ARMOR PLATING MADE OF FINE-GRAIN BORON CARBIDE AND SILICON CARBIDE

Abstract

An antiballistic armor-plating component, includes a ceramic body made of a material comprising, as percentages by volume, between 35% and 55% of silicon carbide, between 20% and 50% of boron carbide, between 15% and 35% of a metallic silicon phase or of a metallic phase including silicon.

Claims

1. An antiballistic armor-plating component, comprising a ceramic body made of a material comprising, as percentages by volume: between 35% and 55% of silicon carbide, between 20% and 50% of boron carbide, between 15% and 35% of a metallic silicon phase or of a metallic phase comprising silicon, and wherein, as percentages by volume of said material: the boron carbide grains with an equivalent diameter greater than 30 micrometers represent less than 5%, preferably less than 2%, the boron carbide grains with an equivalent diameter less than 5 micrometers represent more than 15% and less than 35%, the silicon carbide grains with an equivalent diameter greater than 30 micrometers represent less than 5%, preferably less than 1%, and the silicon carbide grains with an equivalent diameter greater than or equal to 5 micrometers and less than or equal to 30 micrometers represent between 35% and 55%.

2. The 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 armor-plating component as claimed in claim 1, wherein the silicon carbide grains with an equivalent diameter greater than or equal to 5 micrometers and less than 30 micrometers represent more than 40% by volume of said material.

4. The armor-plating component as claimed in claim 1, wherein the boron carbide grains with an equivalent diameter less than 5 micrometers represent between 20% and 30% by volume of said material.

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

6. The armor-plating component as claimed in claim 1, wherein the boron carbide grains with an equivalent diameter between 5 and 30 micrometers, limits included, represent less than 10% by volume of said material.

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

8. The armor-plating component as claimed in claim 1, wherein the free carbon content is less than 1% by volume of said material.

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

10. The armor-plating component as claimed in claim 1, wherein the silicon carbide grains with an equivalent diameter greater than or equal to 5 micrometers are in alpha (a)crystallographic form.

11. The armor-plating component as claimed in claim 1, wherein the proportion by volume of B.sub.4C represents less than 20% of the boron carbide content of said material.

12. The armor-plating component as claimed in claim 1, wherein the boron carbide is present in the form of a B.sub.12(B,C,Si).sub.3 phase.

13. The 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.

14. The armor-plating component as claimed in claim 1, wherein, by volume of said material: the silicon carbide content of said material is greater than 35% and less than 55%, the boron carbide content is greater than 20% and less than 50%, the content of metallic silicon or of the metallic phase comprising silicon is greater than 15% and less than 35%, the boron carbide grains with an equivalent diameter greater than 30 micrometers represent less than 5%, the boron carbide grains with an equivalent diameter less than 5 micrometers represent more than 15% and less than 35%, the silicon carbide grains with an equivalent diameter greater than or equal to 5 micrometers and less than or equal to 30 micrometers represent between 35% and 55%, the silicon carbide grains with an equivalent diameter greater than 30 micrometers represent less than 5%, more than 90% of the grains, by volume of said material, have an equivalent diameter less than 30 micrometers, more than 80% of grains with an equivalent diameter less than 5 micrometers are boron carbide grains, more than 80% of grains with an equivalent diameter greater than or equal to 5 micrometers are silicon carbide (SiC) grains.

15. The 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.

16. The 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.

17. The armor-plating component as claimed in claim 1, comprising a ceramic body made of a material, provided on an inner face thereof 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, metals or alloys thereof or steel.

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

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

20. A process for manufacturing the ceramic body of the armor-plating component as claimed in claim 1, the process comprising: a) preparing a starting feedstock including: at least one powder of boron carbide particles, of which the median diameter of the particles is between 0.1 and 10 micrometers, a powder of silicon carbide particles, of which the median diameter of particles is between 5 and 30 micrometers, a carbon precursor of which the median diameter is less than 1 micrometer, an aqueous solvent, optionally shaping additives, b) shaping the starting feedstock into the form of a preform; c) removal from the mold after setting or drying; d) optionally, drying the preform, until a residual moisture content is comprised between 0 and 0.5% by weight; 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.

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

Description

EXAMPLES

[0120] 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.

[0121] In all the examples which follow, ceramic parts in the form of plates having a 100 m×100 mm format with a thickness of 7 to 10 mm were initially produced by pressing a mixture, the formulations of the various examples of which have been reported in table 1 below. In the examples 1 according to the invention and the comparative examples 1 and 2, the boron carbide and silicon carbide powders were mixed beforehand with a PVA/PEG binder and the graphite powder so as to obtain granules after atomization according to techniques well known to those skilled in the art. The granules obtained after atomization which have a moisture content of less than 1% were shaped by uniaxial pressing at a pressure of 70 MPa, the parts were removed from the mold and then dried for 24 h at 110° C.

[0122] For comparative example 3, the mixture was prepared in the form of a slip cast in a plaster mold. After casting and hardening of the paste, the parts were removed from the mold and then dried for 24 h at 110° C.

[0123] 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.

TABLE-US-00001 TABLE 1 invention comparative comparative comparative exampie 1 example 1 example 2 example 3 Composition of the initial mixture (% by weight) SiC powder 0 0 0 45 D.sub.50 = 80 μm D.sub.10 = 53 μm D.sub.90 = 120 μm SIC powder 45.5 45.5 0 0 D.sub.50 = 11 μm D.sub.10 = 2 μm D.sub.90 = 15 μm SiC powder 0 0 45.5 50 0.1-5 μm D.sub.50 = 2.5 μm D.sub.10 = 0.5 μm D.sub.90 = 7 μm B4C powder 0 30.5 0 0 D.sub.50 = 5 um D.sub.10 = 2 μm D.sub.90 = 9 μm B4C powder 45.5 15 45.5 0 D.sub.50 = 1.5 μm D.sub.10 = 0.5 μm D.sub.90 = 5 μm Graphite powder 9 9 9 5 D.sub.50 ~ /um D.sub.10 - 0.4 μm D.sub.90 “1.0 um total minerals % 100 100 100 100 % added water +50% (before granulation) +18% relative to the mass of minerals Added binder + +2.5 % (before granulation) +0.5% dispersant

[0124] For each embodiment, the properties of the ceramic body and the composition of the various constituent materials thereof are collated in table 2.

TABLE-US-00002 TABLE 2 invention comparative comparative comparative example 1 example 1 example 2 example 3 Body/ceramic material characteristics after firing Microstructural characteristics (vol % of the product excluding porosity) Fraction of boron carbide grains* <1 <1 <1 <1 >30 μm i Fraction of silicon carbide grains* <1 <1 <1 29 >30 μm Fraction of boron carbide grains* <1 8 <5 <1 ≥5 μm and $30 μm Fraction of silicon carbide grains* 45 40 5 20 ≥5 μm and $30 μm Fraction of boron carbide grains* 25 15 22 <1 <5 μm Fraction of SIC grains* 5 8 42 39 <5 μm Volume fraction metallic matrix remainder remainder remainder remainder Porosity % <1 <1 <1 <1 Bulk density g/cm.sup.3 2.76 2.74 2.74 3.10 X-ray diffraction analysis (vol %) Silicon carbide SIC (α and 50 48 48 88 β forms) Boron carbide phase, 24 7.5 24 ND** B.sub.12(B,C,Si).sub.3 I Boron carbide phase, ND** 14.5 ND*’ ND** B.sub.4C Metallic Si 25 30 27 12 Free carbon <1 <1 <1 <1 *equivalent diameter of grains **not detectable

[0125] 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 m×200 m×5 mm.

The surface density ρ.sub.at is calculated according to the following formula ρ.sub.at=t×ρ.sub.v where: [0126] ρ.sub.at the surface density expressed is kg/m.sup.2 [0127] t is the thickness of the plate, expressed in mm, [0128] ρ.sub.v is the bulk density expressed in kg/dm.sup.3 typically measured according to ISO 18754.

[0129] 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 was produced 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 below:

TABLE-US-00003 TABLE 3 invention comparative comparative comparative example 1 example 1 example 2 example 3 Ballistic tests Median velocity 820 790 795 760 V.sub.50 (m/s) for a surface density of 22.5 kg/dm.sup.2

[0130] The results grouped together in table 3 indicate that the choice of material 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 is in accordance with the present invention, leads to improved antiballistic performance (higher velocity V.sub.50, at equal surface density).