving the Corrosion Resistance of the Nickel–Tungsten Alloy by Optimization of the Electroplating Conditions

Nickel–tungsten (Ni–W) alloy coating was electrodeposited on the copper substrate by direct current voltammetry. The optimization of a free-ammonium bath for electrodeposition of Ni–W alloy coating was investigated. Experiments were focused on elucidating the effect of W concentration and operating conditions on the corrosion performance of the obtained Ni–W alloy coating. The corrosion behavior of the coatings was investigated by potentiodynamic polarization (Tafel) test. Experimental data such as corrosion current density, corrosion rate and polarization resistance indicated that the operating conditions used during the electroplating had significant effects on the corrosion parameters of the Ni–W alloy coating. The results showed that the highest corrosion resistance was obtained for the coating with 56.7 wt% tungsten (Ni/W ratio of 1:2.5) which was prepared at the current density of 3.8 A dm^?2. The increase in the corrosion resistance at the optimum current density was attributed to the lower interferences of the hydrogen evolution reaction. Energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) techniques were used to characterize the electrodeposited Ni–W alloy with the best anti-corrosion parameters.

     

Hard plasma chemical coatings based on silicon carbon nitride

Silicon carbon nitride (SiCN) coatings deposited on a silicon substrate are produced by plasma-enhanced chemical vapor deposition (PECVD) using methyltrichlorosilane (MTCS), nitrogen, and hydrogen as starting materials. The coatings are characterized with AFM, XRD, and FTIR. Their mechanical properties are determined with nanoindentation. The abrasion wear resistance is examined using a ball-on-plane (calowear) test and adhesion to the base using a scratch test. The x-ray diffraction indicates that the coatings produced at moderate F_N are nanostructured and represent β-C₃N₄ crystallites embedded into the amorphous a-SiCN matrix. The coatings deposited at a higher nitrogen flow rate are amorphous. The nanostructure is supposed to result from an increase in hardness (25 GPa) and Young’s modulus (above 200 GPa). The tribological tests have revealed that the friction coefficients of the coatings containing nitrogen are two to three times smaller than those based on SiC and deposited on a silicon substrate. The ball-on-plane tests show that the nanostructured coatings also exhibit the highest abrasive wear resistance. These findings demonstrate that the SiCN films deposited using MTCS show good mechanical and tribological properties and can be used as wear-resistant coatings.     

Effect of coating modification of cordierite carrier on catalytic performance of supported NiMnO3 catalysts for VOCs combustion

NiMnO_3 perovskite catalysts supported on cordierite modified by Ce_xZr_(1-x)O_2 coatings were prepared using impregnation and sol-gel methods for catalytic combustion of single/double component VOCs at different concentrations and GHSV of 15,000 h~(-1), which were characterized by BET, XRD, SEM, FT-IR, H_2-TPR and O_2-TPD. After coating modification, the specific surface area of catalysts is improved obviously.Among the catalysts, the Ce_(0.75)Zr_(0.25)O_2 coating modified NiMnO_3 catalyst exhibits the best catalytic activity for VOCs combustion with 95.6% conversion at 275 ℃ and has stable activity when catalyst is embalmed at 800 ℃. In addition, the catalyst also presents the excellent water-resistant and conversion stability over time-on-stream condition. The reason is that Ce_(0.75)Zr_(0.25)O_2 coating can promote more lattice distortion and defects and smaller crystal size, which improve oxygen transfer capability and dispersion of active component.