JPS5838601B2 - Blades for high temperature rotating bodies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blade for a rotating body that can withstand long-term use in high-temperature gas.

Until now, heat-resistant alloy fittings have been used for rotating parts used at high temperatures, but when the temperature of the blade body exceeds 800°C, it is necessary to use long materials in terms of strength, oxidation resistance, and corrosion resistance. It had the disadvantage of not being able to withstand the use of time.

Therefore, in such cases, air-cooled blades are used in gas turbines and efforts are made to cool the blades from within to lower the temperature of the blades themselves. However, if the gas temperature rises even higher than 1,000℃ Since this method requires a large amount of cooling air, the efficiency decreases, and there is no point in increasing the gas temperature to improve efficiency, so it cannot be said to be an essential improvement measure.

In addition, in cases where the temperature of the blade itself cannot but reach 850°C or higher even with appropriate air cooling, the blade should be made so that even high temperatures are sufficient to obtain sufficient leap strength and creep rupture strength.
Wings made of ceramics and alloys of high-melting metals such as columbium were used.

However, even with high-melting point metal alloys, oxidation in high-temperature gas,
Ceramic blades suffer from the disadvantages of not being able to withstand corrosion, and high-melting point metals are very expensive, while ceramic blades are tough,
Since it has poor ductility and cannot withstand impact force, it has the disadvantage of being poor in reliability as a rotating body.

Therefore, the inventor of the present invention conducted intensive research to provide a blade for a high-temperature rotating body that can withstand long-term use in high-temperature gas, and found that a blade made of ceramics was created by coating the surface with a ductile metal layer. , it is possible to prevent the brittleness of ceramics against impact, but the coating metal layer has a temperature of 100℃
Since it cannot have oxidation resistance and corrosion resistance against the above-mentioned high-temperature gases, it was found that the defects could be prevented by further coating the surface with a ceramic layer, and based on this knowledge, the present invention was completed.

That is, the present invention provides a blade body made of ceramics, a first intermediate layer made of a mixture of ceramics and a heat-resistant metal and coated on the surface of the above concrete, and a thin layer of heat-resistant metal coated on the surface of the first intermediate layer. a second intermediate layer made of a mixture of ceramics and a heat-resistant metal and coated on the surface of the thin layer of the heat-resistant metal; and a ceramic layer coated on the surface of the second intermediate layer. The object of the present invention is to provide a blade for a high-temperature rotating body, which is particularly suitable as a rotor blade for a gas turbine.

The surface of the blade is made of ceramics such as Si3N4 or SiC, which has a high melting point such as columbium, tantalum, tungsten, or molybdenum, and alloys of these metals, and has a coefficient of thermal expansion that is small compared to metals and close to that of ceramics. Cover with heat-resistant metal material.

Brittle fractures of ceramic materials occur when other objects come into impactful contact with the surface of the ceramic material, causing cracks to form on the surface.

Furthermore, since ceramics have low ductility, when bending stress is applied to another object, the stress that increases on the surface cannot be alleviated by deformation, which may lead to destruction.

In these cases, the presence of a ductile metal layer in close contact with the surface is extremely effective in preventing brittle fracture of the ceramic.

However, since the metal covered on the surface cannot have sufficient oxidation resistance and corrosion resistance against high-temperature gases of 1,000° C. or higher, it is necessary to further coat the surface with a thin layer of ceramic.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

First, when the ceramic blade 1 is coated with a heat-resistant metal, the surface of the ceramic is coated as it is or the surface is metallized and coated with 0, which is made of a mixture of ceramic and heat-resistant metal.
A first intermediate layer 2 with a thickness of 1 to 0.2 mm is coated, and a layer 3 of refractory metals or alloys thereof is coated thereon with a thickness of 0.2 to 0.5 mm.

Furthermore, in order to coat ceramics on top of this, it is not necessary to coat it directly, but to coat it with a mixture of heat-resistant metal and ceramics.
A second intermediate layer 4 having a thickness of 1 to 0.2 mm is coated, and a ceramic layer 5 is coated thereon to a thickness of 0.2 to 0.5 mm.

By providing the intermediate layers 2 and 4 in this way, it is possible to alleviate the difference in thermal expansion coefficients between the layers, reduce thermal stress during use, and increase the adhesive strength between the heat-resistant metal layer and the ceramic layer.

These coatings are applied by powder application or thermal spraying.
Sintering at a suitable high temperature (e.g. for Si3N4, sintering at 1,700'C to 1,800'C in vacuum or inert gas)
(~3 hours) to increase the strength of each layer and the adhesion between layers.

The materials of the first intermediate layer 2, the second intermediate layer 4, and the outermost ceramic layer 5 may be the same as the ceramic of the blade body 1, or may be different materials.

EXAMPLE The surface of the Sia N4 sintered body (a hollow cylinder with an outer diameter of 15 mm, an inner diameter of 5 mrl, and a length of 50 mm) manufactured by the hot press method was coated with an intermediate layer (0.1 ms thick) of a mixture of columbium powder and S t 3 N4 powder. ), then coated with a 0.4 mm thick layer of columbium metal by thermal spraying of columbium powder, and then again coated with 0.1 mm of the above mixed powder.
It was coated to a thickness of mrn, and further coated to a thickness of 0.4 mrn with S t 3 N4 powder.

The specimens were sintered in a vacuum at 1,700°C to 1,800°C for 3 hours, and the surface remained even after repeated heating and cooling, in which they were heated to 1,300'C with a gas burner and rapidly cooled to room temperature with an air flow. It was shown that there was no occurrence of cracks, peeling, etc., and that it was sufficiently durable.

Similar results were also obtained when tantalum was used instead of columbium.

[Brief explanation of the drawing]

The accompanying drawing is a conceptual diagram (cross-sectional view) showing the structure of the high-temperature rotating body tool of the present invention.

Claims (1)

[Claims] 1. A blade body made of ceramics, a first intermediate layer made of a mixture of ceramics and a heat-resistant metal and coated on the surface of the blade body, and a thin layer of heat-resistant metal coated on the surface of the first intermediate layer. , a second intermediate layer made of a mixture of ceramics and a heat-resistant metal and coated on the surface of the thin layer of the heat-resistant metal; and a ceramic layer coated on the surface of the second intermediate layer. Wings for rotating bodies.