Preparation method of a superhard gradient TiN / TiAlN / TiAlZrN composite coating

Abstract

The present invention discloses a preparation method of a superhard gradient TiN / TiAlN / TiAlZrN composite coating, which includes the following steps: S1: The substrate is ultrasonically oscillated in acetone and absolute ethanol in sequence, cleaned with deionized water and then dried, and then the substrate is fixed on the rotary furnace rack and rotated self in the coating chamber; S2: Remove the debris on the surface of the target; Subsequently, etch the substrate under a bias voltage of -700V to remove the oxide scale on the substrate surface and activate the substrate surface at the same time; S3: Obtain a TiN bottom layer; S4: Obtain a TiAlN transition layer with a gradually increasing c-AlN phase; S5: Obtain a TiAlZrN layer; S6: Bombard the prepared coating under a bias voltage of -200V. The coating prepared by the present invention has good oxidation resistance, superhardness, wear resistance and excellent toughness. In the coating structure, Zr replaces Ti atoms in TiN to form a TiZrN substitutional solid solution, and this solid solution strengthening helps to increase the hardness. In addition, the larger Zr atoms dissolved into the TiN unit cell have a more effective hindering effect on dislocations than the smaller Ti atoms with a smaller atomic radius, which is also beneficial to the increase of the coating hardness.

Description

Technical Field

[0001] The present invention relates to the technical field of surface modification, and particularly to a preparation method of a superhard gradient TiN / TiAlN / TiAlZrN composite coating. Background Art

[0002] With the continuous development of industry and the increasing requirements for the performance of components, new challenges are faced by machining tools. Seeking coated cutting tools that can adapt to high-temperature machining environments and cut hard materials has become a hot topic of concern. When machining some difficult-to-machine materials, the oxidation resistance temperature and hardness of TiAlN coatings cannot meet the requirements. Therefore, finding a new coating system to further improve the performance of coated cutting tools has become a research hotspot. Although TiAlSiN nanocomposite coatings exhibit superhardness, the internal stress of the coatings is relatively large, and peeling is likely to occur during use, resulting in coating failure and unable to meet the use requirements of coated cutting tools. Therefore, there is an urgent need to develop a preparation method of a superhard gradient TiN / TiAlN / TiAlZrN composite coating to solve the above technical problems.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] The object of the present invention is to provide a preparation method of a superhard gradient TiN / TiAlN / TiAlZrN composite coating. The coating prepared by this method has good oxidation resistance, superhardness, wear resistance, and excellent toughness. In the coating structure, Zr replaces Ti atoms in TiN to form a TiZrN substitutional solid solution, and this solid solution strengthening helps to increase the hardness. In addition, the hindrance effect of larger Zr atoms dissolved in the TiN unit cell on dislocations is more effective than that of smaller Ti atoms with a smaller atomic radius, which is also beneficial to the increase of the coating hardness. It has broad application prospects and is conducive to popularization and application.

[0005] In order to achieve the above object, a preparation method of a superhard gradient TiN / TiAlN / TiAlZrN composite coating provided by the present invention includes the following steps:

[0006] S1: The substrate is ultrasonically oscillated in acetone and absolute ethanol for 8 - 12 min in sequence, washed with deionized water for 4 - 8 min and then dried, and then the substrate is fixed on a rotary furnace rack and rotated in the coating chamber by itself;

[0007] S2: Pre-evacuate to 1x10 -3 to 3x10 -3At Pa, heat the furnace chamber to 400 - 450 °C, introduce argon at 160 - 200 sccm, and perform self - cleaning of the Ti target for 3 - 8 min at a current of 130 - 150 A to remove debris on the target surface; subsequently, etch the substrate for 10 - 15 min at a bias voltage of - 700 - 750 V to remove the scale on the substrate surface, and at the same time activate the substrate surface to improve the adhesion strength of the coating on the substrate;

[0008] S3: When the vacuum degree is 1 x 10 -1 to 3 x 10 -1 Pa, connect the Ti target to a current of 120 - 140 A, introduce N2 at 160 - 200 sccm, and deposit for 3 - 5 min at a bias voltage of - 120 to - 100 V on the substrate to obtain a TiN bottom layer;

[0009] S4: Connect the Al 0.67 Ti 0.33 target to a current of 100 - 120 A, introduce N2 at 160 - 200 sccm, and deposit for 60 - 70 min at a bias voltage of - 120 V to - 100 V on the substrate to obtain a TiAlN transition layer with a gradually increasing cubic AlN phase, which is obtained by changing the deposition rate;

[0010] S5: Connect the Al 0.67 Ti 0.33 target to a current of 100 - 120 A, and connect the Al 0.5 Zr 0.5 target to a current of 120 - 160 A, introduce N2 at 160 - 200 sccm, and deposit for 20 - 25 min at a bias voltage of - 100 V to - 80 V on the substrate to obtain a TiAlZrN layer;

[0011] S6: Close the nitrogen, introduce argon at 180 - 200 sccm, place the baffle in front of the Ti target, connect the Ti target to a current of 100 - 120 A, and bombard the coating for 10 - 15 min at a bias voltage of - 220 V to - 180 V to relax the bond lengths and bond angles inside the coating and further reduce the internal stress of the coating.

[0012] Preferably, in S5, when preparing the TiAlZrN layer, the current connected to the Al 0.5 Zr 0.5 target gradually rises from 120 A to 160 A to obtain a TiAlZrN layer with a gradually increasing Zr content. The gradual increase of the Zr element is beneficial for TiAlZrN to reduce the thermal expansion coefficient between the TiAlN and TiAlZrN layers and reduce the stress. In addition, as the Zr content increases, its solid solution increases, and the hardness and temperature resistance of the coating gradually increase.

[0013] Preferably, the design of the TiN / TiAlN / TiAlZrN three-layer structure follows the principle that the hardness gradually increases and the difference in thermal expansion coefficient gradually decreases. In addition, the single layer of TiAlN or TiAlZrN also follows this principle. Therefore, the film has low internal stress, high hardness, and good coating toughness.

[0014] Preferably, in the TiN / TiAlN / TiAlZrN three-layer structure, the TiAlN transition layer is the thickest, and the TiAlZrN layer is thinner than the TiAlN layer. This is because the internal stress of the TiAlZrN layer is greater than that of TiAlN. If a relatively thick TiAlZrN layer is deposited, the film is likely to peel off and fail during use. Therefore, a relatively thick TiAlN layer is designed in the intermediate layer to improve the bearing capacity of the film while reducing the internal stress of the coating.

[0015] The preparation method of a superhard gradient TiN / TiAlN / TiAlZrN composite coating provided by the present invention has the following beneficial effects.

[0016] 1. The present invention improves the hardness, wear resistance, and high-temperature resistance of the original TiAlN coating. The coating preparation is completed by low-energy ion bombardment, which reduces the internal stress of the entire film, improves the internal structure and surface quality of the coating, reduces the surface roughness of the coating, improves the anti-adhesion of the TiAlZrN coating during machining, and greatly enhances the service life of the coating.

[0017] 2. When designing the film system in the coating industry, adding or removing a single layer may cause great changes in the performance of the entire film system. The present invention uses metal Zr atoms to replace Ti atoms in TiAlN to form a TiAlZrN solid solution, which can improve the hardness and thermal stability of the TiAlN coating without introducing too much internal stress. In addition, the larger Zr atoms dissolved in the TiAlN unit cell have a more effective hindrance effect on dislocations than the smaller Ti atoms, which is also beneficial to the increase in the hardness of the coating.

[0018] 3. At present, the cutting of difficult-to-machine materials such as aviation aluminum and superalloys has always been a bottleneck. The present invention was accidentally discovered by the inventor through a large number of experimental studies and practical applications. This film layer structure has the above advantages and has obvious advantages in aspects such as coating stress release, coating hardness improvement, and inhibition of microcrack propagation, which can significantly improve the service life of coated tools and solve the technical problems that people have been eager to solve but have not been successful. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a cross-sectional morphology diagram of the superhard gradient TiN / TiAlN / TiAlZrN composite coating prepared by the present invention;

[0020] Figure 2Composition distribution diagram of the superhard gradient TiN / TiAlN / TiAlZrN composite coating prepared for this invention. Detailed implementation mode

[0021] The following combines specific embodiments and the attached drawings to further explain this invention to help understand the content of this invention.

[0022] A preparation method of a superhard gradient TiN / TiAlN / TiAlZrN composite coating provided by this invention includes the following steps:

[0023] S1: The substrate is ultrasonically oscillated in acetone and absolute ethanol for 10 minutes in sequence, washed with deionized water for 5 minutes and then dried, and then the substrate is fixed on the rotary furnace rack and rotated in the coating chamber.

[0024] S2: Pre-pump the vacuum to 1x10 -3 Pa, heat the furnace cavity to 450 °C, introduce 200 sccm of argon gas, and the Ti target is self-cleaned for 3 minutes under a current of 120 A to remove the debris on the target surface; then the substrate is etched for 10 minutes under a bias voltage of -700 V to remove the oxide scale on the substrate surface, and at the same time activate the substrate surface to improve the adhesion strength of the coating on the substrate.

[0025] S3: When the vacuum degree is 0.3 Pa, the Ti target is connected to a current of 120 A, 200 sccm of N2 is introduced, and the substrate is deposited for 3 minutes under a bias voltage of -120 V to obtain a TiN bottom layer.

[0026] S4: The Al 0.67 Ti 0.33 target is connected to a current of 120 A, 200 sccm of N2 is introduced, and the substrate is deposited for 60 minutes under a bias voltage from -120 V to -100 V to obtain a TiAlN transition layer with a gradually increasing c-AlN phase; among them, the Al 0.67 Ti 0.33 target is connected to a current of 120 A, 200 sccm of N2 is introduced, and the substrate is deposited for 60 minutes under a bias voltage from -120 V to -100 V to obtain a TiAlN transition layer with a gradually increasing cubic AlN phase by changing the deposition rate.

[0027] S5: The Al 0.67 Ti 0.33 target is connected to a current of 120 A, the Al 0.5 Zr 0.5 target is connected to a current of 120 - 160 A, 200 sccm of N2 is introduced, and the substrate is deposited for 20 minutes under a bias voltage of -100 V to obtain a TiAlZrN layer; among them, when preparing the TiAlZrN layer, the Al 0.5 Zr 0.5The current of the target access gradually increases from 120 A to 160 A, and a TiAlZrN layer with a gradually increasing Zr content is obtained. The gradual increase of the Zr element is beneficial to reducing the thermal expansion coefficient between TiAlN and the TiAlZrN layer and reducing stress. In addition, as the Zr content increases, its solid solution increases, and the hardness and temperature resistance of the coating gradually increase.

[0028] S6: Close the nitrogen gas, introduce 200 sccm of argon gas, place the baffle in front of the Ti target, connect the Ti target to a current of 120 A, and bombard the coating for 10 min at a bias voltage of -200 V. Among them, after obtaining the TiN / TiAlN / TiAlZrN composite coating, introduce 200 sccm of argon gas, place the baffle in front of the Ti target, connect the Ti target to a current of 120 A, and bombard the coating for 10 min at a bias voltage of -200 V to relax the bond lengths and bond angles inside the coating and further reduce the internal stress of the coating.

[0029] The design of the TiN / TiAlN / TiAlZrN three-layer structure follows the principle of gradually increasing hardness and gradually decreasing thermal expansion coefficient difference. In addition, the single layer of TiAlN or TiAlZrN also follows this principle. Therefore, the internal stress of the film layer is low, the hardness is high, and the toughness of the coating is good.

[0030] In the TiN / TiAlN / TiAlZrN three-layer structure, the thickness of the TiAlN transition layer is the thickest, and the TiAlZrN layer is thinner than the TiAlN layer. This is because the internal stress of the TiAlZrN layer is greater than that of TiAlN. If a relatively thick TiAlZrN layer is deposited, the film layer is likely to peel off and fail during use. Therefore, a relatively thick TiAlN layer is designed in the intermediate layer to improve the bearing capacity of the film layer while reducing the internal stress of the coating.

[0031] As Figure 1 shown, it is the cross-sectional morphology diagram of the superhard gradient TiN / TiAlN / TiAlZrN composite coating prepared by the present invention. It can be clearly observed from the figure that the combination between each layer is dense and there are no obvious defects such as microcracks. In addition, there is no obvious boundary between TiN and TiAlN.

[0032] As Figure 2 shown, it is the composition distribution diagram of the superhard gradient TiN / TiAlN / TiAlZrN composite coating prepared by the present invention. From the figure, the change trend of each element during the growth of the coating can be seen, and it can also be observed that there is a mixing zone between the TiAlN layer and the TiAlZrN layer, which can improve the binding tightness between layers and reduce the stress caused by lattice mismatch.

[0033] Hardness testing, friction coefficient testing, stress testing, surface roughness testing and temperature resistance testing were carried out on the superhard gradient TiN / TiAlN / TiAlZrN composite coating prepared by the present invention. The testing methods are as follows:

[0034] Hardness testing: The nano-hardness and Young's modulus of the coating were tested and calculated using a nano-indentation instrument (Hysitron TI-950, USA). The continuous stiffness indentation mode was selected, with a loading force of 15 mN. At the same time, to ensure the accuracy of the coating hardness, the indentation depth did not exceed 1 / 10 of the coating thickness.

[0035] Friction coefficient testing: Under atmospheric environment, a UMT-3 friction testing machine was used to test the tribological properties of the TiAlSiCN coating. The friction mode was ball-on-disk. A Si3N4 ceramic ball with a diameter of 9.5 mm was selected as the friction pair, with a load of 10 N, a rotation speed of 200 r / min, a wear scar diameter of 10 mm, and a friction time of 10 min. A white light interferometer was used to measure the wear volume of the coating, and the wear rate of the coating was calculated according to the formula W = V / FS, where: V - wear volume; F - load; S - friction path.

[0036] Stress testing: It was obtained by using the curvature method and calculating with the stoney formula.

[0037] Surface roughness testing: It was obtained using an atomic force microscope

[0038] Temperature resistance testing: The coating was heated using a muffle furnace (SX-10-120, China). The cavity of the muffle furnace was heated to 400 °C, 600 °C, 800 °C and 1000 °C respectively and held, then the specimen was placed in the furnace cavity together with the tray, and kept warm for 120 min and cooled with the furnace.

[0039] The present invention improves the hardness of the original TiAlN coating (rising from 33.47 GPa of TiAlN to 38.64 GPa), wear resistance (the friction coefficient drops from 0.41 of TiAlN to 0.28), and high-temperature resistance (rising from 800 °C of TiAlN to 1000 °C). The coating preparation is completed by low-energy ion bombardment, reducing the internal stress of the entire film layer (the stress drops from -3.5 GPa to -2.6 GPa), improving the internal structure and surface quality of the coating, reducing the surface roughness of the coating (the surface roughness drops from Sq = 45 nm to Sq = 27 nm), improving the anti-adhesion property of the TiAlZrN coating during machining, and greatly enhancing the service life of the coating. When designing the film system in the coating industry, adding or removing one layer may cause a great change in the performance of the entire film system. The present invention uses metal Zr atoms to replace Ti atoms in TiAlN to form a TiAlZrN solid solution, which can improve the hardness and thermal stability of the TiAlN coating without introducing too much internal stress. In addition, the larger Zr atoms dissolved in the TiAlN unit cell have a more effective hindering effect on dislocations than the smaller Ti atoms in terms of atomic radius, which is also beneficial to the increase in the hardness of the coating. At present, the cutting of difficult-to-machine materials such as aerospace aluminum and superalloys has always been a bottleneck. The present invention was accidentally discovered by the inventor in a large number of experimental studies and practical applications. This film layer structure has the above advantages and has obvious advantages in aspects such as coating stress release, coating hardness improvement, and suppression of microcrack propagation, which can significantly improve the service life of coated tools and solve the technical problems that people have been eager to solve but have not been successful in obtaining.

[0040] Specific examples are used in this article to elaborate on the inventive concept in detail. The description of the above embodiments is only used to help understand the core idea of the present invention. It should be pointed out that for those of ordinary skill in the art of this technology, any obvious modifications, equivalent replacements, or other improvements made without departing from the inventive concept shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a superhard gradient TiN / TiAlN / TiAlZrN composite coating, characterized in that, It includes the following steps: S1: The substrate is ultrasonically oscillated in acetone and absolute ethanol for 8 - 12 min in sequence, washed with deionized water for 4 - 8 min and then dried. Then the substrate is fixed on the rotary furnace rack and rotated self - in the coating chamber. S2: Pre-evacuate to 1x10 -3 to 3x10 -3 Pa, heat the furnace chamber to 400 - 450 °C, introduce argon at 160 - 200 sccm, self-clean the Ti target for 3 - 8 min at a current of 130 - 150 A to remove debris on the target surface; then etch the substrate for 10 - 15 min under a bias voltage of -700 - 750 V to remove the oxide scale on the substrate surface, and at the same time activate the substrate surface to improve the adhesion strength of the coating on the substrate; S3: When the vacuum degree is from 1x10 -1 to 3x10 -1 Pa, connect the Ti target to a current of 120 - 140 A, introduce N2 of 160 - 200 sccm, and deposit for 3 - 5 min under a substrate bias voltage of -120 to -100 V to obtain a TiN underlayer; S4: Al 0.67 Ti 0.33 The target is connected to a current of 100 - 120 A, and N2 with a flow rate of 160 - 200 sccm is introduced. The substrate is deposited for 60 - 70 min under a bias voltage of -120 V to -100 V, and a TiAlN transition layer with a gradually increasing cubic AlN phase is obtained by changing the deposition rate; S5: Al 0.67 Ti 0.33 The target is connected to a current of 100 - 120 A, Al 0.5 Zr 0.5 The target is connected to a current of 120 - 160 A, and N2 of 160 - 200 sccm is introduced. The substrate is deposited for 20 - 25 min under a bias voltage of - 100 V to - 80 V to obtain a TiAlZrN layer; S6: Nitrogen is turned off, 180 - 200 sccm of argon is introduced, the baffle is placed in front of the Ti target, the Ti target is connected to a current of 100 - 120 A, and the coating is bombarded for 10 - 15 min under a bias voltage of - 220 V to - 180 V. The design of the TiN / TiAlN / TiAlZrN three - layer structure follows the principle that the hardness gradually increases and the difference in thermal expansion coefficient gradually decreases. In addition, the single layer of TiAlN or TiAlZrN also follows this principle. In the TiN / TiAlN / TiAlZrN three - layer structure, the TiAlN transition layer is the thickest, and the TiAlZrN layer is thinner than the TiAlN layer.

2. The preparation method of a superhard gradient TiN / TiAlN / TiAlZrN composite coating according to claim 1, wherein, In S5, when preparing the TiAlZrN layer, Al 0.5 Zr 0.5 The current applied to the target gradually increases from 120 A to 160 A to obtain a TiAlZrN layer with a gradually increasing Zr content.

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