JPH03145502A - Erosion preventing method for turbine parts - Google Patents

Abstract

PURPOSE:To efficiently prevent erosion of turbine parts and simplify the application and repair and reduce the coal by coating the surfaces of the turbine parts used in high-temperature conditions with either one or a combination of carbides such as Cr3C2, WC, etc. CONSTITUTION:In a steam turbine, turbine parts such as nozzles or blades, etc., used in dry stream region such as high-temperature first stage, medium- pressure initial step, etc., into which steam directly flows from a boiler, are liable to cause erosion due to solid particles of oxidized scales, etc. In order to cope with this, either one or a combination of carbides such as Cr3C2, WC, TiC, SiC, NbC is applied on the surfaces of the turbine parts used in high- temperature conditions. Erosion of the turbine parts can thus be efficiently prevented, and the application and repair of the coatings can simply and cheaply be carried out.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention prevents erosion due to oxidized scale on turbine parts such as nozzles and blades used in a dry steam region in a steam turbine plant. The present invention relates to a method for preventing erosion of turbine parts.

(Prior art) In a steam turbine, turbine parts such as nozzles and blades used in dry steam regions such as the high-pressure first stage and intermediate-pressure first stage where steam directly flows from the boiler are susceptible to solid particles such as oxide scale. It is known that erosion is likely to occur.

Conventionally, high-pressure first-stage nozzles and the like have been subjected to boriding treatment, which is said to be effective as a measure to prevent erosion, as a method of preventing erosion.

(Problems to be Solved by the Invention) However, such a method of applying boriding treatment is not suitable for weld overlay repair due to easy erosion loss, because the weldability of the boriding treatment is poor.

In other words, sufficient weld build-up cannot be obtained when repairing a portion where erosion damage has occurred due to the poor weldability of the boriding treatment, making it difficult to restore the damaged portion to its original state.

For this reason, when repairs are required due to erosion damage, all parts are replaced with new ones.
It had disadvantages such as high maintenance costs, which made it economically disadvantageous.

The present invention has been made in view of the above circumstances, and it provides excellent erosion resistance and the ability to repair 71311.
11, it is an object of the present invention to provide a method for preventing erosion of turbine parts that can reduce maintenance costs.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a turbine component surface 1. used under high temperature conditions. :c, Cx, WCSTI C%S IC.

Erosion is prevented by depositing NbC carbide alone or in combination.

(Function) The present invention reproduces erosion silane by solid particles such as oxide scale, for the purpose of preventing erosion of 12C, TF4, which is a material for a nozzle blade of a steam turbine.
This was done by conducting evaluation tests while analyzing solid particle erosion and applying various surface treatments.

Regarding solid particle erosion reduction, common metallic materials, even high-strength superalloys, are the main IM of turbine components.
Although it is hard to say that it is effective as it has only the same erosion resistance as stainless steel, which is a TIN +4 material, if high hardness ceramic particles such as carbide are applied to the surface of turbine parts by a method such as thermal spraying, It was found that the hardness was Hv500 or more, and it was extremely effective. In particular, when a surface layer is formed from C13C2-based carbide among various carbide particles, after being used for several hundred hours at a high temperature of 400°C or higher, the hardness increases significantly compared to before use (hardening), solid It was found that the particle erosion resistance was further increased, and it was confirmed that this method is effective as a method for preventing solid particle erosion in turbine components used under temperature conditions of 400° C. or higher.

In addition to C, , C, the surface layer containing high hardness carbide particles such as WCSTI C does not harden at high temperatures, but has a hardness of Hv50G or more, and this itself has excellent erosion resistance. It was also found that, with this method, 4
It has also been confirmed that this method is effective as a method for preventing solid particle erosion in turbine parts used at temperatures below 00°C.

(Example) An embodiment of the present invention will be described below.

In this case, 12 of the commonly used turbine main material 11
For comparison with C, M, 75% C, , C, as carbide.
A test piece whose surface was coated by plasma spraying, 80% CO
Test piece with C2 coated on the surface by explosive spraying, 93% C1
Test piece with Ct coated on the surface by low pressure plasma spraying, 8
Test piece with 8% WC coated on the surface by plasma spraying, 8
3% (WC.

Test pieces having T and C) coated on the surface by flame spraying were prepared, and these test pieces were examined for high temperature properties and solid particle erosion properties, and the results shown in Figure 1 were obtained.

In this case, in the solid particle erosion test, iron oxide particles of the same type as boiler scale were jetted at high temperature and high speed to cause erosion in the test piece in order to reproduce the erosion of turbine parts. Specific test conditions include a temperature of 500°C and a flow rate of 4B51/8% iron oxide.
I am trying to find the weight loss of Erosilane when kg is introduced. In addition, various thermal spraying methods are used to form the surface coating of each carbide in the figure, as described above. I have to. Moreover, the percentage of each carbide is the volume percentage.

However, in Fig. 1, when looking at the hardness (Hv), each carbide coating has a hardness of Hv500 or more, but
After prolonged heating at 500° C., the hardness of the C0C2 coating increases significantly. In addition, the erosion ratio is expressed as the ratio of erosion loss divided by that of 12C and M, and for both carbide coatings, it decreased to 115 or less of 12C1 steel, confirming that the erosion reduction effect is large. . Furthermore, in the case of C, C2 arytenoid, 500℃
It can also be seen that the erosion ratio after long-time heating at 100 mL was further reduced to about 115 or less. When C,,C2 is heated at high temperature in this way, it hardens because C,,C, formed by thermal spraying decomposes due to heating.
This is thought to be due to fine dispersion due to transformation, etc.

Incidentally, in the above description, the high-temperature heating of C, C, was described in the case of 5.degree. C., but remarkable effects can be obtained if the temperature is 400.degree. C. or higher.

Therefore, according to the coating formed by C0C2,
Since significant hardening occurs when used at high temperatures, good erosion resistance is obtained and it is extremely effective in preventing erosion of turbine parts. Also, C, sC
Since good erosion resistance can be obtained in the initial state not only for WC and TC, but also for WC and TC, it is extremely effective even for turbine parts used at temperatures below 400°C.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications without changing the gist.

For example, in the above description, a thermal spraying method was used as a method for depositing carbides such as C, )C2, etc. on the surface of a component, but the deposition method is not particularly limited to this method. Further, although the above description has been made using C, scz, WC, and TIC as examples of carbides, similar effects can be expected with carbides such as s and C5NbC.

[Effects of the Invention] According to the present invention, C, C2, WC, TI C55C, Nb C are coated on the surface of turbine parts used under high temperature conditions.
Since these carbides are deposited singly or in combination, it is extremely effective in preventing solid particle erosion caused by oxidized scale on turbine parts. In addition, with this method, the construction on the turbine nozzle and blades requires melting R = 1.
This type of work is easy, as it can be done without causing changes in temperature or other changes to the base material, and can also be applied even when the nozzle is assembled, making this type of work easy. When repairing, the coating can be removed chemically or mechanically, and it can be applied repeatedly, making the repair easy and the maintenance cost low.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining one embodiment of the present invention.

Claims (1)

[Claims] Cr_3 on the surface of turbine parts used under high temperature conditions
C_2. A method for preventing erosion of turbine parts, characterized by depositing carbides of WC, T, C, S, C, and NbC singly or in combination.