JP2898475B2 - Manufacturing method of oxide dispersion strengthened heat-resistant alloy sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sintering powder comprising oxide-dispersed heat-resistant alloy particles, and more particularly to a powder sintering method suitable for producing a sintered body having a complicated shape.

[0002]

2. Description of the Related Art The applicant has previously proposed an oxide dispersion strengthened heat resistant sintered alloy having excellent strength and oxidation resistance at high temperatures (Japanese Patent Application No. Hei 3-97000).

[0003] This sintered alloy is a raw material obtained by finely dispersing 0.2 to 2.0% by weight of Y ₂ O ₃ having an average particle size of 0.1 μm or less in a matrix of a metal substantially composed of Cr or a metal mainly composed of Cr. Prepare powder by mechanical alloying method,
After filling the raw material powder in a suitable metal capsule, it is degassed and sealed, and at a temperature of about 1000 to 1300 ° C., about 1000 to 2000 kgf / cm
Hot isostatic pressure treatment (HIP) under pressure of ² . this is,
This is a so-called capsule HIP sintering method. By this capsule HIP sintering, an almost completely dense sintered product can be manufactured.

[0004] A block-shaped sintered product such as a skid button for a walking beam type heating furnace is generally manufactured by capsule HIP sintering.

However, for example, like a turbine blade,
Even when a product having a complicated shape is produced, a dense sintered body block is once produced by HIP and then cut into a desired shape by machining. For this reason, there is a problem that a sintered product having a complicated shape has a very low material yield and a high product cost.

[0006] Even for a sintered product having a complicated shape, machining such as cutting after forming a sintered body block in this manner is difficult.
This is because in the case of capsule HIP sintering, it is very difficult to produce a capsule having a complicated shape. Further, even if a capsule having a complicated shape is manufactured with a large number of man-hours, the raw material powder cannot be filled so as to have a uniform density in all places in the capsule. In particular, since the filling density is low at the corners of the capsule, the amount of shrinkage after HIP also increases. For this reason, the corners of the capsule must be designed with sufficient consideration of the working margin for subsequent machining, which is substantially the same as cutting out from a sintered block.

On the other hand, sintering of the powder composed of the oxide dispersion strengthened heat-resistant alloy particles is performed without using a capsule by pressing, casting, injection molding, cold isostatic pressing (CIP), etc. to obtain a green compact having a desired shape. Then, when the compact is sintered at a high temperature, there are the following problems.

[0008] Since the sintered alloy contains about 70% or more of Cr, the melting point becomes as high as about 1700 ° C or more. Further, the melting point increases as the Cr content increases. In order to obtain a dense sintered body, in principle, sintering must be performed at a temperature near the melting point of the raw material components. However, when sintering at such a high temperature, oxides that have been finely dispersed in the metal matrix become And the strength was significantly reduced. In this case, there is no point in improving the high-temperature compressive strength by uniformly and finely dispersing the oxide.

On the other hand, green compacts containing about 70% or more of Cr are subjected to temperature conditions (about 1500
Sintering), the density of the sintered product is about 7
Since it reaches only about 5%, the desired high-temperature strength cannot be obtained, and it cannot be put to practical use. In order to eliminate the pores of the sintered product and obtain a denser structure, hot isostatic pressing (HIP) may be further performed. However, the density of the sintered product before HIP is about the same as that of the perfect dense body. If it is not more than 94%, pressure is not applied even when HIP is performed, and the effect of improving the density by HIP can hardly be expected.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a method of sintering a powder comprising oxide-dispersed heat-resistant alloy particles without using a metal capsule and without heating the powder to a temperature higher than about 1500 ° C. It is an object of the present invention to provide a sintering method by which a product can be obtained.

[0011]

SUMMARY OF THE INVENTION The present invention provides substantially Cr
The metal in the matrix composed mainly of metal or Cr consisting, in the sintering of the raw material powder was average particle diameter 0.1μm or less of Y ₂ O ₃ 0.2 to 2.0 wt% finely dispersed, about 1500 ° C. or less green compact By sintering at a temperature of above, it is possible to form a sintered body having a density of about 94% or more of the perfect dense body. Is obtained.

In the sintering method of the present invention, 0.2 to 2.0% by weight of Y ₂ O ₃ having an average particle size of 0.1 μm or less is finely dispersed in a matrix of a metal substantially composed of Cr or a metal mainly composed of Cr. Mixing 1 to 5 parts by weight (total amount) of at least one kind of powder selected from the group consisting of Fe powder, Ni powder and Co powder with respect to 100 parts by weight of the raw material powder obtained, The method includes a step of forming a green compact having a predetermined shape, a step of sintering the compact, and a step of hot isostatic pressing of the obtained sintered body.

[0013] In the mixing step, a powder of a metal substantially composed of Cr or a metal mainly composed of Cr is mixed with a powder of 0.2 to 2.0.
The weight% of Y ₂ O ₃ were mixed raw material powder 100 parts by weight, Fe powder, at least one or more kinds of powder 1 to 5 parts by weight is selected from the group consisting of Ni powder and Co powder (total amount) Simultaneous preparation of an oxide dispersion-strengthened alloy powder in which Y ₂ O ₃ having an average particle size of 0.1 μm or less is finely dispersed in a metal matrix by mechanical alloying treatment, and mixing with the one or more powders simultaneously You can do it.

The green compact sintered body should have a density of about 94% or more of the perfect dense body.
This is for the purpose of obtaining a nearly completely dense sintered body by the subsequent HIP.

The metal is a metal substantially composed of Cr or a metal substantially containing 20% or less of Fe and the balance substantially composed of Cr.
Or Al, Mo, W, Nb, Ta, Hf and Al-Ti
At least one selected from the group consisting of: a metal consisting essentially of Cr or Al, Mo, W, Nb, Ta, Hf and Al-
It is a metal containing at least one selected from the group consisting of Ti in a total amount of 10% or less and Fe of 20% or less, and the balance substantially consisting of Cr. Note that Al-Ti is an intermetallic compound. By finely dispersing 0.2 to 2.0% by weight of Y ₂ O ₃ having an average particle diameter of 0.1 μm or less in the matrix of these metals, when used as a sintered product in a temperature range exceeding 1300 ° C., high compression deformation resistance is obtained. And stable oxidation resistance can be ensured in an oxidizing atmosphere.

A raw material powder comprising oxide dispersion strengthened heat-resistant alloy particles and at least one of Fe, Ni and Co powders are substantially uniformly mixed. By interposing fine particles such as Fe between the particles of the raw material powder, these fine particles exert a bridging role of sintering, and the sinterability of the raw material powder can be improved. The amount of Fe, Ni, Co powder added is
If the amount is less than 1 part by weight per 100 parts by weight, the effect of improving the sinterability of the raw material powder cannot be expected. On the other hand, when the addition amount exceeds 5 parts by weight, the added powder particles are not sufficiently dissolved in the mother alloy at the time of sintering and remain at the particle interface, thereby impairing the inherent characteristics of the oxide dispersion strengthened heat-resistant alloy particles. And the strength at high temperatures decreases. For this reason, Fe, N
i, Co powder is 1 to 5 parts by weight based on 100 parts by weight of the oxide dispersion strengthened heat resistant alloy.

It is desirable that the Fe, Ni, and Co powders to be added have a fine particle size, and it is necessary that the particle size be at least smaller than that of the raw material powder. Desirable particle size is about
10 μm or less.

[0018]

[Function] Since one or more fine particles of Fe, Ni, and Co are interposed between alloy particles of the raw material powder, diffusion tends to occur at the particle interface of the raw material powder, and mutual diffusion is performed at a temperature lower than the melting point. It is considered that sintering and densification occur.
Therefore, even if the raw material powder contains 70% or more of Cr and has a melting point of more than about 1700 ° C., it is sintered at a temperature of about 1500 ° C. or less to obtain a sintered compact having a density of about 94% or more of a completely dense body. You can get union.

By subjecting the sintered body to HIP, pores are removed, and a substantially dense structure is formed.

[0020]

EXAMPLES FE14%, and subjected trial original material powder A consisting of Cr85% and Y ₂ O ₃ 1% of the alloy particles, Fe4%, consisting of Cr95% and Y ₂ O ₃ 1% of the alloy particles subjected trial original material powder B The effect of improving the sinterability by adding Fe, Co, and Ni powders was examined.

The raw material powder is obtained by subjecting a metal powder and a Y ₂ O ₃ powder to mechanical alloying treatment sufficiently by using a high energy ball mill such as an attritor.
Oxide dispersion strengthened alloy particles having an average particle size of 10 μm or less were obtained.

At least one of Fe, Ni and Co powders is added to the raw material powder and mixed substantially uniformly. As the additive powder, pure Fe, pure Ni, or pure Co powder having a particle size of about 2 μm or less was used.

As an example of mixing, a polypropylene wide-mouth bottle is charged with an oxide dispersion-strengthened heat-resistant alloy powder (eg, 500 g) and at least one of Fe, Ni, and Co powders. , Diameter 19.2mm, 6.8mm)
And then sealed, followed by ball milling (eg, 24 hours).

Alternatively, an oxide dispersion strengthened heat-resistant alloy powder
(For example, 1800 g) and at least one of Fe, Ni, and Co powders may be kneaded (for example, for 5 hours) by a high energy ball mill such as an attritor. In addition, Cr
After obtaining a mechanical alloying effect by kneading a mixed powder of alloy powder (for example, 1800 g) and Y ₂ O ₃ (for example, 9 g) for a sufficient time (for example, 65 hours or more) by a high energy ball mill such as an attritor, etc. , Fe in the same ball mill,
Kneading may be performed by charging at least one kind of Ni and Co powders.

Sample powder A or B, Fe, Ni, C
Table 1 shows various examples in which at least one powder of o was added and mixed. Test Nos. 1 to 5 were mixed with test raw material powder A, and Test Nos. 6 to 8 were mixed with test raw material powder B. In addition, in Table 1, the amount of the added powder is shown by weight based on 100 parts by weight of the test raw material powder.

Each of the test materials No. 1 to No. 8 was filled in a rubber cylinder and subjected to cold isostatic pressurization (CIP) to apply a pressing force of 1500 kgf /
The green compact (diameter 30 mm x length 30 mm) was formed under the conditions of cm ² and a pressing time of 1 minute.

Next, these green compacts were sintered in an atmosphere of Ar and H _{2 in} an electric furnace at a temperature of 1500 ° C. and a heating time of 4 hours. After removing the oxide film adhered to the surface of the sintered body, the density was measured based on the Archimedes method. Note that the relative sintering densities of both the test raw material powders A and B were calculated assuming that the density of the completely dense body was 7.2 g / cm ³ . The calculation results are shown in the column “Before HIP” in Table 1.

Each of the obtained sintered bodies was heated at a temperature of 1250 ° C.
HIP was performed under the conditions of 1200 kgf / cm ² and HIP time of 2 hours. After HIP, the density was measured in the same manner as described above. Table 1 shows the calculation results of the relative sintered density after HIP.

As comparative examples, test materials No. 11 to No. 15 were produced. Specimens No. 11 and No. 15 were comparative examples not containing any of Fe, Ni and Co powders, and Specimens No. 12 to No. 14 were F
This is a comparative example in which the amounts of e, Ni, and Co powders do not reach the specified amounts of the present invention. For these comparative examples, green compacts were formed in the same manner as described above, and thereafter, sintering and HIP were performed, and the relative sintered densities were examined. Table 1 shows the results.

[0030]

[Table 1]

As is clear from the results shown in Table 1, a test material (No. 1) was prepared by adding and mixing 1 to 5 parts by weight of at least one of Fe, Ni, and Co powders to 100 parts by weight of the test material powder. ~
No. 8) is the stage before HIP, which is already 93.8-
95.5% of a dense sintered body was obtained, and it is understood that a dense sintered product can be obtained almost completely by further HIP.

On the other hand, the test materials No. 11 and No. 15
Since e, Ni, and Co powders were not added, only a sintered body having a relative density of about 75% was obtained before HIP. Even if this test material is further subjected to HIP, the effect of increasing the density is hardly recognized. In addition, test materials No. 12 to No.
No. 14 has a small addition amount of Fe, Ni, and Co powders.
Only about 80% sintered body can be obtained. Even if HIP is further performed on these sintered bodies, the effect of improving the density is insufficient.

From the above results, by mixing at least one of a predetermined amount of Fe, Ni and Co powders with the raw material powder of the oxide dispersion strengthened heat-resistant alloy, the sinterability is improved and the temperature is considerably lower than the melting point. It can be seen that even if sintering is performed, a sintered body having a relative density of at least about 94% can be obtained.

[0034]

As described above, HIP sintering of the oxide dispersion strengthened heat-resistant alloy powder can be performed without using a capsule.
The degree of freedom of the product shape to be sintered is large. Therefore, a very compact sintered product can be obtained only by forming a green compact by molding a product of almost any shape from the raw material powder and subjecting it to normal sintering and HIP. Even if a complex shaped sintered product is made from a high melting point oxide dispersion strengthened heat-resistant alloy powder, the production of capsules and machining after the formation of a dense sintered body block are not required. large.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takahiro Kitagawa 1-1-1, Hama, Amagasaki-shi, Hyogo Prefecture Inside Kubota Technology Development Laboratory Co., Ltd. Inside the Amagasaki Plant (56) References JP-A-4-325565 (JP, A) JP-A-6-25712 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 1/05 , 1 / 10,27 / 06 B22F 3/00-3/26

Claims (1)

(57) [Claims] 1. An average particle size of 0.1 μm in a metal matrix.
At least one kind of powder 1 selected from the group consisting of Fe powder, Ni powder and Co powder is added to 100 parts by weight of the following raw material powder composed of particles in which 0.2 to 2.0% by weight of Y ₂ O ₃ is finely dispersed. To 5 parts by weight (total amount), a step of forming the obtained mixture into a green compact having a predetermined shape, a step of sintering the compact at a temperature of 1500 ° C. or lower , and a resultant sintered body. And a step of hot isostatic pressurization, wherein the metal contains substantially Cr or a metal substantially containing 20% or less of Fe, and the remainder substantially consists of Cr, or Al, Mo, W, and Nb. , Ta, Hf and A
At least one selected from the group consisting of l-Ti is included in a total amount of 10% or less, and the balance is substantially composed of Cr, or Al, Mo, W, Nb, Ta, Hf, and Al-Ti A method for producing an oxide dispersion-strengthened heat-resistant alloy sintered body comprising at least one selected from the group consisting of: a total amount of 10% or less and Fe of 20% or less, and a balance substantially consisting of Cr.