Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Sintering which includes a chemical reaction
Patent
1992-05-05
1994-04-12
Walsh, Donald P.
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Sintering which includes a chemical reaction
419 19, 419 48, 419 49, 427189, 427191, 427193, 427205, 427226, B22F 310, B22F 312, B22F 702
Patent
active
053023404
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to a method of forming a compact ceramic layer on a metallic or a cermet body, and more particularly to a method of forming a compact ceramic layer having an enhanced bonding to the metallic or cermet bodies by utilizing a great deal of heat developed immediately by Thermit reaction which ignites conveniently under a pressurized condition.
BACKGROUND ART OF THE INVENTION
As to the conventional methods of forming a ceramic layer on the metallic or the cermet body, there are known CVD and PVD vapor deposition methods and plasma spray coating method, etc.
Further, a method for sintering a ceramic powder, a metal powder, or a mixture thereof, which utilizes the heat developed by Thermit reaction as the heat source, is disclosed in Japanese Laid-Open Patent Application No. SHO 61-186404 (which corresponds to U.S. Pat. No. 4,761,262). However, as far as the knowledge of the applicant of the present invention is concerned, no techniques have heretofore been developed, which provide the method of forming a sintered ceramic layer tightly bonded to a metallic or a cermet base material.
The above-mentioned CVD and PVD vapor deposition methods, etc. quoted as prior arts have so far involved problems or points at issue, in particular, on the bonding of coating on metals and cermets, and are unable to provide excellent characteristics of ceramic layers themselves such as resistance to abrasion, resistance to oxidation, and resistance to corrosion, etc.
OUTLINE OF THE INVENTION
The present invention has been made to solve the above-mentioned problems in the prior art, and has for its object to provide a method of forming a ceramic layer on the metallic or the cermet body, characterized by comprising the steps of placing a green ceramic compact layer forming material such as a ceramic powder, etc. on the metallic or cermet body, and immediately forming on the metallic or cermet body a compact ceramic layer having enhanced bonding properties to the metallic or cermet body under a pressurized condition with the heat developed by Thermit reaction.
To achieve the above-mentioned object, according to a first aspect of the present invention, there is provided a method of forming a ceramic layer on a metallic or cermet body, comprising the steps of placing green ceramic powders or a mixture of ceramic powders, non-metallic powders and metallic powders forming a ceramic layer, and a mixture of non-metallic element powders with metallic powders for forming a ceramic layer on the metallic or cermet body, and immediately forming on the metallic or comet body a compact ceramic layer having enhanced bonding properties to the metallic or cermet bodies under a pressurized condition with the heat developed by Thermit reaction.
To achieve the above-mentioned object, according to a second aspect of the present invention, there is provided a method of forming a ceramic layer on a metallic or cermet body as set forth in the above-mentioned first aspect, wherein in that, to start the reaction of a Thermit composition under a pressurized condition conveniently and effectively, either a Si-Thermit composition alone or a mixture of a Si-Thermit composition with another Thermit composition is used as the heat source for igniting the Thermit compositions.
To achieve the above-mentioned object, according to a third aspect of the present invention, there is provided a method of forming a ceramic layer on a metallic or a cermet body, comprising the steps of placing in layers a ceramic compact powder and a mixture of a metallic powder with a non-metallic element powder or a green compact mixture of a ceramic powder with a metallic powder on the metallic or cermet body, and immediately forming on the metallic or cermet body a compact ceramic layer having enhanced bonding properties to the metallic or cermet body under a pressurized condition with the heat developed by Thermit reaction.
To achieve the above-mentioned object, according to a fourth aspect of the present invention, there is pro
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Patent Abstracts of Japan, vol. 12, No. 109 (M-682), Apr. 8, 1988.
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Jenkins Daniel
Kabushiki Kaisha Komatsu Seisakusho
Walsh Donald P.
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