JP4747387B2 - Surface-coated cermet cutting tool with excellent chipping resistance thanks to thick α-type aluminum oxide layer - Google Patents

Description

In the present invention, an upper layer of a hard coating layer, that is, an aluminum oxide layer (hereinafter referred to as an α-type Al ₂ O ₃ layer) having an α-type crystal structure in a state where chemical vapor deposition is formed is particularly thick. The present invention relates to a surface-coated cermet cutting tool (hereinafter referred to as a coated cermet tool) that exhibits excellent chipping resistance even when used for cutting various steels 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) As a lower layer, a Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer formed by chemical vapor deposition, Ti 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 0.5 to 10 μm Compound layer,
(B) an α-type Al ₂ O ₃ layer having an average layer thickness of 1 to 15 μm as an upper layer;
There is known a coated cermet tool formed by vapor-depositing a hard coating layer composed of the above (a) and (b). It is well known to be used.

In general, the Ti compound layer and the α-type Al ₂ O ₃ layer constituting the hard coating layer of the above-mentioned coated cermet tool have a granular crystal structure, and further, the TiCN layer constituting the Ti compound layer is the layer itself. For the purpose of improving the strength of the crystal, a vertically grown crystal formed by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. using a mixed gas containing an organic carbonitride as a reaction gas in a normal chemical vapor deposition apparatus. It is also known to have an organization.
Japanese Unexamined Patent Publication No. 6-31503 Japanese Patent Laid-Open No. 6-8010

In recent years, the use of FA for cutting devices has been remarkable. On the other hand, there has been a strong demand for labor saving and energy saving and further cost reduction for cutting work, and with this purpose, especially for the purpose of further extending the service life of cutting tools. upper layer constituting the hard coating layer, i.e. excellent but the hot hardness and thickening of one step in the α-type the Al ₂ O ₃ layer having heat resistance is strongly demanded, of the α-type the Al ₂ O ₃ layer When the layer thickness exceeds 15 μm, which is the maximum average layer thickness that has been practically used in the past, the Al ₂ O ₃ crystal grains become coarser and the denseness of the layer itself is significantly reduced. since the decrease in the high-temperature strength can not be avoided, the coated cermet tool formed by depositing formed as an upper layer of such thickening α type the Al ₂ O ₃ layer a hard coating layer, the thickening α-type Al ₂ O ₃ layer due to chipping to the cutting edge (fine Chipping) is likely to occur, since it becomes very short for this result useful life, it can not be put to practical use at present.

Therefore, the present inventors focused on the α-type Al ₂ O ₃ layer having an average layer thickness of 1 to 15 μm constituting the hard coating layer of the above-described conventional coated cermet tool from the above viewpoint, Research was conducted to develop a coated cermet tool in which chipping caused by the thickened α-type Al ₂ O ₃ layer does not occur at the cutting edge even if the layer thickness is increased to an average layer thickness exceeding 15 μm. result,
(A) The α-type Al ₂ O ₃ layer, which is the upper layer of the hard coating layer of the above-described conventional coated cermet tool, is generally used in a normal chemical vapor deposition apparatus.
Reaction gas composition: by _{volume%, AlCl 3: 1~5%,} CO 2: 3~7%, HCl: 0.3~3%, H 2 S: 0.02~0.4%, H 2: remainder ,
Reaction atmosphere temperature: 950-1100 ° C.
Reaction atmosphere pressure: 3 to 13 kPa,
The α-type Al ₂ O ₃ layer is formed using the same chemical vapor deposition apparatus.
Reaction gas composition: by _{volume%, AlCl 3: 1~5%,} CO 2: 3~7%, HCl: 0.3~3%, SF 6: 0.1~1%, H 2: remainder,
Reaction atmosphere temperature: 750 to 900 ° C.
Reaction atmosphere pressure: 55-80 kPa,
When using SF ₆ instead of H ₂ S as the reaction gas under relatively low temperature and high pressure conditions, the layer thickness is increased to an average layer thickness of 15 to 30 μm, exceeding 15 μm. In this case, the thickened α-type Al ₂ O ₃ layer (hereinafter referred to as a thickened modified α-type Al ₂ O ₃ layer) is Al _{2 in} spite of being thickened. Since the coarsening of the O ₃ crystal grains is remarkably suppressed and the denseness of the layer itself is maintained, the decrease in high temperature strength is prevented.

(B) The same conditions as the above-mentioned conditions for forming the thickening-modified α-type Al ₂ O ₃ layer and the α-type Al ₂ O ₃ layer that is the upper layer of the hard coating layer of the conventional coated cermet tool (above-mentioned A field emission scanning electron microscope for a thickened α-type Al ₂ O ₃ layer (hereinafter referred to as a thickened normal α-type Al ₂ O ₃ layer) deposited with an average layer thickness of 16 to 30 μm under normal conditions) As shown in the schematic explanatory diagrams of FIGS. 1A and 1B, an electron beam is individually applied to each α-type Al ₂ O ₃ crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface. Irradiate and use an electron backscatter diffraction image apparatus, and a predetermined area is spaced at a distance of 0.1 μm / step, and the normal line of the (0001) plane which is the crystal plane of the crystal grain with respect to the normal line of the polished surface Is measured, and a measured inclination angle within a range of 45 to 90 degrees out of the measured inclination angles is 0.2. When the slope angle number distribution graph is created by dividing the pitch every 5 degrees and the frequencies existing in each section, the thickened normal α-type Al ₂ O ₃ layer is illustrated in FIG. As shown in the graph, the distribution of measured inclination angles on the (0001) plane shows an unbiased inclination angle number distribution graph within a range of 45 to 90 degrees, whereas the thickening-modified α-type Al ₂ O _{3 is used.} As shown in FIG. 2, the layer has a sharp maximum peak at a specific position of the tilt angle section, and this sharp maximum peak is obtained by changing the reaction atmosphere pressure in the chemical vapor deposition apparatus, and the tilt angle on the horizontal axis of the graph. The position that appears in the section changes.

(C) According to the test results, in the above-mentioned thickened modified α-type Al ₂ O ₃ layer, when the reaction atmosphere pressure is changed within the range of 55 to 80 kPa as described above, the sharp maximum peak is obtained. Appears in the range of 83 to 89 degrees of the inclination angle section, and the total of the frequencies existing in the range of 83 to 90 degrees occupies 45 to 77% of the total degrees in the inclination angle distribution graph. Therefore, the highest peak of the inclination angle section appears in the range of 83 to 89 degrees in the inclination angle number distribution graph, and the frequency ratio existing in the range of 83 to 90 degrees is 45 to 90 degrees. A coated cermet tool formed by vapor deposition in the state of coexisting with the Ti compound layer of the lower layer, with the thickened modified α-type Al ₂ O ₃ layer occupying a proportion of 77% as the upper layer of the hard coating layer, Thickened normal α-type Al ₂ Compared to a coated cermet tool in which an O ₃ layer is deposited as an upper layer of a hard coating layer, it has a particularly superior wear resistance over a long period of time without chipping at the cutting edge.

The present invention has been made based on the above research results, and on the surface of a tool base composed of a WC-based cemented carbide or TiCN-based cermet,
(A) The lower layer is composed of one or more of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer, all of which are formed by chemical vapor deposition, and a whole of 0.5 to 10 μm. A Ti compound layer having an average layer thickness;
(B) As an upper layer, each crystal grain having a hexagonal crystal lattice which has an α-type crystal structure in a state where chemical vapor deposition is formed, and which exists within the measurement range of the surface polished surface using a field emission scanning electron microscope An electron backscattered diffraction image apparatus is used to irradiate the substrate with a predetermined region of the crystal grain with respect to the normal of the surface polished surface at an interval of 0.1 μm / step (0001). The inclination angle formed by the normal of the surface is measured, and among the measurement inclination angles, the measurement inclination angles within the range of 45 to 90 degrees are divided for each pitch of 0.25 degrees and exist in each division. In the inclination angle distribution graph obtained by collecting the frequencies, the highest peak exists in the inclination angle section in the range of 83 to 89 degrees, and the total of the frequencies existing in the range of 83 to 90 degrees is the inclination angle number. of the total power in the distribution graph of 45-77% It shows an inclination angle frequency distribution graph which accounts for engagement, and thickening modified α type with an average layer thickness of 16~30μm Al ₂ O ₃ layer,
The hard coating layer formed by vapor deposition of the hard coating layer composed of (a) and (b) above is characterized by a coated cermet tool that exhibits excellent chipping resistance.

In addition, the reason why the numerical values of the constituent layers of the hard coating layer of the coated cermet tool of the present invention are limited as described above will be described below.
(A) Ti compound layer The Ti compound layer basically exists as a lower layer of the thickening-modified α-type Al ₂ O ₃ layer, and the high temperature strength of the hard coating layer is improved by its excellent high temperature strength. In addition to the tool substrate and the thickened modified α-type Al ₂ O ₃ layer, and thus has an effect of improving the adhesion of the hard coating layer to the tool substrate. If the thickness is less than 0.5 μm, the above-mentioned effect cannot be sufficiently exerted. On the other hand, if the average layer thickness exceeds 10 μm, the amount of thermoplastic deformation caused by heat generated during cutting increases beyond the allowable range. As a result, cracks are likely to occur in the thickened reformed α-type Al ₂ O ₃ layer, which is the upper layer, so the average layer thickness was determined to be 0.5 to 10 μm.

As described above, the highest peak position of the measured tilt angle in the tilt angle number distribution graph of the thickening-modified α-type Al ₂ O ₃ layer changes by changing the reaction atmosphere pressure in the chemical vapor deposition apparatus. According to the test results, when the reaction atmosphere pressure is changed within the range of 55 to 80 kPa, the highest peak appears in the inclination angle section within the range of 83 to 89 degrees and the frequency existing within the range of 83 to 90 degrees. The inclination angle number distribution graph occupies a ratio of 45 to 77% of the entire frequency in the inclination angle number distribution graph. Therefore, even if the reaction atmosphere pressure is less than 55 kPa, it exceeds 80 kPa. also, the measurement highest peak position of the inclination angle deviates from the range of 83 to 89 degrees, it may be to maintain the desired high-temperature strength as a result it becomes difficult It comes to occur .
Moreover, the thickened modified α-type Al ₂ O ₃ layer improves the wear resistance of the hard coating layer by the excellent high-temperature hardness and heat resistance of Al ₂ O ₃ itself, and the thickened normal α-type Al Compared with ₂ O ₃ layer, it has excellent high-temperature strength, so it has the effect of suppressing the occurrence of chipping in the thick hard coating layer. However, if the average layer thickness is less than 16 μm, the film thickness is increased. However, if the average layer thickness exceeds 30 μm, the chipping tends to occur. Therefore, the average layer thickness is determined to be 16 to 30 μm.

  For the purpose of identification before and after the use of the coated cermet tool, a TiN layer having a golden color tone may be vapor-deposited as the outermost surface layer of the hard coating layer, but the average layer thickness in this case 0.1-1 μm may be sufficient, because if the thickness is less than 0.1 μm, a sufficient discrimination effect cannot be obtained, while the discrimination effect by the TiN layer is sufficient with an average layer thickness of up to 1 μm. .

In the coated cermet tool of the present invention, the thickened modified α-type Al ₂ O ₃ layer constituting the hard coating layer has the highest tilt angle within the range of 83 to 89 degrees as illustrated in FIG. An inclination angle distribution graph showing the peak is shown. Even when the average layer thickness is increased to a thickness of 16 to 30 μm, it exhibits excellent chipping resistance, so it is excellent in cutting various steels and cast irons. The wear resistance is demonstrated over a long period of time, and the life of the product can be further extended.

  Next, the coated cermet tool of the present invention will be specifically described with reference to examples.

As raw material powders, WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, and Co powder each having an average particle diameter of 1 to 3 μm are prepared. The raw material powder is blended in the blending composition shown in Table 1, added with wax, ball mill mixed in acetone for 24 hours, dried under reduced pressure, and press-molded into a green compact of a predetermined shape at a pressure of 98 MPa. The green compact is vacuum-sintered in a vacuum of 5 Pa at a predetermined temperature within a range of 1370 to 1470 ° C. for 1 hour. After sintering, the cutting edge is subjected to a honing process of R: 0.07 mm. Thus, tool bases A to F made of a WC-based 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, NbC powder, TaC powder, WC powder, Co powder, all having an average particle diameter of 0.5 to 2 μm. , And Ni powder, these raw material powders are blended in the blending composition shown in Table 2, wet mixed with a ball mill for 24 hours, dried, and then pressed into a compact at a pressure of 98 MPa. The powder is sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after sintering, the cutting edge portion is subjected to a honing process of R: 0.07 mm to achieve ISO standard / CNMG120212. The tool bases a to d, f made of TiCN base cermet having the following chip shape were formed.

Next, each of the tool bases A to F and the tool bases a to d and f was charged into a normal chemical vapor deposition apparatus. First, Table 3 (l-TiCN in Table 3 is JP-A-6-8010). Table 4 shows the conditions for forming a TiCN layer having a vertically elongated crystal structure described in the publication, and other conditions for forming a normal granular crystal structure. A Ti compound layer having a target layer thickness to be formed is deposited as a lower layer of the hard coating layer, and then, under the low temperature and high pressure conditions shown in Table 3, with the combinations and target layer thicknesses shown in Table 4, the thickening reforming α The coated cermet tools 1 to 12 of the present invention were manufactured by vapor-depositing a type Al ₂ O ₃ layer as an upper layer of the hard coating layer.

For comparison purposes, a thickened normal α-type Al ₂ O ₃ layer is formed by vapor deposition as the upper layer of the hard coating layer under the normal conditions shown in Table 3 and the combinations and target layer thicknesses shown in Table 6. Except that, comparative coated cermet tools 1 to 12 were produced under the same conditions corresponding to each of the above-described coated cermet tools 1 to 12 of the present invention.

The invention described above coated cermet tools 1 to 12 and Comparative coated cermet tools 1 to thicken reforming α type constituting the upper layer of the hard coating layer of 12 Al ₂ O ₃ layer and a thick film normally α-type Al ₂ O _A tilt angle number distribution graph was created for each of the _three layers using a field emission scanning electron microscope.
That is, the inclination angle number distribution graph is set in a lens barrel of a field emission scanning electron microscope in a state where the surface of each of the various thickened α-type Al ₂ O ₃ layers is a polished surface. An electron backscattered diffraction image is obtained by irradiating an electron beam with an acceleration voltage of 15 kV at an incident angle of 70 ° to an individual crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface with an irradiation current of 1 nA. Using an apparatus, an inclination angle formed by a normal line of the (0001) plane that is a crystal plane of the crystal grain with respect to a normal line of the surface-polished surface in a 30 × 50 μm region at an interval of 0.1 μm / step Based on the measurement result, the measurement inclination angle within the range of 45 to 90 degrees is divided for each pitch of 0.25 degrees, and the frequency existing in each division is measured. Created by counting.

In the resulting gradient angle number distribution graphs of various thickened α-type Al ₂ O ₃ layers, the tilt angle section in which the (0001) plane shows the highest peak, and the tilt angle section within the range of 83 to 90 degrees. Tables 4 and 5 show the ratio of the number of tilt angles existing in the tilt angle number distribution graph to the entire tilt angle number distribution graph.

In the gradient angle distribution graphs of the above various thickened α-type Al ₂ O ₃ layers, as shown in Tables 4 and 5, respectively, as shown in Tables 4 and 5, the thickened modified α-type Al ₂ O ₃ layer of the present coated cermet tool In any of the above, the distribution of the measured inclination angle on the (0001) plane has the highest peak in the inclination angle section in the range of 83 to 89 degrees, and the inclination angle exists in the inclination angle section in the range of 83 to 90 degrees. In contrast to the inclination angle number distribution graph in which the ratio of the number is 45 to 77% , the thickened normal α-type Al ₂ O ₃ layer of the comparative coated cermet tool has a measured inclination angle of the (0001) plane. Inclination angle in which the distribution of 45-90 degrees is unbiased, the highest peak does not exist, and the ratio of the number of inclination angles existing in the inclination angle section in the range of 83-90 degrees is 30% or less A number distribution graph was shown.

Incidentally, FIG. 2, the inclination angle frequency distribution graph of the present invention thickened modified α type the Al ₂ O ₃ layer of the coated cermet tool 7, FIG. 3 is thickened usually α-type Al ₂ comparative coated cermet tool 7 The graph of the distribution of the number of inclination angles of the O ₃ layer is shown respectively.

Further, when the thickness of the resulting present invention coated cermet tools 1 to 12 and Comparative coated cermet tool 1-12 layers constituting the hard layer of the, was measured using a scanning electron microscope (longitudinal sectional measurement) , Each showed an average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness.

Next, in the state where each of the above various coated cermet tools is screwed to the tip of the tool steel tool with a fixing jig, the present coated cermet tools 1 to 12 and the comparative coated cermet tools 1 to 12 ,
Work material: JIS · SCM440 lengthwise equidistant 4 vertical grooved round bar,
Cutting speed: 220 m / min,
Cutting depth: 2.2mm,
Feed: 0.3mm / rev,
Cutting time: 20 minutes,
Dry interrupted cutting test of alloy steel under the following conditions (referred to as cutting condition A),
Work material: JIS / S50C round bar,
Cutting speed: 270 m / min,
Incision: 3mm,
Feed: 0.18mm / rev,
Cutting time: 20 minutes,
Dry continuous cutting test of carbon steel under the conditions (referred to as cutting condition B),
Work material: JIS / FCD450 round bar,
Cutting speed: 235 m / min,
Cutting depth: 2mm,
Feed: 0.35mm / rev,
Cutting time: 20 minutes,
The dry continuous cutting test of cast iron was performed under the above conditions (referred to as cutting condition C), 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, in the coated cermet tools 1 to 12 of the present invention, the upper layer of the hard coating layer is an inclination angle section in which the inclination angle of the (0001) plane is in the range of 83 to 89 degrees. It is composed of a thickening- modified α-type Al ₂ O ₃ layer that shows the highest peak and shows a gradient angle distribution graph in which the total frequency ratio existing in the range of 83 to 90 degrees occupies 45 to 77%. Despite the film thickness of 16-30 μm, the thickened modified α-type Al ₂ O ₃ layer exhibits excellent chipping resistance when cutting steel and cast iron, and the cutting edge portion The occurrence of chipping is significantly suppressed, and the wear resistance is improved over a long period of time, and the service life can be extended. On the other hand, the upper layer of the hard coating layer has a measured inclination angle of the (0001) plane. Distribution is unbiased within the range of 45 to 90 degrees, and there is no highest peak Comparative coated cermet tool 1-12 configured with thicker normal α type the Al ₂ O ₃ layer that shows an oblique angle frequency distribution graph are all the thickened usually α type the Al ₂ O ₃ layer is the average layer thickness When the film thickness is increased to 16 to 30 μm, the high temperature strength is remarkably lowered. As a result, chipping occurs at the cutting edge portion, and it is clear that the service life is reached in a short time.

As described above, the coated cermet tool according to the present invention can be used for various steels even when the α-type Al ₂ O ₃ layer, which is the upper layer of the hard coating layer, has an average layer thickness of 16 to 30 μm. It shows excellent chipping resistance in cutting work such as cast iron and cast iron, exhibits excellent wear resistance over a long period of time, and can extend the service life. It can cope with labor saving, energy saving and cost reduction of processing sufficiently satisfactorily.

It is a schematic diagram illustrating a measurement range of the inclination angle of the crystal grains (0001) plane in various thickened α type the Al ₂ O ₃ layer constituting the hard coating layer. It is an inclination angle number distribution graph of the (0001) plane of the thickening modified α-type Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool 7 of the present invention. 4 is a graph showing the inclination angle number distribution of the (0001) plane of the thickened normal α-type Al ₂ O ₃ layer constituting the hard coating layer of the comparative coated cermet tool 7.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) As a lower layer, each consists of one or two or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride oxide layer formed by chemical vapor deposition, And a Ti compound layer having an overall average layer thickness of 0.5 to 10 μm,
(B) Crystal grains having an α-type crystal structure in the state of chemical vapor deposition as an upper layer and having a hexagonal crystal lattice existing within the measurement range of the surface polished surface using a field emission scanning electron microscope Individually irradiated with an electron beam, and using an electron backscatter diffraction image apparatus, a predetermined region is a crystal plane of the crystal grain with respect to the normal of the surface polished surface at an interval of 0.1 μm / step (0001 ) Measure the tilt angle formed by the normal of the surface, and among the measured tilt angles, the measured tilt angles within the range of 45 to 90 degrees are divided into 0.25 degree pitches and exist in each section In the inclination angle distribution graph obtained by summing up the frequencies, the highest peak exists in the inclination angle section within the range of 83 to 89 degrees, and the total of the frequencies existing within the range of 83 to 90 degrees is the inclination angle. 45 of the total power in the number distribution graph to 77% Shows an inclination angle frequency distribution graph in a proportion, and thickening modified α-type aluminum oxide layer having an average layer thickness of 16～30Myuemu,
A surface-coated cermet cutting tool that exhibits excellent chipping resistance with a thickened α-type aluminum oxide layer formed by vapor-depositing the hard coating layer composed of (a) and (b) above.

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