A temperature-control coating with long life, heat resistance and high emissivity and its preparation process

Abstract

The present invention belongs to the field of heat-resistant high-emissivity coatings and composite materials thereof, and specifically relates to a temperature-controlled coating with long-life heat resistance and high emissivity and a preparation process thereof. The coating is composed of an organic film-forming substance and a filler, wherein the filler is uniformly dispersed in the organic film-forming substance, and the mass of the organic film-forming substance accounts for 40 to 60%; wherein the organic film-forming substance is composed of an organic silicone resin, an amino resin, a hydroxy acrylic resin and a silane coupling agent, and the filler is composed of an organic bentonite, talcum powder, an enamel powder 1 with a softening point of 400°C, an enamel powder 2 with a softening point of 500°C and copper chrome black. The preparation steps of the coating are: (1) substrate treatment, (2) coating preparation, (3) coating spraying, and (4) coating baking and cooling. The coating involved in the present invention has the characteristics of high-temperature corrosion resistance, oxidation resistance, high emissivity and high bonding strength, and provides long-term protection for metal materials and components that are exposed to extreme thermal fatigue temperature change environments for a long time.

Description

Technical Field

[0001] The present invention belongs to the field of heat-resistant high-emissivity coatings and composite materials thereof, and specifically relates to a temperature-controlled coating with long life, heat resistance and high emissivity and a preparation process thereof, wherein the coating can achieve long-term protection for metal materials and components that are exposed to extreme thermal fatigue and temperature change environments for a long time. Background Art

[0002] With the commissioning of new models of land-based and sea-based aircraft, the shortcomings of my country's aerospace equipment in high and low temperature resistant protective coating technology have gradually been exposed. Existing coatings / paints are basically unable to meet the coupling problem of high-speed and complex environment causing high-temperature oxidation and normal-temperature corrosion of the body materials. This has restricted the service level of our military aircraft and other equipment, such as maintenance intervals, combat range, combat duty efficiency, etc. There is a large gap between my country's high-temperature protective coating technology and that of Europe, the United States, Russia and other countries, and the technical indicators are generally low.

[0003] According to the principles of flight dynamics, when the aircraft is flying at a Mach number of 2.5, the skin temperature will reach 140-170°C. When the Mach number is 4.0, the skin temperature may exceed 400°C, and the leading edge of the wing and the air inlet may exceed 650°C or even 700°C. The mechanical strength and mechanical properties of titanium alloys decrease sharply with the increase of temperature, which becomes its fatal weakness in the application of supersonic missiles and key hot end components of aircraft; in addition, at medium temperatures above 650°C, the oxidation rate of titanium alloys is very high, forming loose oxide scales, thereby accelerating alloy corrosion, and causing thermal stress and strain in the matrix, deteriorating material properties. The rise in skin temperature when an aircraft flies in dense air can be composed of three parts: 1. Ambient temperature, which is the temperature of the air around the aircraft, and heat is transferred to the alloy surface and interior through heat conduction; 2. Surface friction heat, when dense air and the aircraft move at high speed relative to each other, the strong friction between the airflow and the surface produces high temperature; 3. Aerodynamic heating, the kinetic energy of the high-speed airflow in the boundary layer is directly converted into the internal energy of the gas, which is the heat load directly felt by the structural material. The gas temperature rises sharply and heats the matrix. As the flight speed of the aircraft increases, aerodynamic heating will occupy an absolute position. Therefore, it is very important to improve the temperature tolerance and oxidation resistance of titanium alloys.

[0004] In order to improve the performance of metal materials in high temperature environments and extend their service life, high temperature resistant and high emissivity temperature control coating technology has emerged. With the rapid development of aerospace technology, there is an urgent need for a multifunctional high temperature resistant and high emissivity protective layer to increase thermal radiation and improve the heat dissipation of equipment surfaces. Among them, the modified organic silicon high emissivity coating not only has the advantages of ordinary ceramic coatings such as high temperature resistance, corrosion resistance, oxidation resistance, and good chemical stability, but also has excellent radiation heat dissipation capabilities. It is widely used in energy saving of industrial kilns, improving the thermal efficiency of infrared heaters, and aerospace thermal control. Summary of the invention

[0005] The purpose of the present invention is to provide a temperature-controlled coating with long service life, high temperature resistance and high emissivity and a preparation process thereof, so that the coating has the characteristics of high temperature corrosion resistance, oxidation resistance, high emissivity and high bonding strength.

[0006] The technical solution of the present invention is:

[0007] A temperature-control coating with long life, heat resistance and high emissivity, the coating consists of an organic film-forming substance and a filler, the filler is uniformly dispersed in the organic film-forming substance, and the mass of the organic film-forming substance accounts for 40-60%; wherein the organic film-forming substance is composed of silicone resin, amino resin, hydroxy acrylic resin and silane coupling agent, and the filler is composed of organic bentonite, talcum powder, enamel powder 1 with a softening point of 400°C, enamel powder 2 with a softening point of 500°C and copper chrome black.

[0008] The temperature-control coating with long life, heat resistance and high emissivity has the following contents of various components in the coating by mass percentage: 15-30% of organic silicone resin, 15-25% of amino resin, 5-15% of hydroxy acrylic resin, 2-5% of silane coupling agent, 2-5% of organic bentonite, 5-10% of talc, 8-15% of enamel powder 1 with a softening point of 400°C, 10-18% of enamel powder 2 with a softening point of 500°C, and 10-17% of copper chrome black.

[0009] The silane coupling agent of the temperature-control coating with long service life, heat resistance and high emissivity is gamma-aminopropyltriethoxysilane (KH550).

[0010] The temperature-control coating with long service life, heat resistance and high emissivity is composed of the following components in terms of mass percentage: 30-35% silicon dioxide, 15-20% boron oxide, 10-15% sodium oxide, 5-10% potassium oxide, 5-10% calcium oxide, 5-10% aluminum oxide, 5-10% ferrosoferric oxide and 2-5% manganese oxide for the enamel powder 1 with a softening point of 400°C: 30-35% silicon dioxide, 15-20% boron oxide, 10-15% sodium oxide, 10-15% potassium oxide, 5-10% calcium oxide, 5-10% aluminum oxide, 5-10% ferrosoferric oxide and 2-5% manganese oxide for the enamel powder 2 with a softening point of 500°C: 40-45% silicon dioxide, 10-15% boron oxide, 8-12% sodium oxide, 5-10% potassium oxide, 4-8% calcium oxide, 5-10% aluminum oxide, 5-10% ferrosoferric oxide and 2-5% manganese oxide for the enamel powder 2 with a softening point of 500°C.

[0011] A preparation process for a temperature-controlled coating with long life, heat resistance and high emissivity, the preparation steps comprising: (1) substrate treatment, (2) coating preparation, (3) coating spraying, and (4) coating baking and cooling.

[0012] The preparation process of the temperature-control coating with long life, heat resistance and high emissivity, step (1) substrate treatment process is specifically: the metal substrate is sandblasted with white corundum sand according to the national standard Sa2.5 to make the surface roughness of the substrate Ra <0.6μm, and then the metal substrate is cleaned with a mixed solvent of anhydrous ethanol and acetone and dried.

[0013] The preparation process of the temperature-control coating with long life, heat resistance and high emissivity, step (2) of the coating preparation process is specifically as follows: first, the silicone resin, amino resin and hydroxy acrylic resin are respectively dissolved in a solvent to form a silicone resin diluent, an amino resin diluent and a hydroxy acrylic resin diluent with a mass fraction of 40-50%, and then the three resin diluents are mixed, and stirred at 600-1000r / min for 10-15min using a high-speed stirrer until a mixed resin is formed that is uniform and transparent; then, the organic bentonite, talcum powder, and softening Enamel powder 1 with a softening point of 400°C, enamel powder 2 with a softening point of 500°C and copper chrome black are added to the mixed resin respectively, and a high-speed stirrer is used to stir and disperse them at a speed of 1000-1500r / min for 10-30min to form a mixture; then, silicate ground zirconium beads accounting for 60-80% of the total mass of the mixture are added, and a high-speed stirrer is used to disperse them at 2000-2600r / min for 0.5-2 hours; finally, a silane coupling agent is added, and a solvent is used to adjust the viscosity of the coating, and the coating flow rate is 20-29 seconds for four cups.

[0014] In the preparation process of the temperature-controlled coating with long service life, heat resistance and high emissivity, the solvent is xylene, and the mass percentage of xylene in the coating is 20% to 60%.

[0015] The preparation process of the temperature-controlled coating with long life, heat resistance and high emissivity, step (3) the paint spraying process is specifically as follows: the coating is prepared by room temperature air spraying, the spraying pressure is 0.2-0.4 MPa, the distance between the nozzle of the paint spray gun and the metal substrate is 15-25 cm, and the spraying is carried out in an alternating manner parallel to and perpendicular to the metal substrate; the coating thickness is controlled by the number of spraying times, the thickness of each spraying is 25-35 μm, and the total coating thickness is 50-300 μm.

[0016] The preparation process of the temperature-controlled coating with long life, heat resistance and high emissivity, step (4) coating baking and cooling process is specifically: carried out in the atmosphere, without the need for a vacuum or special protective atmosphere environment; the metal substrate is placed at a temperature of 80 to 120° C. for curing for 2 to 4 hours, and then cooled to room temperature in the atmosphere.

[0017] The design concept of the present invention is:

[0018] The present invention uses a uniform mixture of silicone resin, amino resin and hydroxy acrylic resin as the organic framework of the composite coating, which ensures the excellent high-temperature corrosion resistance of the coating and its good interface bonding strength with different alloy substrates; the temperature-controlling film-forming, high emissivity and bonding strength of the coating are adjusted through the synergistic effect of fillers, such as controlling the film-forming temperature of the coating and improving the density and heat-resistant and corrosion-resistant performance of the coating during the secondary film-forming process through enamel powders with different softening points, and improving the emissivity of the coating through copper chromium black and ferrous oxide and manganese oxide in the enamel powder. The room-temperature curing (primary film-forming) of the heat-resistant and high-emissivity coating and the synergistic effect of high-temperature secondary film-forming are key technologies for realizing high-temperature service of the coating and satisfying high emissivity and corrosion resistance, and finally obtaining a high-temperature corrosion-resistant and high-emissivity composite coating. In addition, the coating of the present invention also contains specific components: enamel powder 1 with a softening point of 400°C and enamel powder 2 with a softening point of 500°C, which have the following functions: based on the softening flow of the high-temperature enamel phase, an interlocking structure is formed with the organic silicon skeleton, thereby improving the coating's resistance to crack propagation, thereby improving the coating's high-temperature anti-stripping ability, and increasing the bonding force of the two interfaces between the coatings. By adding enamel particles with different softening points to control the secondary film-forming temperature of the coating, high-temperature secondary film-forming or even multiple film-forming of the coating is achieved, the pores left by the volatilization of organic matter are filled, and high-temperature service requirements are met.

[0019] The advantages and beneficial effects of the present invention are:

[0020] 1. The composite coating prepared by the present invention has a simple preparation process, and the raw materials required in the formula can be directly purchased in the market, so the cost is relatively low. The coating is suitable for various metal substrates such as stainless steel, titanium alloy and high-temperature alloy.

[0021] 2. The composite coating prepared by the present invention is dense and free of holes, the resin and filler are evenly distributed, it has high impact toughness and excellent mechanical properties.

[0022] 3. The composite coating prepared by the present invention has secondary film-forming properties under high temperature conditions and can provide excellent high temperature corrosion resistance for a long time.

[0023] 4. The composite coating prepared by the present invention has a high emissivity in the environment of room temperature to 700°C, the emissivity at room temperature of 50°C is above 0.90, and the emissivity at high temperature of 700°C is above 0.80, thereby achieving long-term protection for metal materials and components that are exposed to extreme thermal fatigue and temperature change environments for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the macroscopic morphology of the long-life, heat-resistant and high-emissivity temperature-controlled coating prepared on a stainless steel substrate.

[0025] Figure 2(a)-Figure 2(b) The microscopic morphology of the surface (a) and interface (b) of the long-life, heat-resistant and high-emissivity temperature-controlled coating prepared on a stainless steel substrate.

[0026] Figure 3(a)-Figure 3(b) The emissivity of the long-life, heat-resistant, high-emissivity temperature-controlled coating prepared on a titanium alloy (TC4) substrate at room temperature and high temperature. Among them, Figure 3 (a) is at room temperature t = 50 ° C, Figure 3 (b) is at high temperature t = 650 ° C, the horizontal axis Wavelength is the wavelength (μm), and the vertical axis Spectral Emissivity represents the emissivity.

[0027] Figure 4(a)-Figure 4(b) The microscopic morphology of the surface (a) and interface (b) of the long-life, heat-resistant and high-emissivity temperature-control coating after high-temperature oxidation. DETAILED DESCRIPTION

[0028] The following examples are further detailed descriptions of the present invention. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0029] Embodiment 1:

[0030] In this embodiment, a preparation process of a temperature-controlled coating with long life, heat resistance and high emissivity includes the following steps:

[0031] (1) Taking 15% of solid silicone resin, 17% of amino resin, and 5% of hydroxy acrylic resin by mass percentage, respectively, and dissolving them in xylene to form 50% silicone resin dilution, amino resin dilution, and hydroxy acrylic resin dilution; then mixing the three resin dilutions, and stirring and dispersing them at a speed of 800 r / min for 10 min using a high-speed stirrer until the mixture is uniform and transparent to form a mixed resin;

[0032] (2) adding 5% of organic bentonite, 10% of talc, 13% of enamel powder 1 (softening point 400°C), 15% of enamel powder 2 (softening point 500°C), and 17% of copper chrome black to the mixed resin in sequence, stirring and dispersing them at a speed of 1300 r / min for 15 minutes using a high-speed stirrer to uniformly form a mixture;

[0033] The composition of the enamel powder 1 with a softening point of 400° C. is as follows, in terms of mass percentage: 32% silicon dioxide, 18% boron oxide, 13% sodium oxide, 7% potassium oxide, 8% calcium oxide, 9% aluminum oxide, 10% ferrosoferric oxide, and 3% manganese oxide.

[0034] The composition of the enamel powder 2 with a softening point of 500° C. is as follows, in terms of mass percentage: 45% silicon dioxide, 12% boron oxide, 10% sodium oxide, 8% potassium oxide, 6% calcium oxide, 7% aluminum oxide, 9% ferrosoferric oxide, and 3% manganese oxide.

[0035] (3) adding 80% of the total mass of the mixture into ground zirconium beads, and grinding and dispersing the mixture using a high-speed mixer at a speed of 2300 r / min for 0.5 h;

[0036] (4) Add 3% of silane coupling agent (KH550) by mass percentage, and use xylene to adjust the viscosity of the coating. The flow rate of four cups is about 26 seconds, and then filter the coating with a 250-mesh gauze.

[0037] (5) After the coating was sprayed onto the sandblasted stainless steel surface sample, it was cured at 100°C for 3 hours, the oven was closed, the coated sample was taken out of the oven, and the sample was cooled to room temperature in the atmosphere. The total weight of the organic film-forming substance in the coating accounted for 40%.

[0038] like Figure 1 As shown, the macroscopic morphology of the prepared composite coating is black and shiny with no obvious defects.

[0039] Embodiment 2:

[0040] The difference from Example 1 is that the composite coating formula is changed to:

[0041] By mass percentage, solid organic silicone resin 25%, amino resin 20%, hydroxy acrylic resin 10%, silane coupling agent (KH550) 5%, organic bentonite 5%, talc 5%, enamel powder 1 (softening point 400℃) 8%, enamel powder 2 (softening point 500℃) 10%, copper chrome black 12%. Among them, the total mass of organic film-forming substances accounts for 60%;

[0042] The coating thickness of this embodiment is about 100 μm. The prepared composite coating has a dense structure and a surface morphology similar to Figure 1 Similar, good bonding with the alloy interface, no obvious large hole defects, no cracks, etc.

[0043] Embodiment 3:

[0044] The difference from Example 1 is that the composite coating formula is changed to:

[0045] By mass percentage, solid organic silicone resin 20%, amino resin 20%, hydroxy acrylic resin 6%, silane coupling agent (KH550) 4%, organic bentonite 3%, talc 5%, enamel powder 1 (softening point 400℃) 12%, enamel powder 2 (softening point 500℃) 15%, copper chrome black 15%. Among them, the total mass of organic film-forming substances accounts for 50%;

[0046] The coating thickness of this embodiment is about 100 μm. The prepared composite coating has a dense structure and a surface morphology similar to Figure 1 Similar, good bonding with the alloy interface, no obvious large hole defects, no cracks, etc.

[0047] Embodiment 4:

[0048] The difference from Example 3 is that the coating is baked and cured at 120°C for 2 hours. The coating is dense and has no obvious surface defects, similar to Figure 1 shown.

[0049] Embodiment 5:

[0050] The difference from Example 3 is that the coated alloy substrate is a high-temperature alloy surface, the coating thickness is 100 μm, the surface is intact, and there is no obvious apparent defect, similar to Figure 1 The microscopic morphology and cross section of the coating surface are shown in Figure 2. It can be found that the coating has good interface bonding with the high-temperature alloy, the filler is dispersed and evenly distributed in the organic film-forming substance, and has good interface bonding with the organic film-forming substance. The internal structure of the coating is dense, without obvious defects such as large holes, which is conducive to preventing the infiltration of external corrosive media.

[0051] Embodiment 6:

[0052] The difference from Example 3 is that the coated alloy substrate is a titanium alloy (TC4) surface, the coating thickness is 100 μm, the surface is intact, and there is no obvious apparent defect, similar to Figure 1 As shown in Figure 2, the coating surface microstructure and cross section are shown in Figure 2. It can be found that the coating has good interface bonding with the titanium alloy, the internal structure of the coating is dense, and there are no obvious defects such as large holes. After the emissivity test, the results are shown in Figure 3. The emissivity at room temperature of 50°C is about 0.92, and the emissivity at high temperature of 650°C is about 0.85.

[0053] Embodiment 7:

[0054] The difference from Example 3 is that the thickness of the coating is reduced to 50 μm. The coating surface is intact, without obvious surface defects, and the microstructure is similar to Figure 2. After high-temperature oxidation at 400°C for 20 hours, as shown in Figure 4(a), there are no cracks on the coating surface; at the same time, as shown in Figure 4(b), there are no cracks in the cross section, and the coating thickness is about 50 μm.

Claims

1. A temperature-control coating with long life, heat resistance and high emissivity, characterized in that: The coating is composed of an organic film-forming substance and a filler, wherein the filler is uniformly dispersed in the organic film-forming substance, and the mass of the organic film-forming substance accounts for 40 to 60%; wherein the organic film-forming substance is composed of an organic silicone resin, an amino resin, a hydroxy acrylic resin and a silane coupling agent, and the filler is composed of an organic bentonite, talcum powder, an enamel powder 1 with a softening point of 400°C, an enamel powder 2 with a softening point of 500°C and copper chrome black; The contents of the components in the coating are as follows by mass percentage: 15-30% of organic silicone resin, 15-25% of amino resin, 5-15% of hydroxy acrylic resin, 2-5% of silane coupling agent, 2-5% of organic bentonite, 5-10% of talc, 8-15% of enamel powder 1 with a softening point of 400°C, 10-18% of enamel powder 2 with a softening point of 500°C, and 10-17% of copper chrome black; The composition of enamel powder 1 with a softening point of 400°C is as follows, calculated by mass percentage: 30-35% silicon dioxide, 15-20% boron oxide, 10-15% sodium oxide, 5-10% potassium oxide, 5-10% calcium oxide, 5-10% aluminum oxide, 5-10% ferrosoferric oxide, and 2-5% manganese oxide; the composition of enamel powder 2 with a softening point of 500°C is as follows, calculated by mass percentage: 40-45% silicon dioxide, 10-15% boron oxide, 8-12% sodium oxide, 5-10% potassium oxide, 4-8% calcium oxide, 5-10% aluminum oxide, 5-10% ferrosoferric oxide, and 2-5% manganese oxide.

2. The temperature-control coating with long life, heat resistance and high emissivity according to claim 1, characterized in that: The silane coupling agent is γ-aminopropyltriethoxysilane.

3. A process for preparing a temperature-control coating with long life, heat resistance and high emissivity as claimed in any one of claims 1 to 2, characterized in that: The preparation steps are: (1) metal substrate treatment, (2) coating preparation, (3) coating spraying, and (4) coating baking and cooling.

4. The process for preparing a temperature-control coating having a long life, heat resistance and high emissivity according to claim 3, characterized in that: The metal substrate treatment process of step (1) is specifically as follows: the metal substrate is sandblasted with white corundum sand according to the national standard Sa2.5 to make the surface roughness of the metal substrate Ra <0.6 μm, and then the metal substrate is cleaned with a mixed solvent of anhydrous ethanol and acetone and dried.

5. The process for preparing a temperature-control coating having a long life, heat resistance and high emissivity according to claim 3, characterized in that: The coating preparation process of step (2) is specifically as follows: first, organic silicone resin, amino resin and hydroxy acrylic resin are respectively dissolved in a solvent to form organic silicone resin diluent, amino resin diluent and hydroxy acrylic resin diluent with a mass fraction of 40-50%, then the three resin diluents are mixed, and a high-speed stirrer is used to stir for 10-15 minutes at 600-1000 r / min until the mixture is uniform and transparent to form a mixed resin; then, organic bentonite, talcum powder, enamel powder 1 with a softening point of 400°C, enamel powder 2 with a softening point of 500°C and copper chrome black are respectively added to the above mixed resin, and a high-speed stirrer is used to stir and disperse for 10-30 minutes at a speed of 1000-1500 r / min to form a mixture; then, silicate ground zirconium beads accounting for 60-80% of the total mass of the mixture are added, and a high-speed stirrer is used to stir and disperse at a speed of 2000-2600 r / min. r / min for 0.5 to 2 hours; finally, add silane coupling agent and use solvent to adjust the viscosity of the coating, and the flow rate of coating four cups is 20 to 29 seconds.

6. The process for preparing a temperature-control coating having a long life, heat resistance and high emissivity according to claim 5, characterized in that: The solvent is xylene, and the mass percentage of xylene in the coating is 20% to 60%.

7. The process for preparing a temperature-control coating with long life, heat resistance and high emissivity according to claim 3, characterized in that: The specific process of the paint spraying in step (3) is as follows: the coating is prepared by air spraying at room temperature, the spraying pressure is 0.2-0.4 MPa, the distance between the nozzle of the paint spray gun and the metal substrate is 15-25 cm, and the spraying is carried out in an alternating manner of parallel and vertical to the metal substrate; the coating thickness is controlled by the number of spraying times, the thickness of each spraying is 25-35 μm, and the total coating thickness is 50-300 μm.

8. The process for preparing a temperature-control coating having a long life, heat resistance and high emissivity according to claim 3, characterized in that: The coating baking and cooling process in step (4) is specifically as follows: it is carried out in the atmosphere without the need for a vacuum or special protective atmosphere environment; the metal substrate is placed at a temperature of 80 to 120° C. for curing for 2 to 4 hours, and then cooled to room temperature in the atmosphere.

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