CN104018110B - A kind of preparation method of ferrite conductivity ceramics coating - Google Patents

Abstract

The invention discloses a preparation method of a ferrite conductive ceramic coating, which belongs to the field of surface engineering. The ferrite conductive ceramic coating is a composite coating consisting of a bonding layer and a ceramic layer, the bonding layer is a metal material or an alloy material, and the ceramic layer is a ferrite ceramic material with a molecular formula of MeFe ₂ O ₄ . Firstly, the bonding layer powder is sprayed on the surface of the metal substrate by a plasma spraying process to form a bonding layer; then the ferrite ceramic powder is sprayed on the surface of the bonding layer by supersonic flame spraying to form a ceramic layer. The ferrite conductive ceramic coating has good bonding strength, corrosion resistance and electrical conductivity; the preparation method is simple in process and convenient in operation, and can be applied to the surface of metal substrates of different shapes or sizes, especially in the preparation of large The corrosion-resistant conductive ceramic coating for practical application highlights its superiority.

Description

A kind of preparation method of ferrite conductive ceramic coating

technical field

The invention relates to a preparation method of a ferrite conductive ceramic coating, which belongs to the field of surface engineering.

Background technique

The grounding grid is a necessary facility to ensure working grounding, lightning protection grounding, and protective grounding in power plants, substations, and communication stations. Because the soil has a certain corrosion effect, the ground electrode material is often corroded due to improper protection. With the rapid development of ultra-high voltage DC transmission technology, conventional ground electrode materials such as carbon steel and high-chromium cast iron have certain defects. Carbon steel corrodes too quickly, and the corrosion rate of high-chromium cast iron increases sharply under high overflow density, etc. The shortcomings will become more prominent, directly threatening the operation safety and reliability of DC transmission projects. It is difficult and expensive to excavate and maintain the DC ground electrode, which puts forward higher requirements on the conductivity and anti-corrosion performance of the ground electrode material.

The ferrite material has a spinel structure, and its corrosion resistance is better than that of high-chromium cast iron electrodes. Some ferrite materials have high electrical conductivity, and the main component is Fe ₂ O ₃ . It produces secondary pollution and endangers the environment. It is a new generation of environmentally friendly and anti-corrosion electrode materials. At present, the methods for preparing ferrite ground electrode products are mainly sintering method and casting method. The sintering method has a simple process, but the production cycle is long, and problems such as incomplete reaction are likely to exist. When preparing large-scale products, the green body is prone to cracking or deformation during the drying and sintering process, so it is difficult to realize the preparation of large-scale products; the casting method has The advantages of low production cost and short cycle are suitable for the preparation of electrode products with simple shapes and large volumes. However, due to the great difference in properties between metal oxides and simple metal powders, and the castability of ferrite materials Very poor, special casting technology and strict atmosphere control process are required, which reduces the practicability and operability of this preparation method. Thermal spraying technology provides a new idea for the preparation of ferrite. Coating ferrite coating on the surface of conventional carbon steel grounding electrodes, with the help of coating protection technology, can improve the corrosion resistance of the grounding electrode body under the premise of ensuring good electrical conductivity, which has a good development prospect. The US patent US3850701 applied by Yitai and others pointed out that the maximum thickness of the ferrite coating deposited by chemical method is only 0.02mm, which cannot meet the service life requirements of the ground electrode body, and has not prepared a practical ferrite conductive coating. ceramic coating.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a ferrite conductive ceramic coating. First, the bonding layer powder is sprayed onto the surface of the metal substrate by a plasma spraying process to form a bonding layer; Bulk ceramic powder is sprayed onto the surface of the bonding layer to form a ceramic layer; the bonding layer and the ceramic layer together constitute the ferrite conductive ceramic coating of the present invention. The preparation method has simple process and convenient operation, and can be applied to the surface of metal substrates of different shapes or sizes, especially in the preparation of large-area corrosion-resistant conductive ceramic coatings for practical application.

The purpose of the present invention is achieved by the following technical solutions:

A kind of preparation method of ferrite conductive ceramic coating of the present invention, described method step is as follows:

(1) Clean and sandblast the surface of the metal substrate to be sprayed;

(2) Drying the bonding layer powder and the ferrite ceramic powder respectively, and loading the dried two powders into powder feeders respectively, wherein the drying temperature is 80-200° C.;

(3) Fix the metal substrate to be sprayed on the workbench of the plasma spraying equipment, and use compressed air to further clean the surface of the metal substrate to be sprayed;

(4) After preheating the surface of the metal substrate to be sprayed, use a plasma spray gun to evenly spray the bonding layer powder onto the surface of the metal substrate to be sprayed to form a bonding layer. The thickness of the bonding layer is 0.1 to 0.2mm;

(5) Use a supersonic flame spray gun to evenly spray ferrite ceramic powder onto the surface of the bonding layer to form a ceramic layer with a thickness of 0.1-0.3 mm;

Wherein, in the spraying process described in step (4) and step (5), the internal powder feeding method is used to feed powder, and compressed air is used to cool the surface of the metal substrate to be sprayed; the plasma spraying process parameters are shown in Table 1, and the supersonic flame spraying process parameters See Table 2;

Table 1

The bonding layer and the ceramic layer jointly constitute the ferrite conductive ceramic coating of the present invention, the bonding layer is a metal material or an alloy material, and the ceramic layer is a ferrite ceramic with a molecular formula of MeFe ₂ O ₄ Material;

Wherein, the bonding layer of the present invention is preferably one of Al, Zn, Co and Cu or one of Al-based alloys, Zn-based alloys, Co-based alloys, Cu-based alloys and Ni-based alloys; the MeFe ₂ Me in O ₄ is preferably one of Mn ²⁺ , Zn ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Co ²⁺ and Li ⁺ _0.5 Fe ³⁺ _0.5 ;

Step (1) preferably uses analytically pure acetone to clean the surface of the metal substrate to be sprayed to remove impurities such as dust and oil stains attached to the surface of the metal substrate to be sprayed; use 30 to 80 mesh white jade steel grit for sandblasting;

The bonding layer powder and ferrite ceramic powder in step (2) preferably have a particle size range of 20-100 μm, good particle sphericity, and good fluidity; the powder feeder is preferably a scraper type powder feeder;

The main gas and the carrier gas of the plasma spraying described in step (4) are Ar gas, and the auxiliary gas is He gas;

The carrier gas of the supersonic flame spraying in step (5) is Ar gas, and the fuel is preferably aviation kerosene.

Beneficial effect

(1) The ferrite conductive ceramic coating of the present invention is a composite coating, which includes a bonding layer coated on the metal substrate surface and a ceramic layer coated on the bonding layer, the bonding layer The citation improves the bonding strength between the ceramic layer and the metal matrix while maintaining the electrical conductivity of the metal matrix; the ferrite ceramic layer has good corrosion resistance and electrical conductivity.

(2) The ceramic layer of the present invention selects a ferrite ceramic material with a low melting point, corrosion resistance, good electrical conductivity and strong spraying adaptability, so that the ferrite conductive ceramic coating can be used in power plants and substations Metal structures with corrosion phenomena in facilities such as communication stations and communication stations have a wide range of applications.

(3) The preparation method of a ferrite conductive ceramic coating according to the present invention first sprays the bonding layer powder onto the surface of the metal substrate through a plasma spraying process to form a bonding layer, and the bonding layer not only ensures the coating The conductive properties of the layer, and improve the bonding strength of the coating.

(4) the preparation method of a kind of ferrite conductive ceramic coating of the present invention, ferrite ceramic powder is sprayed on the surface of described adhesive layer by supersonic flame spraying, forms ceramic layer, and described ceramic coating has Good corrosion resistance and electrical conductivity;

(5) The bonding layer and the ceramic layer together constitute a ferrite conductive ceramic coating, the bonding strength of the coating reaches 15.2MPa-50MPa, the porosity of the coating is ≤13.0%, and the resistivity of the coating at room temperature is ≤5.9×10 ^{− 2} Ω·cm.

(6) The preparation method has the advantages of simple process, low cost and strong repeatability. It can be applied to the surface of metal substrates of different shapes or sizes, especially in the preparation of large-area corrosion-resistant conductive ceramic coatings for practical applications. At the same time, the maintenance of the workpiece is simple during service, and it is suitable for industrial promotion.

Description of drawings

Fig. 1 is the scanning electron microscope figure of ferrite conductive ceramic coating section in embodiment 1;

Fig. 2 is the scanning electron microscope figure of ferrite conductive ceramic coating section in embodiment 2;

Fig. 3 is the scanning electron microscope figure of ferrite conductive ceramic coating section in embodiment 3;

Fig. 4 is a schematic diagram of measuring the resistance of ferrite conductive ceramic coating by two-terminal method.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, but is not limited thereto.

The plasma spray equipment used in the following examples is the 5500 type plasma spray system produced by U.S. Praxair, and the spray gun is SG100; the supersonic flame spray equipment used is the FP73 supersonic flame spray produced by U.S. Praxair-TAFA System; the manufacturer of CO-211 nickel-based alloy powder and CO-210 nickel-based alloy powder is Praxair Corporation of the United States.

The ferrite conductive ceramic coating prepared in the following examples is tested as follows:

(1) Morphology observation and porosity measurement of ferrite conductive ceramic coating

Utilize light microscope and S-4800 type cold field emission scanning electron microscope of Japan High-Tech Co., Ltd. to observe the morphology of the ferrite conductive ceramic coating; adopt IA32 image analysis software to calculate the average value of the porosity of the ferrite conductive ceramic coating ;

(2) Measurement of bonding strength of ferrite conductive ceramic coating

The bonding strength of the ferrite conductive ceramic coating and the metal substrate is measured on a universal testing machine by the bonding tensile method, and the tensile speed is 1mm/min;

(3) Measurement of resistivity of ferrite conductive ceramic coating

The resistance of the ferrite conductive ceramic coating is tested by the two-terminal method and the resistivity is calculated. In order to reduce the contact resistance between the ferrite conductive ceramic coating and the ohmmeter and reduce the measurement error, a certain area of conductive adhesive is used to attach the test Like, as shown in Figure 4. Use the positive and negative test leads of the ohmmeter to touch the conductive adhesive and the unpainted surface of the metal substrate respectively, and the measured resistance value is approximately the resistance of the ferrite conductive ceramic coating under the conductive adhesive coating.

According to the resistivity calculation formula (formula 1), the resistivity of the ferrite conductive coating at room temperature can be calculated.

$\mathrm{<span\; class="notranslate">\; \&rho;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; S</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula: ρ is the resistivity of the ferrite conductive ceramic coating;

S is the area of the conductive adhesive;

h is the thickness of the ferrite conductive ceramic coating;

R is the resistance of the ferrite conductive ceramic coating under the conductive adhesive cover.

Example 1

(1) Clean the surface of the LY12 hard steel plate to be sprayed with analytically pure acetone, and use 30-80 mesh white corundum sand for sandblasting;

(2) Select CO-211 nickel-based alloy powder with a particle size range of 20-100 μm as the bonding layer powder and Li _0.5 Fe _2.5 O ₄ powder as the ferrite ceramic powder, and dry the two powders at 100 ° C process, and put the two dried powders into the powder feeder respectively;

(3) Fix the LY12 hard steel plate to be sprayed on the workbench of the plasma spraying equipment, and use compressed air to further clean the surface of the LY12 hard steel plate to be sprayed;

(4) Set the spraying walking route program for the manipulator with the spray gun installed;

(5) Set the plasma spraying process parameters. After preheating the surface of the LY12 hard steel plate to be sprayed, use a plasma spray gun to spray the bonding layer powder onto the surface of the LY12 hard steel plate to be sprayed to form a bonding layer. The thickness of the bonding layer is 0.1mm , where the spraying parameters are current 600A, main gas 3m ³ h ^-1 , auxiliary gas 1m ³ h ^-1 , powder feeding volume 25gmin ^-1 , carrier gas 0.2m ³ h ^-1 , spraying distance 100mm; both main gas and carrier gas It is Ar gas, and the auxiliary gas is He gas;

(6) Set the supersonic flame spraying process parameters. The ferrite ceramic powder is sprayed onto the surface of the bonding layer by a supersonic flame spray gun to form a ceramic layer. The thickness of the ceramic layer is 0.2mm. The spraying parameters are fuel 20Lh ^-1 , oxygen 1500SCFH, powder feeding volume 18gmin ^-1 , carrier gas 10SCFH, spraying distance 350mm; carrier gas is Ar gas, fuel is aviation kerosene.

The ferrite conductive ceramic coating prepared in this embodiment is tested as follows, and the results are as follows:

(1) Morphology observation and porosity measurement of ferrite conductive ceramic coating:

The cross-sectional morphology of the ferrite conductive ceramic coating is as shown in Figure 1, as can be seen from Figure 1, the structure of the ferrite conductive ceramic coating is uniform and compact, and the average porosity of the coating is calculated with the IA32 image analysis software. The value is 2.4%.

(2) Measurement of bonding strength of ferrite conductive ceramic coating:

The bonding strength between the ferrite conductive ceramic coating and the LY12 hard steel plate measured by the bonding tensile method is 29.8 MPa.

(3) Measurement of resistivity of ferrite conductive ceramic coating

The measured resistance of the ferrite conductive ceramic coating is 3.31Ω, and the relevant parameters S=6.4×10 ^-1 cm ² , h=1.8×10 ^-2 cm are substituted into formula (1), and the ferrite The room temperature resistivity of the conductive ceramic coating is 1.18×10 ^-2 Ω·cm.

Example 2

(1) Clean the surface of the LY12 hard steel plate to be sprayed with analytically pure acetone, and use 30-80 mesh white corundum sand for sandblasting;

(2) Select CO-210 nickel-based alloy powder with a particle size range of 20-100 μm as the bonding layer powder and NiFe ₂ O ₄ powder as the ferrite ceramic powder, and dry the two powders at 80 ° C, respectively. And put the dried two powders into the powder feeder respectively;

(3) Fix the LY12 hard steel plate to be sprayed on the workbench of the plasma spraying equipment, and use compressed air to further clean the surface of the LY12 hard steel plate to be sprayed;

(4) Set the spraying walking route program for the manipulator with the spray gun installed;

(5) Set the plasma spraying process parameters. After preheating the surface of the LY12 hard steel plate to be sprayed, use a plasma spray gun to spray the bonding layer powder onto the surface of the LY12 hard steel plate to be sprayed to form a bonding layer. The thickness of the bonding layer is 0.15mm , where the spraying parameters are current 550A, main gas 1m ³ h ^-1 , auxiliary gas 2m ³ h ^-1 , powder feeding volume 10gmin ^-1 , carrier gas 0.6m ³ h ^-1 , spraying distance 70mm; both main gas and carrier gas It is Ar gas, and the auxiliary gas is He gas;

(6) Set the supersonic flame spraying process parameters. The ferrite ceramic powder is sprayed to the surface of the bonding layer by a supersonic flame spray gun to form a ceramic layer. The thickness of the ceramic layer is 0.1mm. The spraying parameters are fuel 25Lh ^-1 , oxygen 2000SCFH, powder delivery rate 6gmin ^-1 , carrier gas 6SCFH, spraying distance 400mm; carrier gas is Ar gas, fuel is aviation kerosene.

The ferrite conductive ceramic coating prepared in this embodiment is tested as follows, and the results are as follows:

(1) Morphology observation and porosity measurement of ferrite conductive ceramic coating:

The cross-sectional morphology of the ferrite conductive ceramic coating is as shown in Figure 2, as can be seen from Figure 2, the structure of the ferrite conductive ceramic coating is uniform and compact, and the average porosity of the coating is calculated with the IA32 image analysis software. The value is 2.1%.

(2) Measurement of bonding strength of ferrite conductive ceramic coating:

The bonding strength of the ferrite conductive ceramic coating measured by the bonding tensile method is 31.5 MPa.

(3) Measurement of resistivity of ferrite conductive ceramic coating

The measured resistance of the ferrite conductive ceramic coating is 2.58Ω, and the related parameters S=6.4×10 ^-1 cm ² , h=1.8×10 ^-2 cm are substituted into formula (1), and the ferrite The room temperature resistivity of the conductive ceramic coating is 9.17×10 ^-3 Ω·cm.

Example 3

(1) Clean the surface of the LY12 hard steel plate to be sprayed with analytically pure acetone, and use 30-80 mesh white corundum sand for sandblasting;

(2) Select CO-210 nickel-based alloy powder with a particle size range of 20-100 μm as the bonding layer powder and ZnFe ₂ O ₄ powder as the ferrite ceramic powder, and dry the two powders at 200 ° C, respectively. And put the dried two powders into the powder feeder respectively;

(3) Fix the LY12 hard steel plate to be sprayed on the workbench of the plasma spraying equipment, and use compressed air to further clean the surface of the LY12 hard steel plate to be sprayed;

(4) Set the spraying walking route program for the manipulator with the spray gun installed;

(5) Set the plasma spraying process parameters. After preheating the surface of the LY12 hard steel plate to be sprayed, use a plasma spray gun to spray the bonding layer powder onto the surface of the LY12 hard steel plate to be sprayed to form a bonding layer. The thickness of the bonding layer is 0.2mm , where the spraying parameters are current 650A, main gas 2m ³ h ^-1 , auxiliary gas 1.5m ³ h ^-1 , powder feeding volume 40gmin ^-1 , carrier gas 1m ³ h ^-1 , spraying distance 120mm; both main gas and carrier gas It is Ar gas, and the auxiliary gas is He gas;

(6) Set the supersonic flame spraying process parameters. The ferrite ceramic powder is sprayed onto the surface of the bonding layer by a supersonic flame spray gun to form a ceramic layer. The thickness of the ceramic layer is 0.3mm. The spraying parameters are fuel 30Lh ^-1 , oxygen 2500SCFH, powder feeding volume 30gmin ^-1 , carrier gas 14SCFH, spraying distance 450mm, carrier gas is Ar gas, fuel is aviation kerosene.

The ferrite conductive ceramic coating prepared in this embodiment is tested as follows, and the results are as follows:

(1) Morphology observation and porosity measurement of ferrite conductive ceramic coating:

The cross-sectional morphology of the ferrite conductive ceramic coating is as shown in Figure 3, as can be seen from Figure 3, the structure of the ferrite conductive ceramic coating is uniform and compact, and the average porosity of the coating is calculated with the IA32 image analysis software. The value is 1.9%.

(2) Measurement of bonding strength of ferrite conductive ceramic coating:

The bonding strength of the ferrite conductive ceramic coating and the LY12 hard steel plate is 36.5 MPa as measured by the bonding tensile method.

(3) Measurement of resistivity of ferrite conductive ceramic coating

The measured resistance of the ferrite conductive ceramic coating is 2.11Ω, and the relevant parameters S=6.4×10 ^-1 cm ² , h=1.8×10 ^-2 cm are substituted into the formula (1) to calculate the ferrite The room temperature resistivity of the conductive ceramic coating is 7.5×10 ^-3 Ω·cm.

The present invention includes but is not limited to the above embodiments, and any equivalent replacement or partial improvement under the principle of the spirit of the present invention will be considered within the protection scope of the present invention.

Claims (6)

1. a preparation method of ferrite conductive ceramic coating, is characterized in that: described method step is as follows: (1) Clean and sandblast the surface of the metal substrate to be sprayed; (2) Dry the bonding layer powder and ferrite ceramic powder respectively, and put the dried two powders into the powder feeder respectively, wherein the drying temperature is 80-200°C, and the iron Oxygen ceramic powder particle size ranges from 20 to 100 μm; (3) Fix the metal substrate to be sprayed on the workbench of the plasma spraying equipment, and use compressed air to further clean the surface of the metal substrate to be sprayed; (4) After preheating the surface of the metal substrate to be sprayed, use a plasma spray gun to evenly spray the bonding layer powder onto the surface of the metal substrate to be sprayed to form a bonding layer. The thickness of the bonding layer is 0.1 to 0.2mm; (5) Spray ferrite ceramic powder evenly onto the surface of the bonding layer with a supersonic flame spray gun to form a ceramic layer with a thickness of 0.1-0.3mm; Wherein, in the spraying process described in step (4) and step (5), the internal powder feeding method is used to feed powder, and compressed air is used to cool the surface of the metal substrate to be sprayed; the plasma spraying process parameters are shown in Table 1, and the supersonic flame spraying process parameters See Table 2; Table 1 Table 2 The bonding layer and the ceramic layer jointly constitute the ferrite conductive ceramic coating, the bonding layer is a metal material, and the ceramic layer is a ferrite ceramic material with a molecular formula of MeFe ₂ O ₄ , wherein Me It is one of Mn ²⁺ , Zn ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Co ²⁺ and Li ⁺ _0.5 Fe ³⁺ _0.5 . 2. the preparation method of a kind of ferrite conductive ceramic coating according to claim 1, is characterized in that: described bonding layer material is a kind of or Al base alloy in Al, Zn, Co and Cu, Zn One of Co-based alloys, Co-based alloys, Cu-based alloys and Ni-based alloys. 3. the preparation method of a kind of ferrite conductive ceramic coating according to claim 1 is characterized in that: step (1) adopts analytically pure acetone to clean the surface of the metal substrate to be sprayed; adopt 30～80 purpose white corundum Sand for sandblasting. 4. The preparation method of a ferrite conductive ceramic coating according to claim 1, characterized in that: the particle size range of the bonding layer powder in step (2) is 20-100 μm; the powder feeder is a scraper type powder feeder. 5. the preparation method of a kind of ferrite conductive ceramic coating according to claim 1 is characterized in that: the main gas and carrier gas of step (4) described plasma spraying are Ar gas, and auxiliary gas is He gas . 6. the preparation method of a kind of ferrite conductive ceramic coating according to claim 1 is characterized in that: the carrier gas of step (5) described supersonic flame spraying is Ar gas, and fuel is aviation kerosene.