JP7043869B2 - Surface coating cutting tool with excellent welding resistance and abnormal damage resistance for the hard coating layer - Google Patents

Description

INDUSTRIAL APPLICABILITY According to the present invention, the hard coating layer has excellent welding resistance, plastic deformation resistance, and abnormal damage resistance in high feed cutting of heat-resistant steel, in which a high load acts on the cutting edge. It relates to a surface-coated cutting tool having excellent cutting performance over a long period of use.

Conventionally, in general, in the cutting of various types of steel, a Ti compound layer such as a carbonitride (TiCN) layer of Ti formed by chemical vapor deposition as a lower layer is provided on the surface of a cemented carbide substrate such as a tungsten carbide group. , A coating tool having a hard coating layer having an aluminum oxide layer formed by chemical vapor deposition as an upper layer is used.
However, in recent years, while high efficiency is required in the cutting of various steels, the conventional coated tool has a problem of shortening the tool life due to welding or abnormal damage.

Therefore, for example, Patent Document 1 proposes to extend the life of a cutting tool or the like by forming a TiZrN hard coating layer having high hardness and excellent wear resistance by using a sputtering method or a plasma CVD method. Has been done.
Further, in Patent Document 2, as a cutter used when cutting a steel pipe, a ceramic coating layer made of TiZrN or the like is provided on a cemented carbide base material having a hard phase of WC and a metal bonding phase of Co, Ni, and Cr. It has been proposed to prevent diffusion between the work piece and the cutter, and to improve the deterioration of productivity and product quality due to welding and blade spillage that have conventionally occurred at the cutting edge when cutting a steel pipe.
Further, Patent Document 3 proposes that a cutting tool in which TiZrN, TiHfN, and TiZrHfN having an fcc structure are formed on a substrate by a CVD method has a longer tool life, particularly when used for dry turning of stainless steel. Has been done.

Japanese Unexamined Patent Publication No. 3-267361 Japanese Unexamined Patent Publication No. 7-237030 U.S. Patent Publication No. 2016/0298233

In recent years, there has been a strong demand for labor saving and energy saving in cutting, and along with this, coated tools have come to be used under more severe conditions, and are excellent in high feed cutting of heat-resistant steel. It is required to have welding resistance, plastic deformation resistance and abnormal damage resistance.
However, regarding the covering tools proposed in Patent Document 1 and Patent Document 2, there is no description about the application of heat-resistant steel to high-feed cutting, and it is also proposed in Patent Document 3. The coating tools having TiZrN, TiHfN or TiZrHfN as the coating layer have a certain level of effect on welding resistance when used for high-feed cutting of heat-resistant steel, but these coating layers. Does not withstand plastic deformation, and does not have sufficient plastic deformation resistance and abnormal damage resistance such as abnormal wear due to falling of particles from the coating layer, so there is still a problem that the life is reached early. Had.

Therefore, from the above-mentioned viewpoint, the present inventors have excellent welding resistance over a long period of use even when the covering tool is used for high feed cutting of heat-resistant steel in which a high load acts on the cutting edge. The following findings were obtained as a result of diligent research on coated tools that have properties, plastic deformation resistance, and abnormal damage resistance, and that improve the tool life.
That is, in the surface-coated cutting tool, the present inventors have limited conditions after forming at least one layer of a compound layer containing Ti or Zr as a lower layer on the surface of the tool substrate and containing carbon and nitrogen. Then, a composite nitride layer of Ti and Zr or a composite nitride layer of Ti, Zr and Hf is formed, and {112 of each crystal grain of such composite nitride layer with respect to the normal on the surface of the tool substrate. } In the range of the inclination angle in the normal direction of the surface in the range of 0 to 45 degrees, the measurement is performed as the number distribution (inclination angle number distribution) in the inclination angle division divided into predetermined pitch intervals (for example, every 0.25 degrees). When performed, it has the highest peak of the number of tilt angles in any of the tilt angle divisions divided by a specific pitch in the region where the tilt angle is 0 to 10 degrees with respect to the normal direction of the tool substrate. The number of tilt angles existing in the region of 0 to 10 degrees with respect to the normal direction of the tool substrate occupies 35% or more of the total measurement region, and the orientation of the crystal grains of the composite nitride layer with respect to the {112} plane. When the tendency is high, a structure that is less likely to cause plastic deformation can be obtained, and in addition, by forming a structure having vertically elongated crystal grains that are directed in the direction perpendicular to the substrate surface, the grain boundaries in the direction parallel to the substrate surface are reduced. It is possible that the crystal grains are less likely to fall off, and further, when a very small amount of chlorine is contained in the composite nitride layer, for example, when the upper limit thereof is 0.030 at% or less, the coating layer is formed. It has been found that the lubrication effect can be exhibited without causing brittleness of the normal, and heat generation due to friction during cutting can be suppressed, so that plastic deformation of the coating layer is less likely to occur and the falling off of the crystal grains can be further suppressed. ..
A coated cutting tool having such a composite nitride layer as a hard coating layer has excellent welding resistance, plastic deformation resistance, and abnormal damage resistance, and therefore has long-term use for high feed cutting of heat-resistant steel. It has been found that the tool life is improved over the use of.

The present invention has been made based on the above findings.
"(1) In a surface-coated cutting tool in which a hard coating layer is formed on the surface of a tool substrate made of a WC-based cemented carbide or a TiCN-based cermet.
(A) The hard coating layer has at least a lower layer and a composite nitride layer from the surface side of the tool substrate.
(B) The lower layer has at least one compound layer containing Ti or Zr and containing carbon and nitrogen, and the total average film thickness thereof is 1.0 μm or more.
(C) The composite nitride layer includes a composite nitride layer of Ti and Zr having an average thickness of 0.5 to 20 μm or a composite nitride layer of Ti, Zr and Hf.
(D) When the average composition of the composite nitride layer is represented by the composition formula (Ti _(1-x) Zr _xy Hf _{x (1-y)} ) N,
The content ratio x of the total amount of Zr and Hf in the total amount of Ti, Zr and Hf, and the content ratio y of the total amount of Zr and Zr and Hf (however, x and y are both atomic ratios). ) Are composite nitride layers satisfying 0.05 ≦ x ≦ 0.95 and 0 <y ≦ 1.0, respectively.
(E) In the composite nitride layer, an electric field emission type scanning electron microscope and an electron beam backscattering diffractometer are used to form individual crystal grains having a rock salt type cubic crystal lattice existing within the measurement range of the cross-sectional polished surface. By irradiating with an electron beam, the inclination angle formed by the normal of the {112} plane, which is the crystal plane of the crystal grain, is measured within the range of 0 to 45 degrees with respect to the normal of the surface of the tool substrate. When the tilt angle is divided into pitches of 0.25 degrees and the tilt angle distribution graph is created by summing up the degrees existing in each division, the tilt angle with respect to the normal of the surface of the tool substrate is 0. The highest peak exists in the tilt angle division within the range of 10 degrees, and the total number of degrees existing in the tilt angle division within the range of 0 to 10 degrees is 35% or more of the total frequency in the tilt angle distribution graph. Occupy,
(F) The surface-coated cutting tool, wherein the composite nitride layer has an area ratio of 50% or more occupied by vertically elongated crystal grains having an aspect ratio of 2 or more in a vertical cross section.
(2) The surface-coated cutting tool according to (1), wherein the composite nitride layer contains 0.030 atomic% or less of chlorine. It is characterized by.

Next, the covering tool of the present invention will be described in detail.

Hard coating layer;
The hard coating layer according to the present invention has at least a lower layer and a composite nitride layer from the surface side of the tool substrate, and the lower layer contains a compound layer containing Ti or Zr and containing carbon and nitrogen. It comprises at least one layer, and the composite nitride layer includes a composite nitride layer of Ti and Zr or a composite nitride layer of Ti, Zr and Hf.
If necessary, as other layers, an intermediate layer 1 is provided between the tool substrate and the lower layer, an intermediate layer 2 is provided between the lower layer and the composite nitride layer, and an upper layer is provided on the composite nitride layer. Can be provided.
Here, if the average thickness of the hard coating layer is less than 1.5 μm, long-term wear resistance cannot be exhibited, while if it becomes thicker than 30 μm, defects and chipping occur in the entire hard coating layer. It is desirable to set it to 1.5 to 30 μm because it is easy.
The average thickness of the hard coating layer can be measured, for example, using an SEM (scanning electron microscope) or a TEM (transmission electron microscope) in a cross section perpendicular to the tool substrate.

Lower layer;
The lower layer formed on the tool substrate is a compound layer containing Ti or Zr and containing carbon and nitrogen, for example, a carbonitride layer of Ti, a carbonitride oxide layer, a carbonitride boride layer, or Zr. By having at least one layer composed of a carbonitride layer, a carbonitride oxide, a carbonitride boride layer, or a Ti and Zr carbonitride layer, a carbonitride oxide layer, a carbonitride boride layer, etc., the tool substrate can be used. Since the adhesion to the composite nitride layer of Ti and Zr or the composite nitride layer having the composite nitride layer of Ti, Zr and Hf can be enhanced, the occurrence of abnormal damage such as chipping and peeling can be suppressed. can.
Further, by forming a composite nitride layer on the lower layer by a limited method described later, the composite nitride layer can be oriented on the {112} plane. The reason why the composite nitride layer is oriented on the {112} plane is that at least the outermost surface of the lower layer is oriented on the {112} plane, and the film formation method described later (that is, the film formation proceeds by the surface reaction). It is considered that the composite nitride layer inherited the orientation from the outermost surface of the lower layer by forming the composite nitride layer by the film forming method) in which the contribution of the gas phase reaction is almost nonexistent.
When the intermediate layer 2 is provided between the lower layer and the composite nitride layer, the intermediate layer 2 is, for example, a TiN layer, and by using the film forming method described later, the outermost surface of the lower layer is {112. } The orientation can be passed on to the composite nitride layer via the intermediate layer 2.
If the total average layer thickness of the lower layer is less than 1.0 μm, the film thickness is thin and the orientation planes are not aligned in the {112} orientation on the outermost surface of the lower layer, so that the composite nitride layer may be oriented {112}. It's difficult. On the other hand, if it exceeds 20 μm, the crystal grains are likely to be coarsened and chipping is likely to occur. Therefore, the total average layer thickness of the lower layer is preferably 1.0 to 20 μm.

Composite nitride layer;
(1) Average layer thickness and component composition The composite nitride layer arranged on the lower layer is a Ti and Zr composite nitride layer having an average layer thickness of at least 0.5 μm or more and 20 μm or less, or a composite of Ti, Zr and Hf. A nitride layer is included, and specifically, the composite nitride layer is represented by the composition formula (Ti _(1-x) Zr _xy Hf _{x (1-y)} ) N. It satisfies 0.05 ≦ x ≦ 0.95 and 0 <y ≦ 1.0, respectively.
Here, x represents the content ratio of the total amount of Zr and Hf in the total amount of Ti, Zr and Hf, and y represents the content ratio of Zr in the total amount of Zr and Hf. However, both x and y are atomic ratios.
In the composite nitride layer according to the present invention, the hardness is improved by the lattice strain caused by the difference in the lattice constant between TiN which is solid-solved and ZrN and HfN, but x is smaller than 0.05. Or, when x is larger than 0.95, sufficient lattice strain is not introduced and sufficient hardness cannot be secured. Therefore, the value of x is limited to 0.05 ≦ x ≦ 0.95.
Further, if the average layer thickness of the composite nitride layer is less than 0.5 μm, long-term wear resistance cannot be exhibited, while if it exceeds 20 μm, chipping and chipping are likely to occur, so that the hardness and chipping are likely to occur. It is preferably 0.5 to 20 μm, which exhibits an excellent effect from the viewpoint of wear resistance.
Hereinafter, the composite nitride layer is also referred to as a TiZrN nitride layer and a TiZrHfN nitride layer, or a TiZrN layer and a TiZrHfN layer.
Since the TiZrN nitride layer and the TiZrHfN nitride layer further contain a small amount of chlorine, a lubricating effect is exhibited, so that heat generation due to wear during cutting is reduced, and plastic deformation resistance is further improved.
Here, the chlorine content is added at 0.030 atomic% or less when the ratio of chlorine (Cl) to the total amount of Ti, Zr, Hf, N and Cl is expressed as atomic%. Is desirable.

(2) Inclined angle number distribution In the present invention, the inclined angle number distribution in the composite nitride crystal grain of the composite nitride layer is measured on the cross-sectional polished surface by using a field emission scanning electron microscope and an electron backscatter diffraction device. It can be measured by irradiating individual crystal grains having a rock salt type cubic crystal lattice existing in the range with an electron beam.
That is, specifically, the inclination angle formed by the normal of the {112} plane, which is the crystal plane of the composite nitride crystal grains in the composite nitride layer, is 0 to 45 with respect to the normal of the surface of the tool substrate. When a tilt angle number distribution graph is created, which measures within the range of degrees, divides the measured tilt angle into pitches of 0.25 degrees, and aggregates the degrees existing in each section, the tool substrate The highest peak exists in the tilt angle section in which the tilt angle with respect to the normal of the surface of the surface is in the range of 0 to 10 degrees, and the total number of degrees existing in the tilt angle section in the range of 0 to 10 degrees is the tilt. It occupies 35% or more of the total frequency in the angle distribution graph, and has a structure in which the composite nitride layer has a high orientation tendency with respect to the {112} plane of the crystal grains and is less likely to cause plastic deformation.
(3) Vertical crystal structure Further, as described above, the composite nitride layer according to the present invention has a vertically long crystal structure, so that particles are suppressed from falling off from the coating layer, and wear resistance and abnormal damage resistance are improved. Demonstrates excellent characteristics.
The vertically long crystal structure referred to here is the largest value in the height (long side) of the crystal grains in the layer thickness direction for each crystal grain when the vertical cross section of the composite nitride layer is observed. Is the maximum grain length (L), the width (short side) of the crystal grains in the direction perpendicular to the layer thickness direction, and the largest value is the maximum particle width (W), defined by L / W. A structure in which the area ratio of the crystal grains having an aspect ratio of 2 or more in the vertical cross section of the composite nitride layer is 50% or more.
The aspect ratio and the area ratio of the vertically elongated crystal grains are measured by, for example, an electron backscatter diffraction method (EBSD) for a longitudinal cross-sectional image obtained by cross-sectional observation at a magnification of 5000 using a scanning electron microscope (SEM). For each crystal grain, measure the major axis diameter (maximum particle length), minor axis diameter (maximum particle width), and vertical cross-sectional area, and obtain the aspect ratio from the major axis diameter and minor axis diameter, and then The ratio of the area of the vertical cross section to be measured to the total area of the vertical cross section of the crystal grain having an aspect ratio of 2 or more was obtained as the area ratio.

Other layers;
(1) Intermediate layer 1
In the present invention, by providing a Ti compound such as TiN or TiC as the intermediate layer 1 between the tool substrate and the lower layer, it is possible to improve the adhesion between the tool substrate and the lower layer.
(2) Intermediate layer 2
Further, in the present invention, an intermediate layer 2 such as a TiN layer and a TiC layer can be provided between the lower layer and the composite nitride layer, and in particular, the TiN layer is the outermost surface of the lower layer. It can inherit the orientation of the {112} plane and has excellent peel resistance.
It is considered that this is because the TiN layer has high adhesion strength in both the lower layer and the composite nitride layer and has high deformation followability.
Although the film forming conditions of the TiN layer are common to the intermediate layer 1 and the intermediate layer 2 (see Table 3), the intermediate layer 1 has a fine granular structure because the substrate components such as Co and C diffuse from the substrate. On the other hand, since diffusion unlike the intermediate layer 1 does not occur in the intermediate layer 2, it is considered that a highly oriented structure inheriting the structure of the lower layer was obtained as described above (see FIG. 2).
(3) Upper layer In the present invention, an upper layer such as an Al oxide, a titanium compound such as TiN or TiCN can be further provided on the composite nitride layer, and a peening treatment or the like is performed after the film formation. You can also.

Method of forming a hard coating layer;
The hard coating layer according to the present invention can be formed in the order of the lower layer and the composite nitride layer, for example, by using the film forming method shown below.
(1) Method for forming a film on the lower layer The lower layer of the hard coating layer has at least one compound layer containing Ti or Zr and containing carbon and nitrogen, and is formed by using an ordinary chemical vapor deposition method. A film can be formed by adjusting the reaction gas composition for each compound layer and the reaction atmosphere such as pressure and temperature within an appropriate range. (See Table 3 etc. described later.)
The compound layer containing Ti includes a carbonitride layer, a carbonitride oxide layer, or a carbonitride boride layer of Ti, and the compound layer containing Zr includes a ZrCN layer, a ZrCNO layer, a ZrCNB layer, and the like. Can be selected.
Further, as those containing both Ti and Zr, a TiZrCN layer, a TiZrCNO layer, a TiZrCNB layer and the like can be selected.

(2) Film formation method of composite nitride layer (TiZrN nitride layer or TiZrHfN nitride layer) TiZrN layer and TiZrHfN layer having the component composition specified in the present invention and having a specific inclination angle number distribution and a vertically long structure. As an example, can be formed, for example, by forming a film on the formed lower layer using a chemical vapor deposition method under the following conditions.
That is, as the film forming conditions of the TiZrN layer or the TiZrHfN layer, TiCl ₄ gas, ZrCl ₄ gas or ZrCl ₄ gas + HfCl ₄ gas, N ₂ gas, NH ₃ gas, H ₂ gas are used as raw materials, and the film forming temperature is set. It can be carried out using a CVD apparatus capable of periodic supply at 830 ° C. or higher and lower than 950 ° C., preferably 860 ° C. or higher and lower than 950 ° C., and the pressure condition is 6 kPa or higher and lower than 12 kPa.
However, since the mixing of TiCl ₄ gas and NH ₃ gas involves a rapid gas phase reaction, and the mixing of ZrCl ₄ gas and NH ₃ gas may also cause a gas phase reaction, composite nitride is used. There is a risk of imparting orientation to the {112} plane in the material layer and hindering the vertical lengthening of the composite nitride crystal grains, and the content of chlorine in the composite nitride layer increases, resulting in brittleness of the coating film. Since it may promote, the gas group is divided into gas group A, gas group B, and gas group C as follows, and in particular, after adjusting each gas group so that TiCl ₄ gas and NH ₃ gas do not mix, each gas group is adjusted. The above-mentioned problems are solved by sequentially performing each reaction with the reactions in the gas group A, the gas group B, the gas group C, and the gas group B as one unit cycle.
As described above, since the production of the tool of the present invention requires suppression of the gas phase reaction, for example, in a film forming method that promotes the gas phase reaction such as the plasma CVD method, the orientation toward the {112} plane is achieved. It is not preferable because it inhibits the growth of vertically elongated tissues.
[Film formation conditions]
1) Reaction gas composition (% by volume):
Gas group A: TiCl ₄ : 0.30 to 3.00, N ₂ : 25.00 to 75.00, H ₂ : Residual gas group B: ZrCl ₄ : 0.03 to 1.50, HfCl ₄ : 0. 00-1.00,
H ₂ : Remaining
However, ZrCl ₄ + HfCl ₄ : 0.03 to 1.70
Gas group C: NH ₃ : 0.30 to 1.50, H ₂ : Remaining 2) Supply cycle:
This is repeated with (gas group A → gas group B → gas group C → gas group B) as one cycle.
The supply time of each gas group is 2.0 seconds or more for all of the gas group A, the gas group B, and the gas group C, and the gas supply time per cycle is 8 seconds or more (preferably 8 seconds or more and 24 seconds or more). Below).
Since the film formation rate decreases as the gas supply time per cycle increases, the gas supply time per cycle is preferably 24 seconds or less.
The film thickness of the composite nitride layer is adjusted by increasing or decreasing the number of repetitions of the gas supply cycle (gas group A → gas group B → gas group C → gas group B).
3) Reaction atmosphere temperature: 830 ° C. or higher and lower than 950 ° C., preferably 860 ° C. or higher and lower than 950 ° C. 4) Reaction atmosphere pressure: 6 kPa or more and less than 12 kPa (3) In the present invention, the intermediate layer 1 is formed between the tool substrate and the lower layer, the intermediate layer 2 is formed between the lower layer and the composite nitride layer, and the upper layer is formed on the composite nitride layer. Can be done.
See paragraph 0013 and Table 3 below for the compounds to be formed and the conditions for forming the film.

In the surface-coated cutting tool according to the present invention, the TiZrN nitride layer or the TiZrHfN nitride layer, which is a composite nitride layer of the hard coating layer formed on the surface of the tool substrate, has a high {112} plane orientation ratio. It has high grain boundary strength, excellent plastic deformation resistance, and has a vertically long crystal structure, so that it has few grain boundaries in the direction parallel to the substrate and exhibits excellent effects that coating particles are less likely to fall off. It is something to do.
The TiZrN nitride layer or the TiZrHfN nitride layer further contains a small amount of chlorine to exert a lubrication effect and reduce heat generation of wear during cutting.
As described above, the surface-coated cutting tool according to the present invention is provided with plastic deformation resistance and abnormal damage resistance in addition to the conventional excellent welding resistance, so that it can be used for a long period of time in high feed cutting of heat-resistant steel. Throughout the use of, it exhibits the characteristics of having excellent cutting performance and improves the tool life.

It is a tilt angle number distribution graph of the {112} plane in the TiZrHfN nitride layer constituting the composite nitride layer of the hard coating layer of the surface coating cutting tool 11 of this invention. The whole schematic diagram of the cross-sectional structure SEM photograph of the hard coating layer layer of the surface covering cutting tool 11 of this invention is shown.

Next, the covering tool of the present invention will be specifically described with reference to Examples.

As raw material powders, WC powder, TiC powder, ZrC powder, TaC powder, NbC powder, Cr _{3C 2} powder, TiN powder, and Co powder having an average particle size of 1 to 3 μm are prepared, and these raw material powders are prepared. , Add wax to the compounding composition shown in Table 1, mix in a ball mill for 24 hours in acetone, dry under reduced pressure, press-mold into a green compact of a predetermined shape at a pressure of 98 MPa, and press-mold this green compact. Is vacuum sintered in a vacuum of 5 Pa at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour, and after sintering, a tool made of WC-based superhard alloy having an insert shape of ISO standard CNMG120408. The substrates A to C were produced, respectively.

In addition, as raw material powder, TiCN (TiC / TiN = 50/50 by mass ratio) powder, ZrC powder, TaC powder, NbC powder, Mo _2C powder, WC powder, all having an average particle size of 0.5 to 2 μm. , Co powder and Ni powder are prepared, these raw material powders are blended into the compounding composition shown in Table 2, wet-mixed with a ball mill for 24 hours, dried, and then press-molded into a green compact at a pressure of 98 MPa. This green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1500 ° C. for 1 hour, and after sintering, a tool substrate D made of TiCN-based cermet having an insert shape of ISO standard CNMG120408. E was prepared.

Then, each of these tool substrates A to E was charged into a chemical vapor deposition apparatus, and a film was formed in the order of a lower layer and a composite nitride layer to manufacture the coated tools 1 to 15 of the present invention, respectively.
At that time, if necessary, an intermediate layer 1 is provided between the tool substrate and the lower layer, an intermediate layer 2 is provided between the lower layer and the composite nitride layer, and an upper layer is provided on the composite nitride layer. Obtained by film formation.
(A) First, the intermediate layer 1 is formed directly or on the tool substrate of Table 1 or 2 shown in the tool substrate symbol of Table 5, and then Ti of the target layer thickness shown in Table 5 is formed as a lower layer. The compound layer or the Zr compound layer was vapor-deposited under the formation conditions shown in Table 3.
(B) Next, after forming the intermediate layer 2 directly or on the lower layer, the composite nitridation of the target layer thickness shown in Table 5 is performed according to the formation conditions shown in Table 4 based on the formation symbols in Table 5. The TiZrN layer or TiZrHfN layer, which is a physical layer, is formed by thin film deposition to produce the covering tools 2, 11, 13, 15 of the present invention, or the TiZrN layer or TiZrHfN layer is formed by thin film deposition, and then the upper layer is formed by thin film deposition. , The coated tools 1, 3 to 10, 12, and 14 of the present invention were manufactured, respectively.
The intermediate layer 1, the intermediate layer 2, and the upper layer were formed by forming a film under the conditions shown in Table 3.

Further, for the purpose of comparison, each of the tool substrates A to E is charged into the chemical vapor deposition apparatus by the same procedure as that of the covering tools 1 to 15 of the present invention, and the comparative example covering tools 1 to 10 are used by the following procedure. Each was manufactured. That is,
(A) A Ti compound layer having a target layer thickness shown in Table 6 is formed as a lower layer directly or after forming an intermediate layer 1 with respect to the tool substrate of Table 1 or Table 2 shown by the tool substrate symbol of Table 6. Alternatively, the Zr compound layer was vapor-deposited under the formation conditions shown in Table 3.
(B) Next, after forming the intermediate layer 2 directly or on the lower layer, based on the formation symbols in Table 6, the composite nitride with the target layer thickness shown in Table 6 under the formation conditions shown in Table 4. Comparative Example Covering Tool 1 by depositing and forming a TiZrN layer or TiZrHfN layer, which is a physical layer, to manufacture a Comparative Example covering tool 9, or by forming a TiZrN layer or a TiZrHfN layer by vapor deposition and then forming an upper layer by vapor deposition. ~ 8 and 10 were manufactured respectively.
The intermediate layer 1, the intermediate layer 2, and the upper layer were formed by forming a film under the conditions shown in Table 3.
Comparative Example With respect to the covering tool 8, periodic supply was not performed when the composite nitride layer was formed. Further, for the comparative example covering tool 9, a magnetron sputtering apparatus was used when forming the composite nitride layer.

Next, the tilt angle number distribution of the crystal grains constituting the composite nitride layer of the hard coating layer of the covering tools 1 to 15 of the present invention and the comparative examples covering tools 1 to 10 was examined with a field emission scanning electron microscope and electron backscattering. It was measured using a diffractometer.
That is, the measurement range (0.3 μm ×) of the cross-sectional polished surface of 0.3 μm in the layer thickness direction of the composite nitride layer from the interface between the lower layer and the composite nitride layer and 50 μm in the direction parallel to the tool substrate surface. 50 μm) is set in the lens barrel of an electric field emission type scanning electron microscope, and an electron beam having an acceleration voltage of 15 kV at an incident angle of 70 degrees is measured on the polished surface with an irradiation current of 1 nA. By irradiating each crystal grain having a rock salt type cubic crystal lattice existing in the range, a measurement area of 0.3 μm × 50 μm is 0.1 μm using an electric field emission type scanning electron microscope and an electron backscattering diffraction image device. At intervals of / step, the inclination angle formed by the normal of the {112} surface, which is the crystal surface of the crystal grains, is 0.25 degrees over the range of 0 to 45 degrees with respect to the normal of the surface-polished surface. The tilt angle classification is within the range of 0 to 10 degrees based on the measurement results, which is represented by a tilt angle number distribution graph that is obtained by dividing the measurement for each pitch and summing up the degrees existing in each classification. The total frequency of a certain crystal grain is obtained, and the ratio of the frequency to the entire tilt angle distribution graph is obtained, which are shown in Tables 5 and 6.

Further, the vertical cross section of the composite nitride layer of the hard coating layer of the covering tools 1 to 15 and the comparative examples covering tools 1 to 10 of the present invention is parallel to the tool substrate at a magnification of 5000 using a scanning electron microscope (SEM). The maximum particle width W and the maximum particle length L are measured for each of the composite nitride crystal grains existing in the region having a height of 10 μm in the direction perpendicular to the tool substrate and the height of the composite nitride layer. At the same time, the value of the aspect ratio L / W was obtained, and the area ratio of the crystal grains having the aspect ratio L / W of 2 or more to the vertical cross section of the composite nitride layer was obtained and shown in Tables 5 and 6.

Further, the thickness of each constituent layer of the hard coating layer of the covering tools 1 to 15 of the present invention and the comparative example covering tools 1 to 10 was measured in a vertical cross section using a scanning electron microscope (SEM), and the average of five points was measured. When calculated from the values, all showed substantially the same average layer thickness as the target layer thickness.

Next, with respect to the coated tools 1 to 15 of the present invention and the coated tools 1 to 10 of the comparative example, with respect to the heat-resistant steel shown below, in a state where the various covering tools are clamped to the tip of the tool steel cutting tool with a fixing jig. A (high-speed) high-feed cutting test was carried out, the flank wear width of the cutting edge was measured, and the presence or absence of welding was observed, and the results are shown in Table 7.

≪Cutting condition A≫
Cutting test: Heat-resistant steel wet continuous high feed cutting test Work material: JIS / SCH13 round bar Cutting speed: 125 m / min,
Notch: 2.0 mm,
Feed: 0.60 mm / rev.
Cutting time: 6 minutes

≪Cutting condition B≫
Cutting test: Heat-resistant steel 1 slit material Wet intermittent high feed cutting processing test Work material: JIS / SCH13 round bar
Cutting speed: 100m / min,
Notch: 1.3 mm,
Feed: 0.50 mm / blade,
Cutting time: 2 minutes

As is clear from the cutting test results in Table 7, the covering tool of the present invention is composed of a TiZrN composite nitride or a TiZrHfN composite nitride having a desired composition and a vertically elongated crystal structure shown in Table 5, and the composite nitride is a composite nitride. In the tilt angle number distribution graph obtained by measuring and totaling the tilt angle formed by the normal of the {112} plane of the crystal grain, the highest peak exists in the predetermined tilt angle division and the frequency in the predetermined tilt angle division. By including a composite nitride layer as a hard coating layer in which the ratio of the above meets the desired range, peeling and chipping do not occur in high feed cutting of heat-resistant steel, the maximum wear width of the flank is small, and excellent welding resistance is achieved. Demonstrates properties, plastic deformation resistance, and abnormal damage resistance.
In the tool of the present invention, those added with a chlorine content of 0.030 at% or less had excellent characteristics with a small flank maximum wear width.
On the other hand, in the comparative example covering tool, the inclination angle formed by the normal of the {112} plane of the crystal grain of the composite nitride, in which the composite nitride of the hard coating layer does not satisfy the desired composition, is measured and totaled. In the tilt angle number distribution graph, the vertical crystal grains having a predetermined aspect ratio, in which the maximum peak does not exist in the predetermined tilt angle division, the ratio of the degrees in the predetermined tilt angle division does not satisfy the desired range, It does not have the desired characteristics because the area ratio does not meet the desired value, and it reaches the end of its life in a short time due to the progress of wear, the occurrence of welding, the occurrence of chipping, etc. rice field.

As described above, the coated tool according to the present invention exhibits excellent welding resistance, plastic deformation resistance, and abnormal damage resistance even under the severe conditions of high feed cutting of heat-resistant steel. We are fully satisfied with the high performance of the cutting equipment, labor saving and energy saving of the cutting process, and cost reduction.

Claims (2)

In a surface-coated cutting tool in which a hard coating layer is formed on the surface of a tool substrate made of WC-based cemented carbide or TiCN-based cermet.
(A) The hard coating layer has at least a lower layer and a composite nitride layer from the surface side of the tool substrate.
(B) The lower layer has at least one compound layer containing Ti or Zr and containing carbon and nitrogen, and the total average film thickness thereof is 1.0 μm or more.
(C) The composite nitride layer includes a composite nitride layer of Ti and Zr having an average thickness of 0.5 to 20 μm or a composite nitride layer of Ti, Zr and Hf.
(D) When the average composition of the composite nitride layer is represented by the composition formula (Ti _(1-x) Zr _xy Hf _{x (1-y)} ) N,
The content ratio x of the total amount of Zr and Hf in the total amount of Ti, Zr and Hf, and the content ratio y of the total amount of Zr and Zr and Hf (however, x and y are both atomic ratios). ) Are composite nitride layers satisfying 0.05 ≦ x ≦ 0.95 and 0 <y ≦ 1.0, respectively.
(E) In the composite nitride layer, an electric field emission type scanning electron microscope and an electron beam backscattering diffractometer are used to form individual crystal grains having a rock salt type cubic crystal lattice existing within the measurement range of the cross-sectional polished surface. By irradiating with an electron beam, the inclination angle formed by the normal of the {112} plane, which is the crystal plane of the crystal grain, is measured within the range of 0 to 45 degrees with respect to the normal of the surface of the tool substrate. When the tilt angle is divided into pitches of 0.25 degrees and the tilt angle distribution graph is created by summing up the degrees existing in each division, the tilt angle with respect to the normal of the surface of the tool substrate is 0. The highest peak exists in the tilt angle division within the range of 10 degrees, and the total number of degrees existing in the tilt angle division within the range of 0 to 10 degrees is 35% or more of the total frequency in the tilt angle distribution graph. Occupy,
(F) The surface-coated cutting tool, wherein the composite nitride layer has an area ratio of 50% or more occupied by vertically elongated crystal grains having an aspect ratio of 2 or more in a vertical cross section. The surface-coated cutting tool according to claim 1, wherein the composite nitride layer contains 0.030 atomic% or less of chlorine.

Images