JP2009220260A - Coated cutting tool and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated cutting tool having a WC-based cemented carbide alloy as the base material which improves adhesion strength between a coating and a base material, drastically reduces film detachment under a practical use environment, and is superior in wear resistance, and a method for manufacturing the coated cutting tool. <P>SOLUTION: In the coated cutting tool coated with a hard coating on a tool made of the WC-based cemented carbide alloy as the base material, a crystalline structure of the base material surface is a W-modified phase having a bcc structure, and a carbide phase is disposed right on the W-modified phase and the hard coating is disposed right on the carbide phase. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coated tool that requires wear resistance, such as a cutting tool and a mold, and a method for manufacturing the coated tool.

  Patent Documents 1 to 3 disclose a technique for improving the adhesion between a hard film and a substrate, and particularly Patent Document 4 discloses a technique for surface treatment of a substrate by metal ion bombardment as a coating pretreatment. Is disclosed.

JP-A-4-128362 JP 7-310173 A JP 2000-129423 A JP 2002-103122 A

  The present invention relates to a coated tool using a WC-based cemented carbide base material, which improves the adhesion strength between the film and the base material, significantly reduces film peeling in a practical environment, and has excellent wear resistance. A manufacturing method is provided.

The first invention in the present invention is a coated tool in which a hard film is coated on a tool based on a WC-based cemented carbide base material, and the crystal structure of the surface of the base material is a W-modified phase having a bcc structure, A coated tool comprising a carbide phase immediately above the W-modified phase and a hard film directly above the carbide phase.
According to a second aspect of the present invention, there is provided a manufacturing method of a coated tool in which a hard film is coated on a tool based on a WC-based cemented carbide, the manufacturing method including a film forming apparatus provided with an arc discharge evaporation source. And a first step of performing ion bombardment treatment and a second step of forming a film. The first step includes negative bias voltages P1, 600 ≦ P1 ≦ 1000 ( V) is applied and the cathode material is evaporated from the arc discharge evaporation source using a mixed gas containing hydrogen gas at a pressure of 0.01 to 2 Pa, and the substrate is irradiated with metal ions evaporated from the cathode material. A W-modified phase in which the surface temperature of the substrate is in the range of 800 to 860 ° C. and the crystal structure of the substrate surface is a bcc structure, and the W-modified phase is formed in the second step. Coated tool characterized by depositing the hard film directly on It is a manufacturing method. By adopting the above configuration, in a coated tool based on a WC-based cemented carbide, the adhesion strength between the coating and the substrate is improved, and the peeling of the coating is greatly reduced in a practical environment, resulting in wear resistance. An excellent coated tool and a method for producing the coated tool can be provided.

In the first invention of the present invention, the W-modified phase of the coated tool is 10 ≦ T1 ≦ 300 nm, the X-ray diffraction has a maximum diffraction intensity at (110) of the bcc structure, I (200) / I (110)> 0.1 or I (210) / I (110)> 0.2, the lattice constant is 0.315 to 0.316 nm, E ≦ 40 nm, 1 ≦ H / E ≦ 7 is preferable from the viewpoint of improving the adhesion strength between the tool base and the coating. Moreover, it is more preferable from the viewpoint of improving the adhesion strength between the tool substrate and the coating that it has a carbide phase immediately above the W-modified phase, is TiC, and is 20 ≦ T2 ≦ 300 nm. Further, the hard film directly above the carbide phase is a nitride layer, the crystal structure is an fcc structure, at least one of the nitride layers is essentially composed of Al, and the remaining Ti, Cr, W, Nb, Y, From the viewpoint of improving the adhesion strength between the tool base and the coating, it is one or more nitrides selected from Ce, Si, B, and that the interface between the carbide phase and the nitride layer is in an epitaxial relationship. More preferred.
In the second invention of the present invention, the hydrogen gas volume ratio of the mixed gas used in the first step is preferably 1 to 20%, and the hard coating is preferably a compound containing Al and Cr as metal components. .

  The present invention is a coated tool using a WC-based cemented carbide as a base material, which improves the adhesion strength between the film and the base material, significantly reduces film peeling in a practical environment, and is excellent in wear resistance, And a method of manufacturing a coated tool. As a result, tool durability and tool life were improved, and cutting efficiency was improved.

  1st invention in this invention improved the adhesive strength of a hard film | membrane and a tool base material in order to improve the durability of a coated tool. Hard coating often leads to abnormal wear due to peeling before exhibiting excellent mechanical properties, leading to tool life, especially on the tool flank side during high-speed cutting or cutting of hard materials. Abnormal wear occurs starting from the peeling of the coating between the rake face and the coating between the substrate and the substrate during wet cutting. This film peeling dominates the tool life. Therefore, this invention improved the adhesive strength of a membrane | film | coat and a base material, and improved the lifetime of the coating tool. In order to improve the adhesion strength, it is necessary that the crystal structure on the surface of the tool base is a W-modified phase having a bcc structure. Here, the W-modified phase is referred to as a W-modified phase in which the WC of the cemented carbide is converted into W through decomposition of W and C by irradiation treatment of Ti ions. The reason for having excellent adhesion strength due to the presence of the W-modified phase is considered as follows. Usually, the surface of a cemented carbide tool substrate has a plurality of compounds or single metals, and the film starts growing immediately above any of these. At this time, the film grown on the compound and the film grown on the single metal have different growth orientations, lattice misfits, and crystal grain sizes, so that the grown film becomes a polycrystal of relatively fine crystals from the initial growth stage. Extremely high residual stress is stored at the base and coating interface of hard alloy tools, leading to a decrease in adhesion strength. In view of this, the present invention provides a coating film in which a part of WC previously contained in a cemented carbide tool base material is deposited on the surface of the base material as a W-modified phase, the crystal structure is bcc structure, The residual stress near the interface between the substrate and the substrate was greatly reduced. As a result, high adhesion strength between the substrate and the film was realized. This point is essentially a difference between the conventional technique which attempts to improve the adhesion strength by covering the intermediate layer and the present invention. In the present invention, since the WC component preliminarily contained in the tool base material is precipitated as a W-modified phase, the thickness of the tool base material having a three-dimensional shape can be controlled uniformly and easily. On the other hand, with the conventional intermediate layer coating, there is a limit to three-dimensional uniform coating. In the present invention, there is no direct interface between Co and the hard coating, and excellent interfacial adhesion strength is exhibited. In contrast, a hard coating that grows on Co, which is a base material component of a cemented carbide, grows as a fine polycrystal, so the residual compressive stress increases near the interface between the substrate and the coating, and the growth continues. Property was hindered, and the adhesion strength between the substrate and the film was reduced.

  The T1 value of the present invention is preferably controlled so as to satisfy 10 ≦ T1 ≦ 300 nm, whereby excellent adhesion strength between the tool substrate and the film can be obtained. When the thickness is less than 10 nm, the effect of the W-modified phase is poor. When the thickness exceeds 300 nm, the adhesion strength tends to decrease. As a result, the effect of the W-modified phase cannot be obtained, and conversely, the peel resistance may decrease. The W-modified phase of the present invention is preferably present in a layer form on the tool substrate, but may be preferentially present in an island shape on the compound of the tool substrate. The adhesion strength can be improved. Further, when the WC particles of the cemented carbide exceed 1 μm and the T1 value is 50 nm or less, the W-modified phase is easily formed in an island shape.

The W-modified phase of the present invention preferably has the maximum diffraction intensity on the (110) plane of the bcc structure. This is because the residual stress of the film is lowered, the adhesion strength is high, and the peel resistance can be improved. In particular, by satisfying the relationship of I (200) / I (110)> 0.1 or I (210) / I (110)> 0.2, the residual stress of the film is reduced and the adhesion strength is reduced. It becomes high and can improve peeling resistance. When the I (200) / I (110) value is 0.1 or less, or when the I (210) / I (110) value is 0.2 or less, the residual stress increases and the peel resistance decreases. Therefore, the durability of the tool is reduced. From the durability of the tool, the preferable upper limit value of I (200) / I (110) value is 0.19, and the preferable upper limit value of I (210) / I (110) value is 0.27.
The W-modified phase of the present invention is W, and the lattice constant of 0.315 to 0.316 nm is particularly effective for improving the durability of the tool. The lattice constant of W by the JCPDS card is about 0.3164 to 0.3165 nm. A smaller lattice constant indicates less strain in the lattice and lower residual stress, which is a more preferred configuration of the present invention.
By controlling the E value of the present invention to E ≦ 40 nm, the adhesion strength between the substrate and the coating is improved, and the durability of the tool is further improved. The smaller the E value and the finer the W modified phase, the better the adhesion strength. When the thickness exceeds 40 nm, the mechanical strength of the W-modified phase decreases, and abnormal wear tends to occur due to slippage starting from the W-modified phase in the wear environment. By setting the H / E value to 1 ≦ H / E ≦ 7, the residual stress is low, the slip in the W-modified phase is suppressed in the wear environment, the adhesion strength between the base material and the film is improved, and the tool Improves durability.
The coated tool of the present invention has a carbide phase immediately above the W-modified phase, and further has a hard film directly above the carbide phase. By constituting in the order of the tool base material, the W-modified phase, the carbide phase, and the hard coating, each joining interface has excellent adhesion strength, and the tool durability is improved. Specifically, the carbide phase is preferably TiC, and the T2 value is preferably 20 ≦ T2 ≦ 300 nm. When the carbide phase is TiC, it is optimal from the viewpoint of adhesion strength with the substrate. Other carbides that can provide similar effects include zirconium carbide, niobium carbide, hafnium carbide, and tantalum carbide, which have lower free energy of formation than tungsten carbide. By setting the crystal structure to fcc, it is possible to improve excellent adhesion strength and tool durability. When the T2 value is less than 20 nm, the effect of improving the adhesion strength due to the carbide phase formation cannot be confirmed. On the other hand, when it exceeds 300 nm, heat resistance will fall and abrasion resistance will fall. The carbide phase is preferably layered immediately above the W-modified phase, but may be preferentially present in the form of islands on the base compound, both of which can improve the adhesion strength between the base and the coating. .
In addition, the hard coating immediately above the carbide phase is a nitride having a crystal structure of fcc structure, and this nitride has Al as an essential component and the remaining Ti, Cr, W, Nb, Y, Ce, Si, B It is preferable that it is 1 or more types of nitrides selected from these. Since the nitride crystal structure has an fcc structure, consistency with the carbide phase is good, adhesion strength is increased, and it is effective for improving durability. The hard film may be composed of nitride, carbide, boride, sulfide, oxide, or a solid solution thereof, but it is particularly preferable to coat a nitride layer having an fcc structure directly on the carbide phase. . The nitride composition is one or more nitrides selected from Ti, Cr, W, Nb, Y, Ce, Si, and B with an Al content of 50% to 80% and the remaining 20 to 50%. It is. Particularly preferred is a nitride of Al and Cr, or a nitride containing less than 10% of Ti, Si, W, Y, B, Ce, and Nb in the nitride of Al and Cr. Further, the nitride may contain O, C, S, etc., and its substitution amount is less than 30% of nitrogen.
By making the interface between the carbide phase and the hard film epitaxial, it is possible to coat each bonded interface with extremely excellent adhesion strength, so that the durability of the tool can be remarkably improved, which is preferable. . A particularly preferred embodiment of the present invention is to laminate on a cemented carbide tool substrate in the order of a W-modified phase having a bcc structure, a carbide phase having an fcc structure, a nitride layer, and a hard coating. Thereby, it can join, respectively, in the state in which each joining interface had remarkably high adhesion strength, and it can improve the durability of a tool markedly. That is, the W-modified phase and the carbide phase have excellent adhesion strength due to the bond strengthening by maintaining the continuity of the one-part lattice, and the carbide phase and the hard film have excellent bond strength due to the epitaxial strengthening relationship. Dramatically improves durability.

As a second invention in the present invention, a method will be described in which the surface of a cemented carbide tool substrate is made into a W-modified phase whose crystal structure is a bcc structure. First, in the first step, the tool base is placed in a decompression vessel to which a bias voltage can be applied, and is evacuated and heated. A negative bias voltage value P1 (V) is applied to the substrate surface, and the substrate surface is cleaned by ion irradiation of the cathode material from an evaporation source of the cathode material. Here, the cathode material is one or more metals selected from Ti, Zr, Hf, Nb, and Ta. For example, the substrate surface can be cleaned by irradiation with Ti ions from a Ti evaporation source. The surface temperature of the substrate is controlled to 800 to 860 ° C. by a heating device such as a heater, irradiation power of irradiation with metal ions, irradiation time, and the like. The P1 value in the present invention is 600 ≦ P1 ≦ 1000. The reason for this is that if it is lower than 600 V, the W-modified phase is not formed on the surface of the tool substrate, and the adhesion strength between the hard coating and the tool substrate cannot be increased. On the other hand, if the voltage exceeds 1000 V, the temperature will be too high, and the strength of the surface of the cemented carbide tool will rapidly decrease. As the metal ions of the cathode material, one or more metal ions selected from Ti, Zr, Hf, Nb, and Ta are used. This is because carbides of these metals have lower free energy of formation than W carbides, are convenient for decarburizing WC, and can stably form a W-modified phase. The reason why the surface temperature of the tool base is set to 800 to 860 ° C. is that when it is less than 800 ° C., the W-modified phase is not formed, and at a temperature higher than 860 ° C., the strength of the tool base rapidly decreases. This is because chipping and abnormal wear are likely to occur. A mixed gas containing H2 is used as the atmospheric gas. This has a high effect of suppressing the adsorption of other elements to the tool base and the coating interface. This is a so-called reduction action and an ion getter effect action by Ti ions and the like, and has an effect of suppressing the mixing of different elements in the vicinity of the interface. In addition to H2, it is also effective to use a mixed gas such as Ar, N2, and Kr. The pressure in the container is 0.01 to 2 Pa. This is because if the pressure is less than 0.01 Pa, there is no gas addition effect, and no W reforming phase is formed. On the other hand, if it exceeds 2 Pa, the metal used for the metal ion bombardment tends to adhere, and in this case as well, the W-modified phase is not formed, so that the adhesion strength cannot be improved. In the first step, simultaneously with the cleaning of the base material surface, the WC on the base material surface becomes a W modified phase by Ti ions and the like colliding with the surface, and the WC C is decomposed from W and combined with Ti etc. A Ti carbide phase is formed immediately above the modified phase. Further, in the vicinity of an evaporation source such as Ti, an ion getter effect also works to suppress mixing of different elements in the vicinity of the tool base and the coating interface. Ti that has taken in different elements does not have a potential, and therefore cannot reach the substrate to which a bias voltage is applied. The W-modified phase formed and precipitated in this way greatly contributes to the relaxation of the residual stress of the film to be coated thereafter and the improvement of the adhesion strength between the tool substrate and the film. For controlling the T1 value, controlling the surface index in the X-ray diffraction of the W-modified phase, controlling the lattice constant, and controlling the E value, for example, irradiation time of Ti ions, bias voltage, pressure in the vessel, gas type, Ti evaporation Adjust the power to the source. In particular, the influence of the Ti ion irradiation time is large for the control of the T1 value, and the influence of the P1 value and the pressure in the container is large for the control of the surface index. For example, when the P1 value during the formation of the W-modified phase is 800 V or more, the diffraction intensity of (110) tends to increase, and the I (200) / I (110) value, I (210) / I (110) Each value can be set to a value close to the lower limit value.
Next, in the second step, the negative bias voltage P2 value is applied to 20 ≦ P2 ≦ 300, the cathode material is evaporated from the arc discharge evaporation source in the plasma while supplying the reactive gas, A compound obtained by reacting the cathode material and the reactive gas is formed and coated as a hard film directly on the W-modified phase. By carrying out like this, the cemented carbide base material and the hard film can exert outstanding adhesion strength, and the durability of the tool can be remarkably improved.

  The coated tool of the present invention is particularly preferably a cutting tool used for cutting high hardness steel, stainless steel, heat resistant steel, cast steel, and carbon steel. Examples thereof include a ball end mill, a multi-blade end mill, an insert, a drill, a cutter, a broach, a reamer, a hob, and a router. Tools such as molds and punches also exhibit excellent wear resistance. The coated tool of the present invention can exhibit extremely excellent durability without being affected by the normal surface on the substrate side, such as a ground surface, a sintered surface, and a mirror surface state. Examples of the present invention will be described below.

Example 1
An arc ion plating (hereinafter referred to as AIP) type film forming apparatus was used for the production of Invention Example 1. In this apparatus, a permanent magnet is provided on the back of the target, and three arc evaporation sources having a perpendicular magnetic field are mounted on the target. The targets are denoted as C1, C2, and C3, respectively. Further, the magnetic flux densities of the permanent magnets arranged on the back of each target are the same for C2 and C3, and C3> C1. The inside of the vacuum vessel is evacuated by a vacuum pump, and gas is introduced from a supply port. The bias power source is connected to the substrate and independently applies a negative DC bias voltage to the substrate. The substrate rotation mechanism is a three-axis planetary mechanism, and the main shaft rotates at a speed of three rotations per minute. The cemented carbide substrate has a composition of wt%, Co: 8%, Cr: 0.5%, VC: 0.3%, the balance WC and inevitable impurities, WC average particle size 0.6 μm, hardness HRA93 9 inserts for a 2-flute ball end mill manufactured by Hitachi Tool Co., Ltd., R: 5 mm were used. As a base material for X-ray diffraction, a test piece of SNMN120408 shape with Co: 10%, Cr: 0.7%, WC average particle size 0.8 μm, and mirror finished was prepared. As a substrate for measuring residual stress, Co: 13.5%, Cr: 0.5%, TaC: 0.3%, WC average particle size 0.8 μm, test piece size 4 × 8 × 25 mm, thickness 0. A test piece of 7 to 0.9 mm was prepared. The substrate was fixed to a jig, and the inside of the vacuum vessel was first evacuated to 8 × 10 −3 Pa or less, and then heated to a substrate temperature of 600 ° C. with a heater. After the pressure reached 1 × 10 −3 Pa or less, the substrate was pretreated. The treatment conditions were such that a mixed gas having a mixing ratio of Ar and H2 of 90:10 was introduced at a flow rate of 20 sccm. The pressure at this time was about 8 × 10 −2 Pa. Next, a negative bias voltage of 600 V was applied, and a cathode current of 120 A was supplied to the C1 target. Cleaning of the substrate was started by Ti ions and gas ions released from C1. The bias voltage was gradually increased to 1000 V, and a cleaning process was performed for 10 minutes at 1000 V. The substrate temperature after the treatment was 820 ° C. Subsequent to the substrate cleaning process, a hard film forming step was performed. The power supply to C1 was interrupted, the supply gas was switched to N2, and the pressure was set to 5 Pa. A bias voltage of 100 V and a power of 150 A were supplied to C2, and a hard film having a C2 composition was coated with approximately 1.5 μm. Subsequently, the power supply to C2 was interrupted, and then 150 A of power was supplied to C3, and the hard coating of the outermost layer of C3 composition was coated by 1.5 μm. Thereafter, the substrate was cooled to approximately 200 ° C. or lower and taken out from the vacuum vessel. The obtained sample was defined as Example 1 of the present invention. Table 1 shows the cleaning conditions before coating, the targets used, and the film formation conditions.

(Example 2)
The substrate cleaning processes of Invention Examples 2 to 30 and Comparative Examples 31 to 37 were in accordance with the operation procedure of Invention Example 1. However, the mixed gas of the substrate cleaning process used in Invention Examples 16 to 19 and Comparative Example 37 had a mixing ratio of N2 and H2 of 90:10. The substrate temperature after cleaning was in the range of about 760 to 850 ° C., although it varied depending on the metal target species installed in C1. The film forming steps of Invention Examples 2 to 19 were also performed in accordance with the conditions of Invention Example 1. Unless otherwise noted, the treatment was performed under the same conditions as Example 1 of the present invention. The film forming process of Invention Example 20 was performed as follows in order to compare the durability of the tool exerted by the layer immediately above the carbide phase. Immediately after the cleaning process of the substrate, the gas in the vacuum vessel is replaced with a mixed gas of Ar: acetylene mixing ratio of 70:30, the pressure is set to 2 Pa, the negative bias voltage is set to 100 V, and C2 is set to AlCr A power of 150 A was supplied to the alloy target, and the carbide film was coated with approximately 1.5 μm. Next, the gas was replaced with N 2 gas, the pressure was set to 5 Pa, 150 A power was supplied to the TiSi alloy target placed on C 3, and a nitride film containing C 2 and C 3 metal components was coated by 0.5 μm. Next, power supply to C2 was interrupted, and a nitride film containing only the metal component of C3 was coated with about 1 μm, and then the substrate was cooled to about 200 ° C. or lower and taken out. The cleaning process before film formation was the same as that of Example 1 of the present invention. The film formation process of Invention Examples 21 to 28 having different nitride layer compositions was the same as that of Invention Example 1 except that the target composition placed on C2 was different. In Invention Example 29, no target was set on C3, and in Example 30 of the invention, a CrSiB target was set on C3 and coated in the same manner as Example 1.

  Using the coated tool base material, the cross section of the interface between the base material and the hard film was observed with an acceleration voltage of 200 kV using a field emission transmission electron microscope (hereinafter referred to as FE-TEM) manufactured by JEOL. In order to investigate each phase, the crystal structure of each layer, the crystal growth direction, and the presence or absence of an epitaxial state between the carbide phase and the hard film, a limited-field diffraction image or an electron beam diffraction image was taken. The approximate composition of the W modified phase and the carbide phase was determined by an energy dispersive X-ray analyzer attached to FE-TEM (hereinafter referred to as EDS). T1 value, T2 value, H value, and E value were measured from a cross-sectional FE-TEM image, but were also measurable from a fractured surface structure photograph by a field emission scanning electron microscope (hereinafter referred to as FE-SEM). . Using the coated base material for X-ray diffraction, analysis by X-ray diffraction was performed. The X-ray diffraction conditions were a tube voltage of 120 kV, a tube current of 40 μm, an X-ray source Cukα, an X-ray incident angle of 5 degrees, an X-ray incident slit of 0.4 mm, and 2θ under measurement conditions of 20 to 70 degrees. From the X-ray diffraction results, the crystal structure, maximum intensity plane index, orientation strength ratio, and lattice constant were determined. In order to determine a crystal structure having a T1 value of 100 nm or less, sufficient X-ray intensity may not be obtained. Therefore, priority was given to the result of electron beam diffraction by FE-TEM. In the inventive examples 1 to 30, the W-modified phase had a bcc structure and the carbide phase had an fcc structure. Table 2 shows the evaluation results of the W modified phase and the carbide phase.

  Next, using the coated tool base material, the composition of the hard coating was analyzed by wavelength dispersive electron beam probe microanalysis (hereinafter referred to as WDS-EPMA), an acceleration voltage of 10 kV, a sample current of 5 × 10-8 A, and an acquisition time of 10 Second, an analysis region diameter of 1 μm and an analysis depth of about 1 μm were measured at five points, and the average value was obtained. Numerical values are shown as 100 in terms of atomic ratio. Residual stress was determined from Formula 1 using the coated residual stress measurement substrate. Here, E is 517.54 GPa, v is 0.238, D is the thickness of the test piece, δ is the deflection amount of the test piece, d is the thickness of the entire film, and L is the length up to the maximum deflection amount. These measurement results are shown in Table 3.

In FIG. 1, the cross-sectional FE-TEM photograph which observed the interface structure in the cross section between the base material of this invention example 1 and a hard film is shown. A layered W-modified phase (2) and a layered carbide phase (3) having a particle diameter different from that of the tool substrate (1) were observed at the interface between the tool substrate (1) and the hard coating (4). FIG. 2 shows a cross-sectional TEM photograph in the vicinity of the interface between the tool base material (1) and the hard coating having a different field of view from FIG. Similar to FIGS. 2 to 1, the layered and particulate W-modified phase (2) is more clearly observed, and the W-modified phase (2) is clearly different in particle size from the tool substrate (1). FIG. 3 shows the dark field STEM image of FIG. An EDS analysis with a diameter of 1 nmφ of spot numbers 1 to 6 in FIG. 3 was performed. For EDS analysis, W-Lα, C-Kα, Co-Kα, Ti-Kα, and Cr-Kα were used, respectively. From the EDS analysis results, the W-modified phase (2) shown in FIGS. 1 and 2 was W, and the carbide phase (3) was TiC. FIG. 4 shows an electron diffraction photograph of the W-modified phase (2) shown in FIGS. 1 and 2 taken with a beam diameter of 20 nm. From the electron diffraction photograph and the EDS analysis result, the W-modified phase was W having a bcc structure. FIG. 5 shows a limited field diffraction photograph of the carbide phase (3) shown in FIGS. The carbide phase was TiC having the fcc structure in accordance with the previous EDS analysis result.
FIG. 6 shows a cross-sectional TEM photograph near the interface between the carbide phase and the nitride layer. In FIG. 6, the [110] incident limited field diffraction of the carbide phase of spot number 9 and the limited field region of 140 nm near the film of spot number 10 is shown in the upper left and lower left, respectively. The carbide phase and the nitride layer have an fcc structure, the nitride layer and the carbide phase have the same diffraction pattern, and the crystal growth directions are the same as the [−111] to [−113] directions or equivalent directions. From this, it was confirmed that the carbide phase and the nitride layer have an epitaxial relationship. From the EDS analysis results, a carbide phase in which W, Co, Ti, Cr, etc. were dissolved was formed near the interface between the W-modified phase and the tool substrate, and the bonding strength was increased. The W-modified phase is formed by the WC in the tool base material being bonded to Ti by the collision of Ti ions, and the WC C is combined with Ti to form a TiC phase. The W-modified phase and the carbide phase form a compound in addition to bonding with diffusion. In particular, the formation of a W-modified phase having a bcc crystal structure was effective in reducing the residual compressive stress of the entire film. The carbide phase and the nitride layer were epitaxially grown, and Example 1 of the present invention achieved extremely strong bonding. On the other hand, in Comparative Example 31, the composition mixed layer of W, Ti, C, Co, or the composition gradient region of the tool base component and the coating component was confirmed, and no W-modified phase or carbide phase was formed. . In Comparative Example 32, no interface structure between the tool base material and the film was confirmed. The WC of the tool base has an hcp crystal structure, and the crystal structure is different from the film having the fcc structure, and the film grown on Co in the tool base has a crystal structure different from the film having the fcc structure. Furthermore, since the polycrystalline coating particles tend to grow, the adhesion strength was poor.
FIG. 7 shows the X-ray diffraction results of Example 1 of the present invention and Comparative Examples 31 and 32. In Example 1 of the present invention, the diffraction intensity of the (110) plane of W having a bcc structure due to the W-modified phase was observed, but not in Comparative Examples 31 and 32. Further, for confirmation, a sample subjected only to the coating pretreatment was prepared, and the structural analysis in the vicinity of the surface was performed. As a result, in Example 1 of the present invention, the presence of a W-modified phase having a bcc structure and a TiC phase having an fcc structure was clearly observed, and the W-modified phase was most strongly oriented in the (110) plane, and (211 ) And (200) in the order of diffraction intensity, and the TiC phase showed the maximum diffraction intensity on the (200) plane, but Comparative Example 31 had no W-modified phase and no carbide phase.

(Example 3)
Using the obtained coated tool and base material, the durability of the tool was evaluated under the following conditions. The tool life is defined as the cutting length (m) when the flank wear width of the tool reaches 0.1 mm, the durability of the tool is evaluated, and a coated tool having a cutting length of 200 m or more can exert the effect of the present invention. Judged that. Cutting lengths less than 10 m are rounded off. The evaluation results are also shown in Table 3.
(Test conditions)
Tool: 2-flute ball end mill insert, radius 5 mm
Work material: SKD11, hardness HRC60
Cutting: axial direction, 0.2 mm, radial direction, 0.2 mm
Number of revolutions: 8000 / min Table feed rate: 2000 mm / min Feed rate per blade: 0.1 mm / blade Cutting oil: None, air blow

As a result of comparing the inventive examples 1 to 3 and the comparative examples 31 to 35 from Table 3, the inventive example improves the adhesion strength between the film and the substrate, reduces the film peeling, and improves the durability and wear resistance of the tool. It was effective for improvement. When the target material type of C1 was Ti of Invention Example 1, Zr of Invention Example 2, and Hf of Invention Example 3, formation of a W-modified phase and a carbide phase could be confirmed. On the other hand, in the Cr of Comparative Example 33, V of Comparative Example 34, and TiAl of Comparative Example 35, no W-modified phase was formed. When Cr, V, or TiAl is used, it is considered that the temperature rise of the base material is lower than that when Ti, Zr, or Hf is used, and the W-modified phase is not formed. When the cutting distance is compared, Examples 1-3 of the present invention are 200-300 m, whereas Comparative Examples 33-35 are less than 140 m, and the examples of the present invention are excellent in tool durability. In Examples 1 to 3 of the present invention, the residual compressive stress of the entire film was reduced to 2.1 to 2.5 GPa by the formation of the W-modified phase, and the adhesion strength was improved. However, Comparative Examples 33 to 35 were 3.5 to 3.9 GPa.
In order to consider the influence of the durability of the tool on the T1 value and the T2 value, Examples 1 and 4 to 10 of the present invention were compared. As the T1 value increased from 5 to 1000 nm, the I (200) / I (110) value, I (210) / I (110) value, lattice constant, E value, and T2 value tended to increase. Moreover, since the cutting distance showed a cutting distance of 300 m or more when the T1 value was in the range of 10 to 200 nm, it was a more optimal T1 value.
In order to consider the durability of the tool affected by the gas type and gas flow rate in the cleaning process before film formation, Invention Examples 1, 11 to 19, and Comparative Examples 36 to 37 were compared. When Invention Examples 11 and 12 were compared, by using H2 gas, peeling of the substrate and the film was suppressed, and the cutting strength was increased by increasing the adhesion strength. In Invention Example 11 using only Ar gas, from a result of high-frequency glow discharge emission analysis, a trace amount of oxygen element and iron element which is a part of the jig component were confirmed in the vicinity of the interface between the base material and the film. Therefore, Example 12 of the present invention using a mixed gas with H 2 gas can reduce the impurity concentration at the interface and is considered to be effective in improving the adhesion strength. As the mixed gas flow rate of Ar and H2, and the mixed gas flow rate of N2 and H2, the T1 value decreases, and at the same time, the X-ray intensity of the (200) and (210) planes of the W reforming phase increases, and the maximum intensity The surface index, I (200) / I (110) value, I (210) / I (110) value, and lattice constant increased, and the E value, H / E value, and T2 value tended to decrease. In Comparative Example 36 in which the mixed gas flow rate of Ar and H2 was 500 sccm, and in Comparative Example 37 in which the mixed gas flow rate of N2 and H2 was 1000 sccm, formation of a W reforming phase and a carbide phase was not confirmed. The comparative example 36 was confirmed to be a Ti metal layer having a bcc structure, and the comparative example 37 was confirmed to be a Ti nitride layer having an fcc structure. However, the durability of the tool could not be improved because the Ti metal layer and the Ti nitride layer had insufficient adhesion between the substrate and the film interface. From the durability evaluation results of Invention Examples 1 and 11 to 19, those having a cutting distance of 300 m or more are a preferable embodiment of the present invention with particularly less peeling from the tool base and the film interface, and the T1 value is 10 to 300 nm. , I (200) / I (110) value is 0.10 to 0.18, I (210) / I (110) value is 0.20 to 0.27, lattice constant is 0.3150 to 0.3160 nm, By setting the E value to 40 nm or less, the H / E value to 1 to 7, and the T2 value to 20 to 300 nm, it was shown that the film peeling at the initial stage of cutting was reduced and the adhesion strength was high.
In order to examine the durability of the tool exerted by the layer immediately above the carbide phase, Examples 1 and 20 of the present invention were compared. In Invention Example 20, since the layer immediately above the carbide phase became an amorphous phase, epitaxial growth with the carbide phase was not confirmed. For this reason, there were many peelings at the interface between the base material and the film as compared with the case of the nitride layer having the fcc structure, and the tool durability was lowered.
The durability of the tool due to the composition of the nitride layer was considered. Inventive Example 21, to which Si was added, showed a cutting distance of 1.2 times that of Inventive Example 1 which is a nitride of Al and Cr. Therefore, this is a preferred embodiment of the present invention. Inventive Example 22 to which W was added showed a cutting distance of 1.2 times, Inventive Example 23 to which Nb was added was 1.1 times, Inventive Example 24 to which Ti was added was equivalent, and Y was added. Invention Example 25 is 1.2 times, Invention Example 26 with Ce added is 1.2 times, Invention Example 27 with Si and Y added is 1.4 times, Invention Example 28 with Si and B added Showed 1.3 times the cutting distance. Invention Example 29 is a case where no TiSi-based hard coating is present, and is superior to the comparative example, but the tool durability was improved more with the hard coating. Inventive Example 30, in which the hard coating employs a CrSiB-based nitride, is inferior in tool durability to Inventive Example 1, but when carbon steel, alloy steel, etc. are processed under the same cutting conditions, 3 It was more than twice as durable.

Example 4
A method of producing Example 38 of the present invention will be described. The base material made of cemented carbide has a composition of wt%, Co: 8%, Cr: 0.5%, VC: 0.3%, balance WC and inevitable impurities, WC average particle size 0.6 μm, hardness Prepared HRA93.9, 2-flute ball end mill insert, R: 5 mm. A test piece having the same shape as that of Example 1 was prepared as an X-ray diffraction base material. The substrate cleaning conditions were the same as in Example 1 except that a mixed gas having a mixing ratio of Ar and H2 of 95: 5 was used. Subsequent to the substrate cleaning process, a hard film forming step was performed. The power supply to C1 was interrupted, the supply gas was switched to N2, and the pressure was set to 5 Pa. A bias voltage of 150 V and a power of 150 A were supplied to C2, and a hard film having a C2 composition was coated by about 3 μm. Thereafter, the substrate was cooled to approximately 200 ° C. or lower and taken out from the vacuum vessel. The obtained sample was determined as Example 38 of the present invention. Other inventive examples 39 to 62 were also prepared according to the above method unless otherwise noted.
Inventive Examples 39 to 43 and Comparative Examples 63 to 65 are for comparing the influence of tool durability exerted by the mixed gas flow rate of 95: 5 on the mixing ratio of Ar and H2 in the cleaning process before film formation. The flow rate was set in the range of 0 to 1000 sccm. Except for the mixed gas flow rate of Ar and H2, the manufacturing method before and after film formation was the same as that of Example 38 of the present invention. Similarly, Examples 44 to 47 of the present invention and Comparative Example 66 were prepared by changing the mixing ratio in order to compare the influence of the mixing ratio of Ar and H2, and Examples 48 to 52 of the present invention and Comparative Example 67 were compared with Ar. In order to compare the influence of the mixed gas flow rate with a mixing ratio of N2 of 95: 5, the flow rate was changed in the range of 10 to 1000 sccm. Inventive Examples 53 and 54 and Comparative Examples 68 to 70 were prepared by changing in the range of 500 to 1200 V in order to compare the influence of the bias voltage. In particular, Invention Example 53 was subjected to a cleaning process of 600 V for 30 minutes, and Invention Example 54 was subjected to a cleaning process of 800 V for 15 minutes. Invention Examples 55-58 and Comparative Examples 71-74 were prepared in order to compare the influence of the C1 target component in the metal bombardment before film formation. Invention Examples 60 to 62 and Comparative Examples 75 and 76 were prepared in the range of 10 to 400 V in order to compare the influence of the film forming bias voltage. In particular, Example 59 of the present invention used TiAl as a film formation target. Table 4 shows the cleaning conditions before coating, the target used and the film formation conditions, and Table 5 shows the evaluation results of the W-modified phase, carbide phase and tool life.

The durability of the tool was evaluated under the same conditions as in Example 3 using the obtained coated tool and substrate. First, the influence of the C1 target component was compared in the substrate cleaning before film formation. The durability of the tools of Invention Examples 38, 55-58 and Comparative Examples 71-74 using C1, Ti, Zr, Hf, Nb, Ta, Cr, Al, V, and TiAl were compared. When C1 was Ti, Zr, Hf, Nb, and Ta, the tool base material temperature reached 800 ° C. or higher, a W-modified phase was formed, and the durability of the tool was improved. On the other hand, when C1 was Cr, Al, V, or TiAl, the substrate temperature did not reach 800 ° C., the formation of a W-modified phase was not observed, and the durability of the tool could not be improved.
Next, in order to consider the durability of the tool affected by the gas flow rate, the mixing ratio, and the gas type in the cleaning process before film formation, the durability of the tool of the present invention example and the comparative example was compared. First, the inventive examples 38 to 43 having a mixed gas flow rate of Ar and H 2 of 10 to 400 sccm showed 2.3 times or more durability as compared with the comparative example. This is a result of the W-modified phase being formed and the adhesion strength between the tool substrate and the hard coating being improved. In the W reforming phase, the T1 value tended to decrease as the mixed gas flow rate of Ar and H2 increased. In Comparative Examples 63 and 64 having a mixed gas flow rate of 0.5 sccm, the durability of the tool was not improved. This is because the temperature of the tool base was 780 ° C. and less than 800 ° C., and the W-modified phase was not formed. Similarly, in Comparative Example 65 where the mixed gas flow rate was 1000 sccm, many peelings of the hard film were observed, and the durability of the tool was not improved. This is because the temperature of the tool base has increased to 870 ° C. Further, the durability of the tools was compared by changing the mixing ratio of the mixed gas of Ar and H2. Even if the mixed gas flow rate was 20 sccm, in Comparative Example 66 not containing H2, the W-modified phase was not formed, and the durability of the tool was not improved. This was thought to be because the formation of a W-modified phase at the interface was hindered because many impurity elements such as oxygen and iron were observed at the interface between the tool base and the hard coating. It has been found that H2 addition is effective for the formation of the W modified phase. Further, the T1 value tends to increase as the H2 content increases, and it is considered that the addition of H2 promotes the formation of the W reforming phase. However, in consideration of safety, the volume ratio is preferably 20% or less. However, when a special exhaust facility is provided, a high H2 content can form the W reforming phase in a shorter time. Furthermore, in order to compare the influence of the mixed gas flow rate of N2 and H2, the durability of the tools of Examples 48 to 52 and Comparative Example 67 of the present invention was compared. Even in the case of a mixed gas of N2 and H2, a W-modified phase was formed in the same manner as in the case of a mixed gas of Ar and H2, and the durability of the tool was improved.
In order to compare the influence of the P1 value (V) in the cleaning step before film formation, the durability of the tools of Invention Examples 53 and 54 and Comparative Examples 68 to 70 were compared. In Comparative Example 68 where the P1 value is less than 600 V, the tool base temperature does not reach 800 ° C. even when the processing time is extended, and the W modified phase is not formed, so the durability of the tool cannot be improved. It was. On the other hand, when the P1 value is 1100 V or more, the tool base material temperature is 870 ° C. or more, and the T1 value is 400 nm or more, and the hard film peels off from the W-modified phase during cutting, and the durability of the tool cannot be improved. It was.
In order to compare the influence of the P2 value (V) during film formation, the durability of the tools of Invention Examples 60 to 62 and Comparative Examples 75 and 76 were compared. When the P2 value was in the range of 20 to 300 V, the durability of the tool was improved. On the other hand, in Comparative Example 75 having a P2 value of 10 V, the progress of tool wear and peeling progressed simultaneously, and in Comparative Example 76 having a P2 value of 400 V, particularly peeling was observed, and the durability of the tool was not improved. Invention Example 59 was prepared using TiAl as the target C2 during film formation, and tool durability was compared. The nitride of Al and Cr was superior in heat resistance and wear resistance to the nitride of Ti and Al, and the adhesion strength with the tool substrate was also excellent.

FIG. 1 shows a cross-sectional TEM photograph of the film interface of Example 1 of the present invention. FIG. 2 shows a cross-sectional TEM photograph of the film interface of Example 1 of the present invention. FIG. 3 shows a dark field STEM photograph of FIG. FIG. 4 shows electron beam diffraction of the carbide phase shown in FIG. FIG. 5 shows limited field diffraction of the carbide phase shown in FIG. FIG. 6 shows a cross-sectional TEM photograph near the interface between the carbide phase and the nitride layer. FIG. 7 shows X-ray diffraction of Example 1 of the present invention and Comparative Examples 31 and 32.

Explanation of symbols

1: Tool base material 2: W modified phase 3: Carbide phase 4: Hard coating

Claims (16)

In a coated tool in which a hard film is coated on a tool based on a WC-based cemented carbide, the crystal structure of the surface of the substrate has a W-modified phase having a bcc structure, and is directly above the W-modified phase. A coated tool comprising a carbide phase and a hard coating directly on the carbide phase. The coated tool according to claim 1, wherein the average thickness of the W-modified phase is T1 (nm), and 10 ≦ T1 ≦ 300. The coated tool according to claim 1, wherein the W-modified phase has a maximum diffraction intensity on a (110) plane in X-ray diffraction. The coated tool according to any one of claims 1 to 3, wherein the diffraction intensity of the (110) plane, the (200) plane, and the (210) plane in the X-ray diffraction of the W-modified phase is I (110), I (200 ), I (210), I (200) / I (110) ≧ 0.1 or I (210) / I (110) ≧ 0.2. The coated tool according to any one of claims 1 to 4, wherein the lattice constant (nm) of the W-modified phase is 0.315 to 0.316. The coated tool according to any one of claims 1 to 5, wherein when the particle length in the direction perpendicular to the particle growth direction of the W-modified phase is E (nm), E≤40. Coated tool. The coated tool according to any one of claims 1 to 6, wherein when the particle length in the particle growth direction of the W-modified phase is H (nm), 1≤H / E≤7. Coated tool. The coated tool according to any one of claims 1 to 7, wherein the carbide phase is TiC. The coated tool according to any one of claims 1 to 8, wherein when the thickness of the carbide phase is T2 (nm), 20≤T2≤300. The coated tool according to any one of claims 1 to 9, wherein the hard coating is a nitride and the crystal structure is an fcc structure. The coated tool according to any one of claims 1 to 10, wherein at least one layer of the hard coating comprises at least one element selected from Ti, Cr, W, Nb, Y, Ce, Si, and B and Al. A coated tool characterized by being a nitride containing The coated tool according to any one of claims 1 to 11, wherein an interface between the carbide phase and the hard film is in an epitaxial state. In a method of manufacturing a coated tool in which a hard film is coated on a tool based on a WC-based cemented carbide, the manufacturing method performs ion bombardment using a film forming apparatus provided with an arc discharge evaporation source. It consists of a first step and a second step of forming a film. In the first step, a negative bias voltage P1, 600 ≦ P1 ≦ 1000 (V) is applied to the substrate, and a pressure of 0. Using a mixed gas containing hydrogen gas at 01 to 2 Pa, the cathode material is evaporated from the arc discharge evaporation source, and the substrate is irradiated with metal ions evaporated from the cathode material, and the surface of the substrate In the temperature range of 800 to 860 ° C., a W-modified phase whose crystal structure on the surface of the substrate has a bcc structure is formed, and in the second step, the hard film is formed immediately above the W-modified phase. The manufacturing method of the covering tool characterized by doing. The method for manufacturing a coated tool according to claim 13, wherein the hydrogen gas volume ratio of the mixed gas used in the first step is 1 to 20%. 15. The method for producing a coated tool according to claim 13 or 14, wherein the cathode material in the first step is one or more metals selected from Ti, Zr, Hf, Nb, and Ta, and uses the W-modified phase. An average thickness T1 (nm) of 10 ≦ T1 ≦ 300 is provided. 16. The method for manufacturing a coated tool according to claim 13, wherein the hard coating in the second step is a compound containing Al and Cr as metal components, and a negative bias voltage P2 value is applied to the substrate. Is formed as 20 ≦ P2 ≦ 300.