Plastic and nonmetallic article shaping or treating: processes – Outside of mold sintering or vitrifying of shaped inorganic... – Using organometallic or organosilicon intermediate
Reexamination Certificate
1998-09-24
2001-06-12
Derrington, James (Department: 1731)
Plastic and nonmetallic article shaping or treating: processes
Outside of mold sintering or vitrifying of shaped inorganic...
Using organometallic or organosilicon intermediate
C264S624000, C264S625000, C264S639000, C264S640000, C264S324000
Reexamination Certificate
active
06245283
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fiber bond type ceramic material, and, more particularly, to a method for the production of a ceramic material of the type having fibers three dimensionally bonded thereto, and engine parts formed of the material.
2. Description of Related Art
A Si—Ti—C—O fiber bond type ceramic material (sold under the trademark of “Tyrannohex [transliteration]”) produced by pressing surface-oxidized Si—M—C—O fibers (sold under the trademark of “Tyranno [transliteration]Fibers”) has been published (“Microstructure and Characteristics of Si—Ti—C—O Fiber-bond Type Ceramic Material,” Jul. 18, 1995, the 76th Ceramic Material Division Committee of Japan Material Society, for example) and has been the subject of patents (Japanese Patent No. 2,579,854, titled “Inorganic fiber sinter and method for production thereof”).
The Tyranno fibers (Si—M—C—O-fibers, M means metal) are inorganic fibers of Si—M—C—O synthesized by melt spinning polymetalocarbosilane, then infusibilizing the produced threads, and firing the set threads. The Tyrannohex (Si—M—C—O fiber-bond type ceramic) material is produced by heat-treating the Tyranno fibers in the air and obtaining oxidized Tyranno fibers having an oxide layer on the surface thereof, preparing unidirectional prepreg sheets from the fibers, superimposing the sheets uniformly in alignment, and compressing the superimposing sheets with a hot press machine at an elevated temperature.
In the Tyrannohex material constructed as described above, a matrix layer has been formed by hot-pressing oxided fibers and the gaps between the adjacent fibers are uniformly filled with the oxide formerly existent on the surface of the raw material fibers and consequently allowed to form a dense texture veritably destitute of pores. Further, since the Tyranno fibers themselves possess high mechanical properties and excellent heat-resistance and oxidation-resistance, the Tyrannohex material likewise excels in mechanical strength and in heat-resistance and oxidation-resistance.
Machining the Tyrannohex material to manufacture engine parts by making the best use of such characteristics of the Tyrannohex (fiber-bond type ceramic) material has been desired. When some turbine parts as, for example, rotor blades and stationary vanes, shrouds, combustors, the afterburner flaps, and split-structure liners are produced by machining the Tyrannohex material, the parts have a heightened heat-resistant strength (not lower than 1400° C.) and a decreased weight (specific gravity about 2.6) as compared with equivalent turbine parts made of the conventional heat-resistant metal (tolerable temperature about 1000° C. and specific gravity about 8).
The Tyrannohex material, however, has the problem of readily sustaining tears when it is cut in fabricating a turbine part. When a unidirectional Tyrannohex material is clamped in a vice and a cut is made in the material in a direction perpendicular to the fibers therein. For example, the complex stress originating in the friction resistance generated by the rotational of a grindstone and the rotation moment generated during the course of cutting under the weight of the grindstone possibly acts on the boundaries of the fibers and causes separation of the fibers at the interfaces.
When then the Tyranno fibers are two-dimensionally woven and they are superposed to produce a Tyrannohex material for the purpose of overcoming the problem mentioned above, the Tyrannohex material has the further problem of readily sustaining separation of superposed weaves at the interfaces when the material is subjected to machining.
Further, attempts to produce a Tyrannohex material by orthogonally weaving Tyranno fibers in such a construction as contains fibers parallel to the direction of compression for the purpose of precluding this separation, suffer from the disadvantage that the raw material fibers, during the course of hot-press fabrication, form kinks and incur a heavy loss of strength, have voids produced readily therein, and prevent formation of a dense matrix layer, with the result that the produced Tyrannohex material will have an unduly low volumetric fiber content and will exhibit serious degradation of heat-resistant strength.
SUMMARY OF THE INVENTION
This invention has been created with a view to solving the problems mentioned above. Specifically, this invention has for an object thereof the provision of a method for the production of a fiber-bond type 3 dimensionally strengthened ceramic material which does not easily peel or crack in the boundary faces or superimposed faces of fibers. Another object is that the raw material fibers suffers scant injury during the course of hot-press fabrication that there are no voids produced therein. Consequently, achievement of these objects enables these raw material fibers to form a dense matrix layer, and allows the produced ceramic material to acquire a high fiber content and allows engine parts to be made of the ceramic material.
According to the present invention, there is provided a method for the production of a fiber-bond type ceramic material, characterized by using, as raw material fibers, inorganic fibers of Si—M—C—O synthesized by melt spinning polymetalocarbosilane, then infusibilizing the produced threads, and firing the set threads, forming from the raw material fibers a woven fabric having all the fibers thereof extending perpendicularly or obliquely relative to the direction of compression during the course of a hot-press fabrication, heat-treating the woven fabric in the air thereby preparing a woven fabric of oxidized fibers provided with an oxide layer on the surface thereof, and subjecting the woven fabric of oxidized fibers to a hot-press fabrication while compressing the fabric in the direction of compression mentioned above thereby causing oxide layers on the surface to adhere fastly to each other and form a matrix.
According to the method of this invention mentioned above, since all the fibers (Tyranno fibers) that form the woven fabric are extended perpendicularly or obliquely relative to the direction of compression during the course of the hot-press fabrication, the compressing force exerted during the course of the hot-press fabrication acts in the lateral direction on the fibers. The fibers, therefore, do not easily kink or shear. Further, since the compressing force acts in the direction of contracting the distances between the fibers, the fibers produce no voids and allow formation of a dense matrix layer. The fiber-bond type ceramic material to be produced, therefore, has a high fiber volumetric content and high heat-resistant strength. The ceramic material having the fibers three-dimensionally bonded thereto does not readily peel or crack in the boundary faces or superimposed faces of the fibers because it acquires a dense texture containing very few pores between the fibers.
Engine parts which are produced by shaping the fiber-bond type ceramic material manufactured as described above do not easily peel or crack in the boundary faces or superimposed faces of the fibers.
According to a preferred embodiment of this invention, a biaxial three-dimensional woven fabric is formed by preparing wefts and warps both of the raw material fibers, laying the wefts in numerous layers, and causing the warps to intersect each other as laid between two or more layers of wefts. By this method, the compressing force generated during the course of the hot-press fabrication can be caused to act nearly perpendicularly on both the warps and wefts and ensure production of a fiber-bond type ceramic material of dense texture.
It is also permissible to form a woven fabric by preparing biaxial two-dimensional planar woven fabrics using wefts and warps both of the raw material fibers, superimposing the planar woven fabrics, and uniting the superposed woven fabrics with obliquely intersecting third threads. By this method, the compressing force of the hot-press fabrication can be caused to act nearly perpendicularly on the
Hirokawa Tetsurou
Masaki Shouju
Tanamura Takeshi
Yamamura Takemi
Derrington James
Griffin & Szipl, P.C.
Ishikawajima-Harima Heavy Industries
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