Stock material or miscellaneous articles – All metal or with adjacent metals – Component of composite having metal continuous phase...
Reexamination Certificate
1998-05-11
2001-01-09
Mai, Ngoclan (Department: 1742)
Stock material or miscellaneous articles
All metal or with adjacent metals
Component of composite having metal continuous phase...
C419S008000, C419S010000, C419S045000
Reexamination Certificate
active
06171709
ABSTRACT:
TECHNICAL FIELD
This invention relates to a composite comprising wear-resistant material with superabrasive particles and ductile metal. Common structural metallic materials can be used to make the substrate, which may be a block in various forms (including plates), and they are prepared either through a compressive work such as forging, rolling, extrusion and HIPping or by foundry.
BACKGROUND TECHNIQUE
As wear-resistant materials comprising superabrasive particles, diamond or cubic boron nitride compacts are commercially produced mainly in ultrahigh pressure processes, and in which the superabrasive particles are joined immediately with each other or distributed in a ceramic matrix. While the compacts may be employed as a block of totally uniform structure, they are more commonly used as a composite with a carbide backing to which the superabrasive particles are joined during the sintering of the particles themselves. The latter composition is taken mainly as demanded in the subsequent steps of machining into the final shape or brazing to the support, where a less superabrasive thickness is favored for a higher efficiency, or a such backing facilitates the work.
However carbide alloy, being a hard and brittle material, cannot fully comply with the residual stresses which occur at the carbide and superabrasive interface after cooled down due to the difference in thermal expansion coefficient. They may eventually cause to disjoint the layers at a slightest external load.
Further, the use of carbide alloy is not advantageous for the rather high material cost and high specific gravity.
It is known to use a self-propagating high-temperature synthesis (SHS) for the preparation of some types of functional materials. The technique is based on the process which occurs with appropriate material systems: a combustion, once initiated by igniting at a spot, sustains itself and propagates throughout the rest of the material, due to an intense production of heat which spreads and causes a sufficient temperature rise. It is useful for the production of such compounds as, for example, carbide, nitride, boride, silicide or oxide of the fourth or fifth group metals of the periodic table, including Ti, Zr, Ta, Si, as well as intermetallic compounds. This technique is fully described in “The chemistry of SHS”, published by T.I.C. (1992).
An SHS process, which can produce high temperatures over a short period of time almost adiabatically, is employed for the formation and sintering, simultaneous or subsequent, of high melting materials and, if tentatively, for the preparation of compact of various materials. For the materials, these techniques are available: static compression with a mechanical press, instantaneous compression by explosive detonation, isostatic compression with a HIP system, quasi HIP process whereby the formed compact is squeezed from around with a mechanical press in a die by means of molding sand.
One of the principal objects of the present invention is to eliminate the above described problems which are associated with conventional processes and products involving an ultrahigh pressure technique, and thereby to provide a heat-resistant product, and also a method for effectively producing the same, which comprises a metallic layer improved both in mechanical material strength and thermal stability of the joint strength to the ceramic substrate. This has been achieved effectively on the basis of an SHS technique.
This is an advanced variation of our previous applied invention which is based on a combined process of SHS with compression and in which metallic ingredients are molten with the intense heat of an SHS reaction and allowed to penetrate the skeletal structure of in situ formed ceramic material, so that the gaps within and among it are filled in. The product of compact structure exhibits a high resistance to both heat and abrasion that conventional techniques could not achieve.
DISCLOSURE OF INVENTION
The composite of the invention essentially comprises a substrate of metallic block and a functional or working layer of ceramic material with superabrasive particles, and is characterized by that the latter is joined to the former on a surface by means of molten metal which occurred in the course of the SHS process.
The composite of the invention is effectively produced by:
(1) mixing a composition of powders so formulated as to be capable of undergoing an SHS process to yield a ceramic product and forming into one or more pellets, with superabrasive particles being distributed at least in the region to serve finally as the working surface; (2) arranging the pellet or pellets in the adjacency of said metallic block to complete the material system, while securing in this system the presence of metallic material to be molten during the SHS process; (3) causing to initiate said process in said system, whereby said metallic material is molten at least partly as heated by the reaction heat; (4) exert compression with a press in 0.1 to 10 seconds from the completion of the process and holding for 2 seconds at least in order to secure the joint of the ceramic and metallic bodies.
REFERENCES:
patent: 4655830 (1987-04-01), Akashi et al.
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patent: 4923490 (1990-05-01), Johnson et al.
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patent: 5330701 (1994-07-01), Shaw et al.
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Borovinskaya Inna P.
Hosomi Satoru
Koizumi Mitsue
Levashov Evgeny A.
Ohyanagi Manshi
Larson & Taylor PLC
Mai Ngoclan
The Ishizuka Research Institute Ltd.
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