Material and method for double-gradient low-stress wear-resistant corrosion-resistant surfacing layer for water-cooled wall

Abstract

The invention discloses a material for a double-gradient low-stress wear-resistant corrosion-resistant surfacing layer for a water-cooled wall. The material comprises a water-cooled wall metallurgical bonding layer welding wire for surfacing on the surface of the water-cooled wall and a water-cooled wall high-temperature-resistant erosion-resistant layer welding wire for surfacing on the surface of the metallurgical bonding layer. A surfacing layer prepared from the material is high in metallurgical bonding strength with a water-cooled wall base body on one hand, and is excellent in high-temperature corrosion resistance on the other hand, a water-cooled wall tube can be effectively protected, and a tube explosion accident of the water-cooled wall under high-temperature erosion is avoided. The invention further discloses a preparation method of the material for the double-gradient low-stress wear-resistant corrosion-resistant surfacing layer for the water cooling wall.

Description

Technical Field

[0001] This invention belongs to the field of metal materials technology, specifically relating to materials for a double-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls, and also to a method for preparing such materials. Background Technology

[0002] As coal-fired power generating units develop towards higher parameters and larger capacities, the working environment of boiler water-cooled walls is becoming increasingly harsh. During operation, the heated surfaces of the water-cooled walls not only endure the intense heat radiation from the high-temperature flames inside the furnace, but also face high-speed erosion and wear from the large amount of fly ash particles generated by pulverized coal combustion. Especially when burning low-calorific-value, high-ash, inferior coal, the fly ash concentration is higher and the particles are harder, causing the water-cooled wall tubes to thin rapidly due to erosion, becoming one of the key factors limiting their service life. At the same time, sulfur in the coal undergoes complex sulfidation reactions with the tube wall metal at high temperatures, causing high-temperature sulfur corrosion, further accelerating the material failure process. The interaction between erosion and high-temperature corrosion makes the protection of water-cooled walls extremely serious, directly affecting the safe and economical operation of the boiler.

[0003] To address the aforementioned issues, the industry commonly employs surface protection technology to extend the service life of water-cooled walls. Among these, surfacing technology is widely used due to its ability to form a cladding layer that is metallurgically bonded to the substrate, offering advantages such as high bonding strength and good impact resistance. However, traditional surfacing material design often focuses on improving a single property, such as increasing the content of alloying elements to enhance the hardness or corrosion resistance of the surfacing layer. But under actual service conditions, the surfacing layer of water-cooled walls faces dual performance requirements, both internal and external: on the one hand, the surfacing layer needs to achieve a good metallurgical bond with the substrate (water-cooled wall tubes, typically low-carbon steel or low-alloy steel), and the portion near the substrate must possess a certain degree of ductility and toughness to buffer thermal and mechanical stresses and prevent interface cracking or peeling; on the other hand, the surface of the surfacing layer is directly exposed to high-temperature flames and corrosive fumes, requiring extremely high red hardness, wear resistance, and corrosion resistance. This significant difference in internal and external performance requirements makes it difficult for a single homogeneous surfacing layer to simultaneously meet these requirements.

[0004] In recent years, although some studies have attempted to optimize performance through multi-layer welding or adjusting alloy composition, some shortcomings still exist. For example, while a simple high-alloy weld overlay exhibits excellent surface performance, the significant difference in thermophysical properties (such as the coefficient of linear expansion) between it and the substrate can easily lead to large residual stresses at the interface, resulting in decreased bonding performance or even weld overlay peeling. On the other hand, transition layers that overemphasize bonding with the substrate often fail to achieve the expected wear and corrosion resistance. Therefore, how to balance the bonding performance between the weld overlay and the substrate with the surface performance, achieving a balance between the two, has become a pressing technical challenge in this field. Summary of the Invention

[0005] The first objective of this invention is to provide a material for a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls. The weld overlay prepared from this material has high metallurgical bonding strength with the water-cooled wall substrate and excellent high-temperature corrosion resistance, which can effectively protect the water-cooled wall tubes and prevent tube rupture accidents under high-temperature erosion of the water-cooled wall.

[0006] The second objective of this invention is to provide a method for preparing a material for a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls.

[0007] The first technical solution adopted in this invention is a material for a dual-gradient low-stress wear-resistant and corrosion-resistant overlay layer for water-cooled walls, comprising a water-cooled wall metallurgical bonding layer welding wire for overlaying on the surface of the water-cooled wall and a water-cooled wall high-temperature erosion-resistant layer welding wire for overlaying on the surface of the metallurgical bonding layer.

[0008] The invention is further characterized in that:

[0009] The welding wire for the metallurgical bonding layer of water-cooled walls includes flux powder and welding skin. The flux powder comprises the following components by mass percentage: Fe 70.0~80.0%, Cr 8.0~10.0%, Nb 1.0~3.0%, Mo 1.0~2.0%, Co 1.0~2.0%, Y2O3 1.0~2.0%, and the remainder Ni. The sum of the mass percentages of the above components is 100%. The high-temperature erosion resistant welding wire for water-cooled walls comprises flux powder and welding skin. The flux powder contains the following components by mass percentage: Cr 40.0~50.0%, Nb 25.0~30.0%, Al 3.0~5.0%, Mo 3.0~5.0%, Co 1.0~2.0%, C 1.0~2.0%, Y2O3 0.5~1.0%, and the remainder is Ni. The sum of the mass percentages of the above components is 100%.

[0010] The purity of each raw material component powder in the metallurgical bonding layer welding wire of the water-cooled wall and the high-temperature erosion resistant layer welding wire of the water-cooled wall is ≥99.9%.

[0011] The particle size of each raw material component powder in the metallurgical bonding layer welding wire of the water-cooled wall and the high-temperature erosion resistant layer welding wire of the water-cooled wall is 100 mesh to 200 mesh.

[0012] The welding wires used for the metallurgical bonding layer of the water-cooled wall and the high-temperature erosion resistant layer of the water-cooled wall are both Inconel 625 strips, with a thickness of 0.4 mm and a width of 7 mm.

[0013] The filling rate of the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall are both controlled at 22wt%~25wt%.

[0014] The preparation method of the welding wire for the metallurgical bonding layer of the water-cooled wall is as follows: Step 1: Weigh out the following components by mass percentage: Fe 70.0~80.0%, Cr 8.0~10.0%, Nb 1.0~3.0%, Mo 1.0~2.0%, Co 1.0~2.0%, Y2O3 1.0~2.0%, with the remainder being Ni. The sum of the mass percentages of the above components should be 100%. Step 2: Place the weighed powder from Step 1 into a vacuum heating furnace and heat it at a temperature of 220℃~260℃ for 1h~3h to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 1h~3h. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced one by one to finally obtain a flux-cored wire with a diameter of 1.2mm; Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0015] The preparation method of the high-temperature erosion resistant welding wire for water-cooled walls, with the following specific steps: Step 1: Weigh out the following components by mass percentage: Cr 40.0~50.0%, Nb 25.0~30.0%, Al 3.0~5.0%, Mo 3.0~5.0%, Co 1.0~2.0%, C 1.0~2.0%, Y2O3 0.5~1.0%, with the remainder being Ni. The sum of the mass percentages of the above components should be 100%. Step 2: Place the weighed medicinal powder from Step 1 into a vacuum heating furnace and heat it at a temperature of 240℃~280℃ for 2h~4h to remove the water of crystallization from the medicinal powder; place the dried medicinal powder into a powder mixer for thorough mixing for 2h~4h. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced one by one to finally obtain a flux-cored wire with a diameter of 1.2mm; Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0016] The second technical solution adopted in this invention is a method for preparing a double-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls. The method uses the aforementioned material for the double-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls to prepare the gradient weld overlay. Specifically, the method involves: First, using a water-cooled wall metallurgical bonding layer welding wire, weld overlay is directly applied to the surface of the water-cooled wall. The welding is performed using a CMT power supply with a welding current of 120A~160A, and the weld overlay thickness is 1.5mm~2.0mm. Second, using a water-cooled wall high-temperature erosion-resistant layer welding wire, weld overlay is applied to the surface of the metallurgical bonding layer obtained in the first step. The welding is performed using a CMT power supply with a welding current of 160A~250A, and the weld overlay thickness is 1.5mm~2.0mm.

[0017] The beneficial effects of this invention are: (1) The gradient weld overlay of the present invention ensures both excellent metallurgical bonding performance with the water-cooled wall substrate and excellent high-temperature erosion resistance. Because the water-cooled wall metallurgical bonding layer is used as the gradient transition layer, the stress of the final weld overlay is low.

[0018] (2) The welding wire for the metallurgical bonding layer of the water-cooled wall of the present invention is designed with Fe, Ni and Cr alloying elements as the main components, which ensures excellent metallurgical bonding strength with the water-cooled wall substrate.

[0019] (3) The high-temperature erosion resistant welding wire for water-cooled walls of the present invention is designed with Cr, Al and Nb alloying elements as the main components, which ensures the excellent high-temperature erosion resistance of the water-cooled walls in the furnace.

[0020] (4) This invention proposes a dual-gradient overlay design, aiming to optimize the surface layer from the inside out through a gradient transition in composition and performance. This ensures excellent metallurgical bonding with the substrate and low residual stress, while providing superior resistance to high-temperature erosion and corrosion, thus offering a more long-lasting and reliable protection solution for water-cooled walls. The welding wire material of this invention can be welded using either MIG or TIG power sources, making it widely applicable and highly valuable for wider application. Attached Figure Description

[0021] Figure 1 The microstructure of the weld overlay layer is obtained by using the welding wire for the metallurgical bonding layer of the water-cooled wall prepared in Example 2 to perform weld overlay on the surface of the water-cooled wall pipe. Figure 2 The microstructure of the weld overlay layer is obtained by using the high-temperature erosion resistant welding wire for water-cooled wall prepared in Example 2 to perform weld overlay welding on the metallurgical bonding layer surface of water-cooled wall pipe. Figure 3The morphology of the resulting weld overlay layer was obtained by welding the material for the dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer prepared in Example 2 onto the surface of the water-cooled wall under high-temperature erosion conditions of 700°C for 5 minutes. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] The present invention provides a material for a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls, including a water-cooled wall metallurgical bonding layer welding wire for weld overlay on the surface of the water-cooled wall and a water-cooled wall high-temperature erosion-resistant layer welding wire for weld overlay on the surface of the metallurgical bonding layer.

[0024] The welding wire for the metallurgical bonding layer of water-cooled walls includes flux powder and welding skin. The flux powder comprises the following components by mass percentage: Fe 70.0~80.0%, Cr 8.0~10.0%, Nb 1.0~3.0%, Mo 1.0~2.0%, Co 1.0~2.0%, Y2O3 1.0~2.0%, and the remainder Ni. The sum of the mass percentages of the above components is 100%. The high-temperature erosion resistant welding wire for water-cooled walls comprises flux powder and welding skin. The flux powder contains the following components by mass percentage: Cr 40.0~50.0%, Nb 25.0~30.0%, Al 3.0~5.0%, Mo 3.0~5.0%, Co 1.0~2.0%, C 1.0~2.0%, Y2O3 0.5~1.0%, and the remainder is Ni. The sum of the mass percentages of the above components is 100%.

[0025] The purity of each raw material component powder in the welding wire for the metallurgical bonding layer of water-cooled walls and the welding wire for the high-temperature erosion resistant layer of water-cooled walls is ≥99.9%.

[0026] The particle size of each raw material component powder in the welding wire for the metallurgical bonding layer of water-cooled walls and the welding wire for the high-temperature erosion resistant layer of water-cooled walls is 100 mesh to 200 mesh.

[0027] The welding wires used for the metallurgical bonding layer of the water-cooled wall and the high-temperature erosion resistant layer of the water-cooled wall are both Inconel 625 strips, with a thickness of 0.4 mm and a width of 7 mm.

[0028] The filling rate of the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall are both controlled at 22wt%~25wt%.

[0029] The present invention relates to a material for a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls, comprising a metallurgical bonding layer welding wire for water-cooled walls and a high-temperature erosion-resistant layer welding wire. The roles of each raw material powder element in the metallurgical bonding layer welding wire are as follows: (1) Fe element: As the matrix element and main component in this welding wire powder, Fe's primary role is to achieve high compositional compatibility with the water-cooled wall substrate (usually low-carbon steel or low-alloy steel). Since the substrate itself is mainly Fe, a high Fe content can significantly reduce the difference in chemical composition between the weld metal and the base material, thereby promoting good metallurgical bonding during the welding process and reducing interface defects caused by abrupt changes in composition. At the same time, the addition of Fe can effectively regulate the thermophysical parameters of the weld layer, making its coefficient of linear expansion closer to that of the substrate, which is crucial for reducing the residual stress generated during the cooling process of the weld layer. In addition, the Fe-based solid solution structure has good plasticity and toughness, and can buffer and release thermal stress through micro-deformation, thereby improving the crack resistance and compatibility with the substrate of the entire bonding layer.

[0030] (2) Cr element: In this metallurgical bonding layer, Cr mainly enhances the strength of the weld metal through solid solution strengthening while maintaining good toughness, avoiding increased brittleness due to excessive strength. An appropriate amount of Cr can provide necessary mechanical support for the bonding layer while ensuring ductility and toughness, preventing deformation and cracking during subsequent surface welding or service. In addition, the addition of Cr helps to purify grain boundaries, combining with impurity elements to form compounds, reducing the formation of brittle phases at grain boundaries, thereby improving the quality of interfacial bonding. Cr can also improve the oxidation resistance of the bonding layer to a certain extent, preventing excessive oxidation of the bonding layer surface during multi-layer welding, which would affect the fusion effect with the surface layer.

[0031] (3) Nb: Nb is a powerful element for refining grains and controlling precipitates. In the metallurgical bonding layer, trace amounts of Nb can form carbides such as NbC during solidification. These fine particles can pin grain boundaries, significantly refining the solidification structure of the weld metal. Grain refinement is an effective means to simultaneously improve the strength and toughness of materials. Fine grain structure can not only improve the mechanical properties of the bonding layer, but also hinder crack propagation by increasing the grain boundary area, thereby improving crack resistance. At the same time, the refined structure helps to evenly distribute residual stress and avoid stress concentration. The addition of Nb can also improve the fluidity of the molten pool, making the weld layer more uniform in shape, reducing bonding defects such as slag inclusions and porosity, and indirectly improving the metallurgical bonding strength with the water-cooled wall.

[0032] (4) Mo: Mo is a key element for improving the high-temperature performance and toughness of the weld overlay. In the bonding layer, Mo mainly strengthens the matrix through solid solution, increasing the strength of the weld metal without significantly reducing its plasticity. More importantly, Mo can reduce the temper brittleness tendency of steel and improve the thermal fatigue resistance of the weld overlay. Under the thermal cycling of multi-layer, multi-pass weld overlay or subsequent surface weld overlay, Mo can ensure the stability of the bonding layer structure, avoid grain coarsening or performance degradation due to heat input, and thus maintain the stability of the interfacial bonding strength. In addition, Mo can also improve the toughness of the weld metal, especially the low-temperature toughness, which is very beneficial for alleviating the stress concentration generated during the cooling and shrinkage of the weld overlay.

[0033] (5) Co element: Co mainly plays a role in solid solution strengthening and optimizing microstructure in this welding wire. Co is dissolved in the matrix, which can improve the strength and recrystallization temperature of the matrix, so that the bonding layer can maintain the stability of the structure under the heat of subsequent welding and avoid performance degradation due to heat. Co can also reduce the stacking fault energy of the weld overlay and promote the generation of more slip systems during deformation, thereby improving the work hardening ability and toughness of the weld metal. This good combination of toughness and strength allows the bonding layer to better buffer and absorb the thermal stress caused by temperature difference, reduce stress concentration at the interface, and thus ensure a strong bond between the bonding layer and the substrate, as well as between the bonding layer and the surface layer.

[0034] (6) Y2O3: As a rare earth oxide, Y2O3 plays a unique role in microalloying and oxide metallurgy in this welding wire. First, Y2O3 can refine grains at high temperatures. By providing heterogeneous nucleation sites during solidification, it promotes the formation of equiaxed crystals and inhibits the excessive growth of columnar crystals, thereby obtaining a uniform and fine microstructure, which is crucial for improving the strength and toughness of the bonding layer. Second, the dispersed Y2O3 particles can pin dislocations and grain boundaries, improve the high-temperature strength and microstructure stability of the weld overlay, and ensure that the bonding layer does not soften or coarsen under the thermal cycling of subsequent surface welding. In addition, rare earth elements have a purifying effect and can combine with impurity elements (such as S, P, O, etc.) in the molten pool, reducing grain boundary segregation and the formation of brittle phases, significantly improving the bonding strength and cleanliness of the interface, thereby reducing the tendency to generate cracks and ensuring the reliability of the metallurgical bond.

[0035] (7) Ni element: Ni is an important alloying element in the welding wire of this bonding layer, and it is also the element with the highest content. The primary role of Ni is to improve the toughness and plasticity of the weld metal, especially to significantly reduce the brittle transition temperature, so that the bonding layer can maintain good crack resistance during complex welding thermal cycles and cooling processes. Ni is infinitely miscible with Fe, which can stabilize the austenitic structure and form a Fe-Ni solid solution with a face-centered cubic structure. This structure has excellent plasticity and toughness and a low yield ratio, and can effectively release residual stress through plastic deformation. At the same time, the addition of Ni can optimize the wettability between the weld layer and the substrate, promote the spread of molten metal on the substrate surface, improve the fusion quality, and thus enhance the metallurgical bonding strength. In addition, Ni can also increase the electrode potential of the matrix, which can enhance the corrosion resistance of the bonding layer to a certain extent and avoid preferential corrosion at the interface.

[0036] The roles of each element in the raw material powder in the high-temperature erosion resistant welding wire for water-cooled walls are as follows: (1) Cr element: Cr is the absolute main element and skeleton element of this high-temperature erosion resistant layer. Its high content of 40-50% is the core of the excellent high-temperature erosion resistance of the weld overlay layer. The high Cr content can quickly form a dense, continuous Cr2O3 oxide film with self-healing ability at high temperature. This oxide film can effectively isolate the high-temperature corrosive gases (such as sulfides, chlorides, etc.) in the furnace, and significantly improve the resistance to high-temperature oxidation and hot corrosion. At the same time, Cr is a strong carbide forming element and can combine with C to form high-hardness M7C3 type carbides. These carbides are uniformly distributed in the matrix as hard phases, forming a wear-resistant skeleton that resists fly ash cutting and directly improves the resistance to mechanical erosion. In terms of gradient bonding, the extremely high Cr content in this layer and the 8-10% Cr content in the metallurgical bonding layer form a reasonable composition gradient, avoiding the interface stress concentration caused by abrupt composition changes, while ensuring good metallurgical compatibility between layers.

[0037] (2) Nb element: Nb is a key element in this welding wire to improve its resistance to erosion and wear, with a content as high as 25-30%. Nb is a strong carbide-forming element, and during solidification, it preferentially combines with C to form high-melting-point, high-hardness NbC particles. These NbC particles are dispersed in the matrix, and as a primary hard phase, they significantly improve the macroscopic hardness and abrasive wear resistance of the weld overlay, effectively resisting the high-speed cutting of fly ash. NbC has excellent high-temperature stability and is not easily decomposed or coarsened in the high-temperature environment of the boiler, ensuring that the weld overlay maintains high red hardness for a long time. In addition, the addition of Nb can significantly refine the solidification structure, inhibit grain growth by pinning grain boundaries, form a fine-grained strengthening effect, and further improve the strength and toughness of the material. In terms of the transition with the bonding layer, the reasonable design of the Nb content allows the layer to smoothly connect with the Nb element in the bonding layer, avoiding large fluctuations in certain elements, which is conducive to forming a defect-free metallurgical bonding interface.

[0038] (3) Al element: Al is an important auxiliary element in this welding wire to improve its high-temperature oxidation and corrosion resistance. Under high-temperature service environment, Al can further form an Al2O3 protective layer near the oxide film / metal interface on the basis of the Cr2O3 oxide film. Al2O3 has extremely high thermodynamic stability and density, which can significantly enhance the barrier effect of the oxide film and effectively inhibit the diffusion of corrosive media such as sulfur and oxygen into the weld overlay, thereby greatly improving the resistance to high-temperature sulfide corrosion. The addition of Al can also form intermetallic compound strengthening phases with elements such as Ni and Fe in the matrix, thereby improving the high-temperature strength of the matrix through dispersion strengthening. In terms of interlayer bonding, the Al content is controlled at a moderate level of 3~5%, which can ensure the excellent oxidation resistance of the surface layer, and avoid the increase of brittleness of the cladding layer or the formation of low-melting-point eutectic phase with the bonding layer due to excessive Al content, thus ensuring the high quality of interlayer bonding.

[0039] (4) Mo element: Mo in this welding wire significantly improves the high-temperature strength and red hardness of the weld overlay through solid solution strengthening. Mo atoms are dissolved in the matrix, causing lattice distortion and hindering dislocation movement, thereby improving the material's resistance to deformation at high temperatures. This allows the material to maintain structural stability when subjected to high-speed fly ash impacts and resist plastic deformation and micro-cutting during erosion. Mo can also improve the matrix's resistance to tempering softening, ensuring that the weld overlay maintains high hardness during long-term high-temperature service. In addition, Mo has a certain anti-corrosion effect in sulfur-containing atmospheres, which can improve the material's resistance to high-temperature creep. Regarding the connection with the bonding layer, the content of Mo in this layer (3~5%) is slightly higher than that in the bonding layer (1~2%), forming a reasonable gradient increase, which not only ensures the continuity of the interlayer composition but also meets the higher requirements of the surface layer for high-temperature strength.

[0040] (5) Co element: Co mainly plays a role in strengthening the high-temperature performance of the matrix and optimizing the microstructure in this welding wire. Co is dissolved in Ni-based solid solution, which can reduce the stacking fault energy of the weld overlay and promote the generation of more slip systems during deformation, thereby improving the high-temperature toughness and thermal fatigue resistance of the weld overlay metal. Under the condition of repeated impact from fly ash, good high-temperature toughness helps to absorb impact energy and delay the initiation and propagation of microcracks. Co can also increase the recrystallization temperature and high-temperature strength of the matrix, ensuring the stability of the structure and the durability of the weld overlay in the high-temperature environment of the furnace. In terms of gradient design, the content of Co in this layer (1~2%) is completely consistent with the content in the bonding layer. This continuity of composition is conducive to forming a smooth transition between the two layers and avoids the structural differences and stress concentration caused by abrupt changes in composition.

[0041] (6) Carbon (C): Carbon is an indispensable element for the formation of a hard, wear-resistant phase in this welding wire. C combines with strong carbide-forming elements such as Nb and Cr to generate high-hardness NbC and Cr carbides in situ. These carbides constitute the main wear-resistant skeleton resisting fly ash erosion. The type, quantity, size, and distribution of carbides directly determine the macroscopic wear resistance of the weld overlay. Controlling the C content within a reasonable range of 1-2% aims to optimize carbide precipitation behavior: ensuring sufficient hard phase to form a wear-resistant skeleton while avoiding excessive carbides that could lead to matrix embrittlement or the precipitation of continuous network carbides along grain boundaries, thus achieving a balance between high hardness and good toughness. This toughness is crucial for resisting repeated impacts from fly ash and can prevent brittle spalling during the erosion process.

[0042] (7) Y2O3 element: As a rare earth oxide, Y2O3 plays a unique role in microalloying and purification strengthening in this welding wire. First, during solidification, Y2O3 can act as a heterogeneous nucleation core, significantly refining grains, promoting the formation of equiaxed crystals, and inhibiting the growth of coarse columnar crystals, thereby obtaining a uniform and fine structure, which is very beneficial to improving the strength, toughness, and wear resistance of the weld overlay. Second, Y2O3 has the function of purifying grain boundaries, and can combine with impurity elements (such as S, P, O, etc.) in the molten pool, reducing grain boundary segregation and the formation of low-melting-point eutectic phases, improving the cleanliness and strength of the interlayer bonding interface, and ensuring a high-quality connection between the high-temperature erosion resistant layer and the metallurgical bonding layer. In addition, the dispersed Y2O3 particles can pin dislocations, improve the high-temperature creep strength of the weld overlay and the adhesion of the oxide film, making the oxide film less likely to peel off under fly ash impact, thus maintaining a long-term protective effect.

[0043] (8) Ni element: Ni, as the balance and matrix element of this welding wire, mainly plays the role of binder and matrix carrier. Ni has good high-temperature plasticity and toughness, and can serve as a tough matrix to contain and support hard phases such as NbC and carbides, forming an ideal wear-resistant structure of "wear-resistant hard phase and energy-absorbing matrix", which not only ensures high hardness, but also provides the necessary impact toughness. Ni can also stabilize the austenitic structure to form a solid solution with a face-centered cubic structure. This structure has excellent high-temperature strength and thermal fatigue resistance. In terms of gradient bonding, Ni is the matrix element that runs through the entire double-layer welding wire system. From the bonding layer to the high-temperature erosion resistant layer, Ni always exists as the main matrix. This continuity of composition is the key guarantee for ensuring high-quality metallurgical bonding between the two layers and eliminating interface defects.

[0044] The preparation method of the welding wire for the metallurgical bonding layer of the water-cooled wall is as follows: Step 1: Weigh out the following components by mass percentage: Fe 70.0~80.0%, Cr 8.0~10.0%, Nb 1.0~3.0%, Mo 1.0~2.0%, Co 1.0~2.0%, Y2O3 1.0~2.0%, with the remainder being Ni. The sum of the mass percentages of the above components should be 100%. Step 2: Place the weighed powder from Step 1 into a vacuum heating furnace and heat it at a temperature of 220℃~260℃ for 1h~3h to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 1h~3h. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced one by one to finally obtain a flux-cored wire with a diameter of 1.2mm; Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0045] The preparation method of the high-temperature erosion resistant welding wire for water-cooled walls, with the following specific steps: Step 1: Weigh out the following components by mass percentage: Cr 40.0~50.0%, Nb 25.0~30.0%, Al 3.0~5.0%, Mo 3.0~5.0%, Co 1.0~2.0%, C 1.0~2.0%, Y2O3 0.5~1.0%, with the remainder being Ni. The sum of the mass percentages of the above components should be 100%. Step 2: Place the weighed medicinal powder from Step 1 into a vacuum heating furnace and heat it at a temperature of 240℃~280℃ for 2h~4h to remove the water of crystallization from the medicinal powder; place the dried medicinal powder into a powder mixer for thorough mixing for 2h~4h. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced one by one to finally obtain a flux-cored wire with a diameter of 1.2mm; Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0046] This invention also provides a method for preparing a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls. The method uses the aforementioned material for the dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls to prepare the gradient weld overlay. Specifically, the method involves: First, using a water-cooled wall metallurgical bonding layer welding wire to directly weld over the surface of the water-cooled wall. The welding is performed using a CMT power supply with a welding current of 120A~160A, and the weld overlay thickness is 1.5mm~2.0mm. Second, using a water-cooled wall high-temperature erosion-resistant layer welding wire to weld over the surface of the metallurgical bonding layer obtained in the first step. The welding is performed using a CMT power supply with a welding current of 160A~250A, and the weld overlay thickness is 1.5mm~2.0mm.

[0047] Example 1 The preparation method of the welding wire for the metallurgical bonding layer of the water-cooled wall is as follows: Step 1: Weigh out the following components by mass percentage: Fe 70.0%, Cr 8.0%, Nb 1.0%, Mo 1.0%, Co 1.0%, Y2O3 1.0%, and the remainder Ni. The sum of the mass percentages of the above components is 100%.

[0048] Step 2: Place the powder weighed in Step 1 into a vacuum heating furnace and heat it at 220℃ for 1 hour to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 1 hour. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced one by one to finally obtain a flux-cored wire with a diameter of 1.2mm; Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0049] The preparation method of the high-temperature erosion resistant welding wire for water-cooled walls, with the following specific steps: Step 1: Weigh out the following components by mass percentage: 40.0% Cr, 25.0% Nb, 3.0% Al, 3.0% Mo, 1.0% Co, 1.0% C, 0.5% Y2O3, and the remainder Ni. The sum of the mass percentages of the above components is 100%.

[0050] Step 2: Place the powder weighed in Step 1 into a vacuum heating furnace and heat it at 240℃ for 2 hours to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 2 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0051] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0052] The purity of each raw material component powder in the welding wire for the metallurgical bonding layer of water-cooled walls and the welding wire for the high-temperature erosion resistant layer of water-cooled walls is ≥99.9%.

[0053] The particle size of each raw material component powder in the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall is 100 mesh.

[0054] The welding wires used for the metallurgical bonding layer of the water-cooled wall and the high-temperature erosion resistant layer of the water-cooled wall are both Inconel 625 strips, with a thickness of 0.4 mm and a width of 7 mm.

[0055] The filling rate of the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall are both controlled at 22wt%.

[0056] A method for preparing a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls is disclosed. The material used in Example 1 is employed to prepare the gradient weld overlay. The preparation method is as follows: First, a metallurgical bonding layer welding wire is used to directly weld over the surface of the water-cooled wall. A CMT power supply is used for the weld overlay, with a welding current of 120A and a weld overlay thickness of 1.5mm. Second, a high-temperature erosion resistant layer welding wire is used to weld over the surface of the metallurgical bonding layer. A CMT power supply is used for the weld overlay, with a welding current of 160A and a weld overlay thickness of 1.5mm.

[0057] The above-mentioned gradient weld overlay was subjected to residual stress testing, Brinell hardness testing, and high-temperature corrosion testing. The results are as follows: (1) The residual stress of the obtained weld overlay is 360 MPa, which is lower than the yield strength of the material and the stress value is low.

[0058] (2) The hardness of the obtained weld overlay is 54HRC, which is relatively high.

[0059] (3) The obtained weld overlay was subjected to a high-temperature corrosion test of sulfate (75wt%NaSO4+25wt%NaCl) at 650℃. After corrosion for 120h, the surface corrosion products were removed and the weight was weighed. The results showed that the weight loss of the weld overlay was 1.25g and the weight loss of the water-cooled wall substrate (the base material without weld overlay treatment) was 12.9g.

[0060] In summary, the gradient weld overlay of the present invention has low stress, high hardness, and excellent high-temperature corrosion resistance.

[0061] Example 2 The preparation method of the welding wire for the metallurgical bonding layer of the water-cooled wall is as follows: Step 1: Weigh out the following components by mass percentage: Fe 80.0%, Cr 10.0%, Nb 3.0%, Mo 2.0%, Co 2.0%, Y2O3 2.0%, and the remainder Ni. The sum of the mass percentages of the above components is 100%.

[0062] Step 2: Place the weighed powder from Step 1 into a vacuum heating furnace and heat it at 260℃ for 3 hours to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 3 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0063] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0064] The preparation method of the high-temperature erosion resistant welding wire for water-cooled walls, with the following specific steps: Step 1: Weigh out the following components by mass percentage: Cr 50.0%, Nb 30.0%, Al 5.0%, Mo 5.0%, Co 2.0%, C 2.0%, Y2O3 1.0%, and the remainder Ni. The sum of the mass percentages of the above components is 100%.

[0065] Step 2: Place the weighed powder from Step 1 into a vacuum heating furnace and heat it at 280℃ for 4 hours to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 4 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0066] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0067] The purity of each raw material component powder in the welding wire for the metallurgical bonding layer of water-cooled walls and the welding wire for the high-temperature erosion resistant layer of water-cooled walls is ≥99.9%.

[0068] The particle size of each raw material component powder in the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall is 200 mesh.

[0069] The welding wires used for the metallurgical bonding layer of the water-cooled wall and the high-temperature erosion resistant layer of the water-cooled wall are both Inconel 625 strips, with a thickness of 0.4 mm and a width of 7 mm.

[0070] The filling rate of the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall are both controlled at 25wt%.

[0071] A method for preparing a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls is described. The material used in Example 2 is employed to prepare the gradient weld overlay. The preparation method is as follows: First, a metallurgical bonding layer welding wire is used to directly weld over the surface of the water-cooled wall. A CMT power supply is used for the weld overlay, with a welding current of 160A and a weld overlay thickness of 2.0mm. Second, a high-temperature erosion resistant layer welding wire is used to weld over the surface of the metallurgical bonding layer. A CMT power supply is used for the weld overlay, with a welding current of 250A and a weld overlay thickness of 2.0mm.

[0072] The above-mentioned gradient weld overlay was subjected to residual stress testing, Brinell hardness testing, and high-temperature corrosion testing. The results are as follows: (1) The residual stress of the obtained weld overlay is 362 MPa, which is lower than the yield strength of the material and the stress value is low.

[0073] (2) The hardness of the obtained weld overlay is 55HRC, which is relatively high.

[0074] (3) The obtained weld overlay was subjected to a high-temperature corrosion test of sulfate (75wt%NaSO4+25wt%NaCl) at 650℃. After corrosion for 120h, the surface corrosion products were removed and the weight was weighed. The results showed that the weight loss of the weld overlay was 1.26g and the weight loss of the water-cooled wall substrate (the base material without weld overlay treatment) was 12.9g.

[0075] In summary, the gradient weld overlay of the present invention has low stress, high hardness, and excellent high-temperature corrosion resistance.

[0076] Figure 1 The microstructure of the weld overlay layer was obtained by depositing the metallurgical bonding layer welding wire prepared in Example 2 onto the surface of a water-cooled wall pipe. As can be seen from the figure, the metallurgical bonding layer structure is mainly composed of columnar dendrites, which are well bonded to the water-cooled wall matrix, and no defects such as pores or cracks were observed.

[0077] Figure 2 The high-temperature erosion resistant welding wire prepared in Example 2 was used to deposit welds onto the metallurgical bonding layer surface of the water-cooled wall pipe. The resulting weld overlay microstructure is shown in the figure. As can be seen from the figure, the high-temperature erosion layer microstructure is mainly composed of columnar numerical crystals, with a dense structure and no defects such as pores or cracks observed.

[0078] Figure 3 The image shows the morphology of the weld overlay material prepared in Example 2 for a water-cooled wall, after being welded onto the surface of the water-cooled wall under high-temperature erosion conditions of 700°C for 5 minutes. As can be seen from the figure, the weld overlay exhibits minimal surface weight loss due to erosion.

[0079] Example 3 The preparation method of the welding wire for the metallurgical bonding layer of the water-cooled wall is as follows: Step 1: Weigh out the following components by mass percentage: Fe 75.0%, Cr 9.0%, Nb 2.0%, Mo 1.5%, Co 1.5%, Y2O3 1.5%, and the remainder Ni. The sum of the mass percentages of the above components is 100%.

[0080] Step 2: Place the powder weighed in Step 1 into a vacuum heating furnace and heat it at 240℃ for 2 hours to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 2 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0081] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0082] The preparation method of the high-temperature erosion resistant welding wire for water-cooled walls, with the following specific steps: Step 1: Weigh out the following components by mass percentage: 45.0% Cr, 27.5% Nb, 4.0% Al, 4.0% Mo, 1.5% Co, 1.5% C, 0.75% Y2O3, and the remainder Ni. The sum of the mass percentages of the above components is 100%.

[0083] Step 2: Place the weighed powder from Step 1 into a vacuum heating furnace and heat it at 260℃ for 3 hours to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 3 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0084] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0085] The purity of each raw material component powder in the welding wire for the metallurgical bonding layer of water-cooled walls and the welding wire for the high-temperature erosion resistant layer of water-cooled walls is ≥99.9%.

[0086] The particle size of each raw material component powder in the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall is 200 mesh.

[0087] The welding wires used for the metallurgical bonding layer of the water-cooled wall and the high-temperature erosion resistant layer of the water-cooled wall are both Inconel 625 strips, with a thickness of 0.4 mm and a width of 7 mm.

[0088] The filling rate of the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall are both controlled at 23wt%.

[0089] A method for preparing a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls is described. The material used in Example 3 is employed to prepare the gradient weld overlay. The preparation method is as follows: First, a metallurgical bonding layer welding wire is used to directly weld over the surface of the water-cooled wall. A CMT power supply is used for the weld overlay, with a welding current of 140A and a weld overlay thickness of 1.75mm. Second, a high-temperature erosion resistant layer welding wire is used to weld over the surface of the metallurgical bonding layer. A CMT power supply is used for the weld overlay, with a welding current of 215A and a weld overlay thickness of 1.75mm.

[0090] The above-mentioned gradient weld overlay was subjected to residual stress testing, Brinell hardness testing, and high-temperature corrosion testing. The results are as follows: (1) The residual stress of the obtained weld overlay is 366 MPa, which is lower than the yield strength of the material and the stress value is low.

[0091] (2) The hardness of the obtained weld overlay is 56HRC, which is relatively high.

[0092] (3) The obtained weld overlay was subjected to a high-temperature corrosion test of sulfate (75wt%NaSO4+25wt%NaCl) at 650℃. After corrosion for 120h, the surface corrosion products were removed and the weight was weighed. The results showed that the weight loss of the weld overlay was 1.29g and the weight loss of the water-cooled wall substrate (the base material without weld overlay treatment) was 12.9g.

[0093] In summary, the gradient weld overlay of the present invention has low stress, high hardness, and excellent high-temperature corrosion resistance.

[0094] Example 4 The preparation method of the welding wire for the metallurgical bonding layer of the water-cooled wall is as follows: Step 1: Weigh out the following components by mass percentage: Fe 71.0%, Cr 8.1%, Nb 1.1%, Mo 1.2%, Co 1.2%, Y2O3 1.2%, with the remainder being Ni. The sum of the mass percentages of the above components is 100%.

[0095] Step 2: Place the powder weighed in Step 1 into a vacuum heating furnace and heat it at 221℃ for 1.3 hours to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 1.3 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0096] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0097] The preparation method of the high-temperature erosion resistant welding wire for water-cooled walls, with the following specific steps: Step 1: Weigh out the following components by mass percentage: 41.0% Cr, 26.0% Nb, 3.1% Al, 3.1% Mo, 1.1% Co, 1.1% C, 0.6% Y2O3, and the remainder Ni. The sum of the mass percentages of the above components is 100%.

[0098] Step 2: Place the weighed medicinal powder from Step 1 into a vacuum heating furnace and heat it at 245℃ for 2.4 hours to remove the water of crystallization from the medicinal powder; place the dried medicinal powder into a powder mixer for thorough mixing for 2.4 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0099] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0100] The purity of each raw material component powder in the welding wire for the metallurgical bonding layer of water-cooled walls and the welding wire for the high-temperature erosion resistant layer of water-cooled walls is ≥99.9%.

[0101] The particle size of each raw material component powder in the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall is 100 mesh.

[0102] The welding wires used for the metallurgical bonding layer of the water-cooled wall and the high-temperature erosion resistant layer of the water-cooled wall are both Inconel 625 strips, with a thickness of 0.4 mm and a width of 7 mm.

[0103] The filling rate of the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall are both controlled at 25wt%.

[0104] A method for preparing a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls is described. The material used in Example 4 is employed to prepare the gradient weld overlay. The preparation method is as follows: First, a metallurgical bonding layer welding wire is used to directly weld over the surface of the water-cooled wall. A CMT power supply is used for the weld overlay, with a welding current of 132A and a weld overlay thickness of 1.55mm. Second, a high-temperature erosion resistant layer welding wire is used to weld over the surface of the metallurgical bonding layer. A CMT power supply is used for the weld overlay, with a welding current of 165A and a weld overlay thickness of 1.65mm.

[0105] The above-mentioned gradient weld overlay was subjected to residual stress testing, Brinell hardness testing, and high-temperature corrosion testing. The results are as follows: (1) The residual stress of the obtained weld overlay is 373 MPa, which is lower than the yield strength of the material and the stress value is low.

[0106] (2) The hardness of the obtained weld overlay is 57HRC, which is relatively high.

[0107] (3) The obtained weld overlay was subjected to a high-temperature corrosion test of sulfate (75wt%NaSO4+25wt%NaCl) at 650℃. After corrosion for 120h, the surface corrosion products were removed and the weight was weighed. The results showed that the weight loss of the weld overlay was 1.32g and the weight loss of the water-cooled wall substrate (the base material without weld overlay treatment) was 12.9g.

[0108] In summary, the gradient weld overlay of the present invention has low stress, high hardness, and excellent high-temperature corrosion resistance.

[0109] Example 5 The preparation method of the welding wire for the metallurgical bonding layer of the water-cooled wall is as follows: Step 1: Weigh out the following components by mass percentage: Fe 76.0%, Cr 8.6%, Nb 1.9%, Mo 1.55%, Co 1.55%, Y2O3 1.55%, with the remainder being Ni. The sum of the mass percentages of the above components is 100%.

[0110] Step 2: Place the weighed powder from Step 1 into a vacuum heating furnace and heat it at 245℃ for 1.45 hours to remove the water of crystallization from the powder. After drying, place the powder into a powder mixer for thorough mixing for 1.59 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0111] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0112] The preparation method of the high-temperature erosion resistant welding wire for water-cooled walls, with the following specific steps: Step 1: Weigh out the following components by mass percentage: 46.5% Cr, 28.0% Nb, 3.9% Al, 3.9% Mo, 1.81% Co, 1.87% C, 0.68% Y2O3, and the remainder Ni. The sum of the mass percentages of the above components is 100%.

[0113] Step 2: Place the weighed powder from Step 1 into a vacuum heating furnace and heat it at 275℃ for 3.7 hours to remove the water of crystallization from the powder. After drying, place the powder into a powder mixer for thorough mixing for 3.8 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0114] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0115] The purity of each raw material component powder in the welding wire for the metallurgical bonding layer of water-cooled walls and the welding wire for the high-temperature erosion resistant layer of water-cooled walls is ≥99.9%.

[0116] The particle size of each raw material component powder in the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall is 200 mesh.

[0117] The welding wires used for the metallurgical bonding layer of the water-cooled wall and the high-temperature erosion resistant layer of the water-cooled wall are both Inconel 625 strips, with a thickness of 0.4 mm and a width of 7 mm.

[0118] The filling rate of the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall are both controlled at 22wt%.

[0119] A method for preparing a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls is described. The material used in Example 5 is employed for preparing the gradient weld overlay. The preparation method is as follows: First, a metallurgical bonding layer welding wire is used to directly weld over the surface of the water-cooled wall. A CMT power supply is used for the weld overlay, with a welding current of 155A and a weld overlay thickness of 1.89mm. Second, a high-temperature erosion resistant layer welding wire is used to weld over the surface of the metallurgical bonding layer. A CMT power supply is used for the weld overlay, with a welding current of 244A and a weld overlay thickness of 1.89mm.

[0120] The above-mentioned gradient weld overlay was subjected to residual stress testing, Brinell hardness testing, and high-temperature corrosion testing. The results are as follows: (1) The residual stress of the obtained weld overlay is 345 MPa, which is lower than the yield strength of the material and the stress value is low.

[0121] (2) The hardness of the obtained weld overlay is 53.5 HRC, which is relatively high.

[0122] (3) The obtained weld overlay was subjected to a high-temperature corrosion test of sulfate (75wt%NaSO4+25wt%NaCl) at 650℃. After corrosion for 120h, the surface corrosion products were removed and the weight was weighed. The results showed that the weight loss of the weld overlay was 1.22g and the weight loss of the water-cooled wall substrate (the base material without weld overlay treatment) was 12.9g.

[0123] In summary, the gradient weld overlay of the present invention has low stress, high hardness, and excellent high-temperature corrosion resistance.

[0124] Example 6 The preparation method of the welding wire for the metallurgical bonding layer of the water-cooled wall is as follows: Step 1: Weigh out the following components by mass percentage: Fe 79.0%, Cr 8.9%, Nb 2.9%, Mo 1.9%, Co 1.9%, Y2O3 1.9%, with the remainder being Ni. The sum of the mass percentages of the above components is 100%.

[0125] Step 2: Place the weighed medicinal powder from Step 1 into a vacuum heating furnace and heat it at 259℃ for 2.9 hours to remove the water of crystallization from the medicinal powder; place the dried medicinal powder into a powder mixer for thorough mixing for 2.9 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0126] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0127] The preparation method of the high-temperature erosion resistant welding wire for water-cooled walls, with the following specific steps: Step 1: Weigh out the following components by mass percentage: 49.0% Cr, 29.0% Nb, 4.9% Al, 4.9% Mo, 1.9% Co, 1.9% C, 0.91% Y2O3, and the remainder Ni. The sum of the mass percentages of the above components is 100%.

[0128] Step 2: Place the weighed powder from Step 1 into a vacuum heating furnace and heat it at 279℃ for 3.9 hours to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 3.9 hours. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced in sequence to finally obtain a flux-cored wire with a diameter of 1.2mm.

[0129] Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

[0130] The purity of each raw material component powder in the welding wire for the metallurgical bonding layer of water-cooled walls and the welding wire for the high-temperature erosion resistant layer of water-cooled walls is ≥99.9%.

[0131] The particle size of each raw material component powder in the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall is 100 mesh.

[0132] The welding wires used for the metallurgical bonding layer of the water-cooled wall and the high-temperature erosion resistant layer of the water-cooled wall are both Inconel 625 strips, with a thickness of 0.4 mm and a width of 7 mm.

[0133] The filling rate of the welding wire for the metallurgical bonding layer of the water-cooled wall and the welding wire for the high-temperature erosion resistant layer of the water-cooled wall are both controlled at 23wt%.

[0134] A method for preparing a dual-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls is described. The material used in Example 6 is employed to prepare the gradient weld overlay. The preparation method is as follows: First, a metallurgical bonding layer welding wire is used to directly weld over the surface of the water-cooled wall. A CMT power supply is used for the weld overlay, with a welding current of 154A and a weld overlay thickness of 1.9mm. Second, a high-temperature erosion resistant layer welding wire is used to weld over the surface of the metallurgical bonding layer. A CMT power supply is used for the weld overlay, with a welding current of 249A and a weld overlay thickness of 1.9mm.

[0135] The above-mentioned gradient weld overlay was subjected to residual stress testing, Brinell hardness testing, and high-temperature corrosion testing. The results are as follows: (1) The residual stress of the obtained weld overlay is 344 MPa, which is lower than the yield strength of the material and the stress value is low.

[0136] (2) The hardness of the obtained weld overlay is 53.7 HRC, which is relatively high.

[0137] (3) The obtained weld overlay was subjected to a high-temperature corrosion test of sulfate (75wt%NaSO4+25wt%NaCl) at 650℃. After corrosion for 120h, the surface corrosion products were removed and the weight was weighed. The results showed that the weight loss of the weld overlay was 1.37g and the weight loss of the water-cooled wall substrate (the base material without weld overlay treatment) was 12.9g.

[0138] In summary, the gradient weld overlay of the present invention has low stress, high hardness, and excellent high-temperature corrosion resistance.

Claims

1. A material for a double-gradient, low-stress, wear-resistant, and corrosion-resistant weld overlay layer for water-cooled walls, characterized in that, This includes welding wires for metallurgical bonding layers of water-cooled walls used for overlay welding on the surface of water-cooled walls, and welding wires for high-temperature erosion-resistant layers of water-cooled walls used for overlay welding on the surface of metallurgical bonding layers.

2. The material for the double-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls according to claim 1, characterized in that, The welding wire for the metallurgical bonding layer of the water-cooled wall comprises flux powder and welding skin. The flux powder comprises the following components by mass percentage: Fe 70.0~80.0%, Cr 8.0~10.0%, Nb 1.0~3.0%, Mo 1.0~2.0%, Co 1.0~2.0%, Y2O3 1.0~2.0%, and the remainder Ni. The sum of the mass percentages of the above components is 100%. The high-temperature erosion resistant welding wire for the water-cooled wall comprises flux powder and welding skin. The flux powder comprises the following components by mass percentage: Cr 40.0~50.0%, Nb 25.0~30.0%, Al 3.0~5.0%, Mo 3.0~5.0%, Co 1.0~2.0%, C 1.0~2.0%, Y2O3 0.5~1.0%, and the remainder is Ni. The sum of the mass percentages of the above components is 100%.

3. The material for the double-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls according to claim 2, characterized in that, The purity of each raw material component powder in the metallurgical bonding layer welding wire of the water-cooled wall and the high-temperature erosion resistant layer welding wire of the water-cooled wall is ≥99.9%.

4. The material for the double-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls according to claim 2, characterized in that, The particle size of each raw material component powder in the metallurgical bonding layer welding wire of the water-cooled wall and the high-temperature erosion resistant layer welding wire of the water-cooled wall is 100 mesh to 200 mesh.

5. The material for the double-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls according to claim 2, characterized in that, The welding wires used for the metallurgical bonding layer of the water-cooled wall and the high-temperature erosion resistant layer of the water-cooled wall are both Inconel 625 strips, with a thickness of 0.4 mm and a width of 7 mm.

6. The material for the double-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls according to claim 2, characterized in that, The filling rate of the metallurgical bonding layer welding wire of the water-cooled wall and the high-temperature erosion resistant layer welding wire of the water-cooled wall are both controlled at 22wt%~25wt%.

7. The material for the double-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls according to claim 2, characterized in that, The specific steps for preparing the welding wire for the metallurgical bonding layer of the water-cooled wall are as follows: Step 1: Weigh out the following components by mass percentage: Fe 70.0~80.0%, Cr 8.0~10.0%, Nb 1.0~3.0%, Mo 1.0~2.0%, Co 1.0~2.0%, Y2O3 1.0~2.0%, with the remainder being Ni. The sum of the mass percentages of the above components should be 100%. Step 2: Place the weighed powder from Step 1 into a vacuum heating furnace and heat it at a temperature of 220℃~260℃ for 1h~3h to remove the water of crystallization from the powder; place the dried powder into a powder mixer for thorough mixing for 1h~3h. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced one by one to finally obtain a flux-cored wire with a diameter of 1.2mm; Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

8. The material for the double-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer for water-cooled walls according to claim 2, characterized in that, The specific steps for preparing the high-temperature erosion-resistant welding wire for the water-cooled wall are as follows: Step 1: Weigh out the following components by mass percentage: Cr 40.0~50.0%, Nb 25.0~30.0%, Al 3.0~5.0%, Mo 3.0~5.0%, Co 1.0~2.0%, C 1.0~2.0%, Y2O3 0.5~1.0%, with the remainder being Ni. The sum of the mass percentages of the above components should be 100%. Step 2: Place the weighed medicinal powder from Step 1 into a vacuum heating furnace and heat it at a temperature of 240℃~280℃ for 2h~4h to remove the water of crystallization from the medicinal powder; place the dried medicinal powder into a powder mixer for thorough mixing for 2h~4h. Step 3: Using Inconel 625 strip as the solder coating, remove the grease from the surface of the Inconel 625 strip with alcohol, and wrap the flux powder prepared in Step 2 inside the Inconel 625 strip using a flux-cored wire drawing device. The diameter of the first drawing die is 2.6mm. Step 4: After the first drawing process is completed, the die hole diameter is reduced one by one to finally obtain a flux-cored wire with a diameter of 1.2mm; Step 5: After the flux-cored welding wire is drawn, it is wound onto the welding wire spool by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for later use.

9. A method for preparing a double-gradient low-stress wear-resistant and corrosion-resistant weld overlay for water-cooled walls, characterized in that, The gradient weld overlay layer is prepared using the material for the double-gradient low-stress wear-resistant and corrosion-resistant weld overlay layer of water-cooled walls as described in claim 2. Specifically, the process is as follows: First, a metallurgical bonding layer welding wire for water-cooled walls is used to directly weld overlay onto the surface of the water-cooled wall. The welding is performed using a CMT power supply with a welding current of 120A~160A and a weld overlay layer thickness of 1.5mm~2.0mm. Second, a high-temperature erosion resistant layer welding wire for water-cooled walls is used to weld overlay onto the surface of the metallurgical bonding layer obtained in the first step. The welding is performed using a CMT power supply with a welding current of 160A~250A and a weld overlay layer thickness of 1.5mm~2.0mm.

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