JP7125013B2 - A surface-coated cutting tool with a hard coating layer that exhibits excellent chipping resistance - Google Patents

Description

The present invention is a surface-coated cutting tool that exhibits excellent cutting performance over a long period of use by providing a hard coating layer with excellent chipping resistance even in high-speed interrupted cutting of alloy steel, high-carbon steel, etc. (hereinafter sometimes referred to as a coated tool).

Conventionally, there is a coated tool in which a Ti—Al-based composite carbonitride layer is formed by vapor deposition as a hard coating layer on the surface of a tool substrate such as a tungsten carbide (hereinafter referred to as WC)-based cemented carbide. These are known to exhibit excellent wear resistance.
However, although the conventional coated tool coated with the Ti—Al-based composite carbonitride layer has relatively excellent wear resistance, it is prone to abnormal wear such as chipping when used under high-speed intermittent cutting conditions. Therefore, various proposals have been made for improving the hard coating layer.

For example, Patent Document 1 has a plurality of layers deposited by CVD and includes Ti _1-x Al _x N layers and/or Ti _1-x Al _x C layers and/or Ti _1-x Al _x CN layers. Coated tools coated with a hard material are described, characterized in that an Al ₂ O ₃ layer is arranged as an outer layer on the layer (where x is between 0.65 and 0.95). there is

Further, for example, Patent Document 2 discloses a coated tool including a tool substrate and one or more hard coating layers formed on the surface thereof, wherein at least one layer of the hard coating contains hard particles. layer, the hard particles include a multilayer structure in which the first unit layer and the second unit layer are alternately laminated, and the first unit layer is composed of elements of groups 4 to 6 of the periodic table and Al The second unit layer includes a first compound consisting of one or more elements selected from the group and one or more elements selected from the group consisting of B, C, N, and O, and the second unit layer includes 4 to 4 of the periodic table. A coated tool containing a second compound consisting of at least one element selected from the group consisting of Group 6 elements and Al and at least one element selected from the group consisting of B, C, N and O is described. ing.

Furthermore, for example, in Patent Document 3, (a) the hard coating layer is (Ti _1-X Al _X ) (C YN _{1-Y )} having an average layer thickness of 1 to 20 μm formed by chemical vapor deposition. When expressed, the average content ratio X _avg of Al in the total amount of Ti and Al and the average content ratio Y _avg of C in the total amount of C and N are 0.60 ≤ X _avg ≤ 0.95, (b) the composite nitride layer or composite carbonitride layer containing crystal grains having a NaCl-type face-centered cubic structure, wherein 0 ≤ Y _avg ≤ 0.005; There is a periodic composition change of Ti and Al in the crystal grain along the normal direction of the tool substrate surface of the material layer, and the crystal grain in which the periodic composition change exists is the tool substrate surface The long-period layer is composed of a long-period layer having a composition change period of 50 to 200 nm along the normal direction, and the long-period layer is composed of two short-period layers A and B having different average Al contents. The period in the A layer and the B layer is 3 to 20 nm, and the differences Δx ₁ and Δx ₂ of the average maximum value and the average minimum value of the Al content x in the A layer and the B layer are 0.5 nm. 02 < Δx ₁ < 0.1, 0.02 < Δx ₂ < 0.1, and further, the average of the maximum values and the minimum values of the Al content x in the long period layer composed of the A layer and the B layer A coated tool is described, characterized in that the mean difference Δx ₃ satisfies 0.05<Δx ₃ <0.25 and Δx ₃ >(Δx ₁ +Δx ₂ ).

Japanese translation of PCT publication No. 2011-516722 JP 2014-129562 A JP 2016-137549 A

In recent years, there is a strong demand for labor saving and energy saving in cutting. Abnormal damage resistance such as peeling resistance is required, and excellent wear resistance over long-term use is also required.

Therefore, the present invention has been made in view of such circumstances, and even when subjected to high-speed interrupted cutting of alloy steel, high-carbon steel, etc., it has excellent chipping resistance and resistance over a long period of use. An object of the present invention is to provide a coated tool exhibiting wearability.

The present inventor has investigated the chipping resistance and wear resistance of a coated tool containing a composite nitride layer or composite carbonitride layer of Ti and Al (hereinafter collectively referred to as "TiAlCN layer"). In order to find out, we conducted a thorough study.

As a result, when there are two types of specific repeated changes in the composition of Ti and Al in the crystal grains having the NaCl-type face-centered cubic structure in the TiAlCN layer, a larger strain is generated than when there is only one type. New knowledge was obtained that this large strain contributes to the improvement of hardness and toughness, and improves the chipping resistance and fracture resistance of the hard coating layer.

The present invention was made based on the above findings,
"(1) A surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool substrate,
(a) the hard coating layer includes a composite nitride layer or composite carbonitride layer of Ti and Al having an average layer thickness of 1.0 to 20.0 μm,
(b) The composite nitride layer or composite carbonitride layer of Ti and Al has a composition of
When represented by the composition formula: (Ti _1-x Al _x ) (C _y N _1-y ),
The average x _avg of the content ratio x of Al in the total amount of Al and Ti of Al satisfies 0.60 ≤ x _avg ≤ 0.90, and the content of C in the total amount of C and N of C The average y _avg of the ratio y is 0.000 ≤ y _avg ≤ 0.005 (where x, y, x _avg , y _avg are atomic ratios),
(c) In the crystal grains having a NaCl-type face-centered cubic structure in the longitudinal section of the composite nitride layer or composite carbonitride layer of Ti and Al, the content ratio of Al to the total amount of Al and Ti in the Al x has a long-period variation with an average period d _Lavg of 50-200 nm and a short-period variation with an average period d _Savg of 1-20 nm (d _Lavg , d _Savg is the direction of the minimum period of variation of x value measured at
(d) n sections (section 1, . , n), the average value Δx _Lavg of the average difference Δx _Li between the maximum and minimum values of adjacent x in the long-period change in each interval is 0.12 to 0.15,
The average value Δx _Savg of the average difference Δx _Si between the maximum value and the minimum value of adjacent x in the short period change in each section is 0.03 to 0.07,
(e) The average difference Δx _Li between the maximum value and the minimum value of adjacent x in the long-period change in each section is, as it moves away from the tool base,
When n is 3 or more, (Average value of Δx _Li from interval 1 to interval [n/3]) <(Average value of Δx _Li from interval [n/3]+1 to interval [2n/3]) satisfying <(average value of Δx _Li from interval [2n/3]+1 to interval n),
When n is 2, Δx _L1 <Δx _L2
is increased to satisfy
(f) The composite nitride layer or composite carbonitride layer of Ti and Al is occupied by crystal grains of a composite nitride or composite carbonitride of Ti and Al having a NaCl-type face-centered cubic structure in a longitudinal section. The ratio is 80 area% or more, and the ratio of the crystal grains having the long period change and the short period change is 50 area% or more.
A surface-coated cutting tool characterized by:
(2) crystal grains having the NaCl-type face-centered cubic structure having the long-period change and the short-period change are 70 area % or more in the longitudinal section;
The surface-coated cutting tool according to (1), characterized in that: "

The surface-coated tool of the present invention has improved hardness and toughness of the hard coating layer and has excellent chipping resistance and peeling resistance.

It is a schematic diagram explaining the periodic change of the Al content rate x. It is a schematic diagram which shows the observation direction of the long-period change and short-period change of Al content x. FIG. 3 is a schematic diagram showing an example in which the total amount of AlCl ₃ and TiCl ₄ is constant and the value of AlCl ₃ /TiCl ₄ (ratio of % by volume) is periodically increased or decreased. It is a schematic diagram which shows an example which superimposed the waveform (triangular wave shape) with a relatively long period, and the waveform (pulse shape) with a relatively short period.

The present invention is described in detail below. In addition, when a numerical range is expressed by "-" in the present specification and claims, the range includes upper and lower numerical values.

Average layer thickness of TiAlCN layer:
The hard coating layer of the present invention includes at least a TiAlCN layer. This TiAlCN layer has high hardness and excellent chipping resistance and wear resistance, and the effect is particularly noticeable when the average layer thickness is 1.0 to 20.0 μm. This is because if the average layer thickness is less than 1.0 μm, the layer thickness is too thin to ensure sufficient wear resistance over long-term use. Crystal grains in the layer tend to coarsen, and chipping tends to occur.
Therefore, the average layer thickness was set to 1.0 to 20.0 μm. More preferably, the average layer thickness is 3.0 to 15.0 μm.

Average composition of TiAlCN layer:
The composition of the TiAlCN layer in the present invention is represented by the composition formula: (Ti _1-x Al _x )(C _y N _1-y ),
The average of the content ratio x of Al in the total amount of Ti and Al (hereinafter referred to as “average of Al content ratio”) x _avg is
The average content ratio y of C in the total amount of C and N (hereinafter referred to as “average of C content ratio”) y _avg is
They are defined to satisfy 0.60≦x _avg ≦0.90 and 0.000≦y _avg ≦0.005 (where x _avg and y _avg are both atomic ratios).

The reason is as follows.
When the average x _avg of the Al content is less than 0.60, the TiAlCN layer is inferior in hardness, so that when subjected to high-speed cutting of alloy steel or the like, the wear resistance is not sufficient. If it exceeds 90, hexagonal TiAlCN crystal grains are precipitated, resulting in deterioration of wear resistance. Therefore, 0.60 ≤ x _avg ≤ 0.90, but more preferably 0.70 ≤ x _avg ≤ 0.90.
The reason why the average y _avg of the C content ratio is set to 0.000≦y _avg ≦0.005 is that the hardness can be improved while maintaining the chipping resistance within the above range.

The average x _avg of the Al content ratio of the TiAlCN layer is obtained by using Auger Electron Spectroscopy (AES) and irradiating an electron beam from the longitudinal section side of a sample whose cross section is polished, and 5 lines in the film thickness direction. This is the average of the analysis results of Auger electrons obtained by line analysis of .

Also, the average y _avg of the C content ratio is determined by secondary ion mass spectrometry (SIMS). That is, in a sample having a polished sample surface, an ion beam is irradiated in a range of 70 μm×70 μm from the surface side of the TiAlCN layer, and surface analysis by the ion beam and etching by the sputtered ion beam are alternately repeated, thereby increasing the depth direction. Composition measurements are taken. First, the average of the data obtained by measuring the length of at least 0.5 μm at a pitch of 0.1 μm or less from a portion of the TiAlCN layer intruded by 0.5 μm or more in the depth direction of the layer is obtained. Furthermore, the average y _avg of the C content ratio is obtained by averaging the results obtained by repeatedly calculating this at least at five locations on the sample surface.

Repeated change of Al content in TiAlCN layer:
When the longitudinal section of the TiAlCN layer is divided into n sections (section 1, . The content ratio of Al in the total amount of Ti and Al in crystal grains having a crystal) (hereinafter referred to as “Al content ratio”) x The average interval (average period) of repeated changes is 50 to 200 nm. It is preferable that there is a repetitive change (long-period change) in the Al content x and a repetitive change (short-period change) in the Al content x at short intervals with an average period of 1 to 20 nm.

Here, the repetitive change in the Al content rate x means that almost the same value of the Al content rate x can be observed at almost constant intervals (periods) at most positions in the measurement section, and is referred to as a long-period change. Graphing the fact that it has a short-period change shows that a change similar to a superposition of a short-period sine wave with a constant amplitude and a long-period sine wave with a constant amplitude, as shown in FIG. show. Then, when the section is observed with a transmission electron microscope (TEM), this almost constant interval allows repeated changes in the Al content ratio x to be observed, and both the long-period change and the short-period change are minimized. direction (referred to as observation direction. In the schematic diagram of FIG. 2, it is the direction away from the tool base, and is not necessarily perpendicular to the surface of the tool base, but is also referred to as the tool surface direction.).

The repetitive change (long-period change) of the Al content x at long intervals is as follows. That is, in the observation direction, repeated changes in the Al content x are measured by line analysis, which will be described later, and the changes are linearly approximated. That is, a straight line is drawn across the curve so that the area of the area surrounded by the straight line and the curve showing repeated changes is equal above and below the straight line. The slope of this approximation straight line (x _m : straight line m in FIG. 1) may increase, decrease, or be substantially constant. Then, when the maximum value or the minimum value is obtained for each region where this x _m crosses the curve showing the repeated change of the Al content x, if the difference between the adjacent maximum value and the minimum value is 0.10 or more, The maximum value and the minimum value are called the maximum value of the long-period change and the minimum value of the long-period change, respectively. Further, the interval between adjacent maximum values or between adjacent minimum values is called a long period. The long-period average value d _Lavg is preferably 50 to 200 nm (see FIG. 1).

The reason why the long-period average value d _Lavg is set in this range is that when the average value d Lavg of the long period is less than 50 nm, the crystal grains having a NaCl-type face-centered cubic structure undergo a long-period change in addition to a short-period change as a change in the Al content x. If the period exceeds 200 nm, crack growth cannot be suppressed, and chipping resistance and peeling resistance decrease. be. The long-period average value d _Lavg is more preferably 80 to 180 nm.

A repetitive change in the Al content x at short intervals (short-period change) is a change in which an increase and a decrease in the Al content x are repeated adjacently when a line analysis described later is performed in the observation direction. In this adjacent repetition, the interval between adjacent maximum values or minimum values is called a short period, and the average value d _Savg of this short period is preferably 1 to 20 nm (see FIG. 1 ).

The reason why the short-period average value d _Savg is set in this range is that when it is less than 1 nm, a high Al content region (a range above the approximate straight line x _m in a curve showing repeated changes in the Al content rate x) and a low Al content As the number of interfaces in the region (the range below the approximate straight line x _m in the curve showing repeated changes in the Al content x) increases, local adhesion strength decreases and plastic deformation tends to occur, so chipping resistance Alternatively, the hardness is lowered, and if the thickness exceeds 20 nm, a sufficient cushioning action for suppressing crack propagation during cutting cannot be expected. The short-period average value d _Savg is more preferably 3 to 15 nm.

Determination of the long-cycle average d _Lavg and the short-cycle average d _Savg :
The long-period average value d _Lavg and the short-period average value d _Savg are measured as follows.
(1) Sections are defined by dividing the longitudinal section of the TiAlCN layer in the layer thickness direction at intervals of 0.5 μm from the interface with the tool base toward the tool surface. However, the section closest to the tool surface may have a thickness of less than 0.5 μm.

(2) If the average layer thickness of the TiAlCN layer is 5.0 μm or less, all the divided sections, if the average layer thickness exceeds 5.0 μm, at least 10 sections (however, section 1 (the most (closest section) and section n (the section closest to the tool surface) are preferably measured.

(3) All of the sections to be measured are observed with a TEM, and after confirming that repeated changes in the Al content x can be observed, the observation direction is determined and five lines are analyzed (described later). measurement interval of 0.5 nm or less).

(4) Graph the relationship between the position in the observation direction and the repeated change in the Al content ratio x, measure the interval between repeated changes in the Al content ratio x in the entire range where the line analysis was performed, and average the long period as described above. A value d _Lavg and a short period average value d _Savg are obtained. Here, in order to obtain this average value, as described above, the repeated change in the Al content x is measured, and the area of the region surrounded by the curve showing this repeated change and the straight line is above and below the straight line. Linearize the curve by drawing a straight line across the curve so that it is equal. It goes without saying that a well-known measurement noise removal method (for example, a moving average method) is performed in graphing.

Difference in Al content ratio between long-period change and short-period change Calculate the average difference Δx _Li between the maximum value and the minimum value for each measurement target section (i) of the Al content ratio change in the section in the long-period change , the average value Δx _Lavg averaged over all measured sections (that is, substantially averaged over the entire hard coating layer) is preferably 0.12 to 0.15. The reason for this is that when the ratio x is less than 0.12, the TiAlCN layer has a long-period change in addition to a short-period change as a change in the Al content x, which reduces the effect of suppressing crack growth during cutting. If it exceeds 0.15, the lattice strain of crystal grains becomes too large, lattice defects increase, and hardness decreases.

Further, the average difference Δx _Savg of the average difference Δx _Si between the maximum value and the minimum value, which is the short-period change in each measurement target section (i), is preferably 0.03 to 0.07. The reason for this is that if it is less than 0.03, the effect of suppressing crack growth during cutting is reduced and the chipping resistance is reduced. This is because the lattice strain generated at the interface between the regions becomes too large, and becomes a starting point of fracture during cutting, resulting in abnormal damage such as chipping. Δx _Savg is more preferably 0.05 to 0.07.

Change in Δx _Li In each measurement target section (i), the average difference Δx _Li between the adjacent maximum value and the minimum value increases as the distance from the tool base increases,
When n≧3,
(Average value of Δx _Li from interval 1 to interval [n/3]) < (Average value of Δx _Li from interval [n/3] + 1 to interval [2n/3]) < (Interval [2n/3] +1 to interval n average value of Δx _Li ),
i.e.
Δx _L1 +Δx _L2 +...+Δx _L[n/3] )/[n/3]<(Δx _L[n/3] +Δx _L[n/3]+1 +...+Δx _L[2n/3] )/([2n/3]-[n/3])<(Δx _L[2n/3] +Δx _L[2n/3]+1 +...+Δx _Ln )/(n-[2n/3])
satisfies the
When n=2, Δx _L1 <Δx _L2
is preferably satisfied. The reason for this is that if this condition is satisfied, the difference in strain between the TiAlCN layer and the layer immediately below it (lower layer described later) or the tool base is suppressed, so excellent peeling resistance is exhibited.
Note that [i] (i=n/3, 2n/3) represents a Gaussian symbol.
The Gaussian symbol [i] is a mathematical symbol representing the largest integer not exceeding i, in other words [i] refers to a numerical value defined by m≦i<m+1, where m is an integer.
For example, if n=23, ie n/3=7.7 and 2n/3=15.3, then [n/3]=7 and [2n/3]=15.

Area ratio of crystal grains having a NaCl-type face-centered cubic structure in the TiAlCN layer:
It is preferable that the area ratio of crystal grains having a NaCl-type face-centered cubic structure in the TiAlCN layer is 80 area % or more. As a result, the area ratio of crystal grains having a high hardness NaCl type face-centered cubic structure is relatively higher than the crystal grains having a hexagonal crystal structure, and the effect of improving the hardness of the TiAlCN layer is obtained. can be done. This area ratio is more preferably 90 area % or more.

Here, the area ratio of crystal grains having a NaCl-type face-centered cubic crystal structure is measured as follows. In the longitudinal section of the TiAlCN layer (the cross section perpendicular to the surface of the tool base), the measurement range is 100 μm in the direction parallel to the surface of the tool base and the length of the layer thickness in the direction perpendicular to the surface of the tool base. This measurement range is polished, and an electron beam backscatter diffraction (EBSD) is used to irradiate the polished surface with an electron beam at an incident angle of 70 degrees and an acceleration voltage of 15 kV at an irradiation current of 1 nA. The crystal structure of each crystal grain is analyzed to see if it has a NaCl-type face-centered cubic crystal structure based on the electron beam backscatter diffraction image obtained by irradiating the crystal grains at intervals of 0.01 μm. At this time, when there is an orientation difference of 5 degrees or more between adjacent measurement points (pixels), the area is defined as a grain boundary, and a region surrounded by the grain boundary is defined as one crystal grain. However, a single pixel that has an orientation difference of 5 degrees or more with respect to all adjacent pixels is not treated as a crystal grain, but a crystal grain in which two or more pixels are connected is treated as a crystal grain.

Area ratio in longitudinal section of crystal grains of NaCl type face-centered cubic structure with long-period change and short-period change:
The area ratio of the NaCl-type face-centered cubic structure crystal grains having long-period changes and short-period changes is preferably 50 area % or more in the longitudinal section. The reason for this is that when the area ratio is 50 area % or more, the effect of suppressing crack growth is further increased, and the effect of improving toughness is further improved. This area ratio is more preferably 70 area % or more.

The area ratio of crystal grains having a NaCl-type face-centered cubic structure with long-period changes and short-period changes is measured as follows. Using TEM, repeated changes in Al content x confirmed by changes in image contrast corresponding to repeated changes in Al content x in a 1 μm × 1 μm image (either long-period change or short-period change only (including the case of ) is specified. Furthermore, line analysis, which will be described later, is performed on all the crystal grains having repeated changes in the Al content x, and the presence or absence of long-period changes and short-period changes is confirmed. Then, the areas of the crystal grains having both the long period change and the short period change are calculated, and the area ratios occupying the observation area of 1 μm × 1 μm are obtained in at least 5 fields of view, and the average value thereof is the long period change in the present invention. It can be obtained as the area of the crystal grain having short period change.

Here, the line analysis for measuring the Al content ratio x means that the longitudinal section of the sample prepared by polishing is analyzed by Energy Dispersive X-ray Spectrometry (EDS) using a TEM. Analysis is performed along five lines in the direction away from (tool surface direction), and the obtained analysis results are averaged. However, the measurement range in the observation direction has a length of at least 100 nm and is longer than the average period d _Lavg of the long period change (when the average period d _Lavg of the long period change is 200 nm Measurement is performed with a length of 200 nm and an average period _dLavg of the long-period variation of 50 nm, or 100 nm if there is no long-period variation).

Other layers:
As a hard coating layer, the TiAlCN layer of the present invention has sufficient wear resistance, chipping resistance and spallation resistance, but Ti carbide, nitride, carbonitride, carbide and carbonitride layers. Tooling a lower layer consisting of one or more layers of nitride oxide layers and including a Ti compound (not limited to stoichiometric compounds) layer having a total average layer thickness of 0.1 to 20.0 μm When provided adjacent to a substrate and/or when a layer comprising at least an aluminum oxide layer is provided as a top layer on top of said TiAlCN layer with a total average layer thickness of 1.0 to 25.0 μm, Together with the effects of these layers, even better wear resistance, chipping resistance, and peeling resistance can be exhibited.

Here, if the total average layer thickness of the lower layer is less than 0.1 μm, the effect of the lower layer is not sufficiently exhibited, while if it exceeds 20.0 μm, the crystal grains of the lower layer tend to coarsen, causing chipping. easier to do. When the total average layer thickness of the upper layer including the aluminum oxide layer is less than 1.0 μm, the effect of the upper layer is not sufficiently exhibited. , chipping is more likely to occur.

Tool substrate:
As the tool substrate, any conventionally known substrate for this type of tool substrate can be used as long as it does not interfere with the achievement of the object of the present invention. For example, cemented carbide (WC-based cemented carbide, WC, containing Co, or containing carbonitrides such as Ti, Ta, Nb, etc.), cermets (TiC, TiN , TiCN as a main component, etc.), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cBN sintered body, or diamond sintered body.

Production method:
The TiAlCN layer of the present invention having a long-period change and a short-period change in the Al content x is, for example, a carbide layer, a nitride layer, or a carbonitride layer of Ti, which is the tool substrate or the lower layer on the tool substrate. , on at least one layer of the carbonate layer and the carbonitride layer, for example, a gas group A consisting of NH ₃ and H ₂ and AlCl ₃ , TiCl ₄ , N ₂ , C ₂ H ₄ and H ₂ It can be obtained by supplying two kinds of reaction gases consisting of gas group B and B as follows. That is, in order to form a long-period change in the Al content ratio x, the composition of the gas group A is not changed, and the total amount of AlCl ₃ and TiCl ₄ in the gas group B is constant, and AlCl ₃ /TiCl ₄ (volume % ratio ) is periodically increased or decreased (eg triangular wave, square wave, etc.) and the difference between the maxima and minima of AlCl ₃ /TiCl ₄ is increased (see FIG. 3). Further, in order to form the short-period change, the compositions of both the gas group A and the gas group B are not changed (the values of AlCl ₃ and TiCl ₄ which are changed to form the long-period change are not further changed). ), supplied with a predetermined phase difference.
Since the gas supply method for giving a long period change is combined with the gas supply method for giving a short period change, the overall gas change is as if a waveform with a relatively long period and a waveform with a relatively short period. (pulse waves) are superimposed (see FIG. 4).

Reaction gas composition (% by volume):
Common to both long-term and short-term changes:
Gas group A: NH ₃ : 2.0 to 5.0%, H ₂ : 65 to 75%
Gas group B: AlCl ₃ : 0.52 to 0.76%, TiCl ₄ : 0.08 to 0.53%,
N ₂ : 0.0 to 12.0%, C ₂ H ₄ : 0.0 to 0.5%, H ₂ : Residual reaction atmosphere pressure: 4.0 to 5.0 kPa
Reaction atmosphere temperature: 700-900°C
Long-term variation:
Period of increase and decrease of AlCl ₃ /TiCl ₄ : 10.0-40.0 seconds Difference between maximum and minimum values of AlCl ₃ /TiCl ₄ : 0.44-6.23 (at the start)
0.65 to 147 (end time)
Short cycle change:
Gas supply cycle: 1.00 to 5.00 seconds Gas supply time per cycle: 0.10 to 0.20 seconds Supply phase difference between gas group A and gas group B: 0.05 to 0.15 seconds

Next, examples will be described.
Here, as a specific example of the coated tool of the present invention, an insert cutting tool using a WC-based cemented carbide as a tool substrate will be described. and the same applies to drills and end mills.

As raw material powders, WC powder, TiC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, ZrC powder, TiN powder and Co powder, all having an average particle size of 1 to 3 μm, were prepared. It was blended according to the formulation shown in Table 1, further wax was added, ball mill mixed in acetone for 24 hours, and dried under reduced pressure. Vacuum sintered in a vacuum of 5 Pa at a predetermined temperature within the range of 1370 to 1470° C. for 1 hour, and after sintering, a tool substrate made of WC-based cemented carbide having an insert shape of ISO standard SEEN1203AFSN. Tool substrates A to C and tool substrates D to F made of WC-based cemented carbide with insert geometry of ISO standard CNMG120412 were produced respectively.

Next, a TiAlCN layer was formed on the surfaces of these tool substrates A to F by CVD using a CVD apparatus to obtain coated tools 1 to 16 of the present invention shown in Table 5.
The film formation conditions are as described in Table 2, but are generally as follows. With the total amount of AlCl ₃ and TiCl ₄ constant, the value of AlCl ₃ /TiCl ₄ (ratio of % by volume) is changed in a triangular wave form from the starting value shown in Table 2, and the maximum value of AlCl ₃ /TiCl ₄ and A linearly increasing difference from the local minimum was supplied. Further, in order to form the short-period change, the compositions of both the gas group A and the gas group B are not changed (the values of AlCl ₃ and TiCl ₄ which are changed to form the long-period change are not further changed). ), supplied at a given phase difference. Note that % of the gas composition is volume % (the sum of gas group A and gas group B is taken as a whole).

Reaction gas composition (% by volume):
Common to both long-term and short-term changes:
Gas group A: NH ₃ : 2.0 to 5.0%, H ₂ : 65 to 75%
Gas group B: AlCl ₃ : 0.52 to 0.76%, TiCl ₄ : 0.08 to 0.53%,
N ₂ : 0.0 to 12.0%, C ₂ H ₄ : 0.0 to 0.5%, H ₂ : Residual reaction atmosphere pressure: 4.0 to 5.0 kPa
Reaction atmosphere temperature: 700-900°C
Long-term variation:
Period of triangular change of AlCl ₃ /TiCl ₄ : 10.0-40.0 seconds Difference between maximum and minimum values of AlCl ₃ /TiCl ₄ : 0.44-6.23 (at the start)
0.65 to 147 (end time)
Short cycle change:
Gas supply cycle: 1.00 to 5.00 seconds Gas supply time per cycle: 0.10 to 0.20 seconds Supply phase difference between gas group A and gas group B: 0.05 to 0.15 seconds

For coated tools 4 to 8, 11, 13, 15, and 16 of the present invention, the lower layer and/or upper layer shown in Table 4 was formed under the film forming conditions shown in Table 3.

For the purpose of comparison, a hard coating layer containing a TiAlCN layer shown in Table 5 was vapor-deposited on the surfaces of the tool substrates A to F under the conditions shown in Table 2 to form a comparative coated tool 1. ~16 was produced.
For comparative coated tools 4 to 8, 11, 13, 15, and 16, the lower layer and/or upper layer shown in Table 4 were formed under the forming conditions shown in Table 3.

Further, the average Al content x _avg and the average C content y _avg were determined for the hard coating layers of the coated tools 1 to 16 of the present invention and the comparative coated tools 1 to 16 by the method described above. In addition, the average interval d _Lavg of the long-period change, the average interval d _Savg of the short-period change, Δx _Lavg , Δx _Savg , Δx _Li , the area ratio of the crystal grains of the NaCl type face-centered cubic structure, and the period of the Al content ratio The area ratio (area %) of NaCl-type crystal grains having a face-centered cubic structure having a characteristic change was determined.
Furthermore, the average layer thickness was determined by scanning a longitudinal section (a section perpendicular to the surface of the tool substrate) of each constituent layer of the coated tools 1 to 16 of the present invention and the comparative coated tools 1 to 16 with an appropriate scanning electron microscope. Observation was carried out at a selected magnification (magnification of 5000 times), and the thickness of the layer at five points within the observation field was measured and averaged.
Table 5 shows the results.

Subsequently, for the coated tools 1 to 8 of the present invention and the comparative coated tools 1 to 8, the various tool substrates A to C (ISO standard SEEN 1203 AFSN shape) were all fixed to the tip of the alloy steel cutter with a cutter diameter of 125 mm. In the state of being clamped with a tool, the following high-speed dry face milling and center-cut cutting test of alloy steel was performed, and the flank wear width of the cutting edge was measured. Table 6 shows the results of the cutting test. As for the comparative coated tools 1 to 8, the life was reached before the end of the cutting time due to the occurrence of chipping, so the time until the life is reached is shown.

Cutting test 1: Dry high-speed face milling, center cut cutting test Cutter diameter: 125 mm
Work material: JIS SCM440 block material with a width of 100 mm and a length of 400 mm Rotational speed: 1019 min ^-1
Cutting speed: 400m/min
Notch: 2.5mm
Feed: 0.25 mm/blade Cutting time: 20 minutes (normal cutting speed is 200 m/min)

In addition, with respect to the coated tools 9 to 16 of the present invention and the comparative coated tools 9 to 16, each of the various coated tools D to F (ISO standard CNMG120412 shape) was screwed to the tip of the alloy steel cutting tool with a fixing jig. In the stopped state, the following dry high-speed interrupted cutting test of high carbon steel was performed to measure the flank wear width of the cutting edge. Table 7 shows the results of the cutting test. As for the comparative coated tools 9 to 16, the life was reached before the end of the cutting time due to the occurrence of chipping, so the time until the life is reached is shown.

Cutting test 2: Dry high-speed interrupted cutting Work material: JIS S55C round bar with 4 equally spaced longitudinal grooves Cutting speed: 400 m/min
Notch: 1.5mm
Feed amount per blade: 0.2 mm/blade Cutting time: 5 minutes (normal cutting speed is 200 m/min)

From the results shown in Tables 6 and 7, the coated tools 1 to 16 of the present invention all have excellent chipping resistance and peeling resistance in the hard coating layer. Even when used for interrupted cutting, it does not cause chipping and exhibits excellent wear resistance over a long period of time. On the other hand, the comparative coated tools 1 to 16, which did not satisfy even one of the items specified for the coated tool of the present invention, caused chipping when used for high-speed interrupted cutting of alloy steel or high carbon steel. , the service life is reached in a short time.

As described above, the coated tool of the present invention can be used as a coated tool for high-speed interrupted cutting of materials other than alloy steel and high-carbon steel, and exhibits excellent chipping resistance and peeling resistance over a long period of time. Therefore, it is possible to fully satisfy high performance cutting equipment, labor saving and energy saving in cutting, and cost reduction.

Claims (2)

A surface-coated cutting tool having a hard coating layer on the surface of the tool substrate,
(a) the hard coating layer includes a composite nitride layer or composite carbonitride layer of Ti and Al having an average layer thickness of 1.0 to 20.0 μm,
(b) The composite nitride layer or composite carbonitride layer of Ti and Al has a composition of
When represented by the composition formula: (Ti _1-x Al _x ) (C _y N _1-y ),
The average x _avg of the content ratio x of Al in the total amount of Al and Ti of Al satisfies 0.60 ≤ x _avg ≤ 0.90, and the content of C in the total amount of C and N of C The average y _avg of the ratio y is 0.000 ≤ y _avg ≤ 0.005 (where x, y, x _avg , y _avg are atomic ratios),
(c) In the crystal grains having a NaCl-type face-centered cubic structure in the longitudinal section of the composite nitride layer or composite carbonitride layer of Ti and Al, the content ratio of Al to the total amount of Al and Ti in the Al x has a long-period variation with an average period d _Lavg of 50-200 nm and a short-period variation with an average period d _Savg of 1-20 nm (d _Lavg , d _Savg is the direction of the minimum period of variation of x value measured at
(d) n sections (section 1, . , n), the average value Δx _Lavg of the average difference Δx _Li between the maximum and minimum values of adjacent x in the long-period change in each interval is 0.12 to 0.15,
The average value Δx _Savg of the average difference Δx _Si between the maximum value and the minimum value of adjacent x in the short period change in each section is 0.03 to 0.07,
(e) The average difference Δx _Li between the maximum value and the minimum value of adjacent x in the long-period change in each section is, as it moves away from the tool base,
When n is 3 or more, (Average value of Δx _Li from interval 1 to interval [n/3]) <(Average value of Δx _Li from interval [n/3]+1 to interval [2n/3]) satisfying <(average value of Δx _Li from interval [2n/3]+1 to interval n),
When n is 2, Δx _L1 <Δx _L2
is increased to satisfy
(f) The composite nitride layer or composite carbonitride layer of Ti and Al is occupied by crystal grains of a composite nitride or composite carbonitride of Ti and Al having a NaCl-type face-centered cubic structure in a longitudinal section. The ratio is 80 area% or more, and the ratio of the crystal grains having the long period change and the short period change is 50 area% or more.
A surface-coated cutting tool characterized by: The surface-coated cutting tool according to claim 1, wherein the crystal grains having the NaCl-type face-centered cubic structure having the long period change and the short period change account for 70 area% or more in the longitudinal section. .

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