JP6519795B2 - Surface coated cutting tool with excellent chipping resistance and wear resistance - Google Patents

Description

  The present invention relates to a surface-coated cutting tool having excellent hard coating layer and excellent chipping resistance and wear resistance, and more particularly to a chipping even when subjected to high-speed cutting of carbon steel, alloy steel, cast iron, etc. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent wear resistance over a long period of time without causing abnormal damage such as chipping or peeling.

Generally, coated tools are used for inserts that are detachably attached to the tip of a cutting tool for turning and planing various materials such as steel and cast iron, and drilling and cutting of materials There are drills and miniature drills, solid type end mills used for facing, grooving and shouldering of work materials, etc. Inserts are detachably attached and cutting is performed in the same way as solid type end mills Insert type end mills and the like are known.
Conventionally, as a coated tool, for example, a coated tool in which a WC-based cemented carbide, a TiCN-based cermet, and a cBN sintered body are used as a tool substrate and a hard coating layer is formed thereon is known. Various proposals have been made for the purpose.

For example, Patent Document 1, at _{least, (Ti y Al x Me 1} -x-y) of N hard coating layer component composition (although, Me is, Zr, Hf, V, Nb , Ta, Cr, Mo , W, Si and coated tool having 0.55 ≦ x ≦ 0.80, 0.50 ≦ x / (x + y) ≦ 0.85, 0.7 ≦ x + y ≦ 1.0) in, argon or nitrogen atmosphere, by maintaining 5-240 minutes at a temperature of _{800~1100 ℃, (Ti y Al x} Me 1-x-y) causing spinodal decomposition of N, cubic TiN, It has been proposed to improve the wear resistance of the hard covering layer by forming cubic AlN and hexagonal AlN to achieve the precipitation effect.

  Further, in Patent Document 2, ten or more TiN layers and AlN layers with a layer thickness of 0.04 to 0.2 μm are alternately laminated on the surface of a base material made of a cutting tool or a wear resistant tool, and the total layer thickness is 0.5. A surface-coated carbide member for cutting and abrasive tools provided with a coating layer of 8 to 8 μm has been proposed. In this surface-coated carbide member for cutting and abrasive tools, TiN increases the hardness of the coating layer and the base material In order to improve the adhesion of aluminum, while improving the fracture resistance of the coating layer and to make the crystal grains of TiN finer, AlN has excellent wear resistance, welding resistance and fracture resistance as a whole. It is supposed that a covering layer is formed.

U.S. Pat. No. 7,056,602 Patent No. 2861113

  The coated tool provided with the hard coating layer proposed in Patent Document 1 can be expected to have excellent wear resistance because it has high hardness, but cutting with a high load acting on the cutting edge like high-speed cutting Although the chipping resistance is not sufficient under the conditions and the coated tool proposed in Patent Document 2 is excellent in the balance between the chipping resistance and the wear resistance, the resistance to the hard coating layer is high in high-speed cutting. Peelability is not sufficient, and as a result, a coated tool having both chipping resistance and wear resistance in high-speed cutting is required.

  Then, when the present inventors earnestly examined about the structure of a hard coating layer in order to solve the said subject, the following knowledge was acquired.

A coating obtained by depositing a hard coating layer composed of a composite nitride of Ti and Al (hereinafter sometimes referred to as "TiAlN") on the surface of a tool base using, for example, an arc ion plating apparatus By applying heat treatment (temperature, time, cooling conditions) to the tool under specific conditions, vertically elongated Al nitrides (hereinafter referred to as “AlN”) are shown in the grain boundaries of the crystal grains of the columnar structure constituting the hard coating layer. It has been found that it is possible to form a layer and a Ti-nitride (hereinafter referred to as "TiN") layer having an oblong shape.
And since the longitudinally-shaped AlN layer is excellent in thermal stability and high in thermal conductivity, heat release of the hard coating layer can be effectively performed, and as a result, the hard coating layer in high-speed cutting can be obtained. It has been found that heat resistance and wear resistance can be improved, and since the longitudinally-long TiN layer has excellent toughness and adhesion resistance, it can improve the chipping resistance of the hard coating layer.

In the heat treatment under the specific conditions, after the TiAlN layer is deposited on the surface of the tool substrate, the heat treatment is performed at a temperature of 800 to 1000 ° C. for 30 to 60 minutes and then cooled at a slow rate of 10 ° C./min or less. The heat treatment forms vertically elongated AlN layers and TiN layers at grain boundaries of crystal grains of the TiAlN layer having a columnar structure. In other words, it can be said that the longitudinally elongated AlN layer and TiN layer are formed so as to surround the columnar structure of TiAlN.
In particular, when the cooling rate is faster than 10 ° C./min, sufficient spinodal decomposition does not occur, so that the longitudinally elongated AlN layer and the longitudinally elongated TiN layer can not be formed at the grain boundaries of the grain structure of the columnar structure. Thus, in the heat treatment of the hard covering layer, in particular, it is important to control the cooling rate.

The present invention has been made based on the above findings.
"The surface on which the hard covering layer having at least an average layer thickness of 0.5 to 10 μm of composite nitride layer of Ti and Al is vapor-deposited on the surface of the tool base consisting of either WC base cemented carbide and TiCN base cermet. In coated cutting tools,
The composite nitride layer of Ti and Al,
When represented by a composition formula: (Ti _1−x Al _x ) N, it has an average composition satisfying 0.35 ≦ x ≦ 0.80 (where x is an atomic ratio),
The composite nitride layer of Ti and Al has a columnar structure, and the average value of the widths of the crystal grains in the direction parallel to the surface of the tool base of the crystal grains constituting the columnar structure is W, and When the average value of the length of the crystal grain in the direction perpendicular to the tool substrate surface is L, the value L / W of the ratio of L to W is 1.4 or more,
A vertically long Ti nitride layer and a vertically long Al nitride layer are formed on at least a part of the grain boundaries of the crystal grains constituting the columnar structure, and the Ti nitride layer and the Al nitride layer A surface-coated cutting tool characterized in that each of the longitudinally elongated shapes has a length of 100 nm or more . "
It is characterized by

  Here, the coated tool of the present invention will be described in more detail.

FIG. 1 (a) shows an example of a longitudinal sectional structure photograph (TEM image) of the hard coating layer (TiAlN layer) of the coated tool of the present invention, and FIG. 1 (b) shows the structural photograph of the longitudinal section (TEM image) An example of an EDS mapping image of Al element and Ti element measured for a part of the part (the part encircled by an arrow in the figure) is shown, and FIG. 2 shows a longitudinal cross section of FIG. The schematic diagram of a structure | tissue photograph (TEM image) is shown.
As shown in FIGS. 1 (a), (b) and FIG. 2, the TiAlN layer of the present invention has a columnar structure, and along at least a part of the grain boundaries of the crystal grains constituting the columnar structure. A vertically long TiN layer and a vertically long AlN layer are formed.
When the average composition of the TiAlN layer of the present invention is represented by a composition formula: (Ti _1−x Al _x ) N, an average satisfying the condition 0.35 ≦ x ≦ 0.80 (where x is an atomic ratio) It has a composition, and its average layer thickness is 0.5 to 10 μm, and further has a columnar structure as shown in FIGS. 1 (a), (b) and FIG.
In the composition formula of the TiAlN layer of the present invention, high hardness can not only be obtained if the value of x (where the atomic ratio) represents the average content ratio of Al to the total content of Ti and Al is less than 0.35. When the average content ratio x of Al with respect to the total content of Ti and Al exceeds 0.80, the crystal structure of a part of the structure changes from a rock salt type crystal structure to a hexagonal crystal structure and hard Because of the decrease in the amount, the average content ratio x of Al in the total amount of Ti and Al was determined as 0.35 ≦ x ≦ 0.80. A more preferable range is 0.45 ≦ x ≦ 0.70.
If the average layer thickness of the TiAlN layer is less than 0.5 μm, the excellent wear resistance obtained over long-term use can not be exhibited, while if the average layer thickness exceeds 10 μm, crystals The average layer thickness of the TiAlN layer of the present invention was determined to be 0.5 to 10 μm because grains tend to be coarsened and the chipping resistance improvement effect can not be obtained.
The average composition and the average layer thickness of the TiAlN layer of the present invention are, for example, scanning electron microscopy (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (Energy) It can be determined by cross-sectional measurement using dispersive X-ray spectroscopy (EDS).

  The hard covering layer of the present invention can be constituted only by the TiAlN layer, but other layers are formed as a lower layer or an upper layer of the TiAlN layer to further improve the chipping resistance and the abrasion resistance. Does not interfere with Examples of such a layer include a TiN layer, a CrN layer, a TiCN layer, a TiSiN layer, an AlCrN layer, a TiAlSiN layer, and the like.

The TiAlN layer of the present invention may be formed into a columnar structure of the layer by depositing under specific conditions using an arc ion plating (hereinafter referred to as "AIP") apparatus which is a type of PVD. it can.
When the longitudinal section of the TiAlN layer is observed, the average width of crystal grains constituting the TiAlN layer (average value of the width of crystal grains in the direction parallel to the tool substrate surface) is W, and the average length of crystal grains When L is an average value of lengths of crystal grains in a direction perpendicular to the tool substrate surface, the ratio L / W of L to W, that is, the average aspect ratio should be L / W> 1. Although desirable, it is preferable to set the average aspect ratio L / W to 1.4 or more in order to impart better wear resistance to the TiAlN layer.
As conditions for forming a columnar structure having an average aspect of more than 1 or, preferably, a columnar structure having an average aspect of 1.4 or more, for example,
Reaction pressure: 3.0 Pa
Internal temperature: 500 ° C
DC bias voltage applied to tool base: 70 V
Arc current: 100A
The following AIP conditions can be mentioned.

In the present invention, after forming a TiAlN layer having a columnar structure with an AIP apparatus, spinodal decomposition is caused by heat treatment including cooling at a predetermined heating temperature, heating holding time, and a predetermined speed in a predetermined atmosphere. The longitudinally elongated TiN layer and the longitudinally elongated AlN layer shown in FIGS. 1 (a), (b) and FIG. 2 can be formed on at least a part of the grain boundary of the crystal grain of the columnar structure.
The heat treatment conditions (heating holding condition, cooling condition) after forming the TiAlN layer are, for example, as follows.
Heat treatment atmosphere: vacuum of 1.0 Pa or less
Heating temperature: 800 to 1000 ° C.
Heating and holding time: 30 to 60 minutes,
Cooling rate after heating and holding: 10 ° C / min or less,
In the above heat treatment, the atmosphere is vacuum or an inert gas atmosphere such as Ar for the suppression of oxidation of the film and promotion of spinodal decomposition and promotion of crystal nucleation of the longitudinal structure, and the heating temperature and the heating holding time are the above. It was a predetermined range.
In cooling after heating and holding, the cooling rate is set to 10 ° C./min or less because spinodal decomposition does not occur when the cooling rate is too fast and exceeds 10 ° C./min. The reason is that the longitudinally elongated TiN layer and the longitudinally elongated AlN layer can not be formed at the grain boundaries of the crystal grains of the TiAlN layer consisting of a structure.

In the TiAlN layer of the present invention, the longitudinally-long TiN layer formed on at least a part of the grain boundary of the crystal grain of the columnar structure is excellent in toughness and also excellent in welding resistance, thereby improving the toughness of the TiAlN layer While suppressing the occurrence of chipping due to welding, as a result, the chipping resistance of the TiAlN layer is improved.
In addition, the longitudinally elongated AlN layer is excellent in thermal stability and high in thermal conductivity, and in particular, since it has a longitudinally elongated shape, heat can be effectively released from the hard coating layer, resulting in high-speed cutting The heat resistance and abrasion resistance of the hard coating layer in processing can be improved.
And, in the TiAlN layer of the present invention, the presence of the longitudinally elongated TiN layer and the longitudinally elongated AlN layer in at least a part of the grain boundaries of the crystal grain of the columnar structure makes the chipping resistance in high speed cutting. It is possible to combine wear resistance.
As shown in Patent Document 2, there is also a coated tool in which a hard coating layer having an alternate lamination structure in which a TiN layer and an AlN layer are alternately stacked in the layer thickness direction is vapor deposited. As described above, there has been a problem that delamination is likely to occur in high-speed cutting.
However, in the coated tool of the present invention in which the longitudinally elongated TiN layer and the longitudinally elongated AlN layer are formed on at least a part of the grain boundaries of the columnar grain, delamination does not occur and is excellent over long-term use. Chipping resistance and abrasion resistance are exhibited.

Distinguish between a longitudinally elongated TiN layer and a longitudinally elongated AlN layer present in at least a part of the grain boundaries of the crystal grain of the TiAlN layer of the columnar structure of the present invention, the composition, length (a longitudinally elongated TiN layer or a longitudinally elongated shape The length (nm) of the AlN layer is a scanning electron microscope (SEM), an electron backscattering diffraction (EBSD), a transmission electron microscope (TEM), an energy dispersive electron microscope, for the longitudinal section of the TiAlN layer. It can be determined by observation and measurement using type X-ray spectroscopy (EDS).
Whether AlN and TiN were present along the grain boundaries of the columnar structure was identified using an EDS mapping method as shown in FIG. 1 (b). From the results of EDS mapping measurement, point analysis of the layer was performed to identify the composition, and shape measurement of the TiN layer and the AlN layer was performed. At this time, the length of the longitudinally elongated shape is preferably 100 nm or more, but in order to further provide welding resistance and high thermal conductivity, the length is preferably 200 nm or more.

In the coated tool of the present invention, at least a TiAlN layer of a predetermined composition having a columnar structure is vapor-deposited as a hard covering layer, and at least a part of the grain boundaries of crystal grains of the columnar structure is a longitudinally elongated TiN layer The hard coating layer can combine excellent chipping resistance and excellent wear resistance because the AlN layer having a longitudinally elongated shape is formed.
Therefore, when the coated tool of the present invention is subjected to high-speed cutting of carbon steel, alloy steel, cast iron and the like, excellent wear resistance over long-term use without causing abnormal damage such as chipping, chipping or peeling. To exert

(A) shows an example of the longitudinal cross-section structure | tissue photograph (TEM image) of the TiAlN layer of this invention coated tool, (b) shows the one part (arrow in the figure) of this longitudinal cross-section structure | tissue photograph (TEM image) An example of the EDS mapping image of Al element and Ti element measured about the circled part shown by (1) is shown. The schematic diagram of the longitudinal cross-section structure | tissue photograph (TEM image) of Fig.1 (a) is shown. It is the schematic of the AIP apparatus for forming the TiAlN layer of this invention coating tool, (a) is a front view, (b) shows a side view.

Below, an Example demonstrates the coating tool of this invention concretely.
In addition, although a coated tool which uses WC base cemented carbide as a tool base is explained as a concrete explanation, the same may be said of a coated tool which uses TiCN base cermet as a tool base.

Tool substrate preparation:
Prepare Co powder, VC powder, Cr ₃ C ₂ powder, TiC powder, TaC powder, NbC powder, WC powder as raw material powder, mix these raw material powders with the composition shown in Table 1, and add wax In addition, after wet mixing in a ball mill for 72 hours, drying under reduced pressure, press forming at a pressure of 100 MPa, sintering these green compacts and processing to a predetermined size, insert shape of ISO standard SEEN 1203 AFTN 1 The tool substrates 1 to 3 made of WC-based cemented carbide having the

Formation of hard coating layer:
A hard coating layer was formed on the tool substrates 1 to 3 using an arc ion plating apparatus shown in FIG.
In addition, as a Ti-Al alloy target of FIG. 2, the Ti-Al alloy target of the composition according to the average composition of the target TiAlN layer was used.
(A) The tool substrates 1 to 3 are ultrasonically cleaned in acetone and mounted in a dry state along the outer peripheral portion at a predetermined distance in the radial direction from the central axis on the rotary table in the AIP apparatus . Moreover, the Ti-Al alloy target of the predetermined composition was arrange | positioned as a cathode electrode (evaporation source).
(B) First, the inside of the apparatus is heated to 500 ° C. with a heater while exhausting the inside of the apparatus and maintaining a vacuum of 10 ⁻² Pa or less, and then an Ar gas atmosphere of 0.5 to 2.0 Pa is set, A DC bias voltage of -200 to -1000 V is applied to the tool base rotating while rotating on the rotary table, thereby bombarding the surface of the tool base with argon ions for 5 to 30 minutes,
(C) Next, nitrogen gas as a reaction gas is introduced into the apparatus to obtain a predetermined reaction atmosphere in the range of 2.0 to 9.0 Pa shown in Table 2 and the temperature in the apparatus shown in Table 2 as well. A predetermined DC bias voltage within a range of -30 to -150 V shown in Table 2 is applied to a tool base rotating while rotating on the rotary table while maintaining the rotation speed, and a cathode electrode made of a Ti-Al alloy target ( A predetermined current in the range of 80 to 240 A shown in Table 2 is applied between the evaporation source) and the anode electrode to generate arc discharge, and the target composition shown in Table 4 on the tool substrate surface, target average layer thickness Manufacture a coated tool on which a hard coating layer consisting of a TiAlN layer is deposited
(D) Next, the coated tool is heat-treated under the conditions shown in Table 3 and cooled similarly under the conditions shown in Table 3 so that the coated tool of the present invention shown in Table 4 (hereinafter referred to as “invention tool”) ) 1 to 7 were prepared.

  For comparison, a TiAlN layer is vapor deposited on the tool substrates 1 to 3 using the AIP apparatus shown in FIG. 2 under the conditions shown in Table 5 and then heat treated under the conditions shown in Table 6 and then Coated tools (hereinafter, referred to as “comparative tool”) 1 to 9 of comparative examples shown in Table 7 were produced without cooling.

The hard coating layer longitudinal cross section perpendicular to the tool substrate surface of the inventive tools 1 to 7 and the comparative example tools 1 to 9 prepared above has a width of 10 μm in the direction parallel to the tool substrate surface, and the thickness of the hard coating layer The composition of the TiAlN layer by cross-sectional measurement using a scanning electron microscope (SEM), a transmission electron microscope (TEM), and energy dispersive X-ray spectroscopy (EDS) for a field of view set so that all the regions are included. The average composition and the average layer thickness were calculated by measuring the layer thickness at a plurality of locations and averaging them.

  In addition, the width and length L of the crystal grain of the TiAlN layer having a columnar structure can be determined by cross-sectional observation using a scanning electron microscope (SEM), an electron backscattering diffraction (EBSD), and a transmission electron microscope (TEM). The average width W and the average length L of the columnar crystal grains were determined and the average aspect ratio L / W was calculated by measuring the crystal grains in the field of view and averaging the measured values.

Further, by cross-sectional observation using a scanning electron microscope (SEM), an electron backscattering diffraction (EBSD), and a transmission electron microscope (TEM), the grain boundaries of the crystal grains of the columnar TiAlN layer are elongated in shape. While checking and discriminating whether or not the TiN layer and the vertically elongated AlN layer are present, the presence length (nm) of the TiN layer and the AlN layer, if present, were measured.
More specifically, it is as follows. The presence of layers along the grain boundaries of the columnar structure of AlN and TiN was identified using EDS mapping, and the average composition was identified by point analysis of the layers at multiple locations. The shape measurement measured the length of multiple places of a TiN layer and an AlN layer from the result of EDS mapping, and computed average length.

  Tables 4 and 7 show the various values obtained above.

Next, high-speed cutting tests were performed on carbon steel, alloy steel, and cast iron under the following conditions for inventive tools 1 to 7 and comparative example tools 1 to 9, respectively.
Cutting condition A:
Work material: round bar of JIS · SCM430 (HB280),
Cutting speed: 200 m / min. ,
Notch: 0.2 mm,
Feeding: 0.27 mm / rev. ,
Cutting time: 5 minutes,
Continuous high-speed high-feed cutting test of alloy steel under the conditions of (normal cutting speed and feed are 155 m / min. And 0.20 mm / rev., Respectively).
Cutting condition B:
Work material: round bar of JIS · S55C (HB250),
Cutting speed: 210 m / min. ,
Notch: 0.2 mm,
Feeding: 0.25 mm / rev. ,
Cutting time: 5 minutes,
Continuous high-speed high-feed cutting test of carbon steel under the conditions of (normal cutting speed and feed are 145 m / min. And 0.25 mm / rev., Respectively).
Cutting condition C:
Work material: Round bar of JIS · SKD 61 (HRC 60),
Cutting speed: 130 m / min. ,
Notch: 0.2 mm,
Feeding: 0.2 mm / rev. ,
Cutting time: 3 minutes,
Continuous high-speed cutting processing test of high hardness steel under the conditions of (normal cutting speed and feed are respectively 70 m / min., 0.1 mm / rev.).
The results are shown in Table 8, Table 9, and Table 10.

According to the results of Tables 8 to 10, no abnormal damage such as chipping or peeling occurs in any of the cutting conditions according to the present invention tools 1 to 7 , and the average of the flank wear width is the cutting condition A It is about 0.2 mm, about 0.23 mm in cutting condition B, and about 0.26 mm in cutting condition C, and it is understood that both chipping resistance and abrasion resistance are excellent.
On the other hand, it is clear that the comparative example tools 1 to 9 reach the life in a short time by the occurrence of chipping or the progress of flank wear under any of the cutting conditions A to C.

The surface-coated cutting tool according to the present invention includes carbon steel, alloy steel, which is accompanied by generation of particularly high heat and which exerts a large load on the cutting edge, as well as cutting under normal cutting conditions of various steels and the like. It exhibits excellent chipping resistance and wear resistance in high-speed cutting of cast iron etc. and exhibits excellent cutting performance over a long period of time, thus improving the performance of cutting equipment and saving labor in cutting And energy saving as well as cost reduction.

Claims (1)

Surface coating formed by vapor deposition of a hard coating layer having a composite nitride layer of Ti and Al with an average layer thickness of 0.5 to 10 μm on the surface of a tool substrate consisting of either WC base cemented carbide or TiCN base cermet In cutting tools,
The composite nitride layer of Ti and Al,
When represented by a composition formula: (Ti _1−x Al _x ) N, it has an average composition satisfying 0.35 ≦ x ≦ 0.80 (where x is an atomic ratio),
The composite nitride layer of Ti and Al has a columnar structure,
The average value of the width of the crystal grain in the direction parallel to the tool substrate surface of the crystal grain constituting the columnar structure is W, and the average value of the length of the crystal grain in the direction perpendicular to the tool substrate surface Where L is the ratio of L to W, L / W is 1.4 or more,
A vertically long Ti nitride layer and a vertically long Al nitride layer are formed on at least a part of the grain boundaries of the crystal grains constituting the columnar structure , and the Ti nitride layer and the Al nitride layer A surface-coated cutting tool characterized in that each of the longitudinally elongated shapes has a length of 100 nm or more .