Analysis of the Quality of Sulfomolybdenum Coatings Obtained by Electrospark Alloying Methods

The authors of this paper have attempted to improve the quality of surface layers applied to steel elements of machine parts constituting friction couples. The main goal of the research was to investigate an electrospark alloying method process for obtaining abrasion-resistant tribological coatings containing molybdenum disulfide on a steel surface. A substance in the form of sulfur ointment with a sulfur content of 33.3% was applied on the surfaces of C22 and C40 steel specimens. In order to determine the influence of the energy parameters of ESA equipment on the quality parameters of coatings, the ESA process was carried out using a molybdenum electrode with discharge energies Wp = 0.13; Wp = 0.55; Wp = 3.4 J. The following tests were carried out on specimens with such coatings: metallographic analysis, microhardness tests, surface roughness, and local X-ray diffraction microanalysis. The experiments revealed that sulfomolybdenum coatings consist of four zones with different mechanical properties. Depending on the discharge energy and the substrate material, the hardness of these zones varies from approx. 1100 to over 10,000 MPa. Differences in the distribution of, among others, sulfur and molybdenum in the obtained coatings, as well as differences in the microstructure of the observed coatings, were observed.

Effective Wear Resistance Parameters of Ion-Plasma Tribological Coatings

Comparative studies of wear resistance during dry friction of vacuum ion-plasma coatings of nitride systems TiAlN and CrAlSiN are carried out. The structural parameters, coating thickness, and physical and mechanical properties were chosen as comparison parameters. A fundamental difference in the wear mechanisms of the coatings is demonstrated. In the TiAlN-system coatings develop an oxidative wear mechanism due to their insufficient heat resistance. The CrAlSiN-system coatings have maximum resistance to plastic deformation. And they are wear out according to the fatigue mechanism, which is typical for coatings with a high level of mechanical properties.

Increasing the resource of agricultural machinery

An effective technique in the improvement of wear resistance and resource especially wornout friction is provided in the surface parts of anti-friction tribological coatings of various compositions entered in the regular lubrication maintenance of machines and equipment [1, 5, 7–10, 12–17]. Approved since 1930 [10] they during maintenance of machinery and equipment allows 2–3 times to increase their service life, 5–20 % reduced consumption of fuel and electricity, up to 30 % operating costs [7, 9, 10, 13, 14]. Introduction to oil chemically active substances, suspensions of particles of natural and artificial minerals, the oil solutions of the active organic substances, metal salts of organic acids [7, 17], the electric charge consumption less than 1 W [4, 6, 11], creating a wear-reducing coating [2, 5, 8, 12, 15–17], enhance adhesion of the lubricant is technically and economically justified, with a margin of 500–800 % or more [1, 3, 5, 7–10, 12–17]. CIP technical service as part of the overall system of technical maintenance and repair of machines, meets all the periods of their life cycle, and includes the testing, diagnosis, commissioning and preventive triboactive, the cleaning of the lubrication systems of engines, fuel, cooling, and most importantly — the restoration of worn units repair-regenerative trains [5, 7–10, 12–14, 17]. In the last intake of the mineral particles of the catalytically active open friction surface are subjected to a mechanical cold deformation, are involved in adhesion, physical and chemical processes, tribromoimidazole, catalysis of tribo-processes [2, 15–17]. As a result of the repair coating [2, 5, 12, 15–17]. The serpentine triboactive create a durable anti-friction coatings [2, 15–17]. According to research by European and American researchers [15, 16], especially in Chinese state laboratory of Tribology of Tsinghua University [17], these minerals cause the formation of diamondlike carbon fi lms (Diamond-Like carbon fi lms — DLC-fi lms). Their surface is high purity and hardness, underneath are visible traces of mechanical processing, for 90 % consist of carbon, the resistance of 10–300 Ohm/cm. The eff ect of serpentine processing is manifested through the hours and ability to operate even without triboactive [2, 10]. Below are the laboratory tribotechnical tests of triboactive and fi ling of charges in the oil, which confi rm the eff ectiveness of non-traditional tribology.

Tribological Studies of Epoxy Composites With UHMWPE and MoS2 Fillers Coated on Bearing Steel: Dry Interface and Grease Lubrication

Epoxy with ultra-high molecular weight polyethylene (UHMWPE) and MoS2 fillers was coated on a bearing steel (SAE 52100). Frictional and wear properties of the coated samples in sliding contact were investigated on a pin-on-disc tribometer under a normal load of 10 N and a linear sliding speed of 1 m/s against a bearing steel ball. The optimized coating composition (72 wt% Epoxy + 7 wt% hardener + 18 wt% UHMWPE + 3 wt% MoS2) showed highly improved tribological properties compared to pure epoxy and other epoxy-based composites. There was 75% reduction in the coefficient of friction (COF) in the dry interfacial condition (COF reduced from 0.2 to 0.05) over pure epoxy and 80% reduction with grease as the lubricant. The specific wear-rate of the composite was lower by five orders of magnitude over that of pure epoxy. Other mechanical properties such as hardness, tensile strength, and Young's modulus of the composite showed increments of 86%, 121%, and 43%, respectively, with respect to those of pure epoxy. 2–3 wt% of MoS2 had drastic effects on improving strength and reducing friction and wear of the composites. For dry sliding, initial abrasive and adhesive wear mechanisms led to transfer film formation on the steel counterface, and the shearing was mainly within the transfer film. For the grease-lubricated case, a thin layer of grease helped in easy shearing, and the transfer film formation was avoided. This epoxy-based composite will have applications as tribological coatings for journal bearings.

Literature Review on Fretting Wear and Contact Mechanics of Tribological Coatings

This article reviews fretting wear damage in industries and in the contact mechanics of coated systems. Micro-slip motion resulting in fretting damage is discussed along with major experimental factors. The experimental factors, including normal force, relative displacement, frequency and medium influence are directly compared. Industrial solutions to reduce fretting damages are then discussed. The contact mechanics of a coated system are reviewed to quantify stress states in a coating layer and the substrate. Finally, a literature review on simulation for fretting is carried out. This review study provides useful methods and practical solutions to minimize fretting wear damage.