Gradient diamond / molybdenum disulfide composite self-lubricating wear-reducing engineering ceramic coating and preparation method thereof

Abstract

The application discloses a gradient diamond / molybdenum disulfide composite self-lubricating wear-reducing engineering ceramic coating and a preparation method thereof, belongs to the technical field of full ceramic self-lubricating wear-resistant coatings, and the coating is sequentially formed of a multi-stage size progressive diamond coating and a molybdenum disulfide coating from the surface of an engineering ceramic substrate to the outside. The multi-stage size progressive diamond coating comprises a micron diamond coating, a fine-grained diamond coating and a nano diamond coating, and the molybdenum disulfide coating is deposited on the diamond coating. The diamond coating is prepared by using a hot-wire chemical vapor deposition method, and the molybdenum disulfide film covering the diamond coating is prepared by using a direct-current magnetron sputtering method. Under certain conditions, the molybdenum disulfide in the composite coating reacts with the nano diamond and is converted into onion-like carbon, so that the hardness and lubricating performance of the composite coating are improved, and the friction and wear are reduced. The composite coating prepared by using the method has more stable bonding force and adhesion, and the service life of a machine is improved.

Description

Technical Field

[0001] This invention belongs to the field of all-ceramic self-lubricating wear-resistant coating technology, specifically relating to a gradient diamond / molybdenum disulfide composite self-lubricating friction-reducing engineering ceramic coating and its preparation method. Background Technology

[0002] All-ceramic bearings are bearings made primarily of ceramic. They possess excellent properties such as high wear resistance, low coefficient of friction, corrosion resistance, insulation, self-lubrication, and plasticity, making them widely applicable in aerospace, automotive, medical equipment, electronics, military equipment, industrial robots, and various high-tech fields and harsh environments. However, prolonged operation of all-ceramic bearings in high-temperature conditions with hard dust, acid, alkali, and salt corrosive substances increases friction, reduces service life and lubrication stability, and has become a concern in related research fields. Molybdenum disulfide has extremely high self-lubricating properties, as well as high wear resistance, high pressure resistance, low coefficient of friction, corrosion resistance, antimagnetism, and economy, making it widely used in machinery manufacturing. While diamond coatings possess certain frictional properties and hardness, their lubrication performance declines over time and under harsh environmental conditions. Adding appropriate elements to alter their internal structure through reactions can create unique and superior properties, profoundly impacting research on the friction and wear of all-ceramic bearings and their application in high-tech fields.

[0003] While research on self-lubricating coatings for ceramic friction pairs continues, studies on composite self-lubricating coatings combining a hard coating and a self-lubricating material are currently limited. For example, patent CN108677144B discloses a method for preparing aluminum-nitrogen co-doped diamond-like carbon (DLC) composite films. This method uses ion-assisted cathodic arc deposition (IAAC) to achieve sputtering deposition on the workpiece surface, obtaining a compositionally controllable aluminum-nitrogen co-doped DLC composite film. Although this method solves the hardness problem of hard DLC films, its lubrication performance is poor. Another example is patent CN102994947B, which uses dual-target magnetron sputtering to alternately deposit DLC and molybdenum disulfide layers on a stainless steel substrate, ultimately obtaining a DLC composite molybdenum disulfide nanolayered film. The coating prepared by this deposition method has low adhesion and poor quality, only addressing the brittleness of hard DLC films on metal substrates. Under cyclic impact stress, it will be damaged due to insufficient adhesion. Under various harsh working conditions, insufficient hardness and toughness, weak adhesion, and fatigue can lead to the failure of the coating friction pair. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to modify the original precipitation technology to solve problems such as low surface hardness, uneven coating, insufficient hardness, weak adhesion, and poor lubrication effect caused by the composite material itself in existing self-lubricating coatings. This invention provides a gradient diamond / molybdenum disulfide composite self-lubricating friction-reducing engineering ceramic coating and its preparation method. The coating prepared by this method consists of a multi-level diamond coating and a single-layer molybdenum disulfide coating, arranged sequentially from the surface of the engineering ceramic substrate outwards. Each level of the diamond coating includes a micron-sized diamond coating, a fine-grained diamond coating, and a nano-diamond coating. A single-layer molybdenum disulfide coating is deposited on top of the diamond coating, and some of the nano-diamond coating is converted into an onion-like carbon structure.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The deposited diamond coating was prepared using hot-wire chemical vapor deposition (CVD). Silicon carbide ceramic was used as the research object. Micron-sized diamond films were prepared on the surface of the ceramic substrate by hot-wire CVD. Then, by changing the deposition parameters (hydrogen flow rate, methane flow rate, and deposition time), fine-grained diamond films and nano-diamond films were successively prepared. The deposition of diamond films on the ceramic substrate surface by hot-wire CVD can significantly improve the film-substrate bonding force. For pores and microcracks formed on the ceramic surface, the diamond film coating can also compensate for ceramic surface defects and improve the surface hardness and smoothness of the ceramic substrate.

[0007] To achieve the structural transformation of nanodiamond and molybdenum disulfide coating into onion-like carbon, an annealing method is used, controlling the annealing time and temperature to achieve the desired result, which can greatly improve the hardness and wear resistance of the composite coating.

[0008] The molybdenum disulfide coating was prepared by PVD DC magnetron sputtering technology. The molybdenum disulfide coating was obtained by optimizing the process parameters. The composite coating can achieve extremely high self-lubricating properties.

[0009] A gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating is composed of a first-order size progressive diamond coating and a molybdenum disulfide coating. Its structure is as follows: from the surface of the silicon nitride ceramic substrate outward, there are first-order size progressive diamond coatings and molybdenum disulfide coatings.

[0010] The structure of the first-order size-progressive diamond coating, from the surface of the ceramic substrate to the outside, consists of: 3 layers of micron-sized diamond coating, 1 layer of fine-grained diamond coating, and 1 layer of nanocrystalline diamond coating. The grain size of diamond in each adjacent diamond coating decreases sequentially. There is an onion-like carbon structure between the nanocrystalline diamond coating and the molybdenum disulfide coating.

[0011] In the three-layer micron-crystalline diamond coating, the diamond grain size from the surface of the silicon nitride substrate outwards is as follows: the first layer of diamond coating has a diamond grain size of 2.4–3 μm and an average grain size of 2.6–2.8 μm; the second layer of diamond coating has a diamond grain size of 1.7–2.4 μm and an average grain size of 1.9–2.1 μm; and the third layer of diamond coating has a diamond grain size of 1–1.7 μm and an average grain size of 1.2–1.4 μm.

[0012] In the fine-grained diamond coating, the diamond grain size is 0.2–1 μm, and the average grain size is 0.4–0.8 μm;

[0013] In the nanocrystalline diamond coating, the diamond grain size is 20-200 nm, and the average grain size is 90-130 nm.

[0014] In the molybdenum disulfide coating, the molybdenum disulfide grain size is 30-60 nm, and the average grain size is 40-50 nm.

[0015] The total thickness of the first-order dimension-progressive diamond coating is 2.7–3 μm, and the total thickness of the molybdenum disulfide coating is 40–100 nm.

[0016] The gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating has a hardness of 4–15 GPa and a friction coefficient of 0.05–0.1.

[0017] The preparation method of the above-mentioned gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating adopts CVD hot-wire chemical vapor deposition and PVD magnetron sputtering, respectively, and specifically includes the following steps:

[0018] Step 1: Pretreatment of engineering ceramic substrate

[0019] The surface of the engineering ceramic substrate is roughened by micro-treatment, and then cleaned and dried to obtain the treated engineering ceramic substrate.

[0020] Step 2: Deposit diamond coating

[0021] The surface-treated engineering ceramic substrate is placed on the chamber stage of the hot filament chemical vapor deposition apparatus, and a first-order size progressive diamond coating is deposited and grown on the surface of the surface-treated engineering ceramic substrate.

[0022] Step 3: Annealing

[0023] The diamond-deposited engineering ceramic substrate is placed in a tube furnace, heated for a period of time, cooled to room temperature and removed to obtain a sample with an onion-like carbon structure on the surface for later use.

[0024] Step 4; Deposition of molybdenum disulfide coating

[0025] The annealed engineering ceramic substrate was placed in the cavity of a DC magnetron sputtering equipment to begin depositing a molybdenum disulfide coating. After deposition, the sample film was removed, and a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating was finally obtained.

[0026] In step 1, the method for roughening the engineering ceramic substrate is diamond micron grinding.

[0027] In step 1, the roughening micro-processing uses 0.5μm diamond polishing paste.

[0028] In step 1, the cleaning method is ultrasonic cleaning, and the drying method is nitrogen blowing.

[0029] In step 2, the hot wire in the hot filament chemical vapor deposition apparatus is tantalum wire.

[0030] In step 2, the deposition process parameters for the diamond coating are as follows: chamber pressure is 3.5–4 kPa, hot filament temperature is 2100–2200 °C, surface-inoculated engineering ceramic substrate temperature is 800–850 °C, the distance between the hot filament and the upper surface of the surface-inoculated engineering ceramic substrate is 10–15 mm, deposition time is 0.45–1 h, methane:hydrogen ratio is (1–5):100, hydrogen flow rate is 400–600 sccm, methane flow rate is 4–30 sccm, and current is 95–100 A.

[0031] When depositing microcrystalline diamond coatings, the methane / hydrogen volume concentration ratio R is adjusted. 微米 For: 1% ≤ R 微米 <3%;

[0032] When depositing a fine-grained diamond coating, adjust the methane / hydrogen volume concentration ratio R. 细晶粒 For: 3% ≤ R 细晶粒 <4%;

[0033] When depositing a nanocrystalline diamond coating, the methane / hydrogen volume concentration ratio R is adjusted. 纳米 For: 4% ≤ R 纳米 <5%;

[0034] During the growth of the microcrystalline diamond coating, the methane / hydrogen volume concentration ratio R of the first layer is controlled. 微1 For: 1% ≤ R 微1 <1.7%, second layer methane / hydrogen volume concentration R 微2 For: 1.7% ≤ R 微2 <2.4%, third layer methane / hydrogen volume concentration ratio R 微3 For: 2.4% ≤ R 微3 <3%.

[0035] In step 3, the specific steps of annealing are as follows:

[0036] (1) Mix nano-diamond powder and molybdenum disulfide powder together at a ratio of (7-8):1;

[0037] (2) Mix the well-mixed powder with glycerin and coat it evenly on the surface of the diamond sample. Then place it in a tube furnace and heat it at a rate of 20-30℃ / min to an annealing temperature of 1700-2000℃ for 0.8-1h. After the annealing is completed, cool the annealed sample to room temperature under an argon atmosphere and then take it out for use.

[0038] In step 4, the DC magnetron sputtering deposition process parameters for the molybdenum disulfide coating are as follows: sputtering pressure is 1-2 Pa, sputtering power is 30-100 W, target-to-substrate distance is 10-13 cm, sputtering temperature is 380-420 °C, and sputtering time is 0.4-0.5 h.

[0039] The gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating and its preparation method of the present invention have the following beneficial effects:

[0040] (1) Compared with existing self-lubricating coatings, the composite self-lubricating coating of the present invention has a higher quality coating. The coating is composed of molybdenum disulfide, which has a lower coefficient of friction and ultra-high self-lubricating performance, reducing friction loss and improving mechanical efficiency.

[0041] (2) In the composite coating of the present invention, the diamond coating is prepared by CVD hot filament chemical vapor deposition technology, and the molybdenum disulfide coating is prepared by PVD DC magnetron sputtering technology. The gradient diamond / molybdenum disulfide composite coating is prepared on the surface of engineering ceramics. It has high surface quality and has the advantages of being dense, uniform and having strong adhesion.

[0042] (3) Under the same working conditions, the composite self-lubricating coating prepared on the surface of engineering ceramics by the preparation method of the present invention can effectively improve the service life of engineering ceramic materials. During the periodic use of engineering all-ceramic bearings, the coating will not peel off on the surface of the friction pair, the friction is stable, and it can exhibit extremely high self-lubricating friction and wear performance.

[0043] (4) The structure between the nanodiamond coating and the molybdenum disulfide coating can react under certain conditions. The diffusion of sulfur in the molybdenum disulfide will increase the strain of the nanodiamond, destroy it and convert it into onion-shaped carbon, which has high hardness and wear resistance.

[0044] (5) The gradient diamond / molybdenum disulfide composite self-lubricating and wear-reducing engineering ceramic coating prepared by the present invention has good hardness, lubricity, adhesion and wear resistance. Attached Figure Description

[0045] Figure 1 In this embodiment of the invention, a schematic diagram of the hot filament chemical vapor deposition apparatus is shown; wherein: 1-bell jar, 2-vacuum chamber, 3-stage, 4-pressure gauge, 5-cooling water, 6-hot filament, 7-substrate, 8-substrate stage, 9-electrode, 10-thermocouple, 11-power supply, 12-vacuum pump, 13-reaction gas;

[0046] Figure 2 In this embodiment of the invention, a schematic diagram of the structure of a DC magnetron sputtering device is shown; wherein: 1-target stage, 2-substrate, 3-cooling water, 4-argon gas inlet, 5-pressure gauge, 6-vacuum system, 7-substrate stage, 8-bell jar. Detailed Implementation

[0047] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

[0048] In this embodiment of the invention, a schematic diagram of the hot-filament chemical vapor deposition apparatus used for diamond coating deposition is shown below. Figure 1 As shown, its structure includes: 1-bell jar, 2-vacuum chamber, 3-worktable, 4-barometer, 5-cooling water, 6-hot wire, 7-substrate, 8-substrate worktable, 9-electrode, 10-thermocouple, 11-power supply, 12-vacuum pump, 13-reaction gas. The specific steps are as follows:

[0049] (1) Turn on the chiller to start circulating the cooling water;

[0050] (2) Turn on the HFCVD equipment to vent until the chamber door is open, arrange the tantalum wire properly, adjust the process parameters, and place the engineering ceramic substrate on the tantalum wire holder;

[0051] (3) Turn on the mechanical pump and evacuate to below 10 Pa;

[0052] (4) After cleaning the ventilation pipeline, open the hydrogen channel and introduce a certain flow of hydrogen into the reaction chamber.

[0053] (5) Turn on the power and raise the filament temperature and substrate temperature to the test values;

[0054] (6) Wait 10-15 minutes and use hydrogen atoms to clean the substrate surface again;

[0055] (7) A certain proportion of methane is introduced to begin diamond deposition;

[0056] (8) Adjust the methane / hydrogen ratio and deposition time in real time to control the filament and substrate temperature;

[0057] (9) After the deposition is completed according to the expected growth time, lower the molybdenum support stage and slowly and gradually reduce the substrate temperature;

[0058] (10) After cooling is complete, release the gas until the cavity door is opened, and take out the deposited diamond coating sample.

[0059] In this embodiment of the invention, a schematic diagram of the DC magnetron sputtering equipment used for molybdenum disulfide coating deposition is shown below. Figure 2 As shown, its structure includes: 1-target stage, 2-substrate, 3-cooling water, 4-argon gas inlet, 5-pressure gauge, 6-vacuum system, 7-substrate stage, 8-bell jar. The specific steps are as follows:

[0060] (1) First turn on the chiller to start circulating the cooling water;

[0061] (2) Open the sample chamber of the magnetron sputtering instrument, prepare the diamond-coated sample, move it to the sample chamber and fix it; place the 99.99% pure molybdenum disulfide on the target stage, adjust the distance between the target and the diamond-coated substrate sample to the required distance, close the substrate baffle and close the sample chamber.

[0062] (3) Vacuuming: Turn on the mechanical pump, then open the pre-evacuation valve. Wait until the vacuum level drops below 10 Pa, then close the pre-evacuation valve. Next, open the fore-stage valve, reset the gate valve, and directly open the evacuation valve to 100%. Finally, turn on the molecular pump and evacuate to 8 × 10 Pa. -4 ~9×10 -4 Pa;

[0063] (4) Adjusting the gas flow path: First, open the mixing valve, select the argon gas channel, and use the knob to adjust the argon gas flow rate; adjust to the required pressure by jogging the switch valve.

[0064] (5) Adjust the DC power supply: After turning on the start button, adjust the knob to control the current and voltage, and adjust the temperature of the sample heating area to the required level;

[0065] (6) After adjusting all process parameters, first open the target baffle, but do not open the substrate baffle to ensure that impurities are not sputtered onto the substrate. After the sputtering is stable, open the substrate baffle and start sputtering the molybdenum disulfide coating. Adjust the sputtering time and start sputtering the coating. After the sputtering is completed, turn off the sputtering switch, argon valve and vacuum pump, and open the inlet valve. When the pressure in the sample chamber is atmospheric pressure, take out the sample film and finally obtain the gradient diamond / molybdenum disulfide composite self-lubricating friction-reducing engineering ceramic coating.

[0066] Example 1

[0067] In this embodiment, taking silicon nitride (Si3N4) ceramic as an example, a composite self-lubricating and friction-reducing engineering ceramic coating is deposited on the surface of the silicon nitride ceramic substrate. The silicon nitride ceramic substrate has a diameter of 100 mm and a thickness of 10 mm. The ratio of acetone solution, deionized water and ethanol solution in the ultrasonic cleaning of the silicon nitride (Si3N4) ceramic is 1:4:5.

[0068] A gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating is composed of a first-order size progressive diamond coating and a molybdenum disulfide coating. Its structure is as follows: from the surface of the silicon nitride ceramic substrate outward, there are first-order size progressive diamond coatings and molybdenum disulfide coatings.

[0069] The structure of the first-order size-progressive diamond coating, from the surface of the ceramic substrate to the outside, consists of: 3 layers of micron-sized diamond coating, 1 layer of fine-grained diamond coating, and 1 layer of nanocrystalline diamond coating. The grain size of diamond in each adjacent diamond coating decreases sequentially. There is an onion-like carbon structure between the nanocrystalline diamond coating and the molybdenum disulfide coating.

[0070] Among them, in the three-layer micron-sized diamond coating, the diamond grain size from the surface of the silicon nitride substrate outwards is as follows: the diamond grain size in the first layer of diamond coating is 2.4-3 μm, with an average grain size of 2.7 μm; the diamond grain size in the second layer of diamond coating is 1.7-2.4 μm, with an average grain size of 2.0 μm; and the diamond grain size in the third layer of diamond coating is 1-1.7 μm, with an average grain size of 1.3 μm.

[0071] In the fine-grained diamond coating, the diamond grain size is 0.2–1 μm, and the average grain size is 0.4 μm;

[0072] In the nanocrystalline diamond coating, the diamond grain size is 20-200 nm, and the average grain size is 110 nm.

[0073] In the molybdenum disulfide coating, the molybdenum disulfide grain size is 30-60 nm, and the average grain size is 45 nm.

[0074] The total thickness of the first-order dimension-progressive diamond coating is 2.7 μm, and the total thickness of the molybdenum disulfide coating is 40 nm.

[0075] The preparation method of the above-mentioned gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating adopts CVD hot-wire chemical vapor deposition and PVD magnetron sputtering, respectively, and specifically includes the following steps:

[0076] Step 1: Pretreatment of engineering ceramic substrate

[0077] A silicon nitride ceramic sample was taken and its surface was pretreated with diamond micron powder grinding. The specific process was as follows: the silicon nitride ceramic sample was placed in a beaker, and acetone solution, deionized water and ethanol solution were added. Then it was cleaned in an ultrasonic cleaner for 15 minutes. After cleaning, it was dried with nitrogen gas. Then, 5μm and 10μm diamond mixed powder was stirred in glycerol and applied to the surface of the ceramic substrate. It was polished with sandpaper that had been soaked in water. Different grades of sandpaper were used, from smallest to largest, 600#-800#-1000#-1200#. It was polished with 0.5μm diamond polishing paste. Then the substrate was placed in an acetone solution containing diamond powder for ultrasonic treatment for 15 minutes. After cleaning, the silicon nitride substrate was placed in an oven to dry, and the dried silicon nitride ceramic substrate was obtained. The ultrasonic frequency of ultrasonic cleaning was 40kHz.

[0078] Step 2: Deposit diamond coating

[0079] The surface-treated engineering ceramic substrate is placed on the chamber stage of the hot filament chemical vapor deposition apparatus. The hot filament in the hot filament chemical vapor deposition apparatus is a tantalum wire, and a first-order size progressive diamond coating is deposited and grown on the surface of the surface-treated engineering ceramic substrate.

[0080] The process parameters for the hot-wire chemical vapor deposition apparatus used to prepare the first layer of microcrystalline diamond coating were as follows: chamber pressure 4 kPa, hot-wire temperature 2200℃, substrate temperature 800℃, hydrogen flow rate 600 sccm, methane / hydrogen volume concentration ratio 1.3%, current 95 A, and the distance between the hot-wire and the upper surface of the surface-grafted silicon nitride ceramic substrate 15 mm; the deposition time was 1 h, resulting in the first layer of microcrystalline diamond coating. The diamond grain size in the first layer of microcrystalline diamond coating was 2.4–3 μm, with an average grain size of 2.7 μm.

[0081] To prepare a second layer of microcrystalline diamond coating, the methane / hydrogen volume concentration ratio was adjusted to 2%, while other parameters remained unchanged. The deposition time was 0.8 h. The second layer of microcrystalline diamond coating was obtained with diamond grain size of 1.7–2.4 μm and average grain size of 2 μm.

[0082] To prepare a third layer of microcrystalline diamond coating, the methane / hydrogen volume concentration ratio was adjusted to 2.7%, while other parameters remained unchanged. The deposition time was 0.6 h. The third layer of microcrystalline diamond coating was obtained with diamond grains ranging from 1 to 1.7 μm in size and an average grain size of 1.3 μm.

[0083] To prepare a fine-grained diamond coating, the methane / hydrogen volume concentration ratio was adjusted to 3.7%, while other parameters remained unchanged. The deposition time was 0.5 h. The resulting fine-grained diamond coating had a diamond grain size of 0.2–1 μm and an average grain size of 0.4 μm.

[0084] To prepare a nanocrystalline diamond coating, the methane / hydrogen volume concentration ratio was adjusted to 4.7%, while other parameters remained unchanged. The nanocrystalline diamond coating was deposited for 0.45 h, resulting in a nanocrystalline diamond coating with a size of 20–200 nm and an average particle size of 110 nm.

[0085] After the diamond coating is deposited, the mechanical pump is turned off. After the temperature inside the chamber cools to room temperature, the silicon nitride ceramic sample is taken out. Thus, the preparation of the micron / fine grain / nano diamond coating on the surface of silicon nitride ceramic is completed.

[0086] Step 3: Annealing

[0087] The onion-like carbon structure conversion between nanodiamond and molybdenum disulfide was achieved using an annealing method. The specific steps are as follows:

[0088] (1) Mix nano-diamond powder and molybdenum disulfide powder together at a ratio of 8:1;

[0089] (2) Mix the powder with glycerin and coat it evenly on the surface of the diamond sample. Then place it in a tube furnace and heat it at a rate of 20℃ / min to an annealing temperature of 1800℃ for 1 hour. After the annealing is completed, cool the annealed sample to room temperature under an argon atmosphere and then take it out for use.

[0090] Step 4: Deposit molybdenum disulfide coating

[0091] The annealed engineering ceramic substrate was placed in the cavity of a DC magnetron sputtering equipment to begin depositing a molybdenum disulfide coating. The DC magnetron sputtering deposition process parameters for the molybdenum disulfide coating were: sputtering pressure of 1 Pa, sputtering power of 30 W, target-substrate spacing of 11 cm, sputtering temperature of 400 °C, and sputtering time of 0.5 h. A gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating was obtained, with a hardness of 6 GPa and a friction coefficient of 0.06. This composite coating has good hardness, lubricity, adhesion, and wear resistance.

[0092] Example 2

[0093] Similar to Example 1, except that: the deposition process parameters for depositing the diamond coating in step 2 are as follows: chamber pressure is 3.5 kPa, hot wire temperature is 2100℃, surface-inoculated engineering ceramic substrate temperature is 850℃, the distance between the hot wire and the surface-inoculated engineering ceramic substrate is 10 mm, the volume concentration ratio is methane:hydrogen = (1~5):100, and the hydrogen flow rate is 400 sccm; the remaining deposition process parameters remain unchanged, resulting in a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating.

[0094] The prepared gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating has the following diamond grain sizes from the surface of the silicon nitride substrate outwards in the three-layer micron-grained diamond coating: the average diamond grain size in the first layer is 2.8 μm, the average diamond grain size in the second layer is 2.1 μm, and the average diamond grain size in the third layer is 1.4 μm; the average diamond grain size in the fine-grained diamond coating is 0.8 μm; and the average diamond grain size in the nanocrystalline diamond coating is 130 nm.

[0095] Example 3

[0096] Same as Example 1, except that: the deposition process parameters for depositing the diamond coating in step 2 are: chamber pressure of 3.8 kPa, hot wire temperature of 2150°C, surface-inoculated engineering ceramic substrate temperature of 830°C, distance between the hot wire and the upper surface of the surface-inoculated engineering ceramic substrate of 12 mm, methane:hydrogen = (1~5):100 by volume concentration, and hydrogen flow rate of 500 sccm; the remaining deposition process parameters remain unchanged, and a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating is obtained.

[0097] The prepared gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating has three layers of micron-sized diamond coatings. The average diamond grain size from the surface of the silicon nitride substrate outwards is as follows: the first layer of diamond coating has an average diamond grain size of 2.8 μm, the second layer has an average diamond grain size of 2 μm, and the third layer has an average diamond grain size of 1.2 μm; the fine-grained diamond coating has an average diamond grain size of 0.6 μm; and the nanocrystalline diamond coating has an average diamond grain size of 100 nm.

[0098] Example 4

[0099] Similar to Example 1, except that in step 2, the first microcrystalline diamond coating is deposited with the methane / hydrogen volume concentration ratio adjusted to 1.5%, the second microcrystalline diamond coating is deposited with the methane / hydrogen volume concentration ratio adjusted to 2%, the third microcrystalline diamond coating is deposited with the methane / hydrogen volume concentration ratio adjusted to 3%, the fine-grained diamond coating is deposited with the methane / hydrogen volume concentration ratio adjusted to 3.5%, and the nanocrystalline diamond coating is deposited with the methane / hydrogen volume concentration ratio adjusted to 4.5%; the remaining deposition process parameters remain unchanged, resulting in a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating.

[0100] The prepared gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating has three layers of micron-sized diamond coatings. The average diamond grain size from the surface of the silicon nitride substrate outwards is as follows: the first layer of diamond coating has an average diamond grain size of 2.6 μm, the second layer has an average diamond grain size of 1.9 μm, and the third layer has an average diamond grain size of 1.2 μm; the fine-grained diamond coating has an average diamond grain size of 0.4 μm; and the nanocrystalline diamond coating has an average diamond grain size of 90 nm.

[0101] Example 5

[0102] Similar to Example 1, except that the heat treatment process parameters in step 3 are: heating rate of 20℃ / min and heating temperature of 1700℃; the other deposition process parameters remain unchanged, resulting in a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating with a hardness of 4GPa.

[0103] Example 6

[0104] Similar to Example 1, except that the heat treatment process parameters in step 3 are: heating rate of 25℃ / min and heating temperature of 1850℃; the other deposition process parameters remain unchanged, resulting in a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating with a hardness of 8GPa.

[0105] Example 7

[0106] Similar to Example 1, except that the DC magnetron sputtering deposition process parameters for the molybdenum disulfide coating in step 4 are: sputtering pressure of 2 Pa, sputtering power of 100 W, target-to-substrate distance of 13 cm, and sputtering temperature of 420 °C; the remaining deposition process parameters remain unchanged, resulting in a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating. In the obtained composite coating, the average grain size of molybdenum disulfide is 50 nm, and the coefficient of friction of the composite coating is 0.1.

[0107] Example 8

[0108] Similar to Example 1, except that in step 4, the DC magnetron sputtering deposition process parameters for the molybdenum disulfide coating are: sputtering pressure of 1.5 Pa, sputtering power of 50 W, target-to-substrate distance of 10 cm, and sputtering temperature of 380 °C; the remaining deposition process parameters remain unchanged, resulting in a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating. In the obtained composite coating, the average grain size of molybdenum disulfide is 48 nm, and the coefficient of friction of the composite coating is 0.08.

Claims

1. A method for preparing a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating, characterized in that, The methods employed are CVD hot-filament chemical vapor deposition and PVD magnetron sputtering, and specifically include the following steps: Step 1: Pretreatment of engineering ceramic substrate The surface of the engineering ceramic substrate is roughened by micro-treatment, and then cleaned and dried to obtain the treated engineering ceramic substrate. Step 2: Deposit diamond coating The surface-treated engineering ceramic substrate is placed on the chamber stage of the hot filament chemical vapor deposition apparatus, and a first-order size progressive diamond coating is deposited and grown on the surface of the surface-treated engineering ceramic substrate. Step 3: Annealing The diamond-deposited engineering ceramic substrate is placed in a tube furnace, heated for a period of time, cooled to room temperature and removed to obtain a sample with an onion-like carbon structure on the surface for later use. The specific steps for annealing are as follows: (1) Mix nanodiamond powder and molybdenum disulfide powder together at a ratio of (7~8):1; (2) Mix the powder with glycerin and coat it evenly on the surface of the diamond sample. Then place it in a tube furnace and heat it at a rate of 20~30 ℃ / min to an annealing temperature of 1700~2000℃ for 0.8~1 h. After the annealing is completed, cool the annealed sample to room temperature under an argon atmosphere and then take it out for use. Step 4; Deposition of molybdenum disulfide coating The annealed engineering ceramic substrate was placed in the cavity of a DC magnetron sputtering equipment to begin depositing a molybdenum disulfide coating; after deposition, the sample film was removed, and finally a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating was obtained. The ceramic coating is composed of a first-order size progressive diamond coating and a molybdenum disulfide coating. Its structure is as follows: from the surface of the silicon nitride ceramic substrate outward, there are first-order size progressive diamond coatings and molybdenum disulfide coatings. The structure of the first-order size-progressive diamond coating, from the surface of the ceramic substrate outwards, consists of: 3 layers of micron-sized diamond coating, 1 layer of fine-grained diamond coating, and 1 layer of nanocrystalline diamond coating. The grain size of diamond in adjacent diamond coatings decreases sequentially with each layer. An onion-like carbon structure exists between the nanocrystalline diamond coating and the molybdenum disulfide coating. In the 3 layers of micron-sized diamond coating, the diamond grain size from the surface of the silicon nitride substrate outwards is as follows: the diamond grain size in the first layer is 2.4~3 μm, the diamond grain size in the second layer is 1.7~2.4 μm, and the diamond grain size in the third layer is 1~1.7 μm. In the fine-grained diamond coating, the diamond grain size is 0.2~1μm; In the nanocrystalline diamond coating, the diamond grain size is 20~200nm; In the molybdenum disulfide coating, the molybdenum disulfide grain size is 30~60nm.

2. The method for preparing a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating according to claim 1, characterized in that, The total thickness of the first-order size-progressive diamond coating is 2.7~3 μm, and the total thickness of the molybdenum disulfide coating is 40~100 nm.

3. The method for preparing a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating according to claim 1, characterized in that, The gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating has a hardness of 4~15 GPa and a friction coefficient of 0.05~0.

1.

4. The method for preparing a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating according to claim 1, characterized in that, In step 2, the deposition process parameters for the diamond coating are as follows: chamber pressure is 3.5~4 kPa, hot wire temperature is 2100~2200℃, surface-inoculated engineering ceramic substrate temperature is 800~850℃, the distance between the hot wire and the upper surface of the surface-inoculated engineering ceramic substrate is 10~15 mm, deposition time is 0.45~1 h, methane:hydrogen ratio is (1~5):100 by volume concentration, hydrogen flow rate is 400~600 sccm, methane flow rate is 4~30 sccm, and current is 95~100 A.

5. The method for preparing a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating according to claim 1, characterized in that, When depositing microcrystalline diamond coatings, the methane / hydrogen volume concentration ratio R is adjusted. 微米 For: 1%≤R 微米 <3%; When depositing fine-grained diamond coatings, adjust the methane / hydrogen volume concentration ratio R. 细晶粒 For: 3%≤R 细晶粒 <4%; When depositing nanocrystalline diamond coatings, adjust the methane / hydrogen volume concentration ratio R 纳米 For: 4%≤R 纳米 <5%.

6. The method for preparing a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating according to claim 5, characterized in that, During the growth of the microcrystalline diamond coating, the methane / hydrogen volume concentration ratio R of the first layer is controlled. 微1 For: 1%≤R 微1 <1.7%, second layer methane / hydrogen volume concentration R 微2 The value is: 1.7%≤R 微2 <2.4%, third layer methane / hydrogen volume concentration ratio R 微3 The value is: 2.4%≤R 微3 <3%.

7. The method for preparing a gradient diamond / molybdenum disulfide composite self-lubricating and friction-reducing engineering ceramic coating according to claim 1, characterized in that, In step 4, the DC magnetron sputtering deposition process parameters for the molybdenum disulfide coating are as follows: sputtering pressure is 1~2 Pa, sputtering power is 30~100 W, target-to-substrate distance is 10~13 cm, sputtering temperature is 380~420℃, and sputtering time is 0.4~0.5 h.

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