RU2078945C1 - Turbine blade, its manufacturing and corrosion protection method - Google Patents

Abstract

FIELD: gas-turbine power plants. SUBSTANCE: turbine blade has base and concave feather whose surface is covered with ceramic coat. Blade manufacturing method involves filling of casting mold with molten metal. Coat protects blade against corrosion. Novelty is that dovetailed slots are made on rod surface to receive ceramic fibers fixed to ceramic coat. Ceramic fibers are bundled and fibers or threads are helically twisted; thread is provided in metal walls of slots including screw grooves around slot. Loops of ceramic bundles are wound onto rod end distant from base so that winding turns are passed through channels in base. During blade manufacture, ceramic fiber bundles are placed on inner surface of mold and secured in the form of fins contracting at point of their fixation. Inner part of mold is made in the form of fibrous-material layer. Fibrous material sheet is used for the purpose, fibrous fins are fastened on top part of sheet and filled with molten polymer by dipping fins into it. Heat-resistant coat is made of ceramic fibers to protect blade against corrosion, and air is passed from blade through voids between fibers which displaces combustion products. EFFECT: improved corrosion resistance of blades. 26 cl, 23 dwg

Description

 The invention relates to power gas turbine units.

 Known impeller blade, assembled from sections that are fastened with a steel cable stretched in the hole inside the blade (US patent N 4389162, IPC 6 F 01 D 1/06, 1983).

Known turbine blade containing a base and a concave metal pen, the outer surface of which is coated with a ceramic coating obtained by plasma spraying of oxide ceramics [1]
A known method of manufacturing a turbine blade, including filling the mold with molten metal and directional crystallization of the casting [2]
There is also known a method of protecting a turbine blade from corrosion, including applying a ceramic coating to the surface of the pen with the formation of a dense ceramic layer, rigidly bonded to the surface [1] Before applying a dense ceramic coating, the surface of the pen is alloyed with aluminum and other elements forming a dense oxide film on the metal. This reduces the corrosion rate by weight. However, polymorphic transformations in this film and the formation of nickel oxide loosen the surface, disrupting the adhesion of the ceramic coating.

 The proposed turbine blade contains a base and a concave metal pen, on the outer surface of which a ceramic coating is applied.

 What is new is that the blade is provided with ceramic fibers, and grooves are made on the surface of the pen, in which ceramic fibers are bonded with a ceramic coating, and the wall of the groove is made with a protrusion that prevents the fibers from falling out. The wall of the groove has a C-shaped profile. Ceramic fibers are assembled into a bundle or thread, which are oriented along the groove and are made with a twist of ceramic fibers. The wall of the groove is made wavy in the direction along the groove. The groove itself is also made in the form of a wave. In particular, the gaps of the surface of the feather between the grooves are made wavy. The grooves are oriented along the feather.

 Holes are made on the surface of the pen to release gaseous refrigerant, air or steam. The ceramic coating is also made of fibers. A screw thread is made on the surface of the grooves, and ceramic fibers located in the grooves under the ceramic coating are assembled into bundles with screw twisted fibers. The thread is multi-pass, which increases its pitch and ensures the orientation of the threads along the feather.

 At the end of the pen, loops of harnesses are laid, and the ends of the loops partially cover the side surface of the pen. At the base of the blade, channels are made through which bundles are passed, forming loops laid along a helical line.

 The proposed method for manufacturing a turbine blade includes filling a mold with molten metal.

 What is new is that before filling the mold on its inner surface, ceramic fibers or twisted bundles of ceramic fibers are placed and these fibers or bundles are fixed in the form of ribs, the profile of which is narrowed at the location of the rib. Previously, the inner surface of the mold is covered with a layer of fibrous material.

 Ceramic fibers or strands of ceramic fibers are fixed on one side of the auxiliary sheath of fibrous ceramic material before they are placed on the inner surface of the mold, then this side of the sheath is coated with a layer of fusible material with the fibers or bundles completely immersed in this layer, the sheath is fixed with the specified layer on investment casting model, and the outer side of the shell is fixed with a rigid matrix with non-stick coating, after which the casting model is melted together with low-melting substance and molten metal is poured into the resulting cavity of the matrix.

 As the shell, a flat sheet of fibrous ceramic material is used, and the fibers or bundles are fixed on the upper side of the sheet and filled with a melt of low-melting substance. In another embodiment of the method, ceramic fiber bundles are inserted into the grooves of the casting investment casting model, the model is covered with a layer of fibrous ceramic material that is fastened internally with bundles and fixed outside, after which the model is removed by heating, and molten metal is poured into the cavity formed.

 In this case, as a layer of fibrous ceramic material, a blank of ceramic fiber coating of the pen is used and a layer of fibrous ceramic material is left on the finished casting.

 The proposed method of protecting the turbine blades from corrosion involves applying a ceramic coating to the surface of the pen.

 What is new is that the coating is made of ceramic fibers, with the formation between the last pores through which gaseous refrigerant is passed from the blade into the flow part of the turbine. Before using the blades in the turbine, a feather with a ceramic fiber coating is placed in a gaseous medium containing alloying elements. The fibrous coating is made of layers differing in porosity, and a layer with a higher porosity is placed between the metallic surface of the pen and the layer with lower porosity. The outer surface of the ceramic coating is formed by fibers oriented across the pen. Ceramic fibers are based on alumina.

 The combination of the ceramic fiber coating with ceramic tows fixed in the grooves of the feather blade provides non-adhesive adhesion of the ceramic to the metal. Such a fixation of the heat-shielding coating cannot be violated by oxidation of the metal surface, as well as by the difference in thermal deformations of the metal and ceramics. This significantly increases the reliability of the coating and makes it possible to repeatedly increase its thickness.

 The inclusion of ceramic tows in the ribs of the mold provides automatic placement of these tows in the grooves of the turbine blades. In addition, the bundles facilitate the extraction of ceramics from the grooves, for example, if additional processing of the grooves and the installation of new bundles are necessary.

When pouring metal onto twisted bundles, the screw relief of the bundle is imprinted on the groove wall in the form of helical grooves. This creates a thread in the groove that prevents longitudinal movement of the tow. The profile of the screw grooves is rounded. Due to this, they do not cause a significant concentration of stress when the deviation of the groove from the axis of the tow to 30 ^o . The twisting of the tourniquet in the groove is prevented by the ceramic coating bonded to the tourniquet.

 The preliminary placement of the bundles in the form of ribs on a sheet of ceramic material facilitates the subsequent fixation of the bundles on the mold. Further simplification of the technology is achieved by filling the ribs with a layer of polymer with the formation of a flat surface. The resulting layered sheet material can be glued to a smooth casting model, also made of polymer. This way eliminates the need to grind grooves for each bundle in the model. The grooves with the bundles placed in them are glued onto the model together with a polymer layer, which becomes part of the model and is subsequently smelted with it. At the same time, the bundles remain permanently bonded with ceramic sheet material, which can be used as a heat-protective coating on the finished casting of a turbine blade.

 Figure 1 shows a turbine blade, a General view with a longitudinal section; figure 2 cross section aa in figure 1; in Fig.3 node 1 in Fig.2 (enlarged); in Fig.4 option node 1 in Fig.2; in Fig. 5, view B in Fig. 4, wavy grooves with a remote coating; Fig.6 embodiment of the shape of the grooves; in FIG. 7 section of the casting model of a turbine blade; on Fig section of the mold with a cut across the harnesses; in Fig.9, view B in Fig.8; figure 10 diagram of the electrolytic extension of the sides of the groove; 11.18 successive stages of manufacturing a turbine blade; 11, the orientation of the tow relative to the sheet of ceramic fiber material; Fig.12 fixing the tourniquet on the sheet in the form of ribs; in Fig.13 alignment of the relief of the sheet by filling the ribs with a layer of polymer; on Fig. fixing sheet on the model; on Fig the formation of a slip shell on a model with a sheet; on Fig melting model and pouring molten metal into the shell; on Fig. curing metal and removing the shell; on Fig. removal of sheet material to access the harness; on Fig mill to obtain a groove under the tourniquet; on Fig milled groove in the model; in Fig.21 view G in Fig.20; on Fig groove with helical grooves in the turbine blade; in Fig.23 view D in Fig.22.

 The turbine blade includes a base 1 and a feather 2, on a metal rod 3 of which a ceramic coating is applied 4. The feather has an input edge 5, an output edge 6, a convex back 7, a concave trough 8, a root part 9 and a free end 10 on which the end 11 is located the rod. The base includes a shelf 12 and a Christmas shank 13.

 In the rod and base are made collectors 14, 15 of an air cooling system, as well as collectors 16, 17 connecting a number of 18 channels 19, 20, 21 of a liquid cooling system. On the surface 22 of the rod, longitudinal grooves 23, 24 are made, in which bundles 25, 26, 27, 28 of ceramic fibers 29, 30 are located. The sides of the grooves are made with protrusions 31, 32, preventing the bundles from falling out. The bundles are twisted with the formation of turns 33, 34 of ceramic fibers. The bundles in the grooves are sealed with ceramic concrete 35 with fibrous filler.

 The heat-protective ceramic coating is formed by sheets 36, 37 of ceramic fabric, which are interspersed with sheets 38, 39 of non-woven ceramic material. The fabric includes warp threads 40 and weft 41. The nonwoven fabric comprises threads 42 oriented along the flow of combustion products and forming the firing surface 43 of the pen. The ceramic coating is bonded to the plaits located in the grooves, ceramic binder, located in the throat of 44 grooves.

 The groove 45 made on the back is connected to its corresponding groove 46 made on the trough, a channel 47 made inside the base. In the grooves 45, 46 is a continuous tourniquet 48, forming a loop 49, which bends around the base of the blade along the channel 47.

 Similarly, to other pairs of grooves, 50 and 51, 52 and 53, loops 54, 55 correspond. A continuous bundle forms a winding 56 with turns 57, 58, which bend around the tip 11 of the feather shaft and hold the fiber ceramic coating 4 attached to the turns.

In a further embodiment of the turbine blade (FIGS. 4, 5), the grooves 59, 60, 61 are made wavy with a maximum angle of deviation from the average direction α = 20 ^° . The depressions 62 and the bulges 63 of the wavy groove are oriented across the pen shaft along the perimeter of the shaft profile. The cross-section of the groove is in the form of a circle 64, which is truncated with the formation of a throat 65 extending to the side surface 66 of the rod. The throat has blunt edges 67, which are made wavy, as well as the inner wall 68 of the groove.

 In the bottom 69 of the groove, openings 70 can be made with an extension 71 for supplying air under the ceramic coating from three layers of fibrous material 72, 73, 74. The middle layer 73 of the coating is sealed with fibrous-reinforced concrete and separated from the surface 66 of the metal rod by a less dense layer of fibrous material 74. Moreover, of all layers of the coating, the middle layer provides air with maximum gas-dynamic resistance, which contributes to the formation of an air cushion above the metal surface. An air cushion protects the blade metal from corrosion in the combustion products.

 By slowing the air exit from the blade into the turbine flow path, the sealed middle layer of the coating increases the radius of action of the outlet 70 in the sense that it provides air to a larger area of the metal surface.

 The location of the sealed layer 73 between the layers 72, 74 of the fibrous material protects it from destruction and, in addition, allows you to fix the gap between it and the metal of the blade. All layers can be made of oriented ceramic fibers, such as ceramic fabric or non-woven material, in which the warp fibers are bonded to weft fibers. The fastening of the coating layers between themselves and with bundles in the grooves of the scapula is provided by a ceramic binder, which acts as a high-temperature glue. The fastening of the layers together can be enhanced by stitching them with ceramic fibers. Stitching can be done before coating the blade.

 In another embodiment, the turbine blades of the wall 75 of the groove are straight and the edges 76, 77 of the throat are wavy, with a protrusion 78 that keeps the tourniquet 79 from falling out of the groove.

 The manufacture of grooves for harnesses can be carried out in various ways. By casting, the grooves can be obtained, for example, by means of a mold, on the wall 80 of which longitudinal ceramic ribs 81 are fixed. The ribs are made of a ceramic bundle 82 coated with a ceramic binder 83. A tubular casing 84 of a ceramic binder with a fibrous filler may be formed around the bundle. After the casting has cured and the mold has been removed, the bundles remain in the grooves. It is possible to remove the harness from the groove and replace it with another harness, as well as the use of auxiliary harnesses specially embedded in the grooves to facilitate the subsequent cleaning of the grooves from the ceramics after casting. The need for cleaning arises from the additional processing of the grooves - drilling holes and applying an anti-corrosion coating.

 Using the plaits fixed in the grooves, the heat-shielding coating can be fixed on any part of the feather blade. The engagement of the bundles with the grooves is also sufficient to hold the cover 85 on the shelf 12 of the blade.

 For the manufacture of a mold using a model 86 of the blade made of low melting plastic. The proposed variants of a method for manufacturing a turbine blade differ in the operation of embedding the bundles in the model. Termination can be carried out: 1) by milling the grooves in the model and pressing the bundles into grooves, 2) by pre-filling the bundles with a layer of polymer and applying the resulting film to the model.

 In the first embodiment of the method, grooves 87 are implemented in the model with side protrusions 88 forming a gap 89. In the grooves, bundles 90 with a fibrous core 91 and an outer layer of ceramic binder, into which a fibrous filler is added, are inserted. A layer 93 of ceramic fiber material is applied to the model. Ceramic binder fastens layer 93 with bundles 90. The model coated with layer 93 is embedded in ceramic matrix 94. The material of the model is melted and a cavity is obtained whose inner surface is covered with wavy ribs 95 containing bundles. Nickel alloy is poured into the cavity. After curing, the matrix is removed.

 The separation of the matrix can be facilitated by a non-stick coating 96, which is previously applied to the outside of the layer 93. It is also possible to apply a non-stick coating 97 to limited areas of the inner side of the layer 93 to reduce the roughness of the casting.

 Instead of a shaped groove, initially, grooves 99 with straight sides 100 can be made in the pen shaft 98 of the pen, which are then expanded by electrolytic deposition of the metal to form protrusions 101. To do this, the surface of the pen is temporarily covered with an insulating polymer film 102, and an insulating polymer rod 103 is inserted into the groove ( figure 10).

 In a second embodiment of the method, a bundle of ceramic fibers 105 is oriented along a sheet 106 of fibrous ceramic material with a non-stick coating 107 applied to the back of the sheet (FIG. 11). The harnesses are fixed on one side 108 of the sheet with a jumper 109 made of ceramic concrete 110 with fibrous filler (Fig. 12). The tow and web form a rib 111 on the surface of the sheet 106. At this stage, the sheet and rib can be coated with an additional non-stick layer 112.

 Many harnesses are fixed on one sheet with the formation of a ribbed relief. In the position of the sheet, upwards, it is poured with its layer 113 of thermoplastic polymer until the smooth surface 114 closes above the ribs (Fig.13). By this surface, the sheet is glued to model 115 of the same polymer (FIG. 14). In such an augmented model, a slip shell 116 is formed, which, after drying, is embedded, together with the model, in a matrix 117 of sand (Fig. 15), filled into the flask.

 The model is melted and molten metal 118 is poured into the shell (Fig. 16). After the curing of the metal in the form of a blade with a pen shaft 119, the shell 116 and the non-stick coating 107 are removed (Fig. 17). The harnesses 104 form grooves 120 in the metal and remain bonded to the sheet 106 of fibrous material, which acts as a heat-shielding coating. If necessary, access to the surface 121 of the pen shaft of the sheet 106 is torn off the harnesses (Fig. 18). The gap occurs on the jumper 109 without breaking the harness. A more accurate separation of the sheet 106 is feasible with a plastic blade or file inserted in the form of a wedge between the sheet 106 and the surface 121 of the rod. The jumper harness is reusable by re-gluing new sheets 106 instead of damaged ones.

 The grooves obtained in the blade by the described methods differ in cross-sectional shape. Machining gives a groove with smooth walls, pouring the bundle with polymer gives a groove with internal threading. For machining, a shaped cutter 122 is used, which includes a spherical head 123, a cylindrical rod 124 and a removable clip 125 (Fig. 19). With a milling cutter, Ω-shaped grooves 127 with protrusions 128 at the edges of the slit 129 and with an extension 130 inside the groove are machined in the model 126 (Fig. 120, 121).

 The cutter is introduced into the groove 127 through the hole 131 in the middle of the groove or through the end face 132 of the processed model. In contrast to the milled grooves, the grooves 133 obtained by casting the bundles with metal have helical grooves 134, 135 forming a multi-thread. The grooves are truncated by a slit 136 with smooth edges 137 (Fig.22, 23).

 Along with the holes 70 in the bottom of the grooves (Fig. 5), the holes 138 for discharging air can also be made in the spaces 139 between the grooves. The jumpers 109 can be sewn with fibers to the bundles 104 before fixing the bundles on the sheet 106 (Fig.12). The role of fibers 105 in bundles 104 can be performed by filaments of fibers.

In the manufacture of a turbine blade, the following materials are used. The core of the pen and the base is a casting nickel alloy with directional crystallization, for example ХН65КМВЮТ (6С6К) with a temperature of long-term use up to 900 ^o C; bundles and a coating of microglass crystal fibers with a content of 95% alumina and a temperature of long-term use of 1400.1600 ^o C; a ceramic binder concentrated aqueous suspension of aluminum oxide with a colloidal component content of 50.100 g / l, is subjected to cold sintering by drying at 100 ^o C and subsequent heat treatment by heating to 1300 ^o C on a cooled blade in stationary conditions, for example on a stationary turbine rotor; ceramic concrete - ceramic binder with filler from chopped alumina fibers; model of the blade low molecular weight polystyrene hardening below 80 ^o C; foundry shell slip made of zircon or silica.

Fibers and suspensions of ceramics of other compositions, for example, zirconium oxide stabilized with yttrium oxide, can be used to work up to 1600.1800 ^o C, as well as an astringent in the form of a colloidal solution of aluminophosphates.

 The blade of the first stage of the gas turbine has a feather length of 30.200 mm and a profile chord of 20.150 mm. Fiber diameter 10.50 μm; rope diameter and maximum groove width d 0.2.2 mm; groove throat width 0.6.0.8 d; pitch wavy groove 1.5 d; the gap between the grooves is 1.3 d. Coating thickness of sheet fibrous material 0.5.3 mm; 5.30% porosity; a densified layer in the form of ceramic paper may be included in the coating.

 During the operation of the turbine, the flow of combustion products flows around the profile of the feather blade. Due to the high-pressure head, the flow presses the sheet fibrous coating material against the metal, provided that the elements of this material do not extend beyond the boundary layer. Otherwise, the coating excites the formation of vortices and is destroyed during vibration. The bundles attached to the sheet coating keep it from lateral displacement into the flow and from longitudinal displacement under the action of centrifugal force. The transverse exit of the bundles from the groove is prevented by the protrusions 31, 32 on the walls of the groove. The longitudinal displacement of the bundle along the straight groove is prevented by adhesion to the screw grooves 134, 135. The adhesion can be enhanced by adding ceramic concrete to the groove, which hardens in the form of a porous fibrous mass filling the gaps between the groove wall and the bundle.

The most loaded part of the ceramic coating is a jumper 109 made of fiber-reinforced concrete. When the thickness of the fibrous coating of aluminum oxide is 2 mm, its surface density does not exceed 0.8 g / cm ² . At a speed of 50 s ^-1 and an average radius of the turbine stage of 1 m, the overload is 10 ⁴ , and the average shear stress in the ceramic coating under these conditions does not exceed 0.8 MPa. In the jumpers, occupying 1/3 of the surface under the coating, this corresponds to a shear stress of 2.4 MPa. When the diameter of the tow 1.2 mm, the maximum pressure on the turns of the groove 134 (Fig.23) is limited to 10 MPa.

In the tow, jumper and coating, these stresses are perceived by alumina fibers, the tensile strength of which at 1400 ^o C exceeds 300 MPa.

 In the wavy groove (Fig. 5), the longitudinal displacement of the bundle along with the friction force on the groove wall is also prevented by the engagement of the bridge over the edge 67, which can be rounded. The connection of the tourniquet with a sheet coating fixes the bends of the tourniquet in the groove and creates an analogue of gearing, when one of the elements of the gear pair is a rigid bend of the tourniquet, and the other is a rigid bend of the groove. In addition to the wavy shape of the groove, helical grooves can be made inside it, as in a direct groove (Fig. 23).

 The proposed methods for the manufacture of a turbine blade allow combining the application of a heat-protective ceramic coating with a metal casting. This greatly simplifies the manufacture of the blade and improves its thermal protection, however, it gives the product without an anti-corrosion metal coating.

 Upon receipt of the heat-protective coating in a known manner by plasma spraying, the surface of the blade must be alloyed with metal before applying the ceramic layer, since the adhesion of the ceramic blocks the access to the metal substrate.

 In the proposed turbine blade, the ceramic coating is non-adhesive, that is, does not occupy a fixed metal surface. This allows, in contrast to the known methods, to alloy the metal after applying the ceramic coating through the pores of the fibrous ceramic.

For example, to alite, a turbine blade with a fibrous ceramic coating is placed for 2 hours in an atmosphere of gaseous aluminum chloride at 800. 1000 ^o C with superimposed pressure fluctuations from the outside to mix the gas in the pores of the coating. Shielding the workpiece with a porous layer is common in the practice of alitizing, since in many cases, alitizing is performed from a layer of powder sprinkled on a metal.

 Small displacements of ceramic fibers relative to the metal occurring during temperature fluctuations or during mechanical action on the coating improve the delivery of the alloying element to the metal. Chromium plating, silicification and other types of diffusion doping are also feasible through the fibrous coating. Moreover, due to the chemical resistance of alumina, the composition of the coating during the alloying process does not change.

 In the proposed design of the turbine blades implemented a new way to protect the blades from corrosion. The air discharged through the pores of the fibrous ceramic coating displaces the combustion products from the metal of the blade. The diffusion of combustion products to the metal occurs in the oncoming flow.

 Carbon oxides coming from the combustion chamber oxidize the metal and form volatile carbonyls; sulfur and sodium compounds give a fusible eutectic of sodium and nickel sulfates; Vanadium anhydride catalyzes the oxidation of metal, combines with chromium oxide.

 The air velocity can be set by the parameters of the holes 70 in the metal core of the pen or by the parameters of the pores in the fibrous coating. In the first case, the main pressure drop falls on the rod, in the second on the coating. Since the rate of air outflow is set, a pressure drop that facilitates the release of air to the outside exists in the coating in both cases. Its value depends on the ratio of gas-dynamic resistances of the rod and coating connected in series. The first case is more favorable for the strength of the coating, since it provides an air outlet with a sufficiently small load on the coating from the inside, for example 0.01 MPa, which is compensated by a slight deflection of the coating in the interval between the places of its fastening on the bundles.

 In addition, with a uniform fibrous coating, changing the diameter and number of holes 70 in the pen shaft along the profile allows reproducing the pressure drop along the flow in the interscapular channel, reaching 0.3.0.5 MPa between the inlet and outlet edges of the pen.

 Known blades with defensive cooling do not have a heat-shielding coating and an air sheet formed on their surface by the expiration of air from the pores of the metal is included in the turbulent flow of the interscapular channel. Combustion products penetrate the metal of the scapula through an air veil by turbulent diffusion, the speed of which is several orders of magnitude higher than the molecular diffusion speed. Under such conditions, air cools the blade, but is not designed and not effective for protecting it from corrosion.

The fibrous ceramic coating of the proposed turbine blade creates a zone of laminar motion and molecular diffusion in the pores between the fibers. Laminar outflow of air from the scapula stops the oncoming molecular diffusion of the combustion products. This process follows the equation
D (∂c / ∂x) = -vc, 0≅x≅a, c (O) = c _o , (1)
where D is the diffusion coefficient of particles of a certain substance in air;
c particle concentration;
c _{o the} value of the concentration on the fire surface of the coating;
x coordinate by coating thickness;
a coating thickness;
v average air flow rate in the pores of the coating.

In the fibrous coating, a temperature difference ΔT of T is established, for example from 850 ^o C on the metal surface to 1400 ^o C on the fire surface of the coating, or ΔT / T _o = 0.4 with respect to the average absolute temperature of the coating T _about 1398 K. With appropriate accuracy (20.40%), sufficient for qualitative conclusions, we can neglect the temperature change over the coating thickness and consider the parameters D and v of equation (1) to be constant and equal to their value at an average temperature. With the same approximation, one can neglect the influence of the shape of the pores on the diffusion coefficient and assume that diffusion occurs normal to the surface of the metal, and fluctuations in the air velocity in the pores caused by pressure fluctuations in the turbulent flow are insignificant.

Then the concentration of the combustion product decreases from the firing surface in a stationary exponent,
c (x) c _о exp (-vx / D), (2)
and makes up on the surface of the metal
c (a) c _о exp (-va / D), (3)
moreover, the sudden expansion of the pore near the metal, due to the non-adhesive nature of the coating, does not affect the concentration, since it is continuous.

Example. D 3 cm ² / s (CO ₂ and CO in air at 1400 K), a 0.2 cm. To reduce the concentration by 2.7 times (e), a speed of v 3 cm ² s ^-1 / 0.2 cm 15 is required cm / s, and to reduce by 100 times (≈e ⁵ ) the speed is v 75 cm / s. With a porosity of θ = 0.2 (20%) of the coating, the average air flow rate over the surface of the coating corresponds to a speed of θv = 0.2 • 75 cm / s = 15 cm / s, which is small compared to the gas velocity in the interscapular channel, 300.800 m / from.

 In contrast to porous cooling, corrosion protection can be achieved by an arbitrarily small air flow rate by reducing the porosity of the coating. A decrease in the concentration of combustion products at the surface of the metal of the blade reduces the corrosion rate by approximately the same amount.

 The similarity between diffusion and thermal conductivity under these conditions is broken. With a decrease in porosity, the fraction of heat transferred by ceramics, which does not participate in diffusion, increases.

 No matter how small the concentration of the reagent at the metal surface, its value determines the reaction rate and, accordingly, the required rate of air flow, while small changes in temperature are not significant for the temperature gradient and the magnitude of the heat flux.

 Reducing the aggressiveness of the environment in the air-ceramic cushion and enhancing thermal insulation reduce the requirements for the chemical resistance of the metal of the blade. In addition, for the same medium and temperature, the transition to a non-adhesive ceramic coating allows one to do this only by refusing adhesion by aluminizing without alloying with refractory elements and platinum.

 The lock grooves 23, 24 (Fig. 3) of the dovetail type can be filled in place of tows with amorphous pulp in the form of ceramic concrete, from which in this case the outer fibrous coating is also made 4. Such a coating with ribs for fixing in grooves can be made separately, for example, in the form of a corrugated sheet material, and used as the inner part of the mold when casting the pen shaft.

 Repeated application of the fibrous ceramic coating on the finished rod with empty grooves can be done using a combustible cover, which is coated from the inside with a layer of fresh ceramic concrete and put on the feather rod, if necessary, in vacuum. This is accompanied by the filling of the locking grooves and the formation of a fibrous coating with a smooth outer surface bounded by a cover, which is then removed by heating the blades in an oxidizing environment.

Claims (26)

 1. A turbine blade containing a base and a concave metal feather, on the outer surface of which a ceramic coating is applied, characterized in that the blade is provided with ceramic fibers, and grooves are made on the surface of the feather, in which ceramic fibers are bonded with a ceramic coating, wherein the groove wall made with a protrusion that prevents the loss of fibers.  2. The blade according to claim 1, characterized in that the groove wall is made with a C-shaped profile.  3. The blade according to claim 1, characterized in that the ceramic fibers are assembled into a bundle or thread, oriented along the groove.  4. The blade according to claim 3, characterized in that the tow or thread is made with a twist of ceramic fibers.  5. The blade according to claim 1, characterized in that the wall of the groove is made wavy in the direction along the groove.  6. The blade according to claim 1, characterized in that the grooves are made wavy.  7. The blade according to claim 6, characterized in that the gaps of the surface of the feather between the grooves are made wavy.  8. The blade according to claim 1, characterized in that the grooves are oriented along the feather.  9. The blade according to claim 1, characterized in that openings are made on the surface of the pen for discharging air.  10. The blade according to claim 1, characterized in that the ceramic coating is made of fibers.  11. The blade according to claim 1, characterized in that on the surface of the grooves a screw thread is made, and ceramic fibers are assembled into bundles with screw twisting of the fibers.  12. The blade according to claim 11, characterized in that the grooves are oriented along the shaft of the pen.  13. The shoulder blade according to paragraphs. 1 and 3, characterized in that at the end of the pen placed loops of harnesses.  14. The shoulder blade according to paragraphs. 1 and 13, characterized in that the base is made of channels through which the bundles are passed, forming a loop.  15. The shoulder blade according to paragraphs. 15, characterized in that the loop loops are laid along a helical line.  16. A method of manufacturing a turbine blade, comprising filling the mold with molten metal, characterized in that before filling the mold on its inner surface, ceramic fibers or twisted bundles of ceramic fibers are placed and these fibers or bundles are fixed in the form of ribs, the profile of which is narrowed in place fixing the ribs.  17. The method according to p. 16, characterized in that the inner surface of the mold is covered with a layer of fibrous material.  18. The method according to p. 16, characterized in that the ceramic fibers or bundles of ceramic fibers before being placed on the inner surface of the mold are fixed on one side of the auxiliary shell of fibrous ceramic material, then cover this side of the shell with a layer of fusible material with complete immersion fibers or bundles in this layer, fix the shell with the specified layer on the investment casting model, and the outside of the shell is fixed, after which the casting model is melted together with the layer easily fusible substance and molten metal is poured into the resulting cavity.  19. The method according to p. 18, characterized in that as a shell using a flat sheet of fibrous ceramic material, and the fibers or bundles are fixed on the upper side of the sheet and fill them with a melt of fusible substance.  20. The method according to p. 18, characterized in that bundles of ceramic fibers are inserted into the grooves of the casting investment casting, the model is covered with a layer of fibrous ceramic material, which is fastened from the inside and bundles, and fixed from the outside, after which the model is removed by heating and into the formed molten metal is poured into the cavity.  21. The method according to PP. 17 and 20, characterized in that as a layer of fibrous ceramic material use a blank of ceramic fiber coating of the pen and leave the specified layer of fibrous ceramic material on the finished casting.  22. A method of protecting a turbine blade from corrosion, comprising applying a ceramic coating to the surface of the pen, characterized in that the coating is made of ceramic fibers with the formation between the last pores through which air is passed from the blade into the flow part of the turbine.  23. The method according to p. 22, characterized in that before using the blades in the turbine, a feather with a fibrous ceramic coating is placed in a gaseous medium containing alloying elements.  24. The method according to p. 22, characterized in that the fibrous coating is made of layers of different porosity, and between the metal surface of the pen and the layer with lower porosity have a layer with a higher porosity.  25. The method according to p. 22, characterized in that the outer surface of the ceramic coating is formed by fibers oriented across the pen.  26. The method according to p. 22, characterized in that the ceramic fibers are made of a material based on aluminum oxide.

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