Wear application of co-tic cemented carbides for gas turbines

The work offers a solution of urgent theoretical and practical problem of increase of wear resistance of GTE blades top shrouds contact faces. Implementation of current research results may increase service life of turbines. For –TiC cemented carbides manufacturing TiC-powders of grain size -20…+0.5 m were used. This provided them with combined micro and macro hardening. High strength of an alloy helps it to resist plastic deformations arising due to action of friction force. Accompanied by generating of friction induced surface structure with positive gradient of mechanical properties provides to Co-TiC cemented carbides perfect wear resistance at elevated and high temperature operatio

Features of transition modes of friction surfaces with partially regular microrelief

Textured surfaces with partially regular micro relief (PRMR) are reported to be an effective means to control lublication. It was found they are good wear debris trap and suppliers of lubricant directly to the actual friction area. Their tribological properties depend on the clearance between mating surfaces, relative slip speed, direction of motion. These parameters change the lubrication regime, and vice versa changing geometry of PRMR it is possible to predict and control lubrication regime for given conditions. Application of micro textured surface is prospective for high precision sliding units – valve slides of oil and hydraulic systems, faces of gear pump gears, ring-to-cylinder interface of aircraft reciprocating engines etc. providing high service life. On other side, changing texture parameters it is possible to stop the leakage of fluid through the gap, what may be efficiently utilized in aircraft non-contacting mechanical (hydrodynamic and hydrostatic) seals of gas compressors and gear mechanisms. This paper discloses some peculiarities of transition lubrication regimes for textured surfaces in lubricated contact

Tribological behaviour of cast cobalt-based alloys under high temperature fretting-wear

У роботі досліджено трибологічну поведінку ливарних евтектичних сплавів на основі кобальту, зміцнені карбідами ніобію та титану в умовах високотемпе-ратурного фретингу. Проаналізовано перебіг фізичних і хімічних процесів, що відбуваються на поверхнях тертя.y Titanium and Niobium carbides under high temperature fretting-wear. The temperature range of wear testing – 650-1050ºC. It was found that the main processes running on the friction surfaces are the metal deformation, grinding and destruction of carbides, deterioration of protective oxide layer, at high temperature and massive deformation galling take place. Increase of carbide phase ratio in the alloy is a proposition in order to decreases the rate of destruction of the material

Phase Equilibrium and Microstructure Examinations of Eutectic Fe-C-Mn-B Alloys

In this study, we analyzed the quaternary Fe-C-Mn-B system to create new eutectic cast alloys for coating deposition and additive manufacturing. Experimental samples were fabricated via the wire arc manufacturing method with argon shielding using Kemppi Pro 5200 Evolution equipment. Annealing was performed in a vacuum electric furnace at 1273 K for 350 h. For phase analyses, Jeol Superprobe 733 equipment was used. Metallographic and differential thermal analyses were used to reveal the eutectic structure of the samples. Examinations of the quaternary Fe-C-Mn-B system demonstrated that several eutectic alloys existed in the system. Four isothermal pseudo-ternary sections of the Fe-C-Mn-B system were studied: “Fe3B”-Fe3C-“Fe3Mn”; Fe2B-“Fe2C”-“Fe2Mn”; “Fe3B”-Fe3C-“Fe1.2Mn”; “Fe23B6”-“Fe23C6”-“Fe23Mn”. Broad eutectic concentrations enabled us to overcome parameter fluctuations during additive manufacturing. In each isothermal section, two dissimilar phase regions were determined: one with a ternary Fe-C-B composition and the other with a ternary Fe-C-Mn composition. Depending on the manganese content, two types of solid solutions could be formed: (Fe, Mn)α or (Fe, Mn)γ

WEAR APPLICATION OF Co-TiC CEMENTED CARBIDES FOR GAS TURBINES

The work offers a solution of urgent theoretical and practical problem of increase of wear resistance of GTE blades top shrouds contact faces. Implementation of current research results may increase service life of turbines. For –TiC cemented carbides manufacturing TiC-powders of grain size -20…+0.5 m were used. This provided them with combined micro and macro hardening. High strength of an alloy helps it to resist plastic deformations arising due to action of friction force. Accompanied by generating of friction induced surface structure with positive gradient of mechanical properties provides to Co-TiC cemented carbides perfect wear resistance at elevated and high temperature operatio

FUNCTIONAL PLASMA-DEPOSITED COATINGS

The paper focuses on the problem of low adhesion of plasma sprayed coatings to the substrate. The subsequent laser treatment modes and their influence on the coatingsubstrate interface were studied. This allows to decrease the level of met-stability of the coating, thus decreasing its hardness down to 11–12 GPa on the surface and to about 9 GPa on depth of 400 µm. The redistribution of alloying elements through solid and liquid diffusion improves mechanical properties and rises the adhesion up to 450 MPa after remelting and up to 90–110 MPa after laser-aided thermal cycling. At the same time, remelting of coating helps to decrease its porosity down to 1%. The obtained complex of properties also allows to improve wear resistance of coatings and to decrease friction factor

Research on the properties of Co-TiC and Ni-TiC HiP-sintered alloys

Three types of sintered alloys were fabricated based on cobalt, nickel and high-temperature alloy ZhS32-VI matrix with titanium carbide strengthening phase. TiC content was in a range of 30–50 vol. %. The melting temperatures of alloys are higher than 1320°C, and they may undergo undamaged through all technological procedures together with turbine blades, including soldering and outgassing. DSC analyses indicates no additional thermal effects until melting, which confirms their structural stability. The examinations of microstructure revealed three types of constituents – TiC particles, matrix solid solution and blow outs – structural defects having negative effects on all the studied properties. It was found that heat resistance of nickel based sintered alloys at the temperature of 1100°C is superior as compared with the alloys based on cobalt and alloy ZhS32-VI. It has been established that wear resistance in conditions of fretting wear at temperatures of 20, 850, 950 and 1050°C of sintered alloy with ZhS32-VI matrix is mostly superior as compared with the other alloys. The properties of produced alloys allow to use them for manufacturing of components of friction couples operating in conditions of high temperature fretting wear, including protective pads of turbine blades top shrouds contact faces

Fretting-Wear Mechanism of Textured Surfaces

The wear mechanism of textured dimpled in conditions of lubricated fretting-wear is established, which, in contrast to others, takes into account possibility of removing deterioration products out of tribo-contact areas into dimples, preventing their action as abrasive material. Selection of optimal structural parameters of selectively dimpled areas allows to reduce duration of tribological couple running-in time. Depending on texture type, friction coefficient was reduced from 0.27 (for untreated furface) to 0.18, and wear loss – from 7.8 ×10–3g to 3.3 ×10–3g

Duplex Aging and Gas Nitriding Process as a Method of Surface Modification of Titanium Alloys for Aircraft Applications

This study discusses the effect of a duplex aging + nitriding process on the wear resistance of an aged double-phase titanium alloy, BT22. Nitriding was applied simultaneously with the heat treatment of the alloy, which is advantageous over the conventional heat and surface treatment methods applied to titanium alloys. According to the results, the thickness of the case depth of the nitrided samples was 40–50 μm. Moreover, nitrogen was uniformly dispersed in the substrate, which was indicated by the hardness tests. The average microhardness of the substrate material was 300 HV0.01, while the hardness of the top layer was 1190 HV0.01, which is an almost four-fold increase. The applied duplex treatment substantially affected the wear performance of the tested alloy. For the untreated alloy, the maximum coefficient of friction was 0.8, while in the surface-modified sample, the maximum fluctuations reached 0.6. The abrasive wear process was dominant in the nitrided samples, while delamination and adhesive wear were observed for the untreated specimens. The nitrided alloy exhibited double the wear resistance of the untreated samples. The proposed treatment does not require additional time or energy consumption, providing a substantial technological advantage over conventional methods. Though the alpha case reduces the mechanical performance of titanium, the nitriding of only the component sections intended to withstand friction will have a positive effect