JPS634005A - Production of composite radial turbine - Google Patents

Abstract

PURPOSE:To improve the strength of a joint surface by sintering the powder packed between the outside surface of a hub and the inside surface of a rim formed to an nearly circular conical shape while breaking the oxide films on the hub and rim surfaces by applying a compressive shearing deformation to the powder. CONSTITUTION:The joint surfaces of the hub 4 and rib 2 formed of different materials are formed to the surface shape having the inclination approximate the nearly circular conical shape. After superalloy powder 8 is packed into the spacing between such hub 4 and the rim 2, the powder is subjected to a hot hydrostatic pressurizing treatment in the vacuum state. The hub 4 is moved to the axial direction according to the pressurization and the powder-packed layer 8b in compressed. The powder is sintered while the oxide films on the hub 4 and the rim 2 are broken by exerting the shearing force to the layer 8b, by which the rim 2 and the hub 4 are joined.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a composite radial turbine, and more specifically, a method for manufacturing a composite radial turbine, in which a composite radial turbine rotor in which the blades and the hub (center part) are made of different materials is heated. Hydrostatic pressurization (
Hereinafter, it will be abbreviated as HIP. ).

(Prior Art) In gas turbines for twin generators for aircraft, it is constantly required to increase the turbine inlet temperature and increase the expansion ratio in order to increase the output and improve the fuel consumption rate.

In particular, the blades of a radial turbine rotor are required to have creep strength because they are subjected to high centrifugal stress in a high-temperature gas flow. On the other hand, since stress due to centrifugal force acts repeatedly on the hub each time the rotor starts and stops, it is required to have high mechanical strength to withstand these large centrifugal forces.

Conventionally, rotor structures suitable for such conditions have been studied, and as one example, such a composite radial turbine rotor is disclosed in Japanese Patent Application Laid-open No. 106005/1983. This is the rim (outer periphery) as described in the same publication.
A shell with integrally molded blades on the outer circumferential surface is cast from a creep-resistant material, and a hub made of a material with high mechanical strength is fitted onto the inner circumference of the rim and diffusion bonded by HIP processing.

(Problem to be Solved by the Invention) However, in the above method, when the hub is diffusion bonded to the inner circumferential surface of the rim, a thin oxide film is present on the outer circumferential surface of the hub and the inner circumferential surface of the rim. , which remains after bonding and reduces the mechanical strength of the bonded surface.

However, one method for removing such an oxide film is disclosed in JP-A-56-131091 "Method for joining metal members".
A method disclosed in is known. This method involves interposing a thin layer of metal powder between two solids to be diffusion bonded. This is because the metal powder destroys the oxide film on the solid surface under high temperature and high pressure, helping to bond the metals together, and the destroyed oxide film becomes spheroidal through heat treatment, thereby avoiding a decrease in mechanical strength.

However, although this technique can be applied to joining a hub and a rim, it has the following problems.

(1) In high-speed rotating bodies such as radial turbine rotors, centrifugal stress is high and repeatedly applied, so the reliability required for joints is extremely high (that is, the destruction of the oxide film must be more complete). (2) Although the powder packed bed undergoes volumetric contraction under high pressure,
At that time, the outer rim also contracts, which causes undesirable aerodynamic deformation of the blades molded around the rim.

The present invention addresses the above-mentioned circumstances and provides a hub.

By applying compressive shear deformation to the powder-filled layer between the rims, the oxide film on the hub and rim surfaces is more completely destroyed, resulting in a stronger joint surface, and the powder filling is made possible by allowing the hub to move. The purpose of this is to partially compensate for the shrinkage of the layer volume and suppress shrinkage deformation of the rim.

(Means for Solving the Problems) That is, the feature of the method of the present invention for achieving the above object is that in a composite radial turbine rotor in which the rim, the blades, and the hub are made of different materials, first, the hub and the rim are joined together. The surface shape is a conical shape or a surface with an inclination close to the conical shape, the outer surface of the hub and the inner surface of the rim are spaced apart by a required distance in the axial direction, and the hub is assembled so as to be movable in the axial direction. Next, a cover with a tube is attached to the rim, and in this state, superalloy powder is filled around the hub through the tube opening, and then air is degassed through the opening while heating the whole, and the powder-filled area is evacuated to form a vacuum inside the tube. occlude.

Then, in this state, the above-mentioned item is placed in a HIP device and subjected to HIP processing, and the hub is moved in the axial direction according to pressure,
The purpose of this method is to compress the packed powder layer and apply shear deformation to the core layer while sintering it, thereby firmly joining the hub and rim.

(Function) When the above method of the present invention is applied to joining the hub and rim of a radial turbine rotor, the hub, which has a conical outer shape or a rotating surface with an inclination close to this, receives pressure from the outside in the axial direction. The thin layer of powder around the hub is subjected to shear and compression forces. This shearing force easily destroys the oxide film on the surfaces of the hub and rim, resulting in a strong bonding surface between the two. At this time, shear deformation occurs throughout the powder layer, so that the mechanical properties of the powder layer after sintering are also stable and good.

Furthermore, since the compressive force is applied to the metal powder layer before the hub and rim are deformed, the packing density is increased, and subsequent deformation of the rim is reduced, resulting in less deformation of the blades on the rim.

(Example) Hereinafter, specific embodiments of the present invention will be described with further reference to the accompanying drawings.

The figure shows the manufacturing state of the radial turbine rotor according to the present invention. In the figure, (1) is a shell consisting of a rim (2) and blades (3), which is made by precision casting of superalloy. On the other hand, (4) is a hub made of a superalloy powder molded product, and after polishing the inner surface of the rim (2) and the outer surface of the hub (4), these are polished using the pin (9) and αω. Assemble them a certain distance apart in the axial direction.

Here, the pin (9), αω, is made of soft metal, which almost loses its rigidity at high temperatures.

Therefore, after the subsequent HIP process, the vicinity of these pins is removed by cutting.

Next, to the rim and hub assembly assembled above, a stainless steel cover (5) is attached to the rim (2) by welding or brazing so as to be airtight.

This cover (5) corresponds to the lid of a capsule container in HIP processing, and has a tube (6) protruding from its center, and an opening (7) at its tip.

Therefore, in the above state, the superalloy powder (8) is passed through the opening (7).
) around the hub (4).

In this case, it is preferable that the superalloy powder (8) is made of the same material as the hub (4) if possible.

When the filling is finished, the whole is heated while opening (
7) is degassed, the area filled with powder (8) is evacuated, the tube (6) is crushed and closed, and HIP treatment is performed using a known HIP device.

At this time, the hub (4) is connected to the cover (5) and the cover (5).
) and the hub (4), the powder moves forward, that is, to the right in the figure, and compresses the powder packed layer (8b) around the hub (4). At the same time, shearing deformation is applied to the packed bed (8b).

In addition, according to the above pressure, the front powder packed layer (8
In the vicinity of c), shearing deformation does not occur because the direction of the layer is perpendicular to the axis, but since the centrifugal stress in this region is low, it is not a problem if it is installed separately.

In this way, the oxide film between the hub and rim is destroyed by the HIP treatment as described above, and a stronger joint surface can be obtained.At the same time, by moving the hub (4) to the right side, the volume of the powder-filled layer is reduced. A portion of the shrinkage is compensated for, suppressing the shrinkage deformation of the rim, reducing the effect of deformation on the blades, and making it possible to manufacture a high-performance turbine rotor.

(Effects of the Invention) As described above, the present invention makes the shape of the joint surface between the hub and the rim into a conical shape or a surface shape with an inclination close to the conical shape, and the hub is attached so as to be movable in the axial direction, and is filled with powder. ShiHI
Due to the shape of the joint surface and its ability to move in the axial direction, it moves in the axial direction when pressure is applied from the outside during HIP, producing shearing force and compressive force in the thin powder layer. The shear force deformation can destroy the oxide film existing on the hub and rim surfaces, and together with the compressive force can provide the joint part with the required sufficiently strong and reliable joint. Since it occurs throughout the powder layer, the mechanical properties after sintering the powder layer can also be stable and good.

Alternatively, during the HIP process, the compressive force is applied to the metal powder layer before the hub and rim are deformed, so the powder packing density increases, reducing subsequent deformation of the rim and deformation of the blade on the rim. This method can provide a high-performance turbine rotor, and is expected to be effective in the future as a manufacturing method for high-performance composite radial turbines, which have recently been required to have higher performance.

[Brief explanation of drawings]

The figure is a schematic cross-sectional view showing an example of how the knob and rim are assembled in the implementation of the method of the present invention. (1)...Shell, (2)...Rim,
(3)...Blade, (4)...Hub, (5)...Cover, (6)...Tube, (7)... ...opening, (8)...
・Powder, (9)αω・・・Pin.

Claims (1)

[Claims] 1. When manufacturing a composite radial turbine rotor in which the rim, blades, and hub are made of different materials, first, the shape of the joint surface between the hub and rim is made into a conical shape or a surface shape with an inclination close to this shape. , assemble the outer surface of the hub and the inner surface of the rim by a required distance in the axial direction and to allow the hub to move in the axial direction, then attach a cover with a tube to the rim of the assembly and move around the hub from the tube opening. After filling the tube with superalloy powder, the whole is heated and degassed through the tube opening, the powder-filled area is evacuated, and the tube is closed, and then the tube is subjected to hot isostatic pressure treatment in that state. Then, the hub is moved in the axial direction according to the applied pressure, compressing the powder-filled layer, and supporting shearing force on the layer to destroy the oxide film on the hub and rim surfaces and sinter them, thereby joining the two. A method for manufacturing a composite radial turbine characterized by: