JP5239062B2 - Surface-coated cutting tool and manufacturing method thereof - Google Patents

Description

  The present invention relates to a surface-coated cutting tool including a substrate and a coating film formed thereon, and a method for manufacturing the same.

  Recent cutting tool trends include the need for dry machining without cutting fluids from the viewpoint of global environmental conservation, the diversification of work materials, and higher cutting speeds to further improve machining efficiency. For example, the tool edge temperature tends to be higher, and the characteristics required for the tool material are becoming stricter. In particular, as a required characteristic of tool materials, the coating film formed on the base material has high temperature stability (oxidation resistance and coating film adhesion) as well as wear resistance related to the cutting tool life. Improvement of crack resistance and fracture resistance is becoming more important.

  In order to improve wear resistance and surface protection function, TiAl nitride is used as a hard coating on the surface of cutting tools and wear-resistant tools made of hard base materials such as WC-based cemented carbide, cermet, and high-speed steel. It is well known to form a single layer or multiple layers. However, in recent high-speed and dry processing, a sufficient tool life cannot be obtained with a coating film made of TiAl nitride.

  Under such circumstances, as a method for improving the heat resistance of the coating film and realizing a long tool life, Patent Document 1 discloses a coating film in which Si is further added to a composite nitride of Ti and Al. Proposed. Thus, the coating film containing Si has an advantage that the heat resistance is superior to the coating film made of a nitride of TiAl because a dense oxidation protective film containing Si is formed on the surface thereof. On the other hand, however, the coating film disclosed in Patent Document 1 has a problem that its performance of hardness and toughness is not sufficient.

  As an attempt to solve such a problem, Patent Document 2 and Patent Document 3 include Ti nitride, carbonitride, nitrogen oxide, or a layer containing an appropriate amount of Si in carbon nitride oxide, and Ti and Al. There is disclosed a coating film in which nitrides, carbonitrides, nitride oxides, or layers composed of carbonitride oxides are alternately laminated. Patent Document 4 discloses a coating film in which layers made of AlTiSiN and layers made of TiSiN are alternately stacked.

JP 07-310174 A JP 2000-334606 A JP 2000-334607 A JP 2003-291005 A

  However, since the TiSi-based coating film disclosed in Patent Document 2 and Patent Document 3 has an extremely high compressive residual stress, the coating film itself is easily self-destructed. There was a problem that the adhesion was not sufficient. Further, the coating film disclosed in Patent Document 4 is excellent in heat resistance, hardness, and toughness. On the other hand, when cutting is performed using a cutting tool coated with such a coating film, There was a tendency to peel between layers, and there was a problem that sufficient tool life could not be obtained.

  In this way, attempts have been made to impart heat resistance to the coating film by including Si in the coating film, but the addition of Si increases the compressive stress of the coating film. There has been a problem that the film is self-destructed or the stress difference with the base material becomes large and the adhesion of the coating film to the base material is lowered. As an attempt to solve such a problem, as shown in Patent Documents 2 and 3, a layered structure of a layer containing Si and a layer not containing Si is used, or as shown in Patent Document 4, a compressive stress is deliberately used. Attempts have been made to add Si without applying a compressive stress to the coating film by forming a coating film under film-forming conditions that reduce the thickness of the coating film. However, the increase in hardness due to the addition of Si is impaired, and as a result, sufficient tool performance has not been obtained.

  The present invention has been made in view of the current situation as described above, and the purpose of the present invention is to make the characteristics of AlTiSiMN excellent in heat resistance, hardness, and stress balance, and in TiAlSiMeN excellent in wear resistance and toughness. Provides a surface-coated cutting tool that has a coating film on the surface that combines wear resistance, chipping resistance, and adhesion by combining the properties and making the shape of the blade edge unique at the edge of the blade edge There is to do. M and Me each independently represent one or more elements selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

  In order to solve the above problems, the present inventors have made various studies on the configuration of the coating film, and the coating film disclosed in Patent Document 4 is easily peeled between layers. It was found that the Si amount of each layer constituting the laminated structure was not matched. Based on this knowledge, the inventors of the present invention have finally completed the present invention by further studying the composition of the layer made of AlTiSiN and the layer made of TiAlSiN and studying the structure of the coating film at the edge line of the blade edge.

That is, the surface-coated cutting tool of the present invention is one and a coating film formed thereon with the substrate, the coating _{film, Al a Ti b Si c M} d N ( provided that Shikichu , 0.35 ≦ a ≦ 0.7,0 <c ≦ 0.3,0 ≦ d ≦ 0.3, and A layer consisting of a + b + c + d = 1), Ti e Al f Si g Me h N ( provided that Shikichu , 0 ≦ f ≦ 0.4, 0 <g ≦ 0.3, 0 ≦ h ≦ 0.3, e + f + g + h = 1) and a laminate in which two or more layers are alternately laminated, Medium M and Me each independently represent one or more elements selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W, and each of the A layer and the B layer is 20 nm or less. The surface of the coating film formed on the edge portion of the blade edge has a distance of 2 μm or more between the steep convex portion and the adjacent convex portion. Irregularities formed irregularly between the first concave portion connecting the curved portions with a gentle curved surface and the second concave portion where the distance between adjacent convex portions is less than 2 μm and connecting the curved portions with a gentle curved surface It is a peeling surface having a feature.

  It is preferable that the peeling surface has irregularities in which first concave portions and second concave portions are alternately formed. The coating film formed on the cutting edge ridge line portion has a thin film region, and the thin film region is preferably 70% or less of the film thickness of the coating film formed on a portion other than the cutting edge ridge line portion.

  The thin film region preferably occupies an area of 50% or more of the coating film formed on the edge portion of the blade edge, and more preferably occupies an area of 80% or more of the coating film. The coating film preferably increases in compressive stress in the thickness direction from the substrate side to the surface side.

  The difference between the atomic ratio c of Si constituting the A layer and the atomic ratio g of Si constituting the B layer is preferably 0.05 or less.

  In the above method for manufacturing a surface-coated cutting tool, the coating film is preferably formed on the substrate by gradually changing the bias voltage of the substrate from the start of film formation to the end of film formation. It is preferable that the bias voltage of the substrate at the start of film formation is 30 V or less, and the bias voltage is gradually changed so that the bias voltage of the substrate at the end of film formation is 70 V or more.

  The surface-coated cutting tool of the present invention has the characteristics as described above, and has the characteristics of AlTiSiMN, which is excellent in heat resistance, hardness, and stress balance, and the characteristics of TiSiMeN, which is excellent in wear resistance and toughness. It combines wear resistance, fracture resistance, and adhesion.

It is typical sectional drawing which shows the shape of the blade edge ridgeline part vicinity of the surface coating cutting tool of this invention. It is the schematic of an arc ion plating apparatus. It is an observation image when the cutting edge edge part vicinity of the cross section of the surface covering cutting tool of this invention is observed by 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 layer thickness or film thickness is measured by a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the composition thereof is an energy dispersive X-ray analyzer. It shall be measured by (EDS: Energy Dispersive x-ray Spectroscopy).

<Surface coated cutting tool>
The surface-coated cutting tool of the present invention comprises a substrate and a coating 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>
As the base material of the surface-coated cutting tool of the present invention, a conventionally known material known as such a cutting tool base material can be used without particular limitation. 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.) High-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, and mixtures thereof), cubic boron nitride sintered body, diamond sintered body Etc. can be mentioned as examples of such a substrate. When a cemented carbide is used as such a 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.

<Coating film>
Coating of the present _{invention, Al a Ti b Si c M} d N ( provided that Shikichu, 0.35 ≦ a ≦ 0.7,0 <c ≦ 0.3,0 ≦ d ≦ 0.3, a + b + c + d = 1) a layer A consisting _{of, Ti e Al f Si g Me} h N ( provided that Shikichu, 0 ≦ f ≦ 0.4,0 <g ≦ 0.3,0 ≦ h ≦ 0.3, e + f + g + h = 1) And a layered product in which two or more layers are alternately laminated, and M and Me in the above formulas are each independently from V, Cr, Zr, Nb, Mo, Hf, Ta, and W. One or more elements selected from the group consisting of the A layer and the B layer each having a layer thickness of 20 nm or less, and the surface of the coating film formed on the edge portion of the blade edge having a steep convex portion And the distance between the adjacent convex portions is 2 μm or more, and the distance between the first concave portion connecting the curved portions with a gentle curved surface is less than 2 μm. In addition, the second concave portion connecting the curved portions with a gentle curved surface is an irregular surface having irregularities formed irregularly.

  Such a coating film of the present invention includes an aspect in which the entire surface of the substrate is coated, and also includes an aspect in which the coating film is not partially formed. The aspect which the lamination | stacking aspect of a part differs is also included. Moreover, it is preferable that the coating film of this invention is the whole film thickness of 1 micrometer or more and 10 micrometers or less. 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 film is 2 μm or more and 8 μm or less. In addition, said coating film may contain other arbitrary layers other than A layer and B layer.

<Features at the edge of the cutting edge>
FIG. 1 is a cross-sectional view of the surface-coated cutting tool of the present invention cut along a plane including a normal line of the coating film surface at the center of the rake face and a ridge where two flank surfaces intersect. In the cross section of FIG. 1, the surface of the coating film 2 formed on the cutting edge ridge line portion 6 has a distance between the steep convex portion and the adjacent convex portion of 2 μm or more, and A concave surface having irregularities in which a first concave portion connecting between them with a gentle curved surface and a second concave portion where the distance between adjacent convex portions is less than 2 μm and connecting between them with a gentle curved surface are irregularly formed. It is characterized by being. Here, the “steep convex portion” means a shape in which the tip of the convex portion is sharp and no smooth surface is formed on the convex curved surface.

  Such a peeled surface can be enhanced in cutting edge strength because the cutting edge ridge portion 6 serving as a starting point of chipping has a partially thinned film and has a partially steep convex portion. As a result, while the wear resistance is improved by the coating film 2, it is possible to prevent the coating film from dropping and chipping, and to obtain excellent wear resistance and excellent chipping resistance. Such a peeling surface is formed by a manufacturing method unique to the present invention, and a specific manufacturing method thereof will be described later.

  Here, the “blade edge line” and the “blade edge line part” in the present invention indicate different concepts. The “blade edge ridge line” indicates a ridge where the rake face and the flank face intersect in the cross section shown in FIG. 1. Such a ridge is formed by a special film forming method described later in the present invention. Therefore, in the present invention, the rake face 3 and the flank face 4 are approximated by straight lines in such a cross section as shown in FIG. An intersection where the extension lines intersect is defined as a cutting edge ridge line 5. On the other hand, the “blade edge line portion” is a part most involved in cutting of the work material during the cutting process, and indicates the peripheral part of the blade edge line 5. When the rake face 3 and the flank face 4 are approximated by straight lines in FIG. 5, the region where the above-mentioned peel face is formed (that is, from the bending point of the rake face 3 to the bending point of the flank face 4 on the surface of the coating film 2). ) Is defined as a cutting edge ridge line portion (sometimes simply referred to as a “cutting edge”).

  On the other hand, with respect to the plane defined above, “the center of the rake face” means the center of the rake face in the geometrical sense, and a through-hole for attaching the surface-coated cutting tool to the center of the rake face. When is opened, it means the geometrical center of the rake face when it is assumed that the through hole is not opened. The “ridge where two flank surfaces intersect” means a ridge where two flank surfaces intersect. If this ridge does not form a clear ridge, both flank surfaces are geometrically enlarged. In this case, it means a hypothetical ridge where the two intersect. In addition, when two or more planes defined in this way exist in one surface-coated cutting tool, any one plane is selected.

  It is preferable that said peeling surface has the unevenness | corrugation in which the 1st recessed part and the 2nd recessed part were formed alternately. The unevenness of such a shape is formed by self-destruction due to compressive stress inside the coating film, but by cutting the edge edge line part in advance, even a Si-containing film having high compressive stress as in the present invention, It is possible to achieve both adhesion and wear resistance.

  And in this invention, in the said cross section, the coating film formed in the blade edge ridgeline part has a thin film area | region which is a film thickness of 70% or less of the film thickness of the coating film formed in other than a blade edge ridgeline part. It is preferable. Such a thin film region is a portion corresponding to the bottoms of the first recess and the second recess, but the coating film has a thin film region, so that the coating film can be stably worn during cutting. And the tool life can be improved. In the present invention, the thin film region is specified by polishing a cross section of the surface-coated cutting tool with a cross section polisher (CP) using an argon ion beam and observing the polished surface with an SEM.

  The thin film region preferably occupies an area of 50% or more of the coating film formed on the cutting edge ridge line part, and more preferably occupies an area of 80% or more of the coating film formed on the cutting edge ridge line part. More preferably, it occupies an area of 90% or more. As described above, the cutting edge ridge line portion has the thin film region, so that the wear of the coating film in the cutting can be stabilized and the tool life can be greatly improved.

  In the coating film of the present invention, it is preferable that the compressive stress increases in the thickness direction from the substrate side to the surface side. Here, “the compressive stress increases in the thickness direction” may be continuous or stepwise as long as the compressive stress increases in the thickness direction of the coating film. Further, even if the compressive stress partially decreases in the thickness direction, it does not depart from the scope of the present invention as long as it increases as a whole. Since the coating film has such a stress distribution, in combination with the effect brought about by the peeling surface in the edge portion of the cutting edge described above, the wear resistance and the toughness are highly compatible with each other. The adhesion between the material and the coating film is further improved. This is because, by reducing the compressive stress on the substrate side, ensuring the adhesion between the substrate and the coating film, while gradually increasing the compressive stress toward the surface side, This is considered to be because the internal destruction of the coating film due to stress is prevented, and the progress of cracks generated on the surface of the coating film during cutting is suppressed.

  In this case, the compressive stress in the portion close to the base material side of the coating film is preferably in the range of 1.5 GPa or less, and the surface side of the coating film has a compressive stress of 2 GPa or more. preferable. In the present invention, “the surface side of the coating film” conceptually indicates the outermost surface as the word indicates, but as an actual measurement condition, an average compressive stress from the surface to a thickness of 0.5 μm is used. Means.

  Here, the compressive stress referred to in the present invention is one type of internal stress (inherent strain) existing in the coating film, and is represented by a numerical value (unit: GPa) of “−” (minus). is there. For this reason, the expression that the compressive stress (internal stress) is high indicates that the absolute value of the numerical value is large, and the expression that the compressive stress (internal stress) is low indicates that the absolute value of the numerical value is small. I mean. Incidentally, what the above numerical value is represented by “+” (plus) is tensile stress.

The average compressive stress and stress distribution of the present invention are measured by the following sin ² ψ method. The sin ² ψ method using X-rays is widely used as a method for measuring the residual stress of a polycrystalline material. This measurement method is described in detail on pages 54 to 66 of "X-ray stress measurement method" (Japan Society for Materials Science, published by Yokendo Co., Ltd. in 1981). The X-ray penetration depth is fixed in combination with the tilt method, and the diffraction angle 2θ with respect to various ψ directions is measured in a plane including the stress direction to be measured and the sample surface normal set at the measurement position, and 2θ− A sin ² ψ diagram can be created, and the average compressive stress from the gradient to the depth (distance from the coating film surface side) can be obtained. In the case of the present invention, the stress distribution is measured by obtaining the thickness from the coating film surface side by observing the cross section of the coating film and sequentially obtaining the average compressive stress up to the thickness (depth). That is, the stress distribution of the present invention can be understood as a set of average stresses from the coating film surface side to its thickness. In this respect, the average stress at a certain point in the coating film indicates an average stress from the surface of the coating film to the point.

  More specifically, X-rays that cause X-rays from an X-ray source to enter a sample at a predetermined angle, detect X-rays diffracted by the sample with an X-ray detector, and measure internal stress based on the detected values. In the stress measurement method, an X-ray is incident from an X-ray source at an arbitrary set angle on the sample surface at an arbitrary position of the sample, passes through the X-ray incident point on the sample, and the ω axis is perpendicular to the incident X-ray When the sample is rotated around the χ axis that coincides with the incident X-ray when the ω axis is rotated in parallel with the data base, the sample is adjusted so that the angle formed by the sample surface and the incident X-ray is constant. The compressive stress inside the sample can be obtained by measuring the diffraction line while changing the angle ψ formed by the normal line of the diffraction surface and the normal line of the sample surface while rotating.

  As an X-ray source for measuring the average stress in the thickness direction of the coating film, synchrotron radiation is used in terms of the quality of the X-ray source (high brightness, high parallelism, wavelength variability, etc.). It is preferable to use light (SR).

Further, in order to obtain the compressive stress from the 2θ-sin ² ψ diagram as described above, the Young's modulus and Poisson's ratio of the coating film are required. The Young's modulus can be measured using a dynamic hardness meter, and since the Poisson's ratio does not vary greatly depending on the material, a value of around 0.2 may be used.

  Hereinafter, the A layer and the B layer constituting the laminate included in such a coating film will be described in more detail.

<A layer>
A layer constituting the _{laminate, Al a Ti b Si c M} d N ( provided that Shikichu, 0.35 ≦ a ≦ 0.7,0 <c ≦ 0.3,0 ≦ d ≦ 0.3, a + b + c + d = 1). Such an A layer is excellent in heat resistance, hardness, and stress balance, and therefore effective for high-speed, chipping resistance of the cutting edge during dry processing. The atomic ratio c of Si is preferably 0.1 or less. When c is 0.1 or less, an increase in compressive stress can be suppressed while improving heat resistance, and a decrease in adhesion can be avoided. The a is preferably 0.5 ≦ a ≦ 0.6, the c is preferably 0.03 ≦ c ≦ 0.08, and the d is more preferably 0 ≦ d ≦ 0.3. In this case, the balance of heat resistance, hardness, and compressive residual stress is good. In the above formula, if a is less than 0.35 or d exceeds 0.3, the effect of improving the oxidation resistance and hardness cannot be sufficiently obtained, and if a exceeds 0.7 , Since the hardness of the coating film is greatly reduced and the wear resistance is lowered.

  Here, M constituting the A layer is one or more elements selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W. By including such an element in the A layer at a ratio of 30 atomic% or less, solid solution strengthening occurs in the A layer, and the hardness of the A layer can be increased. Among the above elements, V, Nb, Mo, W, etc. have the merit that the tool life can be extended because an oxide is formed by the heat generated during cutting and the self-lubricating effect is exhibited. This is preferable.

Note that in the notation Al _a Ti _b Si _c M _d N, and "Al _a Ti _b Si _c M _d", the composition ratio between "N" 1: not limited only to the case of 1, the composition ratio All possible ratios can be included, and the ratio between the two is not particularly limited.

<B layer>
B layer constituting the laminate together with the above layer _{A, Ti e Al f Si g Me} h N ( provided that Shikichu, 0 ≦ f ≦ 0.4,0 <g ≦ 0.3,0 ≦ h ≦ 0. 3, e + f + g + h = 1). Such a B layer is excellent in wear resistance and toughness, but in order to cope with further high speed and dry processing, there is a limit in itself, so in the present invention, it is laminated alternately with the above A layer. It is. When said g is 0.1 or less, the rapid increase of the compressive stress of B layer can be suppressed and the adhesive fall can be suppressed. Here, f is preferably 0 ≦ f ≦ 0.4, g is 0.03 ≦ g ≦ 0.08, and h is more preferably 0 ≦ h ≦ 0.3. In this case, the balance between wear resistance and toughness is further improved. In the above formula, if f exceeds 0.4, the compressive residual stress increases, and delamination tends to occur, which is not preferable.

  Here, Me constituting the B layer is one or more elements selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W, similarly to M constituting the A layer. It is characterized by being. By including such an element in the B layer at a ratio of 30 atomic% or less, solid solution strengthening occurs in the B layer, and the hardness of the B layer can be increased. Among the above elements, V, Nb, Mo, W, etc. have the merit that the tool life can be extended because an oxide is formed by the heat generated during cutting and the self-lubricating effect is exhibited. This is preferable.

Note that in the notation Ti _e Al _f Si _g Me _h N, the composition ratio between "Ti _e Al _f Si _g Me _h" and "N" 1: not limited only to the case of 1, the composition ratio All possible ratios can be included, and the ratio between the two is not particularly limited.

<Layer thickness and laminated body of A layer and B layer>
Each of the A layer and the B layer as described above has a layer thickness of 20 nm or less. By laminating two or more A layers and B layers having such a thickness alternately, the progress of cracks due to impact during cutting is suppressed, and the fracture resistance is improved. The A layer and the B layer are preferably as thin as possible because the adhesion can be improved by thinning them to such an extent that they do not peel between the layers, but for convenience of manufacturing facilities, they are 1 nm or more and 10 nm or less. It is more preferable. When these layer thicknesses are less than 1 nm, the number of rotations of the rotary table on which the substrate of the film forming apparatus is set is too fast, making film formation difficult due to the specifications of the apparatus. The respective characteristics of both the A layer and the B layer cannot be enjoyed.

<Difference in atomic ratio of Si>
The difference between the atomic ratio c of Si constituting the A layer and the atomic ratio g of Si constituting the B layer is preferably 0.05 or less, more preferably 0.03. By adjusting the atomic ratio of Si in the A layer and the B layer within such a range, the adhesion of the coating film can be remarkably improved. If the Si atomic ratio difference exceeds 0.05, the uniformity of the composition cannot be obtained, or the stress difference between the layers is too large.

<Manufacturing method>
The coating film of the present invention is preferably formed by physical vapor deposition (PVD method). In order to form the coating film of the present invention on the substrate surface, it is indispensable to be a film forming process capable of forming a compound having high crystallinity, and various film forming methods were examined. As a result, 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 ratio of raw material elements, before forming the coating film, On the other hand, since metal or gas ion bombardment treatment is possible, the adhesion between the coating film and the substrate is significantly improved, which is preferable.

  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. FIG. 2 is a schematic diagram of an arc ion plating apparatus 200 used in the cathode arc ion plating method. In the opposing evaporation sources 201 and 202, an AlTiSiM target for the A layer is set in the evaporation source 201, and a TiAlSiMe target for the B layer is set in the evaporation source 202. Further, the base 210 (cutting tool) is set on the rotary table 204.

Here, a of Al _a Ti _b Si _c M _d N constituting the A layer by the composition of the target to be set in the evaporation source 201 (the ratio of Al and Ti, Si and M), b, c, and d Can be determined. Also, determine the Ti _e Al _f Si _g Me _h N of e, f, g, and h constituting the B layer by the composition of the target to be set in the evaporation source 202 (the ratio between Ti and Al and Si and Me) can do.

  Then, after the apparatus is evacuated to a vacuum, sputter cleaning (bombarding) with Ar gas is performed while rotating the rotary table 204 at 5 rpm while the apparatus is heated to, for example, 500 ° C. Thereafter, a bias voltage of −50 V is applied to the substrate, and the evaporation sources 201 and 202 are always arc-discharged by a constant arc current while rotating the rotary table 204 at 3 rpm, thereby ionizing each target. At the same time, nitrogen, which is a reactive gas, is introduced from the gas introduction port 205, and A layers and B layers are alternately formed on the surface of the substrate 210.

That, Al _a front when the substrate 210 passes the evaporation source 201 Ti _b Si _c M _d N consisting of A layer is deposited, Ti _e previous evaporation source 202 when the substrate 210 passes al _f Si _g Me _h N consisting B layer is deposited, thus the rotary table 204 can be laminated sequentially alternately a layer and the B layer according to rotate. By adjusting the arc current of the evaporation source 201 and the rotation speed of the table during film formation, the layer thicknesses of the A layer and the B layer can be adjusted, and the arc currents of the evaporation sources 201 and 202 are kept constant. As a result, both the A layer and the B layer can have substantially the same layer thickness.

  Here, the lower the arc current of the evaporation sources 201 and 202, the thinner the layer thicknesses of the A layer and the B layer. However, the arc current needs to be 80 A or more in order to stabilize the discharge of the target. When the arc current is less than 80 A, the arc discharge becomes unstable and it becomes difficult to form the layer thicknesses of the A layer and the B layer uniformly.

  When the arc current is about 150 A, the A layer and the B layer having a layer thickness of 20 nm or less can be formed by setting the number of rotations of the table to 3 rpm or more and 15 rpm or less. If the number of rotations of the table is less than 3 rpm, the layer thicknesses of the A layer and the B layer may exceed 20 nm, and exceeding 15 rpm is not preferable because of restrictions on manufacturing equipment.

  In the formation of the coating film, in order to form the coating film so that the compressive stress increases in the thickness direction from the base material side to the surface side of the coating film, from the start of film formation to the end of film formation, It is preferable to gradually change conditions such as the pressure in the chamber and the bias voltage applied to the substrate. That is, for example, the film formation is started with a bias voltage of 30 V or less at the initial stage of film formation, and the bias voltage is increased gradually or stepwise from there to adjust the bias voltage so that the bias voltage at the latter stage of film formation is 70 V or more. It is preferable to do. By forming the coating film under such film formation conditions, the compressive stress on the surface side of the coating film increases, and particularly the compressive stress concentrates on the edge line 5 of the blade and self-destructs. A peeling surface is formed on the blade edge portion 6. Thus, no attempt has been made in the prior art to concentrate only the coating film formed on the cutting edge by concentrating the compressive stress on the edge 5 of the cutting edge, and the manufacturing method of such a cutting tool is extremely unique. The effect obtained by this is also far superior to the effect obtained by the prior art.

  From the same viewpoint as the above bias voltage, the temperature in the chamber at the initial stage of film formation is set to 550 ° C. or higher, and the temperature in the chamber is gradually or stepwise increased to 450 ° C. or lower at the final stage of film formation. It is preferable to adjust the temperature in the chamber.

  The layer thickness of each layer can be controlled by the number of rotations of the turntable 204 and the arc current value. If the thickness of each of the A layer and the B layer is less than 1 nm, the number of rotations of the rotary table becomes very fast, and it is difficult to form a film on the device specifications. The arc ion plating apparatus 200 includes a plurality of heaters 206.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. In addition, the compound composition of the coating film in an Example and a comparative example was confirmed by XPS (X-ray photoelectron spectroscopy analyzer). The average compressive stress was measured by the sin ² ψ method described above.

In the measurement by the sin ² ψ method, the energy of the X-ray used was 10 keV, and the peak of the diffraction line was a (200) plane of Ti _0.5 Al _0.5 N. The measured diffraction peak position is determined by fitting a Gaussian function, the slope of the 2θ-sin ² ψ diagram is obtained, and the value obtained using a dynamic hardness meter (MST nanoindenter) is adopted as the Young's modulus. The value of TiN (0.19) was used as the Poisson's ratio.

  An arc ion plating apparatus as shown in FIG. 2 was used, a target for forming each layer was set in an evaporation source, and a coating film was formed on the substrate.

  As the base material, a P20 equivalent cemented carbide milling throw tip (shape: SEMT13T3AGSN-G) was prepared, and the coating films of the examples and comparative examples shown in Table 1 were formed.

  The coating film was formed by laminating “A layer” and “B layer” described in the “Composition” column of Table 1. The “layer thickness” column indicates the thickness of each of the A layer and the B layer, and the “total film thickness” column indicates the thickness of the coating film.

  The column “Substrate vicinity compressive stress” shows the average compressive stress in the region from the side of the coating film in contact with the substrate to 0.5 μm, and the column “Surface vicinity compressive stress” shows the coating The average compressive stress in the region from the surface of the film to a thickness of 0.5 μm was shown. In the column of “difference of Si ratio”, the difference between the atomic ratio c of Si in the A layer and the atomic ratio g of Si in the B layer constituting the coating film is shown.

For example, in Example 1, the arc ion plating apparatus of FIG. 2 is used, Al _0.58 Ti _0.25 Si _0.05 Cr _0.12 is set as the target material of the evaporation source 201, and Ti _0.68 Si _0.04 Nb is set as the target material of the evaporation source 202. _A surface-coated cutting tool was prepared by setting _0.28 and forming a coating film. In order to make the coating film have a desired composition, N ₂ gas was introduced as a reaction gas, and Ar gas was appropriately introduced to adjust the pressure in the chamber.

  First, after evacuating so that the pressure in the chamber of the arc ion plating apparatus of FIG. 2 became a vacuum, the temperature in the chamber was raised to 600 ° C. Then, Ar gas was introduced, the pressure in the chamber was maintained at 1.0 Pa, the DC bias voltage was gradually increased to −1000 V, and the substrate surface was cleaned (bombarded) for 15 minutes. Thereafter, the argon gas was exhausted. As a result, Ar ions sputter-cleaned the substrate surface, and strong dirt and oxide films were removed.

Next, an A layer and a B layer were formed. The N ₂ gas is introduced so that the pressure in the chamber becomes 3 Pa, and the Al _0.58 Ti _0.25 Si _0.05 Cr _0.12 target and the Ti _0.68 Si _0.04 Nb _0.28 target are _arced while rotating the rotary table 204 at a rotation speed of 3 rpm. By ionizing as 150A and reacting with N ₂ gas, respectively, a layer A made of Al _0.58 Ti _0.25 Si _0.05 Cr _0.12 N with a thickness of 2 nm and a Ti _0.68 Si _0.04 Nb _0.28 N with a thickness of 2 nm on the substrate. 875 layers were alternately formed with each of the B layers to form a coating film having a total film thickness of 3.5 μm. At this time, the base material DC bias voltage at the start of film formation was set to 25 V, and then changed at a constant ratio so that the base material DC bias voltage at the end of film formation was adjusted to 80 V, and the film was formed for 180 minutes. . Thus, the coating film containing the laminated body which the A layer and the B layer were laminated | stacked alternately was formed into a film, and the surface coating cutting tool of Example 1 was produced.

  The surface-coated cutting tool was cut along a plane including the normal of the coating film surface at the center of the rake face of the surface-coated cutting tool thus produced and a ridge where two flank surfaces intersect. Then, the cross section was polished by a cross section polisher (CP) using an argon ion beam. The polished surface was observed with a SEM at a magnification of 1500 times. The observed image is shown in FIG.

  Based on the image shown in FIG. 3, the shape of the cutting edge ridge line portion was evaluated. As a result, the surface of the coating film formed on the cutting edge ridge line portion of the surface-coated cutting tool of Example 1 had a steep convex portion. The distance between adjacent convex portions is 2 μm or more and the distance between adjacent first convex portions and the adjacent convex portions is less than 2 μm, and the distance between them is connected with a gentle curved surface. It was confirmed that the second concave portion was a peeling surface having irregularities formed irregularly. Moreover, the ratio of the area | region (thin film area | region) of 70% or less of the whole film thickness of the coating film which occupies for a blade edge ridgeline part was computed based on the same observed image. The ratios of the thin film regions calculated in this way are shown in the column “Thin film region ratio” in Table 1.

  Also in the surface-coated cutting tools of Examples 2 to 20, when the edge of the edge of the blade was observed with an SEM in the same manner as in Example 1, it was confirmed that a peeled surface having the same shape was formed. Further, the ratio of the thin film region was calculated by the same method as in Example 1.

(Cutting performance evaluation)
The throwaway tip for surface-coated milling in each example and each comparative example was evaluated under the following cutting conditions. The results of the cutting evaluation are shown in Table 2.

(1) Milling continuous evaluation A milling continuous test was performed using the throw-away tip for surface-coated milling produced above. As for the conditions for continuous milling, as described above, a P20-equivalent cemented carbide throwaway tip (shape: SEMT13T3AGSN-G) is used as the base material, and SCM435 (block material of length 300 mm × width 200 mm) is used as the work material. The cutting speed was 300 m / min, the feed amount was 0.25 mm / t, the cutting amount was 1.5 mm, and no cutting oil was used. The wear width of the flank at a cutting time of 15 minutes was measured. The smaller the wear width, the better the wear resistance.

(2) Milling Intermittent Evaluation A milling intermittent test was performed using the surface-coated milling throwaway tip produced above. The conditions for milling interrupted cutting were S50C (length 300 mm × width 200 mm) as a work material, cutting speed = 100 m / min, feed rate = for an interrupted surface in which 300 holes were drilled with a φ8 drill. 0.4 mm / t, cutting depth = 1.5 mm, performed without cutting oil, and measured the distance of cutting until the chip surface was damaged. The longer the cutting distance, the better the chipping resistance.

  From Table 2, it was found that the surface-coated cutting tool of the example has a significantly improved tool life as compared with the surface-coated cutting tool of the comparative example, and can sufficiently cope with high-speed machining and dry machining. Thus, it was confirmed that the surface-coated cutting tool of the present invention has both the characteristics of AlTiSiMN and TiSiMeN, and has wear resistance, fracture resistance, and adhesion.

  Although the embodiments and examples of the present invention have been described as 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, 210 base material, 2 coating film, 3 rake face, 4 flank face, 5 edge edge line, 6 edge edge line part, 200 arc ion plating apparatus, 201, 202 evaporation source, 204 rotary table, 205 gas inlet, 206 Heater.

Claims (9)

A surface-coated cutting tool comprising a substrate and a coating film formed thereon,
The coating _{film, Al a Ti b Si c M} d N ( provided that Shikichu, 0.35 ≦ a ≦ 0.7,0 <c ≦ 0.3,0 ≦ d ≦ 0.3, a + b + c + d = 1) consists of a layer A consisting _{of, Ti e Al f Si g Me} h N ( provided that Shikichu, 0 ≦ f ≦ 0.4,0 <g ≦ 0.3,0 ≦ h ≦ 0.3, e + f + g + h = 1) Including a laminate in which two or more B layers are alternately laminated,
In the formula, M and Me each independently represent one or more elements selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W;
Each of the A layer and the B layer has a layer thickness of 20 nm or less,
The surface of the coating film formed on the edge of the cutting edge is a first concave portion in which the distance between the convex portion having a steep shape and the adjacent convex portion is 2 μm or more and a gentle curved surface is formed therebetween. A surface-coated cutting tool, wherein a distance between adjacent convex portions is less than 2 μm, and a second concave portion connecting between the convex portions is a irregular surface formed irregularly.   The surface-coated cutting tool according to claim 1, wherein the peeling surface has irregularities in which the first concave portions and the second concave portions are alternately formed.   The coating film formed on the cutting edge ridge line portion has a thin film region having a film thickness of 70% or less of the film thickness of the coating film formed other than the cutting edge ridge line portion. Surface coated cutting tool.   The surface-coated cutting tool according to claim 3, wherein the thin film region occupies an area of 50% or more of the coating film formed on the edge of the cutting edge.   The surface-coated cutting tool according to claim 3, wherein the thin film region occupies an area of 80% or more of a coating film formed on the edge of the cutting edge.   The surface-coated cutting tool according to any one of claims 1 to 5, wherein the coating film increases in compressive stress in a thickness direction from the base material side to the surface side.   The surface-coated cutting according to any one of claims 1 to 6, wherein a difference between an atomic ratio c of Si constituting the A layer and an atomic ratio g of Si constituting the B layer is 0.05 or less. tool. It is a manufacturing method of the surface covering cutting tool according to claim 1,
The method for manufacturing a surface-coated cutting tool, wherein the coating film is formed on the substrate by gradually changing a bias voltage of the substrate from the start of film formation to the end of film formation.   The bias voltage of the substrate at the start of film formation of the coating film is set to 30 V or less, and the bias voltage is gradually changed so that the bias voltage of the substrate at the end of the film formation of the coating film is set to 70 V or more. The method for producing a surface-coated cutting tool according to claim 8.