INVESTIGATION OF THE INFLUENCE OF PLASMA SPRAY SEALING COATINGS ON THE EFFECT OF SEALING THE TV2 - 117A TURBOJET ENGINE COMPRESSOR

This research shows the effect of the application of soft seals deposited by the atmospheric plasma spraying - APS process on the parts of the TV2-117A turbojet engine compressor. Western plasma spray technology and materials were applied for the first time on the parts of the compressor. The aim was to replace the existing sealant with a new class of materials in order to increase the sealing effect and provide air flow under the highest pressure through the compressor. Soft seals are formed as duplex systems consisting of the bonding underlayer based on NiCrAl and NiAl coatings and top sealing layer coatings based on Ni - 15% graphite, Ni - 25% graphite and AlSi - polyester. This paper presents the parameters for depositing the coatings on the compressor parts as well as the mechanical and microstructural characteristics of the coatings produced with the optimal deposition parameters. The mechanical properties of the coatings were assessed by testing the microhardness of the bonding layers using the HV0.3 method and the macrohardness of the sealing layers using the HR15W method. The tensile bond strength of the duplex coatings system was investigated by tensile testing. The microstructures of the coating layers were evaluated on an optical microscope - OM. The analysis of the microstructure of the deposited layers was performed in accordance with the Pratt & Whitney and TURBOMECA standards. Coating wear was determined from the change in the dimensions of the sealing surfaces before and after testing. The dimensions were measured in the coordinate measuring machine MAUSER ML 28. This paper presents the mean value of wear in milimeters and compares it with the values of the allowed tolerance in the compressor machined parts. The sealing effect of the compressor parts was tested on a TV2-117A engine at a test station and by flight tests on an Mi-8 (HT-40) helicopter. The tests have shown that the new system of sealing coatings increases the degree of efficiency of the compressor by 10% while reducing fuel consumption by 8%.


Introduction
Development of new generations of turbo-jet engines and a request for a higher reliability of operation and a wider choice of component resources in exploitation resulted in a wider application of plasma spray coatings. Various quality types of powders have been developed for aircraft components such as low and high pressure compressor components, gas turbine components and landing gear components (Mrdak, 2012b, pp.71-89), (Mrdak, 2013a, pp.69-88), (Vencl, et al., 2011(Vencl, et al., , pp.1281(Vencl, et al., -1288, (Mrdak, et al., 2013, pp.559-567), (Mrdak, 2014a, pp.7-22), (Mrdak, 2014b, pp.7-26). Low and high pressure compressor components of turbojet engines are coated with soft abrasive erosion-resistant coatings which cause low energy conditions of friction. During exploitation, coatings wear instead of causing blade or seam labyrinth wear. These coatings are suitable for eccentric assemblies and they compensate for the changes in machining-induced tolerances. With clearance adjustment to the lowest value, coatings improve engine performances. The precision in machining tolerance is also reflected on a significant reduction of the damage to the blades and on fuel consumption. The most commonly used abrasive coatings are: nickel -graphite, aluminumsilicon -polyester, nickel -chromium -iron and aluminum -boron nitride. The quality and resource of abrasive coatings depend on the deposition parameters (Mrdak, 2012b, pp.71-89), (Mrdak, 2013a, pp.69-88). The sealing coating systems are designed in such a way that the rotor non-axiality and the dimension changes due to temperature change are taken into account and that they wear and tear without damage to the blade tops maintaining a constant clearance (Tosnar, 1988, pp.257-262). The blade tops at high speeds must act as an effective cutting tool in order not to damage the seal or the blades. The characteristics which a material should have are good resistance to erosion from foreign particles and a good possibility of wear without damaging the blades as well as the ability to sustain working temperatures without the degradation of mechanical properties (Naser, 1988, pp.75-84). With wearable sealing systems,there is a need for the balance between material wear due to heat, final surface treatment, erosion resistance and resistance to wear. Plasma spray powder deposition parameters enable a con-trol of the given key characteristics. The plasma spray deposition process enables the control of coating porosity, density and thicknessin order to obtain sealing layers with the required characteristics (Tosnar, 1988, pp.257-262). Soft sealing coatings are formed as duplex systems with plasma spray technology. For the production of the bonding layer, NiAl, NiCrAl and NiCrAlY powders are often used (Mrdak, 2010, pp.5-16), (Mrdak, 2013b, pp.7-22), (Mrdak, 2012a, pp.182-201). The thickness of the bonding layer ranges from 0.005 to 0.15 mm and must correspond to the substrate material and the top sealing layer. The role of the bonding layer is to provide good adhesion to the substrate and good bonding with the sealing layer. The powders for soft sealing coatings contain metallic components which provide toughness to the coating as well as non-metallic components which are consumed in the process of exploitation, such as graphite, polyester and others. For the production of seals for the temperatures up to 480°C, Nigraphite powder is used due to its high resistance to oxidation, wear and sudden changes in temperature. For lower temperatures, up to 345°C, coatings based on AlSi alloy and polyester mixtures are applied. Thus formed soft sealings provide effective sealing with minimal clearance during engine operation and they reduce the loss of pressurein compressors and turbine sections. World wide research in this field has instigated the use of new materials and plasma spray technology in the process of repair of the TV2-117A turbojet engine compressor, produced in Russia. In order to achieve the set goals, the gaps between the components in the compressor must be minimal (Demasi, 1994, pp.1-9). Very good sealing reduces gas loss caused by leakage. Also, seals should provide the thermal insulation of the housing, and reduce the influence of the gas temperature in the casing (Novinski, 1991, pp.451-454), (Yi, 1999, pp.47-53). For that purpose, coatings consisting of a metallic phase and non-metallic phase for self -lubricating with high porosity are used (Oka, 1990, pp.58-67). The most important properties of sealing coatings are high resistance to wear of scraping blades and resistance to gas erosion and foreign particles present in the gas (Novinski, 1990, pp.151-157), (Yi, 1997, pp.99 -102).
The aim of the study was to use the plasma spray technology and new materials in order to examine the effect of sealing the TV2 -117A turbojet engine compressor and to replace the existing sealants during the engine overhaul. New generations of materials applied to seal parts of the engine compressor should provide a higher degree of compressor efficiency with lower fuel consumption. The requirements to be met by such materials are to provide air flow at T = 100 -125°C under the highest pressure through the compressor. The expected effects have been confirmed by 42-hour engine tests on the test station and by flight tests of an    NiCr (75%Ni,19%Cr) and 6%Al. The powder had a granulation range of -120 + 45μm (Metco 443NS Nickel-Chromium / Aluminum Composite Powder, 2000, Technical Bulletin 10-130, Sulzer Metco). Composite powder particles of Ni/Al consist of 95.5% Ni and 4.5% Al. The powder had a granulation range of-88 + 45μm (Metco 450NS Nickel / Aluminum Composite Powder, 2000, Technical Bulletin 10-136, Sulzer Metco). For soft sealing coatings intended for operation up to 480°C, Metco 307NS-1 (Ni/25% graphite) and Metco 308NS-1 (Ni/15% graphite)composite powders were used (Metco 307NS -1,Metco 308NS -1 Nickel Graphite Powder, 2000, Technical Bulletin 10-115, Sulzer Metco). Powders are manufactured by cladding graphite particles with Ni particles by the dry spray method. The powders had a range granulation of 90 + 30μm (Metco 307NS -1,Metco 308NS -1 Nickel Graphite Powder, 2000, Technical Bulletin 10-115, Sulzer Metco). To produce a soft sealing designed for operations up to 345°C, a mechanical mixture of powders AlSi12 and polyester was used. The powder consists of 60% of the Al-Si12 alloy and 40% of polyester. The powder had a granulation particles of a range of -106 + 10μm (Metco 601NS Aluminum -Polyester Powder, 2000, Technical Bulletin 10-141, Sulzer Metco). The substrate material of the samples on which the layers of the sealing coating system were deposited was made of stainless steel X15Cr13 (EN 1.4024) in the thermally unprocessed state. The testing of the mechanical properties of the coating layers was done in accordance with the Pratt & Whitney standard (Turbojet Engine -Standard Practices Manual (PN 582005), 2002, Pratt & Whitney, East Hartford, USA) and TURBOMECA standard (Turbojet engine-standard practices manual, TURBOMECA). For hardness testing and the evaluation of the microstructure of sealing coatings in the deposited state, Č.4171 (X15Cr13 EN10027) steel samples were made, with the dimensions 70x20x1.5mm. The microhardness of the NiAl and NiCrAl coating bond was tested using the HV 0.3 method and the macrohardness of Ni-15% graphite, Ni-25% graphite and AlSi12 polyester sealing coatings was tested using the HR15y method with a Rockwell steel ball of 12.7 mm in diameter and a load of 15 kg. The macrohardness of the coatings was measured along the layers. Out of five performed readings of the hardness values of the layers in the middle and at the ends of the samples, two extreme values were rejected. The three remaining values are shown in their minimum and maximum values. The samples for testing bond strength were made of the same steel with the dimensions of Ø25x50 mm. Tensile tests were carried out at room temperature on the hydraulic equipment at a rate of 10 mm/min. For each compression part,a relevant groups of samples,three specimens for each part, were made. The samples were rotated together with the compressor parts at a certain rotational speed in order to obtain the same conditions of depositing sealing coatings. The results obtained were averaged and the bond strength mean values are shown in the paper.
The microstructure of the deposited layers was examined on an optical microscope -OM. The analysis of the share of micro pores in the coating was performed by treating 5 photos at 200X magnification. The paper presents the mean values of the share of micro pores in the coating. Table 1 contains the names of the TV2-117A turbojet engine compressor parts, types of material the parts were made of as well as the working conditions for the parts with deposited new systems of sealing coatings.
The compressor consists of focusing devices of IV -IX degrees, compressor front body, compressor working rings of V degree to X degree and the air labyrinth ring made of titanium alloy intended for military aviation industry. The titanium alloy has the Russian designation OST 1 90173-75 (VT-5) and the aluminum content of 4.3-6.2% Al. The powder manufacturer, Sulcer Metko, prescribed that the powder should be deposited by its plasma spray systems labeled Metco 9M, 7M and 3M applying the prescribed deposition parameters. Therefore, the application of other plasma spray depositing systems requires that the depositing parameters must be tested and optimized. In previously published works (Mrdak, 2012b, pp.71-89), (Mrdak, 2013a, pp.69-88), the parameters for SG-100 and MINI -GUN II plasma guns of the Plasmadyne company were opti-mised using fixed samples on special tools. To obtain identical microstructures and mechanical properties of the sealing coating system on the accompanying samples and on the cylindrical parts of the compressor, the deposition of powders was performed in specially made tools for the deposition on both the compressor parts and specimens. The deposition of powders was performed under the same conditions on the samples and the compressor parts with a particular rotational speed and the plasma gun rate.
In this experiment, the atmospheric plasma system of the Plazmadayn company and the plasma gun MINI -GUN II were used. Numerous samples were made and the paper presents the optimal parameters used for depositing coatings on the compressor parts and tested on the TV2-117A turbojet engine at the test station and on an Mi-8 (HT-40) helicopter intended for flight tests. The coatings were deposited on the roughened and preheated samples and compressor parts at a temperature of 90-120°C. Because of the geometry of the parts -the focusing devices of IV -IX degrees, the front of the compressor body, the compressor work rings of V -X degrees and the air ring labyrinth -the powder depositing was done with a specially constructed plasma gun MINI -GUN II, with the dimensions Ø25 X 600 mm. The plasma gun consisted of: A 2084 -F65 anode, K1083 -129 cathode and GI2084 B -103 gas injector. The deposition of all the coatings was performed with the power supply of 40KW. The bond layers of NiCrAl and NiAl coatings were deposited with an Ar-He mixture of plasma gases, while the sealing layers of the coatings with Ar were deposited withhout the secondary plasma gas of He.
Three types of systems of sealing coatingswere made: NiCrAl/Ni -15% graphite, NiCrAl/Ni -25% graphite and NiAl/AlSi12 -polyester. In all parts, the thickness of the NiCrAl bond layers with a single pass of the plasma gun was 25μm. The thickness of the sealing Ni -15% graphite and Ni -25% graphite layers with a single pass of the plasma gun was 60μm. The thickness of the NiAl layer on the air labyrinth ring with a single pass of the plasma gun was 20 μm. The thickness of the sealing AlSi12 -polyester layer on the air ring with one pass of the plasma gun was 100 μm. Table 2 shows the plasma spray parameters of the powders deposited with a MINI -GUN II plasma gun on the focusing devices of IV degree to IX degree. The thickness of the bond layers deposited with the NiCrAl powder was from 0.1 to 0.15 mm, and the thickness of the sealing coatings made of the powder of Ni-25% of graphite was 0.65 to 0.7 mm. The sealing coating thicknesses were increased by 0.3 mm for machining purposes.
At the front of the compressor body, the thickness of the bond layers with the deposited NiAl powder was from 0.1 to 0.15 mm, and the thickness of the top layer of the sealing coating made of the powder of Ni-15% of graphite was from 0.65 to 0.7 mm. The sealing coating thicknesses were increased by 0.3 mm for machining purposes. On the compressor working rings of the V -X degrees, the bond layers of the NiCrAl coatings were deposited with a thickness of 0.15 to 0.2 mm. The thicknesses of the top sealing coatings deposited with powder Ni -25% of graphite were thicknesses of 0.8 to 0.85 mm. Also, for machining purposes, the coating thicknesses of the sealing coatings were increased by 0.3 mm.
On the air labyrinth ring, the coating bond layer is made of NiAl powder with a thickness of 0.1 to 0.15 mm, and the top sealing layer of the coating is made of AlSi12-polyester powder with a thickness of 0.6 -0.65 mm. The thickness of the sealing layer includes the additional 0.3 mm for machining purposes.
The machining of the Ni-15% graphite and Ni-25% graphite sealing coatings deposited on the compressor parts was performed using the method of coarse finishing of scuffing and fine finishing of scuffing with cutting tools -a knife with a WC plate. During the machining, no cooling of the machining surface was applied.. Table 3 shows the parameters of the machining of Ni-15% graphite and Ni-25% graphite coatings deposited on the compressor focusing device of IV -IX degrees, the compressor front body and the compressor working rings of V -X degrees.  Table 4 shows the parameters of machining the AlSi12 -polyester coating deposited on the air labyrinth ring. The machining of the coating was done by combining coarse and fine grinding finishing. During machining, the treated surface was cooled. The investigation of the coating sealing effect on the parts of the compressor was done at a test station with the operating time of the TV2-117A turbojet engine of 42 hours and on an Mi-8 (HT-40) helicopter intended for testing.
The coating wear was determined based on the change in size of the sealing surfaces before and after the testing. The measurement of the dimesions was done on a MAUSER ML 28 coordinate measuring machine at eight measuring points around the perimeter of the cylindrical parts. This paper presents the mean wear value of sealing coatings in mm, compared with the values of the allowed tolerance of machineprocessed parts of the compressor.
Results and discussion Figure 1 shows a part of the focusing device of IV to IX degrees of the TV2 -117A turbojet engine compressor on which the system of NiCrAl / Ni-25% graphite sealing coatings was deposited. The figure shows the microstructures of the bond coating (a) and the top sealing coating (b). The layers of the NiCrAl bond coating are evenly deposited on the focusing device with good mechanical properties and structural characteristics. The red arrows mark the surfaces where the system of sealing coatings was deposited. The NiCrAl bond coating had the microhardness values of 308-325 HV 0.3 . The values are above min.170HV 0.3 prescribed by the standard (Turbojet engine-standard practices Manuel, Turbomeca). The even microhardness values indicate an even distribution of oxides and pores in the deposited layers. The tensile bond strength of the system of NiCrAl/Ni -25% graphite coatings had a value of 43 MPa and is above the minimum value of 32MPa prescribed by the standard (Turbojet engine-standard practices Manuel, Turbomeca). The character of the de-struction of the coatings was the adhesion on the coating / substrate interface, which indicates the good cohesive strength of the coating lamellae. The analysis of the micrographs revealed that in the NiCrAl coating bond layers the proportion of micro pores was under 2%. The coating consists of the lamellae of the solid solution of chromium and aluminum in light blue γ -Ni (Cr, Al) nickel and inter-lamellar oxide phases of NiO, NiCr 2 O 3 , Cr 2 O 3 , CrO 3 evenly distributed on the boundaries of the lamellae of the solid solution, dark blue in color and marked with red arrows (Brossard, et al., 2009, pp.1-9), (Mrdak, 2012, pp.5-16), (Mrdak, 2012a, pp.182-201). The oxides formed during the deposition of the powder which reacts with the oxygen from the air and with the oxygen incorporated into the plasma jet from the surrounding atmosphere. In the coating layers, there are also micro pores, dark blue, marked with red arrows. In the coating layers, unmelted particles and precipitates are not present. The Ni -25% graphite sealing coating had the macrohardness values in the range of 78-83 HR15y. The hardness values were quite even, which indicates that the layers of the Ni -25% graphite coating were continuously and uniformly deposited on the bond layers. This was confirmed by the metallographic examination of the coatings. At the cross section of Ni-25% graphite coating there are no unmelted particles, micro cracks networks or macro cracks, which is of essential importance for the good functionality of coatings in exploitation. The structure of Ni -25% graphite coating is lamellar. Nickel, white, is uniformly deposited throughout the cross section, which gives good strength to the coating as well as toughness, and resistance to oxidation, corrosion and erosion. The graphite in light blue marked by red arrows is, as a solid lubricant and a means to control the porosity, uniformly distributed in the coating. It is surrounded and closed by a metal base of Ni, which is very important because it increases the resistance of graphite sealing coatings to thermal shocks. Between the Ni and graphite lamellae, there are micro pores in dark blue. The analysis of the micrographs have shown that the proportion of micro pores was 16% in the layers of Ni -25% graphite sealing coating, which is in accordance with the standards and the regulations of the powder manufacturer. Figure 2 shows the front body of the TV2 -117 A turbojet engine compressor, consisting of two halves. The red arrows mark the places on the compressor body where the systems of NiAl/Ni-15% graphite sealing coatings are deposited. Figure 2  The character of the coatings system destruction was the adhesion at the coating / substrate interface. The analysis of the micrographs of the NiAl bond coating showed that the proportion of pores was below 2%. In the layers of the Ni -15% graphite sealing coating the proportion of micro pores was 13%, which is a lower proportion compared to the Ni -25% graphite sealing coating. The microstructure of the NiAl bond coating is lamellar. The coating consists of a lamella of the solid solution of aluminum in nickel α -Ni (Al), light blue, and NiO and γ-Al 2 O 3 inter-lamellar oxides evenly distributed over the lamellae solid solution boundaries, dark blue and marked with red arrows (Knotek, et al.,1980, pp.282-286), (Mrdak, 2013b, pp.7-22), (Svantesson, Wigren, 1992, pp.65-69). Figure 3 shows the air labyrinth ring (1) and the working ring of the compressor of the V -X degrees (2) of the TV2 -117A turbojet engine.  (2) with the microstructure of the NiCrAl / Ni-25% graphite coating system Slika 3 -Prsten vazdušnog labirinta (1) sa mikrostrukturama sistema prevlaka NiAl / AlSi12 poliester i radni prsten kompresora od V -X stepena (2) sa mikrostrukturama sistema prevlaka NiCrAl / Ni-25%grafit The air labyrinth ring is marked with number 1 and the red arrows mark the surface on which the NiAl/AlSi12-poliester sealing coating system was deposited. Figure (a) Figure 2(a). The analysis of the micrographs of the NiAl bond coating showed that the proportion of micro pores was about 2%. The microstructure of the AlSi12 -polyester sealing coating consists of an AlSi12 alloy (white) which gives strength to the coating as well as resistance to erosion and provides a good bonding of AlSi12 particles with NiAl bond coating particles. The cross section of the AlSi12polyester coating does not show unmelted particles or the network of micro and macro cracks, which is very important for the behavior of the coatings during the compressor operation. The second phase of polyester which serves as a solid lubricant for wear control and maintaining a constant gap during the compressor operation is surrounded, and thus closed, by the metal base of the AlSi12 alloy. Thus formed structure of the sealing coating helps to reduce the transmission of the coating on the blades and to reduce the coating breaking or erosion. The analysis of photomicrographs of the AlSi12 sealing coating showed that the proportion of micro pores was 5%. In Figure 3 (b) it can be seen that the layers of AlSi12 and the polyester have a continuous mesh structure. The network of polyester is given in blue.
Number 2 in Figure 3 marks the working ring and the red arrows mark the surface on which the NiCrAl/Ni-25%graphite sealing coating system was deposited. The photomicrograph (a) shows the microstructure of the NiCrAl bond coating and (b) shows the microstructure of the top Ni -25% graphite sealing coating. The NiCrAl bond coating had the microhardness values of 305-331 HV 0.3 . The Ni -25% graphite sealing coating had the macrohardness values within the range of 79-84 HR15y. The NiCrAl / Ni -25% graphite sealing coating system had the bond strength value of 43 MPa. The microhardness values and tensile bond strength values are above the minimum values prescribed by the TUR-BOMECA standard (min.170HV 0.3 and 35MPa) (Turbojet engine -standard practices manuel, TURBOMECA). The structure of the NiCrAl coating layer is a lamellar microstructure described above, which consists of a solid solution of γ -Ni (Cr, Al) in light blue and oxide phases in dark blue. Between the lamellae of the substrate and the lamellae of oxide phases, there are micro pores in dark blue marked with red arrows (Brossard, et al., 2009, pp.1-9), (Mrdak, 2012, pp.5-16), (Mrdak, 2012a, pp.182-201). In the structure of the Ni -25% graphite coating,a metal network of Ni in white can be seen. Particles of graphite in light blue are evenly distributed in the Ni network. Micro pores are dark blue, clearly distinct and marked with red arrows. The analysis of the photomicrographs has shown that, in the NiCrAl coating layers, the share of micro pores was below 2%, and in the Ni -25% graphite coating layers it was 17%, which is in accordance with the standards and recommendations of the powder manufacturer.
The wear of sealing coatings after testing the sealing effect on the coatings applied on the parts of the TV2-117A turbojet engine compressor at the test station and on the Mi-8 (HT-40) helicopter intended for trial testing was less than the tolerance of the machining of sealing coatings. The wear of the Ni-25% graphite coating on the focusing devices of IV -IX degrees of the compressor motor was 0.033 mm. The tolerance of the machining of the Ni-25% graphite sealing layer in the focusing devices is 0.05 mm. The wear of the Ni-15% graphite coating on the compressor front body was 0.015 mm. The tolerance of the machining of the Ni-15% graphite sealing layer in the front body of the compressor is 0.02 mm. The wear of the Ni-25% graphite coating on the compressor working ring of V -X degrees was 0.031 mm. The tolerance of the machining of the Ni-25% graphite sealing layer in the compressor working ring is 0.05 mm. The consumption of the AlSi12 polyester coating on the compressor air ring was 0.025 mm. The tolerance of the machining for the AlSi12 -polyester layer is 0.05 mm. The wear in coatings on all parts was within the permissible machining tolerance for the top sealing layer. Low consumption of sealing coatings has enabled keeping the clearance at the lowest value which reflected to the degree of efficiency of the compressor and fuel consumption. Small wear of APS -sealing coatings increased a degree of efficiency of the compressor by 10% while reducing fuel consumption by 8%.
The research into the application of APS soft abrasive coatings on parts of the TV2 -117A turbojet engine compressor has shown that there was a significant influence of the type of technology and materials on the effect of sealing the compressor and on keeping the clearance in exploitation at the minimum value. The sealing coating systems have shown that their characteristics significantly affect the performance of the compressor during engine operation. The analysis of the structural and mechanical characteristics of the coatings in the laboratoryas well as the 42-hour testing of the compressor parts at the test station and on the Mi-8 (HT-40) test helicopter has shown the following: The layers of bond and sealing coatings in the deposited state had good structural -mechanical properties that satisfy the criteria prescribed by Pratt & Whitney and Turbomeca standards. There are no macrocracks and micro-crack networks on the surfaces of the sealing coatings. The surface of the coatings had no traces of cracks and grooves of scraping blades. Segment separation of the coating parts from the surface was not found on the sealing coatings.
The sealing coating systems had good adhesion and cohesive strength of layers in exploitation. The compressor parts did notshow the delamination of coatings, the peeling of coatings through layers or the separation of coating layers from the surface of the parts.
There is no ovality on the inner surfaces of the compressor parts, which shows even wear of sealing coatings in exploitation. The average value of wear on the sealing coating of Ni-25% graphite on the directional devices of IV-IX degrees was 0.033 mm. On the sections of the compressor front body, the average value of wear on the sealing coating of Ni-15% graphite was 0.015 mm. On the compressor working ring of V-X degrees, the average value of the wear of the Ni-25% graphite coating was 0.031 mm. The AlSi -polyester sealing coating on the compressor air labyrinth ring had wear of 0.025 mm. On all parts of the TV2 -117 A engine compressor, the wear of the sealing coatings was less than the permitted machining tolerances. Low consumption of sealing layers provided the minimum clearance and efficient sealing while reducing the loss of pressure in the compressor. This has increased the level of efficiency of the compressor by 10% while reducing fuel consumption by 8%. The results of the research show that binary sealing coatings have been successfully applied in the process of general repair of the TV2 -117A turbojet engine compressor. Svantesson, J., & Wigren, J. 1992. A Study of Ni-5wt.% Al coatings produced from different feedstock powder. Journal of Thermal Spray Technology, 1(1 Данное исследование раскрывает эффект уплотнения, нанесенного атмосферным плазменным напылением, на отдельные детали коспрессора турбореактивного двигателя TV2-117A. Впервые такой метод покрытия был применен по западной технологии плазменного напыления. С целью замены существующих уплотнительных материалов новыми классами материалов, обеспечивающих лучший эффект уплотнения и проход воздуха под высоким давлением через компрессор. Мягкие уплотнители разработаны в виде двойной системы, состоящей из нижнего слоя на базе NiCrAl и NiAl покрытия и верхнего слоя уплотнения на базе Ni -15% графита, Ni -25% графита и AlSi -полиэстера.