Composite materials based on titanium nitride for high-speed friction units

Tribological properties are examined for composite materials based on titanium nitride under conditions of dry friction for a wide range of speeds (1–25 m/sec). It is shown that the composites have a high level of tribological properties, which may be better (by up to an order of magnitude) than the properties of known materials. These results are used in guidelines for prospective materials for high-speed friction units. It has been found that there is a necessary condition for the materials to be used in high-speed friction units in that there should be high adhesion strength for the films of oxidation products together with low tendency to adhesion interaction with the counterbody.     

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.     

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.     

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.     

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.     

Corrosion and tribotechnical properties of materials based on Kh18N15 stainless steels with MoS2 and Cr3C2 additives

The corrosive and tribological properties of sintered chromium nickel stainless steel Kh18N15 (18% Cr, 15% Ni) materials, with additions of 2, 4, 6 and 8% MoS₂ and 10% Cr₃C₂ are studied. Adding those amounts of MoS₂ are found to have no significant effect on the corrosive and tribological properties of the steel. Simultaneous addition of MoS₂ and Cr₃C₂ to Kh18N15 can alter the tribological properties without any appreciable change in the corrosion resistance. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(405), pp. 62–68, January–February, 1999.     

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     

Tribological properties of thermally expanded graphite reinforced with knitted metal nets

Production of thermally expanded graphite composites reinforced with knitted copper net is developed and their tribological properties are determined. Wear resistance under reciprocating and rotary movement can be improved by the reinforcement. Reinforced thermally expanded graphite seals may be a substitute for asbestos-containing materials. Institute of Materials Science Problems, Ukrainian National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 33–37, July–August, 1997.     

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.     

Increasing the wear resistance of surface layers of high-speed steel by electric-spark alloying and laser treatment

How the combined action of high-energy spark alloying and laser treatment affect the wear resistance of high-speed steel cutting tools has been studied. That action has been found to form a strengthened layer of composite refractory compounds on the tool surface, thus making it hard and wear-resistant, and create a protective barrier that reduces the adhesive interaction of the cutting tool with a chip. The tribological properties and the durability of the cutting tool can be enhanced by alloying the surface layer with elements and compounds that form stable oxides tightly bonded to the substrate. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(408), pp. 44–51, July–August, 1999.     

Fatigue and Compression Characteristics of Al 6061–B 4 c Composite Materials

Aluminum matrix composites reinforced with boron carbide are a kind of materials that are widely used because of high strength, low density, and improved tribological properties. In this study, mechanical properties of Al 6061–B4C composites reinforced with B4C of three different particle sizes were investigated. In the Al 6061–B4C composite materials, produced by the powder metallurgy methods (extrusion of billets obtained by sintering at temperature of 550°C under pressure of 450 MPa), the change of mechanical properties such as hardness, compressive strength, and fatigue life, related to B4C particle size and the applied heat treatment mode (aging at 180°C for 5 h), were investigated. The hardness of the materials is increased with B4C grain size and the heat treatment. After the heat treatment, the fatigue life of Al 6061–B4C (3 μm) material increases slightly, while that of the composite materials decreases with larger size of B4C reinforcement. The fatigue life of the composite materials reinforced with a larger grain size B4C is reduced by heat treatment. While the compression test data of untreated composite materials were similar to each other, the heat treatment increased these values in all samples. The highest increase in the compression strength was observed in the composite reinforced with 17 μm sized B4C. The addition of graphite reduces the deformation ability of the composites.     

Friction properties of composites of the system TiN−AlN. I. Effect of structure and phase composition of friction and wear of materials of the system TiN−AlN

The tribological properties of ceramic composites of the system TiN?AlN are studied in the concentration range 10–90% AlN. It was found that materials which contain 25, 50, and 75% AlN have a low friction coefficient. Their rate of wear when paired with steel is neglible—2.9–6.0 μm/km (the wear rate of a steel-steel 024 couple is 1000 μm/km). Thin oxide films are formed during friction at high velocities and pressures. These films have relatively high adhesion with respect to materials of the TiN?AlN system and relatively low adhesion with respect to steel. The films may act as a solid lubricant, thus reducing the friction coefficient and wear. This is particularly true of the materials 25% TiN?75% AlN and 50% TiN?50% AlN.     

Effect of the content of calcium fluoride and lead on the structure evolution and the tribo-technological characteristics of a copper-based sintered material

Conclusions Calcium fluorids is a multifunctional additive. It participates in the development of the tribological characteristics, enhances the volumetric shrinkage of the materials, and prevents lead-sweating after sintering.Lead decreases the coefficient of friction of the composite materials. However, increasing its content up to 11 wt. % increases the wear of the materials abruptly. This is related to the weakening effect of lead and its distribution in the form of thin elongated layers between the grains of copper.The copper-based sintered antifriction materials containing up to 6 wt. % lead and 11 wt. % calcium fluoride have a low coefficient of friction (0.15–0.25) under the conditions of friction without lubrication; furthermore, they exhibit an insignificant wear rate (0.3–3.3m/km) and can be recommended for the high-speed friction assemblies as effective replacements for the copper-graphite materials.Translated from Poroshkovaya Metallurgiya, No. 8(344), pp. 78–83, August, 1991.     

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.     

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.     

361441

The tribological properties of materials were studied under conditions which model the collective and individual effects of outer space factors (vacuum, cryogenic temperatures, solar electromagnetic radiation). The behavior of aerospace materials (structural materials, self-lubricating composite materials, antifrictional solid lubricant coatings, wear-resistant coatings, etc.) were investigated. An approach to the design of materials for friction units is proposed, based on the concept that the materials of a friction pair are a complex self-organizing system. This made it possible to substantially expand the range of application of materials and coatings, and aided in the creation of new antifriction materials with pre-determined properties.     

Modification of aluminum antifriction alloys by carbon nanomaterials

A procedure is developed for modification of the near-surface layers of AO-20-1 alloy (AlSn20Cu, GOST Standard 14113–78) by carbon nanotubes at a depth of 2 μm. Data on the depth distribution of carbon across the near-surface layer are obtained. Mechanical and tribological tests of the modified layer are performed. It has been found that the hardness of the near-surface layer increases by 10–60% at a depth up to 1 μm and the friction coefficient decreases by ∼25 %.     

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.     

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.     

Tribotechnical characteristics of powder composite materials based on copper in high-speed friction

Conclusions Copper and the composite materials based on copper (with mullite, glass ceramic, and also sulfur and molybdenum sulfide) have a high friction coefficient (0.23–0.46), a medium temperature of the friction surface (130–270°C), and are susceptible to bonding with the contacting surface (07Khl6N6 steel).The materials containing 10% graphite, sulfur, and molybdenum disulfide have a low friction coefficient (0.09–0.15), do not bond to 07Khl6N6 steel, and can be recommended for service in high-speed friction units.Translated from Poroshkovaya Metallurgiya, No. 7(283), pp. 52–56, July, 1986.