JP2000308905A - Covering tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve oxidation resistance even in the case where knife edge temperature becomes high, to improve peeling resistance and chipping resistance even in the case where the knife edge temperature is comparatively low and to improve cutting performance by specifying logical density of a coating. SOLUTION: Logical density of a coating of a covering tool is made more than 75%. Consequently, when applied voltage is made 400 V and voltage is applied in frequency of 20 kHz per second at a ratio of voltage application 50% and no application (0 V) 50%, it becomes possible to improve ion energy without temperature rise of a covering article. It becomes possible to move atoms to transgranular defect and intergranular defect, to extensively reduce defect in the coating and to extensively improve density of the coating as moving distance of ions and atoms due to improvement of ion energy. Consequently, defect in the coating is reduced, density of the coating is improved, diffusion speed of oxygen is extensively lowered, oxidation resistance of the coating is extensively improved, and consequently, extremely long cutting longevity is performed by high speed cutting and high hardness steel cutting for which cutting temperature rises.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated tool exhibiting excellent wear resistance in cutting at an extremely high cutting temperature, such as dry cutting and high-speed cutting of high-hardness steel.

[0002]

2. Description of the Related Art In recent years, TiAlN-based films containing Al have been widely used in place of conventional TiN and TiCN-based films because of their excellent oxidation resistance. Examples of applications based on the effect of the addition of Al include Japanese Patent Publication No. 4-53642 and Japanese Patent Publication No. 5-6770.
There are 5 magnitudes. However, in these cases, the oxidation resistance of the film itself was only slightly improved by adding Al, and at present, it is satisfactory enough for special high-speed, high-efficiency cutting, hardened steel cutting, and dry cutting. No long tool life has been achieved.

[0003]

In the above-mentioned cutting, the cutting temperature of the cutting edge becomes extremely high, and as a result of detailed observation by the present inventors, even though Al is added, oxidation of the film occurs. It was clarified that abrasion progressed due to abrasion and peeling of the oxide film. Therefore, a satisfactory cutting life cannot be achieved under the above-mentioned cutting conditions unless the oxidation resistance of the coating is further improved.

[0004]

The oxidation proceeds by the oxidation of the crystal grains of the film itself and the diffusion of oxygen at the grain boundaries of the crystal grains. The crystal grain boundary has many lattice defects, and the diffusion rate of oxygen here is several tens times the oxygen diffusion rate inside the crystal,
Oxidation of the film becomes faster in proportion to the defect density at the grain boundaries.
Therefore, if the lattice defects at the crystal grain boundaries of the film are eliminated, the oxidation rate is theoretically reduced to one-tenth. Such lattice defects are present not only at the crystal grain boundaries but also within the crystal grains, and make the film density lower than the theoretical value.
Therefore, it is considered that if the density of the film is improved, the oxidation resistance of the film is surely improved.

[0005] On the other hand, the coating by the current physical vapor deposition method has a negative bias on the coating in any of an electron beam method (holo-cathode method), a sputtering method, a magnetron sputtering method, and a cathode arc method as called ion plating. Is applied to electrically accelerate ionized metal ions and nitrogen ions to deposit a substance. In both cases, a DC voltage is used as a bias applied to the coating in common. When a high DC voltage is continuously applied, the temperature of the coating increases, so that the DC voltage is 20 V to 200 V at present.
In general, In such an applied voltage range, the ions deposited on the surface of the coating do not have sufficient energy for surface movement, the movable distance on the surface is limited, and there is a limit in filling the lattice defect. The density of lattice defects at the grain boundaries seems to dominate the density of the coating. When a normal negative bias is applied, the density of the coating film is actually 60% of the theoretical value calculated from the composition.
About 70%.

As a result of various studies, it has been found that a higher density coating can be formed by pulsing the bias applied to the coating and coating with a higher bias. It is presumed that in the film formed in this way, defects in the film crystal grains and defects at crystal grain boundaries are greatly reduced due to the high density. In other words, by applying the bias voltage intermittently, while suppressing the temperature rise of the coating, the energy of the ions deposited on the surface is significantly increased, and the ions can cause lattice defects by increasing the movable distance on the surface. Enables movement to the fill position. That is, the present inventor can reduce the lattice defects inside the crystal and at the crystal grain boundaries and improve the film density by intermittently pulsing the bias applied to the coating material. Is not only excellent in oxidation resistance when the cutting edge temperature is high, but also excellent in peeling resistance and chipping resistance even when the cutting edge temperature is relatively low, and even more excellent cutting performance,
The present inventors have found that they show a wider range of application, and have led to the present invention.

According to the present invention, a nitride of Ti and Al
For a coated tool in which one or more coatings of carbonitride, carbonitride, boride, and carbonitride are coated by ion plating, the density of the coating should be 75% or more of theoretical density Coated tool, or coated Ti
Part or all of Si and C in the range of 1 to 30 atomic%.
A coated tool characterized by being replaced with at least one of r, Mn, Zr, Hf, Nd, Nb, and Y.

[0008]

When the voltage is applied at 400 V and the voltage is applied at a rate of 20 kHz per second at a rate of 50% applied and 50% not applied (0 V), the ion energy can be improved without increasing the temperature of the coating. Becomes By improving the ion energy, the movement distance of ions and atoms becomes longer, atoms can move to intragranular defects and grain boundary defects, and the defects in the film can be greatly reduced and the density of the film can be greatly improved. Become. As described above, by reducing the defects in the coating and increasing the coating density, the diffusion rate of oxygen is greatly reduced, and the oxidation resistance of the coating is greatly increased, resulting in a high cutting temperature and high hardness steel, which increases the cutting temperature. Extremely long cutting life can be achieved in cutting. Lattice defects existing inside the film crystal generate lattice strain and increase the compressive stress remaining in the film. When the compressive stress is increased, the adhesion of the film is deteriorated, and peeling is apt to occur, so that stable cutting cannot be performed and chipping or the like due to minute peeling of the film easily occurs. The pulsing of the bias greatly contributes to the reduction of the residual compressive stress.

Further, by adding a third component such as Si or Y to the TiAl-based film, it is possible to improve the oxidation resistance of the film and further improve the cutting characteristics.
These third components segregate at the grain boundaries of the TiAl-based coating,
Oxidation resistance of the film is improved by further increasing lattice defects at the grain boundaries and further suppressing diffusion of oxygen at the grain boundaries. Si, Cr,
Mn, Zr, Hf, Y, Nb, and Nd were confirmed.

The density of the film was measured by using a supersonic spectromicroscopy. Measurement method is frequency range 40M
Using an ultrasonic sensor of Hz to 140 MHz, the incident angle was variously changed, and the ultrasonic reflectance was measured. The steepest position in the phase curve of the reflectance at each frequency is regarded as the Rayleigh critical angle, the critical angle at each frequency is determined, and the Rayleigh wave velocity is determined according to Snell's law. Using inverse analysis from the dispersion curve of each frequency and Rayleigh wave velocity,
Calculate the elastic properties of the coating. Specifically, it was obtained by an optimization method that minimizes the sum of squares of the residuals between the calculated dispersion curve and the dispersion curve obtained from experiments.

[0011]

EXAMPLES The present invention will be described based on examples. Example 1 Commercially available W with an average particle size of 0.2 to 1.5 microns
The same 1 micron Co powder as the C powder is used and the Co content is 7
The ball end mill of the present invention having a diameter of 10 mm was prepared by mixing in an alcohol for 6 hours with an attritor so as to obtain a wt% and mixing. These end mills were subjected to arc ion plating using a target of Ti (50) Al (50) to form TiAl under a coating film thickness of 2 μm.
N was coated to produce end mills of the present invention and comparative end mills shown in Table 1.

[0012]

[Table 1]

As is evident from Table 1, all the examples of the present invention in which the bias is pulsed have a high density and an extremely small amount of oxide film formed. It is also apparent that the compressive stress remaining in the film is generally low. In Table 1, the coating composition is Ti
The theoretical density was set to 4.61 g / cm3 obtained by calculation, and the ratio to the theoretical density was set to 0.5Al0.5N. The thickness of the oxide film formed when the oxide film was held at 900 ° C. for 1 hour in the atmosphere was measured and indicated together. Using these ball end mills, pocket processing with a diameter of 100 mm and a depth of 5 mm was performed on SKD61 hardness HrC50. Cutting conditions are: spindle speed 10,000 rpm (cutting speed 314 m / min), table feed 2000 mm / m
in (0.1 mm / blade), notch x pitch 0.2 x
0.5 mm, no cutting oil, and overhang 30 mm. The processing was contour line processing, and the amount of wear and the surface roughness were measured with respect to the number of processing pockets. Table 2 shows the results.

[0014]

[Table 2]

In Table 2, the amount of wear was measured by retreating the cutting edge at the tip of a ball end mill. The unit is mm.
The surface roughness was measured in the feed direction, and the Rmax value was adopted. The life was defined as the number of drilled holes until the amount of retreat of the cutting edge was 0.03 or more or chipping occurred. As is clear from Table 2, it is clear that the example of the present invention employing the pulse bias has a small amount of progress of abrasion and a stable cut and finished surface. In this case, the tip of the ball end mill always comes into contact with the work material and becomes high temperature, the coating is worn out by oxidation and the cutting edge retreats.

Incidentally, the result showed the same tendency also in the end mill with the corner R capable of performing the same processing as the ball end mill.

Example 2 In the same manner as in Example 1, various ternary coatings shown in Table 3 were coated by 2 μm, and the same evaluation was performed by the same cutting as in Example 1. The results are also shown in Table 3. Here, in all of the examples of the present invention, a pulse bias was used, and the condition was a 300 V application rate of 80%. On the other hand, in the comparative example, a DC bias was adopted and the bias was set to 100V. The reaction pressure was 3 Pa.

[0018]

[Table 3]

As is evident from Table 3, it is apparent that the ternary end mill of the present invention exhibits more excellent performance. This is considered to be due to the improvement in wear resistance of the film itself accompanying the improvement in oxidation resistance as described above. When the substitution amount is less than 1%, the effect of addition is not recognized, and it is also confirmed that the result is almost the same as that of Example 1 of the invention. Also,
When the addition amount exceeds 30%, the film becomes brittle and chipping occurs at the initial stage, the film hardness is deteriorated, and the result that the wear resistance is significantly impaired is also confirmed.

[0020]

As described above, the coated end mill according to the present invention significantly improves tool characteristics in dry cutting or the like in which the cutting edge is particularly high in temperature. In addition, even when the temperature of the cutting edge is low, there is a remarkable improvement in chipping resistance, peeling resistance, etc. due to the small residual stress of the film, etc.
Therefore, the product of the present invention exhibits excellent performance when applied to a wide range of uses, and can greatly improve productivity. It goes without saying that the effect is the same for not only the ball end mill of the embodiment but also other tools.

Claims (2)

[Claims] 1. A coated tool in which a substrate surface is coated with at least one coating of a nitride of Ti and Al, a carbonitride, a carbonitride, a boronitride, and a carbonitride by an ion plating method. A coated tool, wherein the density of the coating is 75% or more of the theoretical density. 2. The coated tool according to claim 1, wherein a part or all of Ti of said coating is in the range of 1 to 30 atomic%.
A coated tool characterized by being replaced with at least one of i, Cr, Mn, Zr, Hf, Nd, Nb, and Y.