Super-thick amorphous carbon coating plated on lead screw raceway and preparation method of super-thick amorphous carbon coating

Abstract

The invention discloses a super-thick amorphous carbon coating plated on a lead screw raceway and a preparation method of the super-thick amorphous carbon coating. The super-thick amorphous carbon plating layer is a laminated plating layer and comprises a chromium bottom layer, a carbon-chromium binary transition layer and an amorphous carbon upper cover layer which are sequentially plated on the lead screw, and the preparation method of the super-thick amorphous carbon plating layer comprises the following steps: carrying out argon plasma etching on the lead screw containing a raceway groove; depositing a chromium bottom layer by adopting multi-arc evaporation; depositing a carbon-chromium binary transition layer by adopting multi-arc evaporation; and finally, adopting magnetron sputtering-multi-arc evaporation combined deposition to obtain an amorphous carbon upper cover layer with the thickness of 15-30 microns. The thickness of the super-thick amorphous carbon coating reaches 20-35 microns, the super-thick amorphous carbon coating has excellent bearing capacity and antifriction and wear resistance, the response speed and precision of the lead screw can be greatly improved, and the service life of the lead screw can be greatly prolonged.

Description

Technical Field

[0001] The present invention relates to the field of depositing hard coatings on the surface of metal materials, and particularly to an ultra-thick amorphous carbon coating plated on a lead screw raceway and a preparation method thereof. Background Art

[0002] A lead screw is the most commonly used transmission component in machine tools and precision machinery. Its main function is to convert rotational motion into linear motion, or convert torque into axial reciprocating force, and at the same time has the characteristics of high precision, reversibility and high efficiency. Therefore, the lead screw is a key component that determines the response speed and positioning accuracy of high-end data machine tools and industrial robots. During the working process of the lead screw, due to long-term and high-frequency load reciprocation, as well as rapid advancement under high load, it is easy to cause raceway deformation, raceway and ball wear, affecting the positioning accuracy. Based on its performance requirements of high speed, high precision and long life, it is required that the lead screw raceway groove has high precision, high surface finish, high stiffness, high hardness, high wear resistance and low friction coefficient. Currently, the main methods for lead screw strengthening include surface heat treatment (such as rapid induction hardening), electroplating hard chromium and electroless nickel plating / low-temperature black chromium plating processes, etc.

[0003] With the development of high-end equipment technology, higher requirements are put forward for the accuracy and life of lead screws. Considering deformation and failure mechanisms such as heavy load and particle wear, high-performance ball screws use more wear-resistant ceramic balls, thus putting forward higher requirements for the hardness and wear resistance of the raceway. Vacuum deposition of hard coatings is widely used for surface wear protection of metal workpieces. Such as TiN coatings applied to injection molding machine screws, CrAlN coatings applied to stamping dies, TiAlN coatings and amorphous carbon coatings (or diamond-like coatings) applied to cutting tools, etc. The amorphous carbon coating with high hardness and low friction coefficient is an ideal surface strengthening coating for high-performance ball screws. However, due to the large internal stress in the amorphous carbon coating, the thickness of the amorphous carbon coating prepared by vacuum coating technology is generally less than 5μm, and the load-bearing capacity is poor, which cannot meet the performance requirements of large thickness and high load-bearing capacity of the high-performance lead screw coating. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultra-thick amorphous carbon coating that can be effectively and uniformly plated on a lead screw raceway and a preparation method thereof. The ultra-thick amorphous carbon coating has excellent load-bearing capacity and anti-friction and wear resistance, and can greatly improve the response speed, accuracy and service life of the lead screw.

[0005] The technical solution adopted by the present invention is as follows: In order to improve the load-bearing capacity of the coating, the ultra-thick amorphous carbon coating plated on the lead screw raceway is a laminated coating, which includes a chromium bottom layer, a carbon-chromium binary transition layer and an amorphous carbon top layer sequentially plated on the lead screw. The total thickness of the laminated coating is 20 - 35μm, wherein the thickness of the amorphous carbon top layer is 15 - 30μm.

[0006] Furthermore, the amorphous carbon top layer is formed by alternately overlapping a magnetron sputtered carbon film sub-layer and a multi-arc carbon film sub-layer.

[0007] Furthermore, the thickness of the chromium bottom layer is 2 μm, and the thickness of the carbon-chromium binary transition layer is 3 μm.

[0008] Furthermore, the material of the lead screw is iron-based metal.

[0009] The deposition sequence of the ultra-thick amorphous carbon coating deposited on the lead screw raceway is as follows: first, the lead screw with raceway grooves is etched with argon plasma, then a 2-μm-thick chromium bottom layer is deposited by multi-arc evaporation, then a 3-μm-thick carbon-chromium binary transition layer is deposited by multi-arc evaporation, and finally a 15 - 30-μm-thick amorphous carbon top layer is deposited by a combination of magnetron sputtering and multi-arc evaporation.

[0010] Furthermore, the deposition chamber of the magnetron sputtering - multi-arc evaporation combined deposition coating equipment used in the present invention is as Figure 1 shown. The magnetron sputtering carbon target, multi-arc carbon target, and multi-arc chromium target are arranged in the Figure 1 spatial positions shown, so that the thickness of the amorphous carbon top layer at various positions on the side wall of the raceway groove reaches 15 - 30 μm. Specifically, the arrangement of each target is as follows: the center position of the coating chamber of the coating equipment is a rotatable workpiece holder for placing the substrate, and the inner wall of the chamber is sequentially arranged with target positions numbered 1 - 8 at intervals in a circular arrangement. The 1st target position is one planar rectangular magnetron sputtering carbon target. The 2nd target position is three multi-arc carbon targets with the normal of the target surface tilted upward horizontally. The 3rd target position is three multi-arc chromium targets with the normal of the target surface tilted upward horizontally. The 4th target position is three multi-arc carbon targets with the normal of the target surface tilted downward horizontally. The 5th target position is one planar rectangular magnetron sputtering carbon target. The 6th target position is three multi-arc carbon targets with the normal of the target surface tilted upward horizontally. The 7th target position is three multi-arc chromium targets with the normal of the target surface tilted downward horizontally. The 8th target position is three multi-arc carbon targets with the normal of the target surface tilted downward horizontally. Among them, the 2nd, 3rd, 4th, 6th, 7th, and 8th target positions are all arranged in a row of three types according to the distribution of the inner wall of the chamber.

[0011] The present invention provides a method for preparing an ultra-thick amorphous carbon coating deposited on a lead screw raceway, including the following steps: 1) Pretreat the lead screw to make it clean and dry; 2) Clamp the clean lead screw on the sample workpiece holder and drive the workpiece holder and the lead screw to rotate at a constant speed; 3) Start the magnetron sputtering - multi - arc evaporation combined deposition coating equipment, and deposit an ultra - thick amorphous carbon coating according to the following technological process: A) Sequentially, ① evacuate the coating chamber of the coating equipment to 2×10 -3 ~2.1×10 -3 Pa; ② introduce and maintain argon at 300 - 330 sccm; ③ turn on the bias voltage of - 1000 ± 50 V and maintain it for 15 - 20 min; ④ lower the bias voltage to - 600 ± 50 V and maintain it for 15 - 20 min; B) Lower the bias voltage to - 150 ± 10 V. At the same time, start 3 multi - arc chromium targets with the target normal inclined upward horizontally and 3 multi - arc chromium targets with the target normal inclined downward horizontally, and make the current of each chromium target be 50 ± 5 A, and work for 20 - 25 min (the next step C starts only after working for 20 - 25 min in this step, and the chromium targets described in B still continue to work when C is working); C) Start 6 multi - arc carbon targets with the target normal inclined upward horizontally and 6 multi - arc carbon targets with the target normal inclined downward horizontally, make the starting current of each multi - arc carbon target be 30 ± 3 A, and within 20 min, linearly increase the current of each multi - arc carbon target to 90 ± 5 A; D) Simultaneously with step C, start 2 rectangular magnetron sputtering carbon targets, make the starting power of each magnetron sputtering carbon target be 600 ± 50 W, and within 20 min, linearly increase the power of each magnetron sputtering carbon target to 2600 ± 100 W; E) Turn off 6 multi - arc chromium targets, and make each multi - arc carbon target and each magnetron sputtering carbon target continue to work for 5 - 10 h in the current and power states they finally reach; 4) Shut down the coating instrument and take out the coated lead screw.

[0012] The beneficial effects of the present invention are as follows: The present invention uniformly deposits a laminated coating with a thickness of 20 - 35 μm at the friction and load - bearing positions of the lead screw raceway groove, including: a chromium bottom layer with a thickness of 2 μm, a carbon - chromium binary transition layer with a thickness of 3 μm, and an amorphous carbon top layer with a thickness of 15 - 30 μm. Among them, the amorphous carbon top layer is prepared by combined deposition of magnetron sputtering carbon targets and multi - arc carbon targets as Figure 1 shown. The sp 2 content in the magnetron sputtered carbon film is relatively high and the internal stress is relatively small; the sp 3 content in the multi - arc carbon film is relatively high and the internal stress is relatively large. The amorphous carbon top layer with a thickness of 15 - 30 μm is formed by alternately overlapping magnetron sputtered carbon film sub - layers and multi - arc carbon film sub - layers. Among them, the thickness of the magnetron sputtered carbon film sub - layer is relatively small, and the thickness of the multi - arc carbon film sub - layer is relatively large. Since the magnetron sputtering carbon targets and multi - arc carbon targets are arranged adjacent to each other, there is a mixed co - deposition area between the magnetron sputtered carbon film sub - layer and the multi - arc carbon film sub - layer. sp3 The amorphous carbon coating with a single component composed of the overlapping of "high / low / high... low / high" content takes into account high deposition efficiency, high hardness, low stress, and large thickness, solving the problem that conventional coating technologies cannot deposit amorphous carbon coatings with large thickness. The formed ultra-thick amorphous carbon coating has excellent bearing capacity and anti-friction and wear resistance, which can greatly improve the response speed, accuracy, and service life of the lead screw. Brief Description of the Drawings

[0013] Figure 1 It is the vacuum chamber structure of a magnetron sputtering - multi-arc evaporation combined deposition instrument; Figure 1 -(a) is the top view of the vacuum chamber, Figure 1 -(b) is the side view expansion diagram of the vacuum chamber wall; Among them, position 1 is a planar rectangular magnetron sputtering carbon target, position 2 is three multi-arc carbon targets with the normal direction of the target surface facing 45° upward horizontally, position 3 is three multi-arc chromium targets with the normal direction of the target surface facing 45° upward horizontally, position 4 is three multi-arc carbon targets with the normal direction of the target surface facing 45° downward horizontally, position 5 is a planar rectangular magnetron sputtering carbon target, position 6 is three multi-arc carbon targets with the normal direction of the target surface facing 45° upward horizontally, position 7 is three multi-arc chromium targets with the normal direction of the target surface facing 45° downward horizontally, position 8 is three multi-arc carbon targets with the normal direction of the target surface facing 45° downward horizontally, 9 is the vacuum chamber wall of the equipment, and 10 is a rotatable sample stage.

[0014] Figure 2 It is the result of the cupping test (60 KgF) of the coatings obtained by different embodiments.

[0015] Figure 3 It is the coating structure and morphology of the lead screw raceway wall obtained in Example 1.

[0016] Figure 4 It is a schematic diagram of the coating of the present invention. Detailed Embodiment Example

[0017] An ultra-thick amorphous carbon coating is prepared by a magnetron sputtering - multi-arc evaporation combined deposition method 1) Pretreat the lead screw to make it clean and dry; 2) Clamp the clean lead screw on the sample workpiece holder and drive the workpiece holder and the lead screw to rotate uniformly; 3) Start the magnetron sputtering - multi-arc evaporation combined deposition coating equipment and deposit the ultra-thick amorphous carbon coating according to the following process: A) Sequentially, ① evacuate the coating chamber of the coating equipment to 2×10 -3 Pa; ② introduce and maintain 300 sccm of argon gas; ③ turn on the bias voltage of -1000 V and maintain it for 15 min; ④ lower the bias voltage to -600 V and maintain it for 15 min; subsequently, B) The bias voltage is adjusted down to -150V. At the same time, start 3 multi-arc chromium targets with the target surface normal tilted 3° upward horizontally and 3 multi-arc chromium targets with the target surface normal tilted 3° downward horizontally, and set the current of each chromium target to 50A and work for 20 min. Subsequently (the next step C starts only after 20 - 25 min of the work in this step, and the chromium targets described in B still continue to work during the work of C), C) Start 6 multi-arc carbon targets with the target surface normal tilted 3° upward horizontally and 6 multi-arc carbon targets with the target surface normal tilted 3° downward horizontally, set the starting current of each multi-arc carbon target to 30A, and within 20 min, linearly increase the current of each multi-arc carbon target to 90A; D) Simultaneously with step C, start 2 rectangular magnetron sputtering carbon targets, set the starting power of each magnetron sputtering carbon target to 600W, and within 20 min, linearly increase the power of each magnetron sputtering carbon target to 2600W; Subsequently, E) Turn off 6 multi-arc chromium targets; let each multi-arc carbon target and each magnetron sputtering carbon target continue to work for 5 h in the current and power states they finally reach; 4) Shut down the coating instrument and take out the coated lead screw.

[0018] The thickness of the ultra-thick amorphous carbon coating deposited on the lead screw groove wall according to the above process reaches 20μm, including: a chromium bottom layer with a thickness of 2μm, a carbon-chromium binary transition layer with a thickness of 3μm, and an amorphous carbon top layer with a thickness of 15μm. The hardness of the coating is measured to be 3200HV by a Vickers hardness tester 0.1 , and no spalling of the coating is detected by the 60Kg Rockwell indentation method. Example

[0019] An ultra-thick amorphous carbon coating is prepared by a method of combined magnetron sputtering - multi-arc evaporation 1) Pretreat the lead screw to make it clean and dry; 2) Clamp the clean lead screw on the sample workpiece holder and drive the workpiece holder and the lead screw to rotate at a constant speed; 3) Start the combined magnetron sputtering - multi-arc evaporation coating equipment and deposit an ultra-thick amorphous carbon coating according to the following process: A) Sequentially, ① evacuate the coating chamber of the coating equipment to 2×10 -3 Pa; ② introduce and maintain 300 sccm of argon gas; ③ turn on the bias voltage of -1000V and maintain it for 15 min; ④ adjust the bias voltage down to -600V and maintain it for 15 min; Subsequently, B) The bias voltage is adjusted down to -150V. At the same time, start 3 multi-arc chromium targets with the target surface normal tilted 3° upward horizontally and 3 multi-arc chromium targets with the target surface normal tilted 3° downward horizontally, and set the current of each chromium target to 50A and work for 20 minutes. Subsequently (step C starts 20 - 25 minutes after this step, and the chromium targets described in B still continue to work when C is working), C) Start 6 multi-arc carbon targets with the target surface normal tilted 3° upward horizontally and 6 multi-arc carbon targets with the target surface normal tilted 3° downward horizontally, set the starting current of each multi-arc carbon target to 30A, and within 20 minutes, linearly increase the current of each multi-arc carbon target to 90A; D) Simultaneously with step C, start 2 rectangular magnetron sputtering carbon targets, set the starting power of each magnetron sputtering carbon target to 600W, and within 20 minutes, linearly increase the power of each magnetron sputtering carbon target to 2600W; Subsequently, E) Turn off the 6 multi-arc chromium targets; let each multi-arc carbon target and each magnetron sputtering carbon target continue to work for 10 hours in the current and power states they finally reach.

[0020] 4) Shut down the coating equipment and take out the coated lead screw.

[0021] The thickness of the ultra-thick amorphous carbon coating deposited on the lead screw groove wall according to the above process reaches 35μm, including: a chromium bottom layer with a thickness of 2μm, a carbon-chromium binary transition layer with a thickness of 3μm, and an amorphous carbon top layer with a thickness of 30μm. The hardness of the coating is measured to be 3300HV using a Vickers hardness tester 0.1 , and no peeling of the coating is detected using the 60Kg Rockwell indentation method.

[0022] Prepare the ultra-thick amorphous carbon coating using the multi-arc evaporation method 1) Pretreat the lead screw to make it clean and dry; 2) Clamp the clean lead screw on the sample workpiece holder and drive the workpiece holder and the lead screw to rotate at a constant speed; 3) Start the multi-arc evaporation coating equipment and deposit the ultra-thick amorphous carbon coating according to the following process: A) Sequentially, ① evacuate the coating chamber of the coating equipment to 2×10 -3 Pa; ② introduce and maintain 300 sccm of argon gas; ③ turn on the bias voltage of -1000V and maintain it for 30 minutes; ④ adjust the bias voltage down to -600V and maintain it for 15 minutes; Subsequently, B) Adjust the bias voltage down to -150V. At the same time, start 3 multi-arc chromium targets with the target surface normal tilted 3° upward horizontally and 3 multi-arc chromium targets with the target surface normal tilted 3° downward horizontally, set the current of each chromium target to 50A, and work for 20 minutes; Subsequently, C) Start the 6 multi-arc carbon targets with the target surface normal inclined upward horizontally and the 6 multi-arc carbon targets with the target surface normal inclined downward horizontally. Set the starting current of each multi-arc carbon target to 30 A, and linearly increase the current of each multi-arc carbon target to 90 A within 20 minutes; D) Turn off the 6 multi-arc chromium targets; let each multi-arc carbon target and each magnetron sputtering carbon target continue to work for 5 h with the finally reached current and power states.

[0023] The thickness of the ultra-thick amorphous carbon coating plated on the lead screw groove wall according to the above process reached 18 μm, including: a chromium bottom layer with a thickness of 2 μm, a carbon-chromium binary transition layer with a thickness of 3 μm, and an amorphous carbon top layer with a thickness of 13 μm. The hardness of the coating was measured to be 4100 HV using a Vickers hardness tester 0.1 v0.1. When measured by the 60 Kg Rockwell indentation method, severe peeling of the coating occurred, which could not meet the application requirements.

Claims

1. An ultra-thick amorphous carbon coating plated on a lead screw raceway, characterized in that, The super-thick amorphous carbon coating is a laminated coating, which includes a chromium bottom layer, a carbon-chromium binary transition layer, and an amorphous carbon top layer that are sequentially plated on the lead screw. The total thickness of the laminated coating is 20 - 35 μm. Among them, the thickness of the amorphous carbon top layer is 15 - 30 μm.

2. The ultra-thick amorphous carbon coating plated on the lead screw raceway according to claim 1 is a laminated coating, characterized in that, The amorphous carbon top layer is formed by alternately overlapping a magnetron sputtered carbon film sub-layer and a multi-arc carbon film sub-layer.

3. The ultra-thick amorphous carbon coating plated on the lead screw raceway according to claim 1 is a laminated coating, characterized in that, The thickness of the chromium bottom layer is 2 μm, and the thickness of the carbon-chromium binary transition layer is 3 μm.

4. The super-thick amorphous carbon coating plated on the lead screw raceway as claimed in claim 1 is a laminated coating, characterized in that, The material of the lead screw is iron-based metal.

5. A method for preparing an ultra-thick amorphous carbon coating plated on a lead screw raceway according to any one of claims 1 to 4, characterized in that, First, the lead screw with a raceway groove is subjected to argon plasma etching, then the chromium bottom layer is deposited by multi-arc evaporation, then the carbon-chromium binary transition layer is deposited by multi-arc evaporation, and finally the amorphous carbon top layer is deposited by a combined magnetron sputtering - multi-arc evaporation method.

6. The preparation method of an ultra-thick amorphous carbon coating plated on a lead screw raceway according to claim 5, characterized in that, The method uses a combined magnetron sputtering - multi-arc evaporation coating equipment. In the coating chamber of the coating equipment, there are a magnetron sputtered carbon target, a multi-arc carbon target, and a multi-arc chromium target. The arrangement of each target is as follows: In the center position of the coating chamber of the coating equipment is a rotatable workpiece holder for placing the substrate. The inner wall of the chamber is sequentially arranged with 1 - 8 target positions at intervals in a circular pattern. The 1st target position is 1 planar rectangular magnetron sputtered carbon target. The 2nd target position is 3 multi-arc carbon targets with the target surface normal inclined upward horizontally. The 3rd target position is 3 multi-arc chromium targets with the target surface normal inclined upward horizontally. The 4th target position is 3 multi-arc carbon targets with the target surface normal inclined downward horizontally. The 5th target position is 1 planar rectangular magnetron sputtered carbon target. The 6th target position is 3 multi-arc carbon targets with the target surface normal inclined upward horizontally. The 7th target position is 3 multi-arc chromium targets with the target surface normal inclined downward horizontally. The 8th target position is 3 multi-arc carbon targets with the target surface normal inclined downward horizontally. Among them, the 2nd, 3rd, 4th, 6th, 7th, and 8th target positions are all arranged in a row of three types according to the distribution of the inner wall of the chamber.

7. The preparation method of an ultra-thick amorphous carbon coating plated on a lead screw raceway according to claim 6, characterized in that, The specific steps are as follows: 1) Pretreat the lead screw to make it clean and dry. 2) Clamp the clean lead screw on the sample workpiece holder and drive the workpiece holder and the lead screw to rotate at a constant speed. 3) Start the combined magnetron sputtering - multi-arc evaporation coating equipment and deposit the super-thick amorphous carbon coating according to the following process: A) Sequentially, ① evacuate the coating chamber of the coating equipment to 2×10 -3 ~2.1×10 -3 Pa; ② introduce and maintain argon at 300 - 330 sccm; ③ turn on the bias voltage of -1000 ± 50 V and maintain it for 15 - 20 min; ④ lower the bias voltage to -600 ± 50 V and maintain it for 15 - 20 min; B) Adjust the bias voltage to -150 ± 10 V. At the same time, start 3 multi-arc chromium targets with the target surface normal inclined upward horizontally and 3 multi-arc chromium targets with the target surface normal inclined downward horizontally, and make the current of each chromium target 50 ± 5 A, and work for 20 - 25 min. C) Start 6 multi-arc carbon targets with the target surface normal inclined upward horizontally and 6 multi-arc carbon targets with the target surface normal inclined downward horizontally, and make the starting current of each multi-arc carbon target 30 ± 3 A, and within 20 min, linearly increase the current of each multi-arc carbon target to 90 ± 5 A. D) Simultaneously with step C, start 2 rectangular magnetron sputtered carbon targets, and make the starting power of each magnetron sputtered carbon target 600 ± 50 W, and within 20 min, linearly increase the power of each magnetron sputtered carbon target to 2600 ± 100 W. E) Turn off 6 multi-arc chromium targets, and make each multi-arc carbon target and each magnetron sputtered carbon target continue to work for 5 - 10 h in the current and power states finally reached. 4) Shut down the coating instrument and take out the coated lead screw.

Images