Grain boundary strengthened alpha-al2o3 coated cutting tool and method of making

Abstract

The present application relates to the technical field of coating tools, and provides a grain boundary strengthened alpha-Al2O3 coating cutting tool and a preparation method thereof, the cutting tool comprising a substrate and a coating on the surface of the substrate; the coating comprises at least one alpha-Al2O3 coating deposited by a CVD method; a polished cross section of the alpha-Al2O3 coating with a depth less than 60% of the thickness and parallel to the surface of the coating is analyzed by an electron backscatter device; in an orientation difference angle distribution diagram, adjacent grain orientation difference angles appear as the highest peak in the range of 60+ / -8.7 degrees, and the proportion is greater than 0.3. The cutting tool with the grain boundary strengthened alpha-Al2O3 coating has excellent wear resistance and collapse resistance in the turning of steel parts.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coated cutting tools, and particularly relates to a grain boundary strengthened alpha-Al2O3 coated cutting tool and a preparation method thereof. BACKGROUND

[0002] Alpha-Al2O3 has excellent mechanical properties, thermal stability and oxidation resistance, and is widely used as a coating material for metal cutting tools. Modern manufacturing industry has an increasing demand for high-speed and efficient processing, and higher requirements are put forward for the performance of coated cutting tools. In order to meet the demand of high-speed and efficient processing, the current cutting tool materials, especially the cutting tool coating materials, must improve the high-temperature wear resistance and the anti-chipping performance of the coating materials at the same time.

[0003] Alpha-Al2O3 belongs to the trigonal system, and the space group is R The oxygen ions are stacked in the form of …ABABAB…, and the aluminum ions are orderly filled in the octahedral voids formed by the stacking of oxygen atoms, occupying 2 / 3 of the positions. Controlling the growth of alpha-Al2O3 crystals along the <0001> direction can improve the high-temperature wear resistance of the coating. However, the alpha-Al2O3 coating with (001) texture presents a typical columnar crystal structure. When cutting under unstable conditions, cracks can easily propagate along the columnar crystal grain boundaries and penetrate through the coating due to frequent external force impact or thermal shock, resulting in cracking and peeling of the coating and reducing the service life of the coating.

[0004] Grain boundary engineering is a method of optimizing material performance by controlling the grain boundary structure of the material. The more ordered the atomic arrangement at the grain boundary, the lower the grain boundary energy and the more stable the structure. When the adjacent grains of alpha-Al2O3 rotate around a specific axis by a specific angle, the grain boundary energy has a minimum value. The synergistic plastic deformation ability and the anti-crystal fracture performance of the adjacent grains of alpha-Al2O3 with this grain boundary are enhanced. Therefore, grain boundary strengthening is an important breakthrough for further improving the performance of (001) textured alpha-Al2O3 coating. SUMMARY

[0005] To solve the problems existing in the prior art, the present application aims to provide a grain boundary strengthened alpha-Al2O3 coated cutting tool with wear resistance and impact resistance and a preparation method thereof.

[0006] According to a first aspect of the present application, the present application provides the following technical solution:

[0007] A grain boundary strengthened alpha-Al2O3 coated cutting tool, comprising:

[0008] a substrate and a coating on the surface of the substrate;

[0009] The coating comprises at least one alpha-Al2O3 coating deposited by a CVD method, and the polished cross section of the alpha-Al2O3 coating with a depth less than 60% of the thickness and parallel to the surface of the coating is analyzed by an electron backscatter device, in an orientation difference angle distribution diagram, the highest peak of the orientation difference angle of adjacent grains appears in the range of 60±8.7°, and the proportion is greater than 0.3.

[0010] As a preferred scheme of the crystal boundary reinforced alpha-Al2O3 coating cutting tool, the substrate is cemented carbide, ceramic or superhard material, the coating is distributed from the surface of the substrate to the outside in six layers, the total thickness of the coating is 1-35 μm, the first layer comprises one or more layers selected from TiN or TiCN, and the thickness is 0.1-2 μm; the second layer is an MT-TiCN coating, and the thickness is 1-15 μm; the third layer is a (Ti 1-w Al w )(C x N y O z ) coating, and the thickness is 0.1-0.5 μm; the fourth layer is a Ti a O b coating, and the thickness is 0.3-2 nm; the fifth layer is an alpha-Al2O3 coating, and the thickness is 1.3-23 μm; and the sixth layer is a TiN coating, and the thickness is 0.1-2 μm.

[0011] According to the second aspect of the present application, the present application provides the following technical scheme:

[0012] A preparation method of the above-mentioned crystal boundary reinforced alpha-Al2O3 coating cutting tool, comprising: preparing a coating on the surface of the substrate, wherein the preparation method of the alpha-Al2O3 coating is as follows: under the deposition temperature of 900-1020 ℃ and the deposition pressure of 50-250 mbar, a mixed gas of 1.68-2.32 vol% AlCl3, 4.66-5.49 vol% CO2, 2.52-4.89 vol% HCl, 1.1%-2.4% CO and the balance of H2 is introduced, and the deposition time is 10-30 min; then, a mixed gas of 1.68-2.32 vol% AlCl3, 4.66-5.49 vol% CO2, 2.52-4.89 vol% HCl, 1.0-1.6 vol% H2S, 1.1%-2.4% CO and the balance of H2 is introduced, and the deposition time is 60-1000 min.

[0013] The present application has the following beneficial effects:

[0014] The present application provides a grain boundary strengthened alpha-Al2O3 coating cutting tool and a preparation method thereof, the cutting tool comprising a substrate and a coating on the surface of the substrate; the coating comprises at least one alpha-Al2O3 coating deposited by a CVD method, and the alpha-Al2O3 coating has a polished cross section with a depth less than 60% of the thickness and parallel to the surface of the coating; in an orientation difference angle distribution diagram, the orientation difference angle of adjacent grains appears a highest peak in a range of 60±8.7°, and the proportion is greater than 0.3. The cutting tool with the grain boundary strengthened alpha-Al2O3 coating has excellent wear resistance and collapse resistance in steel turning. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from the structures shown in the drawings without creative labor.

[0016] Figure 1 is an EBSD inverse pole figure distribution diagram of the alpha-Al2O3 coating polished surface of sample A of the present application.

[0017] Figure 2 is an EBSD pole figure of the alpha-Al2O3 coating polished surface of sample A of the present application.

[0018] Figure 3 is an EBSD inverse pole figure of the alpha-Al2O3 coating polished surface of sample A of the present application.

[0019] Figure 4 is an orientation difference angle distribution diagram of the alpha-Al2O3 coating polished surface of sample A of the present application.

[0020] Figure 5 is an orientation difference angle distribution diagram of the alpha-Al2O3 coating polished surface of sample B of the present application.

[0021] Figure 6 is an orientation difference angle distribution diagram of the alpha-Al2O3 coating polished surface of sample C of the present application.

[0022] Figure 7 is an orientation difference angle distribution diagram of the alpha-Al2O3 coating polished surface of sample D of the present application.

[0023] Figure 8 is an orientation difference angle distribution diagram of the alpha-Al2O3 coating polished surface of sample E of the present application.

[0024] Figure 9is the alpha-Al2O3 coating polished surface orientation difference angle distribution diagram of the control sample F.

[0025] The purposes, functional features and advantages of the present application will be further illustrated in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0027] According to a first aspect of the present application, the present application provides the following technical solutions:

[0028] A grain boundary strengthened alpha-Al2O3 coating cutting tool, comprising:

[0029] a substrate and a coating on the surface of the substrate;

[0030] The coating comprises at least one alpha-Al2O3 coating deposited by a CVD method, and the polished section of the alpha-Al2O3 coating with a depth less than 60% of the thickness and parallel to the surface of the coating is analyzed by an electron backscatter device, in the orientation difference angle distribution diagram, the adjacent grain orientation difference angle in the range of 60±8.7° appears the highest peak, and the proportion is greater than 0.3.

[0031] Preferably, the polished section of the alpha-Al2O3 coating with a depth less than 60% of the thickness and parallel to the surface of the coating is analyzed by an electron backscatter device, and specifically, the depth of the polished section of the alpha-Al2O3 coating can be, for example, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10% and the like of the thickness of the alpha-Al2O3 coating.

[0032] Preferably, in the orientation difference angle distribution diagram of the alpha-Al2O3 coating, the adjacent grain orientation difference axis in the range of 60±8.7° is <0001> direction.

[0033] Preferably, on the polished section of the alpha-Al2O3 coating with a depth less than 60% of the thickness and parallel to the surface of the coating, the area proportion of the alpha-Al2O3 grains with the <0001> direction and the normal of the surface of the coating at an angle less than 10° is greater than 60%.

[0034] Preferably, the random distribution multiple in the inverse pole figure along the growth direction of the coating in the polished section of the alpha-Al2O3 coating with a depth less than 60% of the thickness and parallel to the surface of the coating appears a peak value close to the <0001> direction, and the peak value is greater than 30 MRD.

[0035] Preferably, the α-Al2O3 coating has a microstructure with a preferred growth direction <006> and a texture coefficient greater than 6; the texture coefficient is defined as follows:

[0036]

[0037] wherein:

[0038] I(hkl) is the reflection intensity of the (hkl) crystal plane measured by X-ray diffraction;

[0039] I0 is the standard intensity of the diffraction reflection according to PDF card No. 46-1212;

[0040] n is the number of reflection crystal planes used in the calculation;

[0041] The (hkl) reflection crystal planes used are (012), (104), (110), (006), (113), (116), and (300).

[0042] Preferably, the α-Al2O3 coating has a columnar crystal structure perpendicular to the surface of the coating, a coating grain size less than 2.5 μm, and a hardness greater than 27 GPa.

[0043] Preferably, the substrate is cemented carbide, ceramic, or superhard material.

[0044] Preferably, the coating is distributed in six layers from the surface of the substrate to the outside, and the total thickness of the coating is 1-35 μm; the first layer comprises one or more layers selected from TiN or TiCN, and the thickness is 0.1-2 μm; the second layer is an MT-TiCN coating, and the thickness is 1-15 μm; the third layer is a (Ti 1-w Al w )(C x N y O z ) coating, and the thickness is 0.1-0.5 μm; the fourth layer is a Ti a O b coating, and the thickness is 0.3-2 nm; the fifth layer is an α-Al2O3 coating, and the thickness is 1.3-23 μm; and the sixth layer is a TiN coating, and the thickness is 0.1-2 μm.

[0045] Preferably, the MT-TiCN coating has a surface roughness Ra less than 200 nm; in the Ti a O b coating, 1.5 < a < 2.5 and 2.5 < b < 3.5; in the (Ti 1-w Al w )(C x N y O z) the coating has a nano-needle or flake structure, wherein w<0.2, 0.5

[0046] According to a second aspect of the present application, the present application provides the following technical solutions:

[0047] A preparation method of the above-mentioned grain boundary strengthened alpha-Al2O3 coating cutting tool, comprising: preparing a coating on the surface of a substrate, wherein the preparation method of the alpha-Al2O3 coating is as follows: under a deposition temperature of 900-1020 DEG C and a deposition pressure of 50-250 mbar, a mixed gas of 1.68-2.32 vol% AlCl3, 4.66-5.49 vol% CO2, 2.52-4.89 vol% HCl, 1.1%-2.4% CO and the balance H2 is introduced, and the deposition time is 10-30 min; then, a mixed gas of 1.68-2.32 vol% AlCl3, 4.66-5.49 vol% CO2, 2.52-4.89 vol% HCl, 1.0-1.6 vol% H2S, 1.1%-2.4% CO and the balance H2 is introduced, and the deposition time is 60-1000 min.

[0048] The present application uses Oxford Nordlys Max3 detector installed in SEM to characterize the grain boundary and crystal growth characteristics of the coating by electron backscatter diffraction (EBSD) technology. Before EBSD test, the coating surface of the sample is mechanically polished and treated by argon ion polishing to ensure that the electron beam can produce clear diffraction pattern. The coating surface is scanned with a step of 0.05 μm, and the Kikuchi pattern reflected by different grains is recorded. The data collected by the device is imported into AZtecCrystal software for analysis, and pole figure, inverse pole figure and misorientation distribution map are constructed. Misorientation is the smallest equivalent misorientation between two orientation measurements in crystallography. In the misorientation distribution map, Neighbor Pair, Random Pair and Theoretical three types of misorientation data can be displayed. Among them, Neighbor Pair is the adjacent pair, which is the misorientation between adjacent data points, indicating the misorientation between adjacent grains, i.e. the grain boundary misorientation angle. MRD (Multiples of a Random Distribution) in the inverse pole figure is the multiple of random distribution, which is a quantitative index to describe the density of a specific crystal direction relative to random distribution. The value of MRD is obtained by comparing the actual measurement density of a specific crystal plane or crystal direction with the theoretical density of completely random orientation distribution. If the MRD value of a direction is 1, it indicates that the grain orientation in this direction is consistent with the completely random distribution; if the MRD value is less than 1, it indicates that the grain orientation in this direction is more sparse than the random distribution; on the contrary, if the MRD value is greater than 1, it indicates that the grain orientation in this direction is more dense than the random distribution. Among them, the area with high MRD value indicates that the crystal orientation has a tendency to concentrate in these areas.

[0049] The technical solutions of the present application are further described below in combination with specific examples.

[0050] Examples

[0051] According to the description of the present application, 6 layers of coating are coated on the indexable carbide insert CNMG 120408E-PD3 insert by CVD technology, the carbide component is 8.2wt% of Co, 4.5wt% of cubic carbide, 0.6wt% of TiN and the balance of WC, the thickness of the 6 layers is about 15 μm, from the substrate to the outside in turn, respectively: TiN coating (about 0.5 μm), MT-TiCN coating (about 8.0 μm), TiAlOCN coating (about 0.5 μm), Ti2O3 coating (about 1 nm), α-Al2O3 coating (about 6.0 μm) and TiN coating (about 0.3 μm), wherein TiN is an optional coating. Six kinds of samples prepared are respectively called sample A (the present application), sample B (the present application), sample C (the present application), sample D (the present application), sample E (the control group), sample F (the control group). The process parameters of deposition are shown in the following table.

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058] According to the method, the polished surface of the sample coating is observed by electron backscattered diffraction (EBSD), and the polished cross section of the α-Al2O3 coating (about 1 μm) is analyzed, which is about 1 / 6 of the thickness and parallel to the surface of the coating. The EBSD inverse pole figure distribution map of the polished surface of the α-Al2O3 coating of sample A is shown in FIG. 1. The EBSD pole figure of the polished surface of the α-Al2O3 coating of sample A is shown in FIG. 2, and the <0001> direction of each grain of the α-Al2O3 coating is substantially perpendicular to the polished surface of the coating. The EBSD inverse pole figure of the polished surface of the α-Al2O3 coating of sample A is shown in FIG. 3, and the <0001> direction of each grain of the α-Al2O3 coating is strongly concentrated in the normal direction of the coating surface, and the peak value of the random distribution multiple is 85.8 MRD, indicating that the coating has a obvious <0001> preferred orientation in this direction. The misorientation angle distribution maps of the polished surfaces of the α-Al2O3 coatings of samples A-F are shown in FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8 and FIG. 9, respectively. Figure 1 Figure 2 Figure 3 Figures 4~9 ​​​The proportion of adjacent grain orientation difference angle of the alpha-Al2O3 coating in the range of 60±8.7° is about 0.82, 0.61, 0.48, 0.36, 0.26 and 0.19, respectively.

[0059] In terms of coating performance, the cutting performance of the comparative samples is compared by continuous and intermittent turning of the steel piece.

[0060] Test one:

[0061] Operation: continuous turning

[0062] Workpiece: cylindrical piece

[0063] Material: 4340 alloy steel

[0064] Blade type: CNMG 120408E-PD3

[0065] Cutting speed: 310 m / min

[0066] Feed: 0.23 mm / rev

[0067] Depth of cut: 2.0 mm

[0068] Dry / wet cutting: wet cutting

[0069] The amount of flank wear VB greater than 0.3 mm after the blade is taken as the failure criterion. The continuous cutting life of different samples is shown in the following table.

[0070]

[0071] It can be seen that the blade of the present application greatly improves the wear resistance of the coating. In the cutting process, the crater wear of samples A~D is less than that of samples E~F at each time node.

[0072] Test two:

[0073] Operation: intermittent turning

[0074] Workpiece: slotted cylindrical piece

[0075] Material: 4340 alloy steel

[0076] Blade type: CNMG 120408E-PD3

[0077] Cutting speed: 250 m / min

[0078] Feed: 0.22 mm / rev

[0079] Depth of cut: 1.8 mm

[0080] Dry / wet cutting: wet cutting

[0081] The later VB of the tool face wear is greater than 0.3 mm as a failure criterion. The intermittent cutting life of different samples is shown in the following table.

[0082]

[0083] From the above table, it can be seen that the coating cutting blade of the present application improves the chipping resistance of the tool.

[0084] Compared with the prior art, the blade of the present application improves the tool life whether continuous or intermittent.

[0085] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation, direct / indirect application in other related technical fields made by using the content of the present application specification under the inventive concept of the present application are included in the patent protection scope of the present application.

Claims

1. A grain boundary strengthened α-ΑΙ203 coated cutting tool, characterized in that, Comprise: a substrate and a coating on the surface of the substrate; the coating comprises at least one α-Al2O3 coating deposited by CVD method, the polished cross section of the α-Al2O3 coating less than 60% of the thickness and parallel to the surface of the coating is analyzed by electron backscatter device, in the orientation difference angle distribution diagram, the highest peak of the orientation difference angle of adjacent grains in the range of 60±8.7° appears, and the proportion is greater than 0.3; in the orientation difference angle distribution diagram of the α-Al2O3 coating, the orientation difference axis of adjacent grains in the range of 60±8.7° is <0001> crystal direction; in the inverse pole figure along the growth direction of the α-Al2O3 coating, the peak value of the random distribution multiple appears near the <0001> crystal direction, and the peak value is greater than 30MRD; the area proportion of the α-Al2O3 grains with the angle between the <0001> crystal direction of the α-Al2O3 coating and the normal of the coating surface less than 10° is greater than 60%; the preparation method of the α-Al2O3 coating is that under the deposition temperature of 900-1020℃ and the deposition pressure of 50-250mbar, the mixed gas of 1.68-2.32vol% AlCl3, 4.66-5.49vol% CO2, 2.52-4.89vol% HCl, 1.1%-2.4% CO and the balance H2 is introduced, and the deposition time is 10-30min; then, the mixed gas of 1.68-2.32vol% AlCl3, 4.66-5.49vol% CO2, 2.52-4.89vol% HCl, 1.0-1.6vol% H2S, 1.1%-2.4% CO and the balance H2 is introduced, and the deposition time is 60-1000min.

2. The grain- strengthened α-ΑΙ203coated cutting tool according to claim 1, characterized in that The α-Al2O3 coating as a whole presents a microstructure structure of preferential growth in the <006> direction, and the texture coefficient is greater than 6.

3. The grain- strengthened α-ΑΙ203coated cutting tool according to claim 1, characterized in that The α-Al2O3 coating has a columnar crystal structure perpendicular to the surface of the coating, the grain size of the coating is less than 2.5μm, and the hardness is greater than 27GPa.

4. The grain- strengthened α-ΑΙ203coated cutting tool according to claim 1, characterized in that The coating is distributed outward from the surface of the substrate in six layers in turn, and the total thickness of the coating is 1-35μm, the first layer comprises one or more layers selected from TiN or TiCN, and the thickness is 0.1-2μm. The second layer is an MT-TiCN coating layer, with a thickness of 1-15 μm; the third layer is a (Ti 1-w Al w )(C x N y O z ) coating layer, with a thickness of 0.1-0.5 μm; the fourth layer is a Ti a O b coating layer, with a thickness of 0.3-2 nm; the fifth layer is an α-Al2O3 coating layer, with a thickness of 1.3-23 μm; and the sixth layer is a TiN coating layer, with a thickness of 0.1-2 μm.

5. The grain- strengthened α-ΑΙ203coated cutting tool according to claim 4, characterized in that The MT-TiCN coating has a surface roughness Ra less than 200 nm; the Ti a O b In the coating, 1.5 < a < 2.5, 2.5 < b < 3.

5.

6. The grain- strengthened α-ΑΙ203coated cutting tool according to claim 4, characterized by said (Ti 1-w Al w )(C x N y O z ) coating has a nano-needle or flake structure, wherein w < 0.2, 0.5 < x < 0.7, 0.2 < y < 0.5, 0 ≤ z ≤ 0.2, x + y + z = 1.

7. A method of producing a cutting tool coated with the grain boundary-strengthened α- Al2O3 of any one of claims 1 to 6, characterized by, Comprise: preparing a coating on the surface of the substrate, wherein the preparation method of the α-Al2O3 coating is that under the deposition temperature of 900-1020℃ and the deposition pressure of 50-250mbar, the mixed gas of 1.68-2.32vol% AlCl3, 4.66-5.49vol% CO2, 2.52-4.89vol% HCl, 1.1%-2.4% CO and the balance H2 is introduced, and the deposition time is 10-30min; then, the mixed gas of 1.68-2.32vol% AlCl3, 4.66-5.49vol% CO2, 2.52-4.89vol% HCl, 1.0-1.6vol% H2S, 1.1%-2.4% CO and the balance H2 is introduced, and the deposition time is 60-1000min.

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