Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
2000-05-31
2002-01-15
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C051S307000, C051S309000, C407S119000, C428S212000, C428S336000, C428S697000, C428S698000, C428S701000, C428S702000
Reexamination Certificate
active
06338894
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coated cemented carbide cutting tool member (hereinafter referred as “coated carbide member”) that resists breakage and chipping of its cutting edge for a long period of time, particularly when it is applied to cutting operations of extremely severe conditions such as high speed, high feed, thick depth-of-cut interrupted cutting of steels and cast irons.
2. Description of the Related Art
Coated carbide members are widely used in various fields of cutting operations, for example, continuous and interrupted cutting operation of metal work pieces such as steels and cast irons. Coated carbide members are typically manufactured by depositing a hard coating layer having an average thickness of 3 to 25 &mgr;m and including (a) at least one titanium compound layer having an average thickness of 0.1 to 5 &mgr;m and composed of at least one layer of granular titanium compound selected from titanium carbide (hereinafter referred to as “TiC”), titanium nitride (TiN), titanium carbonitride (TiCN), titanium oxide (Ti
2
O
3
), titanium carboxide (TiCO), titanium nitroxide (TiNO) and titanium carbonitroxide (TiCNO), (b) TiCN layer having longitudinal growth crystal structure (1-TiCN) with its average thickness of 2 to 15 &mgr;m, and (c) aluminum oxide (Al
2
O
3
) layer having an average thickness of 0.5 to 8 &mgr;m, on tungsten carbide-based cemented carbide substrate. The common technique for depositing hard coating layer includes CVD (Chemical Vapor Deposition) and/or PVD (Physical Vapor Deposition).
Al
2
O
3
has several different crystal polymorphs, among which the alpha-Al
2
O
3
is known as thermodynamically the most stable polymorph having corundum structure, and typical polymorphs of Al
2
O
3
used as a hard coating layer are stable alpha-Al
2
O
3
and meta-stable kappa-Al
2
O
3
. 1-TiCN layer is manufactured by the CVD method at moderate temperatures such as 700 to 950° using a reaction gas mixture, which includes organic cyanide compounds such as acetonitrile (CH
3
CN), such as disclosed in Japanese Unexamined Patent Publication No.6-8010 and No.7-328808.
In recent years, there has been an increasing demand for cutting operations that save labor and time. Accordingly, the conditions under which the cutting operation takes place have become more severe, i.e., high speed, high feed and thick depth-of-cut. With regard to conventional coated carbide members, the 1-TiCN layer found in conventional hard coating layers has fairly good toughness itself, and consequently the whole hard coating layer also shows sufficient toughness. Thus, the conventional hard coating layer exhibits excellent cutting performance without any chipping at cutting edge during continuous high speed cutting operations. When subjected to extremely severe cutting conditions (e.g., high speed, high feed and thick depth-of-cut interrupted cutting), however, the cutting edge of conventional hard coating layers are subject to chipping because of insufficient toughness, and, consequently, the tool lifetime becomes shorter.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a coated carbide member that resists chipping of cutting edge over long periods of time even when used for high speed, high feed, and thick depth-of-cut interrupted cutting operations of steels and cast irons.
This and other objects have been attained by the present invention, the first embodiment of which provides a coated cemented carbide cutting tool member, which includes:
a substrate and a hard coating layer deposited on the substrate, wherein the hard coating layer has an average thickness of 3 to 25 &mgr;m and includes:
(1) at least one layer having an average thickness of 0.1 to 5 &mgr;m and including a granular Ti compound selected from the group including TiC, TiN, TiCN, Ti
2
O
3
, TiCO, TiNO, TiCNO and mixtures thereof;
(2) a TiCN layer having an average thickness is 2 to 15 &mgr;m and including a longitudinal growth crystal structure; and
(3) an Al
2
O
3
layer having an average thickness of 0.5 to 8 &mgr;m;
wherein the TiCN layer includes a growth direction and a compositional gradient of carbon and nitrogen along the growth direction.
Another embodiment of the present invention is a process for producing a coated carbide member, which includes:
depositing a TiCN layer with a reactive gas, the layer having a lower portion and an upper portion; and
during the depositing, changing a concentration in the reactive gas of at least one selected from the group including CH
3
CN, CH
4
, N
2
, and mixtures thereof; wherein
the depositing of the lower portion is carried out at a deposition temperature of 850-950° C., and the depositing of the upper portion is carried out at a deposition temperature of 960-1040° C.
Another embodiment of the invention provides a coated carbide member, produced by the above-noted process.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description of the preferred embodiments of the invention.
The present invention is particularly suitable for providing a hard coating layer that is coated on the cutting member of a cutting tool. The term “cutting member” refers to the part of the cutting tool that actually cuts the work piece. Cutting members preferably include exchangeable cutting inserts which are mounted on the bit holders of turning tools, face milling cutter bodies, and end-milling cutter bodies. Cutting members also preferably include the cutting blade of drills and end-mills. The cutting member is preferably made of tungsten carbide-based cemented carbide substrates.
The order of depositing the layers (1-3) is not particularly limited, and more than one of each layer may be deposited, so long as at least one of each layer is present.
Preferably, the hard coating layer is deposited on the substrate by chemical vapor deposition and/or physical vapor deposition.
The hard coating layer preferably coats a portion of the surface, more preferably the entire surface of the cutting member. The hard coating layer preferably includes (a) at least one titanium compound layer composed of at least one layer of granular titanium compound selected from TiC, TiN, TiCN, Ti
2
O
3
, TiCO, TiNO and TiCNO, (b) 1-TiCN layer having a compositional gradient of C and N along with its growth direction, and expressed as TiC
1−x
N
x
, wherein x ranges from 0.45 to 0.95 at top portion, and it ranges from 0.05 to 0.40 at bottom portion, and (c) Al
2
O
3
layer.
Preferably, the growth direction of the (gradient) TiCN layer is from the surface on which the TiCN layer is deposited, and the terms “upper” or “top” portion and “lower” or “bottom” portion are with respect to the surface on which the TiCN layer is deposited; the lower or bottom portions being deposited first, and the upper or top portions being deposited on the lower or bottom portion. The TiCN layer may be preferably deposited on the substrate, or may also preferably be deposited on one or more intervening layers.
The present invention is particularly suitable for coated carbide member having a long lifetime and whose hard coating layer has excellent toughness characteristics. The present inventors have found:
(A) Continuous or periodical changes of the gas concentration of the reactive gas component such as CH
3
CN, CH
4
and/or N
2
during the deposition of 1-TiCN layer gives 1-TiCN layer that has a compositional gradient of C and N along with its growth direction, and preferably the concentration of C decreases and that of N increases from bottom to top in that layer. This gradient 1-TiCN layer is preferably expressed by molecular formula TiC
1−x
N
x
, wherein x is the atomic ratio of N to the sum of C and N, and it ranges from 0.45 to 0.95 at top portion of the gradient 1-TiCN layer and ranges from 0.05 to 0.40 at bottom portion of it. The concentration gradient from bottom
Hirakawa Yoshio
Honma Tetsuhiko
Kunugi Hitoshi
Ueda Toshiaki
Mitsubishi Materials Corporation
Turner Archene
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