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.     

Friction, wear, and targeted synthesis of rubbing surfaces of self-lubricating composites

Self-lubricating copper-based composites are developed. It is shown that the structure of the surface layer, which is formed and deformed by the friction forces at the interface, is the major contributor to the friction process. The main stages of developing highly efficient tribotechnical materials for extreme operating conditions (high pressing forces and sliding velocities, absence of lubrication, high vacuum) are examined. A comprehensive approach to constructing tribotechnical composite systems is used to develop several copper-based materials for different operating conditions; in particular, self-lubricating antifriction composites to perform in high-speed friction pairs as well as in tribotechnical systems operating under high vacuum. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 11–19, 2007.     

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.     

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.     

Effect of a strengthening phase on the structure and some mechanical properties of electrolytic coatings based on nickel

An investigation was made of the composition, structure, microhardness, and tribological properties after thermochemical treatment of composite electrolytic nickel-based coatings with various additions. It was established that the mear resistance of nickel-boron-diamond coatings in sliding friction without lubrication depends upon the nature and amount of added inclusions, and the mechod of treatment. Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 47–51, May–June, 1998     

Evaluation of Tribological Characteristics of Electric-Spark Coatings Prepared on Steel with Electrode Materials of the System TiN - Ni

The tribological and physicomechanical indices of electric-spark coatings of the system TiN - Ni are studied in relation to the phase and structural state of the electrode material. It is established that the optimum tribological properties are exhibited by TiN + (20–40)% Ni material due to forming a eutectic structure consisting of hard intermetallics and a ductile solid solution. It is shown that the ductile component (nickel) makes it possible to deform the coating material without embrittlement. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(443), pp. 43–48, May–June, 2005.     

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.     

Effect of electric field on the destruction of the friction surface of sintered metal composites

The wear resistance and electrical resistance of the friction area of powder model composites based on Hadfield steel (Γ13 grade) and processed steel are determined under the conditions of sliding electrical contact at a current density of above 100 A/cm². The structure of materials and the three-dimensional image of the friction surface are presented. The composite based on Γ13 steel is shown to form a contact area with high electrical resistance and roughness. It is found that the transition of the composite material on a steel counterbody occurs under the effect of electric erosion within the friction area. It is determined that the mode of catastrophic wear happens at a current density of ∼200 A/cm².     

Wear resistance of a plasma-electrospark zirconium diboride-based coating on aluminum alloy D16T

The paper examines the structure, phase composition, and mechanical properties of ZrB₂-based plasma coatings formed on D16T aluminum alloy under different conditions. It is established that coatings with an electrospark sublayer are characterized by stronger adhesion with the substrate as compared with that deposited on the base after conventional sandblasting. The wear resistance of this coating in dry friction is comparable with the monolithic VK15 hard alloy. Laser treatment of the coating in open air decreases the wear by 25% at low sliding rates and simultaneously decreases the hardness by 50%. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 5–6 (455), pp. 53–59, 2007.     

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.     

MoS_2对铝基材料摩擦磨损性能的影响

以Al,Fe,Zn等金属粉末和Si粉为原料,采用热压法制备MoS_2含量(质量分数)分别为0和3%的铝基复合材料,在滑动速度为0.377~1.131 m/s以及载荷为4~10 N的条件下进行摩擦试验,研究MoS_2对铝基复合材料摩擦磨损性能的影响。结果表明:在0.377 m/s的滑动速度下,3%MoS_2/铝基复合材料在10 N载荷下具有较低的平均摩擦因数0.4,比不含MoS_2材料的摩擦因数降低近一半;在0.755 m/s的滑动速度下,2种材料的摩擦因数和磨损率接近;在1.131 m/s的滑动速度下,载荷7~10 N时2种材料都严重磨损,3%MoS_2/铝基材料具有相对较低的磨损率,磨损机理为熔化磨损,未添加MoS_2材料的磨损机理为严重塑性变形磨损。添加3%MoS_2可显著改善铝基材料的摩擦磨损性能。     

Wear resistance of composite material made of eutectic steel and bronze powders

The tribological properties of a hardened steel U8-composite pair in contact in which bronze is used as the matrix and eutectic alloy powder (steel 30Kh13 with 15 wt.% VC of eutectic structure) is used as a filler are studied under conditions of reciprocal sliding friction without lubrication. Composite and counterbody wear is not uniform and it depends on the amount of filler within the range 20–80%. A composite with 80% filler has good tribological properties and satisfactory lathe machining.Institute of Metal Physics, Academy of Sciences of the Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 69–73, January–February, 1994.     

Studies on Structural Changes in the Surface Layers of Aluminum Alloys Based on the Al–Si–Cu System under Frictional Deformation

Experimental antifriction aluminum alloys based on an Al–5% Si–4% Cu system with the addition of low-melting components such as Bi, Pb, In, and Cd have been studied. An optimal heat treatment mode has been adjusted, including the hardening at a temperature of 500°С with further aging at 175°С. The tribological testing have been carried out according to a pad–roller scheme (Steel 45 as the material under study) at a pressure of 0.5, 1.0, and 2.0 MPa to simulate the operation of a bearing mount assembly. It is shown that all the experimental alloys have similar tribological properties, but their mechanical characteristics, in particular, hardness, are different. Of greatest importance is an alloy containing cadmium. Using electron microscopy, the topography is studied and the elemental composition is determined for the surfaces of a roller and a pad made of this material before and after tribological testing. A process of active mass transfer in the contact zone under friction is revealed. In this case, the formation of a film consisting of secondary structures on the roller is observed. The film has the following features: an uneven distribution on the surface with a developed relief and a maximum film thickness reaching 200 μm. It is shown that, under the friction conditions that are used, such a film promotes the formation of scuffing. It has been found that the scuffing occurs after testing at a pressure higher than 1 MPa for all the studied experimental alloys. The nanoindentation of a pad performed at a load ranging from 10 to 100 mN has shown an increase in the hardness of a surface layer about 30 μm thick. This could be connected with the hardening of the material owing to plastic deformations in the friction zone.     

AS41耐热镁合金的摩擦学行为研究

本文研究了AS41耐热镁合金在室温和200℃时的显微组织、力学和摩擦学性能,并探讨了其在高温的摩擦学机理。研究表明:AS41耐热镁合金主要由基体(α-Mg)相和第二相(Mg17Al12、Mg2Si和MgO相)组成,其在200℃时除延伸率有所增加外,抗拉强度和屈服强度均较室温时显著下降。耐热镁合金的摩擦系数随载荷增大而减小,滑行速度和滑行距离对摩擦系数的影响不大;磨损率随着载荷和滑行距离的增加而增大,但随滑行速度的增加而减小;且耐热镁合金在200℃的摩擦学性能优于其室温摩擦学性能。随着载荷变化,磨损机理发生变化;低载荷时表现为氧化磨损和磨粒磨损;中等载荷时表现为磨粒磨损和轻微剥层磨损;较高载荷时表现为剥层磨损。     

High Temperature Tribological Studies on Surface Engineered Tool Steel and High Strength Boron Steel

The popularity of hot sheet metal forming processes in the recent years has necessitated research efforts to improve tool life and control the friction level during hot forming operations. In this work, the tribological properties of tool steel and ultra high strength boron steel (UHSS) pairs at elevated temperatures have been studied by using a special hot sheet metal forming test rig that closely simulates the conditions prevalent in the real process. This test involves linear unidirectional sliding of a preheated UHSS sheet between two tool steel specimens where new workpiece material is continuously in contact with the tool surface. The study is aimed at investigating different surface treatments/coatings applied on either the tool or sheet surface or on both. The results have shown that it is possible to control the coefficients of friction through surface treatments and coatings of the tool and workpiece materials. The application of a coating onto the sheet material has a greater influence on the friction compared to changing the tool steel surface. After running‐in, the investigated tool steel variants show almost similar frictional behaviour when sliding against the same sheet material. Although coating the UHSS sheet reduces friction, it abrades the tool surface and also results in transfer of the sheet coating material to the tool surface.     

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.     

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.     

Cu/Mo_5Si_(3p)复合材料的摩擦磨损性能研究

采用销—盘式摩擦磨损试验机研究了液相烧结制备Mo5Si3颗粒弥散强化铜合金在滑动干摩擦条件下的摩擦磨损行为。结果表明:Cu/Mo5Si3p复合材料具有优良的摩擦磨损性能。随着Mo5Si3含量的增加Cu/Mo5Si3p复合材料的硬度增加,摩擦系数和磨损失重量降低。Mo5Si3含量低时,Cu/Mo5Si3p复合材料的磨损机制为犁沟变形和粘着磨损为主,而Mo5Si3含量高时则为犁沟变形磨损为主。     

Effect of silicon on the wear resistance of high-carbon steels with the structures of isothermal decomposition of austenite during friction and abrasive action

The hardness and wear resistance during sliding and abrasive friction of 80S2 (0.83% C, 1.66% Si) and U8 (0.83% C) steels subjected to the isothermal γ → α decomposition in the temperature range 330–650°C and additional 5-min annealing at 650°C are compared. The optimum decomposition temperature is found to be 550°C. At this temperature, fine lamellar pearlite with the maximum hardness and wear resistance as compared to other pearlitic and bainitic structures forms in the silicon steel. The silicon-alloyed fine lamellar pearlite of 80S2 steel is found to have high hardness and abrasive wear resistance as compared to the similar structure in plain U8 steel; however, this pearlite has no advantages in the wear resistance under conditions of sliding friction on a steel plate. Silicon alloying of the bainitic structures in the eutectoid steel leads to a noticeable decrease in the wear resistance during sliding friction and abrasive action. Friction oxidation is shown to negatively affect the abrasive wear resistance of the silicon steel.