Coating processes – Solid particles or fibers applied – Uniting particles to form continuous coating with...
Reexamination Certificate
2000-06-29
2003-08-19
Chen, Bret (Department: 1762)
Coating processes
Solid particles or fibers applied
Uniting particles to form continuous coating with...
C427S450000, C427S452000, C427S249200, C427S900000
Reexamination Certificate
active
06607782
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to compositions, to coatings and articles made from such compositions, and to methods of making and using such compositions, coatings and articles. In another aspect, the present invention relates to nitride, carbide, carbonitride, boride, sulphide, chalcogenide, and silicide compositions, to coatings and articles made from such compositions, and to methods of making and using such compositions, coatings and articles. In even another aspect, the present invention relates to compositions of nitrides, carbides, carbonitrides, borides, sulphides, chalcogenides, and silicides, also having present one or more of nitrides, carbides, carbonitrides, borides, or silicides, to coatings and articles made from such compositions, and to methods of making and using such compositions, coatings and articles. In still another aspect, the present invention relates to cubic boron nitride compositions, to coatings and articles made from such cubic boron nitride compositions, and to methods of making and using such compositions, coatings and articles. In yet another aspect, the present invention relates to compositions of cubic boron nitride having present one or more of nitrides, carbides, carbonitrides, borides, sulphides, chalcogenides, and silicides, to coatings and articles, especially tools and cutting tools, made from such compositions, and to methods of making and using such compositions, coatings and articles.
2. Description of the Related Art
The development of harder materials has created the nee for both processing techniques, and tools with a work surface capable of shaping and cutting workpieces mad of such hard materials.
For example, in recent years grinding has gained its significance as a stock removal process for shaping and sizing both hard and soft materials in contrast to what was realized in the past as a metal finishing operation an a process to be worked on very hard materials. Cutting tools have been pushed into more and more applications in which harder materials are cut at higher speeds, requiring the tool to be longer lasting, tougher an more wear resistant.
To meet the ever increasing demands for improved productivity in the field of grinding and metal cutting, various new techniques have been introduced and are being investigated. These processes basically are intended to provide for high rate stock removal, with improved work piece quality and prolonged grinding wheel and cutting tool life.
One of the most important requirements to be satisfied by the grinding wheels is free cutting action. This necessitates availability of large chip clearance volume ahead of individual crystals. The gap between the adjacent grit in the direction of cutting should be wide enough, and at the same time, the protrusion of the grit above the bond should be large enough to facilitate this gap clearance. Along with these conditions another requirement to be fulfilled is that the bond between grits and matrix should be strong to retain the grit throughout its useful life. The bonding material should have desirable mechanical properties like strength, hardness, good adhesion to the substrate, low solubility in the ground material, and resistance to yielding during actual grinding.
As can be expected, there have been many attempts in the prior art at providing tools having extremely hard work surfaces for cutting and/or grinding such hard workpieces.
For example, boron nitride formed under high pressure includes cubic boron nitride (hereinafter referred to as cBN) and wurtzite boron nitride (hereinafter referred to as wBN). These have the highest hardness next to diamond, and are very promising for grinding and cutting uses. For grinding, the boron nitride material has already been used broadly. For cutting, a cBN compact/bulk bonded by a metal, such as cobalt, has been developed. However, this compact of cBN bonded by a metal has, when used as a cutting tool, various defects. For example, high temperatures generated during the cutting process cause the bonding metal to soften resulting in lowered wear resistance.
High pressure form boron nitride has excellent properties such as high hardness and high heat conductivity, for use as a material for a tool. In a cutting tool, for example, if the other conditions are the same, the higher the heat conductivity of the tool material, the lower the temperature at the cutting tip, which is more advantageous from the standpoint of improving the wear resistance of the tool. In the case of intermittent cutting as in the case of milling cutter, heat shock is imparted to the tool by the rapid rise and fall of the temperature, thereby causing cracks. However, when a tool has a higher heat conductivity, i.e. transmits heat faster, resulting in a faster reduction in the temperature gradient between the temperature of the surface of the tool and temperature of the interior of the tool, resulting in lower thermal stress, and thus minimizing cracks.
cBN high pressure sintered ceramic tips/substrates generally include a small cBN part brazed or cemented to a carbide body. The disadvantages of such ceramic tips are that attachment of the tips with cementing or brazing is labor intensive, and the cement or braze is the weak point for tool failure.
In recent years the increase in the performance of cutting machines has resulted in a trend toward higher cutting speeds and heavier cutting. However, the strength of the cBN high pressure sintered ceramic tips is inadequate. This is especially true for high speed interrupted cutting of high strength steels such as case hardened steels and superalloys, or for cutting under severe conditions such as high feed interrupted cutting. Moreover, due to this lack of strength, the cutting edge of the cutting tip is susceptible to cracking and chipping resulting in unsatisfactory cutting performance.
The art is filled with numerous references directed to cubic boron nitride compositions in the bulk form, the following described patents merely being just a few.
U.S. Pat. No. 4,334,928, issued Jun. 15, 1982, to Hara, et al., discloses a sintered compact for a machining tool and a method of producing the compact. The disclosed compact comprises 10-80 volume percent of a high pressure form of boron nitride, and the balance a matrix of at least one binder compound material selected from the group consisting of a carbide, nitride, carbonitride, boride or silicide of a IVa and Va transition metal.
U.S. Pat. No. 5,129,918, issued Jul. 14, 1992, to Chattopadhay, discloses a cubic boron nitride abrasive tool. The monolayer cBN tool is fabricated by first coating cBN grit with carbides of transition metals directly by CVD to make the surface metallurgically compatible to readily and commercially available brazing alloys known for their strength and durability. This coated grit is then brazed onto a steel substrate.
U.S. Pat. No. 5,328,875, issued Jul. 12, 1994 to Ueda, et al., discloses cubic boron nitride-base sintered ceramics for a cutting tool. The ceramics composition comprises a dispersed phase of cubic crystal boron nitride a bonding phase of one or more of titanium and aluminum carbide, nitride and carbonitride compounds including oxygen, and 20% to 48% by volume of decomposed reaction phase cubic crystal boron nitride. The decomposed reaction phase comprises one or more of titanium carbide, titanium nitride and titanium carbonitride, and one or more of aluminum oxide and aluminum nitride, as well as titanium boride.
U.S. Pat. No. 5,389,118, issued Feb. 14, 1995 to Hinterman, et al., discloses a cBN abrasive tool comprising a metal, ceramic or cemented carbide substrate and a single layer of cBN grits bonded to said substrate by a brazing alloy, characterized in that the surface chemistry of said cBN grits is modified by depositing thereon a film of silicon carbide.
U.S. Pat. No. 5,466,642, issued Nov. 14, 1995, to Tajima et al., discloses a wear resistant cBN-based cutting tool which includes a specified amount of at least one of a Ti carbide
itrid
Bhat Deepak G.
Brown William D.
Malshe Ajay P.
Russell William C.
Yedave Sharad N.
Board of Trustees of the University of Arkansas
Chen Bret
Gilbreth J. M. (Mark)
Gilbreth Mary A.
Gilbreth & Associates P.C.
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