The method of application of combined heat-resistant coatings

 

(57) Abstract:

The invention relates to the field of chemical-heat treatment. The method of application of combined heat-resistant coatings on turbine blades includes chromolithography in vacuum in the powder mixture, thermal vacuum processing, and then produce a vacuum plasma spraying at the inlet edges of the blades layer containing aluminum, and subsequent annealing for the final formation of a coating having the structure-phase input edge with aluminium concentration 22,5-24,0 % with the transition b + - phase in other areas of blades with aluminium concentration of 16-18 %. The technical effect is to increase the durability and reliability of components of gas turbine engines operating under variable thermo-mechanical loads and high temperature oxidation. 5 Il.

The invention relates to the field of chemical-heat treatment of metals and alloys and can be used in engineering industries for protection of parts of gas turbine engines gas from corrosion.

Known methods for producing condensation and diffusion coatings, each of which has its varieties. Most beings who condensation coatings; limited opportunities for simultaneous introduction into the coating composition of several elements for diffusion coatings /1/.

The closest technical solution is the method of applying the combined protective coating, comprising the successive application of vacuum plasma method for applying a sublayer containing a set of elements necessary to provide special properties coatings and chromolithography in vacuum in the powder mixture to saturate coverage of aluminum and chromium to ensure its heat resistance and deficiencies deposited sublayer: porosity and a low adhesion with the substrate /2/.

The coating obtained in this way, has the same composition and thickness, structure, and hence the properties of the profile of the protected blade. Practice shows that some sections of parts of the turbine blades operate in different conditions of temperature and mechanical loads. Thus, the input edges of rotor blades of gas turbines due to increased heating the most prone to oxidation.

To improve resource data plots to increase the concentration of aluminum in the coating, protecting them. However, with increased is to termostaattia cracking of the coating and material details in the colder regions, for example on the output edges of the blades of the turbines. The composition of the substrate, the applied vacuum plasma method has a chemical composition close to the chemical composition of the alloy, and therefore not effective. In addition, the underlayer coating thickness of 20 to 50 microns limits the thickness chromolithograph layer in the coating, carrying the main supply aluminum determining the resistance of the coating. The underlayer coating leads to a significant appreciation of technology.

The invention consists in increasing the durability and reliability of parts operating under conditions of variable thermo-mechanical loads and high temperature oxidation, by applying the combined protective coating which changes in accordance with the working conditions of composition and structure on the profile of the protected items.

The technical result is achieved by a method of applying a combined heat-resistant coatings on turbine blades includes: chromolithography in vacuum in the powder mixture, thermal vacuum processing, and then produce a vacuum plasma spraying at the inlet edges of the blades layer containing aluminum, and subsequent annealing for the final formation of the coating, it is asdah blades with aluminium concentration 16 - 18%. Parts parts working at slightly lower temperatures, for reasons of resistance to cracking are covered with a relatively small thickness, structure + - phases, providing significant compressive stresses in the coating. And lots of items subject to the most intensive high-temperature oxidation, the most very hot. The plasticity of the coating with a high concentration of aluminum in such conditions is quite high. On such sites it is advisable to have a thicker coating with a high content of aluminum, which is provided by sputtering vacuum plasma method.

Comparable analysis of the proposed solutions with the prototype shows that the inventive method differs significantly from the known fact that on a protected surface, refusing condensation substrate, coated with chromolithograph in vacuum powders. And in areas subject to the most intensive gas corrosion, vacuum plasma method further put a layer with a high concentration of aluminum. Subsequent annealing produces the final composition, structure and properties of heat-resistant combined coating.

In Fig. 1 provides a graph of the changes to dstanley microstructure of the protective coating on the input [a] and in other areas of the profile of the blades [b].

In Fig. 3 shows a graph of the concentration of aluminum in the coating during cyclic tests at a temperature of 1150oC.

In Fig. 4 provides a graph of the relative expansion of the diffusion zone during cyclic tests at a temperature of 1150oC.

In Fig. 5 given a graph of relative changes in thickness during the test at a temperature of 1150oC.

Graph of Fig. 1 attached to a conditional points of the cross-sectional profile of the turbine blade. In the case of homogeneous coatings resource vanes generally would be determined by the exhaustion of coating properties on the input edge. To enhance the durability of the coating on the input edge while maintaining satisfactory performance coating in other areas of the aluminium concentration increased to 24 to 26 wt.%. The microstructure of the protective coating on the input edge (Fig. 2) presents - phase and combination +- phase carbides of various types in the inner zone.

Specific example (optimal).

The proposed method of application of the combined coverage is implemented as follows. The coating applied to the blade, made of Nickel alloy. Chromolithography in vacuum in the powder mixture is coating 80 - 100 μm. The powder mixture contains 13% aluminum, 47% chromium, 50% aluminum oxide.

Then the turbine blades coated was subjected to thermal treatment on the treatment: hardening: temperature 1240oC, duration - 1 hour and 15 minutes In the heat treatment process is the formation of the optimal structure and properties of the coating in the area of the back, trough, off the edge. At the inlet edges of the blades of the vacuum-plasma method further layer applied system Ni-Al-Y with the concentration of aluminum is approximately 80%. During the subsequent diffusion annealing at a temperature of 1050oC and a duration of 3 hours the coating is formed, having the structure and phase at the input edge 22,5 - 24,0% aluminum with the transition b +- phase in other areas of the pen 16 to 18% aluminum. The proposed method of application of combined heat-resistant coatings may be implemented using any vacuum furnaces and installations that causes condensation of the coating. The method is most effective for protection against high-temperature oxidation of rotor blades of the turbines due to their high cost and the decisive impact of their resource to the resource of gas turbine engine as a whole.

Sources of information

1. Ryl, C. A. Kochetov improving the reliability of the CCD through the use of combined heat-resistant coatings on turbine blades. Structural strength of engines: proceedings of the II all-Union scientific-technical conference 14 - 16 June 1988 Kuibis. Polytech. John, 1988, 2 (prototype).

The method of application of combined heat-resistant coatings on turbine blades, including chromolithography and vacuum plasma spraying, characterized in that chromolithography carried out in a powder mixture with subsequent thermal treatment, vacuum plasma spraying is carried out after thermal processing by applying a layer containing aluminum, at the inlet edges of the blades, followed by a final annealing for the formation of a coating having the structure - phase input edge with aluminium concentration 22,5 - 24,0% with the transition b + - phase on the other sections of the blades with the concentration of aluminum 16 - 18%.

 

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