Hydraulic turbine blade surface composite coating and high-speed laser cladding preparation method and application

Abstract

The application discloses a water turbine blade surface composite coating and a high-speed laser cladding preparation method and application, and belongs to the technical field of water power equipment surface protection coating preparation, and the method comprises the following steps: mixing a base phase and a reinforcing phase by ball milling to obtain a cermet composite powder; and using a high-speed laser cladding technology to deposit the cermet composite powder on the surface of a pretreated water turbine blade to obtain a water turbine blade surface composite coating; the base phase is a nano / sub-micron autogenous ceramic phase composite nickel-based alloy; and the reinforcing phase is a micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particle. By preparing a multistage composite coating on the surface of the water turbine blade, the anti-erosion-wear performance and the strength and toughness are improved, stress cracking in the cladding process is resisted, and the peeling of the hard phase in the erosion and wear process is reduced. The multistage reinforcing phase particles play a synergistic shadow protection role in the coating, the anti-sand erosion and wear performance is improved, and a new path is provided for long-term protection and repair of the surface of the water turbine blade.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of surface protective coating preparation of hydroelectric equipment, and particularly relates to a surface composite coating of a water turbine blade and a high-speed laser cladding preparation method and application. BACKGROUND

[0002] The water turbine unit is the core equipment of hydroelectric power generation. The flow parts such as the water turbine blade, the water turbine pump and the pipeline suffer severe erosion-wear damage from silt and other substances during service, resulting in the appearance of holes and pits and other damage on the surface of the key parts such as the water turbine blade, which not only affects the stable operation period and safe service life of the water turbine equipment, but also reduces its operating efficiency, causing huge economic losses. Therefore, it is necessary to prepare a protective coating with excellent erosion-wear resistance on the surface of the key flow parts such as the water turbine blade, so as to significantly improve the erosion-wear resistance of the water turbine blade substrate, thereby improving its service life and working efficiency and reducing the operation and maintenance cost.

[0003] At present, the commonly used surface protection technologies for the flow parts of the water turbine unit equipment mainly include surfacing, thermal spraying and laser cladding. Compared with the surfacing and thermal spraying technologies, laser cladding not only can obtain a metallurgical bonding coating, but also can effectively control the dilution rate of the coating, the heat affected zone of the substrate and the thermal deformation, showing greater application potential in the preparation of surface protective coatings for water turbine blades. For example, the Chinese patent application with publication number CN112663044B discloses a cobalt-based alloy laser cladding powder for water turbine blades and a laser cladding method thereof, which prepares a cladding layer with dense structure and fine grains, effectively improving the wear resistance, corrosion resistance and cavitation resistance of the cladding layer. The Chinese patent application with publication number CN116397225A discloses a laser cladding material resistant to cavitation and its application in the surface repair of flow parts of a hydroelectric power station, which obtains a laser cladding coating with high chemical stability, high hardness, wear resistance and metal toughness, showing good cavitation and erosion resistance. However, the traditional laser cladding technology has low preparation efficiency, which greatly limits its application in the surface protection field of key parts such as water turbine blades. In recent years, high-speed laser cladding technology has emerged, which significantly improves the processing efficiency and reduces the dilution rate of the coating compared with the traditional laser cladding technology, and promotes the grain refinement of the coating, which is beneficial to improve its wear and corrosion resistance.

[0004] The current applied anti-erosion-wear coating is mainly divided into metal coating and ceramic coating. The metal coating has good corrosion resistance and laser cladding processing performance, but its hardness is low and the anti-erosion-wear performance is insufficient; the ceramic coating has the advantages of high hardness and high corrosion resistance, but due to its poor plasticity and toughness, the cracking phenomenon is serious in the laser cladding process, and it is difficult to obtain a defect-free coating. Therefore, it is necessary to develop a new type of composite coating material with excellent anti-erosion-wear performance and laser cladding processing performance. The coating not only shows high hardness to significantly improve the anti-erosion-wear performance of the surface of the water turbine blade, but also has good plasticity and toughness to solve the cracking problem of the coating in the high-speed laser cladding process. SUMMARY

[0005] In order to overcome the above-mentioned defects of the prior art, the purpose of the present application is to provide a water turbine blade surface composite coating and a high-speed laser cladding preparation method and application, so as to solve the technical problem of serious damage of the water turbine blade under severe erosion-wear working conditions.

[0006] In order to achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0007] The present application discloses a high-speed laser cladding preparation method for a water turbine blade surface composite coating, comprising the following steps:

[0008] Mechanically ball-milling the matrix phase and the reinforcing phase to obtain a cermet composite powder;

[0009] Using high-speed laser cladding technology, the cermet composite powder is deposited on the pretreated surface of the water turbine blade to obtain a water turbine blade surface composite coating;

[0010] The water turbine blade surface composite coating has a nano / sub-micron / micron multi-level composite reinforcing structure;

[0011] The matrix phase in the water turbine blade surface composite coating is a nano / sub-micron autogenous ceramic phase composite nickel-based alloy, and the reinforcing phase is a micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particle;

[0012] The laser power of the high-speed laser cladding technology is 1000-3000W; the laser scanning rate is ≥5000mm / min, and the overlap rate is ≥70%.

[0013] Preferably, in the cermet composite powder, the content of the reinforcing phase is 10%-70%.

[0014] Preferably, in the nano / sub-micron autogenous ceramic phase composite nickel-based alloy, the mass fraction of Cr is ≥15%; the melting point is ≤1400℃; the hardness is 250-500HV; and the particle size is 30-105μm.

[0015] Preferably, in the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles, the Mo content is 35% to 45%, the B content is 3% to 5%, the Ti content is 1% to 3%, and the Cr content is 5.5% to 9.5%, with the remainder being Ni.

[0016] The micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles include a sub-micron-sized boride ceramic phase and a nickel-based metal binder phase; the sub-micron-sized boride ceramic phase content is ≥70%, the hardness is ≥1000HV, the fracture toughness is ≥15MPa·m 1 / 2 , the melting point is higher than 1400℃, and the particle size is 50 to 200μm.

[0017] Preferably, the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles are prepared by a vacuum electrode induction melting atomization method, including the following steps:

[0018] The MoB powder, the Ni2B powder, the Ti powder, and the Cr powder are ball-mixed, pre-pressed, pre-burned, melted, and cooled to obtain a cermet bulk; the cermet bulk is vacuum electrode induction melted and atomized to obtain the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles.

[0019] Preferably, the pre-pressing pressure is ≥40MPa; the pre-burning temperature is 800 to 1000℃; and the pre-burning time is 20 to 60min.

[0020] The melting conditions include: a vacuum degree of ≤3Pa, a melting temperature of 1500 to 1800℃, and a holding time of ≥20min.

[0021] The vacuum electrode induction melting atomization conditions include: controlling the vacuum degree to be ≤10 -3 Pa, controlling the rotation speed to be 5 to 80r / min, controlling the feeding speed to be 3 to 300mm / min, and controlling the airflow pressure to be 2 to 6MPa.

[0022] Preferably, the mechanical ball-milling rotation speed is 100 to 300r / min, and the ball-to-material ratio is (1 to 5):1.

[0023] Preferably, the high-speed laser cladding technology has a laser power of 1000 to 3000W, a laser scanning speed of ≥5000mm / min, and an overlapping rate of ≥70%.

[0024] Preferably, before the high-speed laser cladding, the method further includes: vacuum drying the cermet composite powder at 120 to 200℃ for 0.5 to 3h.

[0025] Before high-speed laser cladding, further comprising: laser scanning preheating treatment is carried out to the pretreated surface of the water turbine blade; the laser scanning power is 700-1200W, and the laser scanning rate is 1000-3000mm / min.

[0026] The application further discloses a water turbine blade surface composite coating prepared by the high-speed laser cladding preparation method of the water turbine blade surface composite coating. 2 The water turbine blade surface composite coating has a thickness of no less than 300 microns, a cladding efficiency of no less than 0.6m / h, a hardness of 800-1100HV, a corrosion potential of-0.55 to-0.42V and a relative erosion wear performance of 10-25.

[0027] The application further discloses application of the water turbine blade surface composite coating prepared by the high-speed laser cladding preparation method of the water turbine blade surface composite coating in surface protection of key components of water power generation equipment.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] The application provides a high-speed laser cladding preparation method of a water turbine blade surface composite coating.

[0030] Further, by controlling the content of the reinforcing phase in the specific range of 10% to 70%, the toughness and erosion-wear resistance of the coating can be reasonably balanced. If the content of the reinforcing phase is too low, the reinforcing phase cannot fully play a role in improving the performance of the coating, and the erosion-wear resistance of the coating cannot be effectively improved. If the content is too high, the coating may crack during the cladding process due to stress concentration and other problems, affecting the quality and service life of the coating. This content range can achieve good preparation effect under the premise of ensuring the performance of the coating, provide reliable long-term protection for the water turbine blade, and has important engineering practical value.

[0031] Further, in the nano / sub-micron autogenous ceramic phase composite nickel-based alloy, the mass fraction of Cr is ≥15%: Cr element has good solid solution strengthening effect in nickel-based alloy, which can significantly improve the strength and hardness of the alloy, and Cr can also form a dense oxide film on the surface of the alloy, effectively improving the corrosion resistance of the alloy, which is crucial for water turbine blades operating in harsh conditions, can prolong the service life of the blade, and reduce the maintenance and replacement cost caused by corrosion and wear. The melting point is ≤1400℃, which is beneficial to rapid melting of the powder and good metallurgical bonding with the substrate during high-speed laser cladding, reduces the energy consumption during cladding, improves the cladding efficiency, and reduces the adverse effects of high temperature on the performance of the substrate, ensuring that the overall performance of the substrate is not damaged. The hardness is 250-500HV, which can reasonably cooperate with the reinforcing phase, ensure that the coating has a certain toughness, and at the same time, give the coating enough hardness to resist erosion and wear, so that the coating can operate stably for a long time in complex working environment, improve the reliability and durability of the water turbine blade. The particle size is 30-105μm, which can ensure uniform spreading and full melting of the powder during laser cladding, is beneficial to forming a dense and uniform coating structure, avoids defects such as pores and cracks caused by uneven powder particle size, and thus improves the quality and performance of the coating.

[0032] Further, in the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles, the Mo content is 35% to 45%, the B content is 3% to 5%, the Ti content is 1% to 3%, the Cr content is 5.5% to 9.5%, and the rest is Ni; Mo element has the characteristics of high melting point and high hardness, which can significantly improve the hardness and wear resistance of the composite powder; Ni as a binder phase ensures good bonding between the powder and the matrix and between the phases; the addition of B element helps to form boride ceramic phase, further improving the hardness and wear resistance of the coating; Ti element can refine the grain, improve the strength and toughness of the coating; Cr element enhances the corrosion resistance of the coating. The content of each element is accurately optimized to fully exert the synergistic effect of each element, so that the composite powder has excellent comprehensive performance. The hardness of the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles is ≥1000HV, which enables the coating to effectively resist the erosion and wear of hard particles such as sand, significantly improves the anti-erosion-wear performance of the turbine blade, reduces the material loss on the surface of the blade, and prolongs the service life of the blade. The fracture toughness is ≥15MPa·m 1 / 2 , which can effectively avoid the generation and propagation of cracks when the coating is subjected to external force, improve the anti-cracking ability of the coating, and ensure the integrity of the coating under complex stress conditions, thereby ensuring that the coating can function stably for a long time. The melting point is higher than 1400℃, which enables the composite powder to maintain stable performance during laser cladding and is not prone to phase change or decomposition, which is conducive to forming a coating structure with excellent performance and can also adapt to the high energy input environment of high-speed laser cladding. The particle size is 50 to 200μm, which can ensure the flowability and spreadability of the powder during laser cladding, is conducive to forming a uniform and dense coating, improves the bonding strength between the coating and the substrate, reduces the defects in the coating, and further improves the overall performance of the coating. The content of boride ceramic phase is ≥70%, which endows the composite powder with excellent hardness and wear resistance, and is one of the key factors for the coating to have good anti-erosion-wear performance, which can significantly improve the service life of the turbine blade in harsh working environment.

[0033] Further, the mechanical ball milling speed is 100 to 300r / min, which can fully mix the matrix phase and the reinforcing phase, achieve uniform powder refinement, and at the same time avoid overheating, oxidation or introduction of too much impurities due to too high speed, which affects the performance of the powder. Suitable speed is conducive to ensuring the uniformity and quality of the cermet composite powder, laying a foundation for preparing high-performance coatings. The ball-to-material ratio is (1 to 5):1, which can ensure that the powder is subjected to sufficient impact and grinding during ball milling, so that the powder is fully mixed and refined, while avoiding problems such as low ball milling efficiency, powder agglomeration or intensified equipment wear due to too large ball-to-material ratio, improving the stability and efficiency of the ball milling process, and reducing production costs.

[0034] Further, the high-speed laser cladding technology has low energy input, which can avoid problems such as overheating, deformation and cracking of the coating caused by excessive energy, while ensuring that the powder can be fully melted and form a good metallurgical bond with the substrate to obtain a high-quality coating. Suitable energy density helps to optimize the organizational structure and performance of the coating, and improve the anti-erosion-wear performance and corrosion resistance of the coating. The laser power is 1000-3000W, which can meet the energy requirements for powder melting and bonding with the substrate, and can be flexibly adjusted according to different powder characteristics and coating requirements. Suitable laser power can ensure the stability and controllability of the cladding process, improve the quality and consistency of the coating. The laser scanning speed is ≥5000mm / min, which can significantly improve the cladding efficiency, shorten the processing time and reduce the production cost. At the same time, the fast scanning speed helps to reduce the heat-affected zone, reduce the adverse effects on the performance of the substrate, ensure good bonding between the coating and the substrate, and improve the overall performance and service life of the coating.

[0035] Further, the cermet composite powder is vacuum dried at 120-200℃ for 0.5-3h, which can effectively remove the water and impurities in the powder, avoid defects such as pores and cracks caused by water evaporation during the laser cladding process, improve the density and quality of the coating, and ensure good bonding between the coating and the substrate, thereby improving the performance and reliability of the coating. The surface of the pre-processed water turbine blade is subjected to laser scanning preheating treatment, which can reduce the temperature gradient between the substrate and the powder, reduce the thermal stress during the cladding process, and effectively avoid the occurrence of coating cracking. At the same time, the preheating treatment can also improve the wettability of the substrate surface, which is beneficial to the spreading of the powder and the bonding with the substrate, and improves the quality and performance of the coating. The laser scanning power is 700-1200W, and the laser scanning speed is 1000-3000mm / min, which can ensure that the substrate surface reaches an appropriate temperature, which can fully play the role of preheating, and will not adversely affect the performance of the substrate due to excessive temperature. By precisely controlling the preheating parameters, the process conditions of the cladding process can be optimized, and the preparation efficiency and quality of the coating can be improved.

[0036] The application also discloses a water turbine blade surface composite coating prepared by the preparation method, and the thickness of the water turbine blade surface composite coating is ≥300μm, which can provide sufficient protection for the water turbine blade, effectively resist erosion and wear, and prolong the service life of the blade. In the long-term operation process, the thicker coating can better resist the erosion of the external harsh environment and reduce the material loss on the surface of the blade. The cladding efficiency is ≥0.6m 2 / h, can significantly shorten the processing time, reduce production cost, improve production efficiency. This has important significance for large-scale water turbine blade repair and protection engineering, can meet the needs of fast and efficient processing in actual production. The hardness is 800~1100HV, so that the coating has excellent anti-erosion-wear performance, can effectively resist the impact and wear of hard particles such as sand, reduce the wear amount of the blade surface, ensure the normal operation of the water turbine. At the same time, the appropriate hardness also helps to improve the fatigue resistance of the coating, prolong the service life of the coating. The corrosion potential is-0.55~-0.42V, which indicates that the coating has good corrosion resistance, can effectively reduce the corrosion rate of the water turbine blade in the corrosive environment containing water, impurities and the like, reduce the performance decline and damage of the blade due to corrosion, improve the reliability and safety of the water turbine. The relative erosion wear performance is 10~25, which indicates that the coating has higher anti-erosion-wear ability than the traditional coating, can significantly improve the service life of the water turbine blade in harsh working environment, reduce the maintenance cost. In addition, the content of the large particle reinforcing phase in the multi-level composite coating prepared by the present application is ≥10%, and the average hardness of the coating is ≥800HV, so as to ensure the excellent anti-erosion-wear performance of the coating.

[0037] The application also discloses application of the water turbine blade surface composite coating prepared by the high-speed laser cladding preparation method of the water turbine blade surface composite coating in surface protection of key components of water power generation equipment, and the application of the water turbine blade surface composite coating in surface protection of key components of water power generation equipment has important engineering application value. The composite coating obtained by the preparation method can significantly improve the anti-erosion-wear performance and corrosion resistance of key components of water power generation equipment, such as water turbine blades, effectively prolong the service life, reduce the downtime maintenance time and cost caused by equipment damage, improve the operation efficiency and reliability of water power generation equipment, and ensure the stability of power supply, which has a positive role in promoting the development of the water power generation industry. At the same time, the preparation method is efficient and simple, and is suitable for on-site construction, which provides a new solution for on-site efficient repair of key components of water power generation equipment, and has a wide market application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is a scanning electron microscope photo of the surface and cross section of the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles prepared in the embodiment 2 of the present application, wherein (a) is the surface, and (b) is the cross section;

[0039] Figure 2 It is a cross section scanning electron microscope photo of the water turbine blade surface composite coating prepared in the embodiment 2 of the present application;

[0040] Figure 3The microhardness test results of the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles reinforced phase and the nano / sub-micron autogenous ceramic phase composite nickel-based alloy matrix phase in the surface composite coating of the water turbine blade prepared in Example 2 of the present application;

[0041] Figure 4 The X-ray diffraction pattern of the surface composite coating of the water turbine blade prepared in Example 2 of the present application;

[0042] Figure 5 The electrochemical test results of the surface composite coating of the water turbine blade prepared in Example 2 of the present application;

[0043] Figure 6 The macroscopic cross-section scanning electron microscope photo of the surface composite coating of the water turbine blade prepared in Example 2 of the present application. DETAILED DESCRIPTION

[0044] The technical solutions of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present application.

[0045] In the present application, all the embodiments and preferred embodiments mentioned in the present application can be combined to form new technical solutions, if not specifically stated.

[0046] In the present application, all the technical features and preferred features mentioned in the present application can be combined to form new technical solutions, if not specifically stated.

[0047] In the present application, the percentage (%) or the part refers to the percentage by weight or the weight part relative to the composition, if not specifically stated.

[0048] In the present application, the components or the preferred components thereof mentioned can be combined to form new technical solutions, if not specifically stated.

[0049] In the present application, the numerical range “a~b” represents the abbreviation of any real number combination between a and b, where a and b are both real numbers, if not specifically stated. For example, the numerical range “6~22” represents that all the real numbers between “6~22” have been listed herein, and “6~22” is only the abbreviation of these numerical combinations.

[0050] The lower limit and the upper limit of the range disclosed in the present application can be one or more lower limits and one or more upper limits, respectively.

[0051] In the present invention, the term "and / or" as used herein means any combination of one or more of the associated listed terms and all possible combinations, and includes these combinations.

[0052] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the sequence. Preferably, the reaction method herein is carried out sequentially.

[0053] Unless otherwise specified, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to that described can also be applied in the present invention.

[0054] The present invention provides a high-speed laser cladding preparation method for water turbine blade surface composite coating, comprising the following steps:

[0055] S1, selecting water turbine blade steel as the base material, polishing, cleaning, sandblasting and drying the surface of the base material before coating preparation;

[0056] S2, selecting nano / submicron autogenous ceramic phase composite nickel-based alloy as the base phase of the coating, wherein the mass fraction of Cr is ≥15%, the melting point is ≤1400℃, and the hardness is 250~500HV; the powder particle size is 30~105μm. The nano / submicron autogenous ceramic phase composite nickel-based alloy has good corrosion resistance and plastic toughness to resist the cracking tendency of the coating during the high-speed laser cladding process.

[0057] S3, using MoB powder, Ni2B powder, Ti powder and Cr powder as raw material powder, obtaining mixed powder with uniform distribution of components by ball milling, selecting WC-Co grinding balls, controlling the ball-to-material ratio to be (1~5):1, and carrying out ball milling under argon protection, the ball milling speed is 100~300r / min, the ball milling time is ≥24h; the mixed powder is pre-pressed into a blank and pre-fired, the pre-pressing pressure is ≥40MPa, the pre-firing temperature is 800~1000℃, and the pre-firing time is 20~60min, to obtain a preformed block; then the preformed block is melted and poured in a vacuum induction melting furnace, the vacuum degree is set to ≤3Pa, the melting temperature is 1500~1800℃, and the holding time is ≥20min, to obtain a dense cermet block; then the vacuum electrode induction melting atomization technology is used, the vacuum degree is controlled to ≤10 - 3 Pa, the rotation speed is 5~80r / min, the feeding speed is 3~300mm / min, and the airflow pressure is 2~6MPa, to obtain micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles.

[0058] The micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles as the reinforcing phase of the surface composite coating of the water turbine blade include: Mo content of 35% to 45%, B content of 3% to 5%, Ti content of 1% to 3%, Cr content of 5.5% to 9.5%, and the rest is Ni. The micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles include sub-micron boride ceramic phase and nickel-based metal binder phase; the sub-micron boride ceramic phase content is greater than or equal to 70%, the particle size is 50 to 200 μm, the hardness is greater than or equal to 1000 HV, and the fracture toughness is greater than or equal to 15 MPa·m 1 / 2 , and the melting point is higher than 1400℃.

[0059] S4, the matrix phase is mechanically ball-milled and mixed with the reinforcing phase, and the content of the reinforcing phase needs to be controlled to be 10% to 70%. In the mechanical ball-milling and mixing process, the rotating speed is 100 to 300 r / min, and the ball-to-material ratio is (1 to 5):1, so as to control the uniform mixing of the two powders after ball-milling, and obtain the cermet composite powder, and the nano / sub-micron autogenous ceramic phase composite nickel-based alloy is not deformed and the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles are not broken.

[0060] S5, the high-speed laser cladding technology is used to deposit the cermet composite powder on the surface of the pretreated water turbine blade, and the surface composite coating of the water turbine blade is obtained. The surface composite coating of the water turbine blade includes: the nano / sub-micron autogenous ceramic phase composite nickel-based alloy matrix, the sub-micron ceramic phase reinforced cermet composite particles, and the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles reinforced composite coating.

[0061] Before the high-speed laser cladding, the surface of the blade to be repaired is subjected to laser scanning preheating treatment, the laser scanning power is 700 to 1200 W, and the laser scanning speed is 1000 to 3000 mm / min, so as to reduce the cracking tendency of the surface coating in the high-speed cladding process.

[0062] In the high-speed laser cladding process, the laser power is 1000 to 3000 W, the laser scanning speed is greater than or equal to 5000 mm / min, and the overlapping rate is greater than or equal to 70%.

[0063] Before the high-speed laser cladding, the cermet composite powder needs to be subjected to vacuum drying treatment at 120 to 200℃ for 0.5 to 3 h, so as to eliminate the residual moisture in the powder.

[0064] In the surface composite coating of the water turbine blade, the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles are only partially melted in the surface layer and are uniformly dispersed in the nano / sub-micron autogenous ceramic phase composite nickel-based alloy, small-size powder is melted and then small-scale reinforcing particles are precipitated to improve the strength and toughness of the coating matrix.

[0065] The surface composite coating of the water turbine blade prepared by the method has a large-scale cermet particle and a small-scale hard phase particle multi-level composite reinforcing structure (as shown in Figure 1 and Figure 2 The coating has a thickness of ≥300 μm, a cladding efficiency of ≥0.6 m 2 / h, and no obvious crack defects on the coating surface; the average hardness of the coating is 800-1100 HV, the corrosion potential is -0.55--0.42 V, and the relative erosion and wear performance is 10-25, and the anti-erosion and wear performance is improved by more than 10 times compared with the blade substrate.

[0066] The surface composite coating of the water turbine blade disclosed by the application is an erosion and wear protective coating for a sand-containing liquid environment, and needs to resist the erosion and corrosion of water flow and sand, so the impact resistance of the coating is required to be higher; the surface composite coating of the water turbine blade has a multi-level reinforced particle composite structure for resisting erosion and wear, and includes a large-scale Mo-Ni-B-Ti-Cr cermet reinforcing phase for reinforcing the nickel-based alloy, and a small-scale ceramic particle reinforcing composite structure inside the large-scale reinforcing phase; through the multi-level reinforced composite, the cladding stress can be effectively reduced, the high-speed cladding cracking problem can be prevented, the sand impact resistance of the coating can be improved, and the high anti-erosion and wear performance can be ensured; through the coating structure and the powder design, in the high-speed laser cladding coating preparation process, the synchronous pulse laser heating and other auxiliary means are avoided, the requirement for the cladding equipment is lower, and the on-site processing applicability is better.

[0067] To make the purpose, technical solutions, and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are some embodiments of the application, rather than all the embodiments. The components of the embodiments of the application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the application.

[0068] Embodiment 1

[0069] A high-speed laser cladding preparation method of a surface composite coating of a water turbine blade, comprising the following steps:

[0070] 1) Taking a 17-4PH stainless steel plate as a substrate, polishing, cleaning, and sand blasting the surface of the substrate to obtain a clean metal surface, and performing drying treatment.

[0071] 2) Select spherical Ni45 alloy powder as the base phase of the coating, the Cr content is 15%, the melting point is 1080℃, the hardness is 500 HV, and the average particle size of the powder is 105μm.

[0072] 3) Use vacuum electrode induction melting atomization method to prepare micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles as the composite reinforcing phase of the coating, the composition includes: Mo content is 35%, B content is 3%, Ti content is 1%, Cr content is 5.5%, and the rest is Ni. The sub-micron boride ceramic phase content in the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles is 70%, the hardness is 1000HV, the fracture toughness is 18MPa·m 1 / 2 , the melting point is 1400℃, and the average particle size is 200μm.

[0073] The steps for preparing micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles by vacuum electrode induction melting atomization method include:

[0074] 31) Metal ceramic bulk pre-sintering

[0075] Control the pre-pressing pressure to be 50MPa; the pre-sintering temperature is 800℃; the pre-sintering time is 60min;

[0076] 32) Metal ceramic bulk densification

[0077] Control the vacuum degree to be 3Pa, the melting temperature is 1500℃, and the holding time is 20min;

[0078] 33) Atomization powdering

[0079] Control the vacuum degree to be 10 -3 Pa, control the rotating speed to be 5r / min, the feeding speed to be 3mm / min, and the air flow pressure to be 6MPa, to obtain micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles.

[0080] 4) Weigh the Ni45 base phase powder and micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles with a mass ratio of 9:1, use mechanical ball milling method to mix, the ball milling speed is 100r / min, and the ball-to-material ratio is 5:1, to obtain cermet composite powder with uniform mixing and good sphericity.

[0081] 5) Before high-speed laser cladding, set the laser scanning power to be 700W and the laser scanning speed to be 1000mm / min, to perform laser scanning preheating treatment on the surface of the stainless steel blade; at the same time, bake the cermet composite powder at 120℃ for 3h for drying treatment.

[0082] 6) Using high-speed laser cladding equipment, set the laser power to 1000 W, the scanning speed to 5000 mm / min, the powder feeding rate to 0.5 r / min, and the interpass overlap rate to 70%, deposit the cermet composite powder on the surface of the preheated substrate to obtain the composite coating on the surface of the water turbine blade.

[0083] The average thickness of the composite coating on the surface of the water turbine blade prepared in this embodiment 1 is about 300 μm, the cladding efficiency is 0.6 m 2 / h, which is composed of Mo-Ni-B-Ti-Cr cermet particles and a nickel matrix, the average hardness of the coating is 800 HV, the salt water corrosion resistance is better than that of the substrate, the corrosion potential is-0.55 V, and the erosion-wear resistance is 10 times higher than that of the substrate.

[0084] Embodiment 2

[0085] A high-speed laser cladding method for preparing a composite coating on the surface of a water turbine blade, comprising the following steps:

[0086] 1) Taking 17-4PH stainless steel plate as the substrate, the surface of the substrate is polished, cleaned and sand blasted to obtain a clean metal surface, and then dried.

[0087] 2) Selecting nickel-based 718 alloy powder as the coating matrix phase, the Cr content is 18%, the melting point is 1300℃, the hardness is 400 HV, and the powder particle size is 30 μm.

[0088] 3) Using vacuum electrode induction melting atomization method to prepare micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles as the coating composite reinforcing phase, the composition includes: Mo content is 40%, B content is 3.6%, Ti content is 2%, Cr content is 9.5%, and the rest is Ni. The content of sub-micron boride ceramic phase in micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles is 80%, the hardness is 1048 HV, the fracture toughness is 17 MPa·m 1 / 2 , the melting point is 1480℃, and the average particle size is 105 μm (such as Figure 1 ).

[0089] The steps of preparing micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles by vacuum electrode induction melting atomization method, comprising:

[0090] 31) Pre-sintering of cermet block

[0091] The pre-pressing pressure is controlled to be 40 MPa; the pre-sintering temperature is 1000℃; and the pre-sintering time is 20 min;

[0092] 32) Densification of cermet block

[0093] The vacuum level was controlled at 1 Pa, the melting temperature was 1600℃, and the holding time was 25 min.

[0094] 33) Atomization powder production

[0095] Control vacuum level 10 -4 Micron-sized spherical Mo-Ni-B-Ti-Cr metal-ceramic composite particles were prepared by controlling the rotation speed at 40 r / min, the feed speed at 130 mm / min, and the airflow pressure at 2 MPa.

[0096] 4) Weigh nickel-based 718 alloy powder with a mass ratio of 5:5 and micron-sized spherical Mo-Ni-B-Ti-Cr metal-ceramic composite particles, and mix them by mechanical ball milling at a speed of 300 r / min and a ball-to-material ratio of 3:1 to obtain uniformly mixed metal-ceramic composite powder with good sphericity.

[0097] 5) Before high-speed laser cladding, the laser scanning power is set to 900W and the laser scanning rate is 2000mm / min. Laser scanning preheating treatment is performed on the surface of stainless steel blades. At the same time, the metal-ceramic composite powder is baked at 200℃ for 0.5h for drying treatment.

[0098] 6) Using a high-speed laser cladding equipment, with a laser power of 2000W, a scanning rate of 8000mm / min, a powder feeding rate of 0.5r / min, and an inter-pass overlap rate of 80%, metal-ceramic composite powder is deposited on the surface of the preheated substrate to obtain a composite coating on the surface of the turbine blade.

[0099] The average thickness of the composite coating on the turbine blade surface prepared in Example 2 is approximately 500 μm, and the cladding efficiency is 0.7 μm. 2 / h, the microstructure exhibits a multi-level complex structure (such as Figure 2 The main phase composition is Mo2NiB2 and Ni-based solid solution, and the average hardness of the coating is 950 HV (e.g., Figure 4 Its resistance to salt water corrosion is superior to that of the substrate (such as...). Figure 5 Its corrosion potential is -0.53V, and its erosion and wear resistance is 20 times higher than that of the substrate.

[0100] Figure 1 The images show scanning electron microscope (SEM) images of the surface and cross-section of the micron-sized spherical Mo-Ni-B-Ti-Cr metal-ceramic composite particles prepared in Example 2 of this invention; where (a) is the surface and (b) is the cross-section. As can be seen from the images, the micron-sized spherical Mo-Ni-B-Ti-Cr metal-ceramic composite particles are spherical, and the powder contains a bright white submicron-sized boride ceramic phase, with the remainder being a nickel-based metal binder phase.

[0101] Figure 2 Figure 2 is a cross-sectional scanning electron microscope photograph of the surface composite coating of the water turbine blade prepared in Example 2 of the present application; as can be seen from the figure, the surface composite coating of the water turbine blade is composed of large-scale micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particle reinforced phase and nanometer / sub-micron autogenous ceramic phase composite nickel-based alloy matrix phase, the reinforced phase includes small-scale sub-micron Mo2NiB2 ceramic phase and nickel-based metal binder phase, and the nanometer / sub-micron autogenous ceramic phase composite nickel-based alloy matrix phase of the surface composite coating of the water turbine blade is composed of nickel-based alloy and small-scale ceramic particles, presenting a multi-level composite reinforced structure.

[0102] Figure 3 Figure 4 is a microhardness test result of the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particle reinforced phase and the nanometer / sub-micron autogenous ceramic phase composite nickel-based alloy matrix phase in the surface composite coating of the water turbine blade prepared in Example 2 of the present application; as can be seen from the figure, the hardness of the reinforced phase is higher, and the hardness of the matrix phase is lower, and the composite structure of the two can ensure good erosion wear resistance and comprehensive mechanical properties of the coating.

[0103] Figure 4 Figure 5 is an X-ray diffraction pattern of the surface composite coating of the water turbine blade prepared in Example 2 of the present application; as can be seen from the figure, the prepared surface composite coating of the water turbine blade is mainly composed of Mo2NiB2 ceramic phase and nickel-based alloy phase.

[0104] Figure 5 Figure 6 is an electrochemical test result of the surface composite coating of the water turbine blade prepared in Example 2 of the present application; as can be seen from the figure, the corrosion resistance of the prepared surface composite coating of the water turbine blade is obviously superior to that of the 17-4PH stainless steel substrate.

[0105] Figure 6 Figure 7 is a macroscopic cross-sectional scanning electron microscope photograph of the surface composite coating of the water turbine blade prepared in Example 2 of the present application; abscissa: E / V vs SCE; E represents electrode potential, V represents unit volt, vs SCE represents potential relative to saturated calomel electrode, SCE represents saturated calomel electrode (Saturated Calomel Electrode, SCE), which is used to measure the potential of the electrode in the electrochemical system and reflects the trend of the electrode reaction. Ordinate: lg I / A cm -2 ; lg I represents the logarithmic value of current density; I represents current; A cm -2The current density unit, i.e. the current passing through the electrode per unit area, can be more clearly shown by taking the logarithm to show the difference in current change at different potentials, facilitating the analysis of the electrochemical behavior of the electrode such as corrosion and passivation. As can be seen from the figure, the thickness of the composite coating on the surface of the turbine blade is about 500 μm, and the structure is uniform without obvious cracks and other defects.

[0106] Example 3

[0107] A high-speed laser cladding method for preparing a composite coating on the surface of a turbine blade, comprising the following steps:

[0108] 1) Taking 17-4PH stainless steel plate as the base material, the surface of the base material is polished, cleaned and sand blasted to obtain a clean metal surface, and then dried.

[0109] 2) Selecting nickel-based 718 alloy powder as the coating matrix phase, the Cr content is 18%, the melting point is 1300℃, the hardness is 400 HV, and the powder particle size is 55 μm.

[0110] 3) Using vacuum electrode induction melting atomization method to prepare micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles as the coating composite reinforcing phase, the composition includes: Mo content of 40%, B content of 3.6%, Ti content of 2%, Cr content of 9.5%, and the rest is Ni. The micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles contain 80% of sub-micron boride ceramic phase, the hardness is 1048HV, the fracture toughness is 17MPa·m 1 / 2 , the melting point is 1480℃, and the average particle size is 50 μm.

[0111] The steps of preparing micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles by vacuum electrode induction melting atomization method, comprising:

[0112] 31) Metal ceramic bulk pre-sintering

[0113] The pre-pressing pressure is controlled to be 45MPa, the pre-sintering temperature is 900℃, and the pre-sintering time is 40min;

[0114] 32) Metal ceramic bulk densification

[0115] The vacuum degree is controlled to be 1Pa, the melting temperature is 1800℃, and the holding time is 20min;

[0116] 33) Atomization powdering

[0117] The vacuum degree is controlled to be 10 -4Pa, the control rotation speed is 80 r / min, the feeding speed is 300 mm / min, the control airflow pressure is 5.5 MPa, and micron-level spherical Mo-Ni-B-Ti-Cr cermet composite particles are prepared.

[0118] 4) The nickel-based 718 alloy powder and the micron-level spherical Mo-Ni-B-Ti-Cr cermet composite particles with a mass ratio of 7:3 are weighed, and a mechanical ball milling method is used for mixing, the ball milling speed is 250 r / min, and the ball-to-material ratio is 4:1, to obtain a cermet composite powder that is uniformly mixed and has good sphericity.

[0119] 5) Before high-speed laser cladding, a laser scanning power of 1000 W and a laser scanning speed of 2500 mm / min are set to perform laser scanning preheating treatment on the surface of the stainless steel blade; at the same time, the cermet composite powder is baked at 150 DEG C for 1.5 h for drying treatment.

[0120] 6) A high-speed laser cladding device is used, a laser power of 2000 W, a scanning speed of 10000 mm / min, a powder feeding rate of 0.5 r / min, and a interpass overlap rate of 85% are set to deposit the cermet composite powder on the surface of the preheated substrate, to obtain a composite coating on the surface of the water turbine blade.

[0121] The average thickness of the composite coating on the surface of the water turbine blade prepared in this embodiment 3 is about 550 μm, the cladding efficiency is 0.78 m 2 / h, presents a multi-level composite structure, the main phase components are Mo2NiB2 and Ni-based solid solution, the average hardness of the coating is 850 HV, the salt water corrosion resistance is better than that of the substrate, the corrosion potential is-0.48 V, and the erosion-wear resistance is improved by 18 times compared with the substrate.

[0122] Embodiment 4

[0123] A high-speed laser cladding method for preparing a composite coating on the surface of a water turbine blade, comprising the following steps:

[0124] 1) A 17-4PH stainless steel plate is used as a substrate, the surface of the substrate is polished, cleaned and sandblasted to obtain a clean metal surface, and drying treatment is performed.

[0125] 2) Spherical nickel-based 625 alloy powder is selected as a coating matrix phase, the Cr content is 22%, the melting point is 1400 DEG C, the hardness is 250 HV, and the powder particle size is 80 μm.

[0126] 3) The micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles are prepared by vacuum electrode induction melting atomization method, as a coating composite reinforcing phase, the composition includes: Mo content is 45%, B content is 5%, Ti content is 3%, Cr content is 6%, and the rest is Ni. The micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles contain 85% of sub-micron boride ceramic phase, the hardness is 1400HV, the fracture toughness is 15MPa·m 1 / 2 , the melting point is 1500℃, and the average particle size is 150μm.

[0127] The steps of preparing micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles by vacuum electrode induction melting atomization method include:

[0128] 31) Metal ceramic bulk pre-sintering

[0129] The pre-pressing pressure is controlled to be 60MPa, the pre-sintering temperature is 850℃, and the pre-sintering time is 30min;

[0130] 32) Metal ceramic bulk densification

[0131] The vacuum degree is controlled to be 2Pa, the melting temperature is 1700℃, and the holding time is 30min;

[0132] 33) Atomization powdering

[0133] The vacuum degree is controlled to be 10 -4 Pa, the rotating speed is controlled to be 65r / min, the feeding speed is controlled to be 200mm / min, the airflow pressure is controlled to be 4.5MPa, and the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles are prepared.

[0134] 4) The Ni45 matrix phase powder and the micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles with a mass ratio of 7:3 are weighed, and a mechanical ball milling method is used for mixing, the ball milling speed is 200r / min, and the ball-to-material ratio is 1:1, to obtain a cermet composite powder with uniform mixing and good sphericity.

[0135] 5) Before high-speed laser cladding, the laser scanning power is set to be 1200W, the laser scanning speed is 3000mm / min, the surface of the stainless steel blade is laser scanned for preheating treatment, and at the same time, the cermet composite powder is baked at 150℃ for 1.5h for drying treatment.

[0136] 6) using high-speed laser cladding equipment, setting the laser power to 3000W, the scanning rate to 11000mm / min, the powder feeding rate to 0.5r / min, and the interpass overlap rate to 85%, depositing the cermet composite powder on the surface of the preheated substrate to obtain the surface composite coating of the water turbine blade.

[0137] The average thickness of the surface composite coating of the water turbine blade prepared in the embodiment 4 is about 400μm, the cladding efficiency is 0.85m 2 / h, which is composed of Mo-Ni-B-Ti-Cr cermet particles and a nickel matrix, the average hardness of the coating is 1100HV, the salt water corrosion resistance is better than that of the substrate, the corrosion potential is-0.42V, and the anti-erosion and wear performance is 25 times higher than that of the substrate.

[0138] In summary, the anti-erosion and wear coating with a multi-level composite structure is prepared by matching the raw material powder design and the high-speed laser cladding technology in the application, which has high hardness and high corrosion resistance and exhibits excellent anti-erosion and wear performance in the silt environment. The important properties of the surface composite coating of the water turbine blade prepared in the above embodiments are shown in the following table.

[0139] Table 1 Comparison of properties of the substrate and the surface composite coating of the water turbine blade prepared in embodiments 1~4

[0140]

[0141] Table 1 is a comparison of properties of the substrate and the surface composite coating of the water turbine blade prepared in embodiments 1~4; from the table, it can be seen that the hardness of the surface composite coating of the water turbine blade prepared in the application is 800~1100HV; the corrosion potential is-0.55~-0.42V; the relative erosion and wear performance is 10~25; compared with the stainless steel substrate, the surface composite coating of the water turbine blade exhibits higher hardness and corrosion resistance, and the anti-erosion and wear performance is improved by more than one order of magnitude, which has good applicability in the field of water turbine blade surface protection.

[0142] In summary, the water turbine blade surface composite coating and high-speed laser cladding preparation method and application disclosed by the application, by designing and preparing large-scale micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles with strong and tough composite structure as reinforcing phase, selecting nano / sub-micron autogenous ceramic phase composite nickel-based alloy with good abrasion resistance as matrix phase, and by means of low-energy input high-speed laser cladding rapid deposition technology, a multi-stage composite coating with excellent matching of strength and toughness and corrosion resistance is prepared on the surface of the water turbine blade, which plays a multi-stage shadow protection role in resisting liquid-solid erosion and abrasion, thereby excellent anti-erosion and abrasion performance is achieved. The application can effectively slow down the erosion and abrasion damage of the surface of the water turbine blade, improve its safe service life, and has great application prospect in the field of surface protection of key components of water power generation equipment.

[0143] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A method for preparing a composite coating on the surface of a water turbine blade using high-speed laser cladding, characterized in that, Includes the following steps: The matrix phase and the reinforcing phase were mechanically ball-milled and mixed to obtain a metal-ceramic composite powder; Using high-speed laser cladding technology, metal-ceramic composite powder is deposited on the surface of pretreated turbine blades to obtain a composite coating on the turbine blade surface; The composite coating on the surface of the turbine blades has a multi-level composite reinforcement structure of nano / submicron / micron. The matrix phase of the composite coating on the surface of the turbine blade is a nano / submicron self-generated ceramic phase composite nickel-based alloy, and the reinforcing phase is micron-sized spherical Mo-Ni-B-Ti-Cr metal-ceramic composite particles. The laser power of the high-speed laser cladding technology is 1000~3000W; the laser scanning rate is ≥5000mm / min; and the overlap rate is ≥70%.

2. The high-speed laser cladding method for preparing a composite coating on the surface of a turbine blade according to claim 1, characterized in that, The content of the reinforcing phase in the metal-ceramic composite powder is 10% to 70%.

3. The high-speed laser cladding method for preparing a composite coating on the surface of a turbine blade according to claim 1, characterized in that, In the nano / submicron self-generated ceramic phase composite nickel-based alloy, the mass fraction of Cr is ≥15%; the melting point is ≤1400℃; the hardness is 250~500HV; and the particle size is 30~105μm.

4. The high-speed laser cladding method for preparing a composite coating on the surface of a turbine blade according to claim 1, characterized in that, The micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles contain 35%~45% Mo, 3%~5% B, 1%~3% Ti, 5.5%~9.5% Cr, and the remainder is Ni. The micron-sized spherical Mo-Ni-B-Ti-Cr cermet composite particles comprise a submicron-sized boride ceramic phase and a nickel-based metal binder phase; the submicron-sized boride ceramic phase content is ≥70%, the hardness is ≥1000 HV, and the fracture toughness is ≥15 MPa·m. 1 / 2 Melting point above 1400℃; particle size 50~200μm.

5. The high-speed laser cladding method for preparing a composite coating on the surface of a turbine blade according to claim 1, characterized in that, The micron-sized spherical Mo-Ni-B-Ti-Cr metal-ceramic composite particles were prepared by vacuum electrode induction melting and atomization method. Includes the following steps: MoB powder, Ni2B powder, Ti powder and Cr powder were ball-milled and mixed, and then pre-pressed, pre-fired, melted and cooled to obtain a metal-ceramic bulk. The metal-ceramic bulk was then subjected to vacuum electrode induction melting and atomization to obtain micron-sized spherical Mo-Ni-B-Ti-Cr metal-ceramic composite particles.

6. The high-speed laser cladding method for preparing a composite coating on the surface of a turbine blade according to claim 5, characterized in that, The pre-compression pressure is ≥40MPa; the pre-firing temperature is 800~1000℃; and the pre-firing time is 20~60min. The melting conditions include: vacuum degree ≤3Pa, melting temperature 1500~1800℃, and holding time ≥20min; The conditions for vacuum electrode induction melting atomization include: vacuum degree ≤ 10. -3 Pa, rotational speed of 5~80 r / min, feed speed of 3~300 mm / min, and airflow pressure of 2~6 MPa.

7. The high-speed laser cladding method for preparing a composite coating on the surface of a turbine blade according to claim 1, characterized in that, The mechanical ball mill operates at a speed of 100-300 r / min and a ball-to-material ratio of (1-5):

1.

8. The high-speed laser cladding method for preparing a composite coating on the surface of a turbine blade according to claim 1, characterized in that, Before high-speed laser cladding, the process also includes: vacuum drying the metal-ceramic composite powder at 120~200℃ for 0.5~3 hours; Before high-speed laser cladding, the process also includes: laser scanning preheating treatment of the pretreated turbine blade surface; the laser scanning power is 700~1200W, and the laser scanning rate is 1000~3000mm / min.

9. A composite coating for the surface of a water turbine blade, characterized in that, The composite coating on the surface of the turbine blade is prepared by the high-speed laser cladding method according to any one of claims 1 to 8, wherein the thickness of the composite coating on the surface of the turbine blade is ≥300μm. Cladding efficiency ≥ 0.6m 2 / h; hardness is 800~1100HV; corrosion potential is -0.55~-0.42V; The relative erosion wear performance is 10~25.

10. The application of the composite coating on the surface of turbine blades prepared by the high-speed laser cladding method according to any one of claims 1 to 8 in the surface protection of key components of hydropower equipment.

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