阅读说明：本技术 一种耐空蚀纳米晶高熵氮化物陶瓷涂层的制备方法 (Preparation method of cavitation erosion resistant nanocrystalline high-entropy nitride ceramic coating ) 是由 徐江 赵焰杰 蒋书运 于 2021-07-20 设计创作，主要内容包括：本发明公开了一种耐空蚀纳米晶高熵氮化物陶瓷涂层的制备方法,属于高熵陶瓷涂层技术领域。本发明采用双阴极等离子体反应沉积技术制备耐空蚀纳米晶高熵氮化物陶瓷涂层,通过调节靶材与工件之间的距离、电压以及通入真空室中的工作气体流量和工作气压,达到控制沉积温度和靶材沉积速率的目的。本发明制备的涂层是由单一的、面心立方结构的纳米晶组成；涂层致密无缺陷,各元素分布均匀,与基体具有良好的结合力。该涂层在降低本征脆性的同时保持了过渡金属氮化物的高硬度、高强度、高耐蚀性能,能有效提高钛合金在模拟海洋环境中的抗空蚀性能,在水工机械领域具有极高的应用潜力。(The invention discloses a preparation method of a cavitation erosion resistant nanocrystalline high-entropy nitride ceramic coating, and belongs to the technical field of high-entropy ceramic coatings. The invention adopts a double-cathode plasma reaction deposition technology to prepare the cavitation erosion resistant nanocrystalline high-entropy nitride ceramic coating, and achieves the purpose of controlling the deposition temperature and the deposition rate of the target material by adjusting the distance and the voltage between the target material and the workpiece and the flow and the working pressure of the working gas introduced into a vacuum chamber. The coating prepared by the invention consists of single nanocrystalline with a face-centered cubic structure; the coating is compact and has no defect, all elements are uniformly distributed, and the coating has good binding force with a matrix. The coating maintains the high hardness, high strength and high corrosion resistance of the transition metal nitride while reducing the intrinsic brittleness, can effectively improve the cavitation corrosion resistance of the titanium alloy in the simulated marine environment, and has extremely high application potential in the field of hydraulic machinery.)

1. A preparation method of a cavitation erosion resistant nanocrystalline high-entropy nitride ceramic coating is characterized by comprising the following steps: the method comprises the following steps:

step 1, prefabricating a target: taking five kinds of commercial high-purity metal powder of Ti, Zr, Nb, Ta and Mo, and carrying out vacuum hot-pressing sintering to prepare a target material;

step 2, preparing a matrix: taking a workpiece electrode substrate for later use;

step 3, preparing a coating by a double-cathode plasma reaction deposition technology: and (3) taking the target material in the step (1) as a source electrode and the substrate in the step (2) as a working electrode, and performing double-cathode plasma reaction deposition under the vacuum condition and the working atmosphere.

2. The method of claim 1, wherein: in the step 1, five metal powders of Ti, Zr, Nb, Ta and Mo are in equal molar ratio, and the target material is a wafer with phi 80mm multiplied by 5 mm.

3. The method of claim 1, wherein: in the step 2, the workpiece pole substrate is stainless steel or Ti-6Al-4V alloy.

4. The method of claim 1, wherein: in the step 3, the distance between the source electrode and the workpiece electrode is 10-20 mm.

5. The method of claim 4, wherein: in the step 3, the working gas is a mixed gas of nitrogen and argon, and the flow ratio of the nitrogen to the argon is 1: 10; the pressure of the working gas is 30-45 Pa.

6. The method of claim 5, wherein: in the step 3, the voltage of the source electrode is 850V-1000V; the voltage of the workpiece electrode is 300-350V.

7. The method of claim 6, wherein: in the step 3, the temperature of the double-cathode plasma reaction deposition is 750-900 ℃ and the time is 3-4 hours.

Technical Field

The invention belongs to the technical field of high-entropy ceramic coatings, and particularly relates to a preparation method of a cavitation erosion resistant nanocrystalline high-entropy nitride ceramic coating.

Background

The cavitation phenomenon is widely existed in the field of hydraulic machinery, when the local pressure of high-speed flow is suddenly changed, the micro-jet flow and shock wave generated by the collapse of micro-bubbles in the fluid are repeatedly acted on the surface of the material to cause the failure of the material. Cavitation erosion is a serious material fatigue failure mode which affects the operation of large ocean and energy equipment such as high-speed water turbines, high-speed flow pipelines, hydropower station buildings and the like at present. Particularly in the marine environment, the removal of surface materials is further accelerated due to the synergistic effect of corrosive ions such as chloride ions and repeated impact force generated by cavitation collapse, and the service life of the hydraulic machinery is remarkably shortened. Experts and scholars in the fields of machinery, materials and the like carry out extensive research on the improvement of the cavitation erosion resistance of the materials, and the preparation of a high-performance cavitation erosion resistant coating on the surface of a hydraulic machinery material is a way for effectively solving the cavitation erosion damage problem.

The transition metal nitride ceramic material has high melting point, high hardness and high chemical stability, and is widely applied to the fields of high temperature resistance, corrosion resistance, wear resistance and the like. However, most nitrides suffer from intrinsic brittleness, which tends to cause failure of the protective coating. Based on the design concept of the high-entropy alloy, the prepared multi-component single-phase high-entropy nitride ceramic material has thermodynamic high-entropy effect, dynamic slow diffusion effect, serious lattice distortion on the structure and performance cocktail effect, the effects are favorable for forming single-phase simple solid solution, and the high hardness, wear resistance and corrosion resistance are maintained while the intrinsic brittleness of the nitride ceramic material is expected to be reduced. In addition, compared with the ceramic with single component, the mechanical property, corrosion resistance, oxidation resistance and the like of the high-entropy ceramic are expected to be further improved, and the high-entropy nitride is applied to the field of hydraulic machinery, so that the cavitation erosion resistance of equipment is favorably improved, and the service life of the hydraulic machinery is prolonged. However, due to the problems of high melting point, intrinsic brittleness, large difference of thermal expansion coefficient between the nitride and metal and the like, the common coating preparation method is difficult to obtain a compact coating which is firmly combined with a substrate. The double-cathode plasma reaction deposition technology can carry out multi-element codeposition at higher temperature, and the reaction-deposition integrated coating preparation process can be realized by introducing reaction gas into a deposition furnace. The high-entropy nitride coating is prepared by adopting a double-cathode plasma reaction deposition technology, so that the cavitation erosion resistance of the material can be obviously improved, the service life of hydraulic machinery is prolonged, and higher economic benefit is obtained.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a preparation method of a cavitation erosion resistant nanocrystalline high-entropy nitride ceramic coating, the cavitation erosion resistant nanocrystalline high-entropy nitride ceramic coating is prepared by a double-cathode plasma reaction deposition technology, the prepared high-entropy nitride ceramic coating can effectively reduce the intrinsic brittleness of nitride, simultaneously keeps the advantages of high hardness, good corrosion resistance and the like of the nitride, can effectively resist the synergistic action of corrosion and cavitation erosion in a marine environment, and obviously improves the cavitation erosion resistance of a hydraulic machine in the marine environment.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a cavitation erosion resistant nanocrystalline high-entropy nitride ceramic coating comprises the following steps:

step 1, prefabricating a target: taking five kinds of commercial high-purity metal powder of Ti, Zr, Nb, Ta and Mo, and carrying out vacuum hot-pressing sintering to prepare a target material;

step 2, preparing a matrix: taking a workpiece electrode substrate for later use;

step 3, preparing a coating by a double-cathode plasma reaction deposition technology: and (3) taking the target material in the step (1) as a source electrode and the substrate in the step (2) as a working electrode, and performing double-cathode plasma reaction deposition under the vacuum condition and the working atmosphere.

Furthermore, five metal powders of Ti, Zr, Nb, Ta and Mo in the step 1 are in equal molar ratio, and the target material is a wafer with phi 80mm multiplied by 5 mm.

Further, in the step 2, the workpiece pole substrate is made of stainless steel or Ti-6Al-4V alloy.

Further, in the step 3, the distance between the source electrode and the workpiece electrode is 10-20 mm.

Further, in step 3, the working gas is a mixed gas of nitrogen and argon, and the flow ratio of nitrogen to argon is 1: 10; the pressure of the working gas is 30-45 Pa.

Further, in step 3, the voltage of the source electrode is 850V-1000V; the voltage of the workpiece electrode is 300-350V.

Further, in step 3, the temperature of the double-cathode plasma reaction deposition is 750-900 ℃ and the time is 3-4 hours.

The invention adopts a double-cathode plasma reaction deposition technology to prepare the cavitation erosion resistant nanocrystalline high-entropy nitride ceramic coating, and achieves the purpose of controlling the deposition temperature and the deposition rate of the target material by adjusting the distance and the voltage between the target material and the workpiece and the flow and the working pressure of the working gas introduced into a vacuum chamber.

According to the optimized technological parameters and actual requirements, the prepared coating has the following characteristics:

the thickness of the coating is 20-30 mu m, and the coating is flat and compact and has no defects such as holes and cracks;

the coating structure is a single-phase face-centered cubic structure, and the average grain size is about 11 nm;

the nano indentation test shows that the hardness of the coating reaches 33.1 +/-1.2 Gpa, and the elastic modulus is 355.3 +/-9.5 GPa;

a12-hour ultrasonic cavitation test shows that the prepared high-entropy nitride coating obviously improves the cavitation corrosion resistance of the titanium alloy.

Has the advantages that:

1. the preparation method provided by the invention is convenient and efficient, and a simple preparation method of the high-entropy nitride ceramic coating can be obtained by simply regulating and controlling the prior art by a person skilled in the art.

2. Compared with single-phase nitride, the prepared coating can reduce the intrinsic brittleness of the nitride, can keep high hardness and high chemical stability, and obviously improves the fatigue resistance of the surface of a workpiece under a cavitation condition.

3. The high-entropy nitride prepared by the invention is a compact nano isometric crystal structure. Compared with a columnar crystal structure and a coarse crystal structure, the corrosion-resistant coating can effectively inhibit the initiation and the expansion of fatigue cracks, prevent corrosive media from forming local micro-battery corrosion through defects such as microcracks, pores and the like, and can obviously improve the protective capability of the coating.

Drawings

FIG. 1 is the XRD spectrum of the (TiZrNbTaMo) N high entropy nitride ceramic coating of example 1.

FIG. 2 is a cross-section of the (TiZrNbTaMo) N high entropy nitride ceramic coating of example 1.

FIG. 3 shows a TEM image and a selected-area electron diffraction pattern of the (TiZrNbTaMo) N high entropy nitride ceramic coating of example 1.

Detailed Description

The technical solution of the present invention will be further described in detail with reference to the following specific examples.

Example 1

1. Prefabricating a target material: the method comprises the steps of preparing five kinds of metal powder (200 meshes) of commercial high-purity (greater than or equal to 99.9%) Ti, Zr, Nb, Ta and Mo according to the proportion of 20 At% Ti, 20 At% Zr, 20 At% Nb, 20 At% Ta and 20 At% Mo, uniformly mixing powder in a high-speed ball milling tank under the protection of argon gas, then adopting vacuum hot-pressing sintering to obtain a multi-component alloy target material with the diameter of 80mm multiplied by 5mm, and placing the multi-component alloy target material in a drying container for storage and later use. The prepared target material can be repeatedly used, the utilization rate of the target material is improved to the maximum extent, and the production cost is reduced.

2. Matrix: grinding, polishing, cleaning and drying a 30X 3mm commercial titanium alloy Ti-6Al-4V step by step for later use.

3. The preparation process and parameters of the double-cathode plasma reaction deposition technology are as follows:

respectively placing the target material and the substrate in a source electrode and a workpiece electrode sample holder of a cavity, adjusting the distance between the electrodes to be 15mm, and vacuumizing the cavity to 5 multiplied by 10^-4And Pa, introducing argon, regulating the voltage of the substrate to 600V, and sputtering and cleaning the substrate for 10min by using argon ions. Introducing mixed gas of nitrogen and argon, wherein the flow ratio of the nitrogen to the argon is 1: 10. and adjusting the voltage of the source electrode target to 950V, the voltage of the workpiece electrode to 300V, the duty ratio to 0.85 and keeping the working air pressure to 35 Pa. The deposition time is kept for 3.5 hours, and the temperature is cooled to room temperature along with the furnace.

4. The obtained coating was characterized by X-ray diffractometry (XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM), respectively.

FIG. 1 is an XRD spectrum of a (TiZrNbTaMo) N high-entropy nitride coating, and the result shows that diffraction peaks of the XRD spectrum of the prepared coating correspond to face-centered cubic TaN (JCPDS 49-1283), and the high-entropy nitride coating consists of a single face-centered cubic phase and has no other impurity phases; in addition, each diffraction peak has obvious broadening phenomenon, which indicates that the grain size of the coating is fine.

Fig. 2 is a cross-section of the coating observed by Scanning Electron Microscopy (SEM). As can be seen from the figure, the prepared coating is flat and compact, has no defects such as holes, cracks and the like, and has the thickness of about 20 mu m.

FIG. 3 is a Transmission Electron Microscope (TEM) observation of the bright field image and selected area electron diffraction pattern of the coating. As can be seen from fig. 3, the prepared coating consists of nanoscale equiaxed crystals. Statistical analysis of the grain size was carried out, with an average grain size of 11 nm. The selective area electron diffraction pattern is represented by concentric Debye rings with the transmission spot as the center of the circle, reflecting the nanocrystalline characteristics. The diffraction ring corresponds to the (111), (200) and (220) crystal faces of the face-centered cubic structure from inside to outside, and the high-entropy nitride is further proved to be a nanocrystalline single-phase structure.

5. The nano indentation test shows that the hardness (H) of the coating reaches 33.1 +/-1.2 Gpa, and the elastic modulus (E) is 355.3 +/-9.5 GPa. The coating has good mechanical property and can effectively resist cavitation erosion.

6. According to the ASTM G32-16 ultrasonic cavitation erosion test standard, the surface area of each of the titanium alloy without the coating and the titanium alloy coated with the high-entropy nitride coating is 1cm²The sample of (1). A12-hour cavitation experiment is carried out in a simulated seawater (3.5% NaCl) environment, and the weight loss test result shows that the weight loss of the uncoated titanium alloy is 6.21 +/-0.13 mg, and the weight loss of the high-entropy nitride coating is only 0.2 +/-0.05 mg.

Example 2

1. Prefabricating a target material: the method comprises the steps of preparing five kinds of metal powder (200 meshes) of commercial high-purity (not less than 99.9%) Ti, Zr, Nb, Ta and Mo according to the proportion of 20 At% Ti, 20 At% Zr, 20 At% Nb, 20 At% Ta and 20 At% Mo, firstly carrying out high-speed ball milling and powder mixing under the argon protection condition, then adopting vacuum hot-pressing sintering to obtain a phi 80mm multiplied by 5mm multi-component alloy target material, and placing the target material in a drying vessel for storage and standby. The prepared target material can be repeatedly used, the utilization rate of the target material is improved to the maximum extent, and the production cost is reduced.

2. Matrix: grinding, polishing, cleaning and drying the 30X 3mm commercial 316L stainless steel step by step for later use.

3. The preparation process and parameters of the double-cathode plasma reaction deposition technology are as follows:

respectively placing the target material and the substrate in a source electrode and a workpiece electrode sample holder of a cavity, adjusting the distance between the electrodes to be 10mm, and vacuumizing the cavity to 5 multiplied by 10^-4And Pa, introducing argon, regulating the voltage of the substrate to 600V, and sputtering and cleaning the substrate for 10min by using argon ions. Introducing mixed gas of argon and nitrogen, wherein the flow ratio of the argon to the nitrogen is 10: 1. and adjusting the voltage of the source electrode target material to 950V, the voltage of the substrate to 350V and the duty ratio to 0.85, and keeping the working air pressure to 35 Pa. The deposition time is kept for 3.5 hours, and the temperature is cooled to room temperature along with the furnace.

4. The coating prepared on the surface of 316L stainless steel by the above process has a reduced coating adhesion compared to example 1, which may be caused by a large difference in thermal expansion coefficient between the deposited coating and the stainless steel.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.