Suspension Plasma Spraying of Dense Wear-Resistant Alumina Coatings, Their Preparation and Application

Abstract

This invention discloses a dense, wear-resistant alumina coating produced by suspension plasma spraying, its preparation method, and its application. The preparation method includes: pretreating the substrate; applying an alumina suspension to the substrate surface using axial suspension plasma spraying technology to obtain a dense, wear-resistant alumina coating; wherein the process parameters for the axial suspension plasma spraying technology include: a spray gun power of 125-150 kW, a spraying distance of 50-150 mm, a liquid delivery rate of 30-120 ml / min, and a substrate surface temperature of 300-600 °C during spraying. The method provided by this invention features simple operation, short production cycle, controllable coating thickness, and high production efficiency. Simultaneously, the prepared alumina coating retains the chemical composition of the sprayed alumina and has advantages such as larger coating size, denser coating structure, higher bonding strength, higher hardness, lower wear rate, and applicability to more substrate types.

Description

Technical Field

[0001] This invention belongs to the field of ceramic coatings on metal surfaces, specifically relating to a dense and wear-resistant alumina coating produced by plasma spraying of a suspension, its preparation method, and its application. Background Technology

[0002] Alumina coatings, with their high hardness, high chemical stability, and excellent wear and corrosion resistance, are widely used in industrial fields to ensure the stable operation of high-end equipment components in harsh service environments, reduce damage to the base material, and extend their service life. Alumina coatings can be used for low-stress abrasive wear, hard surface wear, resistance to various chemical media and chemical gases, cavitation and erosion resistance at room temperature, and also for high-temperature cavitation resistance and high-temperature emission coatings. They have broad application prospects in many industries, including electronics, petroleum, steel metallurgy, machinery and chemical engineering, equipment manufacturing, and aerospace.

[0003] Current methods for preparing alumina coatings include arc ion plating, pulsed laser deposition, micro-arc oxidation, magnetron sputtering, and chemical vapor deposition. However, the preparation of dense alumina coatings still faces challenges, such as excessive porosity and incomplete particle melting. Plasma spraying offers advantages such as high flame temperature, simple process, high efficiency, and excellent coating performance. It allows for the rapid deposition of alumina ceramic coatings on substrates, organically combining the advantages of alumina ceramic materials and the substrate to improve component performance. Although traditional atmospheric plasma spraying (APS) can achieve a wide range of coating structures, it is limited to powders with good flowability (10-100 μm) and restricts the selection of coating materials. Furthermore, the coating structure still suffers from porosity defects. Patent CN118063196A discloses a method for preparing porous alumina ceramics with a porosity distribution of 8-15%. This high porosity is unsuitable for the frictional corrosion environments of daily life and production, as it provides pathways for frictional fatigue and corrosion, accelerating coating failure.

[0004] Currently, it is generally believed that the higher the solid content, the denser the structure of the coating. However, the current plasma spraying power on the market is only 60-70kW, which is insufficient to achieve high power, making it difficult to completely melt the liquid particles, resulting in various structural defects and wasting raw materials. Furthermore, high-concentration suspensions lead to extremely poor flowability and extensibility during spraying, easily causing powder blockage and hindering the spraying of irregularly shaped workpieces and long-term spraying. In existing technologies, low-concentration suspensions are difficult to prepare highly dense coatings, and low power makes it difficult to achieve good and complete melting of the liquid. Therefore, developing high-power spraying techniques for low-concentration aqueous suspensions to prepare dense coatings to improve raw material utilization and cost-effectiveness is crucial. Simultaneously, developing a high-mechanical-strength alumina coating based on suspension plasma spraying that can be rapidly deposited on various substrates for engineering applications is of great importance. Summary of the Invention

[0005] The main objective of this invention is to provide a dense, wear-resistant alumina coating produced by plasma spraying of suspension, its preparation method, and its application, in order to overcome the shortcomings of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides a method for preparing a dense, wear-resistant alumina coating by plasma spraying with a suspension, comprising:

[0008] Pre-treat the substrate;

[0009] Furthermore, an alumina suspension is applied to the surface of a substrate using axial suspension plasma spraying technology to obtain a dense and wear-resistant alumina coating; wherein the alumina content in the alumina suspension is 10-20wt%, and the dispersant content is 1-5wt%; the process parameters used in the axial suspension plasma spraying technology include: a spray gun power of 125-150kW, a spraying distance of 50-150mm, a liquid delivery rate of 30-120ml / min, and a substrate surface temperature of 300-600℃ during the spraying process.

[0010] The present invention also provides a dense wear-resistant alumina coating prepared by the aforementioned preparation method.

[0011] This invention also provides the application of the aforementioned dense alumina wear-resistant coating in the field of wear-resistant and corrosion-resistant white surfaces of irregularly shaped workpieces.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] (1) The alumina coating in this invention utilizes plasma spraying technology. By changing the concentration of the alumina dispersion solution, the concentration of the dispersant, the liquid flow rate, the spraying distance, the spraying power, the spray gun movement state, and the number of spraying cycles, the thickness and structure of the alumina coating can be effectively controlled. Since the alumina droplets have a high enthalpy value when deposited onto the coating, they can efficiently deposit while forming mechanical interlocking with various substrates, thereby forming a mechanical interlocking force much stronger than weak van der Waals forces. The deposition efficiency of the coating can be intuitively set by controlling only the movement parameters of the robotic arm that moves the spray gun. At the same time, the use of a high power of about 140kW avoids the generation of unmelted and semi-melted particles, breaks through the limitation that low-concentration suspensions cannot prepare dense coatings, improves the utilization rate of liquid raw materials, reduces waste and cost, and breaks through the industry's alumina wear rate limit, reducing the specific wear rate to 5×10 -16 m 3 N -1 m -1 the following;

[0014] (2) The alumina coating spraying process in this invention has the characteristics of simple process, short production cycle and high production efficiency. Compared with conventional alumina coating preparation methods, the alumina coating prepared by this invention has the advantages of larger preparation size, denser coating structure, higher bonding strength, higher hardness, lower wear rate and more applicable substrate types. At the same time, the high power and low solid content make the liquid material have considerable fluidity and the molten droplets have good extensibility, which is more suitable for spraying irregular workpieces. It can be used for various alumina coatings for practical engineering applications, such as those with wear-resistant and friction-reducing properties and corrosion resistance.

[0015] (3) The spraying area and layer thickness of the alumina coating in this invention can be selected according to the specific function. Without significantly changing the coating structure, increasing the liquid delivery rate or adjusting the spraying distance can change the deposition efficiency of the coating. At the same time, this invention uses axial suspension plasma spraying, which improves the kinetic and thermal energy of the liquid material, allowing the liquid material to fully melt and achieve a denser, flattened deposition. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 These are actual photos of the plasma spraying equipment of this invention;

[0018] Figure 2The graph shows the hardness, dry friction wear rate, and seawater friction wear rate of the Al2O3 coating prepared in Example 1 of this invention.

[0019] Figures 3a-3b These are cross-sectional morphology images of the Al2O3 coating prepared in Example 1 of this invention;

[0020] Figures 4a-4b These are cross-sectional morphology images of the Al2O3 coating prepared in Example 2 of this invention;

[0021] Figures 5a-5b This is a graph showing the friction coefficient of the Al2O3 coating prepared in Examples 1-2 of this invention under a 10N load;

[0022] Figure 6 These are cross-sectional hardness diagrams of the Al2O3 coatings prepared in the embodiments and comparative examples of the present invention;

[0023] Figures 7a-7d These are dry friction and wear microstructure images of the Al2O3 coatings prepared in Examples 1-2 of this invention;

[0024] Figure 8 This is a diagram of the Al2O3 coating on the surface of the irregularly shaped workpiece prepared in Example 1 of the present invention. Detailed Implementation

[0025] In view of the deficiencies of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The main purpose is to explore the influence of the amount of polymeric dispersant added and different spraying processes on the coating structure and to achieve defect control. This solves the problem of numerous pores and poor density in the preparation of alumina coatings. The prepared alumina coating has good density, hardness, wear resistance and high bonding strength, which provides convenience for subsequent engineering applications.

[0026] The technical solution of the present invention will be clearly and completely described below. 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.

[0027] Specifically, as one aspect of the technical solution of this invention, the method for preparing a dense and wear-resistant alumina coating by plasma spraying of a suspension includes:

[0028] Pre-treat the substrate;

[0029] Furthermore, an alumina suspension is applied to the surface of a substrate using axial suspension plasma spraying technology to obtain a dense and wear-resistant alumina coating; wherein the alumina content in the alumina suspension is 10-20wt%, and the dispersant content is 1-5wt%; the process parameters used in the axial suspension plasma spraying technology include: a spray gun power of 125-150kW, a spraying distance of 50-150mm, a liquid delivery rate of 30-120ml / min, and a substrate surface temperature of 300-600℃ during the spraying process.

[0030] In some preferred embodiments, the process parameters used in the axial suspension plasma spraying technology include: argon flow rate of 20~30 L / min, nitrogen flow rate of 50~60 L / min, hydrogen flow rate of 5~15 L / min, total gas flow rate of 200~300 L / min, arc current of 200~240A, and atomizing gas flow rate of 10~20 L / min.

[0031] In some preferred embodiments, the preparation method specifically includes: fixing the substrate to a rotating sample stage fixture, preheating the surface of the substrate to 100-300°C, then maintaining the rotating sample stage fixture in a rotating or flipping motion, with the spray gun axis orthogonal to the substrate surface, and the spray gun reciprocating up and down; wherein the rotational speed of the rotating sample stage fixture is 150~250 R / min, the up-and-down movement speed of the spray gun is 15~25 mm / min, and the number of spray gun cycles is 100-200 times.

[0032] Furthermore, the surface of the substrate is preheated to 100-300°C using plasma flame scanning; wherein the number of plasma flame scanning cycles is 2-4 times.

[0033] Furthermore, the material of the substrate includes any one of metal, ceramic, glass, and plastic, but is not limited thereto.

[0034] Furthermore, the thickness of the substrate is 1-100 mm.

[0035] Furthermore, the substrate includes, but is not limited to, irregularly shaped workpiece substrates.

[0036] In some preferred embodiments, the preparation method specifically includes: cleaning the substrate, sandblasting it, and then blowing away the surface dust of the substrate with a high-pressure air gun.

[0037] Furthermore, the substrate is ultrasonically cleaned using ethanol; wherein the ultrasonic cleaning process is performed at a frequency of 20-80 Hz and a cleaning time of 10-20 min.

[0038] Furthermore, the sandblasting treatment is performed using alumina gravel; wherein the alumina gravel includes alumina white fused alumina sand, and the particle size of the alumina white fused alumina sand is 80-120 mesh.

[0039] Furthermore, the pressure used in the sandblasting process is 0.5~1.0 MPa.

[0040] In some preferred embodiments, the method for preparing the suspension plasma-sprayed dense wear-resistant alumina coating includes the following steps:

[0041] The substrate is cleaned and then sandblasted. The resulting substrate is then blown away with a high-pressure air gun to remove surface dust. The substrate surface is preheated to 100-300℃, and then an alumina suspension is deposited onto the substrate surface using a suspension plasma spraying technique to obtain an alumina coating. The alumina suspension concentration is 10-20 wt.%, and the dispersant concentration is 1-5 wt.%. The spray gun power is 125-150 kW; the spraying distance is 50-150 mm; the liquid delivery rate is 30-120 ml / min; and the substrate surface temperature during spraying is 300-600℃.

[0042] In the process of preparing a dense and wear-resistant alumina coating, the present invention first cleans the substrate and then performs sandblasting.

[0043] The cleaning process specifically employs ultrasonic cleaning to remove oil, dust, and debris from the substrate surface. In this application, ethanol is used as the cleaning agent; compared to deionized water, ethanol has a better cleaning effect, and compared to other organic solvents, ethanol is more environmentally friendly, economical, and safe. The ultrasonic cleaning time is 10-20 minutes, and the ultrasonic treatment frequency is 20-80 Hz. The sandblasting treatment is performed according to methods well known to those skilled in the art. Sandblasting increases the surface roughness of the substrate, improves the mechanical interlocking force between the substrate and the coating, and enhances the bonding strength of the coating. In this invention, alumina white corundum sand is selected for sandblasting, and the sandblasting pressure is 0.5-1 MPa. The substrate surface is repeatedly and uniformly sandblasted until it is rough and non-reflective.

[0044] This invention fixes the substrate on a rotating sample stage, maintaining rotation during the spraying process. The spray gun axis is orthogonal to the substrate surface, and the spray gun reciprocates up and down. By coordinating the rotation of the sample stage with the movement speed of the spray gun, the surface speed of the substrate is increased, thereby improving the coating density. More specifically, the rotation speed of the rotating sample stage fixture is 150~250 R / min, the up and down movement speed of the spray gun is 15~25 mm / min, and the number of spray gun cycles is 100-200.

[0045] The present invention subsequently preheats the substrate, increasing its temperature. This preheating process reduces the temperature difference between the substrate and the coating, preventing thermal stress caused by excessive temperature difference that could lead to coating cracking and peeling. Simultaneously, it promotes the growth of columnar grains in the coating, inhibiting crack propagation and thus enhancing the bonding strength between the coating and the substrate. The present invention employs a plasma flame to scan and preheat the substrate surface, maintaining a substrate temperature of 100-300°C.

[0046] Finally, this invention involves plasma spraying an alumina coating onto the substrate surface using a suspension of alumina powder. Specifically, this involves plasma spraying a suspension of alumina powder onto the substrate surface to obtain the alumina coating. The alumina powder has a particle size of 1-5 μm; this increased particle size significantly improves the spraying deposition efficiency. The suspension solvent is deionized water, avoiding the introduction of unnecessary carbon impurities caused by organic solvents, and is also more environmentally friendly, economical, and safe.

[0047] In the method for preparing the alumina coating of this invention, the argon flow rate for ion spraying is 20-30 L / min, the nitrogen flow rate is 50-60 L / min, the hydrogen flow rate is 5-15 L / min, the total gas flow rate is 200-300 L / min, the arc current is 200-240 A, and the atomizing gas flow rate is 10-20 L / min.

[0048] This invention addresses coating defect issues, such as porosity, cracks, and unmelted particle distribution, by optimizing the aforementioned parameters of suspension plasma spraying. The alumina coating thickness ranges from 100 to 600 μm.

[0049] Furthermore, the optimization of the process parameters mainly involves the liquid delivery rate, spraying distance, and the amount of suspension dispersant added.

[0050] The present invention will then use scanning electron microscopy to observe the cross-sectional micromorphology and microhardness of the prepared coating, and test the tribological properties of the alumina coating. Specifically, the pretreatment of the surface of the suspension plasma sprayed coating includes grinding with an 800~2000# diamond grinding wheel and then polishing.

[0051] Furthermore, the friction and wear performance test used 6mm Al2O3 as the grinding pair and subjected it to reciprocating friction motion for 30 min under a 10N load.

[0052] Figure 1 Here are actual photos of the plasma spraying equipment used in this invention. Figure 1 As shown.

[0053] Another aspect of the present invention provides a dense, wear-resistant alumina coating prepared by the aforementioned preparation method.

[0054] Furthermore, the thickness of the dense wear-resistant alumina coating is 100~600μm.

[0055] Furthermore, the porosity of the dense alumina wear-resistant coating is 0.5% to 4.5%.

[0056] Furthermore, the frictional wear rate of the dense alumina wear-resistant coating is 4~25×10⁻⁶. -16 m 3 N -1 m -1 .

[0057] Another aspect of the present invention provides the application of the aforementioned dense alumina wear-resistant coating in the field of wear-resistant and corrosion-resistant white surfaces of irregularly shaped workpieces.

[0058] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0059] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0060] Example 1

[0061] (1) Pre-prepared alumina suspension: The solid content is 20 wt.%, the dispersant is polyethyleneimine with a dispersant concentration of 2.5 wt.%, and deionized water is used as solvent. The suspension is ball-milled for 24 hours.

[0062] (2) Substrate: The substrate is a titanium alloy Ti80 substrate with surface sandblasting treatment. The experimental sample is as follows: Figure 8 After sandblasting, use a compressed air high-pressure gun to clean the surface of the substrate of any remaining spray, particles and dust, and then install it on the rotating sample stage fixture.

[0063] (3) Spraying technology: The surface of the substrate is preheated to 150°C using plasma flame scanning. The spraying process parameters are set, and a suspension plasma spraying technology is used to deposit an alumina suspension onto the substrate surface through the axial delivery of the spray gun to obtain an alumina coating. The movement of the spray gun is achieved by mounting a plasma spray gun on a robotic arm. The robotic arm movement speed is set to 15 mm / s, the spraying distance is 120 mm, and the number of spraying cycles is 150. The turntable speed is set to 225 R / min to increase the surface speed of the substrate.

[0064] Argon flow rate was 25 L / min, nitrogen flow rate was 60 L / min, hydrogen flow rate was 15 L / min, total gas flow rate was 220 L / min, arc current was 220 A, spraying power was 140 kW, liquid delivery rate was 60 ml / min, atomizing gas flow rate was 15 L / min, and the surface temperature of the substrate during spraying was 400℃. Compressed air was used to cool the sample during spraying to prevent overheating.

[0065] Furthermore, during suspension feeding, a peristaltic pump is used to transport the suspension from its container to the suspension nozzle, and the suspension is sprayed out through the nozzle and injected axially at high speed into the plasma flame.

[0066] Furthermore, during the spraying process, the rotating sample stage fixture maintains rotational motion, the spray gun axis is orthogonal to the substrate surface, and the spray gun performs up-and-down reciprocating motion.

[0067] Furthermore, after spraying, once the substrate has cooled to approximately room temperature, it is removed from the sample stage fixture for subsequent characterization tests. These tests revealed that the alumina coating prepared using the water-based suspension of this application possesses a highly dense, typical layered structure. The coating cross-section and microstructure are as follows: Figures 3a-3b As shown. The coating thickness is approximately 581.7 micrometers, the coating porosity is approximately 0.9%, and the wear rate under dry friction conditions is 5.39 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 4.98 × 10⁻⁶. -16 m 3 N -1 m -1 A dense, wear-resistant coating.

[0068] Example 2

[0069] (1) Pre-prepared alumina suspension: The solid content is 20 wt.%, the dispersant is polyethyleneimine with a dispersant concentration of 2.5 wt.%, and deionized water is used as solvent. The suspension is ball-milled for 24 hours.

[0070] (2) Substrate: The substrate is a 316L stainless steel substrate with surface sandblasting treatment. The experimental sample size is 25.4mm×3mm. After sandblasting, the residual spray, particles and dust on the surface of the substrate are cleaned with a high-pressure compressed air gun and then installed on the rotating sample stage fixture.

[0071] (3) Spraying technology: The surface of the substrate was preheated to 200℃ using plasma flame scanning. The spraying process parameters were set, and a suspension plasma spraying technology was used to deposit an alumina suspension onto the substrate surface through axial delivery of the spray gun to obtain an alumina coating. The plasma spray gun was mounted on a robotic arm to move the spray gun. The robotic arm movement speed was set to 15mm / s, the spraying distance was 125mm, and the number of spraying cycles was 150. The turntable speed was set to 225R / min to increase the surface velocity of the substrate. The argon flow rate was 25 L / min, the nitrogen flow rate was 60 L / min, the hydrogen flow rate was 15 L / min, the total gas flow rate was 220L / min, the arc current was 220 A, the spraying power was 140 kW, the liquid delivery rate was 45 ml / min, the atomizing gas flow rate was 15 L / min, and the surface temperature of the substrate during the spraying process was 500℃. Compressed air was used to cool the sample during the spraying process to prevent the sample from overheating.

[0072] Furthermore, during suspension feeding, a peristaltic pump is used to transport the suspension from its container to the suspension nozzle, and the suspension is sprayed out through the nozzle and injected axially at high speed into the plasma flame.

[0073] Furthermore, during the spraying process, the rotating sample stage fixture maintains rotational motion, the spray gun axis is orthogonal to the substrate surface, and the spray gun performs up-and-down reciprocating motion.

[0074] Furthermore, after spraying, once the substrate has cooled to approximately room temperature, it is removed from the sample stage fixture for subsequent characterization tests. These tests revealed that the alumina coating prepared using the water-based suspension of this application possesses a highly dense, typical layered structure. The coating cross-section and microstructure are as follows: Figures 4a-4b As shown. The coating thickness is approximately 210.5 micrometers, the coating porosity is approximately 1.9%, and the wear rate under dry friction conditions is 5.37 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 5.25 × 10⁻⁶. -16 m 3 N -1 m -1 A dense, wear-resistant coating.

[0075] Comparative Example 1

[0076] (1) Ti80 titanium alloy was selected as the base material.

[0077] (2) The concentration of the dispersant in the suspension preparation was 2.5 wt.% relative to the solid content.

[0078] (3) The liquid delivery rate of the suspension plasma spraying process is 30 ml / min, and the other parameters follow those in Example 1.

[0079] (4) The coating thickness is approximately 245.6 micrometers, the coating porosity is approximately 3.4%, and the wear rate under dry friction conditions is 20.26 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 10.58 × 10⁻⁶. -16 m 3 N -1 m -1 This indicates that as the liquid delivery rate decreases, the excessively low delivery rate makes the particles more susceptible to deflection by the plasma flow, leading to increased coating porosity, reduced density, and consequently, decreased tribological performance.

[0080] The coating performed poorly after testing and was not suitable for practical applications.

[0081] Comparative Example 2

[0082] (1) Ti80 titanium alloy was selected as the base material.

[0083] (2) The concentration of the dispersant in the suspension preparation was 2.5 wt.% relative to the solid content.

[0084] (3) The process parameters for plasma spraying of suspension are as follows: the spraying distance is 110 mm, and the others follow the same as in Example 1.

[0085] (4) The coating thickness is approximately 266.8 micrometers, the coating porosity is approximately 1.6%, and the wear rate under dry friction conditions is 12.92 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 4.27 × 10⁻⁶. -16 m 3 N -1 m -1 This indicates that increasing the spraying distance reduces the kinetic energy and momentum of the particles, resulting in increased porosity of the coating. The coating's performance was too poor after testing and does not meet the requirements for practical applications.

[0086] Comparative Example 3

[0087] (1) Ti80 titanium alloy was selected as the base material.

[0088] (2) The concentration of the dispersant in the suspension preparation was 2.5 wt.% relative to the solid content.

[0089] (3) The process parameters for plasma spraying of suspension are as follows: the spraying distance is 115 mm, and the others follow the same as in Example 1.

[0090] (4) The coating thickness is approximately 135.1 micrometers, the coating porosity is approximately 1.8%, and the wear rate under dry friction conditions is 13.09 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 11.34 × 10⁻⁶. -16 m 3 N -1 m -1 The coating performed poorly after testing and was not suitable for practical applications.

[0091] Comparative Example 4

[0092] (1) Ti80 titanium alloy was selected as the base material.

[0093] (2) The concentration of the dispersant in the suspension preparation was 2.5 wt.% relative to the solid content.

[0094] (3) The process parameters for plasma spraying of suspension are as follows: spraying distance is 125 mm, and other parameters follow those in Example 1.

[0095] (4) The coating thickness is approximately 319.9 micrometers, the coating porosity is approximately 2.22%, and the wear rate under dry friction conditions is 5.96 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 7.46 × 10⁻⁶. -16 m 3 N -1 m -1 The coating performed poorly after testing and was not suitable for practical applications.

[0096] Comparative Example 5

[0097] (1) Ti80 titanium alloy was selected as the base material.

[0098] (2) The concentration of the dispersant in the suspension preparation was 2.5 wt.% relative to the solid content.

[0099] (3) The process parameters for plasma spraying of suspension are as follows: spraying distance is 130 mm, and other parameters follow those in Example 1.

[0100] (4) The coating thickness is approximately 324.9 micrometers, the coating porosity is approximately 3.85%, and the wear rate under dry friction conditions is 12.08 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 11.35 × 10⁻⁶. -16 m 3 N -1 m -1The coating performed poorly after testing and was not suitable for practical applications.

[0101] Comparative Example 6

[0102] (1) Ti80 titanium alloy was selected as the base material.

[0103] (2) The concentration of the dispersant in the suspension preparation is 1 wt.% relative to the solid content.

[0104] (3) The process parameters for suspension plasma spraying follow those in Example 1.

[0105] (4) The coating thickness is approximately 188.1 micrometers, the coating porosity is approximately 4.23%, and the wear rate under dry friction conditions is 9.46 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 7.75 × 10⁻⁶. -16 m 3 N -1 m -1 The coating performed poorly after testing and was not suitable for practical applications.

[0106] Comparative Example 7

[0107] (1) Ti80 titanium alloy was selected as the base material.

[0108] (2) The concentration of the dispersant in the suspension preparation was 4 wt.% relative to the solid content.

[0109] (3) The process parameters for suspension plasma spraying follow those in Example 1.

[0110] (4) The coating thickness is approximately 193.7 micrometers, the coating porosity is approximately 3.09%, and the wear rate under dry friction conditions is 17.95 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 9.64 × 10⁻⁶. -16 m 3 N -1 m -1 The coating performed poorly after testing and was not suitable for practical applications.

[0111] Comparative Example 8

[0112] (1) Ti80 titanium alloy was selected as the base material.

[0113] (2) The solid content of the suspension was 5 wt.%, and other aspects followed Example 1.

[0114] (3) The coating thickness is approximately 127.1 micrometers, the coating porosity is approximately 8.09%, and the wear rate under dry friction conditions is 47.95 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 19.44 × 10⁻⁶. -16 m 3 N -1 m -1 The coating performed poorly after testing and was not suitable for practical applications.

[0115] Comparative Example 9

[0116] (1) Ti80 titanium alloy was selected as the base material.

[0117] (2) The solid content of the suspension was 25 wt.%, and other aspects followed Example 1.

[0118] (3) The coating thickness is approximately 591.1 micrometers, the coating porosity is approximately 6.18%, and there are incompletely melted particles. The wear rate under dry friction conditions is 21.84 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 12.83 × 10⁻⁶. -16 m 3 N -1 m -1 The coating performed poorly after testing and was not suitable for practical applications.

[0119] Comparative Example 10

[0120] (1) Ti80 titanium alloy was selected as the base material.

[0121] (2) Suspension plasma spraying process parameters: spraying power 100kW, other parameters follow Example 1.

[0122] (3) The coating thickness is approximately 160.8 micrometers, the coating porosity is approximately 5.93%, and unmelted particles are present. Under dry friction conditions, the wear rate is 25.31 × 10⁻⁶. -16 m 3 N -1 m -1 The wear rate under seawater friction conditions is 17.56 × 10⁻⁶. -16 m 3 N -1 m -1 The coating performed poorly after testing and was not suitable for practical applications.

[0123] Performance characterization: Figure 2 The hardness, dry friction wear rate, and seawater friction wear rate of the Al2O3 coating prepared in Example 1 of this invention; Figures 3a-3b These are cross-sectional morphology images of the Al2O3 coating prepared in Example 1 of this invention; Figures 4a-4b These are cross-sectional morphology images of the Al2O3 coating prepared in Example 2 of this invention; Figures 5a-5b This is the friction coefficient curve of the Al2O3 coating prepared in Examples 1-2 of this invention under a 10N load; Figure 6 These are cross-sectional hardness diagrams of the Al2O3 coatings prepared in the embodiments and comparative examples of the present invention; Figures 7a-7d These are dry friction and wear microstructure images of the Al2O3 coating prepared in the embodiments of the present invention. Figure 7a , Figure 7c This is a microscopic morphology image of Example 1. Figure 7b , Figure 7d This is a microscopic morphology diagram of Example 2.

[0124] This invention first alters the viscosity of the suspension by changing the amount of dispersant added, and then changes the feed rate and spraying distance, thereby affecting the diameter of the suspension mist and the size of the atomized droplets in the plasma flame, as well as the thermal momentum of the droplets in the plasma flame. This controls the size and shape of the deposits formed, thus changing the coating structure and resulting in a dense alumina coating. Because the embodiment exhibits a good coating structure and cohesive strength (high hardness), it demonstrates excellent wear resistance. Figures 7a-7d The friction and wear morphology can be observed. The dry friction and wear mechanism in the embodiment is mainly typical abrasive wear and weak adhesive wear. Cracks, peeling and transfer of coating material were observed, indicating that the coating has a certain ability to resist external fretting wear and other wear under actual friction and wear conditions. The dense structure also prevents external corrosive media from entering the coating through the pores and corroding the substrate.

[0125] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0126] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for producing a suspension plasma sprayed alumina dense wear resistant coating, characterized in that, The method comprises the following steps: preprocessing the substrate; applying an alumina suspension to the surface of the substrate by axial suspension plasma spraying, comprising the following steps: fixing the substrate on a rotating sample table clamp, preheating the surface of the substrate to 100-300 DEG C, then keeping the rotating sample table clamp rotating or overturning, the spraying gun axis is perpendicular to the surface of the substrate, and the spraying gun reciprocates up and down, thereby preparing an alumina dense wear-resistant coating. The content of alumina in the alumina suspension is 10-20 wt%, and the content of dispersant is 1-5 wt%; the process parameters of the axial suspension plasma spraying technology include: the spraying gun power is 125-150 kW, the spraying distance is 50-150 mm, the liquid feeding rate is 30-120 ml / min, and the surface temperature of the substrate during spraying is 300-600 DEG C.

2. The production method according to claim 1, characterized by, The process parameters of the axial suspension plasma spraying technology include: the argon flow rate of plasma spraying is 20-30 L / min, the nitrogen flow rate is 50-60 L / min, the hydrogen flow rate is 5-15 L / min, the total gas flow rate is 200-300 L / min, the arc current is 200-240 A, and the atomizing gas flow rate is 10-20 L / min.

3. The production method according to claim 1, characterized by, The method comprises the following steps: The rotating speed of the rotating sample table clamp is 150-250 R / min, the up and down moving speed of the spraying gun is 15-25 mm / min, and the spraying gun cycle number is 100-200 times.

4. The method of claim 3, wherein: The surface of the substrate is preheated to 100-300 DEG C by plasma flame scanning; wherein the cycle number of the plasma flame scanning is 2-4 times.

5. The method of claim 3, wherein: The material of the substrate includes any one of metal, ceramic and glass.

6. The method of claim 3, wherein: The thickness of the substrate is 1-100 mm.

7. The method of claim 3, wherein: The substrate includes a special-shaped workpiece substrate.

8. The method of claim 1, wherein, The method comprises the following steps: The substrate is cleaned and sand blasted, and then the floating dust on the surface of the substrate is blown away by a high-pressure air gun.

9. The production method according to claim 8, characterized by, The method comprises the following steps: The substrate is ultrasonically cleaned by ethanol; wherein the frequency of the ultrasonic cleaning is 20-80 Hz, and the cleaning time is 10-20 min.

10. The method of claim 8, wherein: The sand blasting is performed by using alumina gravel; wherein the alumina gravel includes alumina white corundum sand, and the particle size of the alumina white corundum sand is 80-120 mesh.

11. The method of claim 8, wherein: The pressure of the sand blasting is 0.5-1 MPa.

12. An alumina dense wear-resistant coating prepared by the preparation method of any one of claims 1-11.

13. The aluminum oxide densi fied wear coating of claim 12, wherein: The thickness of the alumina dense wear-resistant coating is 100-600 μm.

14. The aluminum oxide densi fied wear coating of claim 12, wherein: The porosity of the alumina dense wear-resistant coating is 0.5%-4.5%.

15. The aluminum oxide densi fied wear coating of claim 12, wherein: The friction specific wear rate of the aluminum oxide dense wear resistant coating is 4-25 x 10 -16 m 3 N -1 m -1 .

16. The application of the alumina dense wear-resistant coating of any one of claims 12-15 in the field of wear-resistant and corrosion-resistant surface of a special-shaped workpiece.

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