JPS6179802A - Turbine blade of steam turbine - Google Patents

Abstract

PURPOSE:To easily prevent corrosion of a surface at a low cost, by a method wherein amorphous formation alloy is evaporated to cover the surface, with which waterdrop in wet steam collides, of a turbine blade therewith. CONSTITUTION:Hard amorphous covering 7, such as Fe80B20, is vacuum- deposited on the steam colliding surface of a turbine blade 1. A root 2, formed to the lower part of the blade 1, is engaged with a root groove in the outer peripheral part of a rotor disc, and tenon pins 3 projected from the top of the blade 1 are inserted into corresponding holes of a shroud band. This, even if steam containing waterdrops collides with the surface of the blade 1, enables the surface of the blade 1 to be completely prevented from corrosion thanks to the covering 7. Further, formation of the covering 7 can be performed easily and at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to turbine blades of steam turbines, particularly on the low-pressure side.

BACKGROUND OF THE INVENTION Superheated steam in a conventional steam turbine is sent from the steam inlet on the high pressure side, expands and passes through each stage while reducing its pressure, and is transferred to the turbine blades 01 on the low pressure side shown in FIGS. 2 and 3. After the steam is activated and rotates a rotor (not shown), the steam is discharged from the low-pressure side outlet (also not shown), but as the enthalpy of the steam decreases at that time, the recovery In a water turbine, near the final stage on the low-pressure side, the steam becomes wet, so water droplets in the steam strike the blades from the direction of arrow 06, causing corrosion on the blade surfaces. For this purpose, conventionally, for the purpose of preventing the surface corrosion, a Co-Cr-W alloy thin plate 04 called Stellite (hereinafter referred to as Stellite thin plate) was attached to the vapor collision part of the blade using silver solder 05. The method has the following drawbacks.

In other words, (1) the fatigue limit of the base material of the turbine blade 01 is lowered due to the silver soldering (05), and restrictions on the strength design of the blade become stricter, and (2) the hardness of the Stellite thin plate 04 is 400 to 450 Hv. Since the blade is expensive, it is difficult to bend it to match the curved surface of the blade and make it adhere tightly to the blade surface, and brazing is an inefficient process, so a large amount of man-hours are required to manufacture the blade. .

Problems to be Solved by the Invention The object of the present invention is to prevent corrosion of the collision surface of a turbine blade due to collision of water droplets in steam at low cost and with high productivity.

Means for Solving the Problems In the present invention, an amorphous forming alloy is evaporated and coated on the surface of a turbine blade to be corroded.

Therefore, according to the configuration of the present invention, the amorphous forming alloy coated on the blade surface by evaporation has excellent corrosion resistance, and the vapor deposition of the alloy does not lower the fatigue limit of the blade material. Work can be easily automated and productivity can be greatly improved.

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, a hard amorphous coating 7, for example "e80B20
s Fe46Cr16M020C18 etc. is vacuum-deposited using a laser, an electron beam, etc. as a heating source, and the root 2 provided at the bottom of the blade is fitted into the root groove on the outer periphery of the rotor disk (not shown). A number of blades 1 are fixed together, and a tenon pin 3, which is protruded from the upper part of the blades, is inserted into a corresponding hole in a shroud band (not shown) together with a number of other blades 1, and then the protruding part at the tip is inserted. Although the alloy is crushed and fixed, when the vapor deposited particles adhere to the blade surface, the alloy is rapidly cooled and an amorphous film is easily formed. Incidentally, even if a vapor deposition method other than the above-mentioned vacuum vapor deposition method is used, the effect remains the same.

Effects of the Invention As mentioned above, in this invention, even if steam containing water droplets from the direction of the arrow 6 of the blade 1 collides with the surface of the amorphous-forming alloy coating, the coating metal is highly corrosion resistant. Since corrosion is completely prevented and the fatigue limit of the blade base material is not lowered, strength design is easier compared to the conventional method of attaching thin stellite plates, resulting in high efficiency turbines such as higher speeds and longer blades. In addition to making it easier to respond to changes in technology, the amorphous-forming alloy coating work can be automated extremely easily, resulting in significant cost reductions compared to the conventional stellite thin plate pasting work.
The industrial utility value of this invention is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the invention, and FIG. 2 is a perspective view showing an embodiment of the invention.
FIG. 3 is a plan view showing a conventional method for imparting corrosion resistance to turbine blades of a steam turbine, and is a previous view taken along the line X--X. l...Turbine blade, 7...Amorphous (and 7 others)
Figure 2

Claims (1)

[Claims] A turbine blade for a steam turbine, characterized in that an amorphous-forming alloy is evaporated and coated on a surface on which water droplets in wet steam collide.