The reliability of antifriction coats of sliding bearings of compressors depends a great deal on the coating method. The results of study of wear of specimens based on the disk−block (shoe) scheme are reported. The characteristics of antifriction coats from babbit B-83 alloy applied by centrifugal casting method, plasma-jet spraying, and galvanic deposition are compared. The influence of porosity and density of babbit coats on their antifriction properties is studied.A pressing problem in modern development of compressor engineering is raising reliability of antifriction coats of sliding bearings, for which usually various grades of babbits on tin and lead base are used. The main methods of application of babbits are gas-torch (oxyacetylene) surfacing and centrifugal casting. The layer thickness in this case ranges from 1 to 12 mm and more. As is well known, the greater the babbit coat thickness, the less is the fatigue strength (resistance) of the coat. In fact, while detecting flaws in worked-out brasses (bushings), damage to the antifriction coat essentially in the form of flakes and cracks upon relatively minor wearing is noticed.Since the antifriction properties of babbit is better than many other antifriction alloys, its use for sliding bearings is fully justified. However, in mechanical properties babbit is much inferior to bronze, aluminum alloys, etc. Many authors [1, 2] point out that babbit coats are damaged in the process of use precisely because of their inadequate mechanical properties. Further, the thicker the coat, the worse is its mechanical properties. To ensure mechanical strength of antifriction coat, alloys of aluminum with AO-20 type of tin are used, but still application of babbit as an extra coat is considered advisable [3].The reliability of antifriction coats, including babbit coats, depends a good deal on the method of its application. For instance, practical experience showed that plasma-jet spraying of babbit B-83 on bearing brasses (bushings) significantly extends the life of the bearings.Similar results are reported in [4], where service properties of babbit coat are noted to be 2-2.3 times better than the same coat obtained by casting.At Plaztekh-S investigations were made to enhance the reliability, service properties, and, ultimately, the life of antifriction coats on various types of sliding bearing.Based on a study of the literature sources, patents, and our own investigations, it was proposed to test antifriction coats from babbit B-83 applied by plasma-jet spraying or galvanic deposition (electroplating). These coats are applied on an intermediate bronze layer, which in turn is applied on a sublayer (an undercoat) formed due to exothermic reaction in the spraying process that ensures a high strength of adherence to the steel base. The sublayer with a thickness of 0.05-0.15 mm and the intermediate layer with a thickness of 0.5-0.8 mm are applied by plasma-jet spraying. In this case, the babbit coat thickness must not be more than 0.1-0.25 mm, and in the galvanic method, must b...

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Several coats, such as gray cast iron, cast iron alloyed with nickel and copper, nickel-aluminum, Nichrome (nickel-chromium alloy), bronze, etc., have been investigated. Corrosion resistance of coats in a medium based on drilling mud and sodium chloride and sulfate solutions has been checked. Alloyed cast iron admixed with tin-based compounds showed the best results.

A technology has been developed for repairing the worn cast-iron cylinder and piston in a motorized gas compressor: if the surface wear is more than 1.5 mm, sleeving is used, while with wear not more than 1.5 mm, gas-thermal coating is employed. Tests have been performed on a proposed material for plasma coating. There is a considerable increase in the working life of the repaired cylinders.Research has been done on the viability of the cylinder and piston group in an internal combustion engine (ICE), which has shown that the friction conditions in ICE cylinders are the most unfavorable when the friction surface temperature attains its maximum, i.e., about 350°C, when the thickness of the oil film becomes minimal and the oil is dispersed, where it burns up in a period of ignition and is blown out from the upper rings during compression. This leads in fact to elimination of the oil film * . One then has essentially dry friction between the cylinder, the piston rings, and the piston.More favorable lubrication conditions for the friction surfaces are required to increase the working life. To a certain extent, this can be attained by adjusting the porosity of the cylinder and piston walls, improving their wear resistance, and increasing the antifriction properties.This company has handled these tasks in the repair of worn cast-iron cylinders and pistons. The company has collaborated with organizations in the petroleum industry and has found that there is a considerable demand from the latter for repairing worn parts of compressors, in particular cylinder-piston groups. This can be handled not only by sleeving but also by using the latest technologies for reconstructing worn surfaces, including gas-thermal spraying methods.Developments in the technology for repairing worn cylinders have taken two lines: with surface wear more than 1.5 mm, by sleeving; and with surface wear not more than 1.5 mm, by gas-thermal coating.The sleeving uses cylinders cast from SCh-20 cast iron of hardness 160-180 HB. The working life of the sleeved cylinders was less than that of new ones, so it was proposed to alloy the sleeves during casting.We added 0.2-0.5% of nickel and chromium to the cast iron. This greatly improved the quality of the castings and increased the wear resistance. As a cylinder is a large component of height about 900 mm and internal diameter 355 mm, special equipment was needed to press the sleeves into place (Fig. 1).After sleeving, the cylinder was turned on a lathe and honed. The working life was much increased for cylinders installed by pressing alloy sleeves.The most complicated tasks were handled in devising the plasma coating technology. The mass of a cylinder exceeds 700 kg, and its shape is not convenient for mounting on the chuck of a lathe in the horizontal position, so a special equipment was developed for plasma coating (patent 2279904 RF). The working principle is that the cylinder is set up vertical on