JP2008238281A - Coated tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a performance of high hardness of a boride coating without sacrificing a tight-contact characteristic of the coating by controlling a maximum diffraction intensity of X-ray diffraction. <P>SOLUTION: In this coated tool, a boride coating made of one or more kinds of metal elements selected from Al, Si, Cr, W, Ti, Nb and Zr is coated on a substrate surface. The boride coating has a hexagonal crystal structure, and has a maximum diffraction intensity in X-ray diffraction on a (001) face, and a residual compression stress is 0.1 GPa or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a performance improvement for increasing the hardness of a boride film without sacrificing the adhesion properties of the film.

  Techniques relating to the boride film are disclosed in Patent Documents 1 and 2 and Non-Patent Document 3.

JP 2006-26833 A JP 2002-263913 A N. Panich, Y.M. Sun, Thin Solid Films, 500 (2006) 190-196

  An object of the present invention is to control the strongest diffraction intensity by X-ray diffraction and improve the performance of the boride film to increase the hardness without sacrificing the adhesion characteristics of the film.

  The present invention relates to a coated tool in which a boride film made of one or more metal elements selected from Al, Si, Cr, W, Ti, Nb, and Zr is coated on the surface of a substrate. A coated tool characterized by having a crystal structure, having the strongest diffraction intensity in the (001) plane in X-ray diffraction, and having a residual compressive stress of 0.1 GPa or more. By adopting the above configuration and controlling the strongest diffraction intensity by X-ray diffraction, it was possible to improve the performance of increasing the hardness of the boride film without sacrificing the adhesion characteristics of the film.

  In the coated tool of the present invention, the diffraction intensity of the (001) plane in the X-ray diffraction of the boride film is I (001), the diffraction intensity of (111) is I (111), and I (001) / I (111) When I is the Ia value, 7 ≦ Ia ≦ 25, and when the diffraction intensity of (101) is I (101) and I (101) / I (111) is the Ib value, 0.1 It is preferable that ≦ Ib ≦ 1. Further, the half width Hw value of the (001) plane in the X-ray diffraction of the boride film is 0.6 ≦ Hw ≦ 1.1, and I (001)> I (111)> I (101) Preferably there is.

  The coated tool coated with the boride film of the present invention controls the strongest diffraction intensity by X-ray diffraction, and improves the performance to increase the hardness of the boride film without sacrificing the adhesion characteristics of the film. Can do.

In the present invention, by controlling the strongest diffraction intensity by X-ray diffraction from the crystal orientation of the boride film coated on the tool base, a stable high residual compressive stress can be obtained without sacrificing the adhesion characteristics of the film. It is to coat the boride film having. As a result, the wear resistance of the tool has been dramatically improved. The present invention is a boride film made of one or more metal elements selected from Al, Si, Cr, W, Ti, Nb, and Zr, and has a hexagonal crystal structure. These metal elements are effective elements for increasing the hardness of the boride film. In particular, Si, W, and Ti are effective for increasing the hardness of the film. Ti boride has the highest hardness, but tends to have poor oxidation resistance. Therefore, it is effective to add (Ti, Al) B2, (Ti, Cr) B2, etc. in combination. It is an effective form that the boride film is a composite boride. In addition, since the boride film has excellent lubrication characteristics, the wear resistance of the coated tool can be improved. Ti and Zr boride coatings have higher thermal conductivity than conventional nitride coatings and carbide coatings in the high temperature range of about 800 to 1000 ° C. corresponding to the cutting temperature. It is also effective for avoiding welding, cutting edge deformation, etc. by escaping inward. Al, Nb, Cr, and Zr improve oxidation resistance, and W is effective in improving lubricity. For example, when a cemented carbide is used as the base material, Al and W are effective in preventing Co diffusion from the base material. Further, the hardness can be increased by controlling the strongest diffraction intensity of the boride film having a hexagonal crystal structure to the (001) plane. In X-ray diffraction, the reason why the film is hardened by controlling the strongest diffraction intensity to the (001) plane is considered as follows. In general, the hexagonal crystal structure is a crystal structure in which a boron atom is located at the center of a triangular prism composed of metal atoms, and layers formed by these metal atoms and layers formed by boron atoms are alternately stacked. The bonding strength between these layers is relatively weak. Therefore, in the present invention, it is considered that the boride film is remarkably increased in hardness by controlling the boride film to grow preferentially in the layer direction. Controlling the strongest diffraction intensity to the (001) plane is to control the (001) plane and the approaching direction of the coating hardness measurement indenter to be substantially perpendicular, and thereby the characteristics of the (001) plane. The hardness which is can be utilized effectively. On the other hand, when the (001) plane, which is a hexagonal slip plane, is tilted by about 45 degrees from the direction in which the measurement indenter enters, the strongest diffraction intensity does not become the (001) plane, and is subjected to the maximum shear stress and has high hardness. It is difficult to make it easier. Each indexing in the present invention was determined by a JCPDS card. The distance between the (111) plane and the (102) plane is extremely close to 0.13717 nm and 0.13751 nm, respectively, and it is difficult to separate them. Therefore, in the present invention, the theoretical intensity is slightly high (111) plane. It was.
In the present invention, for example, the crystal orientation of the boride film can be controlled by the physical vapor deposition (hereinafter referred to as PVD) method, and the surface giving the strongest diffraction intensity by X-ray diffraction can also be controlled. The boride film of the present invention can achieve a hardness of 45 to 75 GPa. When the hardness X of the boride film is less than 45 GPa, the wear resistance tends to decrease. If it exceeds 75 GPa, the residual compressive stress becomes too high, the adhesion strength is lowered, and the film is easily peeled off. As a result, tool wear tends to increase. In particular, when the hardness is 65 to 73 GPa, the balance between the residual compressive stress and the film hardness is optimal, and the adhesion strength is excellent, and at the same time, the wear resistance is also excellent. Here, the hardness can be measured by a nanoindentation method. The residual compressive stress of the present invention is 0.1 GPa or more. The reason for this is to control the crystal orientation and to increase the hardness of the film without sacrificing the adhesion properties of the film.

  The Ia value F of the present invention is preferably 7 ≦ Ia ≦ 25. The reason is that when the Ia value is 7 to 25, the residual compressive stress is high and the wear resistance is excellent. When the Ia value is less than 7, the hardness of the boride film is not sufficient, and when it exceeds 25, the residual compressive stress becomes too high, and the adhesion strength tends to be poor and peeling tends to occur. The Ib value is preferably 0.1 ≦ Ib ≦ 1. The reason for this is that when the Ib value is less than 0.1, the compressive stress remaining in the film tends to be high and the adhesion tends to decrease, and when it exceeds 1, the crystallinity decreases and the hardness of the film decreases. Tend to. The Hw value is preferably 0.6 ≦ Hw ≦ 1.1. The boride film of the present invention is preferable because I (001)> I (111)> I (101) is effective in increasing the hardness of the boride film.

  The present invention has excellent wear resistance and lubrication characteristics even with a single layer. By laminating two or more layers of a boride film, nitride, and carbide, the oxidation resistance is improved and the characteristics of the boride film can be exhibited effectively, which is preferable. When the layers are alternately stacked, the layers may be alternately stacked with a thickness of several nm. By coating the nitride film on the interface between the boride film and the substrate, the adhesion strength with the substrate can be improved, which is preferable. A carbide film is preferable because it is particularly effective for improving lubricity. The area ratio of the macroparticles present on the surface of the boride coating of the present invention is preferably 5% or less, which is preferable because the adhesion resistance of the tool is lowered. Among PVD methods, the abundance ratio of macro particles can be reduced to 1% or less by sputtering. After the coating treatment, the macroparticles adhering to the coating surface are mechanically removed, whereby the area ratio of the macroparticles can be reduced. The macro particles here are attached particles having a convex shape with respect to the coating surface, and the core is mainly composed of a metal component. The area ratio of macro particles can be photographed with a scanning electron microscope at a magnification of 3k, and the area of convex macro particles can be quantified by image analysis processing. The boride film of the present invention preferably contains less than 5 atomic% of Ar and Kr. By containing Ar and Kr, the bombardment effect at the time of coating is improved, the hardness of the coating is improved and the coating surface becomes smoother, and the wear resistance and adhesion resistance of the tool can be improved. Since Ar and Kr are present in the crystal grain boundaries, the residual compressive stress tends to be relaxed without reducing the hardness of the film, so that chipping is reduced. If the contents of Ar and Kr are more than 5%, the hardness of the film is greatly lowered and the wear resistance is lowered. Furthermore, it escapes out of the film under a high temperature environment, promotes oxygen diffusion, and decreases oxidation resistance. In particular, the content of Ar and Kr is preferably 0.01 to 0.8%. The presence and quantification of Ar and Kr can be analyzed by electron probe microanalyzer analysis and Auger electron spectroscopy analysis.

  The tool coated with the boride film of the present invention has a long life. The tool base is preferably cemented carbide, cermet, high speed steel, cubic boron nitride sintered body, die steel or the like. Examples of the tool include an end mill, a drill, a reamer, a tap, a broach, a hob, a cutter, a small diameter drill, a cutting tool such as a router, an insert, a die, a punch, and the like. The present invention is particularly excellent in adhesion strength with the base material, and is effective in extending the tool life. The cemented carbide has a Co content of less than 3 to 12% by weight. If it is less than 3%, sudden chipping or chipping of the cutting edge may occur. On the other hand, if it exceeds 12%, the covering effect is not preferred. Hereinafter, the present invention will be described based on examples.

Example 1
The present invention employs a PVD method in which a bias voltage is applied to a tool substrate, and controls the crystal orientation of the film while increasing the ionization rate during film formation, thereby stably forming a high hardness boride film. Can be coated. In this respect, a coating method by a sputtering method is preferable, but an arc discharge ion plating (hereinafter, referred to as AIP) method can be used in combination for a multilayer coating. In the sputtering method, a boride film having stable characteristics can be coated using a direct current power source. A sputtering power source and a bias power source can be selected from a DC power source, a high frequency power source, and a pulse power source and used in combination. Further, it is preferable to dispose the electrode in the vicinity of the base material in order to promote ionization, whereby the ionization of each element is further promoted and the crystallinity of the film can be controlled. In particular, the film formation is preferably performed by providing an independent anode in a vacuum vessel. A normal film forming apparatus uses a vacuum vessel wall as an anode. In the present application, an independent anode is provided at a position opposite to the evaporation source to increase the electron movement distance. As a result, the plasma activity was increased, the crystallinity of the boride film was improved, and the film could be hardened. 1 and 2 show a film forming apparatus coated with the boride film of the present invention. The film forming apparatus is a film forming apparatus on which three sputtering evaporation sources 3, 4, and 5 are mounted. A power source 6 is connected to the sputtering evaporation source 4 and the anode 7, and they are installed at positions facing each other. Although not shown in the drawing, the evaporation sources 3 and 5 are also connected to different power sources in the same manner. The vacuum vessel 1 is evacuated by a turbo molecular pump and a rotary pump, and Ar is introduced from a gas supply port 10. The evaporation source 4 was loaded with a boride target. The bias power source 8 is connected to the base material 2 and independently applies a negative bias voltage to the base material. The base material 2 rotates once per minute, and a fixing jig and a sample holder are installed on the base material 2 and revolves and revolves. The distance between the substrate 2 and the target surface placed on the evaporation sources 3, 4, 5 was 50 mm. As a sample for evaluating the characteristics of the coating, a test piece having an SNMN432 shape made of ultrafine cemented carbide with a Co content of 10% by weight subjected to mirror finishing was prepared. The tool sample was a four-blade square end mill and a two-blade ball end mill made of ultrafine cemented carbide with a Co content of 8% by weight, each of which was thoroughly degreased and placed in a vacuum vessel. The coating conditions were as follows: the substrate temperature was 500 ° C. by heating the heater, the exhaust 9 was performed and the internal pressure of the container reached 4 × 10 −3 Pa. Then, Ar gas was introduced into the vacuum container, and a bias of −400 V was applied to the base 2 The substrate was cleaned with ions by applying a voltage for 30 minutes. Next, electric power was supplied from the power source 6 so that the evaporation source 4 was a cathode and the electrode 7 was an anode, and discharging was started. The cathode power was set to 4 kW. At the same time, a bias voltage was applied to the substrate 2 to coat the boride film with about 2 μm. In order to evaluate the various characteristics of the boride film of the present invention, the boride target composition, bias voltage, film forming temperature, Ar flow rate, and presence / absence of anode installation were changed. After cooling, the sample was taken out and subjected to various evaluations. Table 1 shows film formation parameters.

  For measuring the film hardness, an Elionix nanoindentation apparatus was used. The specimen was tilted 5 degrees, and after mirror polishing, a region where the maximum indentation depth was less than about 1/10 of the film thickness was selected within the polished surface of the film. At this time, there was no influence of the substrate even at about 1/5. Ten points were measured under the measurement conditions of an indentation load of 49 mN, a maximum load holding time of 1 second, and a removal speed after loading of 0.49 mN / second, and the average value was obtained. The film hardness in this measurement method is easily influenced by the fine shape of the indenter, the temperature and humidity at the time of measurement, and the surface state of the sample, and the obtained numerical values do not necessarily match the Vickers hardness. Therefore, single crystal Si was measured simultaneously. The film hardness of the single crystal Si at that time was 15 GPa. Therefore, a relative comparison can be made based on the measurement results. Next, the friction and wear characteristics of the boride film were measured. The evaluation conditions were ball-on-disk type wear tester, load 5N, rotation radius 3mm, rotation speed 3cm / sec, disk coated substrate, ball 6mm diameter SUJ2, friction coefficient measurement, and iron The adhesion state and the friction of the film were measured. Furthermore, the adhesion of the boride film was evaluated. Indentation was made from the coated surface with Rockwell C scale, and the peeled state around the indentation was observed with an optical microscope. The case where peeling was not observed was A, the case where peeling was observed around the entire indentation was C, and the intermediate peeling state was B. These evaluation results are also shown in Table 1. The boride film was evaluated by X-ray diffraction. Using an X-ray diffractometer manufactured by Rigaku Corporation, the tube voltage was 120 kV, the tube current was 40 μm, the X-ray source Cukα, the X-ray incident angle was 5 degrees, the X-ray incident slit was 0.4 mm, and 2θ was 20 to 90 degrees. The crystal structure was determined, and the diffraction intensity ratio, Ia value, Ib value, and Hw value with respect to the sum of the diffraction intensity of (001), (101), and (002) were measured. The results are shown in Table 2. The residual stress of the boride film was measured using the X-ray diffraction parallel tilt method. As a result of the measurement, the residual compressive stress was 0.1 GPa or more in any of the films of the present invention.

From Tables 1 and 2, the examples of the present invention having the strongest diffraction intensity on the (001) plane showed a hardness of 47 to 75 GPa and a high hardness. In general, titanium boride has a maximum strength at (101) and a hardness of about 30 to 40 GPa. FIG. 3 shows the result of X-ray diffraction of Example 1 of the present invention, which had the strongest diffraction intensity on the (001) plane. In Example 1 of the present invention, electrons emitted from the sputtering evaporation source and the gas were captured by the anode placed on the opposite side, and the plasma was more activated. As a result, it was strongly oriented in the (001) plane as compared with Comparative Example 2. A boride film with high crystallinity was formed. The hardness of the boride film reached 72 GPa, and a high hardness titanium boride film was obtained. Regarding having the strongest diffraction intensity in the (001) plane, I (001) / {I (001) + I (101) + I (111)} was taken as an Ic value, and this Ic value was considered as an index. That is, when the Ic value exceeds 50%, it can be considered as a boride film having the strongest diffraction intensity on the (001) plane. FIG. 4 shows that when the Ic value exceeds 50%, the hardness is high. Furthermore, by satisfying the relationship of I (001)> I (111)> I (101), the film had more excellent film properties and was a preferred form.
From Table 1, Examples 1-4 of this invention showed a low value with a friction coefficient of 0.24-0.37. In Examples 1, 3, and 4 of the present invention, almost no deposits adhered to the surface of the film after the test could be visually confirmed, and damage due to abrasion could hardly be confirmed from the depth profile of the surface of the film after the test. However, in Example 2 of the present invention, the wear of the disk progressed rapidly after the frictional wear test. On the other hand, in Comparative Example 17 having the strongest diffraction intensity on the (101) plane, the conditions were such that there was no anode electrode, so electrons were trapped on the vacuum vessel wall. As a result, the flight distance of electrons was remarkably short, the plasma activity was low, and the film hardness was as low as 33 GPa. The friction coefficient was 0.62, and the wear of the boride film progressed quickly. Inventive Example 1 and Comparative Example 17 were different in crystal orientation and different in the boride film growth itself. In Comparative Example 21, the boride film was peeled off in a layer form at the stage of removal from the vacuum container after film formation, and the adhesion strength was extremely low. FIG. 5 shows the relationship between the Ia value and the film hardness. When the Ia value was 7 ≦ Ia ≦ 25, a boride film having a high hardness was obtained, which was a preferred form. FIG. 6 shows the relationship between the Ib value and the film hardness. In the range of 0.1 ≦ Ib ≦ 1, a boride film having a high hardness was obtained, which was a preferable embodiment. FIG. 7 shows the relationship between the Hw value and the film hardness. In the range of 0.6 ≦ Hw ≦ 1.1, a boride film having high hardness was obtained, which was a preferred form. Moreover, it had high adhesion and a low coefficient of friction. Using the same film formation parameters as Example 1 of the present invention, the target material was changed to chrome boride, aluminum boride, zirconium boride, niobium boride, and tungsten boride, and Inventive Examples 12 to 16 were prepared. Evaluation was carried out. The evaluation results are shown in Tables 1 and 2. Under the same film forming conditions, titanium boride had the highest hardness, followed by chromium boride, zirconium boride, and aluminum boride in this order. The coefficient of friction was relatively low for chromium boride, aluminum boride and niobium boride. Even when compared with Comparative Example 17, they exhibited high hardness and a low friction coefficient, and exhibited excellent mechanical properties similar to titanium boride.
When the bias voltage, which is one of the deposition parameters, is −80 to −140 V, the strongest diffraction intensity is in the (001) plane, and the present invention example of −100 to −140 V is preferable because the hardness is increased. It was a form. On the other hand, at -20 to -60V, the strongest diffraction intensity was in the (101) plane. The film formation temperature was considered using the heater power value during film formation as an index. Since the temperature of the substrate is in the range of 500 to 600 ° C. with the heater power of 10 kW, the heater power value was changed with the anode placed on the opposite side of the vapor deposition source. The impact was small and the face index did not change. However, the higher the film forming temperature, that is, the higher the heater power, the higher the boride film tends to become harder. In particular, Invention Example 6 having a heater power of 5 kW and Invention Example 1 having a power of 10 kW were more preferable because of higher hardness than Invention Example 5 in which no heater heating was supplied. Under the condition of Ar flow rate of 100 to 600 sccm, a high hardness film was obtained. The higher the Ar flow rate, the higher the hardness and the lower the friction coefficient. Invention Examples 1 and 9 to 11 having an Ar flow rate of 300 to 600 sccm had high hardness and were preferable coating conditions. When the Ar flow rate was 500 sccm, the pressure in the vacuum vessel was about 0.5 Pa. On the other hand, Comparative Example 22 was the case where the Ar flow rate was as low as 50 sccm, but the crystallinity was poor from the X-ray diffraction results, and a number of diffraction peaks were observed, and the crystal structure could not be identified.

(Example 2)
In order to evaluate the wear resistance and durability, the tool life was evaluated by a square end mill under the following test conditions.
(Test conditions)
Tool: 4-flute solid square end mill, diameter 10mm
Cutting method: Side cutting Work material: ADC12, T6 treatment Cutting: Axial direction, 10 mm, radial direction, 2 mm
Spindle speed: 10kmin-1
Table feed: 4m / min
Cutting oil: None, Air blow The tool life evaluation results are as follows: Cutting length with flank wear width reaching 0.1 mm or extremely unstable machining conditions such as sparking, abnormal noise, flaking of work surface, burr, burn The cutting length that reached the above condition was defined as the tool life. Values less than 10 m were marked off. The evaluation results are also shown in Table 2.
From Table 2, Invention Examples 1 to 16 having the strongest diffraction intensity on the (001) plane have a durability that is approximately 1.6 times longer than Comparative Examples 17 to 20 showing the strongest diffraction intensity on the (101) plane. Has excellent tool life. In particular, Invention Example 1 showed a tool life approximately three times that of Comparative Example 17. By controlling the orientation of the crystal structure, the tool life was significantly improved. When the film hardness of the example of the present invention is 47 to 75 GPa, a particularly excellent tool life can be obtained, so that it was confirmed that the film hardness is particularly effective for improving the wear resistance. Since the present invention has higher thermal conductivity in a high temperature range of about 800 to 1000 ° C. corresponding to the cutting temperature than the conventional nitride film or carbide film, heat generated during cutting is released in the in-plane direction. Therefore, it was effective in avoiding welding and blade edge deformation. Excellent compatibility with iron-based work materials, adhesion resistance, and sliding properties.

FIG. 1 shows a front view of a film forming apparatus used in the present invention. FIG. 2 shows a top view of the film forming apparatus used in the present invention. FIG. 3 shows an X-ray diffraction result of Example 1 of the present invention. FIG. 4 shows the relationship between Ic value and film hardness. FIG. 5 shows the relationship between the Ia value and the film hardness. FIG. 6 shows the relationship between the Ib value and the film hardness. FIG. 7 shows the relationship between the Hw value and the film hardness.

Explanation of symbols

1: Vacuum container 2: Base material 3: Sputtering evaporation source 4: Sputtering evaporation source 5: Sputtering evaporation source 6: Power supply 7: Anode 8: Bias power supply 9: Exhaust line 10: Gas supply port

Claims (5)

In a coated tool in which a boride film made of one or more metal elements selected from Al, Si, Cr, W, Ti, Nb, and Zr is coated on a substrate surface, the boride film has a hexagonal crystal structure. A coated tool characterized by having the strongest diffraction intensity in the (001) plane in X-ray diffraction and having a residual compressive stress of 0.1 GPa or more. The coated tool according to claim 1, wherein the diffraction intensity of the (001) plane in the X-ray diffraction of the boride film is I (001), the diffraction intensity of (111) is I (111), and I (001) / I A coated tool, wherein 7 ≦ Ia ≦ 25, where (111) is an Ia value. 3. The coated tool according to claim 1, wherein when the diffraction intensity of (101) in the X-ray diffraction of the boride film is I (101) and I (101) / I (111) is Ib value, 1. A coated tool characterized in that 1 ≦ Ib ≦ 1. 4. The coated tool according to claim 1, wherein the half-value width Hw value of the (001) plane in the X-ray diffraction of the boride film is 0.6 ≦ Hw ≦ 1.1. Coated tool characterized by The coated tool according to any one of claims 1 to 4, wherein the boride coating satisfies I (001)> I (111)> I (101).

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