A functional coating for the inner wall of a metal crucible and a method for producing it

Abstract

The present application relates to a kind of metal smelting furnace inner wall functional coating and its preparation method, belong to functional coating preparation technical field.The double-layer structure of including outer ceramic coating and inner metal connecting layer, the diffusion effect between smelting furnace and metal melt in smelting process can be isolated by outer ceramic coating, the metal connecting layer in inner layer is used to enhance the binding force between ceramic coating and metal smelting furnace inner wall, to prolong the service life of coating.The preparation process of coating includes: after the treatment to metal smelting furnace inner wall, using plasma spraying process is sprayed Cr 20 Ni 80 Alloy connecting layer is sprayed on the surface of connecting layer, ceramic coating is sprayed.The present application is prepared by plasma spraying process, can be automated production, can greatly improve the quality of smelted metal liquid, reduce the unqualified rate of product, ceramic coating can improve the hardness and wear resistance of metal smelting furnace inner surface, can eliminate the phenomenon of sticking material, promote the service life of smelting furnace.

Description

Technical Field

[0001] This invention relates to the field of functional coating preparation technology, specifically to a functional coating for the inner wall of a metal crucible and its preparation method. Background Technology

[0002] In the metal smelting process, common problems include burn-off due to the interaction between the molten metal and the inner wall of the crucible, diffusion of metallic elements from the inner wall into the molten metal introducing impurities, and contamination of the molten metal due to the peeling off of the coating on the inner wall of the crucible. Taking the smelting process of magnesium alloys as an example, current industrial production mainly uses cast iron crucibles, which easily leads to excessive Fe content in the ingots. Furthermore, coatings need to be applied to the inner wall of the crucible before smelting, extending the production cycle. During the smelting process, the coatings are prone to peeling off, introducing impurities into the melt and increasing the scrap rate.

[0003] Oxide ceramics possess high melting points, outstanding mechanical properties, and high-temperature chemical stability, making them suitable for enhancing the strength, hardness, wear resistance, or biological properties of matrix materials. Therefore, they are commonly used as coating materials. ZrO2-toughened Al2O3 (ZTA) ceramics exhibit high temperature resistance, high strength, high fracture toughness, wear resistance, and resistance to acid and alkali corrosion, finding wide application in industries such as machinery, electronics, petroleum, chemical, aerospace, and textiles. Dy2O3 ceramics exhibit excellent chemical compatibility with ZTA. Adding Dy2O3 to oxide ceramic coatings increases the coating's thermal stability, refines the coating's grain structure, and acts as a solid lubricant between contact surfaces, reducing the coefficient of friction and mitigating wear on composite coatings. Adding Er2O3 to oxide ceramic coatings improves the coating's thermal conductivity, increases its toughness, and reduces its porosity.

[0004] Plasma spraying has obvious advantages and prominent features: (1) Wide range of materials and applications. With its unique heat source system, plasma spraying can heat and ionize almost all existing materials, so the coating materials are no longer limited. This characteristic is unmatched by other thermal spraying methods; (2) High degree of production automation. Plasma spraying has an absolute advantage in process control and coating optimization. The coating thickness can be designed according to the conditions and requirements, and high-performance coatings that meet the preset requirements can be sprayed in a directional and fixed-point manner; (3) Good coating quality. Because the plasma spraying arc heating system can fully melt or highly plasticize the material during the coating material processing stage, the material sprayed onto the workpiece surface is a material with uniform dispersion, resulting in better coating bonding and higher performance. Summary of the Invention

[0005] To address the problems encountered by metal crucibles during the smelting process, this invention provides a functional coating for the inner wall of a metal crucible and its preparation method.

[0006] To achieve the above technical objectives, the technical solution adopted in this application is as follows:

[0007] This invention provides a functional coating for the inner wall of a metal crucible, the coating being a double-layer coating comprising an inner metal bonding layer and an outer ceramic coating;

[0008] The outer ceramic material of the double-layer coating is composed of zirconia-toughened alumina ceramic (ZTA), Dy2O3, Er2O3, and ZrO2; the inner material of the double-layer coating is composed of Cr. 20 Ni 80 .

[0009] Furthermore, the outer ceramic raw material of the double-layer coating is composed of the following mass percentages: ZTA 41-49%, Dy2O3 13-15%, Er2O3 20-24%, and ZrO2 18-20%.

[0010] This invention provides a method for preparing a functional coating on the inner wall of a metal crucible, comprising the following steps:

[0011] (1) Pre-treat the inner wall of the metal crucible;

[0012] (2) The selected spraying powder is Cr 20 Ni 80 The alloy powder is plasma-sprayed onto the inner wall of the treated crucible to form the metal bonding layer.

[0013] (3) Select a spraying powder with the following composition by mass percentage: Dy2O3 13-15%, Er2O3 20-24%, ZrO2 18-20%, and the balance is zirconia toughened alumina ceramic (ZTA). Perform plasma spraying on the surface of the metal connection layer to form the ceramic coating.

[0014] Furthermore, the pretreatment step described in step (1) includes cleaning the inner wall of the metal crucible and roughening its surface.

[0015] Furthermore, in step (1), the inner wall cleaning is performed by using acetone or alcohol to clean the oil stains on the inner surface of the metal crucible, and the surface roughening treatment is to perform sandblasting on the inner surface of the crucible.

[0016] Furthermore, the surface sandblasting treatment in step (1) is carried out by sandblasting with white corundum with a particle size of 250-300μm and a sandblasting pressure of 0.5-0.8MPa.

[0017] Furthermore, the process parameters of the plasma spraying and powder feeding device described in steps (2) and (3) are as follows: the plasma gas is Ar gas, and the powder feeding gas flow rate is 6-9 L•min. -1The arc power is 13-16KW, the spraying distance is 150-200mm, and the particle size of the spraying powder is 20-40μm.

[0018] The principle of this invention is to prepare a functional coating on the surface of a metal crucible using plasma spraying technology. The coating consists of an outer ceramic coating and an inner metal bonding layer. The outer ceramic coating uses ZTA ceramic as the base. Adding Dy2O3 increases the thermal stability of the coating, reduces the coefficient of friction on the ceramic coating surface, and alleviates the wear of the composite coating. During the spraying process, it can react with Ni in the bonding layer to form a metallurgical bond. Adding Er2O3 reduces the porosity of the coating, making it denser and thus extending its service life. Adding ZrO2 can react with Er2O3 to form a tetragonal phase, which can improve the thermal conductivity of the ceramic coating. During the melting process, it reduces the temperature gradient between the coating surface and the metal crucible, thereby extending the service life of the coating and playing a role in isolating mass transfer. This greatly improves the quality of the molten metal, reduces the product defect rate, increases the hardness and wear resistance of the inner surface of the metal crucible, eliminates material sticking, and extends the service life of the crucible. The inner metal bonding layer can form a metallurgical bond with the inner wall of the crucible and the ceramic coating, thereby improving the service life of the coating.

[0019] The plasma spraying process uses plasma spraying equipment and a synchronous automatic powder feeding device. The plasma arc driven by DC electricity is used as a heat source to heat the prepared powder material to a molten or semi-molten state and spray it at high speed onto the surface of the pretreated workpiece, thereby forming a strong coating on the inner wall of the crucible, so that the inner wall of the metal crucible has the function of isolating mass transfer.

[0020] The present invention has a simple process, long product life and excellent performance. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the coating structure described in this invention;

[0022] Figure 2 The hardness of the coating in the embodiments of the present invention;

[0023] Figure 3 This refers to the wear volume loss of the coating in the embodiments of the present invention;

[0024] Figure 4 The value represents the thermal conductivity of the coating at 600°C in the embodiments of this invention. Detailed Implementation

[0025] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0026] The following will further explain and illustrate the implementation scheme of the present invention with reference to specific embodiments. It should be understood that the specific embodiments herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] The technical solution of the present invention will be further illustrated below with reference to examples. Taking cast iron crucibles as an example, cast iron crucibles are commonly used metal crucibles in magnesium alloy smelting. Figure 1 This is a schematic diagram of the coating structure described in an embodiment of the present invention.

[0028] Example 1

[0029] This embodiment describes a functional coating for the inner wall of a metal crucible. The coating is a double-layer coating, comprising an inner metal bonding layer and an outer ceramic coating. The outer ceramic raw material of the double-layer coating has the following composition by mass percentage: 49% ZrO2, 13% Dy2O3, 20% Er2O3, and 18% ZrO2. The inner raw material composition is Cr... 20 Ni 80 .

[0030] This embodiment describes a method for preparing a functional coating on the inner wall of a metal crucible, comprising the following steps:

[0031] (1) Clean and roughen the inner wall of the metal crucible. Acetone was used to clean the inner wall of the cast iron crucible, and 250μm white corundum was used for sandblasting at a pressure of 0.6MPa.

[0032] (2) The selected spraying powder is Cr 20 Ni 80 The alloy powder is used to plasma spray the inner wall of the treated crucible to form a metal bonding layer.

[0033] (3) Select a spraying powder with the following composition by mass percentage: 49% ZTA, 13% Dy2O3, 20% Er2O3 and 18% ZrO2, and perform plasma spraying on the surface of the metal connection layer to form the ceramic coating.

[0034] The process parameters of the plasma spraying process and powder feeding device in steps (2) and (3) are as follows: the plasma gas is Ar gas, the powder feeding gas flow rate is 6L•min-1, the arc power is 13KW, the spraying distance is 150mm, and the selected spraying powder particle size is 20μm.

[0035] Example 2

[0036] This embodiment describes a functional coating for the inner wall of a metal crucible. The coating is a double-layer coating, comprising an inner metal bonding layer and an outer ceramic coating. The outer ceramic raw material of the double-layer coating has the following composition by mass percentage: 49% ZrO2, 13% Dy2O3, 20% Er2O3, and 18% ZrO2. The inner raw material composition is Cr... 20 Ni 80 .

[0037] This embodiment describes a method for preparing a functional coating on the inner wall of a metal crucible, comprising the following steps:

[0038] (1) Clean and roughen the inner wall of the metal crucible. Acetone was used to clean the inner wall of the cast iron crucible, and 250μm white corundum was used for sandblasting at a pressure of 0.6MPa.

[0039] (2) The selected spraying powder is Cr 20 Ni 80 The alloy powder is used to plasma spray the inner wall of the treated crucible to form a metal bonding layer.

[0040] (3) Select a spraying powder with the following composition by mass percentage: 49% ZTA, 13% Dy2O3, 20% Er2O3 and 18% ZrO2, and perform plasma spraying on the surface of the metal connection layer to form the ceramic coating.

[0041] The process parameters of the plasma spraying process and powder feeding device in steps (2) and (3) are as follows: the plasma gas is Ar gas, the powder feeding gas flow rate is 6L•min-1, the arc power is 13KW, the spraying distance is 150mm, and the selected spraying powder particle size is 30μm.

[0042] Example 3

[0043] This embodiment describes a functional coating for the inner wall of a metal crucible. The coating is a double-layer coating, comprising an inner metal bonding layer and an outer ceramic coating. The outer ceramic raw material of the double-layer coating has the following composition by mass percentage: 49% ZrO2, 13% Dy2O3, 20% Er2O3, and 18% ZrO2. The inner raw material composition is Cr... 20 Ni 80 .

[0044] This embodiment describes a method for preparing a functional coating on the inner wall of a metal crucible, comprising the following steps:

[0045] (1) Clean and roughen the inner wall of the metal crucible. Acetone was used to clean the inner wall of the cast iron crucible, and 300μm white corundum was used for sandblasting at a pressure of 0.8MPa.

[0046] (2) The selected spraying powder is Cr20 Ni 80 The alloy powder is used to plasma spray the inner wall of the treated crucible to form a metal bonding layer.

[0047] (3) Select a spraying powder with the following composition by mass percentage: 49% ZTA, 13% Dy2O3, 20% Er2O3 and 18% ZrO2, and perform plasma spraying on the surface of the metal connection layer to form the ceramic coating.

[0048] The process parameters of the plasma spraying process and powder feeding device in steps (2) and (3) are as follows: the plasma gas is Ar gas, the powder feeding gas flow rate is 9L•min-1, the arc power is 16KW, the spraying distance is 200mm, and the selected spraying powder particle size is 40μm.

[0049] Example 4

[0050] This embodiment describes a functional coating for the inner wall of a metal crucible. The coating is a double-layer coating, comprising an inner metal bonding layer and an outer ceramic coating. The outer ceramic raw material of the double-layer coating has the following composition by mass percentage: 45% ZrO2, 14% Dy2O3, 22% Er2O3, and 19% ZrO2. The inner raw material composition is Cr... 20 Ni 80 .

[0051] This embodiment describes a method for preparing a functional coating on the inner wall of a metal crucible, comprising the following steps:

[0052] (1) Clean and roughen the inner wall of the metal crucible. Use alcohol to clean the inner wall of the cast iron crucible, and use 250μm white corundum for sandblasting at a pressure of 0.6MPa.

[0053] (2) The selected spraying powder is Cr 20 Ni 80 The alloy powder is used to plasma spray the inner wall of the treated crucible to form a metal bonding layer.

[0054] (3) Select a spraying powder with the following composition by mass percentage: 45% ZTA, 14% Dy2O3, 22% Er2O3 and 19% ZrO2, and perform plasma spraying on the surface of the metal connection layer to form the ceramic coating.

[0055] The process parameters of the plasma spraying process and powder feeding device in steps (2) and (3) are as follows: the plasma gas is Ar gas, the powder feeding gas flow rate is 6L•min-1, the arc power is 13KW, the spraying distance is 150mm, and the selected spraying powder particle size is 20μm.

[0056] Example 5

[0057] This embodiment describes a functional coating for the inner wall of a metal crucible. The coating is a double-layer coating, comprising an inner metal bonding layer and an outer ceramic coating. The outer ceramic raw material of the double-layer coating has the following composition by mass percentage: 45% ZrO2, 14% Dy2O3, 22% Er2O3, and 19% ZrO2. The inner raw material composition is Cr... 20 Ni 80 .

[0058] This embodiment describes a method for preparing a functional coating on the inner wall of a metal crucible, comprising the following steps:

[0059] (1) Clean and roughen the inner wall of the metal crucible. Use alcohol to clean the inner wall of the cast iron crucible, and use 250μm white corundum for sandblasting at a pressure of 0.6MPa.

[0060] (2) The selected spraying powder is Cr 20 Ni 80 The alloy powder is used to plasma spray the inner wall of the treated crucible to form a metal bonding layer.

[0061] (3) Select a spraying powder with the following composition by mass percentage: 45% ZTA, 14% Dy2O3, 22% Er2O3 and 19% ZrO2, and perform plasma spraying on the surface of the metal connection layer to form the ceramic coating.

[0062] The process parameters of the plasma spraying process and powder feeding device in steps (2) and (3) are as follows: the plasma gas is Ar gas, the powder feeding gas flow rate is 6L•min-1, the arc power is 13KW, the spraying distance is 150mm, and the selected spraying powder particle size is 30μm.

[0063] Example 6

[0064] This embodiment describes a functional coating for the inner wall of a metal crucible. The coating is a double-layer coating, comprising an inner metal bonding layer and an outer ceramic coating. The outer ceramic raw material of the double-layer coating has the following composition by mass percentage: 45% ZrO2, 14% Dy2O3, 22% Er2O3, and 19% ZrO2. The inner raw material composition is Cr... 20 Ni 80 .

[0065] This embodiment describes a method for preparing a functional coating on the inner wall of a metal crucible, comprising the following steps:

[0066] (1) Clean and roughen the inner wall of the metal crucible. Use alcohol to clean the inner wall of the cast iron crucible, and use 300μm white corundum for sandblasting at a pressure of 0.8MPa.

[0067] (2) The selected spraying powder is Cr 20 Ni 80 The alloy powder is used to plasma spray the inner wall of the treated crucible to form a metal bonding layer.

[0068] (3) Select a spraying powder with the following composition by mass percentage: 45% ZTA, 14% Dy2O3, 22% Er2O3 and 19% ZrO2, and perform plasma spraying on the surface of the metal connection layer to form the ceramic coating.

[0069] The process parameters of the plasma spraying process and powder feeding device in steps (2) and (3) are as follows: the plasma gas is Ar gas, the powder feeding gas flow rate is 9L•min-1, the arc power is 16KW, the spraying distance is 200mm, and the selected spraying powder particle size is 40μm.

[0070] Example 7

[0071] This embodiment describes a functional coating for the inner wall of a metal crucible. The coating is a double-layer coating, comprising an inner metal bonding layer and an outer ceramic coating. The outer ceramic raw material of the double-layer coating has the following composition by mass percentage: 41% ZrO2, 15% Dy2O3, 24% Er2O3, and 20% ZrO2. The inner raw material composition is Cr... 20 Ni 80 .

[0072] This embodiment describes a method for preparing a functional coating on the inner wall of a metal crucible, comprising the following steps:

[0073] (1) Clean and roughen the inner wall of the metal crucible. Acetone was used to clean the inner wall of the cast iron crucible, and 250μm white corundum was used for sandblasting at a pressure of 0.6MPa.

[0074] (2) The selected spraying powder is Cr 20 Ni 80 The alloy powder is used to plasma spray the inner wall of the treated crucible to form a metal bonding layer.

[0075] (3) Select a spraying powder with the following composition by mass percentage: 41% ZTA, 15% Dy2O3, 24% Er2O3, and 20% ZrO2, and perform plasma spraying on the surface of the metal connection layer to form the ceramic coating.

[0076] The process parameters of the plasma spraying process and powder feeding device in steps (2) and (3) are as follows: the plasma gas is Ar gas, the powder feeding gas flow rate is 6L•min-1, the arc power is 13KW, the spraying distance is 150mm, and the selected spraying powder particle size is 20μm.

[0077] Example 8

[0078] This embodiment describes a functional coating for the inner wall of a metal crucible. The coating is a double-layer coating, comprising an inner metal bonding layer and an outer ceramic coating. The outer ceramic raw material of the double-layer coating has the following composition by mass percentage: 41% ZrO2, 15% Dy2O3, 24% Er2O3, and 20% ZrO2. The inner raw material composition is Cr... 20 Ni 80 .

[0079] This embodiment describes a method for preparing a functional coating on the inner wall of a metal crucible, comprising the following steps:

[0080] (1) Clean and roughen the inner wall of the metal crucible. Acetone was used to clean the inner wall of the cast iron crucible, and 250μm white corundum was used for sandblasting at a pressure of 0.6MPa.

[0081] (2) The selected spraying powder is Cr 20 Ni 80 The alloy powder is used to plasma spray the inner wall of the treated crucible to form a metal bonding layer.

[0082] (3) Select a spraying powder with the following composition by mass percentage: 41% ZTA, 15% Dy2O3, 24% Er2O3, and 20% ZrO2, and perform plasma spraying on the surface of the metal connection layer to form the ceramic coating.

[0083] The process parameters of the plasma spraying process and powder feeding device in steps (2) and (3) are as follows: the plasma gas is Ar gas, the powder feeding gas flow rate is 6L•min-1, the arc power is 13KW, the spraying distance is 150mm, and the selected spraying powder particle size is 30μm.

[0084] Example 9

[0085] This embodiment describes a functional coating for the inner wall of a metal crucible. The coating is a double-layer coating, comprising an inner metal bonding layer and an outer ceramic coating. The outer ceramic raw material of the double-layer coating has the following composition by mass percentage: 41% ZrO2, 15% Dy2O3, 24% Er2O3, and 20% ZrO2. The inner raw material composition is Cr... 20 Ni 80 .

[0086] This embodiment describes a method for preparing a functional coating on the inner wall of a metal crucible, comprising the following steps:

[0087] (1) Clean and roughen the inner wall of the metal crucible. Acetone was used to clean the inner wall of the cast iron crucible, and 300μm white corundum was used for sandblasting at a pressure of 0.8MPa.

[0088] (2) The selected spraying powder is Cr 20 Ni 80 The alloy powder is used to plasma spray the inner wall of the treated crucible to form a metal bonding layer.

[0089] (3) Select a spraying powder with the following composition by mass percentage: 41% ZTA, 15% Dy2O3, 24% Er2O3, and 20% ZrO2, and perform plasma spraying on the surface of the metal connection layer to form the ceramic coating.

[0090] The process parameters of the plasma spraying process and powder feeding device in steps (2) and (3) are as follows: the plasma gas is Ar gas, the powder feeding gas flow rate is 9L•min-1, the arc power is 16KW, the spraying distance is 200mm, and the selected spraying powder particle size is 40μm.

[0091] Performance evaluation:

[0092] Since the coating materials used in Examples 1-3, 4-6, and 7-9 were the same but the preparation processes were different, the performance was evaluated by dividing the examples into three groups: Group 1 (Examples 1-3), Group 2 (Examples 4-6), and Group 3 (Examples 7-9). The hardness, wear resistance, and thermal conductivity of the three groups of examples were tested according to national standards, and the test results are shown below. Figure 2 , Figure 3 and Figure 4 .

[0093] The hardness changes in the examples are as follows Figure 2 As shown in the figure, the material hardness is positively correlated with the ZTA content. In Example 1, the ZTA content was 49%, and the hardness was 1906 HV. In Example 4, the ZTA content was 45%, and the hardness was 1730 HV. In Example 7, the ZTA content was 41%, and the hardness decreased to 1430 HV, but it was still much greater than the hardness of common coatings and crucible materials. Its wear resistance is as follows: Figure 3 As shown, after being subjected to 320-grit abrasive wear, its wear loss volume is still less than 5.591 mm. 3 The minimum thickness can reach 4.936mm. 3 This fully demonstrates that the coating material possesses excellent strength, hardness, and wear resistance. Its thermal conductivity at 600℃ is as follows: Figure 4 As shown, the thermal conductivity of the coating material increases with the increase in the proportion of Er2O3 and ZrO2, reaching a maximum of 14.1 W / (m·K). This fully demonstrates the significant effect of Er2O3 and ZrO2 on improving the thermal conductivity of the coating material.

[0094] It should be noted that although the above three embodiments are described, this does not limit the scope of patent protection for this invention. Therefore, any modifications or alterations made to the above technical solutions based on the innovative concept of this invention fall within the scope of patent protection for this invention.

Claims

1. A method for preparing a functional coating on the inner wall of a metal crucible, characterized in that, The coating is a double-layer coating, comprising an inner metal bonding layer and an outer ceramic coating; the outer ceramic layer of the double-layer coating is composed of zirconia-toughened alumina ceramic (ZTA), Dy2O3, Er2O3, and ZrO2; the inner metal bonding layer of the double-layer coating is composed of Cr... 20 Ni 80 Composition; the outer ceramic raw material of the double-layer coating is composed of the following by mass percentage: ZrO2 41-49%, Dy2O3 13-15%, Er2O3 20-24%, ZrO2 18-20%; The preparation method includes the following steps: (1) Pre-treat the inner wall of the metal crucible; (2) The selected spraying powder is Cr 20 Ni 80 The alloy powder is used to plasma spray the inner wall of the treated crucible to form the metal bonding layer. (3) The spraying powder is selected with the following composition by mass percentage: Dy2O3 13-15%, Er2O3 20-24%, ZrO2 18-20%, and the balance is zirconia toughened alumina ceramic (ZTA). Plasma spraying is performed on the surface of the metal connection layer to form the ceramic coating. The process parameters for plasma spraying in steps (2) and (3) are as follows: the plasma gas is Ar gas, the powder feeding gas flow rate is 6-9 L•min-1, the arc power is 13-16 KW, the spraying distance is 150-200 mm, and the selected spraying powder particle size is 20-40 μm.

2. The method for preparing a functional coating on the inner wall of a metal crucible according to claim 1, characterized in that, The pretreatment steps described in step (1) include cleaning the inner wall of the metal crucible and roughening its surface.

3. The method for preparing a functional coating on the inner wall of a metal crucible according to claim 2, characterized in that, The inner wall cleaning in step (1) uses acetone or alcohol to clean the oil stains on the inner surface of the metal crucible, and the surface roughening treatment is to perform surface sandblasting treatment on the inside of the crucible.

4. The method for preparing a functional coating on the inner wall of a metal crucible according to claim 3, characterized in that, The surface sandblasting treatment in step (1) uses white corundum with a particle size of 250-300μm for sandblasting, and the sandblasting pressure is 0.5-0.8MPa.

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