JP2002160107A - Surface coating tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface coating tool having improved chipping resistance and a stable cutting performance without reducing abrasion resistance in precise cutting operation, and stably hold surface accuracy of a workpiece in the precise cutting operation. SOLUTION: This surface coating tool has a coating layer comprising nitride, carbonitride, nitrogen oxide of Al, one or more of 4a, 5a, and 6a group metals in a periodic table, and Ti on the surface of a cemented carbide member in an arc ion plating method. One hundred or less bulky metal particles with a diameter of 1 μm or more lie in area of 50 μm2 on the coating layer surface, and an arithmetic mean roughness Ra of the cemented carbide member before forming the coating layer and an arithmetic mean roughness Ra' of the coating layer after forming the coating layer have a relation Ra'/Ra<1.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface-coated tool, and more particularly to a surface-coated tool suitable for precision machining.

[0002]

2. Description of the Related Art As a precision machining tool having a cutting amount and a feeding amount on the order of several μm to several tens μm, a surface coating tool having a hard coating layer formed on the surface of a cemented carbide member is known. Is used.

As the coating layer, a coating layer of a composite composition containing two or more metal elements is usually used. One of the coating techniques suitable for producing a coating layer having a composite composition containing two or more metal elements is an arc ion plating method, which is widely used industrially.

The arc ion plating method is a method in which a metal material serving as an evaporation source is attached to a cathode, and a vapor of the metal material is generated by arc discharge. By reacting the vapor of the metal substance with a nitrogen gas or a carbon-containing gas (such as methane or acetylene) introduced into the apparatus, a thin film of metal nitride, metal carbide, or metal carbonitride is formed on the surface of the substrate. Film.

The advantages of this method are that a composite metal composition can be formed by changing the composition of the metal material serving as the evaporation source, and that the evaporation source can be three-dimensionally arranged since it maintains a solid state as a whole. That is, the processing space can be efficiently used, and the film formation time can be shortened.

However, when an arc ion plating type coating layer forming apparatus is used, it is known that coarse particles of metal elements called macro particles and droplets adhere to the surface of the formed coating layer. . These coarse particles are particles in which arc discharge is concentrated on a certain portion of the evaporation source surface to generate coarse molten particles, which adhere to the surface of the coating layer and remain. The size of such molten particles can range from a few microns to tens of microns.

Although this particle size does not cause a problem in ordinary cutting, it becomes sufficiently large in ultra-precision cutting in which the cutting depth and the tool feed amount in cutting are on the order of microns. As a result, in the ultra-precision cutting, there is a problem that such molten particles cause a deterioration of the processing accuracy and a starting point of destruction of the hard coating layer, thereby causing a problem of a decrease in cutting performance.

[0008] Further, since cutting is a processing method in which the surface shape of a cutting tool is transferred to a workpiece, a decrease in the precision of the surface of the cutting tool due to the attachment of a metal element is directly affected by the surface accuracy of the workpiece. Leads to a decline.

As a result of repeated investigations on the above problems, the present inventor has found that when a coating layer is formed on the surface of a cemented carbide substrate, the number of coarse metal particles adhering to the surface is 1 μm square.
By suppressing not more than 00 remaining,
The present inventors have found that a surface-coated tool having improved cutting resistance without deteriorating wear resistance in precision cutting and having stable cutting performance can be obtained, and the present invention has been accomplished.

When the arithmetic average roughness of the base material before forming the coating layer on the surface of the cemented carbide is Ra and the arithmetic average roughness of the coating layer after forming the coating layer is Ra ', The ratio Ra ′ / Ra of the arithmetic average roughness before and after forming the layer is represented by R
It has been found that by setting a '/ Ra <1.0, it is possible to stably maintain the surface accuracy of a workpiece, which is an important factor in precision cutting, leading to the present invention.

[0011]

Means for Solving the Problems The present invention has been made based on such findings, and a surface-coated tool according to claim 1 is characterized in that Al or periodic table 4a, Any one or more of metals from group 5a and 6a and T
In a surface-coated tool provided with a coating layer comprising a nitride, a carbonitride, or a nitride oxide with i, it is determined that 100 or less coarse metal particles having a diameter of 1 μm or more remain on the surface of the coating layer in 50 μm squares. Features.

The surface-coated tool according to claim 2 is characterized in that Al or periodic table 4a, 5a,
In a surface-coated tool provided with a coating layer made of a nitride, carbonitride, or nitride oxide of at least one of Group 6a metals and Ti, the cemented carbide member before forming the coating layer Where Ra is the arithmetic average roughness of the coating layer and Ra ′ is the arithmetic average roughness of the coating layer after the coating layer is formed, the Ra and Ra ′ have a relationship of Ra ′ / Ra <1.0. It is characterized by the following.

In the surface-coated tool according to the first and second aspects, it is desirable that the thickness of the coating layer is 0.5 to 10 μm.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the invention according to each claim will be described in detail. The coating of the surface-coated tool according to claim 1 is made of a nitride, carbide, carbonitride, or nitride oxide of Ti or any one or more of the metals in the group 4a, 5a, and 6a of the periodic table. .

This coating layer contains Ti as an essential component and Al
Alternatively, one or two or more metal elements selected from Group 4a, 5a, and 6a metals of the periodic table such as Cr, Zr, and V, and one or more nonmetals of nitrogen, carbon, and oxygen It is composed of elements. It is desirable that the ratio of the Ti element to all the metal elements is 50 to 75 atomic%. More preferably 55 to
65% is desirable. When the ratio of the Ti element is more than 75%, the hardness of the coating layer decreases, and the wear resistance becomes insufficient when used as a cutting tool. Also, the Ti element is 50%
If less, AlN which is an unstable phase partially precipitates,
During cutting, the cutting edge may peel off or become abnormally worn.

The substrate is made of a cemented carbide. The cemented carbide may be either a K-class cemented carbide (WC-Co-based) or a P-class cemented carbide (WC-β-Co-based). Since sharp cutting edges are required for precision machining, the hard phase particle diameter is 1.
Fine or ultra-fine cemented carbide of 0 μm or less is desirable.
If the hard phase particles are larger than 1.0 μm, minute falling off of the cutting edge and plastic deformation tend to occur.

The size and the number of adhered coarse metal particles are counted by taking an electron microscope image of the coated tool surface. It is also possible to automatically count using image processing software. Electron microscope images are at magnifications of 1000 to 500
About 0 times is appropriate. The magnification is adjusted to a field of view and a field of view of 50 μm square, and the number of coarse metal particles having a diameter of 1 μm or more existing in the field of view is counted. Adhered particles having a diameter of less than 1 μm are excluded from the number of adhered particles because they do not affect the performance as a cutting tool.

The number of coarse metal particles having a diameter of 1 μm or more is 100 or less in a square of 50 μm, and 20 or less.
It is desirable that the number is not more than the number. 50μ of coarse metal particles
If more than 100 particles are present in each square, the coarse metal particles collide with the work material or chips during the cutting process and fall off, or fall off with the coating layer or a part of the base immediately below, resulting in damage to the cutting edge. , Loss, abnormal wear, etc.

The arithmetic average roughness of the cutting tool before and after forming the coating layer is measured using a stylus type surface roughness meter, a non-contact type laser surface roughness meter, or the like. As a representative value of the surface roughness, an arithmetic average roughness (Ra) specified in JIS B0601 is used. The arithmetic average roughness ratio Ra ′ / Ra before and after forming the coating layer is Ra ′ / Ra <1.0.

When Ra ′ / Ra is 1.0 or more, the arithmetic average roughness is deteriorated due to the attachment of coarse metal particles during film formation and the like, and the effect of the coating layer is deteriorated rather than the effect of improving the wear resistance by the coating layer. It causes damage, deterioration of the precision of the work, etc., and the performance as a cutting tool deteriorates. The closer to 0 the value of Ra '/ Ra is, the smoother and smoother the coating layer is. However, at the present time, the lower limit is 0.3 for reasons such as limitations on the processing accuracy of the substrate.

In order to suppress the number of coarse metal particles having a diameter of 1 μm or more from adhering to only 100 or less in a 50 μm square, the arithmetic average roughness Ra ′ / Ra of the cutting tool before and after forming the coating layer is determined. To make it less than 1.0,
By precisely controlling the behavior of the arc discharge in the evaporated metal,
It is necessary to suppress abnormal growth of the arc spot, which is a factor for generating coarse particles, and to maintain uniform evaporation of metal. Specifically, uniform evaporation can be achieved by shortening the arc spot generation time and quickly and uniformly generating the arc spot.

(Example 1) WC 90 wt% as a substrate,
A cemented carbide having a composition of Co 8 wt% and β 2 wt% was used. The WC particle size was 0.6 μm, and the β particle size was 1.0 μm. The top, side, and bottom surfaces of the sintered body were ground with a diamond wheel to obtain the desired shape and dimensions. Acid after processing,
Wash with alkali, pure water and organic solvent to remove oil, rust, stains and other stains on the surface.

An arc ion plating apparatus was used to form the coating layer, a Ti-Al alloy was used as the evaporated metal, and nitrogen was used as the raw material gas to produce a composite nitride. Where Ti
The composition of the Al alloy was 50:50 (atomic ratio), the pressure of nitrogen gas was 4 Pa (flow rate 1000 ml / min), and the bias voltage was 30 V.

When the number of coarse metal particles is reduced to a predetermined value or less, R
In order to satisfy a '/ Ra <1.0, the above-described precise control of the arc behavior was performed. As a pre-coating step, bombardment treatment with argon ions was performed to further improve the cleanliness of the coating base material. The bombard time was 20 minutes in total. The film was formed for 15 minutes to a thickness of 2.5 μm. (Sample 1)

(Example 2) WC 87 wt% as a substrate,
A cemented carbide having a composition of 13% by weight of Co was used. The WC particle size was 0.3 μm. The top, side, and bottom surfaces of the sintered body were ground with a diamond wheel to obtain the desired shape and dimensions. After processing, wash with acid, alkali, pure water, organic solvent,
Removes dirt such as oil, rust, and stains on the surface.

An arc ion plating apparatus was used to form the coating layer, a Ti-Al alloy was used as the evaporated metal, and nitrogen was used as the raw material gas to produce a composite nitride. Where Ti
The composition of the Al alloy was 50:50 (atomic ratio), the pressure of nitrogen gas was 4 Pa (flow rate 1000 ml / min), and the bias voltage was 30 V.

In order to reduce the number of coarse metal particles to a predetermined value or less,
In addition, precise control of the arc behavior was performed in order to satisfy Ra ′ / Ra <1.0. As a pre-coating step, bombardment treatment with argon ions was performed to further improve the cleanliness of the coating base material. The bombard time was 20 minutes in total. The film was formed for 18 minutes, and the film thickness was 3.0 μm.
And (Sample 2) Samples were prepared based on Examples 1 and 2 in which the evaporated metal and film thickness were changed. In each case, a coating layer was formed in a desired range. (Samples 3 to 8) For comparison, samples in which the number of coarse metal particles on the surface was increased without performing precise control of the arc behavior were produced. A cutting test was performed on each sample under the following conditions. (Samples 9 to 12)

(Cutting condition 1) Work material: Free-cutting stainless steel SUS430F Tool shape: DCGT070202 Cutting speed: 200 to 470 m / min Variable (spindle speed 5000 rpm constant) Feed speed: 0.03 mm / rev Cutting depth: 0.03 mm Cutting time: 45 minutes Cutting fluid: Wet (oil) Cutting was performed up to a maximum of 45 minutes to verify tool wear and cutting edge damage. Table 1 shows the results.

[0029]

[Table 1]

According to Table 1, all of the samples 9 to 12 in which the number of coarse metal particles having a diameter of 1 μm or more is 100 or more in a square of 50 μm without controlling the arc behavior have a large wear amount, and the tool wear amount is large. 1. For samples 1 and 2,
From 5 times to more than 2 times. Above all, Sample 9 experienced abnormal wear, which was predicted to be caused by catastrophic damage.
Sample 12 had a cutting edge defect. The surfaces of these workpieces became cloudy from an early stage and could not be used as products.

On the other hand, it was confirmed that Samples 1 to 8 all exhibited stable cutting performance. For samples 1 to 4, particularly excellent cutting performance,
It exhibited abrasion resistance.

[0032]

As described above in detail, the surface-coated tool according to the first aspect of the present invention is capable of cutting only 100 or less coarse metal particles having a diameter of 1 μm or more on the surface of the coating layer in 50 μm squares. The number of coarse metal particles, which are the starting points of the coating layer destruction on the tool surface, is reduced, whereby the probability of damage to the tool cutting edge and the occurrence of abnormal wear are significantly reduced, and stable cutting performance can be obtained.

In the surface-coated tool according to the second aspect, the arithmetic average roughness of the cemented carbide member before forming the coating layer is Ra.
When the arithmetic average roughness of the coating layer after forming the coating layer is defined as Ra ', Ra and Ra' are Ra '/ Ra.
Since <1.0, it is possible to stabilize the surface accuracy of the workpiece, which is an important factor particularly in precision cutting.

Claims (2)

[Claims] 1. A coating made of a nitride, carbonitride, or oxynitride of Ti or Ti with one or more of Al or any one of metals of the periodic table 4a, 5a, and 6a on the surface of a cemented carbide member. In a surface-coated tool provided with a layer, coarse metal particles having a diameter of 1 μm or more
A surface-coated tool, wherein no more than zero remains. 2. A coating made of a nitride, carbonitride, or oxynitride of Ti or Ti with Al or one or more of the metals in the periodic table 4a, 5a, or 6a on the surface of the cemented carbide member. In the surface-coated tool provided with the layer, the arithmetic average roughness of the cemented carbide member before forming the coating layer is Ra, and the arithmetic average roughness of the coating layer after forming the coating layer is Ra ′. Where Ra and Ra ′ are Ra ′ / R
A surface-coated tool, wherein a <1.0.