JPH1017958A - Production of oxide dispersion strengthened type chromium base alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the toughness of an alloy material and to enable machining thereto by heating a sintered allay material at a prescribed temp. in an inert gas. SOLUTION: This alloy is produced from powder contg. at least, by mass, high m.p. metallic oxide and >=57% Cr and produced by a mechanical allaying method. As the above high m.p. metallix oxide, Y2 O3 or the like can be adopted. Furthermore, the above powder may contain a small amt. of Zr, La or the like as well as <=20% Fe. Then, it is subjected to hot hydrostatic pressing and is subjected to compacting and sintering to obtain a sintered alloy having high density. Next, this material is heated at >=1400 deg.C in an inert gas. In this way, the strains stored at the inside of the sintered alloy material are released to improve its toughness, and, in the subsequent machining such as cutting, the generation of defects such as cracking, chipping or the like can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in the productivity of an oxide dispersion strengthened chromium-based alloy.

[0002]

2. Description of the Related Art The applicants have proposed an oxide dispersion strengthened alloy having excellent oxidation resistance and strength at high temperatures in Japanese Patent Application No. 7-16371. This alloy comprises a Cr-based metal powder, a high melting point metal oxide powder, Zr, La, Ce, N
By processing a metal powder such as d and Y by a mechanical alloying method, it is processed into a tight and uniform mixture powder of each component, and the mixture powder is subjected to hot extrusion or hot isostatic pressing (HIP). ) The powder is compacted and sintered by the treatment.

Then, the sintered alloy material is subjected to hot extrusion to impart structural anisotropy and internal strain to the alloy material, and further heated to a high temperature to coarsen crystal grains. In this state, the alloy has high high-temperature strength and appropriate toughness at room temperature, and is used after being processed into a required shape by molding such as machining. Meanwhile, when performing the hot extrusion or the HIP treatment for compacting and sintering the mixture powder, it is necessary to encapsulate the mixture powder in a metal capsule or sheath. After the treatment, it is necessary to remove the capsule or sheath by cutting to maintain the surface condition of the sintered alloy material.

However, the oxide dispersion-strengthened alloy of the present invention is extremely brittle in the state of compacting and sintering, and thus has a problem that the material is cracked or chipped by machining such as cutting and grinding. If the surface condition is poor, cracks occur during the next step of hot extrusion for imparting directionality and internal strain, which significantly reduces the yield.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the toughness of a dispersion-strengthened chromium-based alloy by compacting and sintering, thereby enabling machining, and providing a sound and high yield. An object of the present invention is to provide a method for manufacturing an alloy.

[0006]

In order to achieve the above-mentioned object, a method for producing an oxide dispersion-strengthened chromium-based alloy according to the present invention comprises the following steps: And a step of heating the powder produced by the mechanical alloying method at a temperature of 1400 ° C. or more in an inert gas after hot isostatic pressing. I do.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION
ROM-based alloys have a high melting point of at least 0.2-2.0% by mass.
It contains point metal oxide and 57% by mass or more of chromium.
Manufactured from powders manufactured by the nickel alloying method
You. The refractory metal oxide is Y _TwoO_Three, Zr
O_Two, Al_TwoO_Three, Gd_TwoO_ThreeAnd the like. Also
The powder contains 20% or less of Fe, a small amount of Zr,
Including La, Ce, Nd, Y, Mo, W, Si, Mn, etc.
You may go out.

[0008] The HIP process is usually performed using a HIP apparatus by a method of processing powder. As a result, the powder is compacted and sintered, and becomes a high-density sintered alloy material. Next, the sintered alloy material is heated at a temperature of 1400 ° C. or more in an inert gas. By heating at a temperature of 1400 ° C. or more, the strain stored inside the sintered alloy material is released, and the toughness is improved, and defects such as cracks and chips are not generated by subsequent processing such as cutting. . If the heating temperature is lower than 1400 ° C., the effect is not sufficient, so the heating temperature needs to be 1400 ° C. or higher.

When the above-mentioned heating is performed in an atmosphere containing oxygen, such as the air, Cr, which is a material of the sintered alloy material, becomes 14%.
At a high temperature of 00 ° C. or more, instead of dense and stable Cr ₂ O ₃ , CrO ₃ having a high vapor pressure is formed and sublimates. As a result, Kirkendall voids are formed in the alloy,
The alloy becomes brittle. Further, when heating in a nitrogen-containing atmosphere, hard and brittle CrN is formed on the surface, which impairs the workability of the alloy. Therefore, the heating needs to be performed in an inert gas. As the inert gas, a rare gas belonging to Group VIIIb can be mentioned, but argon is preferred in terms of performance and cost.

[0010] Since the toughness of the alloy is improved by the above treatment, machining such as cutting and grinding of the metal capsule used in the HIP treatment, and cutting and forming for hot extrusion in the next step can be performed. .

[0011]

EXAMPLES Tight and uniform mixture powders of fine powders having the respective chemical compositions shown in Table 1 were prepared by mechanical alloying, filled into mild steel capsules, degassed, and sealed. This is 1300 ° C, 1200kgf / c
HIP treatment was performed under the conditions of m ² to obtain a sintered body of φ40 × 100 mm.

[0012]

[Table 1]

The sintered body was placed in an argon atmosphere as shown in Table 2.
Was heated for 3 hours at the temperature shown in Table 1 to obtain a test material. A JIS No. 14A tensile test piece having a parallel portion diameter of 6 mm was cut out from each test material by turning, and the presence or absence of cracks was examined for each test piece using a penetrant inspection method. The test was performed on each of three test pieces. Table 2 shows the number of test pieces where cracks were found.

[0014]

[Table 2]

As is clear from Table 2, it can be seen that in the embodiment of the present invention, the crack sensitivity during machining is improved.

[0016]

As described above, according to the present invention, the toughness of the oxide dispersion strengthened chromium-based alloy in the state of compacting and sintering is improved, and machining becomes possible. Thus, a sound and economical method for producing an oxide dispersion strengthened chromium-based alloy having a high yield can be provided.

Claims (1)

[Claims] 1. A powder containing at least 57% by mass of chromium and at least 0.2 to 2.0% by mass of a high-melting metal oxide and produced by a mechanical alloying method is subjected to hot isostatic pressing. A method of manufacturing an oxide dispersion strengthened chromium-based alloy, comprising a step of heating at a temperature of 1400 ° C. or higher in an inert gas.