621.9.048Studies have been made on the structure and properties of spark coatings made of TiN and TiB 2 on steel U8 after treatment with concentrated solar radiation. It is found that the absorption capacity of the steel raised by a factor 2-3. The concentrated radiation reduces the coefficient of friction of the spark coatings made of TiN and TiB 2 by a factor 1.4, while the wear rate is reduced by a factor 1.6-2 by comparison with the untreated material.Concentrated solar radiation (CSR) used to treat protective coatings often considerably improves their physicotechnical characteristics [1,2]. Advantages of this method are the contactless heating in any medium or vacuum, clean heating, and scope for regulating the energy density over a wide range.Spark alloying (SA) produces surface layers with altered structure and composition as well as good adhesion. The method is simple, but one shortcoming is that it produces discontinuous rough coatings because of a discharge pulse discreteness. Therefore, to improve the properties, the SA coatings need additional treatment with focused solar radiation. This reduces the porosity, heals the microcracks, and improves the adhesion.Titanium nitride is a promising material for making wear-resistant coatings [3]. To reduce the brittleness of the titanium nitride electrodes and to increase the transfer factor, Cr and Ni are added, which form unrestricted solid solutions with the iron that is the basic element of the substrate. Adding Mo is used to increase the strength at high temperatures.Studies have been made [4, 5] on the structure and properties of coatings after SA with materials based on TiN, which have given erosion characteristics and electrode transfer coefficients. The purpose of the present study has been to examine improving the physicomechanical properties of spark coatings by treatment with concentrated solar radiation.Spark coatings on U8 steel were made with TiN − (Cr, Ni), TiN − (Mo, Ni), TiB 2 − (Mo, Ni) electrodes; all of the compositions included Al 2 O 3 . The SA was performed with an EFI-46A equipment with I = 1.5 A and C = 300 μF.The surface was treated with focused solar radiation in a SGU-2 equipment, which consisted of a mirror concentrating the solar energy fitted with a sun-tracking system. The radiation flux was regulated within the range 3000-4000 kW/m 2 by means of a blind. Tribological studies were performed with an MT-65 equipment with V = 10 m/sec and load P = = 0.5 MPa on a shaft-insert scheme in air by a standard method [6]. We recorded the frictional force, from which we calculated the coefficient of friction f and the linear wear of the friction pair, which gave the wear intensity I.X-ray diffraction was applied to specimens treated with focused solar radiation with a DRON-3M apparatus in CuK α radiation, while metallographic analysis of the spark coatings and the steel substrates employed an MIM-10 optical microscope.
621.9.048The 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.In order to provide good operating reliability for machines and to increase their service life new composite materials are required with high antifriction properties. Titanium nitride with added metals is a promising material. Pure titanium nitride does not provide sufficient coating thickness and continuity due to its low affinity with steel [1]. A stable bond with a steel substrate and a strong coating of considerable thickness forms with nickel [2].The aim of the present work is to study the dependence of tribological properties (wear resistance and friction coefficient) for electric-spark coatings on the phase composition and structure of electrode materials TiN + (1-100)% Ni.The alloying electrodes were prepared by compaction and sintering in a travelling hearth furnace in an argon atmosphere at 1400-1700°C. Electric-spark alloying (ESA) of steel was accomplished in a ÉFI-46A unit (working current strength I w = 1.25 A, C = 350 μF, open-circuit voltage U o.c = 15 V). Metallographic analysis was performed in a Neophot-2 instrument, and x-ray phase analaysis was performed in a DRON-3 in copper and cobalt radiation. Tribological properties were determined in a M-22M device [3] that made it possible to record the coefficient of friction f and wear intensity I of a specimen during an experiment. Tests were carried out in air by a sleeve-shaft scheme without supply of lubricant to the contact zone in a pair with steel KhVG with a sliding rate V = 0.5 m/sec and pressure P = = 2.0 MPa.The phase composition of the electrode material has the most effect on alloyed layer properties (Table 1). According to the results obtained formation of oxides and solid solutions has a different effect on strengthened layer formation. It was established by x-ray phase analysis of TiN − Ni electrode materials that nickel and titanium form solid solution and intermetallic in accordance with the phase diagram for TiN − Ni [4]. The phase composition of TiN − Ni materials has been studied in [5]. These are solid solutions of titanium in nickel, intermetallics Ti 2 Ni, TiNi 3 , nonstoichiometric TiN 1−x ( Table 1). As a result of titanium nitride dissociation [2] there is formation of non-stoichiometric TiN 1−x and a solid solution of titanium in nickel typical for all compositions containing the metal binder. Formation of * Deceased.
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