A low-residual-stress superhard titanium alloyed zirconium diboride film and a preparation method thereof

Abstract

The application discloses a low-residual-stress superhard titanium alloy zirconium diboride film and a preparation method thereof, and steps are as follows: step 1: a zirconium diboride target, a titanium target and a zirconium target are respectively installed on three radio frequency power sources; step 2: a substrate is subjected to impurity removal treatment and is placed on a base; step 3: a reaction chamber is vacuumized; inert gas is introduced until the pressure of the reaction chamber is 0.1 Pa; and pre-sputtering treatment is carried out; step 4: the base bias is set to 20 V, and the rotating speed is 5 rpm; the radio frequency power source provided with the zirconium target is first started, the power is set to 50 W, and a transition layer is plated on the surface of the substrate; then the other two radio frequency power sources are simultaneously started to carry out sputtering, and a preliminary composite film is obtained; and step 5: the preliminary composite film is annealed in a vacuum environment at 800 DEG C to obtain a final composite film. The hardness of the application reaches 42 GPa, the residual stress is only 0.359 GPa, and the oxidation resistance and high-temperature friction and wear resistance are simultaneously improved.

Description

Technical Field

[0001] This invention relates to the field of thin film materials and surface engineering technology, and in particular to a low residual stress ultra-hard titanium alloyed zirconium diboride thin film and its preparation method. Background Technology

[0002] With the rapid development of aerospace, energy equipment, and advanced manufacturing, engineering materials are prone to severe wear and oxidation when operating under high temperature, high speed, and high load conditions, leading to material performance degradation or even failure. Therefore, depositing protective coatings with excellent properties on material surfaces has become an important technical means to improve material service life. Common methods for coating preparation include chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD). Among these, PVD, as a mature preparation technology, has advantages such as good film quality, strong controllability, and environmental friendliness. However, PVD technology still has certain limitations in practical applications: First, PVD-deposited films have relatively weak coverage of complex-shaped workpieces and areas such as deep holes and grooves, easily leading to uneven film thickness; second, the high particle energy during deposition often generates significant residual stress within the film, resulting in film cracking or decreased adhesion; furthermore, PVD deposition rates are relatively limited, equipment and operation / maintenance costs are high, and strict requirements for vacuum environment and process parameter control remain, posing challenges for large-area continuous production.

[0003] Transition metal diborides are a typical class of ultra-high temperature ceramics (UHTCs). Among them, ZrB2 possesses an extremely high melting point (~3245℃), high hardness (~23 GPa), excellent thermal shock resistance, and outstanding corrosion resistance, thus showing immeasurable development prospects in refractory materials, electrodes, cutting tools, and thermal protection systems for hypersonic flight. However, ZrB2 films still suffer from inherent defects as hard ceramic films, thus limiting their further applications. First, ZrB2 films exhibit poor toughness at high temperatures (K... IC <5MPa·m 1 / 2This makes ZrB2 prone to brittle fracture under high load and high stress environments, severely impacting its long-term service performance. Furthermore, the low density of ZrB2 films makes them susceptible to cracking or peeling under high temperature and high friction conditions, limiting their lifespan. In addition, ZrB2 films exhibit poor oxidation resistance, especially under high-temperature oxidation environments, where the surface oxide layer is not sufficiently stable. During oxidation, the oxide layer formed on the ZrB2 surface is prone to peeling or embrittlement, leading to further oxidation and affecting the film's protective performance and thermal shock resistance. Although ZrB2 has a relatively high oxidation initiation temperature (approximately 700°C), the stability of its oxide layer under prolonged high-temperature exposure still fails to meet the requirements of high-end applications. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a low residual stress ultra-hard titanium alloy zirconium diboride thin film and its preparation method, thereby solving the technical problems of poor toughness and insufficient hardness inherent in existing films.

[0005] This invention provides a low residual stress ultra-hard titanium alloy zirconium diboride thin film, the composition of which includes Zr, Ti and B, and the mass ratio of each component is 1:1:2.

[0006] This invention also provides a method for preparing a low residual stress ultra-hard titanium alloyed zirconium diboride thin film, comprising the following steps:

[0007] Step 1: Install the zirconium diboride target, elemental titanium target, and elemental zirconium target onto the three RF power supplies respectively;

[0008] Step 2: Remove impurities from the substrate and place it on the rotating substrate in the reaction chamber of the magnetron sputtering coating apparatus;

[0009] Step 3: Evacuate the reaction chamber to a vacuum level less than 6 × 10⁻⁶. -4 Pa; Inert gas is introduced until the pressure in the reaction chamber is 0.1 Pa; Pre-sputtering treatment is performed;

[0010] Step 4: Set the substrate bias voltage to 20V and the substrate rotation speed to 5rpm; first turn on the RF power supply with the zirconium target mounted, and set the power to 50W to deposit a transition layer on the substrate surface; then simultaneously turn on the other two RF power supplies for sputtering to obtain a preliminary composite film on the substrate surface. The power supply with the zirconium diboride target mounted is set to 180W; the power supply with the titanium target mounted is set to 10-30W.

[0011] Step 5: Anneal the preliminary composite film prepared in Step 4 in a vacuum environment at 800℃ to obtain a superhard titanium alloyed zirconium diboride film with low residual stress.

[0012] Furthermore, the purity of the zirconium diboride target, elemental titanium target, and elemental zirconium target is ≥99.99%.

[0013] Furthermore, in step 2, the specific method for removing impurities from the substrate is as follows: the substrate is placed in acetone and anhydrous ethanol and cleaned by ultrasonication to remove impurities.

[0014] Furthermore, in step 3, the specific method for evacuating the reaction chamber is as follows: first, a mechanical pump is used to evacuate the chamber until the vacuum level reaches 8 × 10⁻⁶. -3 After Pa, a molecular pump is used to evacuate the vacuum until the vacuum level is less than 6 × 10⁻⁶. -4 Pa.

[0015] Furthermore, in step 3, the inert gas introduced is Ar, and the flow rate is 20 sccm.

[0016] Furthermore, in step 3, the specific method for pre-sputtering is as follows: set the power of the three RF power supplies to 50W and perform pre-sputtering for 30 minutes.

[0017] Furthermore, in step 4, the sputtering time is 2.5 hours; the thickness of the obtained preliminary composite film is 1.1 μm.

[0018] Furthermore, in step 5, the annealing time is 1 hour; the vacuum level of the vacuum environment is less than 1×10⁻⁶. -3 Pa.

[0019] This invention also provides an application of a low residual stress ultra-hard titanium alloyed zirconium diboride thin film in thermal protection systems and machining fields.

[0020] The beneficial effects of this invention are:

[0021] This invention improves the microstructure of thin films by adjusting the Ti content to form a (Zr,Ti)B2 solid solution, thereby significantly increasing the film's hardness and elastic modulus. At a Ti sputtering power of 20W (i.e., the power of the second RF power supply is 20W), the film hardness reaches a maximum of 42.07 ± 0.8 GPa, demonstrating a significant solid solution strengthening effect.

[0022] The introduction of Ti in this invention significantly improves the oxidation resistance of the ZrB2 film. Under high-temperature oxidation conditions, Ti preferentially reacts with oxygen to form a stable oxide, TiO2, which inhibits the peeling of the oxide layer and prevents oxygen from diffusing into the film, thereby improving the long-term stability and service life of the film. Compared with pure ZrB2 films, the composite film of this invention exhibits stronger oxidation resistance during oxidation and demonstrates superior high-temperature oxidation resistance.

[0023] The Zr-Ti-B2 composite film of this invention exhibits significantly lower friction coefficient and wear rate than the pure ZrB2 film at a high temperature of 600°C. Particularly at a Ti sputtering power of 20W, the friction coefficient reaches a minimum of 0.66, and the wear rate is 4.643 × 10⁻⁶. - 5 mm 3 The introduction of Ti ( / N·mm) helps to form a more stable lubricating layer under high temperature conditions, reducing the wear rate of the film and extending its service life. Attached Figure Description

[0024] The features and advantages of the invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the invention in any way. In the drawings:

[0025] Figure 1 This is a flowchart of a specific embodiment of the present invention;

[0026] Figure 2 The image shown is the XRD pattern of the composite film after annealing in Specific Embodiment 1 of the present invention.

[0027] Figure 3 This is a friction curve of the composite film after annealing in specific embodiment 1 of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0029] The present invention will be further illustrated below with reference to specific embodiments. Those skilled in the art should understand that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Modifications to the present invention in various equivalent forms all fall within the scope defined by the appended claims.

[0030] like Figure 1 As shown, this invention provides a method for preparing a low residual stress ultra-hard titanium alloy zirconium diboride thin film, as detailed below:

[0031] S1: Preparation of sputtering target:

[0032] The zirconium diboride target is installed on the first radio frequency power supply, the elemental titanium target is installed on the second radio frequency power supply, and the elemental zirconium target is installed on the third radio frequency power supply; the target materials are all made by high-temperature sintering, and the molar ratio of Zr, Ti and B is 1:1:2.

[0033] S2: Substrate pretreatment:

[0034] The substrate was ultrasonically cleaned in acetone and anhydrous ethanol for 15 minutes each, and then dried to obtain a contamination-free substrate. Two types of substrates were selected: single crystal Si wafers and sapphire wafers. Composite films were deposited on Si wafers for characterization, and composite films were deposited on sapphire wafers for mechanical property testing.

[0035] The Si wafer is a single-sided polished (100) crystal facet Si wafer with a length of 15mm, a width of 15mm, and a thickness of 0.5mm; the sapphire is a single-crystal C-facet sapphire wafer with a length of 15mm, a width of 15mm, and a thickness of 1mm.

[0036] S3: Vacuuming:

[0037] The cleaned substrate was placed on the substrate of the reaction chamber of the magnetron sputtering coating apparatus, and the reaction chamber was evacuated. The vacuum treatment was first performed using a mechanical pump to evacuate the vacuum until the vacuum level reached 8 × 10⁻⁶. -3 After Pa, a molecular pump is used to evacuate the vacuum until the vacuum level is less than 6 × 10⁻⁶. -4 Pa;

[0038] S4: Target cleaning:

[0039] The inert gas (Ar) flow rate was 20 sccm. When the chamber pressure was 0.1 Pa, three RF power supplies with a power of 50W were turned on for pre-sputtering treatment and the baffle was closed. The pre-sputtering treatment time was 30 min.

[0040] S5: Thin film preparation:

[0041] A Zr transition layer was deposited using a third RF power supply with a working pressure of 0.1 Pa and a power of 50 W. Then, a first RF power supply with a power of 180 W and a second RF power supply with a power of 10-30 W were used. A substrate bias voltage of 20 V was applied, and the substrate rotation speed was set to 5 rpm. Thin film preparation was then performed to obtain a (Zr, Ti)B2 composite film. The sputtering time was 2.5 hours, and the thickness of the composite film was 1.1 μm.

[0042] S6: Vacuum annealing

[0043] The (Zr,Ti)B2 composite film was subjected to a vacuum degree of less than 1×10⁻⁶. -3 An ultrahard thin film with low residual stress was obtained by annealing at 800°C for 1 hour under vacuum at Pa.

[0044] In this invention, Ti element mainly enhances film performance by forming (Zr,Ti)B2 solid solution, refining grains, improving film density, and regulating residual stress. At the same time, Ti generates stable oxidation products such as TiO2 during high-temperature friction and oxidation, which is beneficial to the formation of lubricating and protective films, thereby synergistically improving the film's hardness, wear resistance, and oxidation resistance.

[0045] The effects of the present invention will be illustrated below through examples and comparative examples.

[0046] Example 1

[0047] The preparation method of the present invention is as follows:

[0048] Step (1) Preparation of sputtering target

[0049] A zirconium diboride target is installed in the first RF power supply, a elemental titanium target in the second RF power supply, and a elemental zirconium target in the third RF power supply. The target specifications are: D75×3mm. The purity of the zirconium diboride, elemental titanium, and elemental zirconium targets is not less than 99.99%, and the target diameter is 75mm and the thickness is 3mm. The molar ratio of Zr, Ti, and B is 1:1:2.

[0050] Step (2) Substrate pretreatment

[0051] A single-crystal polished Si wafer with a (100) crystal facet is selected, with a length of 15mm, a width of 15mm, and a thickness of 0.5mm; a single-crystal sapphire wafer with a C-facet is selected, with a length of 15mm, a width of 15mm, and a thickness of 1mm.

[0052] Cleaning steps: Place the two substrates in acetone and anhydrous ethanol respectively for ultrasonic cleaning for 15 minutes each, and then dry them in an oven to obtain a contamination-free substrate.

[0053] Step (3) Vacuuming

[0054] The pretreated substrate is placed into the sputtering chamber of the magnetron sputtering coating system, and the mechanical pump evacuates the vacuum to 8 × 10⁻⁶. -3 After Pa, continue evacuation using a molecular pump to 6 × 10⁻⁶. -4 Below Pa.

[0055] Step (4) Target cleaning

[0056] Ar gas was introduced at a flow rate of 20 sccm, and the chamber pressure was controlled at 1.0 Pa. Three RF power supplies were turned on, each set to 50W, and the pre-sputtering time was set to 30 minutes, with the baffle closed.

[0057] Step (5) Thin film preparation

[0058] The working pressure was adjusted to 0.1 Pa. First, the baffle of the third RF power supply was turned on, and a Zr transition layer was deposited on the substrate surface with a power of 50 W. Then, the first RF power supply with a power of 180 W and the second RF power supply with a power of 30 W were turned on simultaneously. The substrate bias voltage was set to 20 V and the substrate rotation speed was set to 5 rpm. Sputtering was carried out for 2.5 h to obtain a (Zr, Ti)B2 composite film with a thickness of 1.1 μm.

[0059] Step (6) Vacuum annealing

[0060] The deposited film was placed in a tube furnace and annealed at 800°C for 60 min, with a vacuum level of less than 1×10⁻⁶. -3 Pa, to obtain an ultra-hard Ti alloyed zirconium diboride thin film with low residual stress.

[0061] The XRD pattern of the annealed zirconium diboride thin film in Example 1 is shown below. Figure 2 As shown. The test results show that obvious diffraction peaks at (001), (002), (101) and (311) can be observed in the XRD pattern of the annealed film, indicating that the obtained film has a polycrystalline structure.

[0062] Example 1: Residual stress testing method for composite films obtained on the surface of Si substrates, the method comprising:

[0063] The radius of curvature of the same region on the substrate before and after deposition was measured using a three-dimensional topology analyzer (BRUKER, Dektak-XT, Germany). The changes in radius of curvature were compared, and the residual stress of the ZrB2 thin film deposited on the single-crystal Si(100) wafer was calculated using the Stoney formula. The substrate's elastic modulus was 170 GPa, and its Poisson's ratio was 0.3. The test results are shown in Table 1 below.

[0064]

[0065] Table 1

[0066] Example 1: A method for testing the tribology of a composite thin film obtained on a sapphire substrate, the method comprising:

[0067] The test was conducted using a high-temperature friction and wear testing machine, and the specific parameters included:

[0068] Friction pair: Al2O3 balls, grinding ball diameter 9.38mm, friction mode is circular motion, normal load is 3N, holding time is 30s, fixture speed during test is 60r / min, circumferential friction radius is 4mm, heated to 600℃ using the equipment's built-in heating function, friction time is 20 minutes, test results are as follows. Figure 3As shown, the steady-state friction coefficient is 0.66, and the wear rate is 4.643 × 10⁻⁶. -5 mm 3 / N·mm.

[0069] Example 2

[0070] This embodiment explores the influence of different substrate materials. All other steps are exactly the same as in Example 1, with the following specific differences:

[0071] In step (2), the substrate is changed to a high-speed steel sheet (HRC). 60 The dimensions are 15×15×2.5mm. The surface of the high-speed steel is polished with 400#, 800#, 1200# and 2000# metallographic sandpaper in sequence, and then polished with diamond polishing paste to Ra<30nm.

[0072] The hardness and residual stress of the prepared superhard zirconium diboride thin film were tested using the same method as in Example 1. The test results were: hardness: 37.23 GPa, residual stress: 0.549.

[0073] Test results show that the preparation method of the present invention is applicable not only to sapphire substrates but also to high-speed steel substrates. The resulting composite film has good bonding performance with the substrate and can meet the application requirements of surface strengthening and high-temperature wear-resistant protection of tool materials.

[0074] Example 3

[0075] This embodiment investigates the effect of different Ti contents. The steps are basically the same as in Example 1, with the following specific differences:

[0076] In step (5), the Ti target power corresponding to the second RF power supply is set to 40W, and the remaining process parameters are the same as in Example 1.

[0077] Test results show that the composite film obtained in this embodiment can also form a (Zr,Ti)B2 solid solution structure. However, when the Ti content exceeds the solid solution limit, the excess Ti will form a Ti-related second phase or Ti enrichment. At the same time, the phase composition, microstructure uniformity and residual stress state of the film deviate from the optimal range, resulting in a decrease in hardness to 40.05 GPa and an increase in residual stress to 0.446 GPa.

[0078] Comparative Example 1

[0079] The steps in this comparative example are basically the same as those in Example 1, except that:

[0080] In step (5), the second RF power supply is not turned on, that is, the Ti source is not introduced. Only the first RF power supply is turned on with 180W power to deposit the ZrB2 thin film, and the Zr transition layer deposition and 800℃ vacuum annealing steps are retained. The remaining process parameters are the same as in Example 1.

[0081] The hardness and residual stress testing methods for the prepared ultrahard boride thin film were exactly the same as those in Example 1. The hardness of the pure ZrB2 film was 25.137 ± 0.5 GPa, the residual stress was 0.817 GPa, and the elastic modulus was 284.759 ± 5.7 GPa. Under high temperature conditions of 600℃, its coefficient of friction was 0.911, and its wear rate was 5.996 × 10⁻⁶. -5 mm 3 / N·mm. Test results show that compared with the boride film prepared in Example 1, the pure ZrB2 film obtained in this comparative example has poorer mechanical properties, oxidation resistance, and high-temperature tribological properties. Therefore, the introduction of Ti is beneficial to improving the overall performance of the film.

[0082] Comparative Example 2

[0083] The steps in this comparative example are basically the same as those in Example 1, except that:

[0084] The vacuum annealing process in step (6) is omitted, that is, the 800°C vacuum annealing is not performed after the deposition is completed, and the remaining steps are the same as in Example 1.

[0085] The hardness and residual stress testing methods of the prepared superhard boride thin film are exactly the same as those in Example 1. The test results show that, compared with the boride thin film prepared in Example 1, the boride thin film obtained in Comparative Example 2 has a larger surface roughness and a large number of point defects due to the lack of high-temperature annealing, resulting in high residual stress and poor toughness. The hardness is also slightly lower than that of Example 1.

[0086] Comparative Example 3

[0087] The steps in this comparative example are basically the same as those in Example 1, except that:

[0088] In step (5), no substrate bias is applied during the thin film deposition process, i.e., the substrate bias is 0V, and the remaining steps are the same as in Example 1.

[0089] The hardness and residual stress testing methods for the prepared ultrahard boride thin film were exactly the same as those in Example 1. The residual stress of the film obtained in this comparative example was 0.470 GPa, and the hardness was 36.42 GPa. The test results show that, compared with Example 1, the film obtained in this comparative example has poorer compactness, more grain boundary defects, and exhibits a loose columnar crystal structure. The residual stress state and microstructure uniformity are also poor, resulting in a decrease in film quality, hardness, and toughness.

[0090] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A low residual stress ultra-hard titanium alloyed zirconium diboride thin film, characterized in that, The components include Zr, Ti, and B, with a mass ratio of 1:1:

2.

2. A method for preparing a low residual stress ultra-hard titanium alloyed zirconium diboride thin film as described in claim 1, characterized in that, Includes the following steps: Step 1: Install the zirconium diboride target, elemental titanium target, and elemental zirconium target onto the three RF power supplies respectively; Step 2: Remove impurities from the substrate and place it on the rotating substrate in the reaction chamber of the magnetron sputtering coating apparatus; Step 3: Evacuate the reaction chamber to a vacuum level less than 6 × 10⁻⁶. -4 Pa; Inert gas is introduced until the pressure in the reaction chamber is 0.1 Pa; Pre-sputtering treatment is performed; Step 4: Set the substrate bias voltage to 20V and the substrate rotation speed to 5rpm; first turn on the RF power supply with the zirconium target mounted, and set the power to 50W to deposit a transition layer on the substrate surface; then simultaneously turn on the other two RF power supplies for sputtering to obtain a preliminary composite film on the substrate surface. The power of the RF power supply with the zirconium diboride target mounted is set to 180W; the power of the RF power supply with the titanium target mounted is set to a range of 10-30W. Step 5: Anneal the preliminary composite film prepared in Step 4 in a vacuum environment at 800℃ to obtain a superhard titanium alloyed zirconium diboride film with low residual stress.

3. The method for preparing a low residual stress ultra-hard titanium alloyed zirconium diboride thin film as described in claim 2, characterized in that, The purity of zirconium diboride targets, elemental titanium targets, and elemental zirconium targets is ≥99.99%.

4. The method for preparing a low residual stress ultra-hard titanium alloyed zirconium diboride thin film as described in claim 2, characterized in that, In step 2, the specific method for removing impurities from the substrate is as follows: the substrate is placed in acetone and anhydrous ethanol and cleaned by ultrasonication to remove impurities.

5. The method for preparing a low residual stress ultra-hard titanium alloyed zirconium diboride thin film as described in claim 2, characterized in that, In step 3, the specific method for evacuating the reaction chamber is as follows: First, a mechanical pump is used to evacuate the chamber until the vacuum level reaches 8 × 10⁻⁶. -3 After Pa, a molecular pump is used to evacuate the vacuum until the vacuum level is less than 6 × 10⁻⁶. -4 Pa.

6. The method for preparing a low residual stress ultra-hard titanium alloyed zirconium diboride thin film as described in claim 2, characterized in that, In step 3, the inert gas introduced is Ar, and the flow rate is 20 sccm.

7. The method for preparing a low residual stress ultra-hard titanium alloyed zirconium diboride thin film as described in any one of claims 2, 5, and 6, characterized in that, In step 3, the specific method for pre-sputtering is as follows: set the power of the three RF power supplies to 50W and perform pre-sputtering for 30 minutes.

8. The method for preparing a low residual stress ultra-hard titanium alloyed zirconium diboride thin film as described in claim 2, characterized in that, In step 4, the sputtering time is 2.5 hours; the thickness of the obtained preliminary composite film is 1.1 μm.

9. The method for preparing a low residual stress ultra-hard titanium alloyed zirconium diboride thin film as described in claim 2, characterized in that, In step 5, the annealing time is 1 hour; the vacuum level of the vacuum environment is less than 1×10⁻⁶. -3 Pa.

10. The application of a low residual stress ultra-hard titanium alloy zirconium diboride thin film as described in claim 1 in thermal protection systems and machining fields.

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