RU2397969C1 - Ceramic composite material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to ceramic composite materials and can be used in aviation engineering and mechanical engineering when making heat-loaded components of gas turbine installations and engines for gas-, oil-pumping, power and transportation systems etc, used in periodic heating conditions at 1400°C. The invention discloses a ceramic composite material which contains carbon fibre and a matrix which includes silicon, carbon, silicon tetraboride, silicon carbide and additionally contains silicon dioxide, boron carbide and boric anhydride, with the following ratio of components of the matrix in wt %: Si 20-30, C 25-35, SiB₄ 1.6-1.8, SiO₂ 4-5, B₄C 1-3, B₂O₃ 0.5-2, SiC - the rest.

EFFECT: higher thermal stability and heat resistance of the ceramic composite material at operating temperature of 1400°C and retention of said properties for a long period of time (over 100 hours), which increases reliability and service life of the article.

1 ex, 2 tbl

Description

The invention relates to ceramic composite materials and can be used in aeronautical engineering and mechanical engineering in the manufacture of heat-loaded parts of gas turbine units and engines of gas, oil pumping, energy and transport systems, etc., operated under conditions of cyclic heating at a temperature of 1400 ° C.

Known ceramic composite material containing carbon fibers and a matrix consisting of silicon carbide, boron and pyrocarbon distributed in its volume and on the surface of the material, in the following ratio of components in the matrix, wt.%:

SiC 10-50 AT 0.5-1.2 C (pyrocarbon) rest

(RF patent No. 2203218).

Ceramic composite material can be used in the manufacture of products, for example, sealing rings operating in aggressive environments, in air at a temperature of 900 ° C.

Also known is a ceramic composite material of the following chemical composition, wt.%:

Carbon fiber fifty Glass matrix fifty

in the following ratio of glass matrix components, wt.%:

SiO ₂ 81 B ₂ O ₃ 13 Al ₂ O ₃ 2 Na ₂ O four

(US patent No. 4511663).

Known ceramic composite material can be used for the manufacture of heat-loaded parts used in aircraft and mechanical engineering.

The disadvantages of these materials include low heat resistance (resistance to cyclic heating) and heat resistance at a temperature of 1400 ° C.

The closest analogue taken for the prototype is a ceramic composite material containing carbon fibers and a matrix including silicon, carbon, silicon tetraboride, silicon carbide, in the following ratio of matrix components, wt.%:

Si 20-35 C 25-40 SiB ₄ 2-6 SiC rest

(RF patent No. 2297992).

The disadvantages of the ceramic composite material of the prototype are insufficient heat resistance and heat resistance (loss of mass) during prolonged use of the material at a temperature of 1400 ° C.

It should be noted that in an oxidizing environment, a change (by 50-100 ° С) of the working temperature of ceramic composite materials, the matrix of which contains boron-containing components, has a significant effect on the oxidation process and the amount of borosilicate glass bond formed, which leads to a change in the operational characteristics of the material in the process long operation.

An object of the invention is to increase the heat resistance and heat resistance of the ceramic composite material at an operating temperature of 1400 ° for a long time (over 100 hours).

The stated technical problem is achieved by the fact that the proposed ceramic composite material containing carbon fibers and a matrix including silicon, carbon, silicon tetraboride, silicon carbide, which additionally contains silicon dioxide, boron carbide and boric anhydride, in the following ratio of matrix components, wt.% :

Si 20-30 FROM 25-35 SiB ₄ 1.6-1.8 SiO ₂ 4-5 At _{4 s} 1-3 B ₂ O ₃ 0.5-2 SiC rest

The authors found that the additional introduction into the matrix of silicon dioxide, boron carbide, boric anhydride at the stated ratio and content of components leads to the formation at 1400 ° C in an oxidizing medium of a sufficient amount of viscous protective borosilicate glass-bond, which has the ability to relax thermoelastic stresses and prevents the diffusion of oxygen into the volume material, which increases its heat resistance and heat resistance.

Examples of implementation

To obtain a ceramic composite material, the compositions of the proposed material (1-3) and the prototype material (4) were prepared, the ratio of the components in which are shown in table 1.

Dispersed particles of a matrix of silicon carbide, silicon, carbon (SiC, Si, C) were mixed with particles of silicon tetraboride (SiB ₄ ) and boron carbide (B ₄ C) and carbon fibers in polyethylene drums.

The carbon fiber UKNP-5000 was used as the carbon fiber material.

The resulting mixture was poured into the mold and pressed at a temperature of 120-150 ° C. Then, the billet was subjected to high temperature heat treatment in a vacuum oven at a temperature of 1400-1450 ° C.

After heat treatment in vacuum, the samples were impregnated with sol in a SiO ₂ –B ₂ O _{3 system} with intermediate drying in air for 24 h.

The properties of the proposed ceramic composite material and the material of the prototype are shown in table 2.

Analysis of the obtained results indicates that the heat resistance of the proposed ceramic composite material is ~ 2.5 times higher than that of the prototype material. The weight gain of the material during heat resistance tests confirms the formation of a protective borosilicate glass bond. The heat resistance of the proposed ceramic composite material, in wt.%: 100 h - 1.8 ÷ 2.1; 200 h - 2.2 ÷ 2.7; 300 h - 2.8 ÷ 2.9; 400 h - 3.2 ÷ 3.5, at the same time, the prototype material exhibits mass loss and destruction after 100 h of testing at 1400 ° C due to oxidation of the carbon filler.

Thus, the use of the proposed ceramic composite material with increased heat resistance and heat resistance in the manufacture of heat-loaded parts of gas turbine units and engines of gas, oil pumping, energy and transport systems, etc., operated for a long time under conditions of cyclic heating at a temperature of 1400 ° C, improves reliability and resource products.

Table 1 Name of components The composition according to examples, wt.% one 2 3 4 prototype Matrix: Si twenty 25 thirty thirty C 35 thirty 25 thirty SiB ₄ 1.8 1.7 1,6 four SiO ₂ 5 4,5 four - B ₄ C 3 2 one - B ₂ O ₃ 2 1,5 0.5 - SiC rest rest rest rest

table 2 No. p / p Properties Suggested formulations Prototype one 2 3 four one. Heat resistance, central heating station, 1400 ° С↔20 ° С, air cooling one hundred 105 one hundred 40 2. Heat resistance, wt.%, 1400 ° С 100 h 1.8 2.1 1.9 -2.5 sample destruction 200 h 2.2 2.6 2.7 sample failure 300 h 2.9 2,8 2.9 - "- 400 h 3.3 3.2 3,5 - "-

Claims (1)

Ceramic composite material containing carbon fibers and a matrix including silicon, carbon, silicon tetraboride, silicon carbide, characterized in that the matrix additionally contains silicon dioxide, boron carbide and boric anhydride in the following ratio of matrix components, wt.%:
Si 20-30 C 25-35 SiB ₄ 1.6-1.8 SiO ₂ 4-5 B ₄ C 1-3 B ₂ O ₃ 0.5-2 SiC rest