Delta-MoN-containing molybdenum nitride-based coating as well as preparation method and application thereof

Abstract

The invention discloses a molybdenum nitride-based coating containing delta-MoN. In the molybdenum nitride-based coating containing delta-MoN, the content of Mo is 45-60 at.%, the content of N is 30-45 at.%, and the content of Cu is 0-15 at.%. The method has the following advantages and effects that the delta-MoN molybdenum nitride-based coating is easy to oxidize, a lubricating and friction reducing friction film is rapidly formed, MoCu04 easier to shear can be formed through introduction of the Cu element, the lubricating property and the high-temperature stability are better, and the problem that Mo03 is easy to volatilize at a high temperature is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating technology, in particular to a δ-MoN-containing molybdenum nitride-based coating and a preparation method and application thereof. BACKGROUND

[0002] Wear is the main reason affecting the service life of parts. In order to ensure the efficient and reliable operation and long service life of parts such as aerospace, microelectronic devices and automobile engine pistons, the requirements for the friction and wear performance of moving parts are increasingly stringent, especially under dry friction and large temperature fluctuation conditions. With the industrial transformation and upgrading of China, the traditional oil lubrication method has limitations in many cases. For example, in special environments such as high / low temperature alternation and high vacuum, oil lubrication is prone to failure.

[0003] For example, parts near the engine are subjected to large mechanical and thermal loads during operation, which are prone to thermal fatigue cracking and wear under this working condition. The lubricating oil deteriorates at high temperatures, leading to further aggravation of wear, and even adhesion of parts. Due to the extremely harsh service conditions, many engineering materials still need to maintain good mechanical properties and wear-resistant lubrication properties at 300 to 400 DEG C to ensure reliable operation and efficient transmission. How to improve the service life and operational reliability of engineering equipment at medium temperatures where oil lubrication fails is a serious constraint on its development.

[0004] Low-friction DLC and MoS2 coatings are prone to oxidation and decomposition at high temperatures, and DLC films have high stress and poor film / substrate adhesion, which are prone to failure under impact and vibration. MoN-based self-lubricating coatings have excellent mechanical properties and chemical stability, and can form a layered and easily sheared MoO3 lubricating phase during friction, which can provide good lubrication at room temperature and high temperature environments. Currently, wear-resistant protective coatings can easily achieve good lubrication at high temperatures, and molybdenum nitride-based coatings also have excellent lubrication properties at room temperature, but the friction coefficient at medium temperatures is still high, making it difficult to develop wear-resistant and lubricated protective coatings in a wide temperature range. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a δ-MoN-containing molybdenum nitride-based coating and a preparation method and application thereof. The technical solutions adopted are as follows.

[0006] The δ-MoN-containing molybdenum nitride-based coating provided in the present application contains 45-60 at.% Mo, 30-45 at.% N and 0-15 at.% Cu.

[0007] In some embodiments of the present application, at least part of the Cu exists in the form of solid solution in the molybdenum nitride lattice.

[0008] In some embodiments of this application, the cross-section of the δ-MoN molybdenum nitride-based coating exhibits an amorphous growth morphology.

[0009] In some embodiments of this application, the Cu content of the δ-MoN molybdenum nitride-based coating is 0-5 at.%.

[0010] This application also provides a method for preparing the aforementioned δ-MoN molybdenum nitride-based coating, comprising the following steps: S1, Polish and clean the substrate, and load the substrate into the reaction chamber; S2, the reaction chamber is evacuated and heated, and the substrate surface is subjected to glow discharge cleaning and Cr ion etching; S3 uses a HiPIMS power supply with a power of 2 to 10 kW, a frequency of 200 to 500 Hz, and a pulse width of 100 to 250 μs to sputter a MoCu target and deposit a MoN-Cu coating in a mixed atmosphere of inert gas and nitrogen; wherein the MoCu target is a planar target and the Mo target has through holes for placing Cu pillars.

[0011] In some embodiments of the preparation method of this application, during the glow discharge cleaning process in step S2, the reaction chamber is heated to 400 to 500°C and evacuated to a vacuum of 4*10. -3 Up to 7*10 -3 Pa; the temperature of the reaction chamber is adjusted to 350 to 450℃, the substrate bias voltage is set to -800 to -1200V, the flow rate of the inert gas is 200 to 300 sccm, the gas pressure of the reaction chamber is 2.0 Pa, and the substrate is subjected to glow discharge cleaning.

[0012] In some embodiments of the preparation method of this application, during the Cr ion etching process in step S2, the inert gas flow rate is 50 to 100 sccm, the substrate bias voltage is -600 to -800 V, the target current is 60 to 100 A, and the substrate is bombarded by Cr evaporation using a cathode arc.

[0013] In some embodiments of the preparation method of this application, in step S3, the temperature of the reaction chamber is 350 to 450°C, and inert gas and nitrogen are introduced, wherein nitrogen accounts for 30% to 60% of the total pressure of the mixed gas.

[0014] In some embodiments of the preparation method of this application, the gas pressure in the reaction chamber is 0.4 to 0.8 Pa, and the substrate bias voltage is -50 to -250 V.

[0015] The δ-MoN molybdenum nitride-based coating provided in this application is used in the field of wear resistance and protection.

[0016] This application has at least the following beneficial effects: This application aims to provide a nitride coating with excellent wear-resistant and lubricating properties at medium to high temperatures where oil lubrication fails. The MoN-Cu coating containing δ-MoN can play a role in lubrication and friction reduction.

[0017] In this application, the coating rapidly forms a lubricating and friction-reducing friction film due to the easy oxidation of δ-MoN. Furthermore, the introduction of Cu allows for the formation of more easily sheared MoCuO4, resulting in better lubricity and high-temperature stability, thus solving the problem of MoO3's easy volatilization at high temperatures. During friction at 400℃, the MoN coating forms an amorphous enamel oxide layer, and due to oxide adhesion, the surface friction film exhibits poor lubrication performance, resulting in a high coefficient of friction at this temperature. However, by inducing a phase transformation in the coating through Cu doping to form δ-MoN, its rapid oxidation can further optimize the coating's coefficient of friction at medium and low temperatures.

[0018] This application utilizes the high ionization rate of Cu in the HiPIMS process to promote grain refinement and drive phase transformation to form δ-MoN with a small amount of Cu. A dense coating can be obtained under the competitive growth of two phases and the influence of a small amount of Cu.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] The present application will be further illustrated below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments illustrated in the following drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application.

[0021] Figure 1 This is a schematic diagram of the target substrate during the deposition process.

[0022] Figure 2 The surface and cross-sectional morphology and EDS composition are shown in (a) the embodiment and (b) the comparative example.

[0023] Figure 3 GIXRD is used for both examples and comparative examples.

[0024] Figure 4 The hardness and elastic modulus are for the examples and comparative examples.

[0025] Figure 5 The scratch test results are for the examples and comparative examples.

[0026] Figure 6 The friction coefficient curves are for the examples and comparative examples.

[0027] Figure 7 The average coefficient of friction and wear rate are for the examples and comparative examples.

[0028] Figure 8 The wear track cross-sectional curves are for (a) the comparative example and (b) the embodiment.

[0029] Figure 9 Raman spectral analysis of the wear marks in (a) the comparative example and (b) the embodiment. Detailed Implementation

[0030] The technical solutions described in this invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described in this specification are only some feasible technical solutions of this invention. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without any creative effort should be considered to fall within the scope of protection of this invention.

[0031] This application relates to a wear-resistant and lubricating δ-MoN molybdenum nitride-based coating. The coating surface is smooth and dense, and the cross-section exhibits an amorphous growth morphology. The δ-MoN molybdenum nitride-based coating contains 45-60 at.%, 30-45 at.%, and 0-15 at.% Mo, N, and Cu. The coating is prepared using the HiPIMS physical vapor deposition method.

[0032] The coating phase structure is mainly δ-MoN, which is easily oxidized during friction to form a lubricating phase, giving the coating excellent wear resistance and friction reduction properties.

[0033] The high ionization rate of Cu under HiPIMS conditions and the solid solution of a small amount of Cu promote the grain refinement of thin films and drive the formation of δ-MoN.

[0034] It should be noted that when the Cu content is less than 5 at.%, Cu mainly exists in the molybdenum nitride lattice in solid solution form, thus driving the formation of δ-MoN under HiPIMS conditions. When the Cu content continues to increase, Cu exists in an amorphous form at the grain boundaries, forming a nanocomposite structure. However, excessively high Cu content will reduce the mechanical and tribological properties of the coating.

[0035] This application relates to the application of a δ-MoN molybdenum nitride-based coating, which is used in the field of wear-resistant protection.

[0036] This application relates to a preparation method for depositing a wear-resistant and lubricating molybdenum nitride-based coating containing δ-MoN.

[0037] The preparation method includes the following process flow: S1, Polish and clean the substrate, and load the substrate into the reaction chamber.

[0038] S2, the reaction chamber is evacuated and heated, and the substrate surface is subjected to glow discharge cleaning and Cr ion etching.

[0039] S3 uses a high-power pulsed magnetron sputtering MoCu target to deposit a MoN-Cu coating in a mixed atmosphere of inert gas and nitrogen.

[0040] It should be noted that during the glow discharge cleaning process in step S2, the reaction chamber is heated to 400 to 500°C and evacuated to a vacuum of 4*10. -3 Up to 7*10 -3 Pa; the temperature of the reaction chamber is adjusted to 350 to 450℃, the substrate bias voltage is set to -800 to -1200V, the flow rate of the inert gas is 200 to 300 sccm, the gas pressure of the reaction chamber is 2.0 Pa, and the substrate is subjected to glow discharge cleaning.

[0041] In step S2, the glow discharge cleaning time is 20 minutes.

[0042] Furthermore, during the Cr ion etching process in step S2, the inert gas flow rate is 70 sccm, the substrate bias voltage is -800V, the target current is 60 to 100A, and the substrate is bombarded by Cr evaporation using a cathode arc.

[0043] During ion etching of the substrate surface, the target-substrate distance is 15 to 25 cm. If the target-substrate distance is too small during etching, the etching will be too strong, causing defects in the substrate and which is not conducive to the bonding force; if it is too large, the etching effect will be poor and it will not be able to effectively remove contaminants from the substrate surface or activate the substrate.

[0044] In step S2, the ion etching time is 3 to 8 minutes.

[0045] In step S3, during the coating deposition process, the temperature of the reaction chamber is 350 to 450°C, and inert gas and nitrogen are introduced, with nitrogen accounting for 30% to 60% of the total mixed gas pressure. The gas pressure in the reaction chamber is 0.4 to 0.8 Pa, and the substrate bias voltage is -50 to -250 V. Excessive nitrogen will poison the target material, reduce the deposition rate, and even cause arcing on the target surface; insufficient nitrogen will cause the formation of a metallic phase in the prepared coating, which is detrimental to its hardness and tribological properties; excessively high chamber pressure is not conducive to magnetron sputtering and will also result in an insufficiently dense MoN-Cu coating.

[0046] HiPIMS power supplies range from 2 to 10 kW in power, 200 to 500 Hz in frequency, and 100 to 250 μs in pulse width. The frequency and pulse width determine the duty cycle. A smaller duty cycle results in a higher ionization rate of the sputtered particles from the target, which affects the ionization rate of Cu during thin film deposition. A higher Cu ionization rate facilitates migration and diffusion on the substrate, reducing the likelihood of agglomeration and leading to grain refinement and film densification.

[0047] In step S3, the target-substrate distance is 8 to 12 cm. If the target-substrate distance is too large, it will reduce the deposition rate and the energy of the film-forming particles. When the energy is low, their migration and diffusion are more difficult, thus causing the coating to become dense and its performance to decline. If the target-substrate distance is too small, the substrate will affect the magnetic field near the target surface. The sharp edges of the substrate may cause arcing. In addition, excessive bombardment will lead to an increase in defects and excessive stress in the film.

[0048] It should be noted that the deposition time in step 3 is 120 minutes.

[0049] The MoCu target used in high-power pulsed magnetron sputtering is a planar target with through holes for placing Cu pillars.

[0050] Ar is used as the inert gas in this application.

[0051] In this application, Cu doping under HiPIMS conditions drives the formation of δ-MoN in the coating. Simultaneously, the high ionization rate of Cu under the HiPIMS process promotes grain refinement, preventing agglomeration between Cu and MoN due to poor wettability, resulting in a high-performance, smooth, and dense coating. δ-MoN is more easily oxidized to form a lubricating phase, thus further optimizing the dry friction coefficient of the coating at medium and low temperatures. Furthermore, at higher temperatures, Cu and MoO3 form the thermally more stable lubricating phase MoCuO4, which continues to provide lubrication, effectively improving the lubrication performance of the molybdenum nitride-based coating during dry friction at medium and low temperatures.

[0052] The performance of the δ-MoN molybdenum nitride-based coating in this application is described in detail below with reference to specific embodiments. It should be noted that the following description is only illustrative and not a specific limitation of this application.

[0053] Example The preparation method of δ-MoN molybdenum nitride-based coatings includes the following process flow, and a schematic diagram of the target and substrate during thin film deposition is shown below. Figure 1 As shown.

[0054] S1, Evacuate the reaction chamber to 7*10 -3 After the vacuum level reaches the set value, the Ar flow rate is set to 300 sccm, the substrate surface is subjected to glow discharge cleaning, the gas pressure in the reaction chamber is 2.0 Pa, the substrate bias voltage is set to -1000 V, and the duration is 20 min.

[0055] S2, the temperature of the reaction chamber is adjusted to 350℃, the Ar flow rate is adjusted to 100sccm, the gas pressure of the reaction chamber is 0.7Pa, the substrate is directly facing the Cr target, the target-substrate distance is 15cm, the substrate bias voltage is -800V, the target current is 80A, and the Cr target is bombarded with the substrate surface by cathode arc evaporation for 5min.

[0056] S3, turn on the HiPIMS power supply for the MoCu target, introduce Ar gas at 40 sccm and nitrogen gas at 60 sccm into the reaction chamber, set the gas pressure in the reaction chamber to 0.6 Pa, the substrate bias voltage to -100 V, the HiPIMS power supply to 4 kW, the frequency to 300 Hz, the pulse width to 150 μs, and the deposition time to 120 min.

[0057] A MoN-Cu coating was prepared.

[0058] Comparative Example The preparation method of molybdenum nitride coating includes the following process flow.

[0059] R1, the reaction chamber is evacuated to 7*10. -3 After the vacuum level reaches the set value, the Ar flow rate is set to 300 sccm, the substrate surface is subjected to glow discharge cleaning, the gas pressure in the reaction chamber is 2.0 Pa, the substrate bias voltage is set to -1000 V, and the duration is 20 min.

[0060] R2, the temperature of the reaction chamber is adjusted to 350℃, the Ar flow rate is adjusted to 70sccm, the substrate is directly facing the Cr target, the target-substrate distance is 25cm, the substrate bias voltage is -800V, the target current is 80A, and the Cr is evaporated by cathode arc to bombard the substrate surface for 5min.

[0061] R3, turn on the HiPIMS power supply for the Mo target, introduce Ar gas at 40 sccm and nitrogen gas at 60 sccm into the reaction chamber, set the gas pressure in the reaction chamber to 0.6 Pa, the substrate bias voltage to -100 V, the HiPIMS power supply to 2 kW, the frequency to 300 Hz, the pulse width to 150 μs, and the deposition time to 120 min.

[0062] A MoN coating was prepared.

[0063] Performance testing: The MoN-Cu coating and MoN coating prepared in the above embodiments were tested using the following methods.

[0064] 1. The surface and cross-sectional morphology of the coating were analyzed using SEM (SEM; Hitachi SU8220) and EDS (EDS; Oxford Instruments X-Max). N )Analyze the composition of the coating, such as Figure 2 As shown.

[0065] As can be seen, the comparative example without Cu exhibits a distinct columnar crystal growth morphology, with fine columnar crystal particles on the surface. However, after Cu doping of 3.8 at.%, the example exhibits an amorphous growth morphology, while the surface becomes denser and smoother.

[0066] 2. The phase structure of the coating was analyzed using XRD (GIXRD; Bruker D8 Advance) at an incident angle of 1° to avoid interference from matrix diffraction peaks. The test results are as follows: Figure 3 As shown.

[0067] Compared to the comparative example, the phase structure of the Cu-doped example changed significantly, forming δ-MoN with the 200 plane as the preferred orientation. At the same time, the diffraction peaks of fcc-Mo2N were significantly broadened due to grain refinement. The grain refinement was caused by Cu doping on the one hand, and by the competitive growth of the two phases on the other.

[0068] 3. Using nanoindentation (Anton Paar TTX-NHT) 2 )Analyze the mechanical properties of the coating, such as Figure 4 As shown.

[0069] Compared to the comparative example, the hardness of the embodiment is improved, but its elastic modulus is smaller, resulting in a larger H / E value. This indicates better toughness, which may also be beneficial to its wear resistance. The increase in hardness is due to both the solid solution of Cu and the composite structure of the two phases.

[0070] 4. The Anton Pare Revetest scratch tester is used to characterize the adhesion strength between the coating and the substrate. Good adhesion is essential to ensure that the film can perform its functions. Figure 5 As shown.

[0071] The scratch results show that the Cu-doped embodiment has better bonding with the substrate. Arc-shaped cracks only appear inside the scratch under a large scratch force, and continuous peeling of the film only occurs at the scratch edge at 86.2 N.

[0072] 5. Friction coefficient test, as follows Figure 6 As shown: Tests were conducted using a ball-and-disc high-temperature friction and wear testing machine (Anton Paar HT1000) under conditions of room temperature, 45% humidity, and 400℃. The grinding balls were Al2O3 balls, the load was 2N, and the friction radius was 2mm. Wear rate test: After friction under these conditions, the cross-section of the wear track was detected using laser confocal microscopy (Olympus OLS4100). The wear track volume was calculated by averaging the cross-sectional areas of five wear points. The wear amount V was obtained using the formula V=A*2πr, and the wear rate was calculated using the formula W=V / (P*L), where L is the friction distance.

[0073] The average coefficient of friction and wear rate of the wear-resistant lubricating coatings in the examples and comparative examples at room temperature and 400°C are as follows: Figure 7 As shown, the coefficient of friction at room temperature is 0.32, and the wear rate is 6.4 × 10⁻⁶. -8 mm 3 / (N×m), comparable to DLC; the coefficient of friction reaches 0.34 at 400°C. Compared with most coatings, the coating in this example exhibits good lubrication performance at this temperature, and the wear rate is 6.4×10. -7 mm 3 / (N×m), exhibiting excellent wear resistance. At this temperature, the comparative sample has a friction coefficient of 0.54. This is because the adhesion within the wear track results in relatively low wear, and this adhesion also contributes to its higher friction coefficient. The introduction of Cu element also helps to improve adhesion during high-temperature friction and contributes to reducing the friction coefficient.

[0074] After a friction test at 400℃, the cross-sectional curve of the wear track at a certain point is as follows: Figure 8 As shown, the coating exhibits a very low wear rate at this temperature compared to the thin film, demonstrating excellent wear resistance.

[0075] 6. Raman spectroscopy (LabRAM HR Evolution 532nm lasers) was used to detect the oxidation products formed on the sample surface after the friction experiment, such as... Figure 9 As shown.

[0076] As can be seen from the figure, the oxidation degree on the sample surface of the comparative example and the embodiment is roughly the same, but the oxide MoO3 formed in the wear track of the embodiment is more abundant. This is because δ-MoN is more easily oxidized to form a lubricating phase than fcc-Mo2N, and therefore more lubricating phase is formed under the action of tribochemical reaction.

[0077] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

Claims

1. A molybdenum nitride-based coating containing δ-MoN, characterized in that: The δ-MoN molybdenum nitride-based coating contains 45-60 at.% Mo, 30-45 at.% N, and 0-15 at.% Cu.

2. The δ-MoN molybdenum nitride-based coating according to claim 1, characterized in that: At least a portion of Cu exists in solid solution form within the molybdenum nitride lattice.

3. The δ-MoN molybdenum nitride-based coating according to claim 2, characterized in that: The cross-section of the δ-MoN molybdenum nitride-based coating exhibits an amorphous growth morphology.

4. The δ-MoN molybdenum nitride-based coating according to claim 1, characterized in that: The Cu content of the δ-MoN molybdenum nitride-based coating is 0-5 at.%.

5. A method for preparing a δ-MoN molybdenum nitride-based coating as described in any one of claims 1-4, characterized in that, Includes the following steps: S1, Polish and clean the substrate, and load the substrate into the reaction chamber; S2, the reaction chamber is evacuated and heated, and the substrate surface is subjected to glow discharge cleaning and Cr ion etching; S3, using a HiPIMS power supply with a power of 2 to 10 kW, a frequency of 200 to 500 Hz, and a pulse width of 100 to 250 μs to sputter a MoCu target, depositing a MoN-Cu coating in a mixed atmosphere of inert gas and nitrogen; wherein, the MoCu target is a planar target, and the Mo target has through holes for placing Cu pillars.

6. The method for preparing a δ-MoN molybdenum nitride-based coating according to claim 5, characterized in that: During the glow discharge cleaning process in step S2, the reaction chamber is heated to 400 to 500°C and evacuated to a vacuum of 4*10. -3 Up to 7*10 -3 Pa; the temperature of the reaction chamber is adjusted to 350 to 450℃, the substrate bias voltage is set to -800 to -1200V, the flow rate of the inert gas is 200 to 300 sccm, the gas pressure of the reaction chamber is 2.0 Pa, and the substrate is subjected to glow discharge cleaning.

7. The method for preparing a δ-MoN molybdenum nitride-based coating according to claim 6, characterized in that: During the Cr ion etching process in step S2, the inert gas flow rate is 50 to 100 sccm, the substrate bias voltage is -600 to -800V, the target current is 60 to 100A, and the substrate is bombarded by Cr evaporation using a cathode arc.

8. The method for preparing a δ-MoN molybdenum nitride-based coating according to claim 7, characterized in that: In step S3, the temperature of the reaction chamber is 350 to 450°C, and inert gas and nitrogen are introduced, wherein nitrogen accounts for 30% to 60% of the total pressure of the mixed gas.

9. The method for preparing a δ-MoN molybdenum nitride-based coating according to claim 8, characterized in that: The gas pressure in the reaction chamber is 0.4 to 0.8 Pa, and the substrate bias voltage is -50 to -250 V.

10. An application of a δ-MoN molybdenum nitride-based coating, characterized in that: The δ-MoN molybdenum nitride-based coating according to any one of claims 1-4 is applied to the field of wear-resistant protection.

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