A coating material for a milling cutter and a preparation method thereof

Abstract

The present invention belongs to the technical field of plating materials, and relates to a plating material for a milling cutter and a preparation method thereof. The present invention provides a plating material for a milling cutter. The plating material is composed of a bottom layer, a first transition layer, a second transition layer, a third transition layer and a working layer from inside to outside on the surface of the milling cutter substrate; the bottom 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 content of Cr in the first transition layer gradually decreases as the thickness thereof increases. The present invention solves the technical problem of poor steady state of cutting force at a relatively high cutting speed.

Description

Technical Field

[0001] The present 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 speeds, high feed rates, high reliability, long life, high precision, and good milling controllability. The emergence of coated cutters has brought a major breakthrough in the milling performance of milling cutters. It combines the cutter body with a hard thin film surface layer. Since the substrate maintains good toughness and relatively high strength, and the hard thin film surface layer has high wear resistance and low friction coefficient, the performance of the milling cutter is greatly improved. At present, it is quite common to coat carbides and nitrides on the surfaces of most milling cutters (including high-speed steel milling cutters and cemented carbide milling cutters), and a considerable proportion of milling cutters need to be re-coated during regrinding after use.

[0003] General-purpose coatings are for obtaining equal and satisfactory machining effects in a wide range of applications. However, for specific application fields, such coatings can only be alternative solutions. For example, TA15 titanium alloy has a composition of T-6Al-2Zr-1Mo-1V and belongs to a high-aluminum equivalent near-α alloy. This alloy has medium room-temperature and high-temperature strengths, good thermal stability, and weldability, and is widely used in the manufacture of various types of aerospace structural parts. In the precision machining of TA15 titanium alloy on a machine tool, as the milling speed increases, the surface roughness gradually decreases. When the cutting speed is low, built-up edges and burrs are easily formed. The higher the cutting speed, the less plastic deformation occurs on the surface, and a smaller surface roughness can be obtained. For some general-purpose coatings, when used for the machining of TA15 titanium alloy, as the cutting force increases, the change in the dynamic cutting force becomes larger, and as the contact area between the tool and the workpiece increases, the change in the dynamic cutting force also increases, affecting the machining precision. In short, only coatings that truly meet the specific requirements of the tool and application conditions can achieve substantial specific application effects. Coatings have been regarded as an integral part of the tool, just like the geometry and substrate material, and should meet specific application conditions and be optimized. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problem that when the existing coatings are used for machining TA15 titanium alloy, at a relatively high cutting speed, the change in the dynamic cutting force is large and it is difficult to perform precision machining. In response to this, the present invention provides a plating material for a milling cutter and a preparation method thereof to meet this need in the art.

[0005] On the one hand, the present invention relates to a plating material for a milling cutter. The plating 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 substrate;

[0006] The underlayer 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;

[0007] In the first transition layer, the content of Cr gradually decreases as its thickness increases.

[0008] Furthermore, in the coating material for the milling cutter provided by the present invention, the thickness of the underlayer 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.

[0009] Furthermore, in the coating material for the milling cutter provided by the present invention, the atomic ratio range of Cr and N in the first transition layer is 3 - 1:2.

[0010] Furthermore, in the coating material for the milling cutter provided by the present invention, in any of the CrAlYN, by atomic percentage, Cr is 20 - 60%, Al is 2 - 10%, Y is 1 - 15%, and the balance is N.

[0011] Furthermore, in the coating material for the 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.

[0012] Furthermore, in the coating material for the 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 the balance is N.

[0013] On the other hand, the present invention relates to a milling cutter, which is composed of a milling cutter substrate and the coating material on the surface of the milling cutter substrate.

[0014] On the other hand, the present invention relates to the application of the milling cutter in metal processing.

[0015] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0016] 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 during high-speed cutting of existing coatings. The core technology lies in designing a coating with a multi-layer gradient structure, which consists of a Cr underlayer, 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. The performance is synergistically improved by optimizing the composition and thickness of each layer. The multi-layer structure of the coating gradually adjusts the hardness and toughness of the material through gradient design, reducing stress concentration between layers. The Cr underlayer enhances the bonding force between the substrate and the coating; in the CrN first transition layer, the Cr content decreases with the thickness, forming a composition gradient to optimize the interlayer matching; the Y element in CrAlYN refines the grains, improves the coating density, and inhibits crack propagation; the CrAlMoN third transition layer introduces the Mo element to enhance the high-temperature stability and anti-friction performance, reducing the accumulation of cutting heat. The Y content in the second transition layer is at least 3% less than that in the working layer. Utilizing the characteristic that the change in Y content in CrAlYN leads to changes in material properties, the supporting role of the intermediate layer is further strengthened, while the working layer ensures surface wear resistance by balancing the composition. Through the synergistic optimization of composition and structure, this coating significantly improves the stability of the milling cutter during high-speed cutting of TA15 titanium alloy. Experimental data show that compared with traditional AlTiN-coated milling cutters, the milling cutter of the present invention has significantly reduced fluctuations in cutting force under long cutting distances, demonstrating a substantial improvement in cutting force stability. At the same time, the introduction of the third transition layer further effectively delays the phenomenon of increasing dispersion of cutting force, extends the tool life, and improves the machining surface quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is a broken line graph of the cutting distance of milling cutter #1 relative to the average cutting force.

[0019] Figure 2 It is a broken line graph of the cutting distance of milling cutter #2 relative to the average cutting force.

[0020] Figure 3 It is a broken line graph of the cutting distance of milling cutter #3 relative to the average cutting force.

[0021] Figure 4 It is a broken line graph of the cutting distance of milling cutter #4 relative to the average cutting force.

[0022] Figure 5Line graph of the cutting distance of the #5 milling cutter relative to the average cutting force.

[0023] Figure 6 Line graph of the cutting distance of a commercially available coated milling cutter relative to the average cutting force. Detailed implementation manners

[0024] Next, the technical solutions of the present invention will be described in conjunction with the embodiments. However, the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are all conventional methods unless otherwise specified; the reagents and materials described, unless otherwise specified, can all be purchased on the market. The % in the following embodiments is the mass percentage content unless otherwise specified. The ratios in the following embodiments are mass ratios unless otherwise specified.

[0025] In the following embodiments, the workpiece to be processed used is TA15 titanium alloy, with the composition of Ti-6.5Al-2Zr-1Mo-1V, belonging to the α-type alloy. It is melted twice by a vacuum consumable furnace. The ingot is forged in the β region and then forged in the upper part of the α-β two-phase region. Its physical properties are as follows: the tensile strength σ b is 1134 MPa, the yield limit σ 0.2 is 943 MPa, the elastic modulus E is 134 GPa, the elongation δ5 is 13.2%, and the reduction of area ψ is 43.9%.

[0026] The following machining tests are carried out on a CNC vertical machining center, model VMC850, a CNC milling machine with a three-axis linear guideway. The spindle speed is 100 - 8000 rpm, the main motor power is 7.5 kW. During the machining process, emulsion is used for lubrication and cooling, and the rotation direction of the contact part between the milling cutter and the workpiece is the same as the workpiece feed direction.

[0027] In the following tests, the helix angle of the milling cutters used is 45°. When setting, the distance from the clamping point to the cutting point of the tool is kept at 40 mm, the milling depth a p is 1 mm, the milling width a e is 8 mm, the feed per tooth f z is 0.05 mm / z, and the milling speed v c is 40 m / min (the limit value of general milling cutters).

[0028] The 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 tool wear, breakage, tool durability, and the quality of the machined surface. In the following experiments, the milling force measuring device is a Swiss Kistler 9257B three-axis milling dynamometer, which is based on the machine tool table and is divided into the x-axis, y-axis, and z-axis. Among them, the y-axis is the feed direction of the tool, and the average milling force in the statistics is the average value of the milling forces on the x-axis, y-axis, and z-axis.

[0029] Embodiment

[0030] This embodiment provides a preparation process for a coating material for a milling cutter.

[0031] The milling cutter substrate is a tungsten-molybdenum series general high-speed steel with a composition of W6Mo5Cr4V2, which is a high-performance cutting tool material with excellent hardness, wear resistance, heat resistance, and machining performance. It is particularly suitable for application fields with high requirements for cutting speed, wear resistance, and heat resistance, such as metal processing, aerospace, etc.

[0032] The cleaned milling cutter substrate is loaded into the equipment fixture. First, it is bombarded and cleaned by argon plasma to clean the tool surface to improve the adhesion of the coating. Then, coating treatment is carried out. For each coating, targets of four components, Cr, Al, Y, and N (pure Cr target, pure Al target, pure Y target, and N2 gas) are used. When preparing the third transition layer, the Y target is replaced with a Mo target, and when preparing the working layer, the Mo target is replaced back with the Y target. Before sputtering, ultrasonic cleaning is carried out to remove impurities such as oil stains on the target surface and improve the surface quality of the coating. The mass purity of each target is ≥99.99%. The target is placed at the cathode, and the titanium substrate is placed at the anode. The sputtering power is 100 - 500 W. The composition content of each layer is controlled by changing the sputtering power of each target, and the thickness of each layer is controlled by changing the sputtering time.

[0033] Based on the above preparation process, a bottom layer, a first transition layer - 1, a first transition layer - 2, a first transition layer - 3, a second transition layer, a third transition layer, and a working layer are sequentially sputtered on the surface of the milling cutter substrate 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.

[0034] Table 1 Thickness of the coating material for the milling cutter

[0035]

[0036] Generally, in the coating materials for the milling cutter provided by the present invention (#1 - #3), the component content of each layer is calculated by atomic percentage, as shown in Table 2 specifically.

[0037] Table 2 Atomic percentage content of each layer component provided by the present invention

[0038]

[0039] And it satisfies that the content of Cr in the first transition layer - 1, the first transition layer - 2, and the first transition layer - 3 decreases 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.

[0040] Exemplarily, the preparation process of the coating material for the milling cutter shown in #1 is specifically as follows:

[0041] Step 1: Clean the milling cutter substrate, load it into the equipment fixture, first perform argon ion bombardment cleaning to clean the tool surface to improve the adhesion of the coating, and then perform coating treatment.

[0042] Step 2: The working gas is argon. Control the vacuum degree of the magnetron sputtering equipment to reach 1×10 -6 Pa and then start coating. Rotate the milling cutter substrate at a speed of 10 r / min. The distance between the sample and the target is 200 mm. Use a Cr target to deposit a bottom layer on the surface of the milling cutter substrate. The sputtering power of the Cr target is 460 W. After opening the Cr target baffle for 3 min, a 0.1 - μm bottom layer is formed on the surface of the milling cutter substrate, and the component of the obtained bottom layer is Cr.

[0043] Step 3: Close the argon gas, introduce nitrogen gas into the cavity, set the flow rate of nitrogen gas to 500 sccm. After opening the Cr target baffle for 5 min, a 0.2 - μm first transition layer - 1 is formed, and the component of the obtained first transition layer - 1 is CrN.

[0044] Step 4: Keep the nitrogen gas, adjust the sputtering power of the Cr target to 320 W. After opening the Cr target baffle for 5 min, a 0.2 - μm first transition layer - 2 is formed, and the component of the obtained first transition layer - 2 is CrN.

[0045] Step 5: Keep the nitrogen gas, adjust the sputtering power of the Cr target to 200 W. After opening the Cr target baffle for 3 min, a 0.1 - μm first transition layer - 3 is formed, and the component of the obtained first transition layer - 3 is CrN.

[0046] Step 6: Keep the nitrogen gas, 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. After opening the baffles of the Cr target, Al target, and Y target simultaneously for 15 min, a 0.5 - μm second transition layer is formed, and the component of the obtained second transition layer is CrAlYN.

[0047] Step 7: Maintain 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. After opening the shutters of the Cr target, Al target, and Mo target simultaneously for 1.5 min, a 60-nm third transition layer is formed, and the composition of the obtained third transition layer is CrAlMoN.

[0048] Step 8: Maintain 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. After opening the shutters of the Cr target, Al target, and Y target simultaneously for 60 min, a 1.5-μm working layer is formed, and the composition of the obtained working layer is CrAlYN.

[0049] In fact, the elemental contents of the respective coatings of the coating material prepared for the milling cutter are shown in Tables 3 to 5.

[0050] Table 3 Atomic percentage contents of the components in each layer of #1

[0051]

[0052] Table 4 Atomic percentage contents of the components in each layer of #2

[0053]

[0054] Table 5 Atomic percentage contents of the components in each layer of #3

[0055]

[0056] Table 6 Atomic percentage contents of the components in each layer of #4

[0057]

[0058] Table 7 Atomic percentage contents of the components in each layer of #5

[0059]

[0060] In addition, by comparison, the commercially available coated milling cutter is a solid carbide four-edge end mill, which has a nano-coating with a composition of AlTiN.

[0061] The change of the average cutting force with respect to the cutting distance from 0 to 8000 mm is measured, and a regression equation is constructed. Through R 2 to judge the stability of its cutting force, and the test results of #1 to #5 correspond Figures 1 - 5 , Figure 6 to the test results of the commercially available coated milling cutter, and the regression equation is shown in Table 8.

[0062] Table 8 Regression equation of cutting distance with respect to average cutting force

[0063]

[0064] As can be seen from Table 8, by adjusting the gradient change of the Cr content in the first transition layer with the thickness, the present invention can effectively improve the stability of the milling cutter during high-speed cutting of TA15 titanium alloy. Further, through the setting of the CrAlMoN thin layer and the difference in the Y content between the second transition layer and the working layer, the stability of the milling cutter during high-speed cutting of TA15 titanium alloy is further improved. Among them, #4 does not have a third transition layer, and obvious increase in the dispersion of cutting force occurs when the cutting distance is about 7000 mm. #5 adopts similar Y content in the second transition layer and the working layer, and obvious increase in the dispersion of cutting force occurs when the cutting distance is about 5000 mm. The commercially available coated milling cutter is completely inapplicable to high-speed cutting under long cutting distances, and obvious increase in the dispersion of cutting force occurs when the cutting distance is about 3000 mm.

[0065] As described above, the basic principle, main features and advantages of the present invention are preferably described. The above embodiments and the description are only for describing the preferred embodiments of the present invention. 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 those of ordinary skill in the art to the technical solutions of the present invention shall 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; 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; The atomic ratio of Cr to N in the first transition layer varies from 3 to 1:2; 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; 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; 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.

2. A milling cutter, characterized in that: The invention is composed of a milling cutter base body and the coating material according to claim 1 on the surface of the milling cutter base body.

3. Use of the milling cutter according to claim 2 in metal processing.

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