Stock material or miscellaneous articles – Self-sustaining carbon mass or layer with impregnant or...
Reexamination Certificate
2001-09-24
2003-12-02
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
Self-sustaining carbon mass or layer with impregnant or...
C428S156000, C428S174000, C428S325000, C428S336000, C428S697000, C428S698000, C428S699000
Reexamination Certificate
active
06656591
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a diamond-coated body, and more particularly to such a diamond-coated body in which a diamond coating is fixed to a substrate with a sufficiently high strength even where the substrate is made of a super-fine particle cemented carbide with a high Co content, and also to a method of manufacturing the same.
2. Discussion of the Related Art
As one type of a cutting tool such as an end mill, a tap and a drill, there is proposed a diamond-coated cutting tool in which a tool substrate made of a cemented carbide is coated with a diamond coating. In a process of formation of the diamond coating on the tool substrate in accordance with a CVD (chemical vapor deposition) method or other method, at a raised temperature of 700-1000° C., Co (cobalt) contained in the cemented carbide is separated from the tool substrate due to the raised temperature so that diamond particles of the diamond coating are graphitized. Such graphitization of the diamond particles undesirably reduces an adhesive or bonding strength with which the diamond coating is bonded to the tool substrate. In the interest of avoiding the separation of the Co from the tool substrate, the tool substrate is commonly subjected to an acid treatment in which Co adjacent to the surface of the substrate is removed by using a suitable acid such as sulfuric acid or nitric acid, prior to the formation of the diamond coating on the substrate. However, where the substrate is made of a super-fine particle cemented carbide having high a Co content, even if Co adjacent to the surface of the substrate has been completely removed from the substrate, Co contained in the substrate comes to the surface of the substrate in a large amount during the heating of the diamond coating. Thus, it is not possible to avoid the reduction in the strength of bonding of the diamond coating to the substrate, making it impossible to use, as the material of the tool substrate, the super-fine particle cemented carbide which inherently has a higher degree of toughness or unbrittleness owing to its high Co content, than the other cemented carbide, and which is advantageously used as the material of the substrate of the cutting tool serving to cut particularly a cast iron or other hard materials.
JP-B2-6-951 (publication of examined Japanese Patent Application laid open in 1994) discloses a diamond-coated body including a substrate, a crystalline diamond coating, an interface layer which is made of TiC or other material, and a layer which has a non-crystalline carbonized structure. In this diamond-coated body, the interface layer is disposed on the substrate, and the non-crystalline carbonized structure layer is disposed on the interface layer so as to be interposed between the interface layer and the diamond coating. This arrangement makes it possible to use, as the material of the substrate, the super-fine particle cemented carbide having a high Co content.
However, in manufacturing the above-described diamond-coated body, it is necessary to implement a step of forming the non-crystalline carbonized structure layer on the interface layer prior to the formation of the crystalline diamond coating. This extra step requires a cumbersome operation, increasing the manufacturing cost.
The above-described drawbacks or problems are encountered not only where the diamond-coated tool takes the form of a cutting tool but also where the diamond-coated tool takes the form of other machining tools such as a cold-forming tool which is designed to form the workpiece into a desired shape by plastically deforming the workpiece.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a diamond-coated body in which a diamond coating is fixed to a substrate with a sufficiently high strength even where the substrate is made of a super-fine particle cemented carbide with a high Co (cobalt) content. This first object may be achieved according to any one of first through eleventh aspects of the invention which are described below.
It is a second object of the invention to provide a method of manufacturing a diamond-coated body in which a diamond coating is fixed to a substrate with a sufficiently high strength even where the substrate is made of a super-fine particle cemented carbide with a high Co content. This second object may be achieved according to either of twelfth and thirteenth aspects of the invention which are described below.
The first aspect of this invention provides a diamond-coated body comprising: a substrate made of a cemented carbide; a diamond coating; and an interface layer interposed between the substrate and the diamond coating, wherein the interface layer consists of a solid solution including an aluminum nitride and a metal which belongs to one of groups IVa, Va and VIa of the periodic table. It is noted that the diamond-coated body of the invention can be also interpreted to comprise the above-described substrate, and a multilayer coating which covers the substrate and which includes the above-described diamond coating as its outer layer and the above-described interface layer as its inner layer. In other words, the diamond coating and the interface layer can be also interpreted to cooperate with each other to provide a multilayer coating which covers the substrate. It is further noted that the above-described interface layer can be also referred to as an intermediate layer.
According to the second aspect of the invention, in the diamond-coated body defined in the first aspect of the invention, the diamond coating is held in contact with the interface layer. The crystalline diamond coating is disposed directly on an outer surface of the interface layer, without a layer consisting of a non-crystalline carbonized structure which is conventionally provided to be interposed between the interface layer and the diamond coating, as discussed above in Discussion of the Related Art.
According to the third aspect of the invention, in the diamond-coated body defined in the first or second aspect of the invention, the interface layer includes one of TiAlN (aluminum titanium nitride), CrAlN (aluminum chromium nitride) and VAlN (aluminum vanadium nitride), and is formed on a surface of the substrate in accordance with a physical vapor deposition method. It is noted that TiAlN is interpreted to mean a solid solution including an aluminum nitride and Ti, that CrAlN is interpreted to mean a solid solution including an aluminum nitride and Cr, and that VAlN is interpreted to mean a solid solution including an aluminum nitride and V.
According to the fourth aspect of the invention, in the diamond-coated body defined in any one of the first through third aspects of the invention, the substrate is made of a super-fine particle cemented carbide which includes WC (tungsten carbide) as a main component thereof, the super-fine particle cemented carbide further including Co such that a content of Co therein is 3-25 wt %.
According to the fifth aspect of the invention, in the diamond-coated body defined in the fourth aspect of the invention, the content of Co in the super-fine particle cemented carbide is 5-10 wt %.
According to the sixth aspect of the invention, in the diamond-coated body defined in the fourth aspect of the invention, the super-fine particle cemented carbide includes a hard phase which is provided by particles whose average diameter is not larger than 1 &mgr;m.
According to the seventh aspect of the invention, in the diamond-coated body defined in any one of the first through sixth aspects of the invention, the substrate has pits and projections formed on a surface thereof such that the surface of the substrate has a roughness curve whose maximum height Ry is within a range from 0.5 &mgr;m to 2 &mgr;m.
According to the eighth aspect of the invention, in the diamond-coated body defined in the seventh aspect of the invention, the interface layer is held in contact with the surface of the substrate which has the roughness curve, and wherein the
Hanyu Hiroyuki
Liu Hao
Murakami Yoshihiko
Oliff & Berridg,e PLC
OSG Corporation
Turner Archene
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