Cerium oxide modified flux-cored wire and preparation method and application thereof

Abstract

This invention relates to the field of welding materials technology, and more particularly to a cerium oxide modified powder-cored welding wire, its preparation method, and its application. The cerium oxide modified powder-cored welding wire of this invention comprises a powder core and an outer sheath, with the powder core filling the outer sheath. The powder-cored welding wire uses an Fe-Al alloy as the matrix phase, Cr3C2 as the reinforcing phase, and also includes CeO2, Ni, and Fe2O3. The Fe-Al alloy is an ordered intermetallic compound with low density and low cost, and it also imparts excellent oxidation and sulfidation resistance, corrosion resistance in various media, and high high-temperature strength to the powder-cored welding wire. Cr3C2, as a reinforcing phase, exhibits good high-temperature stability and matches well with the physicochemical properties of the Fe-Al matrix, further improving the performance of the powder-cored welding wire. The powder-cored welding wire of this invention, by incorporating rare earth cerium oxide, Ni, and Fe2O3, can improve the overall performance of the composite coating formed by the powder-cored welding wire.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, and in particular to a cerium oxide modified powder-cored welding wire, its preparation method, and its application. Background Technology

[0002] High-speed arc spraying (HSA) is a novel spraying technology that utilizes gas dynamics principles. High-pressure air or high-temperature combustion gas is accelerated through a specially designed nozzle and used as a high-speed atomizing gas stream to atomize and accelerate molten metal, propelling the atomized particles at high speed onto the workpiece surface to form a dense coating. HSA offers excellent atomization, with particle velocities reaching up to 350 m / s. The coating density and bonding strength are similar to those of plasma spraying and high-velocity oxygen fuel (HVOF) spraying, making it a preferred method for corrosion and wear protection in power systems.

[0003] Thermal spray metal coatings are among the earliest researched and applied wear-resistant coatings. They include Ni-Cr alloy and Fe-Cr alloy series coatings. These coatings have high bonding strength with the substrate and good resistance to thermal corrosion and thermal fatigue. They can be prepared by technologies such as flame spraying, supersonic flame spraying, plasma spraying, arc spraying, and high-speed arc spraying (HVAS). They are mainly used for wear parts in corrosive environments. Their disadvantages are high price and decreased wear resistance at high temperatures.

[0004] With the continuous improvement of powder-cored wire manufacturing technology, high-carbon stainless steel coatings, amorphous coatings, metal-ceramic composite coatings, and intermetallic compound-based composite coatings have emerged, greatly promoting the development of efficient, high-quality, and low-cost arc-sprayed wear-resistant coating technology and showing promising industrial application prospects. Developing novel high-temperature anti-corrosion and wear-resistant composite coatings, improving the coating's microstructure and properties, and expanding its industrial application range will be an important development direction for arc-spraying technology. Summary of the Invention

[0005] This invention proposes a cerium oxide modified powder-cored welding wire, its preparation method, and its application, in order to solve the problems of high price and decreased wear resistance at high temperatures in existing arc-sprayed wear-resistant coatings.

[0006] According to a first aspect of the present invention, the present invention provides a cerium oxide modified powder-cored welding wire, the powder-cored welding wire comprising a powder core and an outer sheath, the powder core being filled within the outer sheath; the powder-cored welding wire uses an Fe-Al alloy as the matrix phase, Cr3C2 as the reinforcing phase, and further comprises CeO2, Ni and Fe2O3.

[0007] In the above scheme, the theoretical basis for material selection of the cerium oxide modified powder-cored welding wire of the present invention is as follows:

[0008] 1. Selection of matrix phase

[0009] Fe-Al alloys are ordered intermetallic compounds. Intermetallic compounds refer to alloy phases with metallic properties formed between metallic elements or between metals and metalloids, based on stoichiometric compounds with variable compositions within a certain range. Fe-Al alloys possess excellent oxidation and sulfidation resistance, corrosion resistance in various media, high high-temperature strength, low density, and are low-cost as they do not contain precious alloying elements, making them a potentially ideal high-temperature structural material. However, the low room-temperature plasticity and low fracture resistance of Fe-Al alloys severely degrade their forming processability, greatly limiting their engineering applications. Since the 1980s, significant progress has been made in strengthening and toughening various intermetallic compounds, including Fe3Al and FeAl, and research on intermetallic compound-based composite materials has received increasing attention, but it is far from reaching the level of large-scale industrial application. Currently, there are very few research reports on Fe-Al alloy coatings, and their preparation processes are limited to methods such as self-propagating combustion synthesis, supersonic flame powder spraying, magnetron sputtering deposition, and welding. To broaden the application fields of Fe-Al alloys and overcome their process shortcomings such as difficult forming, the principle of high-speed arc spraying rapid metallurgy is applied to dynamically form Fe-Al and Fe-Al-based composite coatings. The formation mechanism of their microstructure is studied, and the room temperature and high temperature performance of the coatings are comprehensively evaluated, which has important theoretical and engineering significance.

[0010] 2. Selection of the reinforcing phase

[0011] The fundamental requirement for the design of intermetallic compound matrix composites is that the reinforcing phase and the matrix must have good physical and chemical compatibility. Intermetallic compound matrix composite components undergo numerous cycles from room temperature to service temperature during use; therefore, a good match between the thermal expansion coefficients of the reinforcing phase and the matrix is ​​essential. The reinforcing phases in intermetallic compound matrix composites are mainly hard ceramic phases, whose thermal expansion coefficients are generally lower than those of the intermetallic compounds (see Table 1). Mismatches in the thermal expansion coefficients between the reinforcing phase and the matrix significantly affect the interfacial structure and properties of the composite material. Ceramic / intermetallic compound systems with very similar thermal expansion coefficients exhibit high physical compatibility, and correspondingly, such intermetallic compound matrix composites possess relatively high strength and toughness. However, when significant stress concentration occurs at the interface between the reinforcing phase and the matrix, it can lead to crack formation or even complete delamination within the matrix.

[0012] Table 1. Room temperature thermal expansion coefficients of several intermetallic compounds and ceramic reinforcing phases

[0013] compound <![CDATA[Fe3Al FeAl Ni3Al NiAl Ti3Al TiAl Al2O3 t-ZrO2 MgO]]> <![CDATA[α / (10 -6 ℃ -1 )]]> 12.5 21.8 11.0 15.1 10.1 11.0 9.4 12.8 13.8 compound <![CDATA[TiN AlN Si3N4 SiC B4C TiC ZrC Cr3C2 WC VC ZrB2]]> <![CDATA[α / (10 -6 ℃ -1 )]]> 9.3 5.1 2.7 4.8 4.5 7.7 7.5 11.7 6.2 7.3 5.5

[0014] Intermetallic compound matrix composites undergo prolonged high-temperature treatment during use. At high temperatures, the extensive dissolution of the reinforcing phase within the matrix or its vigorous reaction with the matrix not only leads to the loss of the reinforcing phase but also causes changes in the composite's composition and properties. Therefore, the chemical compatibility of the reinforcing phase-matrix interface is a crucial issue. Reaction thermodynamics calculations are commonly used to select the reinforcing phase, but these calculations are usually limited to solid-state reaction processes and simple reactions where the reaction products are binary compounds. To overcome the limitations of thermodynamic calculations, appropriate experimental studies are necessary to determine the chemical compatibility of the reinforcing phase-matrix interface. As shown in Table 2, the reinforcing phase / Fe-Al intermetallic compound composite system can be categorized into three different types: non-reactive systems, weakly reactive systems, and reactive systems.

[0015] In reactive systems, strong interfacial reactions generate a large number of reaction products, often reducing the bonding strength between the reinforcing phase and the matrix interface. In non-reactive systems, the bonding between the reinforcing phase and the matrix interface is weak and the bonding strength is also low. Only in weakly reactive systems can a moderate interfacial reaction result in a strong bonding force between the reinforcing phase and the matrix interface. Therefore, considering the good interfacial chemical compatibility between the reinforcing phase and the matrix, selecting compounds such as Cr3C2 that undergo weak chemical reactions with the matrix as the reinforcing phase for manufacturing Fe-Al intermetallic compound coatings is appropriate. It is worth noting that the chemical compatibility between the reinforcing phase and the matrix interface is related not only to the system composition but also to the composition of the composite material and the preparation process parameters.

[0016] Table 2 Chemical compatibility of ceramic reinforcement phases with Fe-Al intermetallic compound interfaces

[0017] Chemical compatibility Enhanced phase reaction <![CDATA[SiC B4N Si3N4 Sialon B C]]> Weak reaction <![CDATA[TiC TiB2 TiN ZrB2 VC WC Cr3C2]]> No response <![CDATA[Al2O3 ZrO2 MgO Y2O3]]>

[0018] 3. The improving effect of rare earth CeO2

[0019] The alloying principle of heat-resistant steel states that when the content of active alloying elements with a high affinity for oxygen, such as Cr and Al, exceeds a critical content, a thin, dense, and continuous oxide film can be formed on the alloy surface through selective oxidation. This film hinders the further diffusion of oxygen atoms into the alloy interior and the outward diffusion of metal ions across the film, thus protecting the alloy from further oxidation and giving it good oxidation resistance in high-temperature oxidizing environments. Although Cr2O3 and Al2O3 films effectively hinder the diffusion of oxygen and metal ions, both are prone to mechanical failure, especially during thermal cycling due to film-substrate detachment. The most effective measure to reduce such failures is to add trace amounts of active elements, such as rare earth cerium oxide, to the alloy, resulting in a significant improvement in film-substrate bonding strength and the integrity of the protective film during thermal cycling. Therefore, the powder-cored welding wire of this invention adds rare earth Cr2O3 to the Fe-Al alloy, which can improve both film-substrate bonding and thermal spraying process performance.

[0020] 4. The roles of Ni and Fe2O3

[0021] Ni is an element that forms and stabilizes austenite. Ni and Fe can exist in a mutually soluble form in austenite and ferrite structures, playing a role in solid solution strengthening. Simultaneously, Ni can lower the impact transformation temperature and improve low-temperature impact toughness. Studies have shown that as the Ni content in the weld increases, the tensile strength of the weld joint increases, and adding an appropriate amount of Ni to the weld metal can improve the impact energy of the weld joint. Fe₂O₃ increases the melting point of the core filler mixture, improves the weld elongation and low-temperature impact toughness, and reduces the size and number of inclusions.

[0022] Compared to the base material, the powder-cored welding wire of this invention has better resistance to friction and wear at room temperature and excellent resistance to high-temperature corrosion, and is relatively inexpensive. It is a novel coating material worthy of vigorous promotion. However, due to limitations in manufacturing processes and alloy smelting, the possibility of producing a solid alloy wire is very small. In non-solid alloy wires, i.e., powder-cored welding wires, the powder core can stabilize the arc, improve operational performance, and provide protection. Powder-cored welding wires can provide both gas protection and slag protection, and their deposition rate is faster than that of solid alloy wires. Powder-cored welding wires are suitable for all-position welding, while solid alloy wires are only suitable for thin-plate welding.

[0023] Furthermore, the raw materials for preparing the powder core include Cr3C2 powder, Ni powder, Al powder, and CeO2 powder.

[0024] The chemical composition of the powder core can be freely adjusted according to different application requirements. Furthermore, by weight percentage, the raw materials for preparing the powder core include 20-57% Cr3C2 powder, 2-5.8% Ni powder, 10-28.5% Al powder, and 3-10% CeO2 powder.

[0025] Furthermore, by weight percentage, the raw materials for preparing the powder core also include 0-10% Fe2O3 powder.

[0026] Furthermore, the raw materials for preparing the powder core also include 0-65% Fe powder by weight percentage.

[0027] Furthermore, the outer skin is selected from carbon steel or stainless steel; preferably, the outer skin is selected from 08F carbon steel strip or 0Cr19Ni9 stainless steel strip.

[0028] In the above scheme, 08F carbon steel strip has good plastic processing properties and does not require intermediate annealing heat treatment. 0Cr19Ni9 stainless steel strip exhibits severe work hardening, requiring intermediate annealing when formed using the rolling and drawing process, but can be continuously formed using the rolling process.

[0029] Furthermore, the diameter of the powder-cored welding wire is 1-3 mm, preferably 2 mm. The diameter of the powder-cored welding wire can be selected and controlled according to actual needs.

[0030] Furthermore, the filling rate of the powder core in the outer skin is 20-30%, preferably 25%.

[0031] According to a second aspect of the present invention, the present invention also provides a method for preparing the above-mentioned powder-cored welding wire, comprising the following steps:

[0032] First, the raw materials for preparing the core are mixed evenly, and the outer sheath is rolled into a "U"-shaped outer sheath with a "U"-shaped cross section. Then, the evenly mixed core raw materials are filled into the "U"-shaped groove of the outer sheath, and the outer sheath with the core raw materials is rolled into a circular cross section by multi-roll continuous rolling. During the rolling process, the ends of the outer sheath adopt a butt joint form. Finally, the core welding wire that meets the size requirements is produced through multiple continuous drawing and winding processes.

[0033] According to a third aspect of the invention, the invention also provides the application of the above-described powder-cored welding wire as a coating on structural components. The structural components can be wear parts exposed to corrosive environments.

[0034] Preferably, the coating is formed by spraying the powder-cored welding wire onto the surface of the structural component using a supersonic arc spraying method.

[0035] Among the above methods, supersonic arc spraying offers advantages such as high efficiency and low cost compared to other spraying methods. A composite coating is created on the surface of structural materials using supersonic arc spraying of lead-cored welding wire. A comprehensive comparison of the performance of the composite coating verifies the wide applicability of lead-cored welding wire.

[0036] Preferably, the spraying technical parameters for supersonic arc spraying include: spraying voltage of 31-33V, spraying current of 175-185A, spraying air pressure of 0.40-0.45MPa, and spraying distance of 280-320mm.

[0037] The beneficial effects of this invention are:

[0038] This invention discloses a cerium oxide modified powder-cored welding wire, comprising a powder core and an outer sheath. The powder core fills the outer sheath. The powder-cored welding wire uses an Fe-Al alloy as the matrix phase and Cr3C2 as the reinforcing phase, and also includes CeO2, Ni, and Fe2O3. Fe-Al alloy is an ordered intermetallic compound with excellent oxidation and sulfidation resistance, corrosion resistance in various media, high high-temperature strength, low density, and no expensive alloying elements, making it an ideal high-temperature structural material. The low-cost Fe-Al alloy is selected as the matrix phase, and Cr3C2, which has good high-temperature stability and good physicochemical properties matching the Fe-Al matrix, is selected as the reinforcing phase. Furthermore, the addition of rare earth cerium oxide (Ni) and Fe2O3 to the powder-cored welding wire of this invention improves the overall performance of the composite coating formed by the powder-cored welding wire. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 A process flow diagram of a method for preparing cerium oxide modified powder-cored welding wire according to an embodiment of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0042] For any techniques or conditions not specifically specified in the embodiments and comparative examples, the techniques or conditions described in the literature in this field, or the product instructions, shall be followed. Instruments and other equipment whose manufacturers are not specified can be purchased from reputable suppliers. All chemical raw materials used in this invention are readily available in the domestic chemical market.

[0043] Examples 1-6

[0044] Examples 1-6 provide a cerium oxide modified powder-cored welding wire, which includes a powder core and an outer sheath, with the powder core filling the outer sheath. The powder-cored welding wire uses Fe-Al alloy as the matrix phase, Cr3C2 as the reinforcing phase, and also includes CeO2, Ni and Fe2O3.

[0045] 1. Selection of outer skin

[0046] Two representative outer sheaths are selected for the powder-cored welding wire: 08F steel strip and high-quality heat-resistant steel strip 0Cr19Ni9. The main chemical composition (wt%) of 08F steel strip is: C 0.05-0.11, Si≤0.03, Mn0.25-0.50, Ni≤0.25, Cr<0.10. 08F steel strip has good plastic processing properties and does not require intermediate annealing heat treatment. The main chemical composition (wt%) of high-quality heat-resistant steel strip 0Cr19Ni9 is: C≤0.08, Si≤1.00, Mn≤2.00, Ni8.0-10.50, Cr18.00-20.00. 0Cr19Ni9 steel strip exhibits severe work hardening; when formed using the rolling and drawing process, intermediate annealing is required, while continuous forming is possible using the rolling process.

[0047] 2. Powder core ratio

[0048] The specific ingredient ratios are shown in Table 3. The filling rate of the powder core in the outer shell is 25%.

[0049] The process flow for preparing powder-cored welding wire is as follows: Figure 1 As shown, the specific steps include the following:

[0050] First, the raw materials for preparing the core are mixed evenly, and the outer sheath is rolled into a "U"-shaped outer sheath with a "U"-shaped cross-section. Then, the evenly mixed core material is filled into the "U"-shaped groove of the outer sheath, and the outer sheath with the core material is rolled into a circular cross-section by multi-roll continuous rolling. During the rolling process, the ends of the outer sheath adopt a butt joint form. Finally, through multiple continuous drawing and winding processes, a core welding wire that meets the size requirements is produced. The diameter of the core welding wire is 2mm, and the cross-sectional structure adopts a butt joint form.

[0051] Table 3

[0052]

[0053] Comparative Example 1

[0054] This comparative example provides a powder-cored welding wire, which differs from Example 3 in that WC powder is used instead of an equal amount of Cr3C2 powder. Its preparation method is the same as in Example 3.

[0055] Comparative Example 2

[0056] This comparative example provides a powder-cored welding wire, which differs from Example 6 in that La2O3 powder is used instead of an equal amount of CeO2 powder. Its preparation method is the same as in Example 6.

[0057] Performance tests were conducted on the powder-cored welding wires of Examples 1-6 and Comparative Examples 1-2. A composite coating was fabricated on the surface of the structural material using supersonic arc spraying (spraying parameters: spraying voltage 32V, spraying current 180A, spraying air pressure 0.43MPa, spraying distance 300mm). The composite coating's resistance to room temperature friction and wear, resistance to high-temperature corrosion, and bonding strength were tested using the following methods:

[0058] Resistance to friction and wear at room temperature: Three Ф25mm×20mm specimens were sprayed on each coating, and their end faces were subjected to wear resistance tests on a wear testing machine. The wear medium was 120-mesh abrasive cloth, and the speed of the wear testing machine was 70 r / min. The total wear time was 30 min, and the specimens were weighed every 10 min. The average wear rate (mg / cm³) of each specimen was calculated. 2 (min). The lower the average wear rate, the better the resistance to friction and wear at room temperature.

[0059] High-temperature corrosion resistance: The heating furnace used for hot corrosion testing was a box-type electric furnace. High-temperature hot corrosion tests were conducted on coatings prepared using the powder-cored welding wires of Examples 1-6 and Comparative Examples 1-2. A saturated aqueous solution of Na₂SO₄ + K₂SO₄ with a molar ratio of 7:3 was used in the tests, and the salt film thickness reached 2.0 mg / cm². 2 ~3.0mg / cm 2 The sample was heated and held at 650℃ for a predetermined time, then removed and allowed to cool before being weighed again. It was then coated with salt, dried, weighed, and subjected to corrosion. The corrosion rate (mg / cm³) was calculated. 2 The smaller the corrosion rate (·h), the better the resistance to high-temperature corrosion.

[0060] Bond strength: The bond strength of the coatings was tested using the mating tensile test method on a universal testing machine according to GB 8642. After sandblasting, the specimens were bonded together using TG205 high-strength adhesive, and tensile tests were performed after complete curing. The bond strength value for each coating is the average of 5 data points (MPa).

[0061] The test results are shown in Table 4 below.

[0062] Table 4

[0063]

[0064]

[0065] As shown in Table 4, compared with the base material, the powder-cored welding wire of the present invention has better resistance to room temperature friction and wear, excellent resistance to high temperature corrosion, and high bonding strength, and is relatively inexpensive, making it a novel spraying material worthy of vigorous promotion. Among the six powder-cored welding wires of the present invention, the powder-cored welding wires of Examples 5 and 6 have higher resistance to room temperature friction and wear, higher resistance to high temperature corrosion, and higher bonding strength. Therefore, these powder-cored welding wires are more suitable as anti-corrosion and anti-wear materials for spraying vulnerable parts of thermal power plants. The powder-cored welding wire of Example 6 has strong resistance to room temperature friction and wear, good resistance to high temperature corrosion, and the coating prepared has high bonding strength. This powder-cored welding wire can be recommended as a material for spraying heating surface pipes in thermal power plants. The comparison between Example 3 and Comparative Example 1 shows that replacing Cr3C2 powder with other powders will reduce the coating's resistance to high temperature corrosion and bonding strength. The comparison between Example 6 and Comparative Example 2 shows that replacing CeO2 powder with other powders will reduce the coating's resistance to room temperature friction and wear, resistance to high temperature corrosion, and bonding strength. The powder-cored welding wire of this invention achieves good resistance to room temperature friction and wear, excellent resistance to high temperature corrosion, and high bonding strength through the synergistic effect between the various raw material components, thereby improving the overall performance of the composite coating formed by the powder-cored welding wire.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cerium oxide modified powder-cored welding wire, characterized in that, The powder-cored welding wire includes a powder core and an outer sheath, with the powder core filling the outer sheath; the powder-cored welding wire uses Fe-Al alloy as the matrix phase, Cr3C2 as the reinforcing phase, and also includes CeO2, Ni and Fe2O3.

2. The powder-cored welding wire according to claim 1, characterized in that, The raw materials for preparing the powder core include Cr3C2 powder, Ni powder, Al powder and CeO2 powder.

3. The powder-cored welding wire according to claim 2, characterized in that, The raw materials for preparing the powder core, by weight percentage, include 20-57% Cr3C2 powder, 2-5.8% Ni powder, 10-28.5% Al powder and 3-10% CeO2 powder.

4. The powder-cored welding wire according to claim 3, characterized in that, The raw materials for preparing the powder core also include 0-10% Fe2O3 powder by weight percentage.

5. The powder-cored welding wire according to claim 3, characterized in that, The raw materials for preparing the powder core also include 0-65% Fe powder by weight percentage.

6. The powder-cored welding wire according to any one of claims 1-5, characterized in that, The outer skin is made of carbon steel or stainless steel.

7. The powder-cored welding wire according to claim 6, characterized in that, The outer sheath is selected from 08F carbon steel strip or 0Cr19Ni9 stainless steel strip.

8. The powder-cored welding wire according to claim 1, characterized in that, The diameter of the powder-cored welding wire is 1-3 mm.

9. The powder-cored welding wire according to claim 8, characterized in that, The diameter of the powder-cored welding wire is 2mm.

10. The powder-cored welding wire according to claim 1, characterized in that, The powder core has a filling rate of 20-30% in the outer skin.

11. The powder-cored welding wire according to claim 10, characterized in that, The powder core has a filling rate of 25% in the outer skin.

12. The method for preparing the powder-cored welding wire according to any one of claims 1-11, characterized in that, Includes the following steps: First, the raw materials for preparing the core are mixed evenly, and the outer sheath is rolled into a "U"-shaped outer sheath with a "U"-shaped cross section. Then, the evenly mixed core raw materials are filled into the "U"-shaped groove of the outer sheath, and the outer sheath with the core raw materials is rolled into a circular cross section by multi-roll continuous rolling. During the rolling process, the ends of the outer sheath adopt a butt joint form. Finally, the core welding wire that meets the size requirements is produced through multiple continuous drawing and winding processes.

13. The application of the powder-cored welding wire according to any one of claims 1-11, characterized in that, It is used as a coating on structural components.

14. The application of the powder-cored welding wire according to claim 13, characterized in that, The coating is formed by spraying the powder-cored welding wire onto the surface of the structural component using a supersonic arc spraying method.

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