Effect of factors governing dry friction on structure formation for the tribological synthesis zone in composites based on copper

Features and peculiarities of structure formation for the friction zone in highly effective composite materials based on copper for prescribed experimental conditions (high contact loads and sliding rates, absence of a lubricant, operation in a high vacuum or in air) are considered. It is shown that reliable efficiency for a tribological system under friction conditions with action of high compressive forces and sliding rates is provided by material adaptation that is achieved via the tribological synthesis at the contact surfaces of a lubricating layer different in composition and structure from the original composite. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 14–21, March–April, 2006.     

Influence of the Composition and Structure of B4C - Al2O3 Ceramic on the Tribotechnical Characteristics in Friction Against Steel

The morphology and phase composition of friction surfaces and the tribotechnical properties of the (B₄C - Al₂O₃)-steel 45 system are studied under dry friction at various sliding velocities and contact loads. We have found that fine-grained secondary structures are formed on the friction surfaces. The morphology and phase composition of these structures depend on the ceramic composition and on the test conditions. A comprehensive investigation of friction surfaces, using x-ray, electron-diffraction electron-probe, and electron-microscopy analysis, has shown that the structure and morphology of the secondary phases determine the tribotechnical properties of ceramic-steel couples. The maximum wear resistance of B₄C ceramics containing 5-20 mass% Al₂O₃ is determined by the formation of dense secondary-phase thin films on the friction surface. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(443), pp. 49–59, May–June, 2005.     

High-temperature friction of refractory compounds

The paper overviews long-term studies into the behavior of metallic (carbides, borides, and nitrides of transition metals), and nonmetallic (boron and silicon carbides, aluminum nitride) refractory compounds as well as composite materials based on them in high-temperature friction in vacuum and air. The friction characteristics (wear rate and friction coefficient) are indicated as a function of temperature in the range from room temperature up to 1000–1400 °C. Data of x-ray examination and electron microscopy of friction surfaces are cited. The fracture mechanism for contacting surfaces of materials in friction is considered. __________ Translated from Poroshkovaya Metallurgiya, Vol. 47, No. 1–2 (459), pp. 167–178, 2008.     

Fe在铜基粉末冶金摩擦材料中的作用

研究了Fe在铜基粉末冶金航空摩擦材料中的摩擦磨损作用及机理。研究表明:Fe在铜基摩擦材料中起到了摩擦组分的作用,对材料的机械性能和摩擦磨损性能起到了重要的作用。Fe能提高铜基摩擦材料的强度、硬度;当Fe含量超过4%后,随Fe含量的增加,材料的摩擦系数及稳定性增加;高速摩擦条件下,Fe能促进摩擦面氧化膜的形成,减小材料的摩擦系数和磨损量。     

Plasma coatings of (TiCrC)-(FeCr) composite powder alloys: Structure and properties

The coatings of the (TiCrC)-(FeCr) composite are deposited on steel and titanium alloy by plasma method. The composition, structure, and tribotechnical properties of these coatings are studied in comparison with traditional materials based on the Ni-Cr alloy. The effect of preliminary surface treatment methods, i.e., sandblasting treatment and electrospark alloying, on coating properties is examined. The fretting corrosion of coatings is investigated. It is established that coatings based on double titanium-chromium carbide have considerably greater wear resistance than that of Ni-Cr alloys at almost equal friction coefficients. It is established that electrospark alloying is competitive with traditional sandblasting treatment in environmental effect and coating-to-based adhesion. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 37–45, 2007.     

Structural changes in friction surfaces of plasma-sprayed coatings

The features surface morphology are considered for plasma-sprayed coatings used with various counterbodies under conditions of boundary friction. The tribotechnical characteristics of the coatings are examined in relation to the structure. There is found to be a substantial effect from the porosity on the formation of the secondary structures, the changes in topography, and the changes in elemental composition of the friction surface. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(405), pp. 92–97, January–February, 1999.     

Tribological Properties of Composite Materials Based on Refractory Titanium Compounds

The tribological properties have been examined for composite materials based on binary titanium-chromium boride and titanium nitride under conditions of dry friction over a wide speed range (1–25 m/sec). The materials have good tribological properties, which exceed by almost an order of magnitude those of known materials. Specifications are formulated for materials promising for high-speed friction units. A necessary condition for viability in high-speed friction units is high strength of the adhesion between the films of oxidation products, and another is low tendency for adhesion with the counterbody. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 58–64, July–August, 2005.     

High-temperature tribotechnical characteristics of ceramics based on aluminum nitride

Studies have been made on the structure, phase composition, and strength parameters for ceramics based on AlN containing 5–15 mass % TiO₂. The tribotechnical characteristics of these ceramics have been determined under sliding friction conditions at 20–900°C in air. Quantitative characteristics are proposed for the friction surface as determined by metallographic, microdurometric, and sclerometric examination of the surfaces produced at various treatment temperatures. Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3-4(400), pp. 43–48, March–April, 1998.     

Behavior of multilayer steel-bronze composites on frictional loading

Tribological aspects are examined for layered composites made by consolidation. Dry friction tests at sliding speeds of 1.6–4.3 m/sec show that this multilayer antifriction material is better by 1–2 orders of magnitude in wear resistance than the initial material. The multilayer composite can withstand a load increased by an order of magnitude without losing its viability under the conditions of surface-structure adaptation. Deceased. Translated from Poroshkovaya Metallurgiya, Nos, 1–2(411), pp. 38–44, January–February, 2000.     

Effects of preparation technique for MK-5 material on frictional and wear response

A study has been made on how the method of making a tribotechnical material affects the frictional and wear behavior. The materials have been made from identical initial powders, which corresponded in composition to standard MK-5 powder material, but different methods were used: traditional sintering under pressure and plasma spraying. The tribological properties of material made by plasma spraying are better than those of ones made by the traditional method, because of the presence of oxides formed during the spraying. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(411), pp. 44–47, January–February, 2000.     

孔隙度对湿式铜基摩擦材料摩擦磨损性能的影响

采用不同的压制压力制备湿式铜基粉末冶金摩擦材料,借助扫描电镜及摩擦磨损试验机研究材料的孔隙度对其组织和摩擦磨损性能的影响。结果表明:当孔隙度小于25%时,高孔隙度材料具有更高且更加稳定的摩擦因数,当孔隙度超过25%时,摩擦性能不稳定;磨损量随孔隙度减小先减小后增大。对此湿式铜基摩擦材料,20%为其最佳的孔隙度,此时材料具有最佳的摩擦磨损性能。     

Service properties of Cu–Sn–CuWO4–MoS2 composite and micromechanical characteristics of its friction surface

Powder Metallurgy and Metal Ceramics - The paper examines the tribotechnical characteristics of the Cu–Sn–CuWO4–MoS2 antifriction composite during lubricated and dry friction at...     

Formation and properties of a surface layer during comprehensive laser boriding of carbon steels

The main parameters of the laser action zones (microhardness, depth, tribotechnical characteristics, alloying element distribution) when carbon steels are laser-borided with powder composites based on high-boron high-melting compounds are investigated. It is demonstrated that the mass transfer of alloying elements into the pool of molten metal can be increased effectively by incorporating a surface-active element into the powder composites. Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2 pp. 74–78 January–February. 1997.     

Antifriction composite materials for friction joints of centrifugal equipment

Mechanical and antifriction properties of promising copper-based powder materials are examined. The metallographic structure of the new materials is studied. It is shown that copper-based composite materials can be successfully used instead of babbits for friction joints operating at high sliding speeds.     

SiO2/ZrO2复合陶瓷组元对铜基摩擦材料摩擦磨损性能的影响

在粉末冶金铜基摩擦材料中添加6%(质量分数)的SiO2/ZrO2复合陶瓷组元,研究SiO₂和ZrO₂的质量分数对摩擦材料摩擦磨损性能的影响,并分析其机理。结果表明:随w(SiO₂)/w(ZrO₂)比值减小,铜基摩擦材料的密度和硬度增大。高速制动时,摩擦材料的摩擦因数和摩擦稳定因数较小。SiO₂可有效提高摩擦因数,ZrO₂可降低摩擦副的磨损率。当w(SiO₂)/w(ZrO₂)为2/4时,摩擦材料具有较好的摩擦磨损性能,高速制动下平均摩擦因数为0.326,摩擦稳定因素处于较高水平,为0.71,对偶数材料损伤在可接受范围内。SiO₂较易脱落而形成磨粒,ZrO₂与基体界面结合状态较好,所以随SiO₂含量减少,主要磨损机制从磨粒磨损转变为黏着磨损和磨粒磨损,最后转变为剥层磨损。     

Investigation into the Influence of the Structure Dispersion and Homogeneity on the Properties of Powder Metastable Austenitic Carbide Steels and Diamond Tools

Diffusion and homogenization in “iron (5 μm–nickel (5 μm or 50 nm)” powder systems of various degrees of dispersion during sintering (900 and 1000°C), as well as spark plasma sintering, are investigated using the Matano–Boltzmann method. Calculated diffusivities in pairs of micron powders sintering without applying pressure (900°C, 6 h) and by the spark plasma method (900°C, 5 min) in these systems are equal to 7 × 10–10 cm2/s. It is shown that the use of nanodispersed nickel powder in diffusion pairs based on finely dispersed iron powder promotes a twofold increase in diffusivity at 900°C in contrast to the pair with the microdispersed nickel powder. Constants in the Ivensen sintering kinetics equation are calculated for the “iron–nickel” powder systems, by which the factors activating sintering of these systems are established. The dependences of the structural phase composition and physicomechanical properties of carbide steels of the Fe(base)–14 wt % Ni–8 wt % TiC system on the sintering temperature in range t = 900–1200°C and structure dispersity and homogeneity are determined. The dependences of the grain size, porosity, hardness, microhardness, fracture toughness, and bending ultimate strength on the sintering temperature are shown. Dependences of tribotechnical properties on the degree of homogeneity of the solid solution and volume of the phase transformation of metastable austenite into deformation martensite during abrasive friction turn out similar for carbide steels and diamond tools based on carbide steel. Optimal values of the variation coefficient of the nickel concentration in austenite and carbide steels of the same chemical composition but with different degrees of dispersity, which provide the maximal volume of the austenite decomposition and high values of the diamond-tool grinding coefficient, turn out equal to 5 in both systems, but the sintering parameters are different. It is shown that the physicomechanical properties of the studied systems depend on the structure porosity and dispersity, while tribotechnical properties depend on the structural homogeneity of steels.     

Physical principles and technological aspects of the production of gradient composites based on an oxygen-free ceramics

This article examines the technological aspects of producing a new generation of ceramic composites— functionally gradient materials. It is shown how a percolation model of the electrical conductivity of resistive systems that was modified by the authors can be used to predict the electrical and mechanical properties of composites with a high degree of accuracy. Gradient composites in conversion systems designed to convert an electrical energy into heat are used as an example to demonstrate the promise of the proposed method as a means of optimizing the processing regimes for the production of ceramic composites having the required level of electrical and mechanical properties. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3–4(406), pp. 3–16, March–April, 1999.     

Riction properties of composite materials of the system TiN - Ain. II. Effect of oxide films on friction and wear of a ceramic material — Steel system

Friction and wear are studied for materials of the system TiN — AlN preliminary oxidized at 800–1100°C. It was established that thin oxide films containing Al₂TiO₅ and α-Al₂O₃, that promote a decrease in frictional wear, form on the surface of composite materials of the system TiN — AlN. Our assumptions are confirmed that the improvement in tribological properties of TiN — AlN composites is caused by forming oxide screening layers that prevent direct contact between the ceramics and steel counter-body. At high rates (V=16 m/sec) and pressure (P=2.0 MPa) the oxide films form more rapidly. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(411), pp. 121–124, January–February, 2000.     

Influence of Aluminum on the Mechanical and Tribotechnical Properties of Sintered Copper-Based Friction Material

The principal physicomechanical and tribotechnical characteristics of friction materials based on tin bronze and aluminum-tin bronze have been studied over a wide range of velocities and friction loads. Aluminum-tin bronze which has slightly higher strength characteristics, is significantly harder than a similar tin bronze. This in turn affects the friction characteristics of the material, increasing the friction coefficient and wear resistance.     

成型压力对铜基粉末冶金摩擦材料性能的影响

研究成型压力对铜基摩擦材料显微组织和性能的影响。结果表明,铜基摩擦材料的密度随成型压力的增加基本保持不变;随着成型压力的增加,孔隙率明显降低,致密度提高。当成型压力从60t增加到100t时,铜基摩擦材料的硬度明显提高,当成型压力继续增加时,硬度出现下降趋势;铜基摩擦材料的摩擦系数随着成型压力的增加呈先降低后增加的趋势。在成型压力为100t时,铜基粉末冶金摩擦材料的综合性能最佳。