JPS62165508A - Turbine blade - Google Patents

Abstract

PURPOSE:To ensure excellent resistance to erosion in a turbine blade made of titanium family alloy by fixing an erosion shield plate, on which a case is produced by means of both Ni plating and nitriding, at least on the blade tip leading edge. CONSTITUTION:An erosion shield plate 2, on which a case 2a is produced, is welded to the blade tip leading edge of a turbine blade 1 made of titanium family alloy. In this case, the erosion shield plate 2 is made of titanium family alloy formed separately from a turbine blade member. And the erosion shield plate 2 is plated with Ni, the thickness of which is approximately, for example, 100mum or more, besides, after a diffusion layer of Ni is formed thereto by heating, the case 2a is produced through forming a nitrided layer by means of ionitriding and the like. And the weld zone of the turbine blade 1 is masked so that no case is produced, then the erosion shield plate 2 is welded to said weld zone.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a turbine blade, and more particularly to an improvement in a turbine blade made of a titanium-based alloy.

[Technical background of the invention and its problems]

In recent years, as power generation efficiency has improved, longer turbine blades have become necessary on the low-pressure side of steam turbines, and the properties required of materials have become more severe.

Conventionally, 12Cr steel has been used as a material for steam turbine blades, but 12Cr steel lacks strength under the above-mentioned constraint conditions, and the load on the rotor becomes excessive, making it difficult to apply to future larger scale applications. Met.

For these reasons, titanium alloys with high specific strength (strength/specific gravity) are increasingly being applied to blade materials. In other words, the strength of the titanium alloy is comparable to that of conventional 12Crl, and furthermore, since the specific strength is high, the centrifugal force caused by the rotation of the shaft is reduced, and the problem of overload on the rotor is also eliminated. In this way, titanium alloys will be practically effective as blades become longer in the future.

- In the low-pressure section, erosion damage due to high i collisions of condensed water droplets contained in the steam flow during operation is significant, so when conventional 12Cr steel is used as the turbine blade material, Stellite alloy with excellent erosion resistance is used. The leading edge of the wing tip is protected by brazing or welding as an erosion shield.

However, when the above titanium alloy is used as a turbine blade material,
When Stellite is used as the erosion shield plate, the strength of the joint is insufficient when brazed, and the joint tends to become brittle when welded, both of which pose problems in use.

[Purpose of the invention]

In view of the above points, an object of the present invention is to obtain a turbine blade having excellent erosion properties by fixing an erosion shield plate on which a hardened layer is formed to at least the leading edge of a blade tip of a turbine blade.

[Summary of the invention]

In order to achieve the above object, the present invention provides a turbine blade made of a titanium-based alloy, in which an erosion shield plate is provided with a hardened layer formed by N1 plated erosion and nitriding treatment. It is characterized by being fixed to the leading edge of the wing tip.

[Embodiment of the Invention] FIG. 1 is a perspective view showing an embodiment of a turbine blade according to the present invention, and FIG. 2 is a plan sectional view of the main part. In these drawings, an erosion shield plate 2 on which a hardened layer 2a as described later is formed is welded to the leading edge of a blade tip of a turbine blade 1 made of a titanium-based alloy. By the way, the erosion shield plate 2 is made of a titanium-based alloy and is formed separately from the turbine blade material by machining or precision forging, and the hardened 1iW2a is formed on the erosion shield plate 2 as follows. ing.

That is, the erosion shield plate 2 is plated with Ni to a thickness of about 100 μm or more, for example, by N1 plating, and then heated at 900 to 1200°C for 20 to 150 hours to coat the plate with N1.
After forming the diffusion layer of i, a nitrided layer is further formed using ammonia, ion nitriding, or the like. In this case, turbine blade 1
The welded portion of the leading edge of the blade tip is masked so that the hardened layer 2a is not formed. After forming the hardened layer 2a in this way, the erosion shield plate 2 is attached to the turbine Ii.
E8. It is fixed by TIG or laser welding. After welding in this way, 600~7
By performing stress relief at 50° C. for 1 to 8 hours, a hardened layer 2a with high strength and toughness is formed at the leading edge of the blade tip of the turbine blade 1. In addition, if a β-type titanium alloy is applied to the leading edge of the blade tip of the turbine blade 1, an additional 30
By performing aging treatment at 0 to 500°C for 30 minutes to 6 hours, hardness equivalent to that of stellite with a base material strength of 400 to 500 Hv can be obtained.

By combining diffusion treatment, nitriding, and aging treatment in this way, a double erosion prevention measure can be provided.

Table 1 shows the results of the cavitation erosion test of the turbine blade 1 manufactured as described above. This is a comparison example in which water quenching was performed immediately after heating, followed by aging treatment at 400° C. for 60 minutes.

Table 1 In addition, as cavitation erosion test,
A magnetostrictive imaging type cavitation/erosion testing device using the semi-finished method (set by the 97th Committee of the Society for the Promotion of Science and Technology) was used, and the test conditions were: vibration frequency 6.5KHz, vibration amplitude 100μ■, test liquid pure water, and liquid temperature 24±. The temperature was 1°C and the test time was 180 minutes.

As is clear from Table 1, the present invention has superior erosion resistance compared to the comparative example in which conventional annealing, solution treatment, and aging treatments were performed.

〔Effect of the invention〕

As explained above, in the present invention, at least the leading edge of the blade tip of a turbine blade made of a titanium-based alloy is plated with N1, and then nitrided to fix the erosion shield plate on which a hardened layer is formed. As a result, the hardened layer can further improve the erosion resistance of the relevant part, and a turbine blade with excellent erosion resistance can be obtained, and its life can be extended.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the turbine blade of the present invention;
FIG. 2 is a plan sectional view of FIG. 1. DESCRIPTION OF SYMBOLS 1... Turbine blade, 2... Erosion shield plate, 2a... Hardened layer. Applicant's agent Sato -Remote island 1 Closed

Claims (1)

[Scope of Claims] 1. In a turbine blade made of a titanium-based alloy, an erosion shield plate on which a hardened layer is formed by Ni plating and further nitriding is provided on at least the leading edge of the blade tip of the turbine blade. A turbine blade characterized by being fixed to a part. 2. The turbine blade according to claim 1, wherein the Ni plating has a thickness of approximately 100 μm or more.