Cermet tool and process for producing the same

Details Cermet tool and process for producing the same Cermet tool and process for producing the same

1999-03-31

2001-05-22

Thibodeau, Paul (Department: 1773)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Including a second component containing structurally defined...

C428S332000, C428S336000, C428S698000, C428S699000

Reexamination Certificate

active

06235382

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a cermet tool and a process for producing the same.
BACKGROUND FOR THE INVENTION
A cermet sintered body, which comprises a hard phase mainly comprising a carbonitride of Ti and a 4a, 5a, 6a Group element component other than Ti (V, Cr, Zr, Nb, Mo, Hf, Ta and W), the hard phase being bound with a binder metallic phase mainly comprising Ni and/or Co is known. Such bodies have excellent plastic deformation resistance, etc. in comparison to super hard alloys which have also been conventionally used. Therefore the sintered bodies are replacing the super hard alloys as cutting tools. The cermet tool is often used in the form in which a hard coating layer of a carbide, a nitride or a carbonitride of Ti or alumina is formed on the surface, to further improve the wear resistance and the plastic deformation resistance.
The formation of a hard layer on the cermet tool described above has been conducted by a gas phase film formation method, such as a physical vapor deposition method, a chemical vapor deposition method, and the like. In this method, however, the hard layer is formed after firing the cermet by conducting another gas phase film forming method as another step. Furthermore, a pretreatment step such as surface polishing, a subsequent surface cleaning or modifying, etc. is necessary before the film formation. As a result, the number of steps is excessive, which leads to an increase in the price of the tool.
An object of the present invention is to provide a cermet tool having a surface coating layer which exhibits a function equivalent to or higher than a hard coating layer of a conventional cermet tool, and being economical in that steps such as a gas phase film forming step is not necessary. Another object of the invention is to provide a process for producing the same.
BRIEF SUMMARY OF THE INVENTION
In essence, the present invention contemplates a cermet tool which includes a binder metallic phase and a hard phase forming a cermet body and a surface coating layer formed on an outermost surface of the cermet body. The binder metallic phase mainly comprises Ni, or Ni and Co (hereinafter referred to as a binder metallic phase forming component). The hard phase contains, as a metallic element component of the phase (hereinafter referred to as a hard phase metallic element component), Ti constituting its main part, and one or more of an additional metallic element component M selected from V, Cr, Zr, Nb, Mo, Hf, Ta and W. The hard phase mainly comprises a carbonitride of the hard phase metallic element component.
A surface coating layer is formed on an outer surface of the cermet body. This surface coating layer mainly comprises the same materials as in the hard phase of the cermet body. However, the weight content of the binder metallic phase forming component is smaller than an average weight content of the binder metallic phase forming component throughout the cermet body. In addition, the weight content WB
1
of the binder metallic phase forming component in the surface coating layer of the cermet body and a weight content WB
2
of the binder metallic phase forming component of a residual part (hereinafter referred to as a main body part) other than the surface coating layer satisfy the following equation:
0.1
≦WB
1
/
WB
2
≦0.7
In a preferred embodiment of the invention, a surface coating layer is formed on the surface outermost part of the cermet body. This surface coating layer mainly comprises the same elements as in the hard phase of the ceramic tool. However, the weight content of the binder metallic phase forming component in the surface coating is less than the average weight content of the binder metallic phase forming component throughout the cermet tool. Also the weight content WR
1
of the hard phase metallic element component and a weight content WB
1
of the binder metallic phase forming component in the surface coating layer of the cermet tool, and a weight content WR
2
of the hard phase metallic element component and a weight content WB
2
of the binder metallic phase forming component of a residual part (hereinafter referred to as a main body part) other than the surface coating layer satisfies the following equations:
0.005
≦WB
1
/
WR
1
≦0.14
0.05
≦WB
2
/
WR
2
≦0.2
The invention will now be described in connection with the accompanying figures.


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