JP5286626B2 - 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 having different surface roughnesses on a rake face side surface and a flank face side surface.

  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.

  Recent trends in cutting tools include the need for dry machining that does not require cutting fluids from the viewpoint of protecting the global environment, and the fact that cutting speeds have become faster in order to further improve machining efficiency. The performance required for tool materials is becoming increasingly severe. Particularly in the processing of cast iron and alloy tool steel, 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 film peeling due to adhesion.

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 the substrate having such an uneven 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 forming a smooth shape with a surface roughness R _max of 0.2 μm or less. Patent Document 4 discloses a technique for suppressing large-scale adhesion separation that is likely to occur during cutting by including fine crystal grains and coarse crystal grains as crystal grains constituting the coating. Further, Patent Document 5 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 Japanese Patent Publication No. 07-0773802 JP 2008-284636 A JP 08-118106 A

As shown in Patent Document 1, when unevenness having a surface roughness R _max of 5 μm or more is formed on the rake face of the base material surface, the surface of the base material is also formed on the surface of the coating film formed thereon. Since the same unevenness is reflected, the surface of the surface-coated cutting tool has the same surface roughness as the surface of the substrate. For this reason, contact resistance at the time of chip discharge | emission increases with the unevenness | corrugation of a tool surface, and adhesion will be accelerated | stimulated, Therefore Adhesion peeling could not be suppressed.

  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.

  In Patent Document 3, since the cutting edge becomes very hot when cutting at high speed, adhesion is likely to occur, and adhesion peeling cannot be suppressed. Moreover, in patent document 4, 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. Further, since the coating disclosed in Patent Document 5 contains Si, the compressive residual stress is very high, and the coating is easily peeled off from the substrate.

  In short, attempts to suppress the adhesion of the work material during cutting and to improve the adhesion between the base material and the coating have been studied in the past, but severe conditions such as dry cutting and high cutting speed have been studied. The substrate and the coating could not be brought into close contact with each other to withstand various cutting conditions.

  The present invention has been made in view of the above-described situation, and the object of the present invention is to provide surface-coated cutting that maintains good adhesion between the base material and the coating and that the work material is less likely to adhere. Is to provide a tool.

  The surface-coated cutting tool of the present invention comprises a base material and a coating 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 in the cross section when the surface-coated cutting tool is cut along a plane including the normal to the rake face of the surface-coated cutting tool, The surface on the flank side has a surface roughness Rz, n of 1 μm or more and 30 μm or less at the flank side reference line of 50 μm in length located on the surface, and the surface on the rake face side of the substrate is located on the surface The surface roughness Rz, s at the rake face side reference line with a length of 50 μm is 0.5 μm or more and 5 μm or less, and Rz, n is larger than Rz, s. Among the recesses that constitute the at least one recess, the recess The length Ln of the line segment An connecting the tips of the convex portions at both ends sandwiching the line segment is 0.1 μm or more and 0.8 μm or less, the line segment Bn parallel to the line segment An and in contact with the deepest part of the recess, The distance Dn to An is 0.1 μm or more and 0.8 μm or less, and at least one of the concave portions constituting the concave and convex portions of the hard particles on the rake face side reference line, the convex portions at both ends sandwiching the concave portion The length Ls of the line segment As that connects the tips of the line segments is 0.05 μm or more and 0.5 μm or less, and the distance Ds between the line segment Bs parallel to the line segment As and in contact with the deepest part of the concave portion and the line segment As is 0.05 μm or more and 0.5 μm or less, Ln is larger than Ls, and the length of the contact line between the hard particles on the flank side and the coating is Sn, and the contact line has one or more concave portions. And the ratio Tn / Sn is 0.1 or more, where Tn is the sum of the respective lengths Ln of the recesses, When the length of the contact line between the hard particle on the rake face side and the coating is Ss, the contact line includes one or more recesses, and the sum of the lengths Ls of the recesses is Ts, the ratio Ts / Ss is 0.1 or more.

  The above-mentioned film has a columnar crystal structure, and the width Wn of the columnar crystal of the film in contact with the recess on the flank side is smaller than Ln and the columnar crystal of the film in contact with the recess on the rake face side. The width Ws is preferably smaller than Ls. It is preferable that the length Ln and the distance Dn are 0.1 μm or more and 0.5 μm or less, and the length Ls and the distance Ds are 0.05 μm or more and 0.3 μm or less.

  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. The base material is a material whose surface is treated after sintering the hard particles and the binder phase. When the surface roughness of the surface of the base material before the surface treatment is Rz, Rz, n is , Larger than Rz.

  The present invention relates to a method of manufacturing a surface-coated cutting tool, and the method of manufacturing the surface-coated cutting tool is based on a cross section when the surface-coated cutting tool is cut along a plane including a normal to the rake face of the surface-coated cutting tool. A first step of forming a surface roughness Rz, n of 1 μm or more and 30 μm or less on a flank side reference line having a length of 50 μm located on the flank side surface of the material, and the surface of the rake face of the substrate in the cross section A second step of forming a surface roughness Rz, s of 0.5 μm or more and 5 μm or less on a rake face side reference line having a length of 50 μm, and hard particles located on the surface of the substrate on the side in contact with the coating The method includes a third step of forming irregularities and a fourth step of forming a film on the substrate by physical vapor deposition.

  The first step is preferably performed by blasting or laser processing. Both the second step and the third step are preferably performed by ion bombardment.

  Since the surface-coated cutting tool of the present invention has the above-described configuration, the adhesion between the base material and the coating film is kept good, and the work material is less likely to adhere to the base material.

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 near the flank on the side in contact with the coating of the substrate is observed with an 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 replaceable cutting tip, a metal saw, a 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 improving the adhesion between the substrate and the film, and the latter micro unevenness contributes to the fineness of the widths Ws and Wn of the crystals constituting the film. The base material of the present invention is provided with a surface property in which the former macro unevenness and the latter micro unevenness are combined, so that the effects obtained by each of these unevenness are combined, and can be predicted in the prior art. Thus, it is possible to provide a surface-coated cutting tool that can improve the adhesion between the substrate and the coating film as much as possible, and can withstand severe cutting conditions.

  Moreover, the macro unevenness formed on the flank side surface of the base material is rougher than the macro unevenness formed on the rake surface side surface of the base material, and is formed on the surface of the hard particles on the flank side. The micro unevenness is rougher than the micro unevenness formed on the surface on the rake face side of the substrate. By roughening the surface unevenness of the base material on the flank side in this way, while improving the adhesion between the base material and the coating, it is formed on the base material by making the surface unevenness on the rake face side fine. The surface of the coating film is smoothed to make it difficult to adhere the work material. 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. 1 and 2 both show the surface on the flank side of the substrate, but the surface on the rake surface side of the substrate is the same except that the roughness of the unevenness is different.

<Roughness of substrate surface>
FIG. 1 is a cross-sectional view of the surface-coated cutting tool taken along a plane including a normal line to the rake face, and is a schematic view showing the vicinity of the flank on the side in contact with the coating film of the substrate. In the cross section when the base material of the present invention is cut along a plane including the normal to the rake face of the surface-coated cutting tool shown in FIG. 1, the surface on the flank side of the base material is the length located on the surface. The surface roughness Rz, n at the 50 μm flank reference line is 1 μm or more and 30 μm or less. Here, the surface roughness Rz, n 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. Indicates that the step is rough.

  Since the base material having such a flank surface roughness has a large contact area with the coating film formed thereon, the adhesion to the coating film can be improved. If the surface roughness Rz, n on the flank side reference line is less than 1 μm, the contact area between the substrate and the coating cannot be secured, and sufficient adhesion cannot be secured. On the other hand, when the thickness exceeds 30 μm, the unevenness of the surface of the base material affects even the coating film formed thereon, so that the work material easily adheres to the coating film and easily causes adhesive peeling.

  Although not shown, in the cross section when cut along a plane including the normal line to the rake face of the surface-coated cutting tool, the rake face side surface of the substrate is a rake face side reference line having a length of 50 μm located on the surface. The surface roughness Rz, s is characterized by being 0.5 μm or more and 5 μm or less. Since the surface of the coating film formed on the base material having such a rake face roughness can be formed smoothly, the occurrence of adhesion peeling can be suppressed. When the surface roughness Rz, s at the rake face side reference line is less than 0.5 μm, the contact area between the substrate and the coating cannot be secured, and sufficient adhesion cannot be secured. . On the other hand, if it exceeds 5 μm, the surface roughness of the base material affects the surface roughness of the surface of the coating film formed on the base material, so that adhesion peeling is likely to occur.

  For the reasons described above, the base material of the present invention is characterized in that the surface roughness Rz, n of the base material on the flank side is larger than the surface roughness Rz, s of the base material on the rake face side. . That is, the flank side of the substrate is roughened to improve the adhesion with the coating, and the rake side of the substrate is to improve the smoothness of the coating surface formed thereon, The surface roughness is reduced. Thereby, it can be set as the surface covering cutting tool with high adhesiveness of a base material and a film, and being hard to adhere a work material.

  The surface roughness Rz, n on the flank side and the surface roughness Rz, s on the rake face side of the substrate are calculated as follows. First, the coating and the substrate are cut along a plane including a normal line to the rake face 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 of the base material within the flank side reference line and the minimum value of the concave portion is the surface roughness Rz, n, and the convex portion of the base material within the rake face side reference line The difference between the maximum value and the minimum value of the recess is the surface roughness Rz, s.

  In the present invention, the surface of the base material is treated after sintering the hard particles and the binder phase, and the surface roughness of the surface of the base material before the surface treatment is Rz. , Rz, n is preferably larger than Rz. Here, after sintering the hard particles and the binder phase, the surface of the base material before processing the surface of the base material is referred to as “sintered skin”. The surface roughness Rz of the sintered skin measured based on the above measurement method is usually 1 μm or more and 3 μm or less, but a conventional surface-coated cutting tool in which a film is formed on the surface of the base material of the sintered skin. Could not sufficiently suppress adhesion peeling. In the present invention, in order to overcome such problems of the prior art, the surface roughness Rz, n of the flank is preferably 3 μm or more.

<Unevenness on hard particle surface>
FIG. 2 is a schematic view showing a cross section of hard particles located on the flank side surface in contact with the coating on the substrate. 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 on the flank side reference line described above. In one recess, the length Ln of the line segment An connecting the tips of the convex portions at both ends sandwiching the recess is not less than 0.1 μm and not more than 0.8 μm, and is parallel to the line segment An and touches the deepest part of the recess The distance Dn between the segment Bn and the line segment An is 0.1 μm or more and 0.8 μm or less. On the other hand, the length Ls of the line segment As 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 on the rake face side reference line is 0. The distance Ds between the line segment As and the line segment Bs that is 05 μm or more and 0.5 μm or less, parallel to the line segment As and in contact with the deepest part of the recess is 0.05 μm or more and 0.5 μm or less, and Ln is , Ls. By forming the concave portion having such a shape on the surface of the hard particle, the width Wn of the crystal constituting the film formed thereon is made smaller than Ln, so that the wear on the flank is reduced on the flank. Can be made. In addition, the width Ws of the columnar crystals of the coating in contact with the recess on the rake face side can be made smaller than Ls, so that the adhesion peeling and the destruction of the coating are hardly caused.

  In the present invention, Ln in at least one concave portion satisfies the above numerical range, and the concave portion having Ln that satisfies the numerical range is half the unevenness included in the flank reference line. It is preferable that it is the above, and more preferably, all of the unevenness included in the flank reference line. Similarly, Ls is preferably at least half of the unevenness included in the rake face side reference line, and more preferably all of the unevenness included in the rake face side reference line.

  In the flank of the substrate, the length Ln and the distance Dn are both 0.1 μm or more and 0.5 μm or less, and in the rake surface of the substrate, the length Ls and the distance Ds are both 0. It is preferable that the thickness is 0.05 μm or more and 0.3 μm or less. By setting it as the surface of such a hard particle, the improvement effect of adhesion peeling and the destruction prevention effect of a film can be heightened.

  When the length Ln is less than 0.1 μm or more than 0.8 μm, adhesion peeling or dropout of crystal grains constituting the film tends to occur when the work material is cut. On the other hand, when the length Ls is less than 0.05 μm or exceeds 0.5 μm, the widths Wn and Ws of the crystals constituting the film are difficult to be miniaturized, and the quality of the processed surface tends to be lowered.

  The length Ln and the distance Dn indicating the shape of the irregularities formed on the surface of the hard particles on the flank side in the present invention are calculated as follows. With respect to the cross section obtained when calculating the surface roughness Rz, n of the above-described base material surface, an image observed at 25000 times to 50000 times using SEM is obtained. An arbitrary concave portion that can be observed in such an image is enlarged, the tip of the convex portion sandwiching the concave portion is connected, a line segment An is drawn, and the length Ln of the line segment An is measured. Then, a distance Dn between the line segment Bn parallel to the line segment An and in contact with the deepest part of the recess and the line segment An is measured. In the same manner as described above, Ls and distance Ds indicating the shape of the irregularities formed on the surface of the hard particle on the rake face side are measured.

  In the present invention, the length of the contact line between the flank hard particle and the coating is Sn, and the contact line includes one or a plurality of recesses, and the sum of the lengths Ln of the recesses is defined as Tn. Then, the ratio Tn / Sn is 0.1 or more, and the length of the contact line between the hard particle on the rake face side and the coating is Ss, and the contact line includes one or more recesses, When the sum of the lengths Ls of the recesses is Ts, the ratio Ts / Ss is 0.1 or more. Here, the “contact line” means that the interface part where the hard particles and the coating come into contact with each other in a cross section when the surface-coated cutting tool is cut along a plane including the normal to the rake face of the surface-coated cutting tool is linear. Say what you represent. 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 Tn / Sn and ratio Tn / Sn are large.

  Such contact line lengths Sn and Ss are directly calculated based on a cross-sectional image of the surface-coated cutting tool. As a method of calculating the ratio Tn / Sn, first, in the cross section of the surface-coated cutting tool, the range Sn of the contact line length Sn between the flank hard particles and the coating is 1 μm. Tn is calculated by adding the lengths Ln of the respective recesses. In this way, the ratio Tn / Sn of the sum Tn of the lengths of the recesses with respect to the length Sn of the contact line is calculated. The calculation method of the ratio Ts / Ss is calculated by paying attention to the contact surface between the hard particles on the rake face side and the coating, similarly to the calculation method of Tn / Sn. The ratios Tn / Sn and Ts / Ss are more preferably 0.2 or more. On the other hand, if either one of the ratios Tn / Sn or Ts / Ss is less than 0.1, the proportion of fine crystals decreases, and it is difficult to obtain the effect of suppressing adhesion peeling and film breakage, which is not preferable. .

<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. 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 with a width of 0.1 μm or more. However, as described above, the film is formed by containing Si as a component of the film. The crystal widths Wn and Ws can be miniaturized, thereby improving the heat resistance and wear resistance. From the viewpoint of making it difficult for self-destruction to occur in addition to heat resistance and wear resistance, the atomic ratio of Si is more preferably 3 atomic percent or more and 10 atomic percent or less.

  In the above-described coating, the columnar crystal width Wn of the coating in contact with the recess on the flank side is smaller than Ln, and the columnar crystal width Ws of the coating in contact with the rake side recess is smaller than Ls. It is preferable. As a result, the adhesion of the film to the substrate can be improved, so that it is possible to remarkably hardly cause the adhesion peeling of the work material and the dropping of the particles constituting the film. 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 widths Ws and Wn of the crystals are the lengths of the line segments that are 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. To do.

<Manufacturing method>
As a method for producing the surface-coated cutting tool of the present invention, the surface-coated cutting tool is positioned on the flank side surface of the substrate in a cross section when the surface-coated cutting tool is cut along a plane including a normal line to the rake face of the surface-coated cutting tool. A first step of forming a surface roughness Rz, n of 1 μm or more and 30 μm or less on a flank side reference line having a length of 50 μm, and a length of 50 μm located on the rake face side surface of the substrate in the cut surface On the rake face side reference line, a second step for forming a surface roughness Rz, s of 0.5 μm or more and 5 μm or less and irregularities are formed on the surface of the hard particles located on the surface of the base material in contact with the coating. It includes a third step and a fourth step of forming a film on the substrate by physical vapor deposition.

  Here, in the first step to the third step, as a method for forming irregularities on the surface of the base material and the hard particles, ion bombardment treatment, chemical etching treatment, blast treatment, laser treatment, and a combination thereof are used. And the like.

  Among these, the first step preferably uses blasting, laser processing, or chemical etching. This is because these surface treatments can easily form a relatively large surface roughness on the surface of the substrate. Moreover, it is preferable to use an ion bombardment process for the second step and the third step. In ion bombardment, after the surface of the substrate is treated, the film can be formed in the same apparatus, and thus the steps from the surface treatment of the substrate to the film formation are consistent. This is because it can be performed and is excellent in productivity.

  The “blast treatment” in the present invention is any processing method as long as it is a method capable of injecting abrasive grains at a predetermined injection speed and injection pressure onto the surface of a substrate to be processed. For example, a fluid processing method such as dry blasting or wet blasting in which abrasive grains are sprayed using a compressed fluid such as compressed air, and a centrifugal force is applied to abrasive grains by rotating an impeller. A centrifugal type (impeller type), a flat type type in which abrasive grains are struck and ejected using a launching rotor, or the like can be used.

  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>
In the first step, a surface roughness Rz, n of 1 μm or more and 30 μm or less is formed on a flank reference line having a length of 50 μm located on the flank side surface of the substrate. In the first step, it is preferable to perform shot blasting on the flank only on the base material 5.

<Second step>
Next, the base material 5 is set in the base material holder 4, and ion bombardment which also serves as sputter cleaning (bombard) with Ar gas is performed. In the second step, a surface roughness Rz, s of 0.5 μm or more and 5 μm or less is formed on the rake face side reference line having a length of 50 μm on the rake face surface of the substrate. The second 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 −1000 V or more and −600 V or less with respect to the substrate 5. The ion bombardment treatment is preferably performed.

<Third step>
In the subsequent third step, irregularities are formed on the surface of the hard particles located on the surface in contact with the coating on the substrate. The third step maintains a relatively low bias voltage of −600 V or more and −300 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.

<4th 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. By the manufacturing method including the above steps, the surface-coated cutting tool of the present invention can be manufactured.

  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, the material is a cemented carbide of ISO P30 grade and the shape is SFKN12T3AZTN. 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 for producing the surface-coated cutting tool of the present invention. First, as a first step, a dry blast was projected for 30 seconds at a projection distance of 100 mm and a projection pressure of 1.25 MPa on the flank face of the substrate. This roughened only the flank of the substrate. In this way, the surface roughness Rz, n of the surface on the flank side of the substrate was set to 1.3 μm.

Next, the substrate was set on the substrate holder 4 of the film forming apparatus of FIG. 3 and Ti was set on the target material of the arc evaporation source 7. 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 second 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 source 9 to be maintained at −700 V, and the ion bombarding process is performed. For a minute. In this way, the surface roughness Rz, s of the surface on the rake face side of the substrate was set to 1.2 μm.

  Next, as a third 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 −500 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 surface of the substrate.

  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. Then, as a fourth step, current was supplied to the arc evaporation source 7 and nitrogen gas was introduced from the gas inlet 2. Then, the voltage of the substrate bias DC power supply 10 was set to 60 V, and the voltage was kept constant. Thereby, Ti ions and nitrogen gas were reacted on the surface of the base material 5 to form a film made of TiN having a thickness of 3 μm on the base material. As described above, the surface-coated cutting tool of this example was produced.

<Examples 2-8 and Comparative Examples 1-8>
The surface-coated cutting tools of Examples 2 to 8 and Comparative Examples 1 to 8 are different from the surface-coated cutting tool of Example 1 in that the conditions of the second step and the third step of ion bombardment treatment are “second” in Table 1. It was produced by the same method as in Example 1 except that the target material for forming the film was different as shown in the “Coating” column of Table 1 as shown in “Step” and “Third Step”. In Comparative Examples 1 to 4, the third step was not performed. In addition, as in Example 8, when there were many metal elements constituting the film, the target material was set in both of the arc evaporation sources in FIG.

  In order to obtain a coating film having a target composition, various source gases were introduced from a gas inlet 2 for supplying 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 rake face 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 flank on the side in contact with the coating on 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 of 50 μm in length is the surface roughness, in particular the surface roughness of the flank is Rz, n, and the surface roughness of the rake face is Rz, s. The surface roughness Rz, n and Rz, s were measured in the same way using five different reference lines, and the average of the measured values of the surface roughness Rz, n and Rz, s for each of the five times was measured as shown in Table 1. Shown in the Rz, n and Rz, s columns.

  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 flank side surface on the side in contact with the coating film of the base material with an SEM. Note that FIG. 5 shows one of the recesses. The length Ln of the line segment An connecting the tips of the convex portions sandwiching the concave portions is obtained in any of the concave portions constituting the concave and convex portions of the surface of the hard particles located on the flank side surface of the substrate. The average value of the five points was calculated and shown in the “Length Ln” column of Table 1. In addition, a line segment Bn parallel to the line segment An and in contact with the deepest part of the recess is drawn, a distance Dn between the line segment An and the line segment Bn is obtained, and an average value of the five points is calculated. Dn "column. In the same manner as the above-described concavo-convex observation of the flank side, the concavo-convex of the surface of the hard particles located on the surface of the rake face side of the substrate is observed, and the length Ls and the distance Ds of the line segment As are calculated. Of “length Ln” and “distance Dn”.

  The widths Ws and Wn of the crystal grains constituting the coating are the lines that are 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 of the minute was calculated, and the average value of the five measurements was shown in the columns of “Crystal width Wn” and “Crystal width Ws” in Table 1.

  In the cross section of the surface-coated cutting tool of each of the above embodiments, the number of recesses in the range where the length Sn of the contact line between the hard particles on the flank side and the coating occupies 1 μm is calculated, and the length of each recess Tn / Sn was calculated by adding Ln. The measurement was made five times in the same manner, and the average value was shown in the column of “Tn / Sn” in Table 1. In the same manner, Ts / Ss was calculated based on the contact surface between the hard particle on the rake face side and the coating, and the result is shown in the column of “Ts / Ss” in Table 1.

  From the results of the above analysis, the surface-coated cutting tool produced in each example includes a base material and a coating film formed on the base material, and the base material includes hard particles and the The hard particles that are in contact with the coating and have a binder phase that binds the hard particles have irregularities formed on the surface in contact with the coating, and the surface-coated cutting tool is a plane that includes the normal to the rake face of the surface-coated cutting tool. In the cross section when cutting the surface, the surface on the flank side of the substrate has a surface roughness Rz, n of 1 μm or more and 30 μm or less at the flank side reference line with a length of 50 μm located on the surface in contact with the coating. The surface on the rake face side of the substrate has a surface roughness Rz, s of 0.5 μm or more and 5 μm or less at a rake face side reference line of 50 μm in length located on the surface in contact with the coating, and Rz, n Is larger than Rz, s, and the concave of hard particles on the flank reference line In at least one of the recesses constituting the length Ln, the length Ln of the line segment An connecting the tips of the convex portions at both ends sandwiching the recess is 0.1 μm or more and 0.8 μm or less, and is parallel to the line segment An. The distance Dn between the line segment Bn in contact with the deepest part of the recess and the line segment An is not less than 0.1 μm and not more than 0.8 μm, and among the recesses constituting the irregularities of the hard particles on the rake face side reference line The length Ls of the line segment As connecting the tips of the convex portions at both ends sandwiching the concave portion in at least one concave portion is 0.05 μm or more and 0.5 μm or less, and is parallel to the line segment As and the deepest portion of the recess The distance Ds between the line segment Bs in contact with the line segment As and the line segment As is not less than 0.05 μm and not more than 0.5 μm, Ln is greater than Ls, and the length of the contact line between the hard particles on the flank side and the coating Is Sn, and the contact line includes one or more recesses, Assuming that the sum of the lengths Ln is Tn, the ratio Tn / Sn is 0.1 or more, and the length of the contact line between the hard particle on the rake face side and the coating is Ss. The ratio Ts / Ss was confirmed to be 0.1 or more, where Ts is the sum of the lengths Ls of the respective recesses.

<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 conditions of the intermittent cutting process are as follows: alloy tool steel (die steel) SKD11 is used as a work material, the cutting speed is 200 m / min, the feed speed is 0.2 mm / blade, and the cutting depth is 2.0 mm. Turning was performed until 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 the results shown in “Cutting Length” in Table 2, 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. It is clear. This is considered to be due to the improved adhesion between the base material and the coating and the suppression of the adhesion of the work material on the rake face. As is clear from the above evaluation results, 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 (9)

A surface-coated cutting tool comprising a substrate 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 the surface-coated cutting tool is cut along a plane including a normal line to the rake face of the surface-coated cutting tool, the surface on the flank side of the substrate is a flank having a length of 50 μm located on the surface. The surface roughness Rz, n at the side reference line is 1 μm or more and 30 μm or less, and the surface on the rake face side of the base material has a surface roughness Rz, s at the rake face side reference line having a length of 50 μm. Is 0.5 μm or more and 5 μm or less, and Rz, n is larger than Rz, s,
The length Ln of the line segment An 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 on the flank side reference line is 0.1 μm. The distance Dn between the line segment An and the line segment Bn parallel to the line segment An and in contact with the deepest part of the recess is 0.1 μm or more and 0.8 μm or less.
The length Ls of the line segment As 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 on the rake face side reference line is 0.05 μm. The distance Ds between the line segment As and the line segment Bs parallel to the line segment As and in contact with the deepest part of the recess is 0.05 μm or more and 0.5 μm or less.
Ln is greater than Ls;
The length of the contact line between the hard particles on the flank side and the coating is Sn, and the contact line includes one or more recesses, and the sum of the lengths Ln of the recesses is Tn. Then, the ratio Tn / Sn is 0.1 or more,
The length of the contact line between the hard particles on the rake face side and the coating is Ss, and the contact line includes one or more recesses, and the sum of the lengths Ls of the recesses is Ts. Then, the surface-coated cutting tool whose ratio Ts / Ss is 0.1 or more. The coating consists of a columnar crystal structure,
The columnar crystal width Wn in contact with the recess on the flank side is smaller than the Ln,
2. The surface-coated cutting tool according to claim 1, wherein a columnar crystal width Ws of the coating in contact with the concave portion on the rake face side is smaller than the Ls. The length Ln and the distance Dn are both 0.1 μm or more and 0.5 μm or less,
The surface-coated cutting tool according to claim 1, wherein both the length Ls and the distance Ds are 0.05 μm or more and 0.3 μm or less. 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 1 to 3, wherein an atomic ratio of Si in the first element is 20 atomic% or less.   The surface-coated cutting tool according to claim 4, wherein an atomic ratio of Si occupying the first element is 3 atomic% or more and 10 atomic% or less. The surface of the base material is processed after sintering the hard particles and the binder phase, and the surface roughness of the surface of the base material before processing the surface is Rz.
The surface-coated cutting tool according to claim 1, wherein Rz, n is larger than Rz. 1 μm or more in the flank side reference line having a length of 50 μm located on the surface of the flank side of the substrate in a cross section when the surface coated cutting tool is cut in a plane including a normal line to the rake face of the surface coated cutting tool A first step of forming a surface roughness Rz, n of 30 μm or less;
A second step of forming a surface roughness Rz, s of 0.5 μm or more and 5 μm or less at a rake surface side reference line of 50 μm in length located on the surface of the rake surface of the substrate in the cross section;
A third 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;
On the substrate, seen including a fourth step of forming a coating film by physical vapor deposition,
The base material is a method for producing a surface-coated cutting tool, wherein the surface is treated after sintering hard particles and a binder phase .   The method of manufacturing a surface-coated cutting tool according to claim 7, wherein the first step is performed by blasting or laser processing.   The method for manufacturing a surface-coated cutting tool according to claim 7 or 8, wherein both the second step and the third step are performed by an ion bombardment process.