JPH06321636A - Ceramic composite material - Google Patents

Abstract

PURPOSE: To improve toughness by forming a solid solution ceramic composite material by mixing SiC powder and AlN powder and heating and pressurizing the mixture at a specified temp. and pressure.

CONSTITUTION: The SiC powder and the AlN powder both having 0.5-5 μm particle size are mixed in a specified proportion to form a powdery mixture containing 1-99 wt.% SiC in the AlN. Then the powdery mixture is subjected to hot pressing under a pressure of about 140.6 kg/cm² and at 1,600-1,800°C for 4-6 hr to obtain the ceramic composite material whose one part is the solid solution and which is tough and withstands high temp. And the powdery mixture is subjected to heat sintering under the pressure of about 140.6 kg/cm² and at 1,800-2,300°C for 4-6 hr to obtain the ceramic composite material in which SiC particles and/or AlN particles form a residual phase in a solid solution matrix and which has high multi-hit performance.

COPYRIGHT: (C)1994,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL FIELD OF APPLICATION The present invention relates to solid solutions for use in armor, cutting tools, wear parts, nozzles, parts subject to high temperatures and similar items subject to severe impact or erosion. It relates to the use of silicon carbide / aluminum nitride as a ceramic composite.

 (Prior Art) U.S. Pat. No. 4,141,740 to Cutler et al. Discloses a heat resistant product formed as a solid solution of aluminum nitride, silicon carbide and aluminum oxycarbide and a process for making the heat resistant product. This patent is cited as the background of the technology related to the present invention.

 It is known that silicon carbide ceramic coated armor systems are lightweight and provide essentially better ballistics perfor- mance than monolithic metalic plates. Silicon carbide coated armor systems are better because the ceramics used have greater compressive mechanical properties than metals, especially dynamic compressive yield strength. Furthermore, these ceramics, due to plastic deformation and erosion or fracture, lead to greater projectile deformation than in the case of metals. This increased deformation reduces the bullet's ability to penetrate in two ways. The plastic deformation of the bullet and the resulting erosion reduces the kinetic energy of the bullet by virtue of plastic flow and the reduction of bullet mass. Alternatively, the destroyed bullet is substantially defocused, ie the target material acting against the bullet is increased due to the increased impact area.

 Although silicon carbide ceramic-coated armor systems have known performance over many other systems, they are not currently used in light armored combat vehicles for two main reasons. One is price, that is, typical prices for high performance silicon carbide ceramic materials are currently $ 110.23 to 220.46 / kg ($ 50,00 to 100,00 / 1b). The US Government is currently not willing to pay for the expensive armor systems that result from the application and use of such high-priced ceramics in lightweight armored vehicles. Another reason is the typically poor multi-hit performance of silicon carbide ceramic systems due to the extremely brittle nature of ceramic materials. Silicon carbide ceramic armor systems are typically formed of ceramic plates or "tiles". A bullet impact on one tile is sufficient to destroy that tile, so a second shot cannot prevent penetration. In addition, the impact within the first tile can often cause the destruction of adjacent tiles, weakening their performance and preventing the penetration of bullets anymore. For this reason, there is a limit to the number of bullets that can be blocked in a given area, and the ability to be hit multiple times.

(Means for Solving the Problems) The ceramic composite material of the present invention is used as lightweight armor in order to deflect bullets penetrating armor by erosion and to crush the bullets. It is the main purpose. This composite material can also be used in severe wear, high temperature, abrasive or other severe impact applications.

 When used in lightweight armor, ceramic composites are specially tuned and treated to make the best trade-off between manufacturing cost and performance. More specifically, the composite is composed of a fine structure containing two or three phases containing silicon carbide (SiC), aluminum nitride (AlN) or a solid solution of AlN and SiC.

 With proper selection of powder and firing conditions, one of the following different microstructure types can be produced:

That is, Type 1 consists of a distinct phase of SiC and AlN. Type 2 consists of one solid solution of SiC and AlN. And the type 3 contains AlN or SiC or both AlN and SiC as a residual phase in one solid solution matrix of SiC and AlN.

 Firing may be either sintering or hot pressing, and the temperature and time conditions for firing are control factors for obtaining the desired microstructure.

 Prior to the description of the ceramic composite material of the present invention, it is instructive to outline the preferred use of the ceramic composite as a penetration blocking armor for high speed steel, tungsten and similar types of penetrators. Think

 It is well known that the use of excessive heavy armor on military combat vehicles as described above is undesirable as it reduces vehicle performance. When using a ceramic composite of AlN and SiC, the composite is not only lighter than steel or silicon carbide, but also cheaper if it counters the same ballistic threat. That has already been confirmed. Also, the ceramic composites of AlN and SiC used as armor show considerable toughness during the impacted impact resulting in large debris and lumps after impact. The toughness of the ceramic composite of the present invention is shown, and its ballistic resistance is constant at all tilt angles, that is, armored by a weapon that collides with the armor surface at an angle of 90 ° or less than 90 °. The same penetration resistance occurs when is impacted. It is well known that other ceramic armor such as boron carbide causes different fractures with varying tilt angles.

 It is also believed that the chemical definitions of the terms "solution", "phase" and "residual" are useful in understanding the present invention.

 "Solution" is defined as "a single homogeneous liquid phase, solid phase or gas phase which is a mixture", and its constituents "liquid, gas, solid or a combination thereof" are homogeneous in the mixture. It is distributed.

 “Phase” is defined as “a part of a physical system (liquid, gas, solid) that has a clear boundary and can be physically separated from other phases and that is homogeneous overall”.

 “Residue” refers to the mineral deposits formed by chemical enrichment of the residue left in place.

 One system (A) provides better performance than the other system (B) if both are designed to prevent the penetration of certain bullets under the same impact conditions. The minimum weight of the system (A) is smaller than the minimum weight of the system (B), or when both systems have the same weight, the system (A) is more severe than the system (B) under severe shock conditions It means that the penetration of a given bullet can be prevented.

 As mentioned above, single-use silicon carbide coated armor systems are expensive and lack the ability to be hit multiple times.

 The ceramic composite of the present invention is formed from a powder mixture of SiC and 1-99% AlN. It has already been confirmed that the grain size of the composites is as fine as 1% or more, and that only 1% AlN is sufficient to modify the microstructure. It has also been previously confirmed that 75-95% SiC produces higher fracture toughness. These powders are mixed before shaping and sintering or hot pressing. The firing temperature is selected according to the desired microstructure. In order to obtain a type 1 microstructure, a mixture of AlN and SiC, firing is performed in the range of 1600-1800 ° C.

In order to obtain the fine structure of types 2 and 3 having a solid solution matrix of AlN and SiC, the firing temperature is in the range of about 1800 to 2300 ° C. At this elevated temperature, a significant amount of the powder reacts to form a solid solution matrix clustered around the unreacted particles.

 The above ceramic composites of the present invention are intended to solve the problems of the prior art silicon carbide armor systems discussed above. As a result of a ballistic resistance test, it was found that AlN has a ballistic resistance performance that is about 2/3 that of SiC. However, it is planned that the price of AlN will be reduced to about half of the price of SiC in the near future due to the large market potential in electronic device applications.

Adding AlN to SiC reduces the final price in two ways. First, the inclusion of this low cost powder reduces the price of the final product. Secondly, the treatment temperature can be remarkably lowered by the inclusion of AlN as compared with the case of SiC not containing AlN. Type 1 microstructured AlN / SiC composite parts containing 38% volume percent SiC are hot-pressed at 1650 ° C compared to 1950 ° C typically required without AlN. . This reduction in temperature significantly extends the life of the hot pressing graphite tool, which in turn reduces the cost of the final part.

 Regarding the performance of multiple hits, AlN shows higher toughness in a ballistic resistance test compared to unmixed SiC. This is due to the very rough rubble of AlN after impact (compared to that of SiC) and the constant performance of AlN over a range of angles of attack of the projectiles. Proven. Other high performance ceramics, such as boron carbide (B4C) and pure SiC, have reduced ballistic resistance when impacted by bullets at angles of less than 90 ° to the ceramic surface.

This reduction in performance is due to the large fracture and the resulting reduction in shear performance of brittle ceramics. The high toughness of AlN eliminates this performance degradation. Of the ceramic composites proposed by the present invention, the type 2 and 3 solid solution matrices exhibit a toughness intermediate between AlN and SiC. The unreacted particles remaining in the matrix add additional toughness to the composite due to the crack deflestion me shanisms common to other particulate ceramic composite materials. The same crack deflection mechanism also gives Type 1 microstructures greater toughness than pure SiC. The ceramic composite proposed by the present invention has sufficiently high ballistic resistance as a lightweight armor system. That is, the problem of toughness, which is limited in the ability to be hit many times, is substantially reduced or eliminated, and the price is low enough to justify application to armor.

The appropriate ceramic composite composition and microstructure type can be selected based on the armor system's ballistic capability, multi-shot capability and cost requirements. For example, to obtain the lowest possible price, a high AlN percentage composite would be processed to form a Type 1 microstructure. In order to meet the demand for high ballistic resistance, it is necessary to construct a structure with a high SiC content having a type 2 and type 3 microstructure. The Type 3 configuration is used for even greater toughness and multiple hit performance. When used as armor, the ceramic composites of the present invention are preferably formed of AlN containing 1-99% silicon carbide. Aluminum nitride and silicon carbide are received in 0.5 to 5 micron powder, placed in a mold, and hot compacted or sintered together at about 140.6 kg / cm ² (2000 psi) at about 1700 ° C. for 4 to 6 hours. Aluminum nitride and silicon carbide form a solid solution, which on cooling forms into a hard tile and bonds to the vehicle surface to be protected. Compared with silicon carbide alone, the blocking effect of aluminum nitride bullets for armor penetration is about 2/3 that of silicon carbide. However, at present, the price is about 1/3 that of silicon carbide. Silicon carbide, which is hot-compressed with aluminum nitride, increases the bullet erosion of the composite, thereby improving the armor effect.

 The main application of the ceramic composite of the present invention is armor for military vehicles that disables armor penetration, but it does not include cutting tools, wear parts, nozzles, electronic components, and high temperature components. ), And many other applications subject to high impact forces and / or wear.

 From the above description, it is clear that the ceramic composite of the present invention is formed from a selected percentage of silicon carbide and aluminum nitride that react in the process for forming the ceramic composite.

The microstructure of the solid solution is processed and formed at a higher temperature than the microstructure of the individual AlN and SiC phases to be mixed.

 Although the best method expected for carrying out the present invention has been shown here, it is obvious that many modifications and variations can be made within the scope of the present invention.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] Flat 2.8.21

[Claims]

Claims (22)

[Claims] 1. Mixing powdered silicon carbide and aluminum nitride, and heating and pressing the powders together at about 140.6 kg / cm ² (2000 psi) to form a solid solution ceramic composite. A method for producing a ceramic composite, comprising: 2. The method for producing a ceramic composite according to claim 1, wherein the powders are pressed together for about 4 to 6 hours while being kept at about 1700 ° C. 3. Both powders in said powder form are about 0.5-.
The method for producing a ceramic composite according to claim 1, which is a powder of 5 microns. 4. The method for producing a ceramic composite according to claim 1, wherein the percentage of silicon carbide powder in aluminum nitride is 1 to 99%. 5. Both powders are about 0.5-5 micron powder and pressed together for about 4-6 hours with the powders kept at 1700 ° C. to form the solid solution ceramic composite. The method for producing a ceramic composite according to claim 1, wherein 6. The method for producing a ceramic composite according to claim 1, wherein the percentage of silicon carbide powder in aluminum nitride is 1 to 99%. 7. The method for producing a ceramic composite according to claim 1, wherein the percentage of silicon carbide powder in aluminum nitride is about 75 to 95%. 8. A step of mixing powder-form silicon carbide and aluminum nitride, and sintering the mixed powder to intimately bond the silicon carbide and aluminum nitride to each other in a solid solution ceramic composite. A method for producing a ceramic composite, which comprises: 9. The method for producing a ceramic composite according to claim 8, wherein the powder is a powder of about 0.5 to 5 microns. 10. The method for producing a ceramic composite according to claim 8, wherein the percentage of the silicon carbide powder in the aluminum nitride powder is about 1 to 99%. 11. The method for producing a ceramic composite according to claim 8, wherein the mixed powder is pressed at a high pressure. 12. The method for producing a ceramic composite according to claim 8, wherein the percentage of the silicon carbide powder in the aluminum nitride powder is about 75 to 95%. 13. A method of manufacturing a ceramic composite armor, wherein in the step of mixing silicon carbide powder and aluminum nitride powder, the powder is a powder of about 0.5 to 5 microns, and the silicon carbide powder is aluminum nitride. about 4-6 hours process, at about 140.6kg / cm ² (200psi) the powder together to mix a silicon carbide powder and aluminum nitride powder is 1 to 99% of the total percentage of the medium, kept at about 2000 ° C. Forming a solid solution ceramic composite armor that is effective to divert the direction of a bullet fired at high speed by hot compression in a state of Method for manufacturing composite armor. 14. The method for producing a ceramic composite armor according to claim 13, wherein the percentage of the silicon carbide powder in the aluminum nitride powder is about 75 to 95%. 15. A mixture of silicon carbide powder and aluminum nitride powder hot pressed together at about 140.6 kg / cm ² (2000 psi), said powder having a particle size in the powder form prior to hot pressing of about A hard solid solution ceramic composite characterized in that it is 0.5 to 5 microns. 16. The powder is about 2000 ° C. in a compression process.
16. The ceramic composite according to claim 15, wherein the pressure is applied for about 4 to 6 hours while being kept at the temperature. 17. The ceramic composite according to claim 16, wherein the percentage of the silicon carbide powder in aluminum nitride is 1 to 99%. 18. When the ceramic composite material is used as armor, the percentage of silicon carbide powder is reduced to a minimum within the range to allow penetration by bullets of various sizes expected to be directed at the armor. 18. The ceramic composite of claim 17, characterized in that at the same time as blocking, the weight of the armor is minimized. 19. The ceramic composite according to claim 15, wherein the composite is a type 1 composite. 20. The ceramic composite of claim 15, wherein the composite is a type 2 composite. 21. The ceramic composite according to claim 15, wherein the composite is a type 3 composite. 22. The ceramic composite according to claim 15, wherein the percentage of the silicon carbide powder in the aluminum nitride powder is about 75-95%.