JPH1129380A - Coating of platinum onto ceramic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable coating without breakage due to N2 gas produced by decomposition of silicon nitride by precoating the surface of a ceramic part, used at high temperatures and consisting essentially of silicon nitride with alumina or zirconia before coating the surface with platinum when coating the surface with the platinum in order to impart electroconductivity. SOLUTION: A precoating 6, having preferably about 1 μm thickness and composed of alumina or zirconia is applied by a physical vapor deposition(PVD) method, e.g. sputtering or ion plating before applying a platinum coating 7 thereto. The top surface of the first layer 6 of the precoating is then coated with platinum of the second layer 7 and the thickness thereof is preferably about 5 μm. The platinum coating is preferably further coated with the third layer 8 composed of alumina or zirconia in order to protect the platinum coating 7. The thickness thereof is preferably about 10 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a gap between a high-temperature rotating component such as a turbine blade made of ceramics and a fixed component by a capacitance type sensor. A method of coating a metal to provide

[0002]

2. Description of the Related Art An axial turbine is used for a high-output and high-efficiency gas turbine such as an industrial gas turbine or an aeronautical gas turbine. In order to improve the efficiency of the turbine, it is necessary to increase the inlet temperature and the inlet pressure of the turbine.
Some inlet temperatures range from 1,300 ° C to 1,400 ° C. Since there is no metal that can withstand such high temperatures, cooled turbine blades are used, and cooling the turbine blades with compressor outlet air reduces the blade temperature by several hundred degrees below the turbine inlet temperature. However, since the use of cooling air causes a decrease in turbine thermal efficiency, it is planned that the blades be made of ceramic and used without cooling at a turbine inlet temperature of about 1,300 ° C. The material of the ceramic blade used is silicon nitride (Si3N
4) Promising.

On the other hand, in a gas turbine, it may be necessary to measure the tip clearance of a turbine blade during operation.
Hereinafter, the method for measuring the gap will be described with reference to the drawings. FIG. 2 is a side view of the vicinity of the turbine blade, and FIG.
FIG. 3A is a view taken in the direction of arrows AA in FIG. 2, and FIG.
(A) is an end view seen from the arrow BB. In these drawings, reference numeral 1 denotes a turbine disk made of metal, and a plurality of grooves 1a parallel to the turbine axis are provided on the outer periphery of the turbine disk 1. Reference numeral 2 denotes a moving blade, which includes a wing portion 2a and an implant portion 2
b, platform 2c. 2d is a wing tip.

[0004] Reference numeral 3 denotes a shroud, and 4 denotes a gap sensor of a capacitance type. δ is the tip clearance, which is the distance between the tip 2 d and the inner surface of the shroud 3. Since there is a fixed relationship between the capacitance of the gap sensor 4 and the gap δ, the gap δ can be detected by measuring a change in the capacitance. 5 is a combustion gas.

[0005]

As described above, since the gap δ is detected based on the change in the capacitance, the blade is required to have conductivity. However, ceramics such as silicon nitride have no conductivity. Therefore, not only the blade tip 2d of the silicon nitride blade but also the blade 2a and the platform 2 to ground the blade tip 2d to the metal turbine disk 1 are grounded.
c, It is necessary to apply a metal coating to the implanted portion 2b. The metal coating does not have to be the entire moving blade 2 and may be in the form of a band, or may be only on one side (ventral or dorsal side). The material of the metal coating is preferably platinum which can withstand high temperatures.

[0006] The inventors conducted experiments by coating platinum on a blade made of silicon nitride. However, 1,000 ゜ C
At moderately high temperatures, air bubbles were formed between the platinum coating layer and the surface of the rotor blade, destroying the coating, changing the value of the capacitance and making measurement impossible. . This is probably because the surface of silicon nitride was decomposed due to the catalytic action of platinum, and nitrogen gas (N2) was generated.

The present invention has been devised based on the findings of the experimental results described above, and provides a method for forming a stable platinum coating layer on a ceramic component containing silicon nitride as a main component, which is used at a high temperature. The purpose is to provide.

[0008]

In order to achieve the above object, a method for coating a ceramic part with platinum according to the present invention is to impart conductivity to the surface of a ceramic part mainly composed of silicon nitride used at a high temperature. This is a method of coating platinum, in which alumina or zirconia is pre-coated before coating with platinum.

When the parts are mounted on an actual machine and used for a long time, it is preferable to coat alumina or zirconia on platinum.

Next, since the surface of silicon nitride was pre-coated with alumina or zirconia before coating with platinum, which explains the function of the present invention, platinum and silicon nitride do not come into direct contact with each other, and therefore, A stable platinum coating layer can be obtained without generating nitrogen gas due to decomposition.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a drawing of a blade tip of a rotor blade, and is a cross-sectional view taken along the line CC of FIG. FIG. 1 (A)
Fig. 1 (B) shows a pre-coating (first layer), a platinum coating (second layer) and a protective coating. (3rd layer) is shown.

As shown in the figure, a coating is applied to the blade tip 2d and the back side of a silicon nitride blade. First layer 6
As (pre-coating), alumina or zirconia is coated. The coating thickness may be about 1 μm, and is applied by a PVD method such as sputtering or ion plating. The second layer 7 is coated on the first layer 6 with platinum. The thickness may be about 5 μm, and is applied by a PVD method such as sputtering or ion plating. The above two layers may be used for a normal test. When used for a long period of time, such as performing a test by attaching to an actual machine, a ceramic such as alumina is coated as a third layer 8 to protect platinum from corrosion by the combustion gas 5. The coating thickness may be about 10 μm, PV
Construct by D method. The coating of the third layer 8 is not performed on the implanted portion 2b below the platform 2c. Platinum coating 7 other than wing tip 2d is wing tip 2d
And has a role as a ground wire to the metal turbine disk 1. Therefore, it is not necessary to coat the entire surface of the rotor blade, and the coating may be performed only on the back side or the abdomen side, or may be a band-like coating.

The present invention is not limited to the embodiment described above, and various changes can be made without departing from the gist of the invention. That is, although the moving blade is described as an example of the ceramic component, other components used at a high temperature may be used.

[0014]

As described above, the method for coating platinum on a ceramic part according to the present invention involves pre-coating ceramic such as alumina before platinum coating.
Silicon nitride does not cause a chemical reaction at a high temperature to generate nitrogen gas, and has an excellent effect that a platinum coating layer can be formed stably at a high temperature of 1,000 ° C. or more.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a rotor blade tip (a view taken along the line CC in FIG. 2), wherein (A) shows a coating with two layers, and (B) shows a coating with three layers I have.

FIG. 2 is a side view of a rotor blade and its vicinity.

FIG. 3A is a view taken in the direction of arrows AA in FIG. 2, and FIG.
FIG. 4 is an end view taken along the line BB in FIG.

[Explanation of symbols]

 2 Blade (ceramic parts) 6 First layer coating (pre-coating) 7 Second layer coating (platinum coating) 8 Third layer coating (protective coating)

Claims (2)

[Claims] 1. A method of coating platinum on a surface of a ceramic component containing silicon nitride as a main component, which is used at a high temperature, in order to impart conductivity to the ceramic component. A method for coating platinum on ceramic parts, characterized by coating. 2. The method for coating platinum on a ceramic component according to claim 1, wherein the platinum is coated with alumina or zirconia to protect the platinum.