Iron-based welding wire for anti-cavitation damage of turbine runner, preparation method and surfacing method

Abstract

The present invention relates to the field of metal materials technology and discloses an iron-based welding wire for resisting cavitation damage to a turbine runner, a preparation method, and a surfacing method. The welding wire comprises a flux powder and a welding coating for coating the flux powder. The flux powder comprises an added hard phase and a metal alloy powder. The added hard phase comprises 10.0% to 20.0% by mass, with the remainder being metal alloy powder. The added hard phase comprises 20% to 30% WC powder, 20% to 30% TiC powder, and the remainder being VC powder. The preparation method comprises mixing the above powders, ball milling them, wrapping them with 430 tape, and drawing them. The welding wire of the present invention achieves a Rockwell hardness of 40 to 50 HRC by combining multiple hard phases with a low-heat-input CMT process. The cavitation resistance of the surfacing layer is over 3.5 times that of the 0Cr13Ni5Mo base material, significantly improving the cavitation resistance of the surfacing layer.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials, and particularly relates to an iron-based welding wire for resisting cavitation damage of a turbine runner, a preparation method and a surfacing method. Background Art

[0002] With their advantages of rapid start-up and shutdown, quick power regulation response, and large-scale regulation, hydropower units play an indispensable role in peak and frequency regulation in the power grid, providing key support for the grid's primary and secondary frequency regulation. However, frequent response to frequency regulation commands forces hydropower units to operate under non-design conditions, particularly low loads, for extended periods. This shift in operating mode worsens water flow conditions and significantly increases the frequency and intensity of cavitation erosion in the runner area. Cavitation damage has become a prominent threat to the safe operation of hydropower units.

[0003] Current repair methods for damaged turbine runners rely primarily on factory processing or on-site welding. The former involves long and costly equipment disassembly, transportation, and factory processing, making it difficult to meet urgent repair needs. While the latter can be performed in situ, commonly used repair materials lack cavitation resistance, and the weld overlay is prone to cracking, flaking, and other defects, resulting in poor repair results.

[0004] Ultra-low-carbon martensitic stainless steel 0Cr13Ni5Mo is a preferred material for turbine runners due to its excellent combined mechanical properties (high strength and toughness), corrosion resistance, and good weldability. However, in service, it still struggles to fully withstand the continuous impact and cutting of high-speed cavitation microjets, which can easily induce microcracks and exacerbate localized failures.

[0005] Chinese patent CN119733990A proposes a cavitation-resistant martensitic welding wire for a turbine runner and its preparation method. The wire comprises a flux powder and a weld coating. The flux powder comprises the following components by mass: 20.0-25.0% Cr powder, 25.0-30.0% Ni powder, 5.0-8.0% Mo powder, 3.0-5.0% Nb powder, 3.0-5.0% W powder, 0.5-1.0% C powder, 4.0-6.0% B powder, 0.8-1.0% Y2O3 powder, and the remainder Fe powder. The B powder in the flux powder, as the sole hard phase, combines with elements such as Cr, Mo, and W during the fusion welding process to form an in-situ boride hard phase. While this improves the hardness of the overlay layer, it also reduces its toughness, fatigue resistance, and cavitation resistance. Furthermore, due to the limited adaptability of the welding process, it is difficult to form a uniform, dense, and substrate-bonded overlay layer in complex areas such as the runner's curved surfaces and narrow gaps. This results in the repaired runner having unstable anti-cavitation capabilities and a high damage recurrence rate under alternating hydraulic loads, making it difficult to ensure its long-term service safety under the harsh conditions of peak and frequency regulation. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above problems and provide an iron-based welding wire, preparation method and surfacing method for turbine runner to resist cavitation damage, so as to obtain a surfacing layer with synergistic optimization of hardness and toughness, thereby ensuring the long-term service safety of the hydropower unit under peak and frequency regulation conditions.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising a flux powder and a welding cover for coating the flux powder, wherein the flux powder comprises an added hard phase and a metal alloy powder, wherein, by mass percentage, the added hard phase accounts for 10% to 20% and the remainder is the metal alloy powder;

[0009] In terms of mass percentage, the added hard phase includes: 20% to 30% WC powder, 20% to 30% TiC powder, and the rest is VC powder.

[0010] A further improvement of the present invention is that, in terms of mass percentage, the metal alloy powder comprises: 6.0% to 8.0% Cr powder, 8.0% to 10.0% Ni powder, 4.0% to 6.0% Mo powder, 2.0% to 3.0% B powder, and the remainder Fe powder.

[0011] A further improvement of the present invention is that the powder particle size of the added hard phase is 200-250 mesh.

[0012] A further improvement of the present invention is that the metal alloy powder has a particle size of 100-150 mesh.

[0013] A further improvement of the present invention is that the filling rate of the powder in the welding skin is controlled at 28% to 32%.

[0014] A further improvement of the present invention is that the welding skin is a 430 strip with a thickness of 0.4 mm and a width of 10 mm.

[0015] In a second aspect, the present invention further provides a method for preparing an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising the following steps:

[0016] Step 1: weigh 10.0% to 20.0% of the added hard phase by mass percentage, and the rest is metal alloy powder;

[0017] Step 2, ball-milling and mixing the weighed added hard phase and metal alloy powder to obtain a drug powder;

[0018] Step 3: Wrap the powder prepared in step 2 in the welding skin and perform the first drawing process. The drawing die used in the first drawing process has an aperture of 2.6 mm.

[0019] Step 4: After the first drawing process is completed, several drawing processes are set in sequence, and the aperture of the drawing die corresponding to each drawing process is reduced successively, so that the final welding wire diameter is 1.2~1.4mm, and an iron-based welding wire for anti-cavitation damage of the turbine runner is obtained.

[0020] A further improvement of the present invention is that in step 1, the weighed metal alloy powders are mixed, vacuum-smelted, and atomized to obtain metal alloy powders;

[0021] The gas atomization treatment uses N2 as the atomizing gas, the atomizing pressure is 6~7MPa, and the superheat of the melt is maintained at 100~150℃ during the atomization process.

[0022] A further improvement of the present invention is that in step 2, the ball milling speed is 250-300 r / min and the ball milling time is 1-2 h.

[0023] In a third aspect, the present invention further provides a surfacing method for surfacing an iron-based welding wire for resisting cavitation damage of a turbine runner using a CMT power supply;

[0024] The process parameters of the surfacing welding are as follows:

[0025] The welding current is 160~190A, the molten droplet adopts short-circuit transfer mode during the surfacing process, and the dilution rate is controlled at 3%~5%; the thickness of the surfacing layer is 1.8~2.4mm, the swing width is 15~20mm, the overlap is 5~8mm, the surfacing layer is 1 layer, and the shielding gas is 30%He+70%Ar.

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

[0027] The present invention provides an iron-based welding wire for resisting cavitation damage to a turbine runner. The welding wire comprises a flux powder and a welding coating for wrapping the flux powder. The flux powder comprises an added hard phase and a metal alloy powder. By precisely controlling the content of the added hard phase in the flux powder within a range of 10% to 20%, and synergizing the flux powder with the metal alloy powder, the hard phase can effectively avoid the risk of stress concentration caused by excessive brittle phases while ensuring that the hardfacing layer obtains high hardness, thereby ensuring that the obtained hardfacing layer has high strength, good toughness, and strong cavitation resistance. Specifically, the added hard phases include WC, TiC, and VC. WC powder has high hardness and good wear resistance. During the cladding process, it can be evenly distributed on the substrate to form fine and hard particles. These particles can effectively resist wear when subjected to cavitation impact, thereby improving the hardness of the cladding layer. TiC powder has ultra-high hardness and oxidation resistance. It can form a reinforcing phase in the cladding layer, enhancing the cavitation resistance of the cladding layer and synergizing with WC powder to further improve the hardness and wear resistance of the cladding layer. The addition of VC powder not only increases the hardness of the cladding layer, but also improves its toughness to a certain extent, making it less prone to cracking and flaking when subjected to cavitation impact. The three hard phases work together. Compared with the traditional single hard phase, the addition of multiple hard phases significantly improves the hardness, wear resistance, and toughness of the cladding layer, thereby effectively improving the cavitation resistance of the cladding layer, meeting the cavitation damage protection and repair requirements of the turbine runner surface of the hydropower plant, as well as the performance requirements under the rapid peak-shaving conditions of the hydropower plant.

[0028] Furthermore, the addition of Cr, Ni, Mo, and B to the metal alloy powder in the welding wire provides both solid solution strengthening and precipitation strengthening, significantly enhancing the toughness of the weld overlay. Furthermore, the primary alloying element, Cr, in the welding wire matches the commonly used material for turbines (0Cr13Ni5Mo), resulting in similar linear expansion coefficients. This ensures excellent metallurgical bonding between the weld overlay and the turbine substrate, as well as low weld residual stress.

[0029] The present invention also provides a method for preparing an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising the steps of ball-milling and mixing weighed external hard phase and metal alloy powder to obtain powder, wrapping the powder in a welding sheath, and then subjecting the wire to a drawing process with a multi-pass die with decreasing aperture to precisely control the diameter of the welding wire, thereby achieving uniform dispersion of the powder, and ultimately obtaining an iron-based welding wire for resisting cavitation damage to a turbine runner with excellent hardness and toughness, thereby ensuring the deposition efficiency during the surfacing process.

[0030] Furthermore, the metal alloy powder is prepared by the gas atomization process so that the formed metal alloy powder has higher purity and the metallurgical transition effect during surfacing is more excellent.

[0031] The present invention also provides a surfacing method, which uses a low-heat-input CMT power source to surfacingly weld an iron-based welding wire for resisting cavitation damage to a turbine runner. This not only reduces the decomposition of WC, TiC, and VC added hard phases during the welding process, but also reduces the molten pool residence time and inhibits the sedimentation and aggregation of the added hard phases. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the various components in the drawings are merely schematic and are used to help understand the present invention, and are not intended to specifically limit the shapes and proportional dimensions of the various components of the present invention.

[0033] Figure 1 Schematic diagram of the metallographic structure of the surfacing layer after surfacing welding on 0Cr13Ni5Mo base material using an iron-based welding wire for anti-cavitation damage of a turbine runner prepared in Example 2;

[0034] Figure 2 A schematic diagram of the cavitation damage on the surface of the cladding layer after 4 hours of cavitation testing using an iron-based welding wire for cavitation damage resistance of a hydraulic turbine runner prepared in Example 2 on a 0Cr13Ni5Mo base metal; and a comparison diagram with the base metal;

[0035] Figure 3 Schematic diagram of surface cavitation damage of 0Cr13Ni5Mo base material after 4h cavitation test. DETAILED DESCRIPTION

[0036] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0037] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0038] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0039] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0040] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0041] The present invention provides an iron-based welding wire for resisting cavitation damage of a turbine runner, comprising a flux powder and a welding skin for wrapping the flux powder, wherein the flux powder comprises an added hard phase and a metal alloy powder, wherein, in terms of mass percentage, the added hard phase accounts for 10% to 20% and the rest is the metal alloy powder.

[0042] In terms of mass percentage, the added hard phase includes: 20% to 30% WC powder, 20% to 30% TiC powder, and the rest is VC powder.

[0043] In terms of mass percentage, the metal alloy powder includes: 6.0% to 8.0% of Cr powder, 8.0% to 10.0% of Ni powder, 4.0% to 6.0% of Mo powder, 2.0% to 3.0% of B powder, and the rest is Fe powder.

[0044] The particle size of the powder of the added hard phase is 200~250 mesh.

[0045] The particle size of the metal alloy powder is 100~150 mesh.

[0046] The filling rate of powder in the weld skin is controlled at 28%~32%.

[0047] The welding skin is 430 tape with a thickness of 0.4mm and a width of 10mm.

[0048] The roles and functions of the main alloy components in the welding wire of the present invention are as follows:

[0049] (1) The added hard phases WC, TiC and VC in the welding wire all have the characteristics of high hardness. Specifically:

[0050] 1) WC has high hardness (~2400HV) and wear resistance, which can provide strong support for the matrix; secondly, compared with other carbides, WC also has good toughness and can reduce crack propagation.

[0051] 2) TiC has ultra-high hardness (~3200HV) and oxidation resistance, and can form a TiO2 protective layer at high temperatures; furthermore, TiC can inhibit grain growth, refine grains, and improve high-temperature strength.

[0052] 3) In the WC-Ni system, VC can hinder the dissolution-reprecipitation process of WC grains, that is, VC has a strong inhibitory effect on grain growth. In addition, VC can also improve the red hardness, that is, the high temperature hardness retention rate.

[0053] Multi-component compound addition has the following synergistic advantages:

[0054] First, the hardness-toughness balance: WC provides basic toughness for the matrix, and TiC and VC work together to compensate for the hardness loss of WC at high temperatures; second, the bending strength optimization: VC refines the grains to reduce stress concentration and alleviate the brittle tendency of single TiC; in addition, the abrasion form: WC resists abrasive wear, TiC inhibits adhesive wear, and VC reduces fatigue wear, and the service life can be increased by 30%~50%.

[0055] In summary, the composite addition of WC-TiC-VC achieves a comprehensive improvement in hardness, toughness, and corrosion resistance (wear + cavitation) through the synergy of multiple mechanisms, and is one of the core strategies in high-end alloy design.

[0056] (2) Cr element is added to the metal alloy powder of the welding wire. The Cr element matches the commonly used material of the turbine runner 0Cr13Ni5Mo, thereby ensuring that the metallurgical bonding strength between the two is high and the residual stress is low when the welding wire is surfacing and repaired on the runner surface.

[0057] (3) Ni and Mo are added to the welding wire metal alloy powder: Ni and Mo can be dissolved in the α-Fe matrix of the overlay layer, achieving a solid solution strengthening effect; Ni is an austenite-forming element, and the addition of Ni can regulate the austenite content in the overlay layer. The addition of 8.0% to 10.0% Ni powder in the present invention ensures that there is about 3% to 5% residual austenite in the overlay layer, thereby effectively improving the toughness of the matrix structure of the overlay layer. The toughness and hardness of the overlay layer are two key indicators of cavitation resistance. Therefore, the addition of Ni improves the toughness and strength of the overlay layer, and the addition of Mo improves the strength of the overlay layer.

[0058] (4) Element B is added to the welding wire metal alloy powder: Element B mainly improves performance through mechanisms such as grain boundary strengthening, microstructure refinement and improved hardenability, specifically:

[0059] 1) Grain boundary strengthening and improved hardenability: The matrix structure of the overlay layer is martensite α-Fe. Boron atoms preferentially adsorb at the austenite grain boundaries, reducing the grain boundary energy and inhibiting the precipitation of ferrite and carbides at the grain boundaries. This also slows down the phase transformation process at high temperatures, significantly improving the hardenability of the overlay layer. Grain boundary brittleness suppression: Boron combines with impurity elements (such as S and P) at the grain boundaries, reducing the precipitation of harmful phases such as sulfides and reducing the tendency to temper brittleness.

[0060] 2) Refinement of structure: B forms BN or M2B (M is Cr, Fe, etc.) particles at high temperature, pinning the grain boundaries to inhibit the coarsening of austenite grains and refine the martensite laths after quenching; homogenization of structure: reducing local coarse martensite and improving the matching of strength and toughness.

[0061] 3) Carbide regulation: B preferentially combines with Cr to form Cr2B, which reduces the consumption of Cr carbides, avoids chromium depletion at grain boundaries, and improves the corrosion resistance of the heat-affected zone of welding.

[0062] 4) Other functions: B, when combined with Cr and Mo, can enhance the hardenability effect of B.

[0063] In summary, the composite addition of Cr, Ni, Mo and B elements achieves the strength and toughness matching of the cladding layer through multiple synergistic mechanisms, thereby improving the cavitation resistance of the cladding layer.

[0064] The present invention also provides a method for preparing an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising the following steps:

[0065] Step 1: weigh 10.0% to 20.0% of the added hard phase by mass percentage, and the rest is metal alloy powder;

[0066] Step 2, ball-milling and mixing the weighed added hard phase and metal alloy powder to obtain a drug powder;

[0067] Step 3: Wrap the powder prepared in step 2 in the welding skin and perform the first drawing process. The drawing die used in the first drawing process has an aperture of 2.6 mm.

[0068] Step 4: After the first drawing process is completed, several drawing processes are set in sequence, and the aperture of the drawing die corresponding to each drawing process is reduced successively, so that the final welding wire diameter is 1.2~1.4mm, and an iron-based welding wire for anti-cavitation damage of the turbine runner is obtained.

[0069] In step 1, the weighed metal alloy powders are mixed, vacuum-melted, and atomized to obtain metal alloy powders;

[0070] The gas atomization treatment uses N2 as the atomizing gas, the atomizing pressure is 6~7MPa, and the superheat of the melt is maintained at 100~150℃ during the atomization process.

[0071] In step 2, the ball milling speed is 250-300 r / min, and the ball milling time is 1-2 h.

[0072] The present invention also provides a surfacing method, which uses a CMT power source to perform surfacing welding on the iron-based welding wire for resisting cavitation damage of the turbine runner;

[0073] The process parameters of the surfacing welding are as follows:

[0074] The welding current is 160~190A, the molten droplet adopts short-circuit transfer mode during the surfacing process, and the dilution rate is controlled at 3%~5%; the thickness of the surfacing layer is 1.8~2.4mm, the swing width is 15~20mm, the overlap is 5~8mm, the surfacing layer is 1 layer, and the shielding gas is 30%He+70%Ar.

[0075] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0076] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0077] The following embodiments of the present invention all perform arc surfacing welding on 0Cr13Ni5Mo base metal.

[0078] Example 1

[0079] This embodiment provides a method for preparing an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising the following steps:

[0080] Step 1: Weigh the following metal alloy powders by mass percentage: 6.0% Cr powder, 8.0% Ni powder, 4.0% Mo powder, 2.0% B powder, and the remainder Fe powder;

[0081] Step 2: Mix the metal alloy powders weighed in step 1, and then perform vacuum melting to prepare metal alloy powders by gas atomization. The atomized metal alloy powders are sieved to obtain a particle size of 125±25 mesh.

[0082] Step 3, weighing 20% ​​WC powder, 20% TiC powder, and the rest VC powder by mass percentage, and mixing them to obtain an additional hard phase;

[0083] Step 4, weighing 10% of the added hard phase by mass percentage, and the rest being metal alloy powder;

[0084] Step 5: Place the weighed additional hard phase and metal alloy powder into a planetary ball mill for ball milling at a speed of 250 r / min for 1 h, so that the additional hard phase and metal alloy powder are fully mixed and partially mechanically welded to obtain a powder;

[0085] Step 6: Use alcohol to remove grease from the surface of the 430 tape, and wrap the powder prepared in step 6 in the 430 tape through a flux-cored wire drawing device to perform the first drawing process. The drawing die used in the first drawing process has an aperture of 2.6 mm.

[0086] Step 7: After the first drawing process is completed, several drawing processes are set in sequence, and the aperture of the drawing die corresponding to each drawing process is reduced in sequence, and finally a welding wire with a diameter of 1.2 mm is obtained;

[0087] Step 8: After the welding wire is drawn, it is wound on a wire reel by a wire winding machine and finally sealed in a welding wire vacuum packaging bag for standby use.

[0088] The iron-based welding wire for resisting cavitation damage of a turbine runner prepared in Example 1 was used for arc surfacing welding on the surface of a 0Cr13Ni5Mo substrate. A CMT power supply was used, the welding current was 160 A, the droplet adopted a short-circuit transfer mode during the surfacing process, and the dilution rate was controlled at 3%. The surfacing layer thickness was 1.8 mm, the swing width was 15 mm, the overlap was 5 mm, and one layer was surfacing. The shielding gas was a helium-argon mixture (30% He + 70% Ar).

[0089] Tested:

[0090] (1) The Rockwell hardness of the cladding layer is 41HRC;

[0091] (2) After 18 hours of cavitation test, the weight loss of the cladding layer is 0.5 mg. After the same time of cavitation test, the weight loss of the base material 0Cr13Ni5Mo is 1.75 mg. Therefore, the cavitation resistance of the cladding layer is 3.5 times that of the base material.

[0092] Example 2

[0093] This embodiment provides a method for preparing an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising the following steps:

[0094] Step 1: Weigh the following metal alloy powders by mass percentage: 8.0% Cr powder, 10.0% Ni powder, 6.0% Mo powder, 3.0% B powder, and the remainder Fe powder;

[0095] Step 2: Mix the metal alloy powders weighed in step 1, and then perform vacuum melting to prepare metal alloy powders by gas atomization. The atomized metal alloy powders are sieved to obtain a particle size of 125±25 mesh.

[0096] Step 3, weighing 30% WC powder, 30% TiC powder, and the rest VC powder by mass percentage, and mixing them to obtain an additional hard phase;

[0097] Step 4, weighing 20% ​​of the added hard phase by mass percentage, and the rest being metal alloy powder;

[0098] Step 5: The weighed additional hard phase and metal alloy powder are placed in a planetary ball mill for ball milling at a speed of 300 r / min for 2 h, so that the additional hard phase and metal alloy powder are fully mixed and partially mechanically welded to obtain a drug powder;

[0099] Step 6: Use alcohol to remove grease from the surface of the 430 tape, and wrap the powder prepared in step 6 in the 430 tape through a flux-cored wire drawing device to perform the first drawing process. The drawing die used in the first drawing process has an aperture of 2.6 mm.

[0100] Step 7: After the first drawing process is completed, several drawing processes are set in sequence, and the aperture of the drawing die corresponding to each drawing process is reduced in sequence, and finally a welding wire with a diameter of 1.2 mm is obtained;

[0101] Step 8: After the welding wire is drawn, it is wound on a wire reel by a wire winding machine and finally sealed in a welding wire vacuum packaging bag for standby use.

[0102] The iron-based welding wire for resisting cavitation damage of a turbine runner prepared in Example 2 was used for arc surfacing welding on the surface of a 0Cr13Ni5Mo substrate. A CMT power supply was used, the welding current was 190 A, the droplet adopted a short-circuit transfer mode during the surfacing process, and the dilution rate was controlled at 5%. The surfacing layer thickness was 2.4 mm, the swing width was 20 mm, the overlap was 8 mm, and one layer was surfacing. The shielding gas was a helium-argon mixture (30% He + 70% Ar).

[0103] Tested:

[0104] (1) The Rockwell hardness of the cladding layer is 43HRC;

[0105] (2) After 18 hours of cavitation test, the weight loss of the weld overlay layer is 0.45 mg. After the same time of cavitation test, the weight loss of the base material 0Cr13Ni5Mo is 1.75 mg. Therefore, the cavitation resistance of the weld overlay layer is 3.8 times that of the base material.

[0106] Figure 1 This diagram shows the metallographic structure of the weld overlay layer after surfacing welding the iron-based welding wire for cavitation damage resistance of a hydraulic turbine runner, prepared in Example 2, onto 0Cr13Ni5Mo base metal. As can be seen from the diagram, the weld overlay layer is primarily martensitic, and the base metal also has a martensitic structure, resulting in a matching structure.

[0107] Figure 2 This is a diagram showing the surface cavitation damage of a 0Cr13Ni5Mo base metal overlay welded with an iron-based welding wire for cavitation damage resistance of a hydraulic turbine runner prepared in Example 2, after a 4-hour cavitation test. Figure 3 This is the surface cavitation damage diagram of 0Cr13Ni5Mo base material after 4h cavitation test. Figure 2 and Figure 3 It can be seen from the figure that the cavitation pits on the surface of the cladding layer formed by the welding wire of the present invention are significantly less than those on the surface of the 0Cr13Ni5Mo base material.

[0108] Example 3

[0109] This embodiment provides a method for preparing an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising the following steps:

[0110] Step 1: Weigh the following metal alloy powders by mass percentage: 7.0% Cr powder, 9.0% Ni powder, 5.0% Mo powder, 2.5.0% B powder, and the remainder Fe powder;

[0111] Step 2: Mix the metal alloy powders weighed in step 1, and then perform vacuum melting to prepare metal alloy powders by gas atomization. The atomized metal alloy powders are sieved to obtain a particle size of 125±25 mesh.

[0112] Step 3, weighing 25% WC powder, 25% TiC powder, and the rest VC powder by mass percentage, and mixing them to obtain an additional hard phase;

[0113] Step 4, weighing 15% of the added hard phase by mass percentage, and the rest being metal alloy powder;

[0114] Step 5: Place the weighed additional hard phase and metal alloy powder into a planetary ball mill for ball milling at a speed of 280 r / min for 1.5 h, so that the additional hard phase and metal alloy powder are fully mixed and partially mechanically welded to obtain a powder;

[0115] Step 6: Use alcohol to remove grease from the surface of the 430 tape, and wrap the powder prepared in step 6 in the 430 tape through a flux-cored wire drawing device to perform the first drawing process. The drawing die used in the first drawing process has an aperture of 2.6 mm.

[0116] Step 7: After the first drawing process is completed, several drawing processes are set in sequence, and the aperture of the drawing die corresponding to each drawing process is reduced in sequence, and finally a welding wire with a diameter of 1.2 mm is obtained;

[0117] Step 8: After the welding wire is drawn, it is wound on a wire reel by a wire winding machine and finally sealed in a welding wire vacuum packaging bag for standby use.

[0118] The iron-based welding wire for resisting cavitation damage of a turbine runner prepared in Example 3 was used for arc surfacing welding on the surface of a 0Cr13Ni5Mo substrate. A CMT power supply was used, the welding current was 180 A, the droplet adopted a short-circuit transfer mode during the surfacing process, and the dilution rate was controlled at 4%. The surfacing layer thickness was 2.1 mm, the swing width was 17 mm, the overlap was 7 mm, and one layer was surfacing. The shielding gas was a helium-argon mixture (30% He + 70% Ar).

[0119] Tested:

[0120] (1) The Rockwell hardness of the cladding layer is 44HRC;

[0121] (2) After 18 hours of cavitation test, the weight loss of the cladding layer is 0.41 mg. After the same time of cavitation test, the weight loss of the base material 0Cr13Ni5Mo is 1.75 mg. Therefore, the cavitation resistance of the cladding layer is 4.2 times that of the base material.

[0122] Example 4

[0123] This embodiment provides a method for preparing an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising the following steps:

[0124] Step 1: Weigh the following metal alloy powders by mass percentage: 6.8% Cr powder, 8.1% Ni powder, 4.6% Mo powder, 2.3% B powder, and the remainder Fe powder;

[0125] Step 2: Mix the metal alloy powders weighed in step 1, and then perform vacuum melting to prepare metal alloy powders by gas atomization. The atomized metal alloy powders are sieved to obtain a particle size of 125±25 mesh.

[0126] Step 3, weighing 26% WC powder, 26% TiC powder, and the rest VC powder, respectively, by mass percentage, and mixing them to obtain an additional hard phase;

[0127] Step 4, weighing 16% of the added hard phase by mass percentage, and the rest being metal alloy powder;

[0128] Step 5: The weighed additional hard phase and metal alloy powder are placed in a planetary ball mill for ball milling at a speed of 260 r / min for 1.2 h, so that the additional hard phase and metal alloy powder are fully mixed and partially mechanically welded to obtain a powder;

[0129] Step 6: Use alcohol to remove grease from the surface of the 430 tape, and wrap the powder prepared in step 6 in the 430 tape through a flux-cored wire drawing device to perform the first drawing process. The drawing die used in the first drawing process has an aperture of 2.6 mm.

[0130] Step 7: After the first drawing process is completed, several drawing processes are set in sequence, and the aperture of the drawing die corresponding to each drawing process is reduced in sequence, and finally a welding wire with a diameter of 1.2 mm is obtained;

[0131] Step 8: After the welding wire is drawn, it is wound on a wire reel by a wire winding machine and finally sealed in a welding wire vacuum packaging bag for standby use.

[0132] The iron-based welding wire for resisting cavitation damage of a turbine runner prepared in Example 4 was used for arc surfacing welding on the surface of a 0Cr13Ni5Mo substrate. A CMT power supply was used, the welding current was 170 A, the droplet adopted a short-circuit transfer mode during the surfacing process, and the dilution rate was controlled at 3.5%. The surfacing layer thickness was 2.0 mm, the swing width was 16 mm, the overlap was 6 mm, and one layer was surfacing. The shielding gas was a helium-argon mixture (30% He + 70% Ar).

[0133] Tested:

[0134] (1) The Rockwell hardness of the cladding layer is 42.5HRC;

[0135] (2) After 18 hours of cavitation test, the weight loss of the cladding layer is 0.44 mg. After the same time of cavitation test, the weight loss of the base material 0Cr13Ni5Mo is 1.75 mg. Therefore, the cavitation resistance of the cladding layer is 3.9 times that of the base material.

[0136] Example 5

[0137] This embodiment provides a method for preparing an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising the following steps:

[0138] Step 1: Weigh the following metal alloy powders by mass percentage: 7.9% Cr powder, 9.9% Ni powder, 5.9% Mo powder, 2.9% B powder, and the remainder Fe powder;

[0139] Step 2: Mix the metal alloy powders weighed in step 1, and then perform vacuum melting to prepare metal alloy powders by gas atomization. The atomized metal alloy powders are sieved to obtain a particle size of 125±25 mesh.

[0140] Step 3, weighing 29% WC powder, 29% TiC powder, and the rest VC powder, by mass percentage, and mixing them to obtain an additional hard phase;

[0141] Step 4, weighing 19% of the added hard phase by mass percentage, and the rest being metal alloy powder;

[0142] Step 5: The weighed additional hard phase and metal alloy powder are placed in a planetary ball mill for ball milling at a speed of 290 r / min for 1.9 h, so that the additional hard phase and metal alloy powder are fully mixed and partially mechanically welded to obtain a powder;

[0143] Step 6: Use alcohol to remove grease from the surface of the 430 tape, and wrap the powder prepared in step 6 in the 430 tape through a flux-cored wire drawing device to perform the first drawing process. The drawing die used in the first drawing process has an aperture of 2.6 mm.

[0144] Step 7: After the first drawing process is completed, several drawing processes are set in sequence, and the aperture of the drawing die corresponding to each drawing process is reduced in sequence, and finally a welding wire with a diameter of 1.2 mm is obtained;

[0145] Step 8: After the welding wire is drawn, it is wound on a wire reel by a wire winding machine and finally sealed in a welding wire vacuum packaging bag for standby use.

[0146] The iron-based welding wire for resisting cavitation damage of a turbine runner prepared in Example 5 was used for arc surfacing welding on the surface of a 0Cr13Ni5Mo substrate. A CMT power supply was used, the welding current was 180 A, the droplet adopted a short-circuit transfer mode during the surfacing process, and the dilution rate was controlled at 3.2%. The surfacing layer thickness was 1.9 mm, the swing width was 19 mm, the overlap was 6.5 mm, and one layer was surfacing. The shielding gas was a helium-argon mixture (30% He + 70% Ar).

[0147] Tested:

[0148] (1) The Rockwell hardness of the cladding layer is 47HRC;

[0149] (2) After 18 hours of cavitation test, the weight loss of the cladding layer is 0.38 mg. After the same time of cavitation test, the weight loss of the base material 0Cr13Ni5Mo is 1.75 mg. Therefore, the cavitation resistance of the cladding layer is 4.6 times that of the base material.

[0150] Example 6

[0151] This embodiment provides a method for preparing an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising the following steps:

[0152] Step 1: Weigh the following metal alloy powders by mass percentage: 6.1% Cr powder, 8.3% Ni powder, 4.3% Mo powder, 2.1% B powder, and the remainder Fe powder;

[0153] Step 2: Mix the metal alloy powders weighed in step 1, and then perform vacuum melting to prepare metal alloy powders by gas atomization. The atomized metal alloy powders are sieved to obtain a particle size of 125±25 mesh.

[0154] Step 3, weighing 22% WC powder, 22% TiC powder, and the rest VC powder, by mass percentage, and mixing them to obtain an additional hard phase;

[0155] Step 4, weighing 12% of the added hard phase by mass percentage, and the rest being metal alloy powder;

[0156] Step 5: The weighed additional hard phase and metal alloy powder are placed in a planetary ball mill for ball milling at a speed of 255 r / min for 1.1 h, so that the additional hard phase and metal alloy powder are fully mixed and partially mechanically welded to obtain a powder;

[0157] Step 6: Use alcohol to remove grease from the surface of the 430 tape, and wrap the powder prepared in step 6 in the 430 tape through a flux-cored wire drawing device to perform the first drawing process. The drawing die used in the first drawing process has an aperture of 2.6 mm.

[0158] Step 7: After the first drawing process is completed, several drawing processes are set in sequence, and the aperture of the drawing die corresponding to each drawing process is reduced in sequence, and finally a welding wire with a diameter of 1.2 mm is obtained;

[0159] Step 8: After the welding wire is drawn, it is wound on a wire reel by a wire winding machine and finally sealed in a welding wire vacuum packaging bag for standby use.

[0160] The iron-based welding wire for resisting cavitation damage of a turbine runner prepared in Example 6 was used for arc surfacing welding on the surface of a 0Cr13Ni5Mo substrate. A CMT power supply was used, the welding current was 185 A, the droplet adopted a short-circuit transfer mode during the surfacing process, and the dilution rate was controlled at 4.5%. The surfacing layer thickness was 2.2 mm, the swing width was 15.5 mm, the overlap was 7.5 mm, and one layer was surfacing. The shielding gas was a helium-argon mixture (30% He + 70% Ar).

[0161] Tested:

[0162] (1) The Rockwell hardness of the cladding layer is 43.5HRC

[0163] (2) After 18 hours of cavitation test, the weight loss of the cladding layer is 0.39 mg. After the same time of cavitation test, the weight loss of the base material 0Cr13Ni5Mo is 1.75 mg. Therefore, the cavitation resistance of the cladding layer is 4.4 times that of the base material.

[0164] Example 7

[0165] This embodiment provides a method for preparing an iron-based welding wire for resisting cavitation damage to a turbine runner, comprising the following steps:

[0166] Step 1: Weigh the following metal alloy powders by mass percentage: 6.35% Cr powder, 9.75% Ni powder, 5.88% Mo powder, 2.78% B powder, and the remainder Fe powder;

[0167] Step 2: Mix the metal alloy powders weighed in step 1, and then perform vacuum melting to prepare metal alloy powders by gas atomization. The atomized metal alloy powders are sieved to obtain a particle size of 125±25 mesh.

[0168] Step 3, weighing 29.5% WC powder, 29.5% TiC powder, and the rest VC powder, by mass percentage, and mixing them to obtain an additional hard phase;

[0169] Step 4, weighing 18.5% of the added hard phase by mass percentage, and the rest being metal alloy powder;

[0170] Step 5: The weighed additional hard phase and metal alloy powder are placed in a planetary ball mill for ball milling at a speed of 287 r / min for 1.7 h, so that the additional hard phase and metal alloy powder are fully mixed and partially mechanically welded to obtain a powder;

[0171] Step 6: Use alcohol to remove grease from the surface of the 430 tape, and wrap the powder prepared in step 6 in the 430 tape through a flux-cored wire drawing device to perform the first drawing process. The drawing die used in the first drawing process has an aperture of 2.6 mm.

[0172] Step 7: After the first drawing process is completed, several drawing processes are set in sequence, and the aperture of the drawing die corresponding to each drawing process is reduced in sequence, and finally a welding wire with a diameter of 1.2 mm is obtained;

[0173] Step 8: After the welding wire is drawn, it is wound on a wire reel by a wire winding machine and finally sealed in a welding wire vacuum packaging bag for standby use.

[0174] The iron-based welding wire for resisting cavitation damage of a turbine runner prepared in Example 7 was used for arc surfacing welding on the surface of a 0Cr13Ni5Mo substrate. A CMT power supply was used, the welding current was 188 A, the droplet adopted a short-circuit transfer mode during the surfacing process, and the dilution rate was controlled at 3.1%. The surfacing layer thickness was 2.3 mm, the swing width was 15.6 mm, the overlap was 7.5 mm, and one layer was surfacing. The shielding gas was a helium-argon mixture (30% He + 70% Ar).

[0175] Tested:

[0176] (1) The Rockwell hardness of the cladding layer is 49HRC;

[0177] (2) After 18 hours of cavitation test, the weight loss of the cladding layer is 0.31 mg. After the same time of cavitation test, the weight loss of the base material 0Cr13Ni5Mo is 1.75 mg. Therefore, the cavitation resistance of the cladding layer is 5.6 times that of the base material.

[0178] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An iron-based welding wire for anti-cavitation damage of a turbine runner, characterized in that: The invention comprises a powder and a welding skin for wrapping the powder, wherein the powder comprises an external hard phase and a metal alloy powder, wherein, by mass percentage, the external hard phase accounts for 10% to 20% and the rest is the metal alloy powder; In terms of mass percentage, the added hard phase comprises: 20% to 30% WC powder, 20% to 30% TiC powder, and the remainder VC powder; The metal alloy powder comprises, by mass percentage, 6.0% to 8.0% of Cr powder, 8.0% to 10.0% of Ni powder, 4.0% to 6.0% of Mo powder, 2.0% to 3.0% of B powder, and the remainder being Fe powder; The filling rate of the powder in the welding skin is controlled at 28% to 32%; The welding skin is 430 tape with a thickness of 0.4 mm and a width of 10 mm.

2. The iron-based welding wire for anti-cavitation damage of a water turbine runner according to claim 1, characterized in that: The powder particle size of the added hard phase is 200-250 mesh.

3. The iron-based welding wire for anti-cavitation damage of a water turbine runner according to claim 1, characterized in that: The metal alloy powder has a particle size of 100-150 mesh.

4. A method for preparing an iron-based welding wire for resisting cavitation damage to a water turbine runner according to claim 1, characterized in that: The following steps are involved: Step 1: weigh 10.0% to 20.0% of the added hard phase by mass percentage, and the rest is metal alloy powder; Step 2, ball-milling and mixing the weighed added hard phase and metal alloy powder to obtain a drug powder; Step 3: Wrap the powder prepared in step 2 in the welding skin and perform the first drawing process. The drawing die used in the first drawing process has an aperture of 2.6 mm. Step 4: After the first drawing process is completed, several drawing processes are set in sequence, and the aperture of the drawing die corresponding to each drawing process is reduced successively, so that the final welding wire diameter is 1.2~1.4mm, and an iron-based welding wire for anti-cavitation damage of the turbine runner is obtained.

5. The method for preparing an iron-based welding wire for resisting cavitation damage to a water turbine runner according to claim 4, characterized in that: In the step 1, the weighed metal alloy powders are mixed, vacuum-melted, and atomized to obtain metal alloy powders; The gas atomization treatment uses N2 as the atomizing gas, the atomizing pressure is 6~7MPa, and the superheat of the melt is maintained at 100~150℃ during the atomization process.

6. The method for preparing an iron-based welding wire for resisting cavitation damage to a water turbine runner according to claim 4, characterized in that: In step 2, the ball milling speed is 250-300 r / min, and the ball milling time is 1-2 h.

7. A surfacing method, characterized in that: Using a CMT power source to perform surfacing welding on the iron-based welding wire for resisting cavitation damage of a turbine runner according to any one of claims 1 to 3; The process parameters of the surfacing welding are as follows: The welding current is 160~190A, the molten droplet adopts short-circuit transfer mode during the surfacing process, and the dilution rate is controlled at 3%~5%; the thickness of the surfacing layer is 1.8~2.4mm, the swing width is 15~20mm, the overlap is 5~8mm, the surfacing layer is 1 layer, and the shielding gas is 30%He+70%Ar.

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