JPH01275724A - Manufacture of dispersion strengthened heat-resistant alloy - Google Patents

Abstract

PURPOSE:To reduce the oxygen content in the title alloy and to improve its mechanical characteristics by incorporating Y or Th to a starting material essentially consisting of Ni or Fe, subjecting it to alloying treatment, forming oxide therein, thereafter solidifying it and uniformly dispersing fine oxide into the alloy. CONSTITUTION:Material powder consisting essentially of Ni or Fe powder and contg., by weight, 0.1-1.5% Y or 0.6-4.5% Th is subjected to machanical alloying treatment to uniformly disperse Y2O3 or Th2O3 into multiple powder in the fine state. The multiple powder is solidified by the means of HIP and so on to manufacture an alloy in which fine grains of Y2O3 and Th2O3 are uniformly dispersed into a mother phase. If required, one or more kinds among Cr, Mo, W, Ta, Nb, Al, Ti, Zr, C and B are incorporated to the material powder in such a manner that 5-30% Cr, 2.5-10% Mo+W, <=6% Ta+Nb, <=10% Al+Ti, <=3% Zr and <=0.2% C+B are regulated. The O2 content in the mother phase is preferably regulated to <=500ppm. The dispersion strengthened heat- resistant alloy has high value in the characteristics of fatigue service life, toughness, etc., while maintaining high creep resistance.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for manufacturing a dispersion-strengthened heat-resistant alloy used for high-temperature, high-pressure blades or combustion liners of aircraft engines and gas turbines, and high-temperature machining tools. Regarding °
In particular, the present invention relates to a method for producing a Ni-based or Fe-based dispersion-strengthened heat-resistant alloy with excellent high-temperature strength.

[Prior Art] As a method for manufacturing Ni-based or Fe-based dispersion-strengthened alloys with excellent high-temperature strength, a method using powder metallurgy technology called a mechanical alloying method has been known, for example, as disclosed in U.S. Pat. No. 3,776.704, No. 3.728,088, 3,
No. 926,568, etc. In this method, Ni.

Metal powder raw materials such as Fe, Mo, W, Nb, Ti, AI, Cr, etc. and fine oxide powders such as T h O2+ A I 203 (partly La2O3 may be used) and Y2O3 are processed in a dry attritor type ball mill, etc. As a typical example, a composite metal powder having a controlled uniform and fine microstructure is produced by crushing, mixing, and recombining in a high-impact crusher. After degassing, this composite powder is HI
It is solidified by known techniques such as P (hot isostatic pressing) and hot extrusion, and further annealed to form an alloy in a desired shape with oxides dispersed therein, which is ready for use. Dispersion-strengthened alloys produced in this way do not include a melting process in the alloying process, so the dispersed oxide particles exist in a uniformly dispersed state, and the metal alloy components are also finely and uniformly distributed, preventing segregation. This has the advantage of not causing any

[Problems to be Solved by the Invention] By the way, in oxide dispersion strengthened alloys, it is essentially important to control nonmetallic components such as oxides and nitrides, and in particular,
When used as a Ni-based super super heat-resistant alloy, it is particularly necessary to control oxygen to an extremely low level. However, in the conventional techniques described above, contamination of the powder with oxygen and an accompanying increase in the oxygen concentration in the alloy are unavoidable. In other words, if the atmosphere during mechanical alloying treatment contains oxygen or if a large amount of oxygen adheres to the surface of the raw powder particles,
Since that oxygen is taken into the composite powder and causes Meda dyeing, it is possible to carry out mechanical alloying treatment using extremely clean raw materials in an atmosphere with very little oxygen, but there is no oxygen at all. In an atmosphere, the powder may adhere to the inner wall of the grinding container, or the composite powder particles may grow into giant particles, which may prevent deformation (that is, sintering) of the powder particles during the next solidification process such as HIP. This may cause the inconvenience of not having enough. In order to avoid such a problem, a method of adding an auxiliary agent such as a halide or a metal halide to metal powder or the like may be considered, but this is not preferable as it results in impurities remaining in the alloy. Therefore, the alloying treatment must be carried out in a mixed gas atmosphere containing an inert gas and a trace amount of oxygen gas, which results in a slight increase in the oxygen content in the alloy. High oxygen content in the alloy will reduce the toughness of the alloy, increase the crack propagation rate, increase notch susceptibility, or reduce high and low cycle fatigue strength. The practical upper limit is considered to be 300 to 500 ppHl.

On the other hand, for example, a mixed powder of component metals corresponding to a Ni-based super super heat-resistant alloy and Y2O3 powder are mixed with 0.0% oxygen gas.
When subjected to mechanical alloying treatment using a dry attritor in an argon gas atmosphere containing 0.5%, the amount of oxygen in the composite powder decreased to 500 ppII after 4 hours and 1500 ppII after 24 hours.
ppli also increases.

Y
The oxygen content in the matrix alloy excluding 2O3 oxygen is 2000
This is one of the reasons why it has not yet been put into practical use as aircraft engine blades, although it has been considered a promising candidate for next-generation materials for turbine blades and research has been carried out over a long period to put it into practical use. ing.

As explained above, according to the conventional technology, no matter how low the oxygen content of the raw material powder is controlled, the powder becomes contaminated with oxygen during the mechanical alloying process, making it difficult to obtain a good composite powder. Therefore, the mechanical properties of dispersion-strengthened heat-resistant alloys are insufficient.

This invention was made in view of such circumstances, and
The object of the present invention is to provide a method for manufacturing a dispersion-strengthened heat-resistant alloy with a low oxygen content and excellent mechanical properties.

[Means for Solving the Problems] The method for producing a dispersion-strengthened heat-resistant alloy according to the present invention mainly contains Ni or Fe, and contains 0.1 to 1.5% by weight of Y or 0.6 to 4.5% by weight. A process of alloying raw material powder containing Th by a mechanical alloying method to produce a composite powder containing Y or Th in an oxidized state, and solidifying this composite powder to form a matrix mainly composed of Ni or Fe. It is characterized by comprising a step of forming an alloy in which Y2O3 or Th02 is dispersed.

[Function] When producing a composite powder for a Ni-based or Fe-based heat-resistant alloy by a mechanical alloying method, if an appropriate amount of Th or Y is included in the starting material, it will be mixed in from the atmosphere during the alloying process. Oxygen and these elements combine to form oxides.

By solidifying this composite powder, a heat-resistant alloy in which fine oxides are uniformly dispersed can be obtained. In this way, oxygen in the atmosphere is consumed in forming the oxide dispersed particles, so the oxygen content in the master alloy can be reduced.

In addition, Th and Y, which are not oxidized, effectively act as a solid solution strengthening alloy for the parent phase. Therefore, a dispersion-strengthened heat-resistant alloy with extremely excellent mechanical properties can be obtained.

[Example] This invention will be described in detail below. This invention is applied to oxide dispersion strengthened Ni-based or Fe-based super super heat-resistant alloys. Oxide dispersion strengthened super heat-resistant alloys are disclosed in U.S. Patent No. 3,
As stated in No. 728,088, etc., 600
The creep strength at temperatures between 1100°C and 1100°C is extremely high. This invention can improve other mechanical properties such as fatigue strength and toughness, which conventionally had to be low due to the presence of oxygen, while retaining the advantages of dispersion-strengthened heat-resistant alloys. It is something.

This invention is based on Ni-Cr, Fe-Cr, Ni-Cr-
The composition of the mother alloy does not matter as long as it is a Ni-based or Fe-based heat-resistant alloy such as Mo-based or Fe-Cr-Mo-based, but in particular, Ni3
It is effective for parent alloys containing an intermetallic compound called the so-called γ' phase, such as Al5Ni3 (Al, Ti).

In the method of the present invention, first, as raw material powders, Ni or Fe powder, which is a matrix component, Th or Y powder, and powders of other alloy components as necessary are prepared, and these are mechanically processed. A composite powder is produced by alloying using an alloying method. That is, these powders are mixed and crushed using a mechanical mixing device such as an attritor ball mill, and then the powder particles are recombined to form a composite powder having a controlled uniform and fine microstructure. This mechanical alloying step is preferably carried out in an environment containing a slight amount of oxygen, as described above. Thereby, it is possible to prevent the raw material powder from adhering to the grinding container and from becoming large particles.

During such a mechanical alloying process, oxygen in the atmosphere and oxygen attached to the surface of the raw material selectively combine with Y or Th to form chemically stable Y2O3 or Th201, and these oxides form composite powder. It is evenly dispersed in a fine state.

Note that the amount of Y or Th added at this time is 0.2 to 1.5% by weight for Y and 0.6 to 4.5% for Th.

If the content of these oxides is less than the lower limit of the above range, the dispersion strengthening effect of these oxides will be insufficient, and if it exceeds the upper limit, the toughness will be significantly reduced.

In addition to Ni or Fe, which is the main component, and Y or Th, which forms the dispersed phase, the raw material powder may include, for example, C, Mo, W,
Ta5Nb, Al, Ti5Zr.

A material to which C and B are added can be used.

Among these alloys, Cr is the most important element that imparts corrosion resistance to heat-resistant alloys, but if the amount added is less than 5% by weight, the effect is insufficient, and if it exceeds 25%, the embrittlement phase becomes a matrix. Precipitates in the phase.

Mo and W are elements that contribute to solid solution strengthening of alloys,
If the amount added is less than 2.5%, such effects are insufficient, and if it exceeds 10%, a brittle phase will precipitate in the matrix. Ta
and Nb are effective elements for strengthening the γ′ phase, but 6
If added in excess of %, the alloy becomes brittle and it becomes difficult to form a solid solution.

AI and Ti form a solid solution in the matrix to improve high-temperature oxidation resistance, and in Ni-based alloys, as mentioned above, Ni3
(A I, Ti) plays an important role in high-temperature strengthening by forming phases, but if the amount added exceeds 10%, the volume fraction of γ' reaches 65 to 70%, leading to a reduction in the amount of oxygen. -, the toughness decreases to such an extent that it is difficult to improve it. Zr・
, C and B are elements that contribute to grain boundary and intragranular strengthening through the formation of carbides, borides, etc., but Zr is 0.3%
If C+B exceeds 0.2%, the matrix becomes brittle. Therefore, in weight%, 5≦Cr≦25%, 2.5≦M
o+W≦10%, O<Ta+Nb≦6%, O<A l
+T i≦1026.0<ZrS2.3%, 0<C+B
It is preferable that it is ≦0.2%. In addition to these alloys, 20% or less of Co can also be added. Co
In particular, it has the function of controlling the amount of γ' phase precipitated in the Ni-based alloy, and is effective when the amount is 20% or less. In addition, 0
In the range where these are not included or are added in relatively low amounts, such as ≦Mo+W≦2.5% and 0≦AI+Ti≦2.0%, no brittle phase will occur even if Cr is added up to 30%. Shows good properties.

Note that it is not necessary to include all of these alloying elements;
These elements can also be added in appropriate combinations depending on the intended use of the alloy.

After producing the composite powder as described above, this composite powder is subjected to HI
The alloy is solidified by known means such as P to produce an alloy in which fine particles of Y2O3 or Th2O3 are uniformly dispersed in the matrix. Thereafter, this alloy is processed and annealed if necessary, and then used.

In this case, Y or Th, which forms the dispersed phase of the oxide, is added in the state of metal, and during the mechanical alloying process, it combines with oxygen in the atmosphere or adsorbed on the raw material to form the dispersed phase of the oxide. As a result, the amount of oxygen incorporated into the mother alloy can be reduced compared to the conventional case where oxides are used as dispersed phase raw materials, and the oxygen content in the alloy can be reduced to 5'00p.
It can be extremely reduced to pm or less. In addition, by controlling the amount of oxygen or adsorbed oxygen in the atmosphere,
The amount of oxide dispersed phase can be adjusted to optimize the high temperature strength of the alloy. Furthermore, unoxidized Y and Th
can be made to act effectively as a solid solution strengthening element for the matrix phase.

Next, specific embodiments of the present invention will be described. First, raw material powder having the composition shown in Table 1 was used. Examples 1 to 5 in Table 1 are within the scope of the present invention, and Comparative Examples 1 to 5 are outside the scope of the present invention.

In Table 1, Examples 1 to 3 are the existing dispersion-strengthened heat-resistant alloy Inconel MA6000 using the mechanical alloying method,
MA754, has almost the same composition as MA956 composition,
In Example 4, a considerable amount of Y was added instead of Y203, and T was added to a composition equivalent to Udimet 500, a Ni-based heat-resistant alloy.
Added Th equivalent to 2.0% hO2, Example 5
The amount of ThO is set to such an amount that the amount of Th that is not oxidized remains. On the other hand, Comparative Examples 1 to 3
are Inconel MA6000, MA754, MA9 respectively.
56 composition, Comparative Example 4 is MA956 without Y2O3, Comparative Example 5 is Udimet 500 with ThO2
2% was added.

After processing the raw material powders of each composition under the same conditions, they were mixed and ground in a dry attritor ball mill for 244 hours and mechanically alloyed. At this time, in the case of the example, 99.95% argon gas (oxygen content 500 ppm) was passed through the attritor type mill, and in the case of the comparative example, 99.95% argon gas (oxygen content 500 ppm) was passed through the attritor type mill.
．． 99% arbon gas (oxygen content 10100pp
was passed through. After that, the mechanically alloyed composite powder was
It was degassed and dried at 0°C. Table 2 shows the amount of oxygen in each raw material powder after degassing, the amount of oxygen in the oxide dispersed phase, and the amount of oxygen in the alloy excluding the amount of oxygen in the oxide dispersed phase.

Table 2 As is clear from Table 2, in all of Examples 1 to 5, the amount of oxygen in the alloy excluding the amount of oxygen in the oxide was 0.3% or less, and the amount of oxygen in the comparative example was 0.3% or less. This value was extremely small compared to 5% to 0.7%. That is, Examples 1 to 5
In the case of , the oxygen in the atmosphere and the adsorbed oxygen are Y or Th
In contrast, in the comparative example, oxygen in the atmosphere and adsorbed oxygen remained in the alloy, resulting in a high oxygen content in the alloy. In the Cr-Al-Ti-Fe system of Comparative Example 4, Al2O3
were formed and were uniformly dispersed in a fine state, but the effect similar to that of Y or Th in Examples could not be obtained.

Note that in this example, raw materials in normal storage conditions (for example, stored in a desiccator) were used, but when metal powder was produced, stored, and transported in a controlled atmosphere to prevent exposure to air, Since there is substantially no adsorbed oxygen, it is expected that the amount of oxygen can be reduced to 0.1%.

Also, among the raw material powders, Ta is easily oxidized.

A1% Tt, Zr, Y, Th, etc. were added as intermediate compound powders such as Ni-Ta.

Among the composite powders produced by the mechanical alloying treatment, those passed through an 80-mesh sieve for Example 1 and Comparative Example 1 were placed in an 18% Cr-B% Ni-Fe stainless steel can. After heating and degassing at 500°C, the alloy was vacuum sealed and solidified by hot extrusion at 1050°C to produce an alloy in which fine dispersed phases were uniformly present. After solution annealing this alloy at 1220°C for 1 hour,
Aging treatment was performed at 850° C. for 24 hours.

From these alloys, cylindrical test pieces with a diameter of 1 ofil and a length of 30 mm were extruded from the parallel portion and taken in the longitudinal direction, and these test pieces were subjected to a high temperature low cycle fatigue life test. The results are shown in FIG. FIG. 1 is a graph showing the relationship between these, with the horizontal axis representing the number of repetitions until breakage and the vertical axis representing the total strain range (ΔεT). The white circles are for Example 1, and the black circles are for Example 1. This is the case of Comparative Example 1. The test conditions were a temperature of 750°C and a frequency of 0.33H.
I did it.

From FIG. 1, it was confirmed that Example 1 had a longer high-temperature, low-cycle fatigue life than Comparative Example 1.

In addition, similar test pieces were prepared for Examples 4 and 5 and Comparative Example 5, and the high-temperature, low-cycle fatigue life was determined under the conditions of a temperature of 800° C. and a frequency of 0.33 Hz. The results are shown in Table 3. Note that Table 3 shows cases where Δε is 0.7% and 0.5%.

Table 3 As is clear from Table 3, Examples 4 and 5 had a 30 to 40% higher number of rupture cycles than Comparative Example 5. In other words, it was confirmed that the fatigue life of the material to which Th was added was longer than that to which ThO2 was added. Furthermore,
Comparing Examples 4 and 5, the amount of unoxidized Th remaining is 1. In Example 5, the number of repetitions of rupture is larger. This is due to the solid solution strengthening effect of unoxidized Th.

Next, toughness tests were conducted on the dispersion strengthened alloys having the compositions of Examples 1.4 and 5 and Comparative Examples 1 and 5.

The alloy was manufactured by the method described above, and a V-notch Charpy test piece was prepared with the hot extrusion direction as the longitudinal direction. This test piece was subjected to a Charpy impact test at 0'C to determine the toughness value. The results are shown in Table 4.

Table 4 In Table 4, when comparing the toughness values of Example 1 and Comparative Example 1, which are M A 6000 F[1 materials, Example 1 had a higher toughness value. Also, Th on Udimet 500
In the system in which O2 was added, Examples 4 and 5 showed significantly higher toughness values than Comparative Example 5. Although Example 5 showed a decrease in toughness due to the solid solution strengthening of Th, it exhibited a much higher toughness value than the Comparative Example.

[Effects of the Invention] According to the present invention, when producing a Ni-based or Fe-based dispersion-strengthened heat-resistant alloy, Y or Th forming an oxide dispersed phase is added in a metallic state, and the Y and Th are Since it is selectively oxidized during the mechanical alloying process, the amount of oxygen taken into the matrix alloy can be extremely reduced, and these oxides are finely and uniformly dispersed in the matrix alloy. . Therefore, while maintaining the high creep strength of the Ni-based or Fe-based dispersion-strengthened heat-resistant alloy, it is possible to significantly improve mechanical properties that are adversely affected by oxygen, such as fatigue life and toughness.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the fatigue life of an alloy manufactured according to the present invention in comparison with a conventional heat-resistant alloy. Applicant's agent Patent attorney Takehiko Suzue

Claims (3)

[Claims] (1) Raw material powder mainly composed of Ni or Fe and containing 0.1 to 1.5% by weight of Y or 0.6 to 4.5% by weight of Th is alloyed with Y or Th by a mechanical alloying method. A step of producing a composite powder containing Y in an oxidized state, and a step of solidifying this composite powder to add Y to a matrix mainly composed of Ni or Fe.
A method for producing a dispersion-strengthened heat-resistant alloy, comprising the step of forming an alloy in which _2O_3 or ThO_2 is dispersed. (2) The raw material powder includes Cr, Mo, W, Ta, Nb, A
Contains at least one element selected from the group consisting of Cr, Ti, Zr, C, and B, and the content of these elements is Cr.
is 5 to 30% by weight, and Mo+W is 2.5 to 10% by weight.
, Ta+Nb is 6% by weight or less, Al+Ti is 10% by weight
Below, Zr is 0.3% by weight or less, C+B is 0.2% by weight
The method for producing a dispersion-strengthened heat-resistant alloy according to claim 1, characterized in that: (3) A dispersion-strengthened heat-resistant alloy having an oxygen content of 500 ppm or less in the matrix alloy, which is produced by the production method of item 1.