JPH07314207A - Cutting tool made of surface covered wc group cemented carbide alloy - Google Patents

Abstract

PURPOSE:To enhance chipping resistance by including a precribed wt.% of Co at least in the upper layer out of the lower, intermediate, and upper layers of a compound hard coating layer. CONSTITUTION:The TiC layer, TiN layer or TiCN layer having a glanular structure in the crystal grain thereof are formed as a lower layer by means of the ordinary hight-temperature CVD method. On this lower layer a TiCN layer of an intermediate layer having a prismatic crystal structure in which crystal grains have been grown in the direction perpendicular to the surface of the base body is formed. On this intermediate layer a TiC layer or TiCNO layer of an upper layer is formed. Then, this is subjected to heat treatment under a prescribed condition, and Co of 0.01 to 6wt.% is diffusedly included in the TiC layer or TiCNO layer of the upper layer. On the upper layer containing Co of 0.01 to 6wt.% like this, an uppermost layer of Al2O3 or TiN layer is formed for enhancing chipping resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is based on a tungsten carbide (hereinafter referred to as WC) -based cemented carbide as a base material, and a surface-coated WC-based superhard material formed by forming a composite hard coating layer having excellent adhesion on the surface thereof. The present invention relates to a hard alloy cutting tool, and even if it is used for intermittent cutting such as milling cutting under more severe conditions than before, chipping does not easily occur, and a surface-coated WC-based cemented carbide cutting tool that exhibits excellent cutting performance. It is about.

[0002]

2. Description of the Related Art Generally, on a surface of a WC-based cemented carbide substrate, a lower layer made of titanium carbide, titanium nitride or titanium carbonitride, each of which has a grain structure, and carbonitride formed on the lower layer. A composite hard coating layer consisting of an intermediate layer made of titanium, an upper layer made of titanium carbide or titanium oxycarbonitride formed on the intermediate layer, and an uppermost layer made of aluminum oxide formed on the upper layer was formed. A surface-coated WC-based cemented carbide cutting tool is known, and this composite hard-coated layer is a WC-based cemented carbide cutting tool manufactured by a high temperature chemical vapor deposition method (hereinafter referred to as HT-CVD method) at a temperature of over 900 ° C. It is well known that the surface-coated WC-based cemented carbide cutting tool having a composite hard coating layer formed on the surface of is used for intermittent cutting of steel and the like.

[0003]

However, the above-mentioned conventional H
The composite hard coating layer composed of the lower layer, the middle layer, the upper layer and the uppermost layer formed on the surface of the WC-based cemented carbide substrate by the T-CVD method has insufficient toughness in the upper layer as the number of layers increases, and sufficient chipping resistance is obtained. Therefore, the conventional HT-CVD method cannot obtain a surface-coated WC-based cemented carbide cutting tool that can be used under severe conditions.

The present inventors have investigated the cause of the conventional surface-coated WC-based cemented carbide cutting tool having poor chipping resistance, and as a result, formed the WC-based cemented carbide substrate surface by the conventional HT-CVD method. The composite hard coating layer consisting of the lower layer, the middle layer, the upper layer, and the uppermost layer thus formed has a lower Co content in the upper layer as the lower layer becomes a barrier and becomes a multilayer, and thus the toughness of the entire composite hard coating layer is insufficient. It was found that sufficient chipping resistance could not be obtained.

[0005]

Therefore, the present inventors have
As a result of conducting research to obtain a surface-coated WC-based cemented carbide cutting tool with better chipping resistance than before,
(A) 700 using recently developed organic CN compound
Chemical vapor deposition at temperatures up to 900 ° C.
In the TiCN layer formed by the medium temperature chemical vapor deposition method (hereinafter referred to as MT-CVD method) described in Japanese Patent Publication No. 2 (1993), crystal grains grow in a direction perpendicular to the surface of the substrate to form a columnar crystal structure, and at the same time, WC-based cemented carbide. (B) TiC having a relatively thin thickness of 0.01 to 2.0 μm of crystal grains having a granular structure on the surface of the WC-based cemented carbide substrate, which acts to absorb Co contained in the alloy substrate to the surface. Layer, TiN layer or TiCN
Even if the layer is formed as a lower layer by the usual high temperature CVD method, C
o It does not serve as a suction barrier, but rather improves adhesion, and the middle layer of Ti has a columnar crystal structure in which the crystal grains grow in a direction perpendicular to the substrate surface on the lower layer.
A CN layer is formed, an upper TiC layer or a TiCNO layer is formed on the middle layer by a normal high temperature CVD method, and then heat treatment is performed under predetermined conditions. 6 wt% can be diffused and contained, and such Co is 0.01 to 6 wt%
A top Al ₂ O ₃ layer or T over the included top layer
The composite hard coating layer obtained by forming the iN layer has a conventional H content.
It was found that the surface-coated WC-based cemented carbide cutting tool obtained by the T-CVD method is superior in chipping resistance.

The present invention has been made on the basis of the above findings, and uses a normal WC-based cemented carbide as a substrate,
The lower layer made of titanium carbide, titanium nitride, or titanium carbonitride whose crystal grains formed on the surface have a granular structure, and the crystal grains formed on the lower layer are perpendicular to the surface of the WC-based cemented carbide substrate. A middle layer made of titanium carbonitride having a columnar crystal structure grown in a direction, an upper layer having a grain structure of crystal grains made of titanium carbide or titanium oxycarbonitride formed on the middle layer, and on the upper layer. Surface coating W consisting of aluminum oxide, titanium nitride or a composite hard coating layer having an uppermost layer consisting of aluminum oxide and titanium nitride in which the formed crystal grains have a granular structure
A C-based cemented carbide cutting tool, wherein C is present in at least an upper layer of the lower layer, middle layer and upper layer of the composite hard coating layer.
It is characterized by a surface-coated WC-based cemented carbide cutting tool containing o in an amount of 0.01 to 6% by weight.

The crystal grains of the present invention have a columnar structure T
To form the iCN inner layer, the reaction gas composition is TiC.
l _4: 1 to 4% by volume, CH ₃ OH: 0.1 to 1% by volume,
N ₂ : 0 to 25% by volume, H ₂ : consisting of the rest, and formed under the conditions of reaction temperature: 800 to 900 ° C. and pressure: 30 to 200 torr.

The thickness of the lower layer is 0.01 to 2.0 μm, preferably 0.1 to 1.0 μm, and the thickness of the middle layer of TiC is
The thickness of the N layer is 2 to 20 μm, preferably 2 to 10 μm, and the amount of Co contained in at least the upper layer is 0.
It is from 01 to 6% by weight, preferably from 0.01 to 3.0% by weight.

[0009]

EXAMPLES Co: 6.5% by weight, TiC: 2% by weight, T
aC: 4% by weight, TiN: 1% by weight, balance W
CIS has a component composition consisting of C and inevitable impurities.
A throw-away tip having a shape defined in the standard SNMG432 is prepared, and this throw-away tip is used as a WC-based cemented carbide substrate, and the following (1) and (2) are provided on the surface of this WC-based cemented carbide substrate. Alternatively, the HT-CVD method under the condition shown in (3) is used to form a TiC layer having a granular crystal grain, T
A lower layer composed of an iN layer or a TiCN layer is formed, and then MT-C under the condition shown in (6) below is formed on the lower layer.
A TiCN intermediate layer having columnar crystal grains is formed by the VD method, and TiC having granular crystal grains is formed on the TiCN intermediate layer by the HT-CVD method under the conditions shown in (1) or (4) below.
A layer or an upper layer consisting of a TiCNO layer, and then
After heat treatment under the conditions shown in Table 1 below, an Al ₂ O ₃ layer having granular crystal grains and / or TiN is formed by the HT-CVD method under the conditions shown in (2) or (5) below.
The uppermost layer consisting of layers was formed to produce the coated cutting tools 1 to 10 of the present invention shown in Table 2.

[0010]

[Table 1]

[0011]

[Table 2]

For comparison, the lower layer, the middle layer and the upper layer in which the crystal grains are granular are formed by the HT-CVD method under the conditions shown in the following (1) to (4), and the following is performed without further heat treatment. (5) and / or (2) under the conditions of the HT-CVD method, the crystal grains are granular Al ₂
Conventional coated cutting tools 1 to 10 shown in Table 3 by forming an uppermost layer consisting of an O ₃ layer and / or a TiN layer.
Was produced.

[0013]

[Table 3]

Conditions for forming hard coating layer (1) Conditions for forming TiC layer in which crystal grains have a granular structure Reactive gas composition: TiCl ₄ : 2% by volume, CH ₄ : 5% by volume, H ₂ : 93% by volume, pressure : 100 torr, reaction temperature: 1030 ° C.,

(2) TiN whose crystal grains have a granular structure
Layer forming conditions Reaction gas composition: TiCl ₄ : 2% by volume, N ₂ : 20% by volume, H ₂ : 78% by volume, pressure: 200 torr, reaction temperature: 1000 ° C.,

(3) TiC in which crystal grains have a granular structure
Conditions for forming N layer Reaction gas composition: TiCl ₄ : 2% by volume, CH ₄ : 5% by volume, N ₂ : 20% by volume, H ₂ : 73% by volume, pressure: 100 torr, reaction temperature: 1030 ° C.,

(4) TiC whose crystal grains have a granular structure
Conditions for forming NO layer Reaction gas composition: TiCl ₄ : 2% by volume, CO: 3% by volume, N ₂ : 3% by volume, H ₂ : 92% by volume, pressure: 100 torr, reaction temperature: 1000 ° C.

(5) Al ₂ whose crystal grains have a granular structure
Conditions for forming O ₃ layer Reaction gas composition: AlCl ₃ : 5% by volume, CO ₂ : 8% by volume, H ₂ : 87% by volume, pressure: 100 torr Reaction temperature: 1000 ° C.,

(6) TiC in which the crystal grains have a columnar structure
Conditions for forming N layer Reaction gas composition: TiCl ₄ : 2% by volume, CH ₃ CN:
0.5% by volume, H ₂ : 97.5% by volume, pressure: 50 torr, reaction temperature: 850 ° C.,

With respect to the coated cutting tools 1 to 10 of the present invention and the conventional coated cutting tools 1 to 10, a work material: a round bar with a slit of SCM440 (hardness: H _B 220) Cutting speed: 170 m / min Delivery: 0 0.25 mm / rev. Depth of cut: 1.5 mm Cooling oil: Dry intermittent cutting test was conducted under the condition, and after 10 minutes, the maximum flank wear amount of the cutting edge was measured, and the damage condition of the cutting edge was also observed. The results are shown in Table 4.

[0021]

[Table 4]

From the results shown in Tables 1 to 4, in the coated cutting tools 1 to 10 of the present invention, Co is contained in the upper layer below the uppermost layer, whereas in the conventional coated cutting tools 1 to 10, the upper layer is formed. C
When o is not detected and a dry interrupted cutting test under the above conditions is performed using these coated cutting tools 1 to 10 of the present invention and conventional coated cutting tools 1 to 10, the coated cutting tools of the present invention 1 to 1
0 has a smaller maximum flank wear width of the cutting edge, and the damage condition of the cutting edge shows normal wear, whereas the conventional coated cutting tools 1 to 10 have a large maximum flank wear width of the cutting edge and have a sharp cutting edge. It can be seen that the blade is chipping.

[0023]

As described above, according to the present invention, it is possible to provide a surface-coated WC-based cemented carbide cutting tool exhibiting superior cutting performance to the prior art, which can greatly contribute to industrial development. Is.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C23C 16/40 28/04

Claims (3)

[Claims] 1. An ordinary WC-based cemented carbide substrate surface having a lower layer of titanium carbide, titanium nitride or titanium carbonitride having a grain structure, and the crystal grains formed on the lower layer being WC. An intermediate layer made of titanium carbonitride having a columnar crystal structure grown in a direction perpendicular to the surface of the base cemented carbide substrate, and a granular structure of crystal grains made of titanium carbide or titanium oxycarbonitride formed on the intermediate layer And a surface-coated WC-based cemented carbide cutting tool comprising a composite hard coating layer formed of an upper layer having an upper layer and an uppermost layer of aluminum oxide having crystal grains having a granular structure formed on the upper layer. At least the upper layer of the lower layer, the middle layer and the upper layer of the composite hard coating layer contains 0.01 to 6 Co.
A surface-coated WC-based cemented carbide cutting tool, characterized in that it is contained in a weight percentage. 2. The surface-coated WC-based cemented carbide cutting tool according to claim 1, wherein the uppermost layer of the composite hard coating layer is made of titanium nitride. 3. The surface-coated WC-based cemented carbide cutting tool according to claim 1, further comprising a titanium nitride layer formed on the uppermost aluminum oxide layer of the composite hard coating layer.