JPH05285740A - Hard layer coated cutting tool and its manufacture - Google Patents

Abstract

(57) [Summary] [Purpose] Physical vapor deposition T with excellent fracture resistance and abrasion resistance.
An iN hard layer coated cutting tool and a method for manufacturing the same are provided. [Configuration] (1) Residual compressive stress: 0.9 to 1.25G
A hard layer coated cutting tool obtained by coating a substrate with a physical vapor deposition TiN hard layer having Pa and having an average crystal grain size of 190 to 270 Å. (2) In a method for manufacturing a hard layer-coated cutting tool in which a TiN hard layer is physically vapor-deposited on the surface of a substrate while applying a bias voltage to the substrate, a hard layer that controls the bias voltage to be gradually lowered from the start of physical vapor deposition. Manufacturing method of coated cutting tools.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a physical vapor deposition titanium nitride hard layer (hereinafter referred to as TiN hard layer) coated cutting tool having excellent fracture resistance and wear resistance against cutting under severe conditions. is there.

[0002]

2. Description of the Related Art Generally, a cutting tool coated with a TiN hard layer by forming a TiN hard layer on the surface of a substrate composed of WC-based cemented carbide, TiCN-based cermet or ceramics by a physical vapor deposition method such as ion plating. Are known. It is known that the TiN hard layer has a high residual compressive stress of 0.9 GPa or more, and the TiN hard layer having such a high residual compressive stress has excellent fracture resistance. Regarding the residual compressive stress of the TiN hard layer,
For example, "Journal of the Japan Institute of Metals" Vol. 49, No. 2 (1985)
P120-124 and "Journal of the Japan Institute of Metals", Vol. 49, No. 9 (1985), P773-778.

[0003]

However, the TiN hard layer having a large residual compressive stress described above has low fracture resistance but low wear resistance, and a cutting tool formed by coating the TiN hard layer having a large residual compressive stress. Could not sufficiently cope with cutting under severe conditions.

[0004]

Therefore, the present inventors have
As a result of research to obtain a TiN hard layer-coated cutting tool having both excellent fracture resistance and wear resistance, the TiN hard layer formed by a conventional physical vapor deposition method and having a large residual compressive stress has an average crystal grain size of Although the wear resistance was insufficient due to the coarse grains of 280 Å or more, even if the residual compressive stress was large, the TiN hard layer with the average crystal grain size reduced to 270 Å or less had the above-mentioned fracture resistance. Wear resistance is improved while maintaining a high level, and the average grain size is finer than 270 Å.
It has been found that the hard layer can be obtained by controlling the bias voltage of the physical vapor deposition device so as to be gradually lowered from the start of physical vapor deposition.

The present invention has been made based on the above findings, and (1) In a hard layer-coated cutting tool having a TiN hard layer coated on the surface of a substrate, the above-mentioned TiN is used.
The hard layer is a hard layer-coated cutting tool having a residual compressive stress of 0.9 to 1.25 GPa and an average crystal grain size of 190 to 270 angstroms, and (2) the surface of the substrate while applying a bias voltage to the substrate. In the method for manufacturing a hard layer-coated cutting tool in which a TiN hard layer is physically vapor-deposited, the hard layer-coated cutting tool in which the bias voltage is controlled to be gradually lowered from the start of physical vapor deposition is characterized.

In the conventional physical vapor deposition method, since the bias voltage applied to the substrate is kept constant, the temperature of the substrate gradually rises when the physical vapor deposition is continued, and the residual compression of the TiN hard layer formed on the substrate surface is caused. It is considered that the stress is increased and the crystal grains of the TiN hard layer are coarsened at the same time, and the wear resistance of the TiN hard layer is reduced. On the other hand, when the bias voltage applied to the substrate is gradually decreased as in the present invention,
The temperature of the substrate is kept constant, coarsening of the crystal grains of the TiN hard layer is avoided, and the residual compressive stress of the TiN hard layer is 0.
It was maintained within the range of 9 to 1.25 GPa, and the wear resistance was improved by refining the crystal grains of the TiN hard layer while maintaining the fracture resistance at almost the same level as the conventional level. Conceivable.

If the residual compressive stress of the TiN hard layer of the hard layer-coated cutting tool of the present invention is less than 0.9 GPa, sufficient fracture resistance cannot be obtained, while the residual compressive stress is 1.25.
When it is larger than GPa, the adhesiveness is remarkably deteriorated, which is not preferable. Therefore, Ti of the hard layer coated cutting tool of the present invention
Residual compressive stress of N hard layer is 0.9GPa-1.25GP
set to a.

Further, it is difficult to control the average crystal grain size of the TiN hard layer to less than 190 angstroms by the method of lowering the bias voltage of the present invention from the start to the end of physical vapor deposition. On the other hand, without lowering the bias voltage. If the average crystal grain size is larger than 270 angstroms, the wear resistance sharply decreases, which is not preferable. Therefore, the average crystal grain size of the TiN hard layer is set to 190 to 270 angstrom.

The residual compressive stress of the TiN hard layer is 0.9
GPa to 1.25 GPa and average grain size of 190 to
The bias voltage applied to reach 270 Å is preferably dropped in the range of 50-700V.

[0010]

Embodiments of a hard layer-coated cutting tool and a method for manufacturing the same according to the present invention will now be specifically described with reference to the drawings.

As raw material powder, average particle diameter: 3 μm
m Co powder, TiC powder, TaC powder, WC powder are prepared, and these powders are Co powder: 9 wt%, TiC powder: 1 wt%, TaC powder: 2 wt%, and the rest: WC powder. After blending and mixing, molding into green compact,
This green compact is sintered under normal conditions to produce a sintered body, which is then ground to ISO standard TANGA160408.
W having the shape of ISO standard P30 equivalent material
A C-based cemented carbide chip was produced.

This WC-based cemented carbide chip is used as a substrate 3 and is mounted above the reaction furnace 1 having the structure shown in FIG. 1. On the other hand, in the crucible 4 installed below the reaction furnace 1, Metal titanium 6 was filled.

In this state, the pressure in the reaction furnace 1 is set to 1 × 10.
^It was evacuated to a vacuum of ^-5 Torr, and the temperature inside the reaction furnace 1 was raised to 700 ° C by the heater 8.

While keeping the temperature in the reaction furnace 1 at this temperature, Ar gas is supplied from the mass flow controller 9 through the reaction gas introduction port 2 and is maintained in an Ar gas atmosphere of 5 × 10 ^-2 Torr to carry out the bombard cleaning of the substrate 3. After that,
The Ar gas was discharged from the reaction furnace 1.

Next, the metal titanium 6 is heated and evaporated by the electron beam 7, a positive voltage is applied to the discharge electrode 5, and the electron beam 7 is generated between the discharge electrode 5 and the molten metal titanium 6. A discharge is caused by the secondary electrons generated by the collision with the and the metal vapor evaporated from the surface of the molten metal titanium 6. At the same time as this operation was performed, the mass flow controller 9 was controlled by the vacuum gauge 10 and the pressure controller 11, nitrogen gas was supplied, and physical vapor deposition of the TiN hard layer was started.

After the physical vapor deposition is started, the surface temperature of the substrate 3 is monitored by the radiation thermometer 12, and the signal is sent to the bias power source 13 via the temperature controller 14 to show the surface temperature of the substrate 3. In order to maintain the temperature shown in Table 1, the bias voltage is gradually reduced under the conditions shown in Table 1 for 60 minutes to perform physical vapor deposition, and the manufacturing methods 1 to 20 of the coated cutting tool having the TiN hard layer with a thickness of 3.0 μm are carried out. did.

[0017]

[Table 1]

Manufacturing method 1 to 20 of the above hard layer-coated cutting tool
Regarding the hard layer coated cutting tools 1 to 20 obtained by
Using CuKα rays (parallel beam), the residual compressive stress σ _γ of the TiN hard layer was determined from the 2θ-sin ² ψ relationship straight line using the following formula, and the results are shown in Table 2. σ _γ = {(E · cot θo) / 2 (1 + ν)} · {π / 1
80} · {δ (2θ) / δ (sin ² ψ)} where θo: standard Bragg angle E: Young's modulus ν: Poisson's ratio σ _γ : residual compressive stress Further, the TiN hard layer is subjected to X-ray diffraction, The average crystal grain size was calculated by the Scherrer's equation using the full width at half maximum of the (200) plane, and the results are shown in Table 2.

For hard layer coated cutting tools 1 to 20 having the residual compressive stress and average grain size shown in Table 2,
An intermittent dry cutting test and a continuous dry cutting test were performed under the following conditions, and the results are also shown in Table 2.

Intermittent dry cutting test Work material: SCM440 (Brinell hardness: 300), cylindrical body with four grooves on the outer circumference in the axial direction, cutting speed: 100 m / min., Feed: 0.21 mm / rev ., Depth of cut: 1.0 mm, Cutting time: 2 min., Intermittent dry cutting was performed, and the number of cutting edges in which a defect occurred out of 10 test cutting edges was measured.

Continuous dry cutting test Work material: SNCM439 (Brinell hardness: 250), cutting speed: 180 m / min., Feed: 0.3 mm / rev., Depth of cut: 1.5 mm, continuous dry cutting , Flank wear width: V _B is 0.3
The time (minutes) required to reach mm was measured, and at this time, the crater wear depth at the time of cutting for 15 minutes was also measured.

[0022]

[Table 2]

[0023]

EFFECT OF THE INVENTION Manufacturing method 1 of the coated cutting tool shown in Table 1
The physical properties of the TiN hard layer-coated cutting tools 1 to 20 having the residual compressive stress and the average crystal grain size shown in Table 2 were physically vapor-deposited under the conditions of 20 to 20 and the residual compressive stress was 0.9 GP.
a to 1.25 GPa and average grain size:
TiN in the range of 190-270 Angstroms
It can be seen that the coated cutting tools 8 to 15 of the present invention having the hard layer have the most excellent fracture resistance and wear resistance.

However, the residual cutting stress is 0.8 GPa or less and the average grain size is in the range of 190 to 270 angstroms, and the coated cutting tools 1 to 7 which are external to the present invention and the residual compressive stress are 1.32 GPa or more. Thus, it can be seen that the coated cutting tools 16 to 20 which are external to the present invention and have an average crystal grain size of more than 270 angstroms have reduced fracture resistance and wear resistance.

As described above, the TiN hard layer-coated cutting tool whose residual compressive stress and average crystal grain size are adjusted to predetermined ranges can sufficiently cope with cutting under severe conditions and is excellent in industry. It has a great effect.

[Brief description of drawings]

FIG. 1 is a schematic view of a physical vapor deposition apparatus used for manufacturing a hard layer-coated cutting tool of the present invention.

[Explanation of symbols]

 1 Reactor 2 Reactant Gas Inlet 3 Substrate 4 Crucible 5 Discharge Electrode 6 Metal Titanium 7 Electron Beam 8 Heater 9 Mass Flow Controller 10 Vacuum Gauge 11 Pressure Controller 12 Radiation Thermometer 13 Bias Power Supply 14 Temperature Controller

Claims (2)

[Claims] 1. A hard-layer-coated cutting tool comprising a substrate made of cemented carbide, cermet or ceramics and a titanium nitride (hereinafter referred to as TiN) hard layer coated on the surface thereof, wherein the TiN hard layer has a residual compressive stress: 0.9-1.25
A hard layer-coated cutting tool having GPa and having an average crystal grain size of 190 to 270 angstroms. 2. A substrate made of cemented carbide, cermet or ceramics is placed in a reaction furnace of an ordinary physical vapor deposition apparatus, and a TiN hard layer is physically deposited on the surface of the substrate while applying a bias voltage to the substrate. A method for manufacturing a hard layer-coated cutting tool, characterized in that the bias voltage is controlled so as to be gradually lowered from the start of physical vapor deposition.