Stock material or miscellaneous articles – Self-sustaining carbon mass or layer with impregnant or...
Patent
1995-06-26
1997-06-03
Raimund, Christopher
Stock material or miscellaneous articles
Self-sustaining carbon mass or layer with impregnant or...
427373, 4273855, 442179, B32B 900
Patent
active
056353006
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the field of structural materials operable under heavy thermal loading and in oxidizing media and can be useful in chemical, petroleum, metallurgy, and aircraft industries, to produce articles and structural elements able to withstand aggressive media, such as linings of chambers for neutralizing ecologically unsafe substances, nozzles, crucibles, parts of high-temperature turbines subject to heavy mechanical loads under service conditions.
DESCRIPTION OF PRIOR ART
There are known in the art various processes for producing materials reinforced by carbon fibers and oxidation protected to prevent rapid damage under service conditions of the material carbon-carbon basis which carries all the mechanical loads. Generally, the oxidation protection of such materials is attained via forming a heat-resistant silicon carbide layer on the surface thereof.
Known in the art is a process for producing composite articles, wherein first of all a carbon-plastic preform is prepared on the basis whereof a coke matrix is formed by heating the preform up to 1000.degree. C. The resulting composite is twice densified via pitch impregnation, the latter being carbonized.
To form a surface protective SiC layer, the resulting carbonized preform is heat treated in a filling consisting of silicon carbide and silicon, thereby forming a SiC surface layer about 400 .mu.m thick (JP, A, 2-91270).
The article material protection (as a separate process) in the form of a surface SiC layer having CTE different from that of the carbon-carbon basis, causes the SiC layer cracking under cooling, and, accordingly, rapid damage of the basis under service conditions in view of an oxidizer penetration thereto through the cracks.
Furthermore, the carbon-carbon basis low modulus of elasticity makes it impossible to use articles made of such a material in structures requiring a high rigidity.
Also known in the art is a process for producing composite articles, wherein onto a premolded fibrous preform in the form of wool, yarn, etc. (for example a plate of 200.times.100.times.25 mm) pyrolytic carbon is CVD deposited, and a protective SiC coating is then formed by immersing the fibrous preform into a silicon melt (U.S. Pat. No. 4,397,901). In this case a portion of the pyrolytic carbon is converted into silicon carbide on the article fibers.
The pyrolytic carbon deposition directly onto the fibers, without the step of forming a carbon-plastic preform and on its basis a coke matrix, results in a preform having low strength properties (brittle), insofar as the carbon fibers appear not to be bonded with the matrix, are in a movable state, and do not take over the loads.
Moreover, when using this process, a large amount of free silicon remains in the matrix which decreases the article operating temperature level and increases the residual stresses in the material (in view of silicon expansion under cooling), which decreases its strength as well. Siliconizing in a silicon melt not only causes ecologically unsafe evaporations, but also requires rather expensive equipment, and in case of large-size articles the problems are getting still more serious.
Further known in the art is a process for producing a structural material, wherein a carbon-plastic preform reinforced by carbon fibers is obtained, and a pyrolytic carbon coating is used, however the latter is applied directly onto the fibers prior to the matrix formation. The resulting fibrous basis is then subjected to multiple densifications with a thermosetting binder modified with fine-dispersed SiC additives for SiC-forming components. Upon carbonization followed by heat treatment a material is obtained in the coke matrix whereof separate SiC inclusions are present (FR, B, 2,635,773).
Using a separate process, by treating in a filling containing silicon and silicon carbide with an alumina additive, a protective SiC layer is formed on the article surface. Then, in view of the SiC layer cracking under cooling, onto the 1.sup.st SiC layer surface is CVD
REFERENCES:
patent: 4397901 (1983-08-01), Warren
patent: 4540674 (1985-09-01), Watanabe et al.
patent: 5051300 (1991-09-01), Rousseau
Demin Alexander V.
Kolesnikov Sergey A.
Konokotin Vasily V.
Kostikov Valery I.
Ponkratova Raisa N.
Aerospatiale - Societe Nationale Industrielle
NII Grafit Research Institute
Raimund Christopher
LandOfFree
Process for producing articles of carbon-silicon carbide composi does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing articles of carbon-silicon carbide composi, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing articles of carbon-silicon carbide composi will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-390160