High-strength, high-toughness and high-combination ceramic insulating coating as well as preparation and application thereof

Abstract

The invention relates to a high-strength, high-toughness and high-combination ceramic insulating coating as well as preparation and application thereof. Aiming at the problems that an existing ceramic coating is poor in interface bonding, complex in high-temperature process and insufficient in performance, tellurium oxide, antimony oxide, vanadium oxide, diopside and the like are innovatively adopted as ultralow-melting-point auxiliary phase materials to be compounded with high-melting-point oxide ceramic main phases (such as Al2O3, TiO2 and the like), composite powder (the volume ratio of the main phases is 50%-98%, and the volume ratio of the auxiliary phases is 2%-50%) is prepared through a mechanical mixing or nano-agglomeration method, and the composite powder is prepared through a high-temperature sintering method. And the coating is deposited by combining a low-temperature thermal spraying process (the temperature of the matrix is 100-250 DEG C). According to the process, tellurium oxide and the like are fused to fill pores and reduce the critical deposition temperature of a main phase, so that the coating has high bonding strength, low porosity, high toughness and excellent insulativity. Compared with the prior art, comprehensive performance breakthrough is achieved under the low-temperature condition, the anti-impact energy is larger than or equal to 5 J, and the long-acting galvanic corrosion protection coating is suitable for long-acting galvanic corrosion protection of steel-titanium and other dissimilar metal connecting faces in ocean engineering and has remarkable technical advantages and industrial application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of materials engineering technology, and specifically relates to a high-strength, high-toughness and high-strength combined ceramic insulating coating and its preparation and application, which is particularly suitable for galvanic corrosion protection of heterogeneous metal connectors in marine engineering. Background Art

[0002] In marine environments, galvanic corrosion is a prominent problem at the joints of dissimilar metals (such as ship hull steel and titanium alloy). Seawater, acting as an electrolyte, accelerates the galvanic cell reaction, causing rapid corrosion of the anode metal, threatening the sealing and safety of equipment. Currently, traditional plasma-sprayed ceramic insulating coatings are widely used due to their low electrical conductivity. However, plasma-sprayed ceramic coatings have the following drawbacks: 1. Weak interface bonding: The proportion of unbonded interfaces between the coating and the substrate, and between layers is high (the effective bonding rate is only about 1 / 3), resulting in low bonding strength (≤25MPa) and high porosity (≥5%). 2. Intrinsic brittleness: Poor toughness and insufficient impact resistance. 3. Price and stability limitations: Existing technologies that increase density by adding relatively expensive bismuth oxide or potassium titanate have poor phase stability and are prone to phase transformation under high-temperature service conditions, resulting in weakened coating performance.

[0003] For example, although the ceramic composite powder disclosed in patent document CN 116574991 A increases the bonding strength to ≥30MPa and reduces the porosity to ≤4%, the compatibility and synergy of the auxiliary phase materials bismuth oxide or potassium titanate with the main phase material are limited, and bismuth oxide has poor phase stability at high temperatures. It undergoes a phase transition at 730°C, from the α phase to the δ phase, and transforms into the β phase when cooled to 650°C, and further transforms into the γ phase when cooled to 639°C. The phase transition is accompanied by volume changes, which affects the coating performance. In addition, the raw material price of bismuth oxide is relatively high and the processing is difficult, which further increases the processing cost; while potassium titanate is expensive, and the processing technology is complex and difficult.

[0004] In summary, the existing technology is still unable to prepare high bonding strength (≥50 MPa), low porosity (≤2%), high toughness (≥4 MPa·m 1 / 2 ) and structurally stable ceramic insulating coatings with excellent impact resistance, it is urgent to develop low-cost new material systems and low-temperature preheating processes to break through the bottleneck of traditional technology.

[0005] The information disclosed in this background technology section is only used to deepen the understanding of the background technology of the present disclosure and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0006] In response to the bottleneck problems of poor interface bonding, difficult high-temperature deposition, and limited performance improvement in ceramic insulating coatings in the prior art, the present invention provides a high-strength, high-toughness, and high-strength ceramic insulating coating and a low-temperature preheating thermal spray preparation method thereof. By introducing a low-melting-point auxiliary phase material (such as TeO2, V2O5, CaMgSi2O6, etc.) with good compatibility with the main phase material, the composite powder system and process parameters are synergistically optimized, and the critical deposition temperature of the main phase ceramic is significantly reduced to 100-250°C. Under low-temperature preheating deposition conditions, the coating achieves a bonding strength of ≥50 MPa, a porosity of ≤2%, and a fracture toughness of ≥4 MPa·m 1 / 2 and impact energy ≥5 J, which is significantly better than existing technologies and has wider process adaptability, especially suitable for large and complex components.

[0007] The technical solutions adopted include: 1. Ceramic composite powder matching design ① Main phase material: A high-melting-point oxide ceramic material with a melting point of 1500~2500℃ is selected from at least one of aluminum oxide (Al2O3), titanium oxide (TiO2), chromium oxide (Cr2O3), lanthanum oxide (La2O3), silicon oxide (SiO2), yttrium oxide (Y2O3), and zirconium oxide (ZrO2), for example, a binary combination (Al2O3-TiO2, Y2O3-ZrO2), accounting for 50%~98% by volume.

[0008] ② Auxiliary phase materials: low melting point (600~1400℃) insulating ceramic materials antimony oxide (Sb2O3), tellurium oxide (TeO2), vanadium oxide (V2O5), diopside (CaMgSi2O6), bismuth molybdate (Bi2Mo3O 12 ), calcium fluoride (CaF2), accounting for 2% to 50% by volume.

[0009] ③ Synergistic effect: The melting point of the auxiliary phase material is at least 500°C lower than that of the main phase. After melting, it fills the pores of the main phase and lowers the critical deposition temperature of the main phase, achieving low-temperature strong bonding and densification.

[0010] 2. Optimization of low-temperature preheating thermal spraying process ① Substrate temperature control: During spraying, the substrate surface temperature is maintained at 100-250°C (fluctuation range ±10°C), which is achieved by the following methods: empty gun scanning heating before spraying (spray gun speed 100-800 mm / s); external heating device (heating table / heating blanket, laser preheating).

[0011] ② Thermal spraying process: plasma spraying or flame spraying is used, and the parameters are as follows: Plasma spraying: power 30~50 kW, spraying distance 80~120 mm, argon 40~60 slpm, hydrogen 5~10 slpm, powder feed rate 20~40 g / min.

[0012] Flame spraying: oxygen-acetylene fuel, spraying distance 80~120 mm, powder feeding rate 20~30 g / min, power 25~35kW.

[0013] One or more technical solutions provided in the embodiments of this application have at least any of the following technical effects or advantages: 1. Material system innovation: TeO2, V2O5, and other materials are used for the first time as low-melting-point auxiliary phases, breaking the existing technology's reliance on expensive materials with poor high-temperature phase stability such as Bi2O3, and achieving a reduction of the critical deposition temperature of the main phase by more than 40% (for example, Al2O3 is reduced from 300°C to 100°C).

[0014] 2. Process innovation: By combining low-temperature deposition (100-250°C) with auxiliary phase melt filling, the interface bonding strength and density are simultaneously improved, overcoming the limitations of high-temperature preheating deposition processes on large components.

[0015] 3. Improved coating performance: Bond strength ≥50 MPa (66% improvement compared to ≥30 MPa for existing technologies); Porosity ≤2% (50% reduction compared to ≤4% for existing technologies); Fracture toughness ≥4 MPa·m¹ / ²; Impact energy ≥5 J (25% improvement compared to ≥4 J for existing technologies), meeting the demands of demanding marine operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Surface morphology of materials in the examples of this application; among them, (a) surface morphology of AT13 main phase powder; (b) surface morphology of TeO2 auxiliary phase powder.

[0017] Figure 2 The cross-sectional microstructures of the coatings produced by different processes in the embodiments of the present application are shown in Figures 1 and 2. (a) low-magnification of the AT13 coating at room temperature; (b) high-magnification of the AT13 coating at room temperature; (c) low-magnification of the AT13-TeO2 coating at 100°C; and (d) high-magnification of the AT13-TeO2 coating at 100°C, showing reduced porosity and enhanced interface bonding. DETAILED DESCRIPTION

[0018] Unless otherwise specified, the instruments and equipment involved in the following examples are all conventional instruments and equipment; the industrial raw materials involved are all commercially available conventional industrial raw materials unless otherwise specified; the tests and preparation methods involved are all conventional methods unless otherwise specified.

[0019] In order to better understand the technical solution of the present application, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0020] Example 1: AT13-TeO2 ternary composite coating (low-temperature preheating plasma spraying) Step 1: Composite powder preparation Main phase material: Al2O3-13%TiO2 (nanopowder, particle size 15~45 μm). Powder surface morphology see Figure 1 a; Auxiliary phase material: TeO2 powder, particle size 45~75 μm, powder surface morphology see Figure 1 b; Ratio: AT13 and TeO2 volume ratio 80:20; Mixing process: V-type mixer, speed 50 rpm, mixing powder for 2 h to obtain uniform composite powder.

[0021] Step 2: Substrate pretreatment and temperature control Substrate material: marine grade 304 stainless steel; surface treatment: sandblasting (Ra = 5-8 μm); temperature control: heating stage maintains substrate temperature at 100°C.

[0022] Step 3: Plasma Spraying Spraying process parameters: power 43 kW, spraying distance 90 mm; argon flow rate 50 slpm, hydrogen flow rate 8 slpm; powder feeding rate 30 g / min, spraying speed 300 mm / s.

[0023] Step 4: Coating performance test like Figure 2 As shown in the figure, the structural density and interface bonding of the AT13-20%TeO2 ternary ceramic composite coating prepared under the above conditions are significantly improved, the coating porosity (metallographic image analysis method) is greatly reduced from 5.6% of the AT13 ceramic coating deposited at room temperature to 1.5%, and the coating bonding strength (GB / T 8642 tensile method) is increased from 25 MPa of the AT13 coating to 51 MPa, further indicating its significantly improved interface bonding. At the same time, the test results show that the hardness of the AT13-20%TeO2 ceramic coating remains above 1000 HV, and the coating fracture toughness (indentation method, load 10 kgf) is 4 MPa·m 1 / 2 , compared with the fracture toughness of AT13 ceramic coating of 2.2 MPa·m 1 / 2 Compared with the conventional steel ball, it is nearly 2 times higher, and its impact energy reaches 5 J (falling ball impact test, steel ball diameter 40 mm, height 1.94 m); and its volume resistivity is 2×10 12Ω·m (volt-ampere method, voltage 100V), indicating excellent insulation protection performance. These results demonstrate that, under deposition conditions significantly below the critical deposition temperature of 300°C for AT13 ceramic material, a ceramic insulating coating with significantly improved interfacial bonding and toughness was obtained. Compared to the 35 MPa bonding strength and 3.8% porosity of the coating in the prior art (CN116574991 A), this coating significantly improved performance while also reducing the deposition temperature by 66%. After 3000 hours of neutral salt spray testing (GB / T10125), the coating showed no corrosion, blistering, cracking, or shedding. The coating also underwent a temperature shock test (CB 20090) of 50 cycles from 500°C to room temperature to -40°C, with no signs of cracking, peeling, or shedding.

[0024] Using the aforementioned process, a ceramic insulating coating was deposited on the surface of a ship's steel flange. The measured insulation resistance between the flange and the mating copper flange was 10 MΩ, significantly greater than the 2Ω resistance without the coating. The flange was subjected to a stamping fatigue test (JB / T 8859-2017) alternating between atmospheric pressure, 5 MPa, and atmospheric pressure for 2000 cycles. The coating remained intact, showing no cracking, peeling, or flaking. A vibration test (GJB 150.16A) was also conducted on the flange at frequencies of 16 to 60 Hz for 2 hours, and the coating showed no signs of damage or cracking.

[0025] Example 2: Al2O3-TeO2 binary composite coating (flame spraying) Step 1: Composite powder preparation Main phase material: Al2O3 powder, particle size 50~100 μm; Auxiliary phase material: TeO2 powder, particle size 50~100 μm; Ratio: Al2O3 and TeO2 volume ratio 90:10; Mixing process: three-dimensional mixer, speed 30 rpm, mixing powder for 1.5 h.

[0026] Step 2: Substrate Temperature Control Matrix material: titanium alloy (Ti-6Al-4V); Temperature control: The spray gun is heated to 200°C by scanning with an empty gun (scanning speed 400 mm / s).

[0027] Step 3: Flame spraying process Spraying parameters: oxygen flow rate 120 L / min, acetylene flow rate 80 L / min; spraying distance 100 mm, powder feeding rate 25 g / min; flame power 30 kW, spraying speed 250 mm / s.

[0028] Step 4: Coating performance test The test results show that the porosity of the Al2O3-10% TeO2 binary ceramic composite coating is only 1.2%, the coating interface bonding is greatly improved, the coating bonding strength reaches 54 MPa, and the fracture toughness is 4.2 MPa·m 1 / 2 The coating's impact resistance was measured using the falling ball method, revealing that it can withstand an impact energy of 5J, significantly higher than the 2J of the Al2O3 coating. This indicates that by adding a low-melting-point ceramic powder to the sprayed ceramic powder, a highly dense, strong, tough, and strongly bonded ceramic insulating coating is achieved at a critical deposition stability temperature significantly lower than the 300°C required for Al2O3 coatings. Galvanic corrosion inhibition was demonstrated: no galvanic current was observed at the steel-titanium flange connection in a 3.5% NaCl solution. After 2500 hours of neutral salt spray testing (GB / T10125), the coating showed no corrosion, blistering, cracking, or shedding. The coating also underwent a temperature shock test (CB 20090) of 600°C to room temperature to -40°C for 50 cycles, revealing no cracking, peeling, or shedding.

[0029] Flame spraying is used to achieve low-temperature deposition, reducing process costs by 30%, and the coating performance comprehensively surpasses plasma-sprayed alumina-based coatings (CN 116574991 A).

[0030] Example 3: Nano-agglomerated TeO2 toughened Al2O3 coating (low-temperature preheating plasma spraying) Step 1: Nanocomposite powder preparation Main phase: nano-Al2O3 (50~100 nm); Auxiliary phase: nano-TeO2 (50~80 nm); Ratio: Al2O3 and TeO2 volume ratio 85:15; Preparation process: Ball milling: zirconia ball media, speed 200 rpm, time 2 h; spray granulation: air inlet temperature 260 °C, feeding rate 60 mL / min; sintering: 600 °C for 3 h, sieving to 40-70 μm.

[0031] Step 2: Plasma Spray Parameters Substrate temperature: 150°C (laser preheating); power 45 kW, argon flow 55 slpm, powder feed rate 35 g / min.

[0032] Step 3: Performance Characterization Porosity: 0.8% (reaching a nearly fully dense level); fracture toughness: 5.1 MPa·m 1 / 2(Crack deflection toughening mechanism); After 3000 hours of neutral salt spray testing (GB / T 10125), the coating showed no corrosion, blistering, cracking, or shedding. The coating also underwent a temperature shock test (CB 20090) with 100 cycles from 700°C to room temperature to -40°C, showing no cracking, peeling, or shedding (better than 20 cycles compared to existing technologies).

[0033] Creativity: Uniform distribution of nano-scale TeO2 achieves ultra-low porosity and ultra-high toughness, breaking through the performance limits of traditional micron-level auxiliary phase materials.

[0034] Example 4: Comparative Experiment Verification 1. Comparison of auxiliary phase material properties Experimental Design: Using the same primary phase (Al₂O₃) and the same process conditions (Example 1), coatings were prepared using TeO₂ (present invention) and bismuth oxide / potassium titanate (reference document CN 116574991 A) as auxiliary phases, and their performance was tested. The test results are shown in Table 1.

[0035] Table 1 Comparison of coating performance indicators of different auxiliary phase materials .

[0036] From the above comparison, it can be seen that TeO2 can significantly reduce the critical deposition temperature, and its performance is superior to existing auxiliary phase materials in all aspects.

[0037] 2. Verification of the necessity of low temperature process Experimental Design: A fixed primary phase (Al₂O₃) and auxiliary phase (TeO₂, 80:20 volume ratio) were used to prepare coatings at different substrate temperatures (50°C, 100°C, 250°C, and 300°C) (other process conditions refer to Example 1). The performance of the coatings was then tested. The results are shown in Table 2.

[0038] Table 2 Coating performance indicators under different substrate temperature conditions .

[0039] From the above results, it can be seen that 100~250℃ is the optimal performance range. High bonding strength and low porosity can be achieved at low temperatures without the need for high-temperature processes.

[0040] Example 5: Extended Example and Boundary Condition Test Verification 1. Main / auxiliary phase ratio optimization experiment Experimental design: The main phase (Al2O3) was fixed, and the volume proportion of TeO2 was adjusted (1%, 10%, 20%, 40%, 60%). The coating was prepared according to the process conditions of Example 1, and the coating performance was tested. The results showed (see Table 3) that 2%~50% was the effective range. If the auxiliary phase was too low, it could not fill the pores. If it was too high, it would cause a large amount of volatilization, increase the porosity of the coating, and reduce the bonding strength of the coating.

[0041] Table 3 Coating performance indicators with different proportions of auxiliary phase materials .

[0042] 2. Verification of adaptability to complex matrices Experimental Design: Coatings (AT13-20% TeO2, preheated to 100°C, other process conditions refer to Example 1) were prepared on hull steel, titanium alloy, aluminum alloy, and magnesium alloy substrates, and the bonding strength and insulation properties were tested. The test results show (see Table 4) that the coating has a bonding strength of ≥45 MPa and a volume resistivity of ≥10 on various substrates. 11 Ω·m.

[0043] Table 4 Coating performance indicators of different substrates .

[0044] Example 6: Test Verification of Boundary Conditions of Coating Preparation Process Parameters 1. Relationship between spraying power and bonding strength Experimental design: Based on the preparation method in Example 1, the coating was prepared with fixed other parameters (AT13-20% TeO2, preheating temperature 100°C). The plasma spraying power was adjusted (20 kW, 30 kW, 50 kW, 60 kW), and the bonding strength was tested. The results showed (see Table 5) that when the power was less than 30 kW, the bonding strength was less than 40 MPa, 30-50 kW was the optimal range, and >50 kW resulted in overburning.

[0045] Table 5 Coating performance indicators under different spraying powers .

[0046] 2. Effect of powder feeding rate on porosity Experimental Design: Based on the preparation method described in Example 1, the coating (AT13-20% TeO2, preheating temperature 100°C) was prepared with fixed parameters. The powder feed rate was increased from 10 g / min to 50 g / min, and the porosity was measured. The results showed that the porosity was ≤2% when the powder feed rate was 20-40 g / min, and the porosity increased significantly beyond this range.

[0047] Although some preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0048] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of the inventive concept. Thus, if such changes and modifications fall within the scope of the claims of this application and their equivalents, this application is intended to include such changes and modifications.

Claims

1. A high-strength, high-toughness, high-strength combined ceramic insulating coating, characterized in that: The ceramic composite powder is prepared by a thermal spraying process with a low temperature preheating of 100-250°C. The ceramic composite powder includes: Main phase material: high melting point oxide ceramic material with a melting point of 1500~2500℃, which is at least one of aluminum oxide, titanium oxide, chromium oxide, lanthanum oxide, silicon oxide, yttrium oxide, and zirconium oxide, accounting for 50%~98% by volume; Auxiliary phase material: a low-melting-point insulating ceramic material with a melting point of 600-1400°C, selected from at least one of antimony oxide, tellurium oxide, vanadium oxide, diopside, and bismuth molybdate, accounting for 2%-50% by volume; The melting point of the auxiliary phase material is at least 500°C lower than that of the main phase material, and the auxiliary phase material is melted to fill the pores of the main phase coating and reduce the critical deposition temperature of the main phase material to 100-250°C, so that the performance of the coating meets the following requirements: bonding strength ≥50MPa, porosity ≤2%, fracture toughness ≥4MPa·m 1 / 2 , the impact energy borne is ≥5 J.

2. The high-strength, high-toughness, high-strength ceramic insulating coating according to claim 1, characterized in that: The auxiliary phase material is at least one of antimony oxide and vanadium oxide, and its volume proportion is 5% to 30%.

3. The high-strength, high-toughness, high-strength ceramic insulating coating according to claim 1, characterized in that: The main phase material is a binary combination of aluminum oxide and tellurium oxide, wherein the mass fraction of tellurium oxide is 5% to 20%, or a binary combination of zirconium oxide and yttrium oxide, wherein the molar fraction of zirconium oxide is 5% to 15%.

4. The method for preparing the high-strength, high-toughness and high-strength ceramic insulating coating according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Preparation of ceramic composite powder: The main phase and auxiliary phase materials are prepared into composite powders of 15-150 microns by mechanical mixing or nano-agglomeration sintering; (2) Low temperature preheating thermal spraying: a. Substrate preheating: Use empty gun scanning heating or external heating device to maintain the substrate surface temperature at 100~250℃; b. Using plasma spraying or flame spraying, the composite powder is heated to a molten or semi-molten state and then sprayed onto the substrate surface to form a coating. During thermal spraying, the temperature of the coating surface is maintained within the desired temperature range by the accumulation of the particles' own temperature during the spraying process.

5. The preparation method according to claim 4, characterized in that The steps of the nano-agglomeration method include: (1) ball milling the nanopowders of the main phase material and the auxiliary phase material, using zirconia balls as the ball milling medium, at a speed of 100-400 rpm for 1-3 h; (2) The composite powder is mixed with a binder, a dispersant, and distilled water in a mass ratio of 100:(1-10):(1-10):(100-400) and ball-milled to form a slurry; (3) The slurry was spray granulated with the following parameters: feeding speed 30~120 mL / min, air inlet temperature 250~300℃, and air outlet temperature 100~130℃; (4) The powder after spray granulation is sintered at high temperature. The sintering temperature is selected according to the auxiliary phase material: When the auxiliary phase material is antimony oxide, tellurium oxide, vanadium oxide or bismuth molybdate, the sintering temperature is 500~800℃; when the auxiliary phase material is diopside, the sintering temperature is 900~1200℃; The sintering time is 1~3 h, and the particles are sieved to a particle size of 15~150 microns.

6. The preparation method according to claim 4, characterized in that The plasma spraying parameters are: power 30-50 kW, spraying distance 80-120 mm, argon flow rate 40-60 slpm, hydrogen flow rate 5-10 slpm, and powder feeding rate 20-40 g / min.

7. The preparation method according to claim 4, characterized in that The flame spraying parameters are: oxygen and acetylene as fuel gas, spraying distance 80-120 mm, powder feeding rate 20-30 g / min, and power 25-35 kW.

8. Application of the high-strength, high-toughness, high-strength ceramic insulating coating according to any one of claims 1 to 3, characterized in that: Used for galvanic corrosion protection of heterogeneous metal connection surfaces in marine engineering, including insulation protection of hull steel and titanium alloy flange connection surfaces, pipeline welding joints or marine equipment sealing surfaces. The coating thickness is 50~500 microns.

Images