Coating material for milling cutter and preparation method of coating material

Abstract

The invention belongs to the technical field of plating materials, and relates to a plating material for a milling cutter and a preparation method of the plating material. The invention provides a coating material for a milling cutter. The coating material is composed of a base layer, a first transition layer, a second transition layer, a third transition layer and a working layer on the surface of a milling cutter base body from inside to outside. The base layer is made of Cr, the first transition layer is made of CrN, the second transition layer is made of CrAlYN, the third transition layer is made of CrAlMoN, and the working layer is made of CrAlYN; the content of Cr in the first transition layer is gradually reduced along with the increase of the thickness of the first transition layer. The technical problem that the steady state of the cutting force is poor at the high cutting speed is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of plating materials and relates to a plating material for a milling cutter and a preparation method thereof. Background Art

[0002] Modern metal milling requires milling cutters to have high milling speed, high feed rate, high reliability, long life, high precision and good milling control. The emergence of coated tools has made a major breakthrough in the milling performance of milling cutters. It combines the milling cutter substrate with the hard film surface. Since the substrate maintains good toughness and high strength, and the hard film surface has high wear resistance and low friction coefficient, the performance of the milling cutter is greatly improved. At present, it is quite common for most milling cutters (including high-speed steel milling cutters and carbide milling cutters) to be coated with carbides and nitrides on the substrate surface, and a considerable proportion of milling cutters need to be plated again when they are reground after use.

[0003] Universal coatings are designed to achieve uniform processing results in a wide range of applications. However, for specific application areas, such coatings can only be an alternative. For example, TA15 titanium alloy is composed of T-6A1-2Z-1Mo-1V, which is a high aluminum equivalent near-α type alloy. The alloy has moderate room temperature and high temperature strength, good thermal stability and welding performance, and is widely used to manufacture various types of aviation structural parts. In the precision machine tool processing of TA15 titanium alloy, the surface roughness gradually decreases with the increase of milling speed. When the cutting speed is low, it is easy to form built-up edge and scale burrs. The higher the cutting speed, the less sufficient the surface plastic deformation, and the smaller the surface roughness can be obtained. For some universal coatings, when it is used for TA15 titanium alloy processing, as the cutting force increases, the change of its dynamic cutting force will also increase, and as the contact area between the tool and the workpiece increases, the change of its dynamic cutting force will also increase, affecting the precision of the processing. In short, only coatings that truly meet the specific needs of tools and application conditions can achieve substantial specific application effects. The coating is considered to be an integral part of the tool, just like the geometry and the base material, which should be matched to the specific application conditions and optimized. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problem that when the existing coating is used for processing TA15 titanium alloy, the dynamic cutting force changes greatly at a high cutting speed, making it difficult to perform precision processing. To this end, the present invention provides a coating material for a milling cutter and a preparation method thereof to solve this need in the art.

[0005] On the one hand, the present invention relates to a coating material for a milling cutter, wherein the coating material is composed of a primer layer, a first transition layer, a second transition layer, a third transition layer and a working layer from the inside to the outside on the surface of the milling cutter base body; The base layer is Cr, the first transition layer is CrN, the second transition layer is CrAlYN, the third transition layer is CrAlMoN, and the working layer is CrAlYN; The Cr content of the first transition layer gradually decreases as the thickness thereof increases.

[0006] Furthermore, in the coating material for a milling cutter provided by the present invention, the thickness of the base layer is 0.1~0.3μm, the thickness of the first transition layer is 0.5~1.5μm, the thickness of the second transition layer is 0.5~1.5μm, the thickness of the third transition layer is 60~120nm, and the thickness of the working layer is 1.5~3μm.

[0007] Furthermore, in the coating material for a milling cutter provided by the present invention, the atomic ratio of Cr to N in the first transition layer varies in the range of 3 to 1:2.

[0008] Furthermore, in the coating material for a milling cutter provided by the present invention, in any of the CrAlYN, in terms of atomic percentage, Cr is 20-60%, Al is 2-10%, Y is 1-15%, and N is the remainder.

[0009] Furthermore, in the coating material for a milling cutter provided by the present invention, the atomic percentage content of Y in the second transition layer is at least 3% less than the atomic percentage content of Y in the working layer.

[0010] Furthermore, in the coating material for a milling cutter provided by the present invention, in the CrAlMoN, by atomic percentage, Cr is 20-60%, Al is 2-10%, Mo is 4-8%, and N is the remainder.

[0011] In another aspect, the present invention relates to a milling cutter, which is composed of a milling cutter base body and the coating material on the surface of the milling cutter base body.

[0012] In another aspect, the present invention relates to the use of the milling cutter in metal processing.

[0013] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: The present invention provides a coating material for a milling cutter and a preparation method thereof, aiming to solve the technical problems of large fluctuations in dynamic cutting force and unstable machining accuracy of existing coatings during high-speed cutting. The core technology is to design a coating with a multi-layer gradient structure, which is composed of a Cr base layer, a CrN first transition layer, a CrAlYN second transition layer, a CrAlMoN third transition layer and a CrAlYN working layer from the inside to the outside, and each layer synergistically improves performance through optimization of composition and thickness. The multi-layer structure of the coating gradually adjusts the hardness and toughness of the material through gradient design to reduce interlayer stress concentration. The Cr base layer enhances the bonding force between the substrate and the coating; the Cr content in the CrN first transition layer decreases with thickness, forming a composition gradient and optimizing interlayer matching; the Y element in CrAlYN refines the grains, improves the density of the coating, and inhibits crack propagation; the Mo element is introduced into the CrAlMoN third transition layer to improve high temperature stability and anti-friction performance and reduce cutting heat accumulation. The Y content in the second transition layer is at least 3% less than that in the working layer. The characteristic that the change of Y content in CrAlYN leads to the change of material properties is used to further strengthen the supporting role of the intermediate layer, while the working layer ensures the surface wear resistance by balancing the composition. The coating significantly improves the stability of the milling cutter when cutting TA15 titanium alloy at high speed through the coordinated optimization of composition and structure. Experimental data show that compared with the traditional AlTiN coated milling cutter, the milling cutter of the present invention has significantly reduced cutting force fluctuations at long cutting distances, proving that the cutting force stability is greatly improved. At the same time, the introduction of the third transition layer further effectively delays the phenomenon of increased cutting force dispersion, prolongs the tool life, and improves the quality of the processed surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 It is a line graph of cutting distance of #1 milling cutter relative to average cutting force.

[0016] Figure 2 It is a line graph of cutting distance relative to average cutting force for #2 milling cutter.

[0017] Figure 3 This is a line graph of the cutting distance of the #3 milling cutter relative to the average cutting force.

[0018] Figure 4 It is a line graph of cutting distance relative to average cutting force for #4 milling cutter.

[0019] Figure 5This is a line graph of the cutting distance of the #5 milling cutter relative to the average cutting force.

[0020] Figure 6 The figure is a line graph showing the cutting distance of a commercially available coated milling cutter relative to the average cutting force. DETAILED DESCRIPTION

[0021] The technical scheme of the present invention is described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials can be purchased on the market unless otherwise specified. The % in the following embodiments, unless otherwise specified, are all mass percentages. The ratios in the following embodiments, unless otherwise specified, are all mass ratios.

[0022] In the following examples, the material to be processed (workpiece) used is TA15 titanium alloy, the composition is Ti-6.5Al-2Zr-1Mo-1V, which is an α-type alloy. It is smelted twice in a vacuum consumable furnace, the ingot is forged in the β region, and forged in the upper part of the α-β two-phase region. Its physical properties are tensile strength σ b is 1134MPa, and the yield limit σ 0.2 is 943MPa, elastic modulus E is 134GPa, elongation δ 5 The cross-sectional shrinkage rate ψ is 13.2% and 43.9%.

[0023] The following machining tests were carried out on a CNC vertical machining center, model VMC850, a CNC milling machine, with a three-axis guide rail, a spindle speed of 100~8000rpm, a main motor power of 7.5kW, and emulsion lubrication and cooling during machining. The rotation direction of the contact part between the milling cutter and the workpiece is the same as the workpiece feed direction.

[0024] The helix angle of the milling cutter used in the following tests is 45°. The distance from the clamping point to the cutting point of the cutter is kept at 40 mm, and the milling depth is a p The milling width a is 1 mm. e The feed per tooth is 8mm. z is 0.05mm / z, milling speed v c It is 40m / min (the limit value of general milling cutters).

[0025] Milling force is one of the most important physical quantities in the milling process. Its generation is based on the cutting deformation process. The milling force directly affects the generation of cutting heat, and further affects the wear and breakage of the tool, tool durability and machining surface quality. In the following test, the milling force measurement equipment is the Swiss Kistler9257B three-axis milling dynamometer, which is based on the machine tool worktable and is divided into x-axis, y-axis and z-axis. The y-axis is the feed direction of the tool. The average milling force in the statistics is the average of the milling forces of the x-axis, y-axis and z-axis.

[0026] Example This embodiment provides a process for preparing a coating material for a milling cutter.

[0027] The milling cutter base is a tungsten-molybdenum general high-speed steel with a composition of W6Mo5Cr4V2, a high-performance cutting tool material with excellent hardness, wear resistance, heat resistance and processing performance. It is particularly suitable for applications with high requirements on cutting speed, wear resistance and heat resistance, such as metal processing, aerospace, etc.

[0028] The cleaned milling cutter substrate is placed in the equipment fixture. It is first cleaned by argon plasma bombardment to clean the surface of the tool to improve the adhesion of the coating. Then the coating treatment is carried out. Each coating first uses a target material of Cr, Al, Y, and N (pure Cr target, pure Al target, pure Y target, and N 2 Gas), when preparing the third transition layer, replace the Y target with the Mo target, and when preparing the working layer, replace the Mo target back to the Y target. Before sputtering, ultrasonic cleaning is used to remove impurities such as oil on the surface of the target material to improve the surface quality of the coating. The quality purity of each target is ≥99.99%. The target material is placed at the cathode and the titanium substrate is placed at the anode. The sputtering power is 100~500W. The component content of each layer is controlled by changing the sputtering power of each target material, and the thickness of each layer is controlled by changing the sputtering time.

[0029] Based on the above preparation process, the base layer, the first transition layer-1, the first transition layer-2, the first transition layer-3, the second transition layer, the third transition layer and the working layer are sputtered on the surface of the milling cutter substrate in sequence to obtain the coating materials for the milling cutter shown in #1~#5. The thickness and atomic percentage content of each layer are shown in Tables 1~7.

[0030] Table 1 Thickness of coating materials used for milling cutters

[0031] Generally, in the coating material (#1 to #3) for a milling cutter provided by the present invention, the content of the components of each layer is expressed in atomic percentage, as shown in Table 2.

[0032] Table 2 Atomic percentage content of each layer component provided by the present invention

[0033] And the Cr contents in the first transition layer-1, the first transition layer-2 and the first transition layer-3 decrease in sequence, and the atomic percentage content of Y in the second transition layer is at least 3% less than the atomic percentage content of Y in the working layer.

[0034] Exemplarily, the preparation process of the coating material for a milling cutter shown in #1 is as follows: Step 1: Clean the milling cutter substrate and place it in the equipment fixture. First, it is cleaned by argon plasma bombardment to clean the surface of the tool to improve the adhesion of the coating, and then the coating treatment is performed.

[0035] Step 2: The working gas is argon, and the vacuum degree of the magnetron sputtering equipment is controlled to reach 1×10 -6 The coating started after Pa, the milling cutter substrate was rotated at a speed of 10r / min, the distance between the sample and the target was 200mm, and a Cr target was used to deposit a base layer on the surface of the milling cutter substrate. The sputtering power of the Cr target was 460W. After opening the Cr target baffle for 3 minutes, a 0.1μm base layer was formed on the surface of the milling cutter substrate, and the composition of the obtained base layer was Cr.

[0036] Step 3: Turn off the argon gas, introduce nitrogen gas into the chamber, set the nitrogen flow rate to 500 sccm, open the Cr target baffle for 5 minutes, and form a 0.2 μm first transition layer-1. The composition of the obtained first transition layer-1 is CrN.

[0037] Step 4: Maintaining nitrogen, adjusting the sputtering power of the Cr target to 320 W, opening the Cr target baffle for 5 minutes, and forming a 0.2 μm first transition layer-2, the composition of which is CrN.

[0038] Step 5: Maintaining nitrogen, adjusting the sputtering power of the Cr target to 200 W, opening the Cr target baffle for 3 minutes, and forming a first transition layer-3 of 0.1 μm. The composition of the obtained first transition layer-3 is CrN.

[0039] Step 6: Maintaining nitrogen, adjust the sputtering power of the Cr target to 460 W, the sputtering power of the Al target to 180 W, and the sputtering power of the Y target to 100 W. At the same time, open the baffles of the Cr target, Al target, and Y target for 15 minutes to form a second transition layer of 0.5 μm. The composition of the obtained second transition layer is CrAlYN.

[0040] Step 7: Maintaining nitrogen, adjust the sputtering power of the Cr target to 460 W, the sputtering power of the Al target to 180 W, and the sputtering power of the Mo target to 280 W. At the same time, open the baffles of the Cr target, Al target, and Mo target for 1.5 minutes to form a 60nm third transition layer, and the composition of the obtained third transition layer is CrAlMoN.

[0041] Step 8: Maintaining nitrogen, adjust the sputtering power of the Cr target to 460 W, the sputtering power of the Al target to 180 W, and the sputtering power of the Y target to 340 W. At the same time, open the baffles of the Cr target, Al target, and Y target for 60 minutes to form a 1.5 μm working layer, and the composition of the obtained working layer is CrAlYN.

[0042] The element contents of each coating layer of the coating material actually prepared for the milling cutter are shown in Tables 3 to 5.

[0043] Table 3 Atomic percentage content of each layer component in #1

[0044] Table 4 Atomic percentage content of each layer component in #2

[0045] Table 5 Atomic percentage content of each layer component in #3

[0046] Table 6 Atomic percentage content of each layer component in #4

[0047] Table 7 Atomic percentage content of each layer component in #5

[0048] In addition, the commercially available coated milling cutter for comparison is a solid carbide four-edge end mill with a nano-coating whose composition is AlTiN.

[0049] The change of the cutting distance from 0 to 8000 mm relative to the average cutting force was measured, and a regression equation was constructed. 2 Judging the stability of the cutting force, the test results of #1~#5 correspond to Figures 1 to 5 , Figure 6 The test results of commercially available coated milling cutters are shown in Table 8.

[0050] Table 8 Regression equation of cutting distance relative to average cutting force

[0051] As can be seen from Table 8, the present invention can effectively improve the stability of the milling cutter during high-speed cutting of TA15 titanium alloy by adjusting the Cr content in the first transition layer to change with the gradient of thickness, and further improve the stability of the milling cutter during high-speed cutting of TA15 titanium alloy by setting the CrAlMoN thin layer and the difference in Y content in the second transition layer and the working layer. Among them, #4 does not have a third transition layer, and its cutting force dispersion increases significantly when the cutting distance is about 7000mm. #5 uses a similar Y content in the second transition layer and the working layer, and its cutting force dispersion increases significantly when the cutting distance is about 5000mm. The commercially available coated milling cutter is completely unsuitable for high-speed cutting at long cutting distances, and a significant increase in cutting force dispersion occurs when the cutting distance is about 3000mm.

[0052] As described above, the basic principle, main features and advantages of the present invention are well described. The above embodiments and descriptions are only descriptions of the preferred implementation modes of the present invention, and the present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, various changes and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the protection scope determined by the present invention.

Claims

1. A coating material for a milling cutter, characterized in that: The coating material is composed of a base layer, a first transition layer, a second transition layer, a third transition layer and a working layer from the inside to the outside on the surface of the milling cutter base body; The base layer is Cr, the first transition layer is CrN, the second transition layer is CrAlYN, the third transition layer is CrAlMoN, and the working layer is CrAlYN; The Cr content of the first transition layer gradually decreases as the thickness thereof increases.

2. The coating material for a milling cutter according to claim 1, characterized in that: The thickness of the primer layer is 0.1-0.3 μm, the thickness of the first transition layer is 0.5-1.5 μm, the thickness of the second transition layer is 0.5-1.5 μm, the thickness of the third transition layer is 60-120 nm, and the thickness of the working layer is 1.5-3 μm.

3. The coating material for a milling cutter according to claim 1, characterized in that: The atomic ratio of Cr to N in the first transition layer varies in the range of 3 to 1:

2.

4. The coating material for a milling cutter according to claim 1, characterized in that: In any of the CrAlYN, in terms of atomic percentage, Cr is 20-60%, Al is 2-10%, Y is 1-15%, and N is the balance.

5. The coating material for a milling cutter according to claim 4, characterized in that: The atomic percentage content of Y in the second transition layer is at least 3% less than the atomic percentage content of Y in the working layer.

6. The coating material for a milling cutter according to claim 1, characterized in that: In the CrAlMoN, in terms of atomic percentage, Cr is 20-60%, Al is 2-10%, Mo is 4-8%, and N is the balance.

7. A milling cutter, characterized in that: The invention is composed of a milling cutter base body and a coating material according to any one of claims 1 to 6 on the surface of the milling cutter base body.

8. Use of the milling cutter according to claim 7 in metal processing.

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