Development of heat-and impact-resistant coatings for main pipelines

We have developed composite layered temperature-resistant silicon-organic sandwich-type coatings with thin polyurethane silicon-organic interlayers. We used the following materials as binding components: KO 921 silicon-organic lacquer with addition of éD-20 epoxy resin for prime coat, the same lacquer with addition of PZ 1040 S polyurethane elastomer for thin soft interlayers, and only KO 921 lacquer for thick hard layers. The mineral filler represented a mixture of coal ash and omiacarb in proportion 70 / 30 mass %. We have manufactured and tested laboratory specimens with two hard layers and two interlayers as well as with three hard layers and two thin interlayers. We have established that the developed composite layered coatings exceed, in their basic characteristics, the requirements of the State Standard Committee of Ukraine and foreign normative documents for the rust protection of steel main pipelines. Our coatings possess high impact strength, heightened elasticity and adhesion strength and, as to their electrical insulating characteristics, exceed these requirements by an order of magnitude. We note the complexity of the technology of applying layered composite coatings and the necessity of its improvement. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 4, pp. 59–65, July–August, 2006.     

Production of conversion oxide-ceramic coatings on zirconium and titanium alloys

We consider the possibilities of surface hardening of zirconium and titanium alloys with conversion oxide-ceramic coatings. These coatings have been produced by the method of plasma-electrolytic treatment in alkaline solutions. We have established that the plasma temperature in discharge spark channels reaches (6–9) · 10³ K. The thickness of the coatings is 100 to 120 and 30 to 40 μm, and their microhardness is ∼ 800 and ∼ 1000 MPa for zirconium and titanium alloys, respectively. The functional properties of the coatings depend on the synthesis conditions, including the electrolyte composition, the cathode and anode current densities, and also the treatment time. We have evaluated the thickness, microhardness, and wear resistance of the coatings under conditions of dry friction and cavitation as well as their fatigue strength and corrosion resistance. We have established that this treatment provides a high wear and corrosion resistance of the alloys under study with insignificant decrease in their fatigue strength. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 2, pp. 117–124, March–April, 2006.     

Tribological properties of carbonitride coatings formed on titanium by thermodiffusion carbonitriding

We have studied the tribological properties of VT14 titanium alloy with carbonitride coatings formed by the contact and noncontact method and binary (oxide and nitride) coatings. In the case of the contact method, specimens are saturated in a graphite backfill, and in the case of the noncontact method, specimens are located above it. We have investigated the wear resistance of a “titanium disk–bronze block” friction pair in AMH-10 hydraulic fluid under a load to 3 MPa on a friction path to 15 km. It has been established that coatings based on ternary interstitial compounds (titanium carbonitrides) provide a higher wear resistance than that of coatings based on binary interstitial compounds (titanium nitrides and oxides).     

Fatigue characteristics of VT22 titanium alloy with wear-resistant coatings

We study the influence of wear-resistant gas-thermal plasma and ion-plasma nitride coatings, diffusive electrochemical treatment, and vacuum nitriding on the fatigue resistance of specimens made of VT22 titanium alloy. The experimental results demonstrate that the wear-resistant hard coatings decrease the fatigue limit, whereas the procedure of sand-blasting increases the fatigue resistance of the alloy. Unlike diffusive coatings, plasma coatings suffer cracking and exfoliate from the surface of titanium alloy, which reveals their insufficient adhesion and high stiffness. The obtained results are quite urgent for the aircraft industry, where the VT22 alloy is extensively used. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 6, pp. 119–122, November–December, 2006.     

Physicochemical properties of tungsten-carbide and zirconium-diboride galvanic coatings on steel

We study the physicochemical and mechanical properties of galvanic coatings based on tungsten carbide and zirconium diboride and obtained as a result of electrolysis of ionic melts on steels. The thickness of the coatings does not exceed 100 μm. The application of these coatings makes the wear resistance of steel specimens 6–9 and 8–9 times higher and their abrasion resistance 7–8 and 8–10 times higher, respectively. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 1, pp. 68–72, January–February, 2007.     

Model representation of filled polymers

We have investigated the mechanical properties and dielectric relaxation in polyamide-6 composites with fiber glass and mica. We propose a new model for filled polymers, assuming that the material consists of two interpenetrating continuous phases. The first phase is the polymer sorbed on the surface of the filler particles, mechanically stronger and having a higher modulus of elasticity. The second phase is the unsorbed polymer. The calculated mechanical characteristics of the composites (tensile strength and modulus of elasticity) agree well with experimental data. Translated from Izmeritel'naya Tekhnika, No. 8, pp. 53–56, August, 1998.     

Enhancement of the corrosion resistance of titanium alloys of the Ti-Al-Mo-V system by carbonitriding

We study the regularities of formation of coatings on titanium alloys of the Ti-Al-Mo-V system in the process of saturation in carbon-and-nitrogen-containing media (with an oxygen content of at most 0.01–0.0005 vol.%) and their corrosion-electrochemical behavior in an 80% aqueous solution of sulfuric acid. The difference between the phase compositions of the coatings formed in different temperature ranges of saturation is revealed. Thus, nitride coatings are formed on the surface at temperatures below 1100°C and carbonitride coatings are formed above 1100°C. It is shown that the physicochemical characteristics of nitride coatings formed in carbon-and-nitrogen-containing media are better than the corresponding characteristics of nitride coatings obtained by nitriding for the same temperature, time, and gas-dynamic parameters of saturation. As the content of cubic δ-nitride in the coating increases, the corrosion characteristics of the surface after saturation in carbon-and-nitrogen-containing media increase. Despite a significant surface roughness of carbonitride coatings, their corrosion resistance is high. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 4, pp. 78–83, July–August, 2006.     

Influence of hydrogen on the long-term strength of tire steels

We establish that the time to fracture of specimens made of 8Mn−8Ni−4Cr steel decreases in tap water at high stresses by a factor of 2.5 and, in the course of electrolytic hydrogenation, by a factor of 35–50 as compared with that obtained in tests in twice-distilled water. The use of a hardening surface treatment and protective coatings under the same conditions increases the long-term strength by a factor of 1.5–2. A combined plasma Al+V₂O₅ coating with subsequent soaking with epoxy compound preserves the plastic characteristics of steel and, hence, increases the time to fracture in the best way. The application of plasma nitride (TiN+CrN+NbN) coatings on the thread and mounting surfaces of elements of a rotor shroud unit gives them a high hardness and resistance to dripping and scoring and prevents the penetration of hydrogen-containing media into the base. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 4, pp. 37–42, July–August, 1999.     

Surface hardening of titanium by noncontact thermodiffusion carbonitriding

We have studied the influence of the parameters of noncontact carbonitriding on the properties of coatings and surface layers. We have shown that this method enables one to decrease the saturation temperature to 800–850°C. The temperature-time and gas-dynamic parameters of this process determine the phase and structural features of surface layers. Regulating the technological parameters of saturation, one can affect the properties of coatings. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 5, pp. 63–68, September–October, 2008.     

Dielectric properties of carbon black: SBR composites

A series of styrene–butadiene rubber (SBR) composites have been prepared with different weight ratios of polyacetylene based conducting carbon black (CCB) (0–90 phr). The SBR–CCB systems are characterized for dimensional stability which is enhanced by increasing the CCB loading because of enhancement in polymer-filler interaction. The electrical properties such as dielectric constant (ε_r), dissipation factor (tan δ) and dielectric loss (ε″) of the composites have been studied. The influence of different loading of CCB (0–90 phr), frequency of ac (100 Hz–30 MHz) and temperature (25–75 °C) on the electrical properties was studied. An increase in dielectric constant and tan δ of the SBR composites was observed with increase in CCB content and ac frequency. This is due to enhancement of filler–filler interaction and the increase in continuity of conducting phase. The surface morphology has been studied using scanning electron microscopy (SEM).     

Characteristics of organosilicon urethane composite materials and coatings

We study the principles of modification of organosilicon materials aimed at improving their physicomechanical, engineering, and operating parameters. The efficiency of application of viscous-flow polyurethane compositions as modifiers is demonstrated. We analyze the structural, physicomechanical, and dielectric characteristics of the polyurethane elastomers, organosilicon urethane composites, and anticorrosive coatings based on these compounds. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 6, pp. 62–66, November–December, 2007.     

Effect of Carbon-Containing Conducting Fillers on the Properties of Epoxy Coatings

We have established that antistatic coatings based on EP-0010 putty and graphite have low adhesion to metal and breaking strength but are resistant to the action of an operating environment. The use of carbon black as a conducting additive increases 1.5–3 times the strength of free films obtained on the basis of the given epoxy composition as compared with graphite and decreases their mass losses in an operating environment. The adhesion of epoxy coatings based on the EP-0010 composition modified by carbon black is 2–2.5 times as great as that of coatings with a graphite filler. The use of a plasticizer based on epoxidated vegetable oil instead of an inert phthalate plasticizer in a carbon-containing epoxy composition is promising and, in the case of optimal content of the components, enables one to enhance significantly the physicomechanical characteristics of antistatic epoxy coatings and their resistance to the action of the operating environment. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 2, pp. 109–113, March–April, 2005.     

Effect of coatings on the distribution of heat in bar-disk tribosystems

We develop an analytic method for the evaluation of the surface temperature and the coefficient of distribution of heat in a tribosystem formed by an immobile bar and a rapidly rotating disk with coating. The analysis of numerical results demonstrates that surface temperature increases with the thickness of the coatings if the thermal conductivity of the coating is lower than the thermal conductivity of the disk. For coatings of fixed thickness, surface temperature decreases as the angular velocity increases. We also study the dependences of the coefficient of distribution of heat between the bodies on their geometric parameters and thermal properties. Franko L'viv University, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 3, pp. 43–49, May–June, 1997.     

Separation of germanium and silicon oxides by plasma-chemical deposition of germanosilicate glass in a moving plasma column

The optical transmission spectrum of germanosilicate glass deposited by surface plasma chemical vapor deposition on the inner surface of a quartz tube revealed interference resonances typical of multilayer dielectric coatings with alternating refractive indices. It is shown that this effect can be attributed to the longitudinal inhomogeneity of the plasma composition and specifically to an axial shift of the concentration maxima of germanium and silicon oxide. As a plasma having a nonuniform composition moves along the tube, a layer of glass is formed with a strong transverse germanium concentration gradient. It is established that in surface plasma chemical vapor deposition the axial separation of the regions of deposition of the silicon and germanium oxides increases if the glass is synthesized under conditions of oxygen deficiency. Pis’ma Zh. Tekh. Fiz. 25, 55–61 (July 12, 1999)     

Electrode for measuring ohmic and impedance characteristics of protective coatings of pipelines

We propose a mobile electrode of original design for measuring the ohmic and impedance characteristics of protective coatings on pipes of diameter 57 to 1420 mm under laboratory and field conditions. The electrode was calibrated on plane specimens with respect to measurements of the transient ohmic resistance by the method of “hollow cylinders.” We present the results of measurements of the transient ohmic resistance of identical coatings on plane specimens and pipes of different diameters as well as the values of relative errors. A good agreement between the results of investigations is shown. Owing to the original design of the working chamber and magnetospring hold-down device, the electrode can be used for the survey of inclined, wall, and ceiling surfaces of steel structures. As a result, we conclude that it is expedient to introduce this electrode into the State Standard. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 5, pp. 98–102, September–October, 2006.     

Calculation of the radiation-induced conduction current in dielectrics irradiated with high-energy electrons and protons having a two-component maxwellian distribution

A method is considered for calculating the distributions of the space-charge field and of the radiation-induced conduction current over the thickness of dielectric coatings, and of the potential of their open surface corrected for the space-charge field, during interactions with electrons and protons. This method is used to consider these quantities for a two-component Maxwellian distribution of the charged particles. The optimal thickness of coatings on artificial sttellites is also determined. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 6–12, November, 1998.     

Dielectric properties of carbon black and carbonyl iron filled epoxy–silicone resin coating

The dielectric properties of epoxy–silicone resin coatings containing carbon black (CB) and carbonyl iron (CI) particles as a function of frequency (2–18 GHz) and the CB volume content (0.2–1%) have been investigated. The complex permittivity of the coatings increased with increasing CB content, which mainly attributed to the interfacial polarization at the CB/resin/CI particles interfaces. The complex permittivity also decreased rapidly with increasing frequency in the low frequency range while decreased slowly in the high frequency range. The changes of dielectric properties with frequency and the CB volume content were discussed using the power-law decay and the concept of interfacial polarization.     

Cavitation resistance of modified surface layers of alloyed steels

The cavitation strength of 15Kh11MF and 15Kh12VNMF steels after nitriding and deposition of vacuum arc titanium and titanium nitride coatings is investigated. Kinetic curves of fracture of specimens under the action of cavitation and polarization curves in a 3% aqueous solution of NaCl are obtained, and the microhardness is measured. A steel–coatings system is thermocycled by the scheme 293 K–543 K–293 K with cooling in a 3% NaCl solution. The serviceability of the system is confirmed.     

Doped barium titanate nanoparticles

We have synthesized nickel (Ni) and iron (Fe) ion doped BaTiO₃ nanoparticles through a chemical route using polyvinyl alcohol (PVA). The concentration of dopant varies from 0 to 2 mole% in the specimens. The results from X-ray diffractograms and transmission electron micrographs show that the particle diameters in the specimen lie in the range 24–40 nm. It is seen that the dielectric permittivity in doped specimens is enhanced by an order of magnitude compared to undoped barium titanate ceramics. The dielectric permittivity shows maxima at 0.3 mole% doping of Fe ion and 0.6 mole% of Ni ion. The unusual dielectric behaviour of the specimens is explained in terms of the change in crystalline structure of the specimens.     

Discontinuous coatings on cutting tools

To increase the life of cutting tools, it is proposed to form wear-resistant discontinuous coatings on their surface. In order to ensure cohesive strength of coating, coating crack spacing is taken as the size of discrete portion. It has been shown that under contact loading conditions, such coatings prevent contact fracture thanks to reduction of residual stresses. __________ Translated from Problemy Prochnosti, No. 1, pp. 138–143, January–February, 2007. Report on International Conference “Dynamics, Strength, and Life of Machines and Structures” (1–4 November 2005, Kiev, Ukraine).