Preparation process of PVD (Physical Vapor Deposition) coating for cutter

Abstract

The invention relates to the technical field of tool surface treatment, and discloses a preparation process of a PVD coating for a tool, and the process comprises the steps of tool matrix pretreatment, coating deposition equipment debugging, matrix plasma cleaning, transition layer deposition, nano multilayer coating deposition and post-treatment. The coating prepared through the method is high in binding force with a matrix, the nanometer hardness can reach 35-40 GPa, the friction coefficient is smaller than or equal to 0.15, and the oxidation resistance is excellent at the high temperature of 900 DEG C; the method is simple in process, wide in process universality and suitable for various matrixes such as hard alloy, high-speed steel and metal ceramic, the service life of the prepared cutter is remarkably prolonged in the cutting scene of difficult-to-machine materials, the service life is greatly prolonged compared with a traditional coated cutter, and the method is suitable for industrial batch production.

Description

Technical Field

[0001] This invention relates to the field of cutting tool surface treatment technology, specifically to a process for preparing a PVD coating for cutting tools. Background Technology

[0002] Physical vapor deposition (PVD) technology has become one of the core technologies for tool surface modification due to its ability to prepare thin film coatings with high hardness and low friction coefficient. Currently commonly used PVD coatings include single or composite coatings such as TiN, TiAlN, and CrAlN. Among them, TiAlN coatings are widely used in the cutting tool field because they have both high hardness and oxidation resistance. However, traditional TiAlN coatings are prone to oxidation failure in high-temperature (>800℃) cutting environments, and the adhesion between the coating and the substrate is insufficient, which limits the tool life.

[0003] Existing multilayer PVD coating processes mostly employ alternating deposition of single nitride coatings. While this can improve some performance, it suffers from problems such as weak interfacial bonding and uneven grain size. Furthermore, incomplete substrate cleaning and low matching of deposition parameters in traditional processes further exacerbate coating peeling, wear, and other failure phenomena. In addition, existing processes are often designed for specific substrate materials, lacking versatility and failing to meet the personalized performance requirements of cutting tools made from different materials.

[0004] Therefore, developing a PVD coating preparation process for cutting tools that combines high hardness, strong adhesion, and excellent high-temperature stability to achieve synergistic improvement in coating performance has become an urgent technical problem to be solved in the field of cutting tool surface treatment. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a process for preparing PVD coatings for cutting tools, which significantly improves the wear resistance, oxidation resistance and service life of cutting tools.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a process for preparing a PVD coating for cutting tools, wherein...

[0007] (1) Pretreatment of the tool substrate: mechanical grinding, ultrasonic cleaning, sandblasting activation and secondary drying are performed in sequence;

[0008] (2) Coating deposition equipment debugging: Fix the pretreated tool substrate to the PVD equipment fixture and evacuate to 5.0×10 -5 -1.0×10 -4 MPa;

[0009] (3) Substrate plasma cleaning: Argon gas is introduced and argon ions are used to bombard the substrate surface for 40-60 minutes, while heating to 400-450℃ to further remove residual pollutants and adsorption layers on the surface, activate the atomic activity of the substrate surface, and enhance the film-substrate bonding force.

[0010] (4) Transition layer deposition: N2 / Ar mixed gas is introduced to deposit a TiAlCrN transition layer with a thickness of 0.5-1.0 μm;

[0011] (5) Nanoscale multilayer coating deposition: TiAlCrN sublayer and TiSiN sublayer are deposited alternately to form 15-20 deposition cycles with a total thickness of 1.5-3.0 μm;

[0012] (6) Post-treatment: Cool the furnace to below 150°C, remove the vacuum, and then passivate the cutting edge.

[0013] Further, in step (1), mechanical grinding is performed by grinding step by step with 400-800 mesh wet sandpaper, and the surface roughness of the substrate after polishing is Ra≤0.2μm; ultrasonic cleaning is performed by sequentially using acetone and ethanol solutions, with a cleaning temperature of 40-50℃ and each cleaning lasting 15-20 minutes.

[0014] Furthermore, in step (1), the sandblasting activation uses Al2O3 medium, the sandblasting pressure is 0.3-0.5MPa, the sandblasting distance is 10-15cm, and the sandblasting time is 30-60s.

[0015] Furthermore, in step (3), the argon flow rate is 20-30 sccm, and the deposition chamber pressure is 1.0 × 10⁻⁶. -2 -5.0×10 - 2 MPa, substrate negative bias voltage -800~-1000V.

[0016] Furthermore, in step (4), the N2 / Ar mixed gas volume ratio is 1:1, the total flow rate is 30-40 sccm, and the deposition chamber pressure is 2.0 × 10⁻⁶. -3 -5.0×10 -3 MPa; TiAlCr alloy target current 60-80A, substrate negative bias voltage -200~-300V, deposition temperature 400-450℃, deposition time 10-15min.

[0017] Further, in step (5), the TiAlCrN sublayer deposition parameters are: target current 60-80A, negative bias voltage -150~-250V, deposition time 1-2min, and thickness 50-80nm; the TiSiN sublayer deposition parameters are: target current 50-70A, negative bias voltage -150~-250V, deposition time 0.5-1min, and thickness 20-40nm.

[0018] Furthermore, in step (6), the cooling rate is controlled at 5-10℃ / min, and after cooling to below 150℃, inert gas is introduced to break the vacuum.

[0019] Furthermore, the tool substrate is made of cemented carbide, high-speed steel, or cermet.

[0020] Furthermore, the tool surface is sequentially coated with a TiAlCrN transition layer and a TiAlCrN / TiSiN nano multilayer coating, with a total coating thickness of 2.0-4.0 μm, a nano hardness of 35-40 GPa, and a film-substrate adhesion of ≥80 MPa.

[0021] The tool substrate surface is progressively ground using 400-800 grit wet abrasive paper to remove surface oxide scale, scratches, and machining defects until the surface roughness Ra ≤ 0.2 μm. Subsequently, diamond polishing paste is used for fine polishing to obtain a smooth and flat substrate surface. The polished tool substrate is then ultrasonically cleaned sequentially in acetone and ethanol solutions for 15-20 minutes each time, at a temperature controlled at 40-50℃, to remove surface oil and residual impurities. It is then rinsed 3-5 times with deionized water and placed in a vacuum drying oven at 80-100℃ for 2-3 hours to ensure no moisture residue remains on the substrate surface. The dried substrate surface is sandblasted using Al2O3 as the blasting medium. The blasting pressure is 0.3-0.5 MPa, the blasting distance is 10-15 cm, and the blasting time is 30-60 s. This creates a uniform rough surface on the substrate, improving the mechanical adhesion between the coating and the substrate. After sandblasting, compressed air is used to blow away any residual sand particles on the surface. The substrate is then ultrasonically cleaned in ethanol for 5-10 min and dried for later use.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] The TiAlCrN / TiSiN nano-multilayer coating prepared by this invention forms a nanoscale interlayer structure by alternately depositing nitride sublayers of different compositions. This refines the coating grain size to 20-50 nm, achieving a nano-hardness of 35-40 GPa and a friction coefficient below 0.15. The introduction of the TiSiN sublayer significantly enhances the coating's high-temperature oxidation resistance, maintaining good structural stability even at 900℃, effectively solving the problem of high-temperature oxidation failure in traditional coatings. By optimizing the substrate pretreatment process and combining it with the design of the TiAlCrN transition layer, the adhesion between the coating and the substrate can reach over 80 MPa, far exceeding that of traditional PVD coatings, effectively preventing coating peeling during cutting and extending tool life. This process is adaptable to various tool substrates such as cemented carbide, high-speed steel, and cermet. By fine-tuning the deposition parameters, it can meet the performance requirements of different cutting scenarios, making it widely applicable and highly practical. The use of multi-arc ion plating and magnetron sputtering composite technology results in a coating with small thickness uniformity error, dense grain structure, and no obvious defects, making it suitable for industrial mass production. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1 (Preparation of PVD coating for cemented carbide cutting tools)

[0026] 1. Substrate pretreatment: WC-Co cemented carbide cutting tools (Co content 10%) were selected as the substrate and ground sequentially with 400-grit, 600-grit, and 800-grit wet sandpaper until Ra=0.15μm. The substrate was ultrasonically cleaned in acetone and ethanol for 15 min each (45℃), rinsed with deionized water, and vacuum dried at 80℃ for 2 h. The substrate was then sandblasted with Al2O3 (pressure 0.4MPa, distance 12cm, time 45s), purged, ultrasonically cleaned with ethanol for 5 min, and dried for later use.

[0027] 2. Equipment Debugging: Fix the cutting tool on the fixture, with a 30mm gap between the substrate and the target; close the deposition chamber and evacuate to 8.0×10⁻⁶. -5 MPa.

[0028] 3. Plasma cleaning: Argon gas is introduced (flow rate 25 sccm), pressure 3.0 × 10⁻⁶. -2 MPa; apply -900V negative bias voltage, bombard with argon ions for 50 min, and heat the substrate to 420℃.

[0029] 4. Transition layer deposition: Introduce a N2 / Ar mixed gas (1:1, total flow rate 35 sccm) at a pressure of 3.0 × 10⁻⁶. -3 MPa; Start TiAlCr target (current 70A), substrate negative bias -250V, deposit at 420℃ for 12min to form a 0.8μm thick TiAlCrN transition layer.

[0030] 5. Multilayer coating deposition: TiAlCrN / TiSiN sublayers are deposited alternately. The TiAlCrN sublayer is deposited for 1.5 min (thickness 60 nm) and the TiSiN sublayer is deposited for 0.8 min (thickness 30 nm). This process is repeated for 18 cycles to form a multilayer coating with a total thickness of 2.5 μm.

[0031] 6. Post-processing: Cool to 120℃ in the furnace (cooling rate 8℃ / min), remove from the furnace after the vacuum is broken, and passivate the cutting edge to obtain the finished product.

[0032] Finished product testing: The coating has a nano-hardness of 38 GPa, a friction coefficient of 0.13, and a film-substrate adhesion of 85 MPa. High-temperature oxidation resistance test shows that after holding at 900℃ for 2 hours, the oxidation weight gain rate is 0.12%, with no obvious oxide impurities, and no surface cracking or peeling. In the cutting test of titanium alloy TC4 (cutting speed 200 m / min, feed rate 0.2 mm / r, cutting depth 0.3 mm), the tool life is 120 min, which is 8 times higher than that of traditional TiAlN coated tools (15 min).

[0033] Example 2 (Preparation of PVD coating for high-speed steel cutting tools)

[0034] 1. Matrix pretreatment: Select W6Mo5Cr4V2 high-speed steel tools, grind and polish to Ra=0.18μm; ultrasonically clean with acetone and ethanol for 20min (40℃), vacuum dry at 100℃ for 3h; sandblast with Al2O3 (pressure 0.3MPa, distance 10cm, time 30s), blow-dry and ultrasonically clean with ethanol for 8min, and dry for later use.

[0035] 2. Equipment debugging: With a substrate-target spacing of 25mm, evacuate to a vacuum level of 5.0×10⁻⁶. -5 MPa.

[0036] 3. Plasma cleaning: Argon flow rate 20 sccm, pressure 1.0 × 10⁻⁶ -2 Bombardment with MPa; -800V negative bias for 40 minutes, and heating the substrate to 400℃.

[0037] 4. Transition layer deposition: N2 / Ar mixed gas (1:1, flow rate 30 sccm), gas pressure 2.0 × 10⁻⁶ -3MPa; TiAlCr target current 60A, negative bias voltage -200V, 400℃ deposition for 10min to form a 0.5μm transition layer.

[0038] 5. Multilayer coating deposition: Alternate deposition of TiAlCrN (1 min, 50 nm) / TiSiN (0.5 min, 20 nm) for 15 cycles, with a total thickness of 1.5 μm.

[0039] 6. Post-treatment: Cool to 100℃ in the furnace (cooling rate 5℃ / min) and passivate the cutting edge.

[0040] Finished product testing: The coating has a nano-hardness of 35 GPa, a friction coefficient of 0.15, and a film-substrate adhesion of 80 MPa. High-temperature oxidation resistance test shows that after holding at 900℃ for 2 hours, the oxidation weight gain rate is 0.18%, the phase structure is stable, and the surface morphology is intact. In the cutting test of high-strength steel 40Cr (cutting speed 180 m / min, feed rate 0.15 mm / r, cutting depth 0.2 mm), the tool life is 150 min, which is 10 times longer than that of uncoated high-speed steel tools (15 min).

[0041] Example 3 (Preparation of PVD coating for cermet cutting tools)

[0042] 1. Substrate pretreatment: Ti(C,N)-Ni-Co cermet cutting tools were selected as the substrate and ground sequentially with 400-mesh, 600-mesh, and 800-mesh wet abrasive paper until Ra=0.16μm. The substrate was ultrasonically cleaned in acetone and ethanol for 18 min each (48℃), rinsed 4 times with deionized water, and then vacuum dried at 90℃ for 2.5 h. The substrate was then sandblasted with Al2O3 (pressure 0.45MPa, distance 14cm, time 50s), purged, ultrasonically cleaned with ethanol for 7 min, and dried for later use.

[0043] 2. Equipment debugging: Fix the tool on the fixture, with a distance of 32mm between the substrate and the target; close the deposition chamber and evacuate to 9.0×10⁻⁶. -5 MPa.

[0044] 3. Plasma cleaning: Argon gas is introduced (flow rate 28 sccm), pressure 4.0 × 10⁻⁶. -2 MPa; apply -950V negative bias voltage, bombard with argon ions for 55 min, and heat the substrate to 440℃.

[0045] 4. Transition layer deposition: A N2 / Ar mixed gas (1:1, total flow rate 38 sccm) was introduced at a pressure of 4.0 × 10⁻⁶. -3 MPa; Start TiAlCr target (current 75A), substrate negative bias -280V, deposit at 440℃ for 14min to form a 0.9μm thick TiAlCrN transition layer.

[0046] 5. Multilayer coating deposition: TiAlCrN / TiSiN sublayers are deposited alternately. The TiAlCrN sublayer is deposited for 1.8 min (75 nm thick) and the TiSiN sublayer is deposited for 0.9 min (35 nm thick). This process is repeated for 19 cycles to form a multilayer coating with a total thickness of 2.9 μm.

[0047] 6. Post-processing: Cool to 130℃ in the furnace (cooling rate 9℃ / min), remove from the furnace after the vacuum is broken, and passivate the cutting edge to obtain the finished product.

[0048] Finished product testing: The coating has a nano-hardness of 39 GPa, a friction coefficient of 0.12, and a film-substrate adhesion of 88 MPa. High-temperature oxidation resistance test shows that after holding at 900℃ for 2 hours, the oxidation weight gain rate is 0.10%, indicating the best oxidation resistance performance. In the cutting test of the high-temperature alloy Inconel 718 (cutting speed 180 m / min, feed rate 0.18 mm / r, cutting depth 0.2 mm), the tool life is 90 min, which is 9 times better than the traditional TiAlN coated tool (10 min).

[0049] Comparative Example 1 (Preparation of conventional TiAlN coated cutting tools)

[0050] 1. Substrate pretreatment: Select the same WC-Co cemented carbide tool (Co content 10%) as in Example 1, grind and polish to Ra=0.2μm, ultrasonically clean with acetone for 15min, dry at 80℃ for 2h, and do not perform sandblasting activation treatment.

[0051] 2. Equipment Debugging: A single multi-arc ion plating PVD equipment was used, equipped with a TiAl alloy target (Ti:Al=70:30, mass ratio), with a substrate-target distance of 30mm, and a vacuum of 8.0×10⁻⁶. -5 MPa.

[0052] 3. Plasma cleaning: Argon gas is introduced (flow rate 25 sccm), pressure 3.0 × 10⁻⁶. -2 Bombardment with MPa and -900V negative bias for 30 minutes, followed by heating the substrate to 420℃.

[0053] 4. Coating deposition: A mixture of nitrogen and argon gas (N2:Ar=2:1, volume ratio) is introduced at a flow rate of 35 sccm and a pressure of 3.0 × 10⁻⁶. -3 MPa; Start TiAl target (current 70A), substrate negative bias -250V, deposit at 420℃ for 30min to form a 2.5μm thick single TiAlN coating.

[0054] 5. Post-processing: Cool in the furnace to below 150℃ at a cooling rate of 15℃ / min, remove and passivate the cutting edge to obtain the finished product.

[0055] Finished product testing: The coating has a nano-hardness of 28 GPa, a friction coefficient of 0.22, and a film-substrate adhesion of 55 MPa. High-temperature oxidation resistance test showed that after holding at 900℃ for 2 hours, the oxidation weight gain rate was 1.85%, and Al2O3 and TiO2 oxide phases were detected, with obvious oxidation peeling marks on the surface. Under the same titanium alloy TC4 cutting test conditions (cutting speed 200 m / min, feed rate 0.2 mm / r, cutting depth 0.3 mm), the tool life was only 15 min, which is 1 / 8 of the finished product of Example 1 (120 min).

[0056] Nanohardness test: The test was conducted using a nanoindenter (model: Agilent G200). The test load was 50mN and the holding time was 10s. Ten test points were selected for each sample. The average value after removing the maximum and minimum values ​​was taken as the nanohardness value of the coating. The test standard refers to GB / T 18449.4-2022.

[0057] Friction coefficient test: The test was conducted using a ball-and-disc friction and wear tester (model: UMT-3). The friction pair consisted of Si3N4 ceramic balls (6mm in diameter). The test load was 5N, the sliding speed was 0.2m / s, the sliding distance was 1000m, the test temperature was 25℃, and the ambient humidity was 50%±5%. The real-time friction coefficient was recorded by the software built into the tester, and the average value during the stable phase of the test was taken as the final friction coefficient.

[0058] Membrane-substrate adhesion test: The test was conducted using a scratch tester (model: Revetest RST3), and the test standard was in accordance with GB / T 19396-2025.

[0059] High-temperature oxidation resistance test: The coating sample is placed in a muffle furnace and kept at 900℃ for 2 hours. After naturally cooling to room temperature, the oxidation weight gain rate of the coating is measured as (mass after oxidation - mass before oxidation) / mass before oxidation × 100%. An oxidation weight gain rate ≤ 0.5% indicates that the oxidation resistance performance is qualified.

[0060] Tool cutting life test: Select the corresponding machining materials (titanium alloy TC4, high-strength steel 40Cr, high-temperature alloy Inconel 718), and conduct dry cutting tests on CNC lathes. Set uniform cutting parameters (cutting speed, feed rate, and depth of cut are matched to the corresponding materials respectively). Cut continuously until the tool edge shows obvious wear (flank wear VB=0.2mm) or the coating peels off. Record the cutting time. The cutting time is used to characterize the tool life. Each sample is tested 3 times, and the average value is taken as the final result.

[0061] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for preparing a PVD coating for cutting tools, characterized in that, The (1) Pretreatment of the tool substrate: mechanical grinding, ultrasonic cleaning, sandblasting activation and secondary drying are performed in sequence; (2) Coating deposition equipment debugging: Fix the pretreated tool substrate to the PVD equipment fixture and evacuate to 5.0×10 -5 -1.0×10 -4 MPa; (3) Plasma cleaning of substrate: Argon gas is introduced and argon ions are used to bombard the substrate surface for 40-60 minutes, while heating to 400-450℃. (4) Transition layer deposition: N2 / Ar mixed gas is introduced to deposit a TiAlCrN transition layer with a thickness of 0.5-1.0 μm; (5) Nanoscale multilayer coating deposition: TiAlCrN sublayer and TiSiN sublayer are deposited alternately to form 15-20 deposition cycles with a total thickness of 1.5-3.0 μm; (6) Post-treatment: Cool the furnace to below 150°C, remove the vacuum, and then passivate the cutting edge.

2. The preparation process of the PVD coating for cutting tools according to claim 1, characterized in that, In step (1), mechanical grinding is performed by grinding with 400-800 mesh wet sandpaper in stages, and the surface roughness Ra of the substrate after polishing is ≤0.2μm; ultrasonic cleaning is performed by acetone and ethanol solutions in sequence, with a cleaning temperature of 40-50℃ and each cleaning lasting 15-20 minutes.

3. The preparation process of the PVD coating for cutting tools according to claim 1, characterized in that, In step (1), Al2O3 medium is used for sandblasting activation, the sandblasting pressure is 0.3-0.5MPa, the sandblasting distance is 10-15cm, and the sandblasting time is 30-60s.

4. The preparation process of the PVD coating for cutting tools according to claim 1, characterized in that, In step (3), the argon flow rate is 20-30 sccm, and the deposition chamber pressure is 1.0 × 10⁻⁶. -2 -5.0×10 -2 MPa, substrate negative bias voltage -800~-1000V.

5. The preparation process of the PVD coating for cutting tools according to claim 1, characterized in that, In step (4), the N2 / Ar mixed gas volume ratio is 1:1, the total flow rate is 30-40 sccm, and the deposition chamber pressure is 2.0 × 10⁻⁶. -3 -5.0×10 -3 MPa; TiAlCr alloy target current 60-80A, substrate negative bias voltage -200~-300V, deposition temperature 400-450℃, deposition time 10-15min.

6. The preparation process of the PVD coating for cutting tools according to claim 1, characterized in that, In step (5), the TiAlCrN sublayer deposition parameters are: target current 60-80A, negative bias voltage -150~-250V, deposition time 1-2min, and thickness 50-80nm; the TiSiN sublayer deposition parameters are: target current 50-70A, negative bias voltage -150~-250V, deposition time 0.5-1min, and thickness 20-40nm.

7. The preparation process of the PVD coating for cutting tools according to claim 1, characterized in that, In step (6), the cooling rate is controlled at 5-10℃ / min, and after cooling to below 150℃, inert gas is introduced to break the vacuum.

8. A process for preparing a PVD coating for cutting tools as described in any one of claims 1-7, characterized in that, The tool substrate is made of cemented carbide, high-speed steel, or cermet.

9. A coated cutting tool prepared using the process described in any one of claims 1-8, characterized in that, The tool surface is sequentially coated with a TiAlCrN transition layer and a TiAlCrN / TiSiN nano multilayer coating, with a total coating thickness of 2.0-4.0μm, a nano hardness of 35-40GPa, and a film-substrate adhesion of ≥80MPa.