JPS60245767A - Metal dispersion strengthened ceramics and its production - Google Patents

Abstract

PURPOSE:To obtain a titled strengthened ceramics having improved toughness and strength by dispersing unreacted metals into the matrix obtd. by subjecting a powder mixture composed of selected metallic elements and non-metallic elements to exothermic reaction under high pressure and sintering the same. CONSTITUTION:Respective powders of >=1 kinds of metallic elements selected from Groups III, IVa, Va and VIa and >=1 kinds of non-metallic powders selected from B, C, Si and N are mixed at the ratio at which the metallic powder is more than the stoichiometric compsn. Such powder mixture is subjected to the exothermic reaction under the high pressure to synthesize the ceramics. The powder is sintered by the reaction heat so that the unreacted metals are diffused into the ceramic matrix. The dispersed metallic particles are chemically securely bound with the ceramics. The metal dispersion-strengthened ceramics has high hardness and wear resistance and has an excellent high-temp. characteristic and corrosion resistance as well.

Description

[Detailed Description of the Invention] (a) Technical Field The present invention improves toughness and strength by incorporating spherical metal particles in a ceramic matrix that are chemically strongly bonded to the ceramic matrix. This invention relates to ceramics and their manufacturing method.

The energy required to sinter this metal dispersion strengthened ceramic is supplied by the reaction heat generated when combining metal and non-metal elements to synthesize ceramic nox. Dispersion of metal particles is 1
It is unique in that it is completed in two steps at the same time.

(b) Problems with the conventional technology Ceramics generally have higher hardness (and better wear resistance) than metals, so they are used in processing tools and sliding parts that are subject to significant wear compared to metals.

At this time, the most important issues when using ceramics are strength and toughness. Strength and toughness, in turn, lead to material reliability.

Most ceramics are coexisting islands, have a modulus of elasticity several times higher than metals, and hardly cause either elastic or plastic deformation.

For this reason, it is extremely sensitive to defects inside the sintered body, and once cracks begin to develop, it is almost impossible to stop them midway, resulting in destruction. This point is the biggest difference from metals, and various attempts have been made to date to improve the brittleness of ceramics.

One of these attempts to stop the propagation of a crack by applying compressive stress to the tip of the crack by utilizing the volumetric expansion accompanying the phase transformation of a ceramic dispersed phase, typified by partially stabilized ZrO2. However, with this method, phase transformation occurs before stress is applied as the temperature rises, and the toughening mechanism disappears.

Another method is to strengthen ceramic particles such as cermet by bonding them through a metal grain boundary phase. This method has a strong impact buffering effect due to the presence of a highly tough metal phase between the ceramic particles, but when used at high temperatures, the softening of the grain boundary phase or the impact on the overall strength of the cermet is affected. , causing a rapid decrease in strength.

In addition, 5% 1I11 in the matrix of ceramic and camphorax
Research has also been conducted on increasing toughness by dispersing ceramic fibers in the matrix to branch out the propagation of cracks and increase fracture energy. However, the technology to uniformly disperse ceramic fibers is difficult, and The wettability of ceramics and ceramic fibers has not been fully elucidated, and the technology has not yet reached the practical stage.

As mentioned above, various measures have been taken to improve the toughness of currently used ceramics, but they are still insufficient or have sacrificed properties other than fatness. There is.

Considering the conventional technology from the manufacturing method point of view, if one attempts to obtain a ceramic having a structure in which spherical metal particles are dispersed in a ceramic matrix like the present invention,
Conventional methods typically involve sintering a mixture of ceramic powder and metal powder under high pressure. However, the sintering temperature of ceramics is often higher than the melting point of the metal, and in that case, the metal melts during sintering, creating a structure in which the metal fills the spaces between the ceramic particles. A structure in which spherical metal particles are dispersed in a matrix cannot be obtained. On the other hand, even if the melting point of the metal is higher than the sintering temperature of the ceramic, poor wettability between ceramic particles and metal particles will inhibit the M&densification of the ceramic, resulting in a large number of pores remaining in the sintered body. . Furthermore, as the volume fraction of the metal increases, the coalescence of the added metal particles progresses, and a structure in which the metal is finely and evenly distributed is not obtained, but coarse particles of the metal are unevenly distributed! There is a high possibility that it will be a J1 weave.

As mentioned above, with conventional sintering methods, it is difficult to obtain high toughness ceramics in which spherical metal particles are finely and uniformly dispersed as in the present invention. In view of the above-mentioned problems, the present inventors conducted research and development on a method for sintering high-toughness ceramics dispersed and strengthened by metal particles, and as a result, they arrived at the present invention.

(C) Disclosure of the Invention The biggest difference between the present invention and conventional ceramic composite materials is that the composite material is not obtained by sintering a mixture of ceramic powder and a dispersion material such as metal, but by combining metal powder and non-dispersed material. During simultaneous sintering of ceramics from metal elements, by reacting a mixture containing metal in excess of the stoichiometric composition, unreacted metal particles are uniformly dispersed in the ceramic matrix after sintering. It is in.

As mentioned in the section on problems with conventional technology, when a mixture of ceramic powder and metal powder is used as a starting material, there are problems with the melting point and sintering temperature of the metal, and problems with the wettability of ceramic particles and metal particles. There are many problems such as the formation of coarse particles due to coalescence of metal particles. In contrast, in the present invention, these problems can be solved by utilizing simultaneous sintering of ceramics.

First, there is the issue of the melting point and sintering temperature of metals. Even if the simultaneous sintering temperature of ceramics is higher than the melting point of metals, metal particles that are in contact with nonmetallic elements during the ceramics synthesis process are removed from the surface. Ceramicization progresses inward, so even if the temperature temporarily exceeds the melting point of the metal, the metal will melt inside the ceramic shell and will not flow out of the shell. Therefore, after cooling, a structure in which spherical metal particles are dispersed in the ceramic matrix can be obtained.

For example, considering the case of producing a composite material in which spherical metal Ti is dispersed in a TiB2 matrix, T i +2B + T i B2 + 70.0Kcaj
! 7moL (288°K)---(1) As shown in equation (1), 70.0Kca2/m with the production of TiB2
The heat of reaction is generated. For this reason, if a powder mixture of Ti and B to which Ti is added in excess of the chemical composition is consolidated under pressure, a portion of the mixture is heated and ignited to force the reaction of formula (1) to start. Next, the reaction heat generated causes adjacent parts to start reacting one after another, and the chain reaction progresses to the entire powder compact, completing the synthesis and sintering of the ceramic at the same time. When TiB2 is generated, it is thought that the temperature exceeds 2000° C., albeit temporarily. Therefore, the metal Ti that is added in excess of the stoichiometric composition and does not participate in the synthesis reaction of 'rtB2 may be temporarily melted, but the metal T
The outer shell of i changes to TiB2 and prevents the molten Tj from flowing between the particles, so after cooling, spherical metallic Ti particles are dispersed in the gray ceramic matrix as shown in Figure 1. The tissue obtained is as follows. Figure 1 shows TiB
This figure shows how metal TI particles are dispersed in the matrix of z.

Regarding the wettability of the matrix ceramic and the dispersed metal particles, ceramicization progresses from the surface of the metal particle toward the inside, and this outer ceramic shell is sintered to form the matrix. The wettability of the dispersed particles is very good, and they are also strongly chemically bonded.

As shown in Figure 1, the matrix of TiB2 and the metal T
i The dispersed particles are firmly bonded without any gaps.

Furthermore, according to the synthesis and simultaneous sintering method of the present invention, the excess 11 parts that do not contribute to the synthesis reaction of ceramics during sintering are TiB2
Since the metal particles are separated by the outer shell, there is a low probability of direct contact, which has the advantage that the metal particles are less likely to become coarse. As shown in FIG. 1, most of the dispersed particles of metallic Ti exist independently.

The metal dispersion-strengthened ceramics produced in the above manner have extremely high hardness and excellent wear resistance because the matrix is ceramic, and at the same time, the dispersed metal particles resist impact forces. Is it durable because it acts as a material? l17 attack power has been improved to +11. Furthermore, by dispersing metal particles with low hardness in a matrix with high hardness, there is a high possibility that the sliding properties will be improved. In fact, the coefficient of friction is smaller than that of ceramics alone, which does not contain dispersed metal particles.

Regarding high-temperature strength, cermets have the disadvantage that high-temperature strength rapidly decreases due to the softening of the metal grain boundary phase existing between ceramic particles, but in the metal dispersion-strengthened ceramic of the present invention, Since the existing skeleton is ceramic, the rate of decrease in strength and hardness at high temperatures is very small compared to cermet.

Regarding corrosion resistance, when metal exists in continuous grain boundaries like cermet, the metal grain boundary phase is preferentially corroded by acid or alkali, making it impossible to hold the ceramic particles together, making it difficult to feed food. However, in the metal dispersion-strengthened ceramic of the present invention, the matrix is a ceramic with excellent corrosion resistance, and metals that are susceptible to corrosion are protected by the ceramic matrix, so they cannot be used directly in corrosive atmospheres. Since there is no contact with the metal, corrosion resistance is also improved.

As described above, the metal dispersion-strengthened ceramic of the present invention has the advantages of ceramics, such as high hardness and excellent wear resistance, high-temperature properties, and corrosion resistance, as well as high toughness and excellent impact resistance. It is a material that has the advantages of other metals.

The present invention will be explained below with reference to Examples.

Example 1 - 71.85 g of 325 mesh metal Ti powder (1,5
mole) and B powder 21. with an average particle size of 1.0 μm. [i2g
After mixing (2 moles), a portion of this powder was molded into a cylinder with a diameter of 5 and a height of 5 fins using a mold press at a pressure of 2 tons/c♂. After storing this molded body in a BN container, the molded body was placed in an ultra-high pressure generator with the upper end surface in contact with a carbon heater, and while pressurized to 30,000 atmospheres, the carbon heater was energized and ignited. . The current was cut off immediately after the TiBz production reaction started.

Gold g4Ti dispersion strengthened TiB2 obtained as above
The density of the sintered body was 99.4% of the theoretical density.

The structure inside the sintered body at this time is shown in FIG.

As a result of analysis by E PMA, the particles dispersed in FIG. 1 were gold WA Tf N matrix was TiB2.

Example 2 A total of 239.85 g of 1 im Mo powder (
2.5 mol) and average particle size 1.0 μm (7) C powder +z
, otg (1 mol I) was combined, and then vacuum sealed in a Mo sealed container. A carbon heater was built into this sealed container as an igniter, and a lead wire was taken out of the container. This sealed container was placed in a high-pressure generator, and while the sealed container was preheated to 800°C and pressurized with 2000 atm Ar gas, the carbon heater was ignited by electricity.The current was cut off as soon as the MO2C production reaction started. did.

The density of the metallic Mo dispersion-strengthened MO2C sintered body obtained as described above was 991% of the theoretical density.

As a result of X-ray diffraction of this sintered body, peaks of Mo2C and Mo corresponding to approximately the same molar ratio were observed.

[Brief explanation of drawings]

Figure 1 shows TiB2-T produced according to an example of the present invention.
This is a micrograph of i-based dispersion-strengthened ceramics magnified 1000 times. Engraving of the drawing (no change in content) 1 diagram 100O Continuation of the 1st page ■Int, CI,' Identification symbol Internal organization - ■Inventor
Eiji Kamijo 1-1-1 Uchikita, Konkuni Seisakusho, Itami City Sumitomo Electric Industries, Ltd. Itami Procedural Amendment Form) September 1981/δ Date Commissioner of the Patent Office Manabu Shiga 2, Name of the invention: Metal dispersion strengthening Ceramics and Their Manufacturing Act 3, Relationship with the Amendment Person Case Name of Patent Applicant: 5-15 Kitahama, Higashi-ku, Osaka Name (213)
) President of Sumitomo Electric Industries, Ltd. Tetsube 4, agent address: 1-1-3 Shimaya, Konohana-ku, Osaka City, Sumitomo Electric Industries, Ltd. "Application", "Brief explanation of drawings" in the description column, and “Drawing”. 7. Contents of the amendment (1) We will submit an "application" with the exact title of the invention as attached. (2) On page 14, line 11 of the specification, between “no” and “rlo00 times”, metal Ti is present in rTiBQ.
Insert the sentence ``In an organization where the organization is dispersed.'' (3) We will submit the correct "drawings" as attached.

Claims (6)

[Claims] (1) Group m, Group 1 Va, Group Va, and Vl of the periodic table
At least one metal element selected from group a and B, C, N
. The matrix is a ceramic synthesized by an exothermic reaction from a mixture consisting of at least one nonmetallic element selected from the group consisting of Si, and metal particles identical to the metal constituting the ceramic are dispersed in this matrix. Metal dispersion-strengthened ceramics are characterized by a strong chemical bond between the two. (2) The metal dispersion-strengthened ceramic according to claim 1, wherein the dispersed metal particles are generally spherical. (3) The metal dispersion-strengthened ceramic according to claim 1, wherein the volume fraction of the dispersed metal particle phase is 70% or less. (4) Group ■, Group 1 Va, Group Va, and Vi of the periodic table
At least one metal element selected from group a and B+C+S
i. A powder mixture of at least one nonmetallic element selected from N containing more metal powder than the stoichiometric composition obtained from both is reacted under high pressure by an exothermic reaction to form a ceramic. 1. A method for producing metal dispersion-strengthened ceramics, which comprises synthesizing and sintering unreacted metals in the matrix of the ceramic or matrix. (5) At least one metal element selected from Group ■, Group ■a, Group Va, and Group ■a of the periodic table and B+C+S l
A powder mixture of at least one nonmetallic element selected from The matrix is made of ceramics, which are characterized by the ability to induce a reaction in order to cause the entire molded body to react, leading to sintering.In this matrix, the same metal particles as the metal constituting the ceramic are dispersed, and both are strongly chemically bonded. A method for producing metal dispersion strengthened ceramics characterized by bonding to. (6) Group ■, Group 1 Va, Group Va, and Vl of the periodic table
At least one metal element selected from group a and B+C+S
Occurs when synthesizing ceramics by reacting a powder mixture of at least one nonmetallic element selected from I+N with a mixture containing more metal powder than the stoichiometric composition obtained from both. The reaction heat is mainly used to start the reaction without adding external heat or at a temperature far lower than the synthesis temperature of ordinary ceramics.
Ceramics that are characterized by being sintered are used as matrices and laths, and metal particles identical to the metal constituting the ceramics are dispersed in the matrices and laths, and the two are strongly chemically bonded. A method for producing metal dispersion-strengthened ceramics characterized by: