A double ceramic layer wear-resistant self-lubricating coating and a preparation method thereof

Abstract

The present application belongs to the field of high-temperature-resistant coating preparation, and particularly relates to a double-ceramic-layer wear-resistant self-lubricating coating and a preparation method thereof. The coating is prepared by ultrasonic flame spraying a nickel-chromium-aluminum-yttrium-silicon (NiCrAlYSi) adhesive bottom layer, ultrasonic flame spraying a nickel-chromium / chromium carbide+fluoride-containing nickel-chromium / chromium carbide eutectic body (NiCr / Cr3C2+NiCr / Cr3C2BaF2·CaF2) as an intermediate layer, and ultrasonic flame spraying a nickel-chromium / chromium carbide eutectic body containing calcium fluoride and barium fluoride and silver (NiCr / Cr3C2-BaF2·CaF2+Ag) as a surface layer. The coating has satisfactory bonding strength and anti-peeling capacity, maximally prolongs the service life under the runway and brush wire high-speed friction and wear environment, avoids the failure and scrapping caused by the peeling of the runway surface coating or the melting and deformation of the brush wire, and improves the sealing effect of the sealing system as a whole.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high-temperature-resistant coating preparation, and particularly relates to a double-ceramic-layer wear-resistant self-lubricating coating and a preparation method thereof. BACKGROUND

[0002] The brush seal of an aero-engine is a contact seal device, which is composed of an interference fit of brush wires and a counter run, and allows the rotor to work in a state with a certain deviation, thus having higher sealing performance. In the aero-engine, the air or gas pressure is high, the temperature is high, the super-high rotating speed can be as high as 30000 rpm, the heat generated by friction is large, and the like, and in the gas turbine, the long service life is also required, so the performance requirements of the brush wires and the run are very high. The run surface is generally sprayed with a wear-resistant coating to resist the wear of the brush wires and to improve the service life of the run. However, due to the harsh environment of the engine, the wear-resistant coating on the run will appear cracks, crazing and peeling, and the brush wires will also appear deformation, burn and other phenomena after being worn, which greatly damages the sealing performance of the brush seal system, so the sealing effect will be greatly affected. Therefore, it is necessary to develop a wear-resistant self-lubricating coating system with high bonding strength, high density and good wear performance with the brush wires and its preparation process suitable for the use of the brush seal.

[0003] To meet the use requirement below 800℃, a nickel-chromium / chromium carbide (NiCr / Cr3C2) wear-resistant coating is usually used. Although the carbide coating enhances the wear resistance of the run surface of the sealing disc, the friction performance of the coating with the brush wires and the thermal shock resistance of the coating with the substrate are insufficient under the working condition environment of high sealing pressure, high environmental temperature and high interface sliding speed of the aero-engine, the single-layer nickel-chromium / chromium carbide coating cracks and peels due to the residual thermal stress caused by the mismatch of thermal expansion between the coating and the metal substrate. The existing research results show that the multi-layer coating system can reduce the thermal stress between the coatings, thus improving the thermal cycle performance of the coating. In addition, calcium fluoride, barium fluoride and silver materials have low shear resistance and are good solid lubricants. SUMMARY

[0004] The single-layer carbide coating has low thermal shock resistance, because the thermal expansion coefficient of the carbide material is low, which increases the thermal expansion mismatch between the ceramic layer and the metal substrate, and in the cold and hot alternating environment of the engine, large residual thermal stress is generated in the coating, and the high-speed friction of the brush wire adversely affects the anti-peeling ability of the coating, in order to improve the thermal shock life of the wear-resistant self-lubricating coating, the application discloses a double-ceramic-layer wear-resistant self-lubricating coating and a preparation method thereof, a metal bonding bottom layer is used to obtain excellent wear-resistant self-lubricating coating bonding strength and thermal shock resistance, calcium fluoride, barium fluoride and silver are added to nickel-chromium / chromium carbide (NiCr / Cr3C2) powder material to form nickel-chromium / chromium carbide + fluoride-containing nickel-chromium / chromium carbide eutectic (NiCr / Cr3C2+NiCr / Cr3C2BaF2·CaF2) coating material and nickel-chromium / chromium carbide (NiCr / Cr3C2-BaF2·CaF2+Ag) coating material containing calcium fluoride, barium fluoride eutectic and silver, the composition transition of the wear-resistant self-lubricating coating is realized, the friction coefficient of the wear-resistant coating is reduced, good lubrication high-temperature characteristics are provided for the friction pair, and the friction performance of the runway wear-resistant coating and the brush wire is significantly improved.

[0005] The technical scheme of the application is:

[0006] A double-ceramic-layer wear-resistant self-lubricating coating, the coating uses a nickel-chromium-aluminum-yttrium-silicon (NiCrAlYSi) sprayed metal substrate as a bonding bottom layer, uses nickel-chromium / chromium carbide + fluoride-containing nickel-chromium / chromium carbide eutectic (NiCr / Cr3C2+NiCr / Cr3C2BaF2·CaF2) as an intermediate layer, and uses nickel-chromium / chromium carbide (NiCr / Cr3C2-BaF2·CaF2+Ag) containing calcium fluoride, barium fluoride eutectic and silver as a surface layer.

[0007] Further, the bonding bottom layer of the double-ceramic-layer wear-resistant self-lubricating coating is made of fine-grained NiCrAlYSi alloy powder, which improves the oxidation and corrosion resistance of the bonding bottom layer, has good wettability with the metal substrate alloy and the carbide coating, enhances the bonding strength between the coating and the substrate and between the coatings, and the particle size of the powder ranges from 20 to 45 microns, and the mass percentage of each element is as follows: Cr: 15% to 25%, Al: 5% to 15%, Y: 0.05% to 2.0%, and Si: 0.1% to 3.0%.

[0008] Further, the double ceramic layer wear-resistant self-lubricating coating has the following advantages: the NiCr in the NiCr / Cr3C2+NiCr / Cr3C2+BaF2·CaF2 powder in the intermediate layer is a high-temperature bonding phase, which provides the coating with necessary mechanical properties, oxidation resistance and corrosion resistance, reduces oxidation and ablation of the core particles in the spraying process, the Cr3C2 is a hard wear-resistant phase, which significantly enhances the strength and wear resistance of the coating, and the BaF2·CaF2 eutectic body is a high-temperature solid lubricating phase, which is used to reduce the friction and wear of the coating and the brush wire, realize good composition transition with the surface layer, reduce the thermal stress between the layers, improve the bonding strength of the coating, the powder particle size is 45 μm to 53 μm, the content ratio of the NiCr / Cr3C2 and the NiCr / Cr3C2+BaF2·CaF2 powder is 1:1, and the mass percentage of each component phase is 65% to 80% of Cr3C2, 20% to 30% of NiCr, and 1% to 5% of CaF2 and BaF2.

[0009] Further, the double ceramic layer wear-resistant self-lubricating coating has the following advantages: the NiCr in the NiCr / Cr3C2+NiCr / Cr3C2+BaF2·CaF2 powder in the intermediate layer is a high-temperature bonding phase, which provides the coating with necessary mechanical properties, oxidation resistance and corrosion resistance, reduces oxidation and ablation of the core particles in the spraying process, the Cr3C2 is a hard wear-resistant phase, which significantly enhances the strength and wear resistance of the coating, and the BaF2·CaF2 eutectic body is a high-temperature solid lubricating phase, which is used to reduce the friction and wear of the coating and the brush wire, realize good composition transition with the surface layer, reduce the thermal stress between the layers, improve the bonding strength of the coating, the powder particle size is 45 μm to 53 μm, the content ratio of the NiCr / Cr3C2 and the NiCr / Cr3C2+BaF2·CaF2 powder is 1:1, and the mass percentage of each component phase is 65% to 80% of Cr3C2, 20% to 30% of NiCr, and 1% to 5% of CaF2 and BaF2.

[0010] Further, the double ceramic layer wear-resistant self-lubricating coating has the following advantages: the NiCr in the NiCr / Cr3C2+NiCr / Cr3C2+BaF2·CaF2 powder in the intermediate layer is a high-temperature bonding phase, which provides the coating with necessary mechanical properties, oxidation resistance and corrosion resistance, reduces oxidation and ablation of the core particles in the spraying process, the Cr3C2 is a hard wear-resistant phase, which significantly enhances the strength and wear resistance of the coating, and the BaF2·CaF2 eutectic body is a high-temperature solid lubricating phase, which is used to reduce the friction and wear of the coating and the brush wire, realize good composition transition with the surface layer, reduce the thermal stress between the layers, improve the bonding strength of the coating, the powder particle size is 45 μm to 53 μm, the content ratio of the NiCr / Cr3C2 and the NiCr / Cr3C2+BaF2·CaF2 powder is 1:1, and the mass percentage of each component phase is 65% to 80% of Cr3C2, 20% to 30% of NiCr, and 1% to 5% of CaF2 and BaF2.

[0011] A preparation method of a double ceramic layer wear-resistant self-lubricating coating, comprising the following steps:

[0012] Step 1) pre-treatment before spraying;

[0013] Step 2) spraying of the bonding bottom layer by using the supersonic flame spraying equipment:

[0014] The JP5000 supersonic flame spraying equipment using oxygen and kerosene as fuel is used, the spraying distance is 330 to 370 mm, the powder feeding rate is 40 to 60 g / min, the oxygen pressure is 200 to 240 psi, the flow rate is 1600 to 1850 SCFH, and the kerosene pressure and flow rate are 210 to 240 psi and 5.5 to 6.5 GPH respectively;

[0015] Step 3) spraying of the intermediate layer and the surface layer by using the supersonic flame spraying equipment:

[0016] The JP5000 supersonic flame spraying equipment using oxygen and kerosene as fuel is used, the spraying distance is 350-400mm, the powder feeding rate is 40g-50g / min, the oxygen pressure is 200-240psi, the flow is 1600-1800SCFH, and the kerosene pressure and flow are 210-240psi and 5.0-5.5GPH respectively.

[0017] Advantages and beneficial effects of the present application:

[0018] 1. The present application uses supersonic flame spraying nickel-chromium-aluminum-yttrium-silicon (NiCrAlYSi) as a metal bonding underlayer on the surface of a metal base to improve the oxidation resistance of the coating system; uses supersonic flame spraying nickel-chromium / chromium carbide + fluorine-containing nickel-chromium / chromium carbide eutectic (NiCr / Cr3C2+NiCr / Cr3C2 BaF2·CaF2) as an intermediate layer to improve the matching with the base and improve the thermal cycle performance of the coating; and finally uses supersonic flame spraying fluorine-containing + silver nickel-chromium / chromium carbide (NiCr / Cr3C2-BaF2·CaF2+Ag) coating to improve the lubrication performance of the coating system, so that the coating system has good friction and wear performance and satisfactory coating thermal cycle performance.

[0019] 2. The bonding strength of the double-ceramic-layer wear-resistant self-lubricating coating of the present application is above 50MPa, higher than the bonding strength of existing wear-resistant self-lubricating coatings; the hardness is above 50 in hardness HV0.3650, and the wear resistance is good; the thermal shock resistance at 700℃ is greater than 100 times, and the thermal shock resistance is excellent; the friction coefficient at 800℃ is 0.26, and the tribological performance is significantly improved.

[0020] 3. The double-ceramic-layer wear-resistant self-lubricating coating of the present application uses a bonding underlayer + double-layer carbide ceramic layer structure system to improve the matching between the coating and the base and between the coatings, improve the thermal cycle performance of the coating, reduce the peeling of the coating during use, has satisfactory bonding strength and peeling resistance, maximally prolongs the service life in the high-speed friction and wear environment of the runway and the brush wire, avoids failures and scrapping caused by peeling of the coating on the runway surface or melting, deformation and breaking of the brush wire, and improves the sealing effect of the sealing system as a whole. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Friction coefficient curve of the NiCr / Cr3C2-BaF2·CaF2+Ag coating at different temperatures. DETAILED DESCRIPTION

[0022] The present application will be further described in detail below in combination with the drawings and specific embodiments of the present application.

[0023] The invention is spraying test of double ceramic layer wear-resistant self-lubricating coating on the runway of brush seal system of engine.

[0024] The process flow is as follows:

[0025] Part inspection→acetone oil removal→appearance inspection→sand blasting protection→dry sand blasting→cleaning→spraying protection→clamping→→ultrasonic flame spraying adhesive bottom layer→ultrasonic flame spraying middle layer→ultrasonic flame spraying surface layer→appearance inspection.

[0026] The dry sand blasting treatment before spraying is to clean, roughen and activate the surface of the runway base alloy, and improve the bonding strength between the adhesive layer and the alloy base.

[0027] The process parameters for spraying the adhesive bottom layer are as follows: using JP5000 ultrasonic flame spraying equipment with oxygen and kerosene as fuel, spraying distance is 350mm, powder feeding rate is 50g / min, oxygen pressure is 220psi, flow is 1800SCFH, kerosene pressure and flow are 230psi and 6.1GPH respectively;

[0028] The process parameters for spraying the middle layer and the surface layer are as follows: using JP5000 ultrasonic flame spraying equipment with oxygen and kerosene as fuel, spraying distance is 350mm, powder feeding rate is 40g / min, oxygen pressure is 220psi, flow is 1700SCFH, kerosene pressure and flow are 230psi and 5.5GPH respectively.

[0029] Selection of raw materials:

[0030] The NiCrAlYSi alloy powder for the adhesive bottom layer has a powder particle size of 45μm, and the mass percentage of each element is as follows: Cr: 20%, Al: 10%, Y: 1%, Si: 2%, and the balance is nickel;

[0031] The powder particle size of the middle layer NiCr / Cr3C2+NiCr / Cr3C2BaF2·CaF2 is 53μm, the mass percentage of NiCr / Cr3C2 and NiCr / Cr3C2BaF2·CaF2 powder is 1:1, Cr3C2 accounts for 75%, NiCr accounts for 20%, and CaF2 and BaF2 account for 5%;

[0032] The powder particle size of the surface layer NiCr / Cr3C2-BaF2·CaF2+Ag is 45μm, the particle density of each component powder is the same, and the thermal physical parameters are the same, Cr3C2 accounts for 60%, NiCr accounts for 25%, CaF2 and BaF2 account for 10%, and Ag accounts for 5%.

[0033] The adhesive layer thickness of the obtained double ceramic layer wear-resistant self-lubricating coating is 80μm, the middle layer thickness is 100μm, and the surface layer thickness is 110μm.

[0034] The average bond strength test result of the wear-resistant self-lubricating coating was 62 MPa. The fracture mainly occurred in the fluorinated calcium eutectic, barium fluoride eutectic and silver nickel-chromium / chromium carbide coatings near the interface of the intermediate layer / top layer.

[0035] Thermal shock tests were conducted on the thermal barrier coating at 800℃ using forced air cooling. After 100 cycles of thermal shock testing, observation of the coating surface and cross-sectional morphology revealed no peeling or cracking at the coating interface. The test results indicate that the double-layer ceramic structure wear-resistant self-lubricating coating exhibits excellent thermal shock resistance.

[0036] like Figure 1 The figure shows the friction coefficient curves of the NiCr / Cr3C2-BaF2·CaF2+Ag coating at different temperatures. It can be seen from the figure that the friction coefficient of the coating fluctuates greatly at room temperature. As the temperature increases, the friction coefficient of the coating becomes more stable, the fluctuation decreases, and the friction coefficient curve becomes smoother. This indicates that the higher the temperature, the lower the friction coefficient of the coating containing eutectic fluoride and silver solid lubricant. Under the high-temperature operating environment of the engine, the coating can better exert its wear resistance and lubrication performance.

Claims

1. A dual ceramic layer wear resistant self-lubricating coating, characterized in that, The coating is a metal base sprayed with nickel-chromium-aluminum-yttrium-silicon NiCrAlYSi as a bonding base layer, nickel-chromium / chromium carbide + fluorine-containing nickel-chromium / chromium carbide eutectic NiCr / Cr3C2+NiCr / Cr3C2BaF2•CaF2 as an intermediate layer, and nickel-chromium / chromium carbide NiCr / Cr3C2-BaF2•CaF2+Ag containing fluorine-containing calcium fluoride, barium fluoride eutectic and silver as a surface layer. The surface layer material has BaF2•CaF2 eutectic, Ag, and Cr3C2 as a core, a NiCr alloy cladding layer as a shell, and a powder particle size range of 20-53 μm. The component powders have the same particle density, thermal conductivity, temperature coefficient, and specific heat capacity. The mass percentage of each component phase is 58-68% of Cr3C2, 22-30% of NiCr, 1-10% of CaF2 and BaF2, and 1-10% of Ag. The thickness of the bonding base layer is 80-120 mm, and the thickness of the intermediate layer and the surface layer is 100-120 mm.

2. A dual ceramic layer wear resistant self-lubricating coating according to claim 1, characterized in that, The NiCrAlYSi alloy powder of the bonding base layer has a powder particle size range of 20-45 μm, and the mass percentage of each element is 15-25% of Cr, 5-15% of Al, 0.05-2.0% of Y, and 0.1-3.0% of Si.

3. The dual ceramic layer wear resistant self-lubricating coating of claim 1, wherein, The intermediate layer NiCr / Cr3C2+NiCr / Cr3C2BaF2•CaF2 powder has a particle size range of 45-53 μm, and the content ratio of NiCr / Cr3C2 and NiCr / Cr3C2BaF2•CaF2 powder is 1:

1. The mass percentage of each component phase is 65-80% of Cr3C2, 20-30% of NiCr, and 1-5% of CaF2 and BaF2.

4. A method of producing the dual ceramic layer wear resistant self-lubricating coating of claim 1, characterized in that, The method comprises the following steps: Step 1) pre-treatment before spraying; Step 2) ultrasonic flame spraying of the bonding base layer: JP5000 ultrasonic flame spraying equipment using oxygen and kerosene as fuel is used, the spraying distance is 330-370 mm, the powder feeding rate is 40-60 g / min, the oxygen pressure is 200-240 psi, the flow rate is 1600-1850 SCFH, the kerosene pressure and flow rate are 210-240 psi and 5.5-6.5 GPH, respectively; Step 3) ultrasonic flame spraying of the intermediate layer and the surface layer: JP5000 ultrasonic flame spraying equipment using oxygen and kerosene as fuel is used, the spraying distance is 350-400 mm, the powder feeding rate is 40-50 g / min, the oxygen pressure is 200-240 psi, the flow rate is 1600-1800 SCFH, the kerosene pressure and flow rate are 210-240 psi and 5.0-5.5 GPH, respectively.

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