JP2023163982A - Hard coating film and cutting tool using the film - Google Patents

Abstract

To achieve a hard coating film or the like stably exerting high performance under broad processing conditions.SOLUTION: A hard coating film 12 has a structure in which A layer (A1-An) consisting of AlxCr1-xN and B layer (B1-Bn) consisting of Ti1-ySiyN are alternately laminated. The thickness of C layer is 7nm or more but 18nm or less when a set of A layer and B layer in which the A layer and the B layer are alternately laminated is defined as C layer (C1-Cn). The total thickness of C layers is 1 μm or more but 6 μm or less, and the thickness of A layer and that of B layer are less than 10nm, respectively (here, x is 0.6 or more but 0.7 or less, and y is more than 0.05 but less than 0.08).SELECTED DRAWING: Figure 1

Description

The present invention relates to a hard coating and a cutting tool using the same.

Cutting tools used to process metal materials such as steel have high hardness, so when cutting, a large impact is applied to the cutting tool and high heat of 800 ° C. or more may be applied. Therefore, in order to improve the wear resistance, heat resistance, etc. of the cutting tool, the surface of the cutting tool is usually coated.

The coating is performed by, for example, depositing a nitride such as titanium or chromium on a base material such as high-speed steel or cemented carbide to form a thin film. Various methods have been proposed so far to improve the wear resistance and the like.

For example, Patent Document 1 describes at least one (Al _y Cr _1-y )X layer (0.2≦y≦0.7) and/or one (Ti _z Si _1-z )X layer (0 .01≦z≦0.3), then one further (AlCrTiSi)X mixed layer, then one further (Ti _z Si _1-z )X layer, then one further (AlCrTiSi) A hard material layer is proposed with at least one layer package comprising a mixed layer )X and then a further (Al _y Cr _1-y )X layer. The X is, for example, N.

Japanese Patent Application Publication No. 2013-176837

Patent Document 1 describes that the optimal layer thicknesses of the Al _y Cr _1-y N layer and the Ti _z Si _1-z N layer in the hard material layer are necessary for improving the lifespan ( [0016] of Patent Document 1). The optimum layer thickness is 75 to 200 nm, preferably 120 to 170 nm for the Al _y Cr _1-y N layer, and 50 to 150 nm, preferably 70 to 120 nm for the T _z Si _1-z N layer. .

AlCrN and TiSiN are materials commonly used for coating cutting tools. AlCrN has the advantage of being excellent in fracture resistance at low temperatures, but has the disadvantage of reduced hardness and strength at high temperatures due to the loss of N. Furthermore, TiSiN has the advantage of being excellent in wear resistance and suitable for high-speed cutting operations, but has the disadvantage of being hard and brittle. Therefore, a hard coating containing AlCrN and TiSiN is required to have both the above-mentioned advantages and not exhibit the above-mentioned disadvantages.

The hard material layer described in Patent Document 1 includes the mixed layer, and since the Al _y Cr _1-y N layer and the Ti _z Si _1-z N layer are thick, the average thickness of AlCrN and TiSiN is There is a high probability that one of the above-mentioned defects will be exhibited. Therefore, there is room for improvement in the hard material layer from the viewpoint of stably exhibiting high performance under a wide range of processing conditions.

Furthermore, other conventional hard coatings have not been able to avoid the problem of exposing the defects of either AlCrN or TiSiN. Therefore, cutting tools coated with the hard coating have insufficient properties such as hardness, heat resistance, wear resistance, and chipping resistance, and have a short lifespan, especially under harsh cutting conditions. Ta.

Therefore, one aspect of the present invention aims to realize a hard coating that has both the advantages of AlCrN and TiSiN and stably exhibits high performance under a wide range of processing conditions, and a cutting tool using the same.

The present inventor studied the composition and structure of a hard coating that has both the advantages of AlCrN and TiSiN. As a result, by using a specific composition of AlCrN and TiSiN and a specific laminated structure of the AlCrN layer and TiSiN layer, we have realized a hard coating that stably exhibits high performance under a wide range of processing conditions. They found that it is possible and came up with the present invention.

In order to solve the above problems, a hard coating according to one embodiment of the present invention has layers A made of Al _x Cr _1-x N and layers B made of Ti _1-y Si _y N stacked alternately. When the C layer is a combination of the A layer and the B layer which are alternately laminated, the C layer has a thickness of 7 nm or more and 18 nm or less; The total thickness is 1 μm or more and 6 μm or less, and the thicknesses of the A layer and the B layer are each less than 10 nm. (Here, the x is 0.6 or more and 0.7 or less, and the y is more than 0.05 and less than 0.08.)

According to one aspect of the present invention, it is possible to realize a hard coating that has both the advantages of AlCrN and TiSiN and stably exhibits high performance under a wide range of processing conditions, and a cutting tool using the same. That is, it is possible to provide a hard coating having excellent abrasion resistance, heat resistance, chipping resistance, and excellent film strength.

FIG. 1 is a vertical cross-sectional view schematically showing the surface structure of a cutting tool provided with a hard coating according to an embodiment of the present invention. FIG. 1 is a vertical cross-sectional view schematically showing an example of the structure of an arc evaporator. FIG. 3 is a top view of the arc evaporator shown in FIG. 2 when observed from vertically above. This is an X-ray diffraction pattern obtained by subjecting two types of cutting tools (Sample 1 and Sample 2) each having a hard film made of a laminated layer of AlCrN and TiSiN to X-ray diffraction. 5 is an enlarged view of the vicinity of 2θ=34° to 40° in FIG. 4. FIG. These are the X-ray diffraction patterns obtained by subjecting three types of cutting tools (samples 3 to 5) having hard coatings made of laminated AlCrN and TiSiN to X-ray diffraction. 7 is an enlarged view of the vicinity of 2θ=34° to 40° in FIG. 6. FIG. The results of observing the hard coating of one of the cutting tools obtained in Examples using a scanning transmission electron microscope (STEM) are shown. This is the result of observing the hard coating shown in the left diagram of FIG. 8 at a magnification of 1,000,000 times.

An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various changes can be made within the scope of the claims, and technical means disclosed in different embodiments may be combined as appropriate. The obtained embodiments also fall within the technical scope of the present invention. In this specification, unless otherwise specified, the numerical range "A to B" means "A or more and B or less".

[Embodiment 1: Hard coating]
A hard coating according to an embodiment of the present invention has a structure in which layers A made of Al _x Cr _1-x N and layers B made of Ti _1-y Si _y N are alternately laminated. When a combination of the A layer and the B layer stacked together is a C layer, the thickness of the C layer is 7 nm or more and 18 nm or less, and the total thickness of the C layer is 1 μm or more and 6 μm. The thickness of the A layer and the B layer are each less than 10 nm. (Here, the x is 0.6 or more and 0.7 or less, and the y is more than 0.05 and less than 0.08.)
FIG. 1 is a vertical cross-sectional view schematically showing the surface structure of a cutting tool provided with a hard coating according to an embodiment of the present invention. In the figure, 11 is a base material, 12 is a hard coating, and 10 is a cutting tool. FIG. 1 shows a case where n layers of A layers and n layers of B layers are laminated, and the A layers are represented as A ₁ to A _n , and the B layers are represented as B ₁ to B _n . In the figure, "..." means that the descriptions from A ₃ to B _n-1 are omitted. Although FIG. 1 shows a mode in which the surface of the base material 1 is coated with layer A and layer B is laminated on the layer A, the present invention is not limited to this. may be covered with a B layer, and the A layer may be laminated on the B layer.

In FIG. 1, layers A and B are alternately stacked. The C layer (for example, C ₁ , C ₂ , and C _n in the figure), which is a combination of the A layer and the B layer stacked alternately, has a thickness of 7 nm or more and 18 nm or less.

The above-mentioned "structure in which layers A and B layers are alternately laminated" means, for example, that the surface of layer A is in contact with the surface of layer B, and the surface of layer B is in contact with layer A. This means that the structure in which the surface opposite to the surface of the A layer is in contact with the surface of another A layer is repeated. In other words, it refers to a laminated structure in which a set of A layer and B layer is a repeating unit. For example, the structure is repeated in which the surface of the _A1 layer in the figure is in contact with the surface of the _B1 layer in the figure, and the surface of the _B1 layer, which is not in contact with the _A1 layer, is in contact with the _A2 layer.

As mentioned above, Al _x Cr _1-x N constituting the A layer has the advantage of being excellent in fracture resistance at low temperatures, but at high temperatures, the hardness and strength decrease due to the loss of N. It has the disadvantage of decreasing. Further, Ti _1-y Si _y N constituting the B layer has the advantage of being excellent in wear resistance and being suitable for high-speed cutting work, but has the disadvantage of being hard and brittle.

By making the C layer a thin layer with a thickness of 7 nm or more and 18 nm or less, it is possible to realize a hard coating that exhibits only the above-mentioned advantages and does not exhibit the above-mentioned defects. This point will be explained below.

By setting the thickness of the C layer to 7 nm or more and 18 nm or less, in the hard coating, one A layer is sandwiched between two B layers in a state in which thin C layers are laminated. Since one A layer is sandwiched between two B layers, only the side surfaces of the A layer are exposed. Since the C layer is a thin layer, the layer thickness on the side surface is extremely thin. Therefore, the N contained in the Al _x Cr _1-x N of the A layer is blocked from falling off by the Ti _1-y Si _y N even at high temperatures.

Further, by setting the thickness of the C layer to 7 nm or more and 18 nm or less, in the hard coating, one B layer is sandwiched between two A layers with thin C layers stacked. Since the C layer is a thin layer and one B layer is sandwiched between two A layers, the development of defects or cracks caused by the defects of Ti _1-y Si _y N is less likely to occur than Al _x Blocked by Cr _1-x N.

In this way, the defects of Al _x Cr _1-x N and Ti _1-y Si _y N are prevented from appearing in each C layer. Since the hard coating according to an embodiment of the present invention has a structure in which each C layer is laminated so that the above-mentioned defects are prevented from being exposed, the above-mentioned defects are not exposed in the hard coating as a whole, and only the above-mentioned advantages are maintained. can be expressed.

On the other hand, in the package structure described in Patent Document 1, for example, as mentioned above, the optimal layer thickness is 75 to 200 nm for the Al _y Cr _1-y N layer, preferably 120 to 170 nm, and the Ti _z Si _1- The thickness of _{the zN} layer is 50 to 150 nm, preferably 70 to 120 nm.

In such a configuration, due to the thick layer thickness, it may not be possible to sufficiently prevent N from falling off from the Al _y Cr _1-y N layer, or defects or cracks due to defects in the Ti _z Si _1-z N layer may occur. Progress cannot be adequately prevented. Further, the hard material layer described in Patent Document 1 has a plurality of mixed layers, but the mixed layer is a layer exhibiting average characteristics of AlCrN and TiSiN, or a drawback that either AlCrN or TiSiN has. This is the layer that is exposed.

The thickness of the C layer in one embodiment of the present invention is more preferably 9 nm or more and 17 nm or less, and even more preferably 11 nm or more and 15 nm or less. This makes it possible to more efficiently prevent the development of defects, cracks, etc. caused by the drop-off of N in Al _x Cr _1-x N and the aforementioned defects in Ti _1-y Si _y N.

In the hard coating according to one embodiment of the present invention, the thicknesses of the A layer and the B layer are each less than 10 nm.

In order for the hard coating to exhibit excellent wear resistance, heat resistance, chipping resistance, and high film strength, the A layer and the B layer must be contained in the C layer in a well-balanced manner. preferable. Therefore, the ratio of the thickness of the A layer to the thickness of the B layer in the thickness of the C layer is preferably 2:3 to 3:2, more preferably 4:5 to 5:4. Preferably, the ratio is 6:7, most preferably.

The total thickness of the C layer is 1 μm or more and 6 μm or less. That is, the hard coating has a structure in which a very large number of the C layers are laminated, that is, a super multilayer structure.

The hard coating has a structure in which a structure that can bring out only the advantages of Al _x Cr _1-x N and Ti _1-y Si _y N is repeated and laminated over a large number of layers. Therefore, the hard coating has excellent abrasion resistance, heat resistance, chipping resistance, and excellent film strength. Since the hard coating has these excellent properties, it can be processed on various materials from soft materials to hard materials (for example, hardness of 20 to 60 HRC), and can correspond to various processing conditions.

Therefore, it is possible to stably exhibit high performance under a wide range of processing conditions. The various processing conditions include conditions corresponding to processing temperatures ranging from low to high temperatures, conditions corresponding to processing methods such as wet processing, dry processing, and high-speed cutting.

The hard coating can be particularly preferably used for gear cutting. Gear cutting is the process of cutting steel or the like into a complicated gear shape, and machining a part of the gear shape with a large cut places a large load on the cutting tool blade. Furthermore, machining a gear-shaped part with a small cut places a load only on the cutting edge of the cutting tool. Therefore, hard coatings used in gear cutting are particularly required to have wear resistance, heat resistance, chipping resistance, and high strength.

If a hard coating has weak wear resistance, heat resistance, chipping resistance, or strength, the weak parts will not be able to withstand the harsh cutting conditions, resulting in a shortened cutting tool life and a reduction in machining efficiency. bring about a decline. As described above, the hard coating according to one embodiment of the present invention has excellent wear resistance, heat resistance, chipping resistance, and excellent film strength. Therefore, it can be suitably used for gear cutting. Of course, the hard coating is not limited to this, and the hard coating can also be suitably used for other processing purposes. For example, it can be suitably used as a hard coating for cemented carbide blades, drills, end mills, etc., which will be described later.

The total thickness of the C layer is more preferably 2 μm or more and 4.5 μm or less.

The hard coating may have a configuration in which a layer A, which does not form the C layer, is laminated subsequent to a layer B, which forms the C layer, at an end of the laminated structure. For example, an embodiment may be adopted in which a layer A is further laminated next to the B _n layer shown in FIG. Similarly, the hard coating may have a configuration in which a layer B, which does not form the layer C, is laminated subsequent to a layer A, which forms the layer C, at an end of the layered structure.

In this case, the structure is such that the A layer is sandwiched between two B layers, or the B layer is sandwiched between two A layers, so the Al _x Cr _1- Only the omission of N that _x N has and the advantage that Ti _1-y Si _y N has can be brought out.

The x of the Al _x Cr _1-x N is 0.6 or more and 0.7 or less, and the y of the Ti _1-y Si _y N is more than 0.05 and less than 0.08. In the hard coating according to an embodiment of the present invention, an A layer made of Al _x Cr _1-x N having the above composition and a B layer made of Ti _1-y Si _y N are formed such that the thickness of the C layer is 7 nm. The total thickness of the C layer is 1 μm or more and 6 μm or less. Thereby, the hard coating can exhibit the above-mentioned excellent wear resistance.

Al _x Cr _1-x N in which x is 0.6 or more and 0.7 or less can be prepared by controlling the composition of the raw material AlCr target, the pressure of N ₂ when forming the C layer, the bias voltage, etc. . Furthermore, Ti _1-y Si _y N in which y is more than 0.05 and less than 0.08 can be similarly prepared by controlling the composition of the raw material TiSi target, the pressure of N ₂ during the formation of the C layer, the bias voltage, etc. can do.

In addition, x of the prepared Al _x Cr _1-x N is 0.6 or more and 0.7 or less, and y of Ti _1-y Si _y N is more than 0.05 and less than 0.08. , can be confirmed by an EDX analyzer attached to SEM and/or TEM.

The hard film according to one embodiment of the present invention can be manufactured, for example, by a method of applying arc ion plating to a base material. As an apparatus that can be used in this method, for example, a vacuum film forming apparatus such as an arc evaporator (manufactured by Nippon ITF Co., Ltd.) equipped with a Stair One evaporation source can be mentioned.

FIG. 2 is a longitudinal sectional view schematically showing an example of the structure of the arc evaporator. FIG. 3 is a top view of the arc evaporator shown in FIG. 2, viewed from vertically above. In the figure, 20 is an arc evaporation device, 21 is a Cr evaporation source, 22 is an Al _x Cr _1-x arc evaporation source, 23 is a Ti _1-y Si _y arc evaporation source, 24 is a rotary table, and 25 is a small table. , 26 is an arc power supply, and 27 is a bias power supply. Since the small table 25 is connected to the rotary table 24 by a gear, it rotates when the rotary table 24 rotates. The gear ratio between the rotary table 24 and the small table 25 is preferably a value greater than 6 and not an integer when the number of gears of the small table 25 is 1.

The interior of the arc evaporator 20 is a vacuum chamber. An example of a method for manufacturing a cutting tool by coating a base material with a hard coating according to an embodiment of the present invention using the arc evaporator 20 will be described below. Note that this method is also used in Examples described later.

First, the rotary table 24 on which the base material 11 is placed on the small table 25 is installed inside the arc evaporator 20 (inside the furnace).

Next, the inside of the arc evaporator 20 is brought to a specified degree of vacuum, and the base material 11 is heated by a heater (not shown) until the temperature reaches 400°C. Subsequently, as shown in FIG. 3, argon gas is introduced into the furnace, and the pressure inside the furnace is set to 1 Pa. Thereafter, a bias voltage of -900V is applied to the base material 11 by the bias power supply 27, and the base material 11 is etched with argon ions. After exhausting the argon gas, nitrogen gas is introduced into the furnace as shown in FIG. 3, and the pressure inside the furnace is set to 4 Pa.

Next, by operating the arc power supply 26, Al _x Cr _1-x is arc-discharged from the arc evaporation source 22 at 150A, and Ti _1-y Si _y is arc-discharged from the arc evaporation source 23 at 140A. As a result, Al _x Cr _1-x and Ti _1-y Si _y are evaporated in the nitrogen gas atmosphere.

Since the rotary table 24 is rotating and the base material 11 is rotating, when the base material 11 directly faces the arc evaporation source 22, Al _x Cr _1-x is deposited on the base material 11 and at the same time the Combined with nitrogen gas, a film of Al _x Cr _1-x N is formed on the surface of the base material 11 .

On the other hand, when the base material 11 directly faces the arc evaporation source 23, Ti _1-y Si _y is evaporated onto the base material 11 and simultaneously combines with the nitrogen gas, and the Ti _1-y Si _y N film forms a base material. A film is formed on the surface of the material 11.

By repeating the above operations, a hard coating according to an embodiment of the present invention can be formed on the surface of the base material 11. At this time, by applying a bias voltage to the base material 11, ions of the evaporated metal elements (Ti, Si, Al, Cr) are strongly drawn into the base material 11, making the film denser, and increasing the strength of the hard film and reducing the residual Adjust stress.

The thickness of the C layer and the total thickness of the C layer can be controlled to be 7 nm or more and 18 nm or less and 1 μm or more and 6 μm or less, respectively, by adjusting the arc current and the rotation speed of the rotary table 24.

After forming a hard coating having a predetermined C layer thickness and a total C layer thickness, the furnace is cooled until the temperature inside the furnace is 200°C or less, and the inside of the furnace is opened to the atmosphere, and the manufactured cutting Take out the tools.

That the manufactured hard coating has a predetermined structure can be confirmed by observing a longitudinal section of the hard coating using, for example, a scanning transmission electron microscope. The predetermined structure has a structure in which layers A and B are alternately stacked, the thickness of the C layer is 7 nm or more and 18 nm or less, and the total thickness of the C layers is 1 μm or more and 6 μm. The structure is as follows. For example, based on the observation results shown in FIG. 9, which will be described later, the total thickness of 10 to 20 consecutive layers is measured and divided by the number of combinations of layer A and layer B. Thickness can be calculated. The thickness of layer A and the thickness of layer B can be determined by measuring the thickness of about 5 to 10 layers and calculating the average value.

In the hard coating according to an embodiment of the present invention, in the X-ray diffraction pattern of the hard coating, the ratio (A/B) of the sub-peak intensity (A) to the main peak intensity (B) is 0.4 or more. It is preferably 0.75 or less.

The main peak is a crystal peak of the A layer and the B layer. The sub-peak is a peak that appears near the main peak (near the low-angle side and high-angle side of the main peak in the X-ray diffraction pattern), and is a peak resulting from the super multilayer structure. The ratio is an indicator that the hard coating has the super multilayer structure.

The X-ray diffraction pattern can be obtained, for example, by performing X-ray diffraction measurement of the hard coating using the θ-2θ method under the following conditions. The conditions are as follows: Measuring device: Bruker AXS X-ray diffractometer D8 DISCOVER, X-ray source: Cu-Kα, tube voltage: 40 kV, tube current: 40 mA, slit width: 0.5°, one-dimensional detector, step: 0.02°, integration time: 0.6 seconds, scan range 2θ=30 to 50°. Hereinafter, a method for determining the ratio (A/B) will be explained.

FIG. 4 shows the X-ray diffraction patterns obtained by subjecting two types of cutting tools (Sample 1 and Sample 2) each having a hard film made of a laminated layer of AlCrN and TiSiN to X-ray diffraction. FIG. 5 is an enlarged view of the vicinity of 2θ=34° to 40° in FIG. 4.

First, as shown in FIG. 5, a straight line is drawn for each of Sample 1 and Sample 2 to connect the intensity at 2θ=34° and the intensity at 2θ=39°. Next, subpeak 1 near 36°, peak of TiSIN (111) plane near 36.5°, peak of AlCrN (111) plane near 37.3°, and subpeak 2 near 37.8°, , the difference from the straight line (the length of the vertical straight line shown in the figure) is defined as the intensity I1, I2, I3, and I4 of each peak. Then, let (I1+I4)/(I2+I3) be the ratio (A/B). Table 1 shows the results of determining the ratios for Sample 1 and Sample 2 shown in FIG.

FIG. 6 shows the X-ray diffraction patterns obtained by subjecting three types of cutting tools (Samples 3 to 5) each having a hard coating made of a laminated layer of AlCrN and TiSiN to X-ray diffraction. FIG. 7 is an enlarged view around 2θ=34° to 40° in FIG. 6. The straight line shown in FIG. 7 was drawn, and the ratio (A/B) was determined in the same manner as described for Samples 1 and 2. The results are shown in Table 2.

The ratio is more preferably 0.45 or more and 0.72 or less, and even more preferably 0.5 or more and 0.55 or less. This can serve as a more useful indicator that the hard coating has the super multilayer structure.

The hard coating according to an embodiment of the present invention preferably has a compressive stress of −0.5 GPa or more and −4.0 GPa or less. According to this configuration, the hard coating has strong resistance to impact and is not easily destroyed. From this point of view, the compressive stress is more preferably -1 GPa or more and -3 GPa or less, and even more preferably -1.5 GPa or more and -2.5 GPa or less. The compressive stress can be measured, for example, by a sin ² φ method using X-ray diffraction, or a measurement method based on Stoney's equation using a test piece.

The hard coating according to one embodiment of the present invention preferably has a surface roughness Ra of 0.03 μm or more and 0.18 μm or less. If the surface roughness Ra exceeds 0.18 μm, unevenness will occur not only on the surface of the hard coating but also inside, making it difficult to form the super multilayer structure. Furthermore, the sub-peaks are less likely to be found in the X-ray diffraction pattern. The lower the lower limit value of the surface roughness Ra, the better, but the practical lower limit value is 0.03 μm.

Therefore, the fact that the hard coating has a surface roughness Ra of 0.03 μm or more and 0.18 μm or less is an indicator that the hard coating according to an embodiment of the present invention has the super multilayer structure. Further, according to the above configuration, it can be said that the surface smoothness of the hard coating is extremely high.

Therefore, the hard coating can stably exhibit high performance under a wide range of processing conditions, and has high smoothness, so it can improve the quality of the workpiece.

From this viewpoint, the surface roughness Ra of the hard coating is more preferably 0.06 μm or more and 0.15 μm or less, and even more preferably 0.08 μm or more and 0.14 μm or less.

The surface roughness Ra can be measured, for example, by the following method. That is, a method may be mentioned in which the surface of a test piece with a sufficiently small surface roughness Ra is coated with the hard film using an ion plating method or the like, and the surface roughness Ra of the coated test piece is measured. can.

Examples of the test piece include a test piece having a surface roughness Ra of 0.01 μm or less. Since the test piece has a sufficiently small surface roughness Ra, the surface roughness Ra of the test piece covered with the hard coating can be regarded as the surface roughness Ra of the hard coating.

Moreover, as another method of measuring the surface roughness Ra, the following method can be mentioned, for example. That is, a longitudinal cross section of a cutting tool whose surface is coated with a base material by ion plating or the like is prepared. Next, using a scanning electron microscope, the shape of the interface between the hard coating and the base material is taken out as a profile of the base material surface, and Ra is calculated according to the Ra calculation method. Similarly, the shape of the hard coating surface is extracted as a film surface profile, and Ra is calculated according to the Ra calculation method. The value obtained by subtracting the Ra of the base material surface from the Ra of the film surface is defined as the Ra of the hard coating.

Note that Ra can be measured using, for example, a surface roughness measuring machine manufactured by DEKTAK.

The hard coating according to one embodiment of the present invention preferably has a nanoindentation hardness of 35 GPa or more and 40 GPa or less.

According to this configuration, the hard coating has sufficient strength. Therefore, it has sufficient resistance to machining of materials with high hardness, so it can contribute to improving the sharpness of cutting tools, improving the ability to discharge chips, etc.

The nanoindentation hardness can be measured by, for example, using a Nanoindenter ENT-1100 manufactured by Elionix Co., Ltd. as a measuring device and applying a load of 2 g to the hard coating provided on the surface of the cutting tool using a Berkovich indenter. I can do it.

[Embodiment 2: Cutting tool]
A cutting tool according to an embodiment of the present invention includes a base material and a hard coating coating a surface of the base material, and the hard coating is a hard coating according to an embodiment of the present invention.

Examples of the cutting tools include hobs, cemented carbide blades, broaches, flat rolling dies, shaving cutters, gear cutting tools such as pinion cutters; drills; end mills; taps, thread cutting dies, chasers, thread milling cutters, and thread mills. Examples include thread cutting tools such as molding dies; indexable tools such as inserts; wear-resistant tools such as drawing tools, rolling tools, shearing tools, forging tools, molds, tools for electronic related parts, and machine attachment parts.

The hard coating according to one embodiment of the present invention has not only wear resistance, heat resistance, chipping resistance, and high hardness, but all of these properties in a well-balanced manner. Therefore, the cutting tool can be used with a wide range of workpiece materials having a hardness of 20 to 60 HRC, for example.

In recent years, the usage conditions for gear cutting tools are increasing, such as high-speed machining and dry machining, which tends to increase the impact that the cutting edge receives and the temperature of the cutting edge. Further, a gear cutting tool has a large number of cutting edges, such as a hob, but due to the characteristics of gear cutting, the load applied to the cutting edge changes from one cutting edge to another.

Therefore, a cutting tool provided with a hard coating that is weak in any of the above properties cannot be stably used under the above usage conditions. Furthermore, the cutting tool cannot be used as a gear cutting tool because it cannot cope with loads that vary from cutting edge to cutting edge. Since the cutting tool according to one embodiment of the present invention has all of the above characteristics in a well-balanced manner, it can operate stably even under the above usage conditions. Moreover, it can be suitably used as a gear cutting tool.

The cutting tool can be obtained by forming the hard coating on a base material by a method such as arc ion plating. As other methods, sputtering methods such as HiPIMS (high power pulse sputtering), vapor deposition methods, etc. can also be used.

As the base material, high speed steel, cemented carbide, etc. can be used. Examples of the cemented carbide include WC-Co alloy, WC-TiC-Co alloy, WC-TaC-Co alloy, WC-TiC-TaC-Co alloy, WC-Ni alloy, and WC-Ni-Cr. A series alloy etc. can be used.

〔summary〕
The present invention includes the following aspects.
<1>
It has a structure in which layers A made of Al _x Cr _1-x N and layers B made of Ti _1-y Si _y N are alternately laminated,
When a combination of the A layer and the B layer stacked alternately is a C layer, the thickness of the C layer is 7 nm or more and 18 nm or less,
The total thickness of the C layer is 1 μm or more and 6 μm or less,
A hard coating, wherein the thickness of the A layer and the B layer are each less than 10 nm.

(Here, the x is 0.6 or more and 0.7 or less, and the y is more than 0.05 and less than 0.08.)
<2>
In the X-ray diffraction pattern of the hard coating, the ratio (A/B) of the sub-peak intensity (A) to the main peak intensity (B) is 0.4 or more and 0.75 or less, described in <1>. hard coating.
<3>
The hard coating according to <1> or <2>, having a compressive stress of -0.5 GPa or more and -4.0 GPa or less.
<4>
The hard coating according to any one of <1> to <3>, which has a surface roughness Ra of 0.03 μm or more and 0.18 μm or less.
<5>
A cutting tool comprising a base material and a hard coating coating a surface of the base material, wherein the hard coating is the hard coating according to any one of <1> to <4>.
<6>
The cutting tool according to <5>, wherein the cutting tool is a gear cutting tool.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. are also included within the technical scope of the present invention.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Examples 1 to 13]
(1) Manufacturing a cutting tool with a hard coating according to an embodiment of the present invention Based on the method described above with reference to FIGS. 2 and 3 using the arc evaporator 20 shown in FIGS. 2 and 3, A cutting tool provided with a hard coating according to an embodiment of the present invention was manufactured. The base materials include a high-speed steel hob; a 20 mm square, 2 mm thick high-speed steel test piece with a mirror-wrapped surface (surface roughness Ra = 0.01 μm or less); a 10 mm width, 20 mm length, and 1 mm thick A hard metal test piece was used. In this example, a total of 13 hobs each having a diameter of 80 mm and a length of 150 mm were manufactured. These are referred to as cutting tools according to Examples 1 to 13.

When cutting tools according to Examples 1 to 13 were prepared, x of Al _x Cr _1-x arc-discharged from the arc evaporation source 22 was 0.6 or more and 0.7 or less (Table 3). "Al composition" column). Further, y of Ti _1-y Si _y arc-discharged from the arc evaporation source 23 was more than 0.05 and less than 0.08 ("Si composition" column in Table 3). The composition ratios (atm%) of Al and Cr in layer A (layer consisting of Al _x Cr _1-x N) and Ti and Cr in layer B (layer consisting of Ti _1-y Si _y N) of the obtained hard coating. Table 3 shows the Si composition ratio (atm%). Table 3 also shows the thickness of layer C, the thickness of the hard coating (total thickness of layer C), and the number of layers (sum of the number of layers A and B).

For each example, the high speed steel test piece and the cemented carbide test piece were also subjected to the method at the same time as each example. The atm %, the thickness of the C layer, the total thickness of the C layer, and the number of layers of the hard coatings formed on these test pieces were the same as the hard coatings obtained in the corresponding examples.

FIG. 8 shows the results (bright field image, magnification: 50,000 times) of a longitudinal section of the hard coating of one of the cutting tools obtained in the example, observed using a scanning transmission electron microscope (STEM).

FIG. 9 is a diagram showing the results of observing the hard coating shown in FIG. 8 at a magnification of 1,000,000 times. As shown in FIG. 9, it can be seen that a regular laminated structure is well formed. Based on the observation results shown in Figure 9, calculate the thickness of layer C by measuring the total thickness of 10 to 20 consecutive layers and dividing by the number of combinations of layer A and layer B. be able to. Regarding the hard coatings obtained in Examples 1 to 13 and Comparative Examples 1 to 4, the thickness of the C layer was calculated based on the observation results by STEM. The total thickness of the C layer was determined by measuring the total thickness of the C layer observed by the STEM.

(2) X-ray diffraction The hobs obtained in Examples 1 to 13 were subjected to X-ray diffraction, and measurements were performed using the θ-2θ method under the following conditions. The conditions are: measurement device: Bruker AXS X-ray diffraction device D8 DISCOVER, X-ray source: Cu-Kα, tube voltage: 40 kV, tube current: 40 mA, slit width: 0.5°, step: 0.02°, Integration time: 0.6 seconds, scan range 2θ=30 to 50°. Next, from the X-ray diffraction pattern obtained for each hob, the ratio of the subpeak intensity (A) to the main peak intensity (B) ( A/B) was calculated. The results are shown in Table 3.

(3) Measurement of surface roughness Ra of hard coating The surface roughness Ra of the surface coated test pieces made of high speed steel obtained at the same time as Examples 1 to 13 was measured using a surface roughness measuring machine manufactured by DEKTAK, The surface roughness of the hard coating was defined as Ra. The results are shown in Table 3.

(4) Measurement of nanoindentation hardness of hard coating Each cutting tool was prepared on the surface of the hob obtained in Examples 1 to 13 using a Berkovich indenter using a nanoindenter ENT-1100 manufactured by Elionix Co., Ltd. A load of 2 g was applied to the hard coating, and the nanoindentation hardness of the hard coating was measured. The results are shown in Table 3.

(5) Measurement of compressive stress The warpage of the cemented carbide surface coated test pieces obtained in Examples 1 to 13 was measured using a surface roughness measuring machine manufactured by DEKTAK, and the warpage was measured based on Stoney's formula. The compressive stress was measured. The results are shown in Table 3.

(6) Cutting test 1
The hobs obtained in Examples 1 to 7 were subjected to dry machining using SCM415 gears under the conditions of cutting speed (V) = 180 m/min, feed rate of 2.5 mm/rev., and climb cut. . Every time 100 pieces were processed, the wear width of the cutting edge was confirmed using a microscope. The results were evaluated based on the number of machining operations until the wear width exceeded 0.2 mm or the cutting edge was damaged. The results are shown in Table 3.

(7) Cutting test 2
The hobs obtained in Examples 8 to 13 were subjected to dry machining using SCR420H gears under the conditions of cutting speed (V) = 160 m/min, feed rate of 1.5 mm/rev., and climb cut. . Every time 100 pieces were processed, the wear width of the cutting edge was confirmed using a microscope. The results were evaluated based on the number of machining operations until the wear width exceeded 0.2 mm or the cutting edge was damaged. The results are shown in Table 3.

[Comparative Examples 1 to 4]
Layer A and layer B having the compositions shown in Table 3 were prepared using the same method as in Examples 1 to 13. A hob made of high speed steel; a 20 mm square, 2 mm thick test piece made of high speed steel with a mirror-wrapped surface; width 10 mm, length A film was formed on a test piece made of cemented carbide with a diameter of 20 mm and a thickness of 1 mm. As a result, hobs and test pieces were obtained in which the thickness of the C layer, the total thickness of the C layer, and the number of layers were as shown in Table 3.

When the cutting tools according to Comparative Examples 1 to 4 were prepared, x of Al _x Cr _1-x arc-discharged from the arc evaporation source 22 was the value listed in the "Al composition" column of Table 3. Ta. Furthermore, y of Ti _1-y Si _y arc-discharged from the arc evaporation source 23 was the value listed in the "Si composition" column of Table 3, respectively. In Comparative Examples 3 and 4, the arc current and the rotation speed of the rotary table 25 were changed from Examples 1 to 13 and Comparative Examples 1 and 2, and the C layer thickness was set to less than 7 nm or more than 18 nm.

The hob was subjected to X-ray diffraction, nanoindentation hardness measurement of the hard coating, and cutting test 1 in the same manner as in Examples 1 to 13. Furthermore, the surface roughness Ra was measured using the surface-coated test piece made of high speed steel, and the compressive stress was measured using the surface-coated test piece made of cemented carbide. The results are shown in Table 3.

"Sub-peak intensity ratio" is the ratio (A/B) between sub-peak intensity (A) and main peak intensity (B) in the X-ray diffraction pattern of the hard coating, and "film hardness" is This is the nanoindentation hardness of the hard coating.

Comparative Example 1 has a Si composition of 5.0 atm%, which does not exceed 5 atm%. In Comparative Example 2, the Si composition is 8.0 atm% and is not less than 8 atm%. Comparative Example 3 has a C layer thickness of 5 nm, which does not satisfy the requirement of 7 nm or more and 18 nm or less. Comparative Example 4 has a C layer thickness of 20 nm, which does not satisfy the requirement of 7 nm or more and 18 nm or less.

The hobs described in Comparative Examples 1 to 4 have subpeak intensity ratios and surface roughness Ra comparable to those of Examples, but the results of Cutting Test 1 are clearly inferior to those of Examples. This is considered to be because the hard coating according to one embodiment of the present invention does not satisfy the requirements.

On the other hand, in the hob described in Examples 1 to 13, the total of the Al composition, Cr composition, Ti composition, Si composition, C layer thickness, and C layer thickness that the hard coating according to one embodiment of the present invention should have Satisfy all of the following. As a result, the cutting test results were very good.

As described above, the hard coating according to an embodiment of the present invention has a structure in which "A layer made of Al _x Cr _1-x N and a B layer made of Ti _1-y Si _y N are alternately laminated." and when a combination of the A layer and the B layer which are alternately laminated is taken as a C layer, the thickness of the C layer is 7 nm or more and 18 nm or less, and the thickness of the C layer is The total thickness is 1 μm or more and 6 μm or less, and the thickness of the A layer and the B layer is each less than 10 nm (here, the x is 0.6 or more and 0.7 or less, and the y is 0.05 It is possible to provide a hard coating that has excellent abrasion resistance, heat resistance, chipping resistance, and excellent film strength. I understand.

INDUSTRIAL APPLICATION This invention can be suitably utilized for the cutting tool used under wide range of processing conditions.

10... Cutting tool 11... Base material 12... Hard coating A ₁ - A _n ... A layer B ₁ - B _n ... B layer C ₁ - C _n ... C layer 20. ... Arc evaporation device 21 ... Cr evaporation source 22 ... Arc evaporation source of Al _x Cr _1-x 23 ... Arc evaporation source of Ti _1-y Si _y 24 ... Rotary table 25 ... Small table 26...Arc power supply 27...Bias power supply

Claims (6)

It has a structure in which layers A made of Al _x Cr _1-x N and layers B made of Ti _1-y Si _y N are alternately laminated,
When a combination of the A layer and the B layer stacked alternately is a C layer, the thickness of the C layer is 7 nm or more and 18 nm or less,
The total thickness of the C layer is 1 μm or more and 6 μm or less,
A hard coating, wherein the thickness of the A layer and the B layer are each less than 10 nm.
(Here, the x is 0.6 or more and 0.7 or less, and the y is more than 0.05 and less than 0.08.) According to claim 1, in the X-ray diffraction pattern of the hard coating, the ratio (A/B) of the sub-peak intensity (A) to the main peak intensity (B) is 0.4 or more and 0.75 or less. hard coating. The hard coating according to claim 1, having a compressive stress of -0.5 GPa or more and -4.0 GPa or less. The hard coating according to claim 1, having a surface roughness Ra of 0.03 μm or more and 0.18 μm or less. A cutting tool comprising a base material and a hard coating covering a surface of the base material, the hard coating being the hard coating according to any one of claims 1 to 4. The cutting tool according to claim 5, wherein the cutting tool is a gear cutting tool.

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