BORON CARBIDE AND SILICON CARBIDE ARMOUR

Abstract

An antiballistic armor-plating component, includes a ceramic body made of a material including, as percentages by volume, between 20% and 75% of boron carbide, between 5% an d 30% of a metallic silicon phase or of a metallic phase including silicon and between 20% and 70% of silicon carbide and wherein, as percentages by volume: more than 60% of the grains with an equivalent diameter greater than 60 micrometers are boron carbide grains, the boron carbide grains with an equivalent diameter greater than 30 micrometers represent more than 20%, the silicon carbide grains with an equivalent diameter greater than or equal to 10 micrometers represent more than 10%, the silicon carbide grains with an equivalent diameter less than 10 micrometers represent more than 10%.

Claims

1. An antiballistic armor-plating component, comprising a ceramic body made of a material comprising, as percentages by volume: between 20% and 75% of boron carbide, between 5% and 30% of a metallic silicon phase or of a metallic phase comprising silicon, between 20% and 70% of silicon carbide, and wherein, as percentages by volume: more than 60% of the grains with an equivalent diameter greater than 60 micrometers are boron carbide grains, the boron carbide grains with an equivalent diameter greater than 30 micrometers represent more than 20%, the silicon carbide grains with an equivalent diameter greater than or equal to 10 micrometers represent more than 10%, and the silicon carbide grains with an equivalent diameter less than 10 micrometers represent more than 10%.

2. The antiballistic armor-plating component as claimed in claim 1, wherein said ceramic body is monolithic and has an impact area greater than 100 cm.sup.2, a thickness greater than 3 mm and a bulk density less than 3.0 g/cm.sup.3.

3. The antiballistic armor-plating component as claimed in claim 1, wherein the silicon carbide grains with an equivalent diameter greater than or equal to 10 micrometers and less than 60 micrometers represent more than 10% by volume of said material.

4. The antiballistic armor-plating component as claimed in claim 1, wherein the silicon carbide grains with an equivalent diameter less than 10 micrometers represent less than 55% by volume of said material.

5. The antiballistic armor-plating component as claimed in claim 1, wherein the silicon carbide grains with an equivalent diameter greater than or equal to 60 micrometers represent less than 10% by volume of said material.

6. The antiballistic armor-plating component as claimed in claim 1, comprising: boron carbide grains, a matrix binding said boron carbide grains, said matrix comprising at least a) a metallic silicon phase or a metallic phase comprising silicon and b) silicon carbide grains.

7. The antiballistic armor-plating component as claimed in claim 1, wherein the boron carbide grains with an equivalent diameter less than or equal to 5 micrometers represent less than 10% by volume of said material.

8. The antiballistic armor-plating component as claimed in claim 1, wherein the silicon carbide grains with an equivalent diameter less than 5 micrometers, in alpha (a)crystallographic form, represent at least 20% by volume of said material.

9. The antiballistic armor-plating component as claimed in claim 1, wherein the boron carbide grains with an equivalent diameter greater than 60 micrometers represent more than 15% and/or less than 40% by volume of said material.

10. The antiballistic armor-plating component as claimed in claim 1, wherein the silicon carbide content of said material is greater than 30% and/or less than 65% by volume of said material.

11. The antiballistic armor-plating component as claimed in claim 1, wherein the boron carbide content is greater than 25% and/or less than 60% by volume of said material.

12. The antiballistic armor-plating component as claimed in claim 1, wherein the boron carbide, the silicon carbide and the metallic silicon or the metallic phase comprising silicon together represent more than 75%, by volume, of said material.

13. The antiballistic armor-plating component as claimed in claim 1, wherein, by volume of said material: the silicon carbide content of said material is greater than 30% and less than 70%, and the boron carbide content is greater than 20% and less than 50%, and the content of metallic silicon or of the metallic phase comprising silicon is greater than 8% and less than 25%, and the boron carbide grains with an equivalent diameter greater than 30 micrometers represent more than 20% and less than 50%, and the silicon carbide grains with an equivalent diameter between 10 micrometers and 60 micrometers represent more than 10% and less than 20%, and the silicon carbide grains with an equivalent diameter less than 10 micrometers represent more than 25% and less than 60%, and the silicon carbide grains with an equivalent diameter less than 5 micrometers represent less than 5%, the boron carbide grains with an equivalent diameter greater than 60 micrometers represent more than 15% and less than 30%, and more than 80% of the grains with an equivalent diameter greater than 60 micrometers are boron carbide grains.

14. The antiballistic armor-plating component as claimed in claim 1, wherein the ceramic body has a mass-to-area ratio, or surface density, measured in kg/m.sup.2, of less than 100.

15. The antiballistic armor-plating component as claimed in claim 1, wherein the ceramic body is chosen from a plate, a chest protector, a helmet, a bodywork element of a vehicle, a tube.

16. The antiballistic armor-plating component as claimed in claim 1, comprising a ceramic body made of a material, provided on its inner face or face opposite the impact face with an energy-dissipating back coating, made of a material of lower hardness than that of the material constituting the ceramic body, wherein the material constituting the back coating is chosen from polyethylenes PE, glass or carbon fibers, aramids, or metals.

17. The antiballistic armor-plating component as claimed in claim 16, wherein the ceramic body-back coating assembly is surrounded by an envelope of a confining material.

18. The antiballistic armor-plating component as claimed in claim 17, wherein the material constituting the envelope is chosen from polyethylenes PE, glass or carbon fibers, aramids, or metals.

19. A process for manufacturing the ceramic body of the armor-plating component as claimed in claim 1 comprising: a) preparing a starting feedstock including: at least one powder of boron carbide particles, of which a median diameter of the particles is between 30 micrometers and 150 micrometers, a first powder of silicon carbide particles, of which a median diameter of the first powder of particles is at least 1.5 times smaller than the median diameter of boron carbide grains, a second powder of silicon carbide particles, of which a median diameter is at least 5 times smaller than the median diameter of the first powder of silicon carbide particles, an aqueous solvent, optionally, a carbon precursor, optionally, shaping additives, b) shaping the starting feedstock into the form of a preform; c) removal from a mold after setting or drying; d) optionally, drying the preform; e) loading the preform, in contact with a source of silicon or a silicon alloy into a furnace; f) firing the preform under an inert atmosphere or under vacuum, so as to infiltrate the preform with the source of molten silicon and consolidate it.

20. A method comprising providing an antiballistic protection for a person or for a land, sea or air vehicle or for a fixed installation with the antiballistic armor-plating component as claimed in claim 1.

Description

EXAMPLES

[0126] The following examples are given purely by way of illustration and do not limit, under any of the described aspects, the scope of the present invention.

[0127] In all the examples which follow, ceramic parts in the form of plates having a 100 mm×100 mm format with a thickness of 7 to 10 mm were initially produced by casting, in a plaster mold, a suspension according to the process described above and the formulations described in table 1 below. After casting and hardening of the paste, the parts were removed from the mold and then dried for 24 h at 110° C. The parts were then introduced into a furnace for firing at 1700° C. under vacuum, at a pressure below 20 torr. The silicon was introduced from a powder placed in contact with the green parts during furnace charging. The amount of silicon representing about 45% of the dry green. mass of the parts. Representative comparative example 6 was according to the teaching of example 1 of U.S. Pat. No. 6,862,970B2. The firing for this example was carried out at 1550° C. in contrast to the other examples.

[0128] For each embodiment, the properties of the ceramic body and the composition of the various constituent materials thereof are collated in table 2.

[0129] For each example, eight ceramic plates obtained according to the process described above having a surface density of 22.5 kg/m.sup.2 (±0.5 kg/m.sup.2) were adhesively bonded to metal plates of 7020 T6 aluminum of 200 mm×200 mm×5 mm.

[0130] The surface density ρat is calculated according to the following formula ρat=t×ρv where: [0131] ρat is the surface density expressed in kg/m.sup.2 [0132] t is the thickness of the plate, expressed in mm [0133] ρv is the bulk density expressed in kg/dm.sup.3 typically measured according to ISO 18754.

[0134] Each ceramic-metal assembly was shot from a distance of 15 meters with a 7.62×51 P80 (steel core) ammunition at various speeds. A graph representing the degree of impact or perforation (total protection at complete perforation) as a function of the impact speed for all the examples. From this graph, it is determined for each example the median velocity V50 starting from which the probability of perforation is 50%. A velocity greater than 700 m/s, taking into account this type of ammunition, is considered satisfactory. A high velocity corresponds to a ballistic performance which is inversely proportional to the surface density. The ballistic properties of the final armor plate are collated in table 3.

[0135] The results are given in the following tables:

TABLE-US-00001 TABLE 1 invention invention invention comparative comparative comparative comparative cornparative comparative example example example example example example example example example 1 2 3 1 2 3 4 5 6 Composition of the initial mixture (% by weight) B4C powder 41 30 41 25 30 70 0 0 46.3 D.sub.50 = 70 μm D.sub.10 = 47 μm D.sub.90 = 105 μm B4C powder 0 0 0 0 0 0 30 0 0 D.sub.50 = 5 μm SiC powder 0 0 0 0 15 0 15 45 0 D.sub.50 = 80 μm D.sub.10 = 53 μm D.sub.90 = 120 μm SiC powder 15 15 30 20 0 27 0 0 0 D.sub.50 = 27 μm D.sub.10 = 18 μm D.sub.90 = 40 μm SiC powder 0 0 0 0 0 0 0 0 46.3 D.sub.50 = 13 μm D.sub.10 = 8.5 μm D.sub.90 = 17.5 μm SiC powder 41 50 26 50 50 0 55 50 0 0.1-5 μm D.sub.50 = 2.5 μm D.sub.10 = 0.5 μm D.sub.90 = 7 μm % added 0 0 0 0 0 0 0 0 7.4 carbon (fructose) Graphite 3 5 3 5 5 3 0 5 0 powder D.sub.50 = 0.7 μm D.sub.10 = 0.4 μm D.sub.90 = 1.0 μm total 100 100 100 100 100 100 100 100 100 minerals % % added 18 18 18 18 18 18 18 18 26 water relative to the mass of minerals Added 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 binder + dispersant

TABLE-US-00002 TABLE 2 Inv. Inv. Inv. Comp. Comp. Comp. Comp. Comp. Comp. example example example example example example example example example 1 2 3 1 2 3 4 5 6 Body/ceramic material characteristics after firing Microstructural characteristics (vol % of the product excluding porosity) Fraction of boron 35 28 34 24 39 52 <1 <1 43 carbide grains* ≥30 μm Fraction of boron <1 <1 <1 <1 <1 <1 19 <1 <1 carbide grains* <5 μm Fraction of boron 23 19 22 15 26 35 0 0 28 carbide grains* ≥60 μm Percentage by 99 99 99 99 72 99 0 0 99 volume of boron carbide grains among the grains ≥60 μm Fraction of <1 <1 <1 <1 10 <1 8 35 <1 silicon carbide grains* ≥60 μm Fraction of 13 14 25 19 <1 13 2 7 28 silicon carbide grains* ≥10 μm and <60 μm Fraction of 35 47 21 47 40 10 36 46 9 silicon carbide grains* <10 μm Fraction of a SiC 30 40 18 40 34 <1 31 39 <1 grains* <5 μm Porosity % <1 <1 <1 <1 <1 <1 <1 <1 <1 Bulk density 2.82 2.92 2.82 2.95 2.87 2.63 2.81 3.10 2.73 g/cm.sup.3 X-ray diffraction analysis (vol %) Silicon carbide 48 61 46 65 53 23 46 88 37 SiC (α and β) forms) Boron carbide 35 28 34 23 39 52 36 0 43 phases, in particular B.sub.4C and B.sub.12(B, C, Si).sub.3 Metallic Si 17 11 20 12 9 25 18 12 20

TABLE-US-00003 TABLE 3 Inv. Inv. Inv. Comp. Comp. Comp. Comp. Comp. Comp. example example example example example example example example example 1 2 3 1 2 3 4 5 6 Ballistic tests Median velocity 800 780 760 740 730 700 750 760 730 V.sub.50 (m/s) for a surface density of 22.5 kg/dm.sup.2

[0136] The results grouped together in table 3 indicate that the choice of materials used to manufacture an armor-plating component, i.e. of which the volume fractions of boron carbide grains, of silicon carbide grains and of the silicon-based metallic phase are in accordance with the present invention, lead to improved antiballistic performance (higher velocity V.sub.50, at equal surface density).