Wear resistance of eutectic coatings of the Fe–Mn–C–B system alloyed with Si,Ni, and Cr

We analyze the wear resistance, structures, and compositions of eutectic coatings of the Fe–Mn–C–B system alloyed with Si, Ni, and Cr and obtained on 45 steel by the methods of electric-arc and plasma spraying performed by using eutectic powder wires. The process of wear of eutectic coatings is accompanied by the intense diffusion processes leading to segregation and, hence, to the increase in the C, B, and Si contents on the friction surface. Boron and silicon form nonstoichiometric oxides in the actual contact spots. Carbon is in the free state. As a result, the friction coefficient decreases and, therefore, the wear resistance of eutectic alloys increases.     

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.     

Development of antifriction aluminum-base alloys and compositions for sliding current collectors

We have studied the effect of alloying of aluminum with copper (2–4%), silicon (2–4.5%), tin (10–15%), and lead (10–15%) on its wear resistance under conditions of friction in a couple with a copper contact wire. We have established that alloying enhances the wear resistance of metals and decreases the wear of contact wires. The use of an electrographitic bush decreases the wear of a metal insert. Field investigations of metal trolleybus current-collecting inserts with electrographitic bushes show that their durability is 5–8 times greater in dry weather and 2–3 times greater in rainy weather than that of conventional articles. In addition, the wear of the contact wire is minimally admissible. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 6, pp. 111–115, November–December, 2006.     

Structure and properties of composite iron-based coatings obtained by the electromechanical technique

The influence of the electrolyte temperature and current density on the content of inclusions of powder particles in composite coatings obtained by the electrochemical technique has been investigated. It has been found that the wear resistance of iron coatings with inclusions of powder particles of aluminum, kaolin, and calcium silicate increases from 5 to 10 times compared to coating without inclusions of disperse particles, and the friction coefficient therewith decreases from 0.097 to 0.026. It has been shown that the mechanical properties of iron obtained by the method of electrochemical deposition depend on their fine structure. The regimes of deposition of iron-based coatings have been optimized. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 23–27, September–October, 2007.     

Wear resistance of electrodeposited Ni–B and Ni–B–Si<Subscript>3</Subscript>N<Subscript>4</Subscript> composite coatings

The wear resistance of electrodeposited (ED) Ni–B and Ni–B–Si₃N₄ composite coatings is compared. The effect of incorporation of Si₃N₄ particles in the ED Ni–B matrix on the surface morphology, structural characteristics and microhardness has been evaluated to correlate the wear resistance. The wear mechanism of ED Ni–B and Ni–B–Si₃N₄ composite coatings appears to be similar; both involve intensive plastic deformation of the coating due to the ploughing action of the hard counter disc. However, the extent of wear damage is relatively small for ED Ni–B–Si₃N₄ composite coatings.     

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).     

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.     

Optimization of the procedure of plasma spraying of erosion-resistant coatings according to strength criteria

It is shown that mechanical characteristics of the coatings depend on their technological conditions of their deposition. We propose a procedure of optimization of the technological process and control over this process according to the criteria of strength and specific consumption of materials by analyzing an example of plasma spraying of erosion-resistant coatings. The erosion resistance exhibits the most stable correlation with the cohesive strength of the coatings. The regression equations are used to determine the maximum levels of cohesive strength of the coatings and erosion resistance for the optimal combinations of technological parameters of. Translated from Problemy Prochnosti, No. 6, pp. 136–151, November–December, 2008.     

On estimation of materials durability

A wear resistance function was proposed to characterize relative wear resistance of materials. Submitted results make it possible to determine parameters of the wear resistance or durability of materials and protective coatings. Franko Drogobych State Pedagogic Institute, Drogobych. Lublin Polytechnic Institute, Lublin, Poland. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 6, pp. 88–92, November–December, 1997.     

Synthesis,corrosion and wear of anodic oxide coatings on Ti–6Al–4V

Electrodeposited anodic oxide coatings were produced on Ti–6Al–4V substrates using aqueous electrolytes containing dissolved calcium and phosphorus. Different coatings were produced by varying the time periods. The coatings were characterised by XRD technique and TEM. The coatings were exposed to Simulated Body Fluid (SBF). Electrochemical polarisation and ac impedance studies too were performed on the coatings in SBF. Pins were coated and run against wooden disc in pin-on-disc type of wear tests. Coatings produced from long time electrolysis showed very good resistance to the attack of SBF and less wear compared to those produced from short time exposure.     

The effect of humidity on friction and wear of an aluminium–silicon eutectic alloy

The sliding wear of an aluminium–silicon eutectic alloy against cast iron counterface in 3–100% relative humidity range has been investigated. The results show that the moisture content has a significant effect on the friction and wear of the Al–Si alloy. The wear rate decreases by two orders of magnitude as the relative humidity increases from 3% to 100%. At low humidity conditions adhesive wear is predominant, whilst at high humidity conditions a layer of compacted oxide–metal debris film is formed on the Al–Si slider surface, which reduces the direct metal–metal contact. The friction coefficient is maximum at 3% and 100% relative humidity conditions. This revised version was published online in November 2006 with corrections to the Cover Date.     

Influence of Surface-Modified Conducting Fillers on the Properties of Epoxy Coatings

We have developed a new epoxy composition for antistatic coatings on metallic surfaces, filled with technical carbon and talc, which had been surface-modified by paranitroaniline and phosphoric acid. It has been shown that, with the introduction of modified fillers, the content of gel fraction in an epoxy coating increases by 5–6%, its adhesion becomes 2.5–2.7 times higher, and the amount of organic solvents decreases. We have also established that the electric resistance of the coating is more stable in time as compared with the commercial antistatic ground-coat enamel, and the frequency dependence of the resistance is more clearly pronounced after exposure to a chloride-containing medium, which corroborates the better protective properties of antistatic coatings with modified current conductive fillers. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 4, pp. 53–58, July–August, 2005.     

A study of properties of chromium-diamond coatings using nanodiamonds from various producers

The paper addresses the dependence of the key performance parameters of chromium-nanodiamond coatings on the quality of detonation nanodiamonds under study and on the method of their dispersion in an aqueous suspension. It is demonstrated that the best result in terms of the coating microhardness for the coatings prepared by the hard chromium plating method has been achieved with the nanodiamonds produced by NanoCarbon Research Institute (Japan), which indeed form a dispersion of individual particles (about 4–5 nm in size) in water. It is also found out that the best wear resistance is offered by the chromium-nanodiamond coatings deposited using detonation nanodiamonds produced by Tekhnolog SDTB FSUE (Russian Federation).     

Study of the structure and adhesive properties of ceramic coatings prepared by plasma spraying

We study the influence of technological parameters on the formation and structure of ceramic coatings based on Al₂O₃ and deposited by plasma spraying. We present the results of investigations of the adhesive properties of plasma-sprayed coatings based on Al₂O₃ and ZrSiO₄ that form tribological couples with 19,436 and 12,050 steels and polyamide. It is shown that the parameters of an A-160 plasma torch with aqueous plasma stabilization are suitable for the high-quality melting of ceramic materials based on Al₂O₃ if we use powders with particles 40–100 μm in size and perform spraying from a distance of 200–600 mm. Ceramic layers are formed by three types of particles of different shapes with different arrangements. Defects in the structure of the layers (pores, hollows, branched cracks, and large particles) deteriorate the properties of the coatings. The coatings based on Al₂O₃ and ZrSiO₄ exhibit the best properties under the conditions of abrasive wear, and this material, in combination with 19,436 steel, is suitable for application in friction couples. The degree of wear corresponds to the the value of the friction coefficient for the investigated tribocouples determined by the hardness of the material surfaces in the couple. The ceramics-polyamide couple seems to be quite promising due to the low friction coefficient and minimum wear. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 2, pp. 62–70, March–April, 2008.     

Electrolytic deposition and corrosion resistance of Zn-Ni coatings obtained from sulphate-chloride bath

Zn-Ni coatings were deposited under galvanostatic conditions on steel substrate (OH18N9). The influence of current density of deposition on the surface morphology, chemical and phase composition was investigated. The corrosion resistance of Zn-Ni coatings obtained at current density 10–25 mA cm⁻² are measured, and are compared with that of metallic cadmium coating. Structural investigations were performed by the X-ray diffraction (XRD) method. The surface morphology and chemical composition of deposited coatings were studied using a scanning electron microscope (JEOL JSM-6480) with EDS attachment. Studies of electrochemical corrosion resistance were carried out in the 5% NaCl, using potentiodynamic and electrochemical impedance spectroscopy (EIS) methods. On the ground of these research, the possibility of deposition of Zn-Ni coatings contained 24–26% at. Ni was exhibited. It was stated, that surface morphology, chemical and phase composition of these coatings are practically independent on current density of deposition. On the basis of electrochemical investigations it was found that corrosion resistance of these Zn-Ni coatings is also independent of current density. These coatings are more corrosion resistant in 5% NaCl solution than metallic cadmium. It was suggested that the Zn-Ni coating may be used as a substitute for toxic cadmium.     

Tribological Properties of TiN-Cr Electric-Spark Coatings after Solar Treatment

We show the prospects of using TiN-Cr electrode materials for the formation of wear-resistant electric-spark coatings under the influence of concentrated sunrays, which increase the wear resistance of the coatings two to three times. Electric-spark coating made of 40% TiN and 60% Cr possesses optimal tribotechnical and physicomechanical properties. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 4, pp. 116–120, July–August, 2005.     

Physicochemical properties of molybdenum-carbide-based electroplates on steel materials

We investigate the physicochemical and mechanical properties of molybdenum-carbide-based electroplates deposited by ionic-melt electrolysis on steels. The possibility of depositing electroplates up to 100 μm thick at a deposition rate of 5–25 μm/h with a current yield of up to 50% is demonstrated. The coatings increase the wear resistance of steel samples by a factor of 5–7 and the abrasive resistance by a factor of 4–6. Vemadskyi Institute of General and Inorganic Chemistry of the Ukrainian Academy of Sciences, Kiev. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 34, No. 2, pp. 63–68, March–April, 1998.     

Wear characteristics of a new type austenitic stainless steel

In order to solve the problem of the poor wear resistance in conventional austenitic stainless steels, a new type austenitic stainless steel was designed based on Fe–Mn–Si–Cr–Ni shape memory alloys in this article. Studies on its wear resistance and wear mechanism have been carried out by comparison with that of AISI 321 stainless steel using friction wear tests, X-ray diffraction, scanning electron microscope. Results showed that the wear resistance of Fe–14Mn–5.5Si–12Cr–5Ni–0.10C alloy was better than that of AISI 321 stainless steel both in dry and oily friction conditions owing to the occurrence of the stress-induced γ → ε martensitic phase transformation during friction process. This article also compared the corrosion performance of the two stainless steels by testing the corrosion rate. Results showed that the corrosion rate of Fe–14Mn–5.5Si–12Cr–5Ni–0.10C alloy was notably lower in NaOH solution and higher in NaCl solution than that of AISI 321 stainless steel.     

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).     

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.