A metal ceramic coating scraper containing reaction-synthesized TiO2 and its preparation method

Abstract

The present invention discloses a scraper coated with a metal ceramic coating containing reaction-synthesized TiO2 and a preparation method thereof. The raw materials of the metal ceramic coating are Ti powder and one of WC-Co, WC-CoCr, WC-Cr3C2-NiCr, and Cr3C2-NiCr. WC-Co, WC-CoCr, WC-Cr3C2-NiCr, and Cr3C2-NiCr are used as metal ceramic powders, and the mixing ratio of the metal ceramic powder to the Ti powder is 1:9-1:4. The metal oxide of the metal ceramic coating is Ti powder in the coating raw material, which is oxidized at high temperature during thermal spraying to generate TiO2, and is deposited together with the metal ceramic phase on the surface of the scraper blade to obtain TiO2. 2‑ The Ti powder mixed in the metal ceramic powder is heated in a high-speed high-temperature flame flow and produces an oxygen absorption reaction to generate TiO2, thereby obtaining TiO 2‑ The wear-resistant composite coating is a uniform mixture of metal and ceramic, and the TiO2 generated by the self-oxidation reaction during the spraying process reduces the thermal conductivity of the coating, blocking the heat generated by friction at the moment of scraper operation from being transferred to the scraper blade substrate, causing the scraper to lose dimensional accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of coating scrapers with ceramic coatings, in particular to a coating scraper with a metal ceramic coating containing reaction-synthesized TiO2 and a preparation method thereof. Background Art

[0002] A coating blade is a production tool that applies a thin layer of coating evenly to a uniformly moving paper web, improving the surface finish of the paper. During the coating process, paper fibers and solid particles such as kaolin in the coating slurry severely abrade the blade edge, causing rapid wear and failure and requiring frequent replacement. With increasing paper machine speeds, coating blades with metal-ceramic composite coatings such as WC-Co, WC-CoCr, or WC / Cr3C2-NiCr have gained widespread application in production. These metal-ceramic composite coatings offer advantages such as high hardness and excellent wear resistance, significantly extending the service life of coating blades. Furthermore, the metal-ceramic coating's excellent toughness makes it less susceptible to chipping during blade installation and coating. However, WC and Cr2Cr3 ceramics have good thermal conductivity. At the moment of coating production, the coating slurry has not yet reached the paper surface. The paper and the scraper blade are in a dry friction state. The high-speed relative motion causes the scraper blade to heat up rapidly. The heat is quickly transferred to the substrate through the metal ceramic coating with good thermal conductivity, causing the blade to expand due to heat. However, the scraper is firmly pressed in the scraper clamp and cannot expand freely. Ultimately, the blade produces constrained strain and appears wavy, losing dimensional accuracy.

[0003] After extensive searching, the existing technology was found: publication number CN1668390A, which discloses a coating knife and a preparation method thereof. Its essence is a coating scraper with a sacrificial coating on the edge of the blade and a preparation method. A layer of polymer film is coated on the surface of the ceramic coating on the blade of the scraper. The isolation and lubrication effect of the polymer film layer is utilized to reduce or eliminate the dry friction between the blade and the paper web during the loading stage of the scraper, thereby reducing the heat generated by friction and avoiding deformation of the scraper blade due to excessive temperature rise.

[0004] In summary, from the perspective of material thermal conductivity, oxide ceramics generally have poor thermal conductivity. Typical oxide ceramics include ZrO2, with a thermal conductivity of approximately 5-8 W / (m·K), TiO2, with a thermal conductivity of approximately 1.809-10.3 W / (m·K), and Cr2O3 ceramics, with a thermal conductivity of approximately 2.6-2.8 W / (m·K). Metal ceramics, which combine the properties of both metals and ceramics, generally have higher thermal conductivity. Typical thermal conductivity of WC is approximately 80-110 W / (m·K), and that of Cr3C2 is approximately 19-22 W / mK. Compared to oxide ceramics, metal ceramics offer the advantages of good toughness, high hardness, and excellent wear resistance. If oxide ceramics and metal ceramics are mixed and sprayed to form a composite coating, the low thermal conductivity of the oxide ceramic and the high hardness and wear resistance of the metal ceramic can be fully utilized. However, metal ceramics are generally coated using a supersonic spraying process, while oxide ceramics have poor thermal conductivity and a high melting point, and are generally coated using a plasma spraying process. The mixed powders of the two cannot be coated using the same spraying method. Summary of the Invention

[0005] The object of the present invention is to provide a metal ceramic coating scraper containing reaction-synthesized TiO2 and a preparation method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above objectives, the present invention provides the following technical solutions: a metal ceramic coating blade containing reaction-synthesized TiO2 and a preparation method thereof, wherein the raw materials for the metal ceramic coating are Ti powder and one of WC-Co, WC-CoCr, WC-Cr3C2-NiCr, and Cr3C2-NiCr, wherein WC-Co, WC-CoCr, WC-Cr3C2-NiCr, and Cr3C2-NiCr are used as the metal ceramic powder, and the mixing ratio of the metal ceramic powder to the Ti powder is 1:9-1:4;

[0007] The metal oxide of the metal ceramic coating is TiO2 which is generated by high temperature oxidation during the thermal spraying process of the Ti powder in the coating raw material and is deposited together with the metal ceramic phase on the surface of the scraper blade to obtain TiO2. 2- Metal-ceramic composite low thermal conductivity coating.

[0008] Preferably, during the spraying process, the Ti powder reacts with O2 in the supersonic spraying flame to be completely or partially oxidized to generate TiO2, thereby obtaining a composite coating in which TiO2 and metal ceramics are uniformly mixed.

[0009] Preferably, the metal ceramic powder in the spraying raw materials is a raw material suitable for supersonic spraying that is a composite of metal ceramic phase and alloy. The raw material is one of WC-Co, WC-CoCr, WC-Cr3C2-NiCr, and Cr3C2-NiCr. After the raw material powder is mixed with Ti powder, it is sprayed using a weak oxidizing flame flow. The O2 in the high-temperature flame flow reacts with Ti to obtain a composite coating.

[0010] Preferably, the preparation method of the metal ceramic coating scraper is as follows:

[0011] S1: Preparation of metal-metal ceramic mixed powder;

[0012] S2: coating was prepared by supersonic spraying process;

[0013] S3: Grinding the blade coating at an angle according to coating requirements to obtain a finished coated blade with a metal oxide-cermet composite coating.

[0014] Preferably, in S1 of the method for preparing a metal ceramic coating blade:

[0015] Pure Ti powder and metal ceramic powder for thermal spraying are selected, and one of WC-Co, WC-CoCr, WC-Cr3C2-NiCr and Cr3C2-NiCr is selected, and the pure Ti powder and the metal ceramic powder for thermal spraying are uniformly mixed according to proportion.

[0016] Preferably, in S1 of the method for preparing a metal ceramic coating blade:

[0017] The content of Ti powder in the mixed powder is 10%-25%, and the rest is metal ceramic powder. The particle size of the Ti powder is 15-30 μm.

[0018] Preferably, in S2 of the preparation method of the metal ceramic coating blade:

[0019] The mixed metal-metal ceramic powder is placed in an oven, heated to 60-100°C and dried for 2 hours;

[0020] The blade of the scraper is pre-grinded, the part to be sprayed is sandblasted, and the rest of the scraper is masked with masking tape. Within 2 hours after sandblasting, the dried metal-metal ceramic mixed powder is sprayed using the supersonic flame spraying process.

[0021] Preferably, in S2 of the preparation method of the metal ceramic coating blade:

[0022] Before feeding powder into the supersonic flame, the O2 and fuel gas flow rates are adjusted to obtain a weak oxidizing flame. During the spraying process, the Ti powder in the mixed powder enters the supersonic flame and is heated to a molten state. The Ti element has strong chemical activity at high temperatures and easily absorbs oxygen to produce an oxidation reaction to generate Ti oxide TiO2.

[0023] Preferably, in S2 of the preparation method of the metal ceramic coating blade:

[0024] The metal oxides generated by the reaction and the metal ceramics in the mixed powder are continuously heated and accelerated by the supersonic jet flame flow, and are deposited on the surface of the scraper substrate to obtain a metal oxide-metal ceramic composite coating.

[0025] Preferably, in S3 of the method for preparing a scraper coated with a metal ceramic coating: precision grinding and polishing to Ra 0.3-0.4 μm.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. A low thermal conductivity coating composed of metal oxide and metal ceramic is obtained by supersonic spraying, which avoids the need to use two different types of ceramic materials to prepare coatings separately using two spraying processes, and avoids the phenomenon that the ceramic coating scraper uses layered oxide as the thermal insulation layer, which easily leads to cracking or local peeling of the coating. The process is simple and has good formability.

[0028] 2. Selecting Ti powder as the metal phase in the spraying raw material fully utilizes the high chemical activity of Ti element and its strong oxygen absorption reaction ability at high temperature (≥800℃). When Ti is oxidized to generate TiO2, heat is released, which is more conducive to the increase of flame temperature and the melting of coating material during spraying. After being deposited on the substrate surface, a metal oxide-ceramic composite coating with high bonding strength and high density is obtained.

[0029] 3. By changing the content of Ti element, the content of oxide phase in the mixed coating can be easily regulated, and the thermal conductivity of the composite coating can be regulated.

[0030] 4. The present invention uses Ti powder, which has a room temperature thermal conductivity of 14.6 W / (m·K). It is an element with relatively poor thermal conductivity among metal materials. The thermal conductivity of TiO2 generated after oxidation during the spraying process is even lower. Even if some incompletely oxidized Ti metal exists during the spraying process, it can still effectively reduce the thermal conductivity of the composite coating.

[0031] 5. The raw materials of the coating of the present invention are widely available, and the coating preparation process is the supersonic spraying process commonly used in industry. The process is simple and the construction technology is mature. The preparation of the blade coating can be completed without special equipment or complicated processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the scraper structure of the present invention;

[0033] Figure 2 This is an enlarged microstructure diagram of the scraper blade section of the present invention;

[0034] Figure 3 This is a table showing the thermal conductivity test results of different types of coating + substrate samples of the present invention. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] See also Figures 1 to 3 , the present invention provides three embodiments:

[0037] Example 1:

[0038] Ti powder and WC-10Co4Cr metal ceramic powder are selected as spraying raw materials. After supersonic spraying, a ceramic coating composed of TiO2 and WC-10Co4Cr is obtained. The specific steps are as follows:

[0039] S1: Ti powder with a particle size of 10-30 μm and WC-10Co4Cr metal ceramic powder are uniformly mixed in a ratio of 1:9. Then, the mixture is placed in a drying oven and heated to 80°C for 2 hours for later use.

[0040] S2: Pre-grind the blade edge, roughen the area to be sprayed by sandblasting, and mask the rest of the area to avoid being affected by sandblasting and spray jets.

[0041] S3: The mixed and dried powders were sprayed using a DJ2700 supersonic spraying machine. The spraying process parameters were: air flow rate of 310 nlpm, oxygen flow rate of 240 nlpm, propane flow rate of 65 nlpm, carrier gas flow rate of 12 nlpm, powder feed rate of 35 g / min, spraying distance of 230 mm, single spray thickness of 0.02 mm, coating thickness of 0.20 mm, and coating thickness of 0.15 mm after precision grinding and polishing. The surface finish was Ra 0.3-0.4 μm. This resulted in a ceramic-coated scraper with a TiO2-WC-10Co4Cr composite coating on the blade.

[0042] Example 2:

[0043] Ti powder and WC-12Co metal ceramic powder are selected as spraying raw materials. After supersonic spraying, a ceramic coating composed of TiO2 and WC-12Co is obtained. The specific steps are as follows:

[0044] S1: Ti powder with a particle size of 10-30 μm and WC-12Co metal ceramic powder are uniformly mixed in a ratio of 15:85. Then, the mixture is placed in a drying oven and heated to 80°C for 2 hours for later use.

[0045] S2: Pre-grind the blade edge, roughen the area to be sprayed by sandblasting, and mask the rest of the area to avoid being affected by sandblasting and spray jets.

[0046] S3: The mixed and dried powders were sprayed using a DJ2700 supersonic spraying machine. The spraying process parameters were: air flow rate of 310 nlpm, oxygen flow rate of 230 nlpm, propane flow rate of 60 nlpm, carrier gas flow rate of 12 nlpm, powder feed rate of 40 g / min, spraying distance of 260 mm, single spray thickness of 0.02 mm, coating thickness of 0.20 mm, and coating thickness of 0.15 mm after precision grinding and polishing. The surface finish was Ra 0.3-0.4 μm. This resulted in a ceramic-coated scraper with a TiO2-WC-12Co composite coating on the blade.

[0047] Example 3:

[0048] Ti powder and WC-Cr3C2-NiCr metal ceramic powder are selected as spraying raw materials. After supersonic spraying, a ceramic coating composed of TiO2 and WC-Cr3C2-NiCr is obtained. The specific steps are as follows:

[0049] S1: Ti powder with a particle size of 10-30 μm and WC-Cr3C2-NiCr metal ceramic powder are uniformly mixed in a ratio of 2:8. Then, the mixture is placed in a drying oven and heated to 80°C for 2 hours for later use.

[0050] S2: Pre-grind the blade edge, roughen the area to be sprayed by sandblasting, and mask the rest of the area to avoid being affected by sandblasting and spray jets.

[0051] S3: The mixed and dried powders were sprayed using a DJ2700 supersonic spraying machine. The spraying process parameters were: air flow rate of 310 nlpm, oxygen flow rate of 230 nlpm, propane flow rate of 60 nlpm, carrier gas flow rate of 12 nlpm, powder feed rate of 40 g / min, spraying distance of 265 mm, single spray thickness of 0.02 mm, coating thickness of 0.20 mm, and coating thickness of 0.15 mm after precision grinding and polishing. The surface finish was Ra 0.3-0.4 μm. This resulted in a ceramic-coated scraper with a TiO2-WC-Cr3C2-NiCr composite coating on the blade.

[0052] The same method as in Examples 1-3 was used to prepare standard samples for thermal conductivity testing. The standard samples were 0.15 mm supersonic spray coating + 0.5 mm thick SK4 steel plate as the base material. The base materials were the same, so the thermal conductivity of the samples can be used to qualitatively evaluate the thermal conductivity of the coating. The measurement results are attached in the attached instructions. Figure 3 shown.

[0053] The thermal conductivity of samples with oxide TiO2 ceramic coating is significantly reduced, especially the samples with TiO2-WC-Cr3C2-NiCr composite coating, which has lower thermal conductivity and can well meet the performance requirements of coating blades for high-speed paper machines.

[0054] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for preparing a metal ceramic coating blade containing reactively synthesized TiO2, characterized in that: The preparation method of the metal ceramic coating scraper is as follows: S1: Preparation of metal-metal ceramic mixed powder; S2: coating was prepared by supersonic spraying process; S3: Grinding the blade coating at an angle according to coating requirements to obtain a finished coated blade with a metal oxide-cermet composite coating; The raw materials of the metal ceramic coating are Ti powder and one of WC-Co, WC-CoCr, WC-Cr3C2-NiCr, and Cr3C2-NiCr, WC-Co, WC-CoCr, WC-Cr3C2-NiCr, and Cr3C2-NiCr are used as metal ceramic powders, and the mixing ratio of the metal ceramic powder to TiO2 is 1:9-1:4; The metal oxide of the metal ceramic coating is TiO2, which is generated by high-temperature oxidation of Ti powder in the coating raw material during thermal spraying and is deposited together with the metal ceramic phase on the surface of the scraper blade to obtain a TiO2 metal ceramic composite low thermal conductivity coating; During the spraying process, Ti powder reacts with O2 in the supersonic spray flame to be completely or partially oxidized to generate TiO2, thereby obtaining a composite coating uniformly mixed with TiO2 and metal ceramics. Among the spraying raw materials, the metal ceramic powder is a raw material that is a composite of metal ceramic phase and alloy and is suitable for supersonic spraying. The raw material is one of WC-Co, WC-CoCr, WC-Cr3C2-NiCr, and Cr3C2-NiCr. The raw material powder is mixed with Ti powder and then sprayed using a weak oxidizing flame flow. O2 in the high-temperature flame flow reacts with Ti to obtain a composite coating. In S1 of the method for preparing a metal-ceramic coating blade: the content of Ti powder in the mixed powder is 10%-25%, and the rest is metal-ceramic powder, and the particle size of the Ti powder is 15-30 μm; Before feeding powder into the supersonic flame, adjust the O2 and fuel gas flow rates to obtain a weakly oxidizing flame.

2. The method for preparing a metal ceramic coating blade containing reactively synthesized TiO2 according to claim 1, characterized in that: Preparation method S1 of a metal-ceramic coating blade: Pure Ti powder and metal ceramic powder for thermal spraying are selected, and one of WC-Co, WC-CoCr, WC-Cr3C2-NiCr and Cr3C2-NiCr is selected, and the pure Ti powder and the metal ceramic powder for thermal spraying are uniformly mixed according to proportion.

3. The method for preparing a metal ceramic coating blade containing reactively synthesized TiO2 according to claim 1, characterized in that: Method S2 for preparing a scraper coated with a metal ceramic coating: The mixed metal-metal ceramic powder is placed in an oven, heated to 60-100°C and dried for 2 hours; The blade of the scraper is pre-grinded, the part to be sprayed is sandblasted, and the rest of the scraper is masked with masking tape. Within 2 hours after sandblasting, the dried metal-metal ceramic mixed powder is sprayed using the supersonic flame spraying process.

4. The method for preparing a metal ceramic coating blade containing reactively synthesized TiO2 according to claim 1, characterized in that: Method S2 for preparing a scraper coated with a metal ceramic coating: During the spraying process, the Ti powder in the mixed powder enters the supersonic flame flow and is heated to a molten state. The Ti element has strong chemical activity at high temperatures and easily absorbs oxygen to produce an oxidation reaction to generate Ti oxide TiO2.

5. The method for preparing a metal ceramic coating blade containing reactively synthesized TiO2 according to claim 1, characterized in that: Method S2 for preparing a scraper coated with a metal ceramic coating: The metal oxides generated by the reaction and the metal ceramics in the mixed powder are continuously heated and accelerated by the supersonic jet flame flow, and are deposited on the surface of the scraper substrate to obtain a metal oxide-metal ceramic composite coating.

6. The method for preparing a metal ceramic coating blade containing reactively synthesized TiO2 according to claim 1, characterized in that: In S3 of the method for preparing a metal-ceramic coating blade: precision grinding and polishing to Ra 0.3-0.4 μm.

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