JP4235904B2 - Surface-coated cutting tool with excellent wear resistance with a hard coating layer in high-speed cutting - Google Patents

Description

The present invention relates to a surface-coated cutting tool that exhibits excellent wear resistance with a hard coating layer, particularly in high-speed cutting of various types of steel and cast iron.

Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. ,
(A) Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer, oxide (hereinafter referred to as TiO) layer, Ti compound layer composed of one or more of a carbon oxide (hereinafter referred to as TiCO) layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer and having an overall average layer thickness of 3 to 20 μm ,
(B) having an average layer thickness of 1 to 30 μm and a composition formula: (Al _1-X Cr _X ) ₂ O ₃ (where X is an atomic ratio, X: 0.20 to 0.45),
A solid solution oxide of Al and Cr satisfying the following conditions (hereinafter referred to as vapor-deposited (Al, Cr) ₂ O ₃ ) layer:
There is known a surface-coated cutting tool formed by chemical vapor deposition of the hard coating layer composed of the above (a) and (b), and this surface-coated cutting tool is used for continuous cutting such as various steels and cast irons. It is well known to be used for interrupted cutting.

In general, the Ti compound layer and the vapor deposition (Al, Cr) ₂ O ₃ layer constituting the hard coating layer of the surface-coated cutting tool have a granular crystal structure, and the TiCN layer constituting the Ti compound layer. In order to improve the strength of the layer itself, it is formed by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. using a mixed gas containing organic carbonitride as a reaction gas in a normal chemical vapor deposition apparatus. It is also known to have a vertically grown crystal structure.
Japanese Patent Publication No.58-53065

In recent years, the performance of cutting machines has been remarkable. On the other hand, there is a strong demand for labor saving, energy saving, and cost reduction for cutting work, and along with this, cutting work tends to be further accelerated. For surface-coated cutting tools , there is no problem when this is used for continuous cutting or intermittent cutting under normal conditions such as steel or cast iron, but especially when this is used for high-speed cutting, a hard coating layer is formed. The deposited (Al, Cr) ₂ O ₃ layer has excellent heat resistance and sufficient high-temperature strength, but because the high-temperature hardness is not sufficient, the wear progress of the hard coating layer accelerates rapidly due to this. As a result, the service life is reached in a relatively short time.

Therefore, the present inventors pay attention to the surface-coated cutting tool in which the above-described vapor deposition (Al, Cr) ₂ O ₃ layer constitutes the hard coating layer from the above viewpoint, and aims to improve the wear resistance thereof. As a result of research,
After forming the Ti compound layer and the vapor deposition (Al, Cr) ₂ O ₃ layer as a hard coating layer on the surface of the tool base, a vacuum atmosphere, a hydrogen atmosphere, or an Ar atmosphere is used. When the heat treatment is performed at 800 ° C. for 1 to 5 hours, the Ti compound layer does not change, but phase separation occurs in the deposited (Al, Cr) ₂ O ₃ layer, compared with Cr. And a solid solution oxide separated phase of Al and Cr with high Al content [hereinafter referred to as a high Al-Cr oxide separated phase], and a solid solution oxide separated phase of Cr and Al with a high Cr content compared to Al A heated two-phase separated oxide layer of Al and Cr (hereinafter referred to as a two-phase separated (Al, Cr) ₂ O ₃ layer) having a two-phase mixed structure composed of a high Cr—Al oxide separated phase]. in phase separation (Al, _Cr) 2 _{O 3} layer, the high Cr Since the Al oxide separated phase has excellent high temperature hardness and heat resistance due to the high Al content, and the high Cr-Al oxide separated phase has excellent high temperature strength due to the high Cr content, Compared to the conventional vapor deposition (Al, Cr) ₂ O ₃ layer, it has excellent high temperature hardness, heat resistance, and high temperature strength, and thus the two-phase separation (Al, Cr) ₂ O ₃ layer. The surface-coated cutting tool formed in the state of coexisting with the Ti compound layer as a hard coating layer is high-speed cutting with severe cutting conditions and does not cause chipping (small chipping) on the cutting edge. Compared to the above-mentioned conventional coated cermet tool As a result, they have obtained research results indicating that they have even better wear resistance.

The present invention was made based on the above research results, and a chemical vapor deposition apparatus was used on the surface of a tool base composed of a WC-based cemented carbide or a TiCN-based cermet.
(A) a Ti compound layer composed of one or more of a TiC layer, a TiN layer, a TiCN layer, a TiO layer, a TiCO layer, and a TiCNO layer, and having an overall average layer thickness of 3 to 20 μm,
(B) the composition _{formula: (Al 1-X Cr X} ) 2 O 3, ( provided that, X is atomic ratio, X: 0.20~0.45),
And an evaporated (Al, Cr) ₂ O ₃ layer having an average layer thickness of 1 to 30 μm,
The surface-coated cutting tool formed by vapor-depositing the hard coating layer composed of (a) and (b) above is set to 1 at a predetermined temperature in the range of 600 to 800 ° C. in a vacuum atmosphere, a hydrogen atmosphere, or an Ar atmosphere. Heat treatment is performed under the condition of holding for a predetermined time within a range of ˜5 hours, and the above-described vapor-deposited (Al, Cr) ₂ O ₃ layer is divided into a high Al—Cr oxide separation phase and a high Cr—Al oxide separation phase. It is characterized by a surface-coated cutting tool that exhibits high wear resistance in which a hard coating layer is excellent in high-speed cutting, which is a two-phase separation (Al, Cr) ₂ O ₃ layer having a two-phase mixed structure consisting of

The reason why the constituent layers of the hard coating layer of the surface-coated cutting tool of the present invention are numerically limited as described above will be described below.
(A) X value of vapor-deposited (Al, Cr) ₂ O ₃ layer When the X value is less than 0.20 in atomic ratio (the same shall apply hereinafter), the ratio of the high Cr—Al oxide separated phase after heat treatment is high Al—Cr. Compared to the oxide separation phase, it becomes too small, and the desired high-temperature strength cannot be secured in the two-phase separation (Al, Cr) ₂ O ₃ layer, and chipping tends to occur on the cutting edge, while X If the value exceeds 0.45, on the contrary, the ratio of the high Al-Cr oxide separated phase after the heat treatment becomes low, and a rapid decrease tendency appears in high temperature hardness and heat resistance. Was determined to be 0.20 to 0.45.

(B) Overall average layer thickness of the Ti compound layer The Ti compound layer basically exists as a lower layer of the two-phase separation (Al, Cr) ₂ O ₃ layer, and has a hard coating layer due to its excellent strength. In addition to providing strength, the tool base and the two-phase-separated (Al, Cr) ₂ O ₃ layer are firmly adhered to each other, and thus have an effect of improving the adhesion of the hard coating layer to the tool base. If the total average layer thickness is less than 3 μm, the above-mentioned effect cannot be fully exerted. On the other hand, if the total average layer thickness exceeds 20 μm, it is easy to cause thermoplastic deformation especially in high-speed cutting with high heat generation. Since this causes uneven wear, the overall average layer thickness was determined to be 3 to 20 μm.

(C) 2-phase separation (Al, _Cr) 2 average layer thickness 2 phase separation of _{O 3} layer (Al, _Cr) in 2 _{O 3} layer has a good hot hardness provided by a high Al-Cr oxide isolation phase The heat resistance and excellent high-temperature strength due to the high Cr-Al oxide separation phase have the effect of improving the wear resistance of the hard coating layer without chipping at the cutting edge even at high-speed cutting. However, if the average layer thickness exceeds 30 μm, chipping is likely to occur. Therefore, the average layer thickness is 1-30 μm. Determined.

The surface-coated cutting tool of the present invention has excellent high-temperature hardness and heat resistance in which the two-phase separation (Al, Cr) ₂ O ₃ layer constituting the hard coating layer is excellent even in high-speed cutting of various types of steel and cast iron with high heat generation. In addition, since it has excellent high-temperature strength, it exhibits excellent wear resistance without occurrence of chipping on the cutting edge.

Next, the surface-coated cutting tool of the present invention will be specifically described with reference to examples.
WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder all having an average particle diameter of 1 to 3 μm are prepared as raw material powders. These raw material powders were blended into the composition shown in Table 1, added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and pressed into a green compact with a predetermined shape at a pressure of 98 MPa. The green compact was vacuum sintered at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa. After sintering, the cutting edge portion was R: 0.07 mm honing By performing the processing, tool bases A to F made of a WC-base cemented carbide having a throwaway tip shape specified in ISO · CNMG120408 were manufactured.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after the sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. Tool bases a to f made of TiCN-based cermet having a standard / CNMG12041 chip shape were formed.

Next, a normal chemical vapor deposition apparatus was used on the surfaces of these tool bases A to F and tool bases a to f. First, Table 3 (l-TiCN in Table 3 is described in JP-A-6-8010). The TiCN layer and the vapor deposition (Al, etc.) under the conditions shown in the conditions shown in the above are the conditions for forming a TiCN layer having a vertically grown crystal structure. Conventional surface-coated cutting tools 1 to 13 were produced by vapor-depositing hard coating layers composed of Cr) ₂ O ₃ layers in the combinations shown in Table 4 and with the target layer thicknesses also shown in Table 4.

Next, each of the conventional surface-coated cutting tools 1 to 13 obtained as a result was subjected to a heat treatment under the conditions shown in Table 5 to phase-separate the deposited (Al, Cr) ₂ O ₃ layer, and to obtain a high Al Each of the surface-coated cutting tools 1 to 13 of the present invention is formed as a two-phase separated (Al, Cr) ₂ O ₃ layer having a two-phase mixed structure composed of a Cr oxide separated phase and a high Cr—Al oxide separated phase. Manufactured.

About the constituent layer of the hard coating layer of the above-mentioned surface coating cutting tool 1-13 of the present invention and the conventional surface coating cutting tool 1-13, when the thickness was measured using a scanning electron microscope (longitudinal section measurement), All showed the average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness.
Further, the two-phase separation (Al, Cr) ₂ O ₃ layer of the hard coating layer of the above-mentioned surface-coated cutting tools 1 to 13 of the present invention and the vapor deposition (Al, Cr) ₂ O of that of the conventional surface-coated cutting tools 1 to 13 _{When the three-} layer structure was observed with a high-resolution electron microscope using a post-column type energy filter, each of the two-phase separated (Al, Cr) ₂ O ₃ layers was a high Al-Cr oxide separated phase. A two-phase mixed structure composed of a high Cr—Al oxide separated phase was shown, and the vapor-deposited (Al, Cr) ₂ O ₃ layer showed a single-phase structure composed of a solid solution.

Next, the surface coating cutting tools 1 to 13 and the conventional surface coating cutting tools 1 to 13 of the present invention and the conventional surface coating cutting tools 1 to 13 are mounted in a state where each of the various surface coating cutting tools is screwed to the tip of the tool steel tool with a fixing jig. For 13,
Work material: JIS · SCM440 lengthwise equidistant 4 vertical grooved round bar,
Cutting speed: 300 m / min,
Incision: 1.5mm,
Feed: 0.15mm / rev,
Cutting time: 10 minutes,
Dry high-speed intermittent cutting test of alloy steel under the conditions of (normal cutting speed is 150 m / min),
Work material: JIS / S45C round bar,
Cutting speed: 400 m / min,
Incision: 1.5mm,
Feed: 0.2mm / rev,
Cutting time: 10 minutes,
Dry high-speed continuous cutting test of carbon steel under the conditions (normal cutting speed is 180 m / min),
Work material: JIS / FC300 round bar,
Cutting speed: 450 m / min,
Incision: 1.5mm,
Feed: 0.3mm / rev,
Cutting time: 10 minutes,
The dry high-speed continuous cutting test (normal cutting speed is 250 m / min) of cast iron under the above conditions was performed, and the flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 6.

From the results shown in Tables 4 to 6, the surface-coated cutting tools 1 to 13 of the present invention have excellent hard coating layers without occurrence of chipping even at high speed cutting of various steels and cast irons with high heat generation. In contrast, the conventional surface-coated cutting tools 1 to 13 show that the wear of the hard coating layer progresses very rapidly, and the service life is reached in a relatively short time.
As described above, the surface-coated cutting tool of the present invention has an excellent hard coating layer not only for continuous cutting and intermittent cutting under normal conditions such as various steels and cast iron, but also for high-speed cutting with high heat generation. High wear resistance and excellent cutting performance over a long period of time, so that it can sufficiently satisfy the high performance of cutting equipment, labor saving and energy saving of cutting, and cost reduction It is.

Claims (1)

A chemical vapor deposition device is used on the surface of the tool base made of tungsten carbide base cemented carbide or titanium carbonitride base cermet,
(A) Ti carbide layer, nitride layer, carbonitride layer, oxide, carbonate layer, and one or more layers of carbonitride oxide layer, and an overall average layer of 3 to 20 μm A Ti compound layer having a thickness;
(B) the composition _{formula: (Al 1-X Cr X} ) 2 O 3, ( provided that an atomic ratio, X: 0.20 to 0.45),
And an evaporated solid solution oxide layer of Al and Cr having an average layer thickness of 1 to 30 μm,
The surface-coated cutting tool formed by vapor-depositing the hard coating layer composed of (a) and (b) above is set to 1 at a predetermined temperature in the range of 600 to 800 ° C. in a vacuum atmosphere, a hydrogen atmosphere, or an Ar atmosphere. A heat treatment is performed under the condition of holding for a predetermined time within a range of ˜5 hours, and the above-described vapor-deposited solid solution oxide layer of Al and Cr is separated into a solid solution oxide phase of Al and Cr containing a higher Al content than Cr. And a heated two-phase separated oxide layer of Al and Cr having a two-phase mixed structure consisting of a solid solution oxide separated phase of Cr and Al with a high Cr content compared to Al.
A surface-coated cutting tool that exhibits excellent wear resistance with a hard coating layer in high-speed cutting.