KR20200122656A - Manufacturing method for oxide dispersion strenthening alloys - Google Patents

Abstract

The present invention relates to a method for manufacturing an oxide dispersion strengthening alloy, which previously alloys a highly active metal to a base metal, carbonizes or hydrogenates the highly active metal to form a ceramic phase, and selectively oxidizes the ceramic phase to produce an alloy, thereby suppressing the growth of oxide particles and the base metal. The present invention comprises the steps of: (a) preparing a master alloy by alloying the base metal and the highly active metal; (b) converting the highly active metal into the ceramic phase by carbonizing or hydrogenating the master alloy; and (c) selectively oxidizing the ceramic phase.

Description

Manufacturing method for oxide dispersion strenthening alloys}

The present invention relates to a method for producing an oxide dispersion-reinforced alloy, and more particularly, a high active metal is prealloyed to a base metal, and then the high active metal is carbonized or hydrogenated to form a ceramic phase, and the ceramic phase is selected again. It relates to a method for producing an oxide dispersion-reinforced alloy capable of suppressing the growth of oxide particles and base metals by preparing an alloy through the step of oxidizing with.

Nickel (Ni) or iron (Fe)-based oxide dispersion strenthening (ODS) alloys are alloys in which oxides are dispersed in a metal matrix to increase strength at room temperature and high temperature.

1 shows a conventional manufacturing process. In general, ODS alloys are known to be reinforced by oxide dispersion and base metal grain refinement because the smaller the oxide particle size, the smaller the particle spacing, which hinders the growth of the base metal grains.

In the conventional ODS alloy manufacturing, when a composite powder is manufactured and sintered through a mechanical mixing process of an alloy of a metal component or pure metal powder and an oxide powder to be dispersed, the oxide dispersed during the sintering process prevents the grain refinement and oxide dispersion of the base metal. Reinforcement is achieved by

Since such a conventional technique sinters the mechanically mixed powder of the component metal and the oxide, there is no chemical reaction between the metal particles (base metal) and the oxide particles, so that the atomic arrangement between the oxide particles and the metal particles is misaligned, which is liable to be mismatched. During sintering, the growth rate of oxides by heating is fast, and the growth of matrix grains is also accelerated due to the reduction of the pinning effect by the oxide particles. Therefore, this coarsening of oxide particles and matrix grains is pointed out as a factor that reduces the reinforcing effect, and this has a negative effect on high temperature stability (high temperature strength, high temperature durability, etc.). However, by adding an element such as titanium (Ti) or aluminum (Al) to form a composite oxide at the interface between the oxide and the matrix, a matched or semi-matched structure in which the atomic arrangement between the oxide particles and the matrix is connected is obtained. However, in this case, the size of the oxide particles is non-uniform, the fraction of unconformed oxide particles is high, and there is a limit to maximizing the reinforcing effect.

Therefore, there is a need for a new manufacturing process capable of maximizing reinforcement and high temperature stability by inhibiting the growth of oxide and matrix grains by imparting matching or semi-consistency between the oxide and the matrix in the raw material powder manufacturing step before sintering.

(0001) Korean Patent Application Publication No. 10-1992-0019958 (0002) Korean Patent Application Publication No. 10-2009-0086685

In order to solve the above problem, the present invention forms a ceramic phase by prealloying a high active metal to a base metal, then carbonizing or hydrogenating the high active metal, and selectively oxidizing the ceramic phase again. By manufacturing an alloy, it is intended to provide a method of manufacturing an oxide dispersion-reinforced alloy capable of suppressing the growth of oxide particles and base metals.

In order to solve the above problems, the present invention comprises the steps of: (a) preparing a master alloy by alloying a base metal and a highly active metal; (b) converting the highly active metal into a ceramic phase by carbonizing or hydrogenating the master alloy; And (c) it provides a method for producing an oxide dispersion-reinforced alloy comprising the step of selectively oxidizing the ceramic phase.

The base metal may be nickel (Ni) or iron (Fe), and the highly active metal may be yttrium (Y) or titanium (Ti).

In the step (b), carbonization or hydrogenation may be performed through carbonization milling or hydrogenation milling.

The carbonization milling or hydrogenation milling has a weight ratio of the milling ball: the master alloy of 10:1 to 20:1, and may be performed for 20 to 30 hours.

The selective oxidation of step (c) may be performed by first heat treatment for 2 to 5 hours at a temperature of 500 to 800°C in an air atmosphere, and then secondary heat treatment for 30 to 90 minutes at a temperature of 500 to 800°C in a hydrogen atmosphere. .

The present invention also provides an oxide dispersion-reinforced alloy prepared by the above method.

The method for producing an oxide dispersion-reinforced alloy according to the present invention comprises a step of prealloying a highly active metal to a base metal, then carbonizing or hydrogenating the highly active metal to form a ceramic phase, and then selectively oxidizing the ceramic phase again. By preparing the alloy, it is possible to suppress the growth of oxide particles and the base metal, so that it is possible to manufacture an alloy having high compressive strength and hardness.

1 schematically shows a method of manufacturing a conventional oxide dispersion-reinforced alloy.
2 is a schematic view of a method of manufacturing an oxide dispersion-reinforced alloy according to an embodiment of the present invention.
3 is a schematic diagram of a method of manufacturing an oxide dispersion-reinforced alloy according to an embodiment of the present invention.
4 is a flow chart showing a method of manufacturing a Ni-TiO2 based oxide dispersion reinforced alloy according to an embodiment of the present invention.
5 is a graph showing the size of oxide particles and the average distance between particles in the Ni-TiO2 oxide dispersion-reinforced alloy according to an embodiment of the present invention.
6 is a graph comparing the grain size of a base metal in a Ni-TiO2 oxide dispersion reinforced alloy according to an embodiment of the present invention.
7 is a graph comparing compressive strength and hardness of a Ni-TiO2 based oxide dispersion strengthened alloy according to an embodiment of the present invention.
8 is a flow chart showing a method of manufacturing a Ni-Y2O3 based oxide dispersion reinforced alloy according to an embodiment of the present invention.
9 is a graph comparing the grain size of a base metal in a Ni-Y2O3 based oxide dispersion reinforced alloy according to an embodiment of the present invention.
10 is a graph comparing compressive strength and hardness of a Ni-Y2O3 based oxide dispersion reinforced alloy according to an embodiment of the present invention.
11 is a flow chart showing a method of manufacturing a Ni-Cr-Al-Ti-Y2O3-based oxide dispersion-reinforced alloy according to an embodiment of the present invention.
12 is a graph showing a Ni-Cr-Al-Ti-Y2O3 system high-temperature compressive stress-strain curve according to an embodiment of the present invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail. In describing the present invention, when it is determined that a detailed description of a related known technology may obscure the subject matter of the present invention, a detailed description thereof will be omitted. Throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components, unless otherwise stated.

The present invention is intended to illustrate specific embodiments and to be described in detail in the detailed description, since various transformations can be applied and various embodiments can be provided. However, this is not intended to limit the present invention to a specific embodiment, it should be understood to include all conversions, equivalents, or substitutes included in the spirit and scope of the present invention.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present invention, terms such as include or have are intended to designate the presence of features, numbers, steps, actions, components, parts, or a combination of them described in the specification, and one or more other features, numbers, and steps. It is to be understood that it does not preclude the possibility of the presence or addition of, operations, components, parts, or combinations thereof.

The present invention comprises the steps of: (a) preparing a master alloy by alloying a base metal and a highly active metal; (b) converting the highly active metal into a ceramic phase by carbonizing or hydrogenating the master alloy; And (c) selectively oxidizing the ceramic phase (see FIG. 2).

The step (a) is a step of preparing a master alloy by alloying a base metal and a highly active metal. In the case of the conventional oxide dispersion strengthened (ODS) alloy, the metal oxide is mechanically mixed and dispersed, but in the present invention, it is converted to a metal oxide. The high active metal to be formed is mixed with the base metal through an alloying process to prepare a master alloy, and the high active metal is oxidized to prepare an ODS alloy (1 in FIG. 3).

Nickel (Ni) or iron (Fe) may be used as the base metal. The base metal is preferably a metal that is difficult to hydrogenate or carbonize compared to the highly active metal. In the case of general metals, most of the oxidation is easily performed, but it is known that in the case of formation of carbides or hydrides depending on the metal, the activity is different depending on the type of each metal. Accordingly, in the present invention, nickel or iron, which is a metal that is difficult to be carbonized or hydrogenated, is used as a base metal, and carbonization or hydrogenation can be selectively performed on only a highly active metal, and thus oxide formation can be selectively formed.

The highly active metal may be yttrium (Y) or titanium (Ti). As also described in the base metal, it is preferable to use yttrium or titanium for easy formation of carbides or hydrides as the highly active metal. In the case of such carbides or hydrides, it is possible to convert to oxides through the following steps, and as a result, it is possible to manufacture an ODS alloy by selectively converting the highly active metal into oxides.

The step (b) is a step of converting the highly active metal into a ceramic phase by carbonizing or hydrogenating the mother alloy, and the carbonization or hydrogenation may be performed through carbonization milling or hydrogenation milling (2 in FIG. 3). In the case of the highly active metal component of the master alloy, a metal easily carbonized or hydrogenated as described above may be used. Therefore, when performing a carbonization or hydrogenation process on such a master alloy, the highly active metal may preferentially form a carbonization or hydride (ceramic phase). Looking at this process in detail, after powdering the alloyed metal phase (Ni ₄ Y, Ni ₃ Ti, Fe ₂ Y, FeTi, etc.) in step (a), the weight ratio of the milling ball: the master alloy is 10:1 to 20 :1 Preferably it is charged to the milling machine at a weight ratio of 10:2 to 20:2, and milling is performed for 20 to 30 hours to form hydrides or carbides (ceramic phase, YH ₂ , TiH ₂ , TiC, etc.) have.

The step (c) is a step of selectively oxidizing the ceramic phase, and is a step of selectively oxidizing the hydride or carbide generated by the milling in step (b) (③ in FIG. 3). In the step (c), since oxidation of the ceramic phase generated while suppressing the oxidation of the base metal should be performed, the first heat treatment is performed at a temperature of 500 to 800°C for 2 to 5 hours in an air atmosphere, and then 500 to 800°C in a hydrogen atmosphere. It is preferable to perform the secondary heat treatment at a temperature of 30 to 90 minutes. At this time, when the temperature of the first heat treatment is less than 500°C or less than 2 hours, the ceramic phase is not converted to oxide, and when the heat treatment exceeds 800°C or more than 5 hours, the base metal may be oxidized. In addition, the secondary heat treatment is performed to prevent oxidation of the base metal contained in the mother alloy. If the heat treatment is performed for less than 30 minutes, oxidation of the base metal may occur. If the heat treatment is performed for more than 90 minutes, there is no further effect. Only manufacturing costs can be consumed.

Thereafter, component elements (Cr, Al, Ti Ni, Mg, etc.) are added to the intended composition in the same manner as in the conventional process, mechanical alloying is performed, and then sintered to produce a final product or an intermediate product (see FIG. 3). .

The present invention also relates to an oxide dispersion-reinforced alloy produced by the above method.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement them. In addition, in describing the present invention, when it is determined that a detailed description of a related known function or a known configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. In addition, certain features presented in the drawings are enlarged or reduced or simplified for ease of description, and the drawings and their components are not necessarily drawn to scale. However, those skilled in the art will readily understand these details.

<Example 1>: Ni-TiO ₂ ODS alloy production

Figure 4 briefly shows the method of strengthening the dispersion of TiO ₂ in pure nickel.

In Example 1, powder particles coexisting in the base metal Ni and TiC were prepared by using carbonization milling in the ② recomposition process of FIG. 3. Thereafter, these powder particles were selectively oxidized, and then Ni powder was added to suit the target composition, and mechanically alloyed and sintered (NT-a).

For comparison with the present invention, the powder prepared by the conventional process was compared by sintering under the same conditions (NT-c).

Experimental Example 1

As a result of TEM observation analysis of the raw material powder before sintering, the NT-a powder according to Example 1 of the present invention was able to confirm the formation of semi-matching at the Ni(111) surface/TiO ₂ (111) interface in the oxide particles of 3 to 5 nm size. . On the contrary, in the case of the NT-c powder manufactured by the conventional method, it was confirmed that all oxide particles exhibited a mismatched interface.

5 shows the particle size and average distance between the particles of the Ni-TiO ₂ ODS metal oxide prepared according to Example 1 of the present invention. Example 1 It was confirmed that the oxide particle size and interparticle distance of NT-a exhibited a smaller value over the entire sintering temperature range than NT-c, which means that the dispersed oxide was relatively micronized.

6 is a graph comparing base metal grain size comparison. It was also confirmed that the known crystal grain size showed a smaller value in the entire sintering temperature range than NT-c in the oxide grain size and inter-particle distance of NT-a. The above result means that the pinning effect is maximized due to the reduction in the oxide particle size and the distance between particles.

7 is a graph comparing compressive strength and hardness of NT-a and NT-c samples. It was confirmed that the compressive strength and hardness of NT-a showed higher values over the entire sintering temperature range than NT-c. This means that both the oxide dispersion strengthening (Orowan strengthening) and the strengthening by base metal grain boundaries (Hall-Petch strengthening) of the NT-a sample are relatively excellent.

<Example 2>: Ni-20wt%Cr-1.0wt% Y ₂ O ₃ ODS alloy production

Figure 8 shows the Ni-20wt%Cr-1.0wt% Y ₂ O ₃ ODS alloy manufacturing process. In this Example 2, powder particles coexisting with Ni and YH _{2 as} a base metal were prepared by using hydrogen milling in the ② Recomposition process of FIG. 3. Thereafter, these powder particles were selectively oxidized and converted into powder particles in which Ni and Y ₂ O ₃ phases, which are known metals, coexist, and then Ni and Cr powders were added to suit the target composition, and then mechanically alloyed and sintered (NY-a).

For comparison with the present invention, the powder prepared by the conventional process was compared by sintering under the same conditions (NY-c).

Experimental Example 2

Table 1 is a comparison of the oxide particle size and the average distance between the particles in the Ni-20wt%Cr-1.0wt% Y ₂ O ₃ ODS alloy prepared in Example 2. Regardless of the sintering temperature, it can be seen that the oxide particle size and inter-particle distance of NY-a are smaller than NT-c over the entire sintering temperature range. This means that the dispersed oxide is relatively micronized.

Temp(℃)
sample 850 1000 Particle size (nm) Particle distance (nm) Particle size (nm) Particle distance (nm) NY-c 23 50 45 75 NY-a 16 40 30 55

9 is a result of comparing the grain size of the base metal of the Ni-20wt%Cr-1.0wt% Y ₂ O ₃ ODS alloy according to the sintering temperature. It can be seen that the known grain size also exhibits a smaller value in the entire sintering temperature range than NY-c in the oxide particle size and inter-particle distance of NY-a.

10 is a comparison of the compressive strength and hardness of the samples NY-a and NY-c. It can be seen that the compressive strength and hardness of NY-a exhibited higher values over the entire sintering temperature range than NY-c. This means that both the oxide dispersion strengthening (Orowan strengthening) and the strengthening by base metal grain boundaries (Hall-Petch strengthening) of the NY-a sample were relatively excellent.

Meanwhile, as a result of TEM observation analysis, the NY-a sample sintered at 1000°C was Ni-Cr(111)//Y ₂ O ₃ (422) and Ni-Cr(111)//Y ₂ O ₃ ( 433) It was confirmed that each was in a semi-aligned state at the interface. However, in the case of NT-c powder, it was confirmed that it was in a state of mismatch at the oxide interface regardless of the particle size.

<Example 3>: Ni-20wt%Cr-0.3wt% Al-0.5wt% Ti-0.6wt% Y ₂ O ₃ Preparation of ODS alloy

Figure 11 shows the Ni-20wt%Cr-0.3wt%Al-0.5wt%Ti-0.6wt%Y ₂ O ₃ ODS alloy manufacturing process. In this Example 3, powder particles coexisting with Ni and YH ₂ phases were prepared by using hydrogen milling in the ② Recomposition process of FIG. 3. Then, these powder particles were selectively oxidized to convert them into powder particles in which Ni and Y ₂ O ₃ phases, which are known metals, coexist, and then Ni, Cr, Al, and Ti powders were added to suit the target composition, and then mechanically alloyed and sintered (MA -a)

For comparison with the present invention, the powder prepared by the conventional process was sintered under the same conditions and compared (MA-c).

Experimental Example 3

Table 2 is a comparison of the oxide particle size and the average distance between the particles in the Ni-20wt%Cr-0.3wt% Al-0.5wt% Ti-0.6wt%Y ₂ O ₃ ODS alloy sintered at 1100 ℃. It was confirmed that the size of the oxide particles of MA-a and the distance between the particles were smaller than those of MA-c, which means that the dispersed oxides were relatively micronized.

Particle size (nm) Particle distance (nm) MA-c 48 60 MA-a 32 53

Table 3 shows the results of comparing the grain size of the base metal of the MA-a and MA-c ODS alloy samples sintered at 1100°C. As for the known grain size, it was confirmed that the oxide particle size and inter-particle distance of MA-a were smaller than those of MA-c in the entire sintering temperature range.

Base metal grain size (nm) MA-c 301 MA-a 183

Table 4 is a comparison of compressive strength and hardness of MA-a and MA-c samples sintered at 1100°C. It can be seen that the compressive strength and hardness of MA-a are higher than those of MA-c. This means that both the oxide dispersion strengthening (Orowan strengthening) and the strengthening by the base metal grain boundary (Hall-Petch strengthening) of the MA-a sample are relatively excellent.

Compressive yield strength (Mpa) Hardness (Hv) MA-c 1395 417 MA-a 1653 492

Table 5 is a comparison of high-temperature compressive strength and elongation hardness of MA-a and MA-c samples sintered at 1100°C. Even at high temperatures, the compressive strength of MA-a showed a higher value than M-c, and in the case of elongation, it was confirmed that MA-a showed a lower value than M-c.

Temp(℃)
sample High temperature compressive strength (Mpa) Elongation (%) Room temperature 750 850 Room temperature 750 850 MA-c 1395 605 437 7.5 13 19 MA-a 1653 833 651 5.5 10 14.5

12 shows a high temperature compressive stress-strain curve. Relatively low temperature (a) shows higher stress and lower plastic strain than high temperature (b). In addition, it can be seen that the compressive stress of MA-a is higher than that of M-c at all temperatures.

Meanwhile, as a result of TEM observation analysis, Ni-Cr(111)//YTiO ₃ (220), Ni-Cr(111)//YAiO ₃ (110) and Ni in oxide particles of less than 6 nm even in MA-c samples sintered at 1100°C. -Cr(111)//YTiO(220) was confirmed to be in a semi-matched state at the interface. In the case of the oxide size of 6 nm or more and the single oxide such as Y ₂ O ₃ , all were mismatched, and all semi-matched were confirmed to be composite oxides. It was confirmed that Al and Ti can be added to impart interface consistency in the case of Al and Ti due to the addition of Al and Ti.

On the other hand, in the MA-a sample, Ni-Cr(111)// YTiO ₃ (220), Ni-Cr(111)//YAiO ₃ (110) and Ni-Cr(111)//YTiO(220) of oxide particles of 6 nm or more ) It was confirmed that the interface also showed semi-conformity. This means that the high temperature stability of the oxide interface is improved. In addition, in the MA-a sample, the Ni-Cr(111)//Y ₂ O ₃ (440) interface, which is a monooxide interface, also showed semi-matching. As a result of measuring the volume fraction of the semi-matched oxide, MA-a was 40.7% and MA-c was 13.7%, indicating that the MA-a sample formed much more semi-matched interfaces. This means that the dispersion strengthening effect of the ODS alloy of the present invention process is excellent, and the high temperature stability of the oxide interface is also very excellent.

As described above, specific parts of the present invention have been described in detail, and it will be apparent to those of ordinary skill in the art that these specific techniques are only preferred embodiments, and the scope of the present invention is not limited thereby. will be. Accordingly, it will be said that the substantial scope of the present invention is defined by the appended claims and their equivalents.

Claims (6)

(a) preparing a master alloy by alloying a base metal and a highly active metal;
(b) converting the highly active metal into a ceramic phase by carbonizing or hydrogenating the master alloy; And
(c) selectively oxidizing the ceramic phase;
Oxide dispersion-reinforced alloy manufacturing method comprising a.
The method of claim 1,
The base metal is nickel (Ni) or iron (Fe), and the highly active metal is yttrium (Y) or titanium (Ti).
The method of claim 1,
In the step (b), carbonization or hydrogenation is carried out through carbonization milling or hydrogenation milling.
The method of claim 3,
The carbonization milling or hydrogenation milling is a method for producing an oxide dispersion-reinforced alloy, characterized in that the weight ratio of the milling ball: the master alloy is 10:1 to 20:1, and is performed for 20 to 30 hours.
The method of claim 1,
The selective oxidation of step (c) is characterized in that the first heat treatment is performed for 2 to 5 hours at a temperature of 500 to 800°C in an air atmosphere, and then the secondary heat treatment is performed for 30 to 90 minutes at a temperature of 500 to 800°C in a hydrogen atmosphere. Oxide dispersion reinforced alloy manufacturing method using.
An oxide dispersion-reinforced alloy manufactured by the method of any one of claims 1 to 5.

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