JPS60204807A - Production of high-density sintered body - Google Patents

Abstract

PURPOSE:To produce easily a high-density sintered body having a hardened surface by subjecting the sintered body to an impregnation treatment to close the holes on the surface thereof then subjecting such body to a hot isotropic pressurization treatment. CONSTITUTION:A sintered body is subjected to an impregnation treatment to close the holes on the surface of the sintered body which communicate with the outdoor air and thereafter the sintered body is subjected to a hot isotropic pressurization treatment to crush and annihilate the holes existing therein by a pressure difference by which the porosity is decreased and the density is increased; at the same time the holes on the surface which are held closed are also crushed to harden the surface. The above-mentioned impregnation treatment and succeeding hot isotropic pressurization treatment are preferably executed plural times for sure closing of the holes on the surface. A ceramic slurry contg. at least one kind of Al2O3, SiO2 and Cr2O3 is preferably used as an impregnating material in the above-mentioned impregnating treatment to form the closed state of high hardness.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a method for manufacturing a high-density sintered body.

[Technical background of the invention and its problems]

Attempts have been made to use a hot isostatic press to further harden a sintered body produced by sintering after powder compaction. This process is
For example, the heating temperature is about 1200°C to 2000°C.

The material is cured by uniformly applying pressure from the surroundings in an inert gas of about 1,000 to 3,000 atmospheres. Through this treatment, the pores that were closed in the sintered body are crushed and eliminated by the pressure difference with the surroundings, the porosity is reduced, and the sintered body, especially its surface, is hardened.

However, in the case of products with complex shapes such as turbocharger rotors and compressor blades, it is necessary to increase the pressurizing conditions more uniformly in order to provide the desired physical strength such as Nk resistance and thermal shock resistance. However, production has become extremely difficult as processing conditions become more pressurized, such as requiring the use of containers with higher pressure resistance in accordance with the pressurizing conditions.

[Purpose of the invention]

The present invention was made to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a method for manufacturing a high-density sintered body whose surface can be easily hardened.

[Summary of the invention]

That is, the present invention has been made to achieve the above object, and includes performing a hot isostatic pressing treatment (HIP treatment) after impregnating the sintered body and closing the pores on the surface of the sintered body. This is a method for manufacturing a high-density sintered body characterized by the following.

A normal sintered body has pores that communicate with the surrounding outside air, that is, communicating pores, and closed pores, and the pores that are closed by HIP processing are crushed by the pressure difference between the surrounding high pressure and the low pressure inside the pores. However, the communicating pores around the surface that communicate with the outside air do not create a pressure difference and are difficult to disappear because they are in communication with the outside air even when pressurized by the HIP process.For this reason, the pores are crushed by the HIP process. However, the effect of surface hardening is incomplete.The present invention is based on the above discovery, and the HIP treatment is performed after impregnating the sintered body and closing the pores on the surface of the sintered body. As a result, the communication holes that existed before the impregnation treatment are also closed, and pressurized from the surroundings, crushed by the pressure difference, and eliminated. In this manner, the communication holes that were present and communicated with the outside air can also be eliminated, and the surface can be hardened. Further, in the manufacturing method of the present invention, since the nuclide is applied to the surface of the sintered body by impregnation treatment, it is possible to easily infuse the nuclide even in a part having a complicated shape such as a turbocharger-like rotor.

In order to more reliably obtain the above effects in the manufacturing method of the present invention, it is recommended to repeat the impregnation treatment→HIP treatment at least twice or more.

Alternatively, it is desirable to perform the HIP treatment after repeating the impregnation treatment two or more times, since this makes it easier to turn open pores in the sintered body into closed pores.

In addition, if the impregnating agent applied to the sintered body has a low hardness when hardened, it will have little effect on increasing the strength of the sintered body even if it is impregnated into the pores, so hardening materials such as ceramic slurry should be used. It is desirable to select one with high hardness.

The impregnating material was AJ203.5iOz.

Practically preferred is a slurry of metal oxide ceramic such as Orhos.

[Embodiments of the invention]

A binder containing wax, polyethylene, and stearic acid in a ratio of 7:1:1 is added to a powder mainly composed of iron with a particle size of 10 to 44 μm, and the mixture is uniformly mixed to produce compressor blades with relatively complex shapes by injection molding. Shape and heat at 20℃
From 180℃ to 180℃, the temperature was increased at a temperature increase rate of 10℃/hr, and after holding at 180℃ for 4 hours,
Degreasing was performed by heating to 0°C.

Next, the temperature was raised to 1200°C at a heating rate of about 300°C/hr, and this temperature was maintained for 1 hour to perform sintering.

The sintered body thus obtained was processed into a slurry of Cr2
After repeating the operation of soaking in O3 solution and firing at 550°C for 1 hour 3 or 4 times, the temperature was increased to 120°C in an Ar gas atmosphere.
A high-density sintered body was manufactured by performing HIP treatment under the conditions of 0° C. and 2000 atm pressure.

The high-density sintered body manufactured by the above manufacturing method had greater mechanical strength and superior wear resistance, corrosion resistance, and thermal shock resistance compared to a sintered body manufactured by simply performing HIP treatment after sintering. .

〔Effect of the invention〕

According to the manufacturing method of the present invention, by performing the HIP treatment after closing the pores, especially the communication holes, in the sintered body, it is possible to easily withstand even complex-shaped sintered bodies without significantly increasing the pressurizing conditions. Properties such as abrasion resistance, thermal shock resistance, and mechanical strength can be improved.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a high-density sintered body, characterized in that the sintered body is impregnated to close the pores on the surface of the sintered body, and then hot isostatic pressure treatment is performed. . 2. The method for manufacturing a high-density sintered body according to claim 1, wherein the impregnation treatment is performed on the sintered body, and the hot isostatic pressing treatment after the impregnation treatment is performed multiple times. 3. The method for manufacturing a high-density sintered body according to claim 1 or 2, wherein the impregnation treatment applied to the sintered body is a treatment using a ceramic slurry containing ceramic as an impregnating material. 4. The impregnation treatment applied to the sintered body is AA! zoa, 5iOz
4. The method of manufacturing a high-density sintered body according to claim 3, wherein the treatment is performed using a ceramic slurry containing at least one type of Oryo03 as an impregnating material.