JP5532320B2 - Surface-coated cutting tool and manufacturing method thereof - Google Patents

Description

  The present invention relates to a surface-coated cutting tool, and more particularly, to a surface-coated cutting tool in which a coating is coated on a substrate whose surface has been processed to be uneven.

  In order to improve the wear resistance and surface protection of surface-coated cutting tools, a coating made of a single layer or multiple layers of nitrides such as Ti and TiAl on the surface of a substrate made of WC cemented carbide, cermet, etc. Coating is well known.

  In recent years, work materials such as stainless steel, Inconel, and titanium alloys have become more difficult to cut, and the performance required for tool materials is becoming increasingly severe. In the processing of difficult-to-cut materials, it is necessary not only to improve the heat resistance of the film, but also to firmly adhere the substrate and the film in order to prevent the film from being welded to the material to be peeled off.

For example, Patent Document 1 discloses a technique in which irregularities having a surface roughness R _max of 0.5 μm or more and 30 μm or less are formed on a substrate surface, and a coating film is formed on the substrate on which the irregularities are formed. By forming a film on such a surface, an anchor effect is caused to act between the substrate and the film, thereby improving the adhesion between the substrate and the film.

  Patent Document 2 discloses a technique in which a substantially triangular convex binder phase having an average height of 0.05 μm or more and 0.5 μm or less is formed on the surface of a base material, and a film is formed on the convex binder phase. It is disclosed. By forming the coating in this way, the adhesiveness between the substrate and the coating is improved by bringing the convex binder phase and the coating into close contact.

  Patent Document 3 discloses a technique for suppressing large-scale welding separation that is likely to occur during cutting by including fine crystal grains and coarse crystal grains as crystal grains constituting the film. Patent Document 4 discloses a surface-coated cutting tool in which heat resistance and wear resistance are improved by mixing Si into the coating.

JP 04-280972 A JP 2007-031779 A JP 2008-284636 A JP 08-118106 A

  As shown in Patent Document 2, when a WC cemented carbide is used as a base material, the binder phase contained in the base material only occupies about 10% of the entire surface on the base material surface. For this reason, even if all of the binder phases located on the surface of the base material are ideally bonded to the film, the base material and the film cannot be firmly adhered.

  Moreover, in patent document 3, it is necessary to also make the hard particle | grains which comprise a base material fine according to atomizing the crystal grain which comprises a film. For this reason, the material which comprises a base material will be restrict | limited significantly. In addition, since the coating disclosed in Patent Document 4 contains Si, the compressive residual stress is very high, and the coating is easily peeled off from the substrate.

  In short, attempts to improve the adhesion between the base material and the coating have been studied conventionally, but the base material and the coating are sufficiently resistant to severe cutting conditions such as dry cutting and high feed conditions. Could not be adhered.

  The present invention has been made in view of the current situation as described above, and the object of the present invention is to provide a surface-coated cutting tool that can maintain good adhesion between a substrate and a coating and withstand severe cutting conditions. Is to provide.

The surface-coated cutting tool of the present invention is a surface-coated cutting tool comprising a base material and a coating film formed on the base material, and the base material includes hard particles and a binder phase that binds the hard particles. The hard particles in contact with the coating have irregularities formed on the surface in contact with the coating, and the substrate contacts the coating in a cross section when cut by a plane including the normal to the surface of the surface-coated cutting tool. The surface roughness R _{max at} the reference line of 50 μm in length located on the surface on the side is 1 μm or more and 10 μm or less, and at least one of the recesses constituting the unevenness of the hard particles in the reference line sandwiches the recess The length L of the line segment A connecting the tips of the convex portions at both ends is 10 nm or more and 100 nm or less, and the distance D between the line segment B parallel to the line segment A and in contact with the deepest part of the concave portion is 10 nm or more and 100 nm or less, If the length of the contact line between the hard particles and the coating is S, the contact line includes one or more recessed portions of a predetermined shape, and T is the sum of the lengths L of the recessed portions of the predetermined shape. / S is 0.1 or more.

  It is preferable that the film has a columnar crystal structure, and the width W of the columnar crystal in contact with the recess having a predetermined shape is smaller than the length L of the recess having the predetermined shape. It is preferable that the length L is 10 nm or more and 50 nm or less, the distance D is 10 nm or more and 50 nm or less, and the ratio T / S is 0.1 or more.

  The coating includes one or more first element carbides, nitrides, or carbonitrides selected from the group consisting of Ti, Al, Si, and Cr, and the atomic ratio of Si in the first elements is 20 It is preferably at most atomic%. The atomic ratio of Si in the first element is preferably 3 atomic percent or more and 10 atomic percent or less.

A surface roughness R _max of 1 μm or more and 10 μm or less is formed on a reference line of 50 μm length of the surface of the substrate in a cross section when the surface coated cutting tool is cut in a plane including a normal line to the surface of the surface coated cutting tool A first step, a second step of forming irregularities on the surface of the hard particles located on the surface of the substrate on the side in contact with the coating, and forming a coating on the substrate by physical vapor deposition on the substrate The length L of the line segment A connecting the tips of the convex portions at both ends sandwiching the concave portion in at least one concave portion among the concave portions constituting the concave and convex portions of the hard particles in the reference line is 10 nm. The distance D between the line segment A, which is 100 nm or less, parallel to the line segment A and in contact with the deepest part of the recess, and the line segment A is 10 nm or more and 100 nm or less, and the contact line between the hard particles and the coating The length is S and the contact line Includes one or a plurality of recesses having a predetermined shape, and the ratio T / S is 0.1 or more, where T is the sum of the lengths L of the recesses of the predetermined shape.

  Both the first step and the second step are preferably performed by ion bombardment.

  Since the surface-coated cutting tool of the present invention has the above-described configuration, the surface-coated cutting tool has an excellent effect of maintaining good adhesion between the substrate and the coating film and withstanding severe cutting conditions.

It is a schematic diagram which shows the cross section of the surface vicinity of the side which contact | connects the film of a base material. It is a schematic diagram which shows the cross section of the hard particle located in the surface of the side in contact with the film of a base material. It is a schematic diagram of the film-forming apparatus for producing the surface covering cutting tool of this invention. It is an image when the cross section of the surface vicinity of the side in contact with the film of a base material is observed with SEM. It is an image when the cross section of the hard particle located in the surface of the side in contact with the film of a base material is observed with SEM.

  Hereinafter, the present invention will be described in detail. In the following description of the embodiments, the description is made with reference to the drawings. In the drawings of the present application, the same reference numerals denote the same or corresponding parts. In the present invention, the film thickness is measured by a scanning electron microscope (SEM), and the composition of the film is measured by an energy dispersive x-ray spectrometer (EDS). And

<Surface coated cutting tool>
The surface-coated cutting tool of the present invention comprises a base material and a film formed thereon. The surface-coated cutting tool of the present invention having such a basic configuration is, for example, a drill, an end mill, a milling or turning cutting edge replacement type cutting tip, a metal saw, a gear cutting tool, a reamer, a tap, or a crankshaft pin. It can be used very effectively as a chip for milling.

<Base material>
The base material of the surface-coated cutting tool of the present invention can be used without particular limitation as long as it contains hard particles and a binder phase that binds the hard particles. For example, cemented carbide (for example, WC base cemented carbide, including WC, including Co, or further including carbonitride such as Ti, Ta, Nb, etc.), cermet (TiC, TiN, TiCN, etc.) As a main component), cubic boron nitride sintered bodies, and the like can be given as examples of such a substrate. Among these, from the viewpoint of maintaining good adhesion to the coating, it is preferable to use a WC-based cemented carbide, cermet or the like. When a cemented carbide is used as the base material, the effect of the present invention is exhibited even if such a cemented carbide contains an abnormal phase called free carbon or η phase in the structure.

  In addition, these base materials may have a modified surface. For example, in the case of cemented carbide, a de-β layer may be formed on the surface, and in the case of cermet, a surface hardened layer may be formed, and even if the surface is modified in this way, The effect is shown.

  In this invention, the hard particle which comprises a base material is contained as a main component of a base material, and is contained in order to raise the hardness of a base material. On the other hand, the binder phase is provided to bond the hard particles. When using a substrate made of a cemented carbide, for example, WC, TiC, TiCN or the like is used as the hard particles, and Co, Ni or the like is used as the binder phase. On the other hand, when using a substrate made of cermet, for example, TiC, TiN, TiCN, WC or the like is used as the hard particles, and Co, Ni or the like is used as the binder phase.

  The substrate used in the present invention has macro unevenness formed on the surface thereof, but apart from the unevenness, micro unevenness is formed on the surface of the hard particle positioned on the surface of the substrate. It is characterized by that. In the present invention, the former macro unevenness (surface unevenness of the substrate) is defined by a parameter called surface roughness, and the latter micro unevenness (hard particle surface unevenness) is a line segment connecting the tips of the protrusions sandwiching the recesses. And the parameters of the depth from the line segment to the deepest part of the recess.

  The former macro unevenness contributes to the improvement of the adhesion between the substrate and the film, and the latter micro unevenness contributes to the fineness of the width W of the crystals constituting the film. The base material of the present invention improves the adhesion between the base material and the film so as to be unpredictable by the prior art by providing the surface texture that combines the former macro unevenness and the latter micro unevenness. Thus, a surface-coated cutting tool that can withstand severe cutting conditions can be provided. In the following, the former macro unevenness (surface roughness of the substrate surface) will be described with reference to FIG. 1, and the latter micro unevenness (hard particle surface unevenness) will be described with reference to FIG.

<Roughness of the surface of the substrate>
FIG. 1 is a schematic view showing the vicinity of the surface on the side in contact with the coating film of the substrate, which is a cross-section taken along a plane including the normal to the surface of the surface-coated cutting tool. The substrate of the present invention has a rough surface at a 50 μm long reference line located on the surface in contact with the coating film in a cross section when cut along a plane including the normal to the surface of the surface-coated cutting tool shown in FIG. The degree R _max is 1 μm or more and 10 μm or less. Here, the surface roughness R _max is the difference between the maximum value (maximum height) of the convex portion of the base material within the reference line and the minimum value (minimum height) of the concave portion, and the larger the value, the more uneven the surface. Indicates that the step is rough.

Since the base material having such surface roughness on the surface has a large contact area with the coating film formed thereon, the adhesion with the coating film can be improved. When the surface roughness R _{max at the} reference line is less than 1 μm, the contact area between the substrate and the coating cannot be ensured, and sufficient adhesion cannot be ensured. When the thickness exceeds 10 μm, the unevenness on the surface of the base material affects even the coating film formed thereon, and the work material easily adheres to the coating film and is liable to cause peeling.

The surface roughness R _max of the surface of the substrate is calculated as follows. First, the coating and the substrate are cut along a plane including a normal line to the surface of the coating, and the cross section is mechanically polished. And it observes by 2500 times-5000 times using SEM from the perpendicular | vertical direction with respect to the cross section (FIG. 1 is a schematic diagram of an observation image). In this observation image, the difference between the maximum value of the convex portion and the minimum value of the concave portion within the reference line is the surface roughness R _max .

<Unevenness on hard particle surface>
FIG. 2 is a schematic view showing a cross section of hard particles located on the surface of the base material in contact with the coating. As shown in FIG. 2, the hard particles in contact with the coating have irregularities formed on the surface in contact with the coating, and at least one of the recesses constituting the irregularities of the hard particles in the reference line described above. The length L of the line segment A connecting the tips of the convex parts at both ends sandwiching the concave part is 10 nm or more and 100 nm or less, the line segment B parallel to the line segment A and in contact with the deepest part of the concave part, and the line segment A The distance D is 10 nm or more and 100 nm or less. By forming the concave portion having such a shape, the width of the crystal constituting the coating film formed thereon can be made to be a fine structure of 100 nm or less, and therefore, it is difficult to cause welding peeling and destruction of the coating film. . Both the length L and the distance D are preferably 10 nm or more and 50 nm or less.

  When the length L is less than 10 nm or more than 100 nm, it is difficult to reduce the crystal width of the film, and when the work material is cut, welding peeling or crystal grains constituting the film are liable to occur.

The length L and the distance D indicating the shape of the irregularities formed on the surface of the hard particles in the present invention are calculated as follows. To the cross-section obtained when calculating the surface roughness R _max of the above substrate surface, to obtain an image observed 25,000 times 50000 times using SEM. An arbitrary concave portion that can be observed in such an image is enlarged, a line segment A is drawn by connecting the tips of the convex portions sandwiching the concave portion, and the length L of the line segment A is measured. Then, a distance D between the line segment B and the line segment A that is parallel to the line segment A and in contact with the deepest part of the recess is measured.

  In the present invention, the length of the contact line between the hard particles and the coating is S, and the contact line includes one or a plurality of recesses having a predetermined shape, and the sum of the lengths L of the recesses of the predetermined shape is T Then, the ratio T / S is 0.1 or more. Here, the “contact line” refers to a linear portion where the hard particles and the coating come into contact with each other in a cross section cut along a plane including a normal line to the surface of the surface-coated cutting tool. It shows that the unevenness | corrugation is formed in the surface of the hard particle of the part which a hard particle and a film contact, so that ratio T / S is large.

  Such a contact line length S is directly calculated based on a cross-sectional image of the surface-coated cutting tool. As a method of calculating the ratio T / S, first, in the cross section of the surface-coated cutting tool, the portion occupying the range of the length S with respect to the range where the length S of the contact line between the hard particles and the coating is 1 μm. The number of recesses having a predetermined shape is obtained, and the length L of each recess having a predetermined shape is added to calculate T. In this way, the ratio T / S of the sum T of the lengths of the concave portions of the predetermined shape with respect to the length S of the contact line is calculated. The ratio T / S is more preferably 0.2 or more. On the other hand, when the ratio T / S is less than 0.1, the proportion of fine crystals is low, and it is difficult to obtain an effect of suppressing welding peeling and film breakage.

<Coating>
The coating in the present invention includes a mode in which the entire surface of the substrate is coated, a mode in which the coating is not partially formed, and a part of the layered mode of the coating is partially different. This embodiment is also included. Moreover, it is preferable that the film thickness of this invention is 1 micrometer or more and 10 micrometers or less of the whole film thickness. If it is less than 1 μm, the abrasion resistance may be inferior, and if it exceeds 10 μm, the adhesion to the substrate and the fracture resistance may be reduced. A particularly preferable film thickness of such a coating is 2 μm or more and 5 μm or less. Moreover, the coating film of the present invention is not limited to only one layer, and may be a laminate of two or more layers.

  The coating of the present invention contains one or more carbides, nitrides, or carbonitrides of a first element selected from the group consisting of Ti, Al, Si, and Cr, and an atomic ratio of Si occupying the first element Is preferably 20 atomic% or less. A more preferable atomic ratio of Si is not less than 3 atom% and not more than 10 atom%. When the atomic ratio of Si exceeds 20 atomic%, the compressive residual stress of the film becomes too large, and the film itself is undesirably destroyed. The coating film having such a composition has a columnar crystal structure.

  Conventionally, a film made of TiN or TiAlN not containing Si is likely to have crystal grains having a width of 100 nm or more. However, by containing Si as a constituent component of the film as described above, The width W can be miniaturized, so that heat resistance and wear resistance can be improved.

  In the above film, the width W of the crystal is preferably smaller than the length L of the recess. When the width W of the crystal constituting the coating is smaller than the length L of the concave portion on the surface of the hard particles, the adhesion of the coating to the substrate can be improved, so that the work material is welded and peeled. It is possible to remarkably make it difficult for the particles constituting the particles to fall off. Thereby, since Si was contained, even if the compressive residual stress of a film becomes high, the adhesiveness of a base material and a film becomes difficult to fall. The width W of the crystal refers to the length of the line segment that is the shortest in the vertical direction with respect to the longitudinal direction of the crystal grains constituting the film when the cross section of the film is observed with an SEM.

<Manufacturing method>
As a method for producing the surface-coated cutting tool of the present invention, a reference line having a surface length of 50 μm in the cross section when the surface-coated cutting tool is cut along a plane including a normal line to the surface of the surface-coated cutting tool. A first step of forming a surface roughness R _max of 1 μm or more and 10 μm or less, a second step of forming irregularities on the surface of the hard particles located on the surface of the substrate on the side in contact with the coating, and the substrate On the other hand, the method includes a third step of forming a film on the substrate by a physical vapor deposition method.

  Here, in the first step and the second step described above, as a method of forming irregularities on the surface of the base material and the hard particles, ion bombardment treatment, chemical etching treatment, shot blast treatment, treatment combining these, etc. Can be mentioned. In particular, the ion bombardment process can be performed in the same equipment for the subsequent film formation steps, so each step from the surface treatment of the substrate to the film formation can be performed consistently and productivity is improved. From the viewpoint of

  The coating of the present invention is preferably formed by physical vapor deposition (PVD method). This is indispensable to be a film forming process capable of forming a compound having high crystallinity in order to form the film of the present invention on the surface of the base material. As a result of examining various film forming methods, This is because it has been found that it is optimal to use physical vapor deposition. Physical vapor deposition methods include, for example, sputtering method, ion plating method, etc. Especially when using cathode arc ion plating method with high ion rate of raw material elements, it is necessary to apply to the substrate surface before forming the film. Since metal or gas ion bombardment treatment is possible, there is a merit that the adhesion between the coating and the substrate is remarkably improved. Therefore, the coating film of the present invention is preferably formed by employing a cathode arc ion plating method which is a kind of physical vapor deposition method. Below, each step which produces the surface coating cutting tool of this invention using an arc ion plating apparatus is demonstrated, referring FIG.

  FIG. 3 is a schematic view of a film forming apparatus for producing the surface-coated cutting tool of the present invention. The apparatus shown in FIG. 3 has a chamber 1, a gas inlet 2 for introducing a source gas into the chamber 1, and a gas outlet 3 for exhausting the source gas to the outside. The chamber 1 is connected to a vacuum pump (not shown), and the pressure inside the chamber 1 can be changed through the gas discharge port 3.

  A substrate holder 4 for holding the substrate 5 is provided in the chamber 1, and the substrate holder 4 is electrically connected to the negative electrode of the substrate bias DC power supply 10. On the other hand, the positive electrode of the substrate bias DC power supply 10 is grounded and electrically connected to the chamber 1. Arc-type evaporation sources 6 and 7 are attached to the side wall of the chamber 1. The arc-type evaporation sources 6 and 7 are connected to negative electrodes of DC power sources 8 and 9 that are variable power sources, respectively. , 9 are grounded.

<First step>
First, the base material 5 is set in the base material holder 4, and the first step of ion bombardment also serving as sputter cleaning (bombard) with Ar gas is performed.

In the first step, a surface roughness R _max of 1 μm or more and 10 μm or less is formed on a reference line having a length of 50 μm on the surface of the substrate. The first step maintains a relatively high bias voltage on the substrate 5 at a relatively low pressure of 0.5 Pa or more and 1.5 Pa or less and a pressure of −1200 V or more and −800 V or less with respect to the substrate 5. The ion bombardment treatment is preferably performed.

<Second step>
In the subsequent second step, irregularities are formed on the surface of the hard particles located on the surface in contact with the coating of the substrate. The second step maintains a relatively low bias voltage of −800 V or more and −400 V or less on the substrate with a relatively high pressure of 1.5 Pa or more and 2.5 Pa or less with respect to the substrate 5. The ion bombardment treatment is preferably performed.

<Third step>
After the substrate surface is subjected to ion bombardment as described above, a film is formed on the substrate by physical vapor deposition. First, a target constituting a film is set on the arc evaporation source 7. As the target, various metal simple substances or metal compounds of Ti and Cr can be used.

  When there are two or more metal elements constituting the coating, it is preferable to set a target on the arc evaporation source 6 in addition to the arc evaporation source 7. Although FIG. 3 shows a case where two arc evaporation sources 6 and 7 are provided, it goes without saying that three or more arc evaporation sources may be used.

  After setting the target as described above, a direct current is applied to the arc evaporation sources 6 and 7 and a voltage of about several tens to several hundreds V is applied between the arc evaporation sources 6 and 7 and the chamber 1. As a result, arc discharge is caused between the arc evaporation sources 6 and 7 and the chamber 1. Then, the targets set in the arc evaporation sources 6 and 7 are partially dissolved, and the targets are evaporated from the arc evaporation sources 6 and 7 toward the base material 5. The evaporated target reacts with a source gas such as nitrogen gas to form a film on the substrate.

  Examples of the raw material gas introduced into the chamber 1 when coating the coating include argon gas, nitrogen gas, or oxygen gas, and hydrocarbon gas such as methane, acetylene, and benzene. May be used.

The surface-coated cutting tool produced by the above manufacturing method is a surface-coated cutting tool including a base material and a coating film formed on the base material, and the base material combines the hard particles and the hard particles. In the cross section when the hard particles that are in contact with the coating have a concavo-convex shape on the surface that is in contact with the coating and are cut along a plane that includes the normal to the surface of the surface-coated cutting tool, Has a surface roughness R _max of 1 μm or more and 10 μm or less at a reference line of 50 μm in length located on the surface in contact with the coating, and at least one of the recesses constituting the unevenness of the hard particles in the reference line The length L of the line segment A connecting the tips of the convex parts at both ends sandwiching the concave part is 10 nm or more and 100 nm or less, the line segment B parallel to the line segment A and in contact with the deepest part of the concave part, and the line segment A The distance D to the is 10 nm or more The length of the contact line between the hard particles and the coating is S, and the contact line includes one or a plurality of concave portions of a predetermined shape. The sum of the lengths L of the concave portions of the predetermined shape is T Then, the ratio T / S is 0.1 or more.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
As the base material of the surface-coated cutting tool of this example, a material made of cemented carbide of ISO P30 grade and having a shape of SFKN12T3AZTN was used. The cemented carbide constituting the substrate contains WC as hard particles and is formed by bonding the hard particles with a binder phase made of Co. FIG. 3 is a schematic view of a film forming apparatus used for producing the surface-coated cutting tool of this example.

While setting the said base material to the base material holder 4 of the film-forming apparatus of FIG. 3, Ti was set to the target material of the arc type evaporation source 7. FIG. And vacuuming was performed by the vacuum pump until the pressure inside the chamber 1 became 1.0 × 10 ⁻³ Pa. At the same time, the temperature in the chamber was raised to 450 ° C. by a heater (not shown) in the chamber.

Then, as a first step, Ar gas is introduced to maintain the internal pressure of the chamber 1 at 1.0 Pa, and the DC bias voltage is gradually increased from the DC power supply 9 to be maintained at −1200 V. For a minute. In this way, the surface of the substrate was made to have a surface roughness R _max of 9.4 μm.

  Next, as a second step, argon gas was introduced from the gas inlet 2 so that the pressure in the chamber became 2.0 Pa, the DC bias voltage was maintained at −600 V, and ion bombardment was performed for 30 minutes. . In this way, irregularities were formed on the surface of the hard particles located on the substrate surface.

  Thereafter, nitrogen gas is introduced from the gas inlet 2 so that the pressure in the chamber becomes 3.0 Pa, and a current of 100 A is supplied from the DC power source 9 to the arc evaporation source 7 to Ti ions were evaporated in the direction. And while supplying electric current to the arc type evaporation source 7, nitrogen gas was introduced from the gas inlet 2, the voltage of the base-material bias DC power supply 10 was set to 60V, and the voltage was kept constant. By reacting Ti ions and nitrogen gas on the surface of the base material 5, a film made of TiN having a thickness of 3 μm was formed on the base material. As described above, the surface-coated cutting tool of this example was produced.

<Examples 2-7 and Comparative Examples 1-6>
The surface-coated cutting tools of Examples 2 to 7 and Comparative Examples 1 to 6 are the same as the surface-coated cutting tool of Example 1 with respect to the conditions of the first step and the second step of ion bombardment treatment, and the target material for forming the coating film. However, as shown in the “Composition” column of “First Step”, “Second Step”, and “Coating” in Table 1, they were prepared in the same manner as in Example 1. In Comparative Examples 1, 2, and 6, the second step was not performed. In addition, as in Example 6, when there were many metal elements constituting the film, the target material was set in both the arc evaporation sources 6 and 7 in FIG.

  In order to obtain a coating film having a target composition, various source gases were introduced from the gas inlet 2 for supplying the source gas to the chamber 1 via a mass flow controller (not shown).

<Surface analysis of substrate>
In the surface-coated cutting tool of Example 1 produced as described above, the coating and the substrate were cut along a plane including the normal to the surface of the coating, and the cross section was mechanically polished. And it observed by 25000 times using SEM from the perpendicular | vertical direction with respect to the cross section. The image which observed the cross section of the surface coating cutting tool of Example 1 with SEM is shown in FIG.

FIG. 4 is an image when a cross section in the vicinity of the surface on the side in contact with the coating of the substrate is observed with an SEM. In the cross section shown in FIG. 4, the difference between the maximum value and the minimum value on the reference line having a length of 50 μm was defined as the surface roughness R _max . In a similar manner at five different reference lines was measured surface roughness R _max, exhibited an average of the measured values of the five surface roughness R _max in the column of the surface roughness R _max in Table 1.

  Next, the same cross section was observed at 25000 times using SEM. FIG. 5 is an image obtained by observing a cross section of the hard particles located on the surface on the side in contact with the coating of the base material with an SEM. Note that FIG. 5 shows one of the recesses. Obtain the length L of the line segment A connecting the tips of the convex portions sandwiching the concave portions in any five concave portions of the concave portions constituting the irregularities on the surface of the hard particles located on the surface of the substrate. The average value was calculated and shown in the “Length L” column of Table 1. Further, a line segment B parallel to the line segment A and in contact with the deepest part of the concave portion is drawn, a distance D between the line segment A and the line segment B is obtained, and an average value of the five points is calculated. D ”column.

  The width W of the crystal grains constituting the coating is the line segment that is perpendicular and shortest to the longitudinal direction of the crystal grains that can be distinguished by observing the cross section in an image obtained by observing the same cross section at 25,000 times using an SEM. The length was calculated, and the average value of the five measurements was shown in the “Crystal width W” column of Table 1.

  In the cross section of the surface-coated cutting tool of each of the above embodiments, the number of concave portions having a predetermined shape in a range in which the length S of the contact line between the hard particles and the coating occupies 1 μm is calculated, and the concave portions having the predetermined shapes are calculated. T / S was calculated by adding the length L. The measurement was made five times in the same manner, and the average value was shown in the column of “Ratio T / S” in Table 1.

From the results of the above analysis, the surface-coated cutting tool produced in each example is a surface-coated cutting tool including a base material and a film formed on the base material, and the base material is a hard particle When the hard particles in contact with the coating have a concavo-convex surface formed on the surface in contact with the coating and are cut at a plane including the normal to the surface of the surface-coated cutting tool In the cross section, the substrate has a surface roughness R _max of 1 μm or more and 10 μm or less at a reference line of 50 μm in length located on the surface on the side in contact with the coating, The length L of the line segment A connecting the tips of the convex portions at both ends sandwiching the concave portion is at least 10 nm and not more than 100 nm in at least one concave portion, and is a line segment parallel to the line segment A and in contact with the deepest portion of the concave portion The distance D between B and the line segment A is 10 nm or more and 100 nm or less, the length of the contact line between the hard particles and the coating is S, and the contact line includes one or a plurality of recesses of a predetermined shape, and the sum of the lengths L of the recesses of the predetermined shape When T is T, the ratio T / S was confirmed to be 0.1 or more.

<Evaluation of tool life>
The life of the tool was evaluated by performing a dry intermittent cutting test on each of the surface-coated cutting tools of each Example and Comparative Example prepared above. The intermittent cutting process was performed using SUS304 as a work material, with a cutting speed of 120 m / min, a feed rate of 0.2 mm / blade, and a cutting depth of 2.0 mm until the surface of the base material was exposed. It was. Table 2 below shows the cutting lengths cut until the substrate is exposed. Note that the longer the cutting length, the longer the tool life.

  As is clear from Table 2, it is clear that the surface-coated cutting tool according to the present invention in each example improves the tool life as compared with the surface-coated cutting tool in each comparative example. This is considered to be due to the improved adhesion between the substrate and the coating. From the above, it was confirmed that the tool life of the surface-coated cutting tool can be improved according to the present invention.

  Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 chamber, 2 gas introduction port, 3 gas exhaust port, 4 base material holder, 5 base material, 6,7 arc evaporation source, 8,9 DC power supply, 10 substrate bias power supply.

Claims (6)

A method for producing a surface-coated cutting tool comprising a substrate and a coating formed on the substrate,
In the reference line length 50μm on the surface of the substrate in a cross section obtained by cutting the surface-coated cutting tool with a plane including the normal to the surface of the surface-coated cutting tool, 1 [mu] m or more 10μm or less of the surface roughness R _max A first step of forming
A second step of forming irregularities on the surface of the hard particles located on the surface of the substrate on the side in contact with the coating;
To said substrate, wherein the physical vapor deposition and a third step of forming said coating on said substrate,
The length L of the line segment A connecting the tips of the convex portions at both ends sandwiching the concave portion in at least one concave portion among the concave portions constituting the concave and convex portions of the hard particles in the reference line is 10 nm or more and 100 nm or less. The distance D between the line segment A parallel to the line segment A and in contact with the deepest part of the recess and the line segment A is 10 nm or more and 100 nm or less,
If the length of the contact line between the hard particles and the coating is S, the contact line includes one or more recessed portions of a predetermined shape, and T is the sum of the lengths L of the recessed portions of the predetermined shape. , the ratio T / S is state, and are 0.1 or more,
The method for manufacturing a surface-coated cutting tool, wherein the first step and the second step are both performed by ion bombardment . A surface-coated cutting tool manufactured by the method for manufacturing a surface-coated cutting tool according to claim 1,
E Bei a base material and a coating formed on the substrate,
The substrate includes hard particles and a binder phase that binds the hard particles;
The hard particles in contact with the coating have irregularities formed on the surface in contact with the coating,
In the cross section when cut along a plane including the normal to the surface of the surface-coated cutting tool, the substrate has a surface roughness R _max of 1 μm at a 50 μm long reference line located on the surface in contact with the coating. 10 μm or less,
The length L of the line segment A connecting the tips of the convex portions at both ends sandwiching the concave portion in at least one concave portion among the concave portions constituting the concave and convex portions of the hard particles in the reference line is 10 nm or more and 100 nm or less. A distance D between the line segment B parallel to the line segment A and in contact with the deepest part of the recess and the line segment A is 10 nm or more and 100 nm or less,
If the length of the contact line between the hard particles and the coating is S, the contact line includes one or more recessed portions of a predetermined shape, and T is the sum of the lengths L of the recessed portions of the predetermined shape. The surface-coated cutting tool having a ratio T / S of 0.1 or more. The coating consists of a columnar crystal structure,
3. The surface-coated cutting tool according to claim 2 , wherein a width W of a columnar crystal of the coating in contact with the recess having the predetermined shape is smaller than a length L of the recess having the predetermined shape. The surface-coated cutting according to claim 2 or 3 , wherein the length L is not less than 10 nm and not more than 50 nm, the distance D is not less than 10 nm and not more than 50 nm, and the ratio T / S is not less than 0.1. tool. The coating includes a carbide, nitride, or carbonitride of one or more first elements selected from the group consisting of Ti, Al, Si, and Cr,
The surface-coated cutting tool according to any one of claims 2 to 4 , wherein an atomic ratio of Si in the first element is 20 atomic% or less. The surface-coated cutting tool according to claim 5 , wherein an atomic ratio of Si occupying the first element is 3 atomic% or more and 10 atomic% or less.