A laser cladding high-performance Co-based high-entropy alloy / WC / NbC ceramic composite powder, coating and its preparation method

Abstract

This invention discloses a high-performance Co-based high-entropy alloy / WC / NbC ceramic composite powder, coating, and preparation method thereof, all prepared by laser cladding. The composite powder is primarily composed of a Co-based high-entropy alloy, with the following atomic percentage composition: Co powder: balance; Cr powder: 25-35%; Ni powder: 7-13%; Al powder: 5-8%; Ti powder: 5-8%; Nb powder: 0.5-5%. WC powder: 5-25 wt% and NbC powder: 1-10 wt% are added to this formulation. Using this powder as raw material, laser cladding is applied to the surface of a water turbine workpiece to form a coating of 0.5-10 mm. This coating exhibits a metallurgical bond with the substrate and possesses excellent resistance to abrasion, cavitation erosion, and corrosion. This invention has high production efficiency, higher coating adhesion compared to supersonic thermal spraying technology, and is a metallurgical bonding process, making it more suitable for construction in small spaces. It can produce thicker coatings, and the laser cladding coating is denser, without through holes, preventing corrosion channels and making it more corrosion resistant. It is used to solve the problems of abrasion, cavitation and corrosion on the surface of water turbines.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic equipment coating technology, and relates to a high-performance Co-based high-entropy alloy / WC / NbC ceramic composite powder, coating and preparation method thereof by laser cladding, especially a coating with excellent comprehensive performance of anti-abrasion, anti-cavitation and anti-corrosion, which is suitable for application on the flow-through components of water turbines. Background Technology

[0002] Hydropower generator units are an indispensable component in the redevelopment and utilization of water resources, and their long-term, efficient, and stable operation has a significant impact on society and the economy. For a long time, the surfaces of the flow-through components of hydropower generator units have suffered from abrasion, cavitation, and corrosion. Preliminary statistics indicate that 30-40% of hydropower generator units experience abrasion, cavitation, and corrosion problems. After abrasion, cavitation, and corrosion damage occurs to the flow-through components of the turbine, the surface morphology changes, disrupting the conditions for normal water flow around them, thus affecting the power output and operating efficiency of the equipment. In severe cases, this can generate strong vibrations, noise, and load fluctuations, directly affecting the safety, stability, operating efficiency, and service life of the turbine. This leads to a large number of turbines needing replacement and becoming obsolete, which not only affects the safety of project operation but also results in serious waste of resources and energy, especially posing a significant potential threat to the safe operation of the power station.

[0003] To address the problems of erosion, cavitation, and corrosion damage in hydraulic turbines, domestic and international research institutions and enterprises have conducted extensive research and engineering practices, achieving some progress. Traditional methods mainly include improving the base material of components, metal electrode welding, alloy powder spraying, coating with organic materials, sputtering coating technology, and thermal spraying technology. While these technologies provide technical methods for solving the erosion problem of hydraulic turbines, each has its own drawbacks and is often unsuitable for construction in confined spaces or for preparing thick, high-performance coatings. Therefore, this invention combines laser cladding technology and high-entropy alloy / ceramic composite materials to effectively solve this problem. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of current technical solutions by providing a laser cladding high-performance Co-based high-entropy alloy / WC / NbC ceramic composite powder, coating, and preparation method thereof. This coating possesses excellent anti-abrasion, anti-cavitation, and anti-corrosion properties, exhibiting superior overall performance. The turbine flow components coated with this material can effectively overcome abrasion, cavitation, and corrosion phenomena generated during high-speed operation, preventing a decline in the coating performance of the flow components. Furthermore, this invention allows for construction in a relatively small space and can produce a thicker coating with high performance, which is beneficial for application on turbine surfaces.

[0005] The technical solution adopted in this invention is as follows:

[0006] A high-performance Co-based high-entropy alloy / WC / NbC ceramic composite powder for laser cladding has the following composition: WC powder: 5-25 wt%, NbC powder: 1-10 wt%, and Co-based high-entropy alloy powder: balance; wherein the Co-based high-entropy alloy powder, by atomic percentage, has the following composition: Co powder: balance, Cr powder: 25-35%, Ni powder: 7-13%, Al powder: 5-8%, Ti powder: 5-8%, and Nb powder: 0.5-5%.

[0007] A high-performance Co-based high-entropy alloy / WC / NbC ceramic composite coating is laser-clad, which is prepared on the surface of a substrate by laser cladding using the aforementioned powder formulation as raw material. The preparation method specifically includes the following steps:

[0008] Step 1: Co powder, Cr powder, Ni powder, Al powder, Ti powder, and Nb powder are mixed according to atomic percentages, and Co-based high-entropy alloy powder is prepared by mechanical mixing or gas atomization method, with a particle size of 10-105 μm.

[0009] Step 2: The Co-based high-entropy alloy powder prepared in Step 1 is mixed with WC powder and NbC powder according to the mass percentage, and Co-based high-entropy alloy / WC / NbC ceramic composite powder is prepared by mechanical mixing; the particle size of WC powder is 2-5 μm and the particle size of NbC powder is 1-3 μm.

[0010] Step 3: Spread the prepared Co-based high-entropy alloy / WC / NbC ceramic composite powder separately and place it in an insulated box for drying;

[0011] Step 4: Clean the surface of the substrate with acetone or alcohol and dry it to remove oil stains and dirt.

[0012] Step 5: Set up the laser cladding process to prepare a high-performance Co-based high-entropy alloy / WC / NbC ceramic composite coating.

[0013] In the above scheme, the thickness of the composite coating is further 0.5 to 10 mm.

[0014] Furthermore, in step 3, the heat preservation temperature is 80-100℃, and the drying time is 1-5 hours.

[0015] Furthermore, the drying temperature in step 4 is 50–60°C.

[0016] Furthermore, the laser cladding process parameters in step 4 are as follows: spot diameter is 4-6 mm, laser power is 2.5-4 KW, overlap rate is 40%-60%, cladding head scanning speed is 5-20 mm / s, and powder feeding rate is 15-90 g / min.

[0017] In this invention, the high-entropy alloy exhibits a unique atomic structure, forming a single solid solution or simple eutectic structure from multiple principal elements, resulting in excellent mechanical properties, oxidation resistance, and corrosion resistance. By incorporating ceramic materials into the high-entropy alloy, the coating's resistance to abrasion and cavitation erosion can be further improved. Combined with laser cladding technology, a high-energy-density laser beam is used to fuse the coating with a thin layer on the substrate surface, forming a metallurgically bonded cladding layer on the substrate surface. The prepared coating exhibits a metallurgical bond with the substrate, resulting in high production efficiency. Compared to technologies such as supersonic thermal spraying, the method of this invention is more suitable for small-space construction, allowing for the preparation of high-strength, metallurgically bonded coatings even in confined spaces. It can also produce thicker coatings, such as those up to tens of millimeters thick. In contrast, supersonic thermal spraying is only suitable for coatings with a thickness of <1 mm; excessively thick coatings are prone to cracking and peeling due to stress issues. Compared with other methods such as electroplating and welding, the laser cladding method used in this invention has the advantages of dense structure, good adhesion between the coating and the substrate, suitability for a wide range of cladding materials, and large variation in particle size and content. The combination of laser cladding technology and high-entropy alloy / ceramic composite materials in this invention has significant advantages in solving the erosion problem of hydroelectric generator sets.

[0018] The beneficial effects of this invention are:

[0019] This invention prepares a Co-based high-entropy alloy / ceramic composite coating using laser cladding. The coating's hardness is approximately 25-35% higher than that of ZG06Cr13Ni5Mo steel, a commonly used substrate material for hydraulic turbines; its abrasion resistance is 3-6 times that of ZG06Cr13Ni5Mo; its cavitation erosion resistance is 2-6 times that of ZG06Cr13Ni5Mo; its porosity is less than 0.1%; and its resistance to neutral salt spray corrosion is greater than 480 hours. The coating and substrate have a metallurgical bond. This invention offers high production efficiency and is more suitable for construction in confined spaces compared to supersonic thermal spraying technology. It achieves a metallurgically bonded coating, can produce thicker coatings, and is highly dense, preventing corrosion channels. This invention is used to solve the problems of abrasion, cavitation erosion, and corrosion on the surface of hydraulic turbines.

[0020] The present invention will be further illustrated below with reference to examples. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0022] In this embodiment of the invention, the coating substrate can be Q235 steel, ZG06Cr13Ni5Mo stainless steel, 316L stainless steel, etc. Co-based high-entropy alloy powder is prepared by mechanical mixing or gas atomization, with a particle size of 10-105 μm; WC powder has a particle size of 2-5 μm, and NbC powder has a particle size of 1-3 μm.

[0023] Example 1

[0024] (1) The components were taken according to the atomic ratio: Co powder: balance, Cr powder: 26.3%, Ni powder: 7.1%, Al powder: 5.2%, Ti powder: 5.2%, Nb powder: 1.3%, and Co-based high-entropy alloy coating powder was prepared.

[0025] (2) Take each component by mass percentage: the high entropy alloy powder prepared in step 1: balance, WC powder: 6.8%, NbC powder: 1.1%, and prepare Co-based high entropy alloy / ceramic composite coating powder;

[0026] (3) The Co-based high-entropy alloy / ceramic composite coating powder was laid out separately and placed in an insulated box for drying. The insulated temperature was 90℃ and the drying time was 4 hours.

[0027] (4) Clean the surface of the substrate with acetone or alcohol and dry it in an insulated box at 50-60°C.

[0028] (5) Laser cladding process parameters: spot diameter: 4.2mm, laser power: 2.5KW, overlap rate: 50%, cladding head scanning speed: 8mm / s, powder feeding rate: 20g / min;

[0029] (6) The hardness of the prepared CoCrNiAlTiNb / WC / NbC high-entropy alloy / ceramic composite coating is 565 HV. 0.2 Under the same conditions, the CoCrNiAlTiNb / WC / NbC high-entropy alloy / ceramic composite coating exhibits 3.2 times the anti-wear performance and 5.22 times the cavitation erosion resistance of the base ZG06Cr13Ni5Mo stainless steel. No corrosion was observed after 480 hours of neutral salt spray corrosion.

[0030] Example 2

[0031] (1) The components were taken according to the atomic ratio: Co powder: balance, Cr powder: 26.8%, Ni powder: 8.2%, Al powder: 5.8%, Ti powder: 5.8%, Nb powder: 1.5%, and Co-based high-entropy alloy coating powder was prepared.

[0032] (2) Take each component according to the mass percentage: the high entropy alloy powder prepared in step 1: balance, WC powder: 10%, NbC powder: 2.7%, and prepare Co-based high entropy alloy / ceramic composite coating powder;

[0033] (3) The Co-based high-entropy alloy / ceramic composite coating powder was laid out separately and placed in an insulated box for drying. The insulated temperature was 90℃ and the drying time was 4 hours.

[0034] (4) Clean the surface of the substrate with acetone or alcohol and dry it in an insulated box at 50-60°C to remove oil stains and dirt from the surface.

[0035] (5) Laser cladding process parameters: spot diameter: 4.6mm, laser power: 3.2KW, overlap rate: 50%, cladding head scanning speed: 10mm / s, powder feeding rate: 40g / min;

[0036] (6) The hardness of the prepared CoCrNiAlTiNb / WC / NbC high-entropy alloy / ceramic composite coating is 605 HV. 0.2 Under the same conditions, the CoCrNiAlTiNb / WC / NbC high-entropy alloy / ceramic composite coating exhibits 4.71 times the anti-wear performance and 4.04 times the cavitation erosion resistance of the base ZG06Cr13Ni5Mo stainless steel. No corrosion was observed after 480 hours of neutral salt spray corrosion.

[0037] Example 3

[0038] (1) The components were taken according to the atomic ratio: Co powder: balance, Cr powder: 29.7%, Ni powder: 9.8%, Al powder: 6.4%, Ti powder: 6.4%, Nb powder: 1.7%, and Co-based high-entropy alloy coating powder was prepared.

[0039] (2) Take each component by mass percentage: the high entropy alloy powder prepared in step 1: balance, WC powder: 15.4%, NbC powder: 2.7%, and prepare Co-based high entropy alloy / ceramic composite coating powder;

[0040] (3) The Co-based high-entropy alloy / ceramic composite coating powder was laid out separately and placed in an insulated box for drying. The insulated temperature was 90℃ and the drying time was 4 hours.

[0041] (4) Laser cladding process parameters: spot diameter: 4.3mm, laser power: 3.8KW, overlap rate: 50%, cladding head scanning speed: 15mm / s, powder feeding rate: 65g / min;

[0042] (5) The hardness of the prepared CoCrNiAlTiNb / WC / NbC high-entropy alloy / ceramic composite coating is 678 HV. 0.2 Under the same conditions, the CoCrNiAlTiNb / WC / NbC high-entropy alloy / ceramic composite coating exhibits 5.16 times the anti-wear performance and 3.12 times the cavitation erosion resistance of the base ZG06Cr13Ni5Mo stainless steel. No corrosion was observed after 480 hours of neutral salt spray corrosion.

[0043] The embodiments described above are merely some preferred embodiments of the present invention, and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A high-performance Co-based high-entropy alloy / WC / NbC ceramic composite coating for laser cladding, characterized in that, The composite powder composition is as follows: Co-based high-entropy alloy coating powder was prepared according to the atomic ratio of Co powder: balance, Cr powder: 26.3%, Ni powder: 7.1%, Al powder: 5.2%, Ti powder: 5.2%, and Nb powder: 1.3%. Then, according to the mass percentage of the high-entropy alloy coating powder: balance, WC powder: 6.8%, and NbC powder: 1.1%. Alternatively, a Co-based high-entropy alloy coating powder can be prepared by using the atomic ratios of Co powder: balance, Cr powder: 26.8%, Ni powder: 8.2%, Al powder: 5.8%, Ti powder: 5.8%, and Nb powder: 1.5%; then, by mass percentage, the high-entropy alloy coating powder is used as follows: balance, WC powder: 10%, and NbC powder: 2.7%. Alternatively, a Co-based high-entropy alloy coating powder can be prepared according to the atomic ratio of Co powder: balance, Cr powder: 29.7%, Ni powder: 9.8%, Al powder: 6.4%, Ti powder: 6.4%, and Nb powder: 1.7%; then, according to the mass percentage, the high-entropy alloy coating powder is taken as follows: balance, WC powder: 15.4%, and NbC powder: 2.7%. The WC powder has a particle size of 2-5 μm, and the NbC powder has a particle size of 1-3 μm. The composite coating is obtained by laser cladding based on the composite powder. The laser cladding process parameters are: spot diameter of 4~6mm, laser power of 2.5~4KW, overlap rate of 40%~60%, cladding head scanning speed of 5~20mm / s, and powder feeding rate of 15~90g / min. The resulting composite coating was subjected to neutral salt spray corrosion for 480 hours without corrosion.

2. The method for preparing a laser-clad high-performance Co-based high-entropy alloy / WC / NbC ceramic composite coating as described in claim 1, characterized in that, First, Co-based high-entropy alloy powder is prepared, and then mixed with ceramic powder, including the following steps: Step 1: Co powder, Cr powder, Ni powder, Al powder, Ti powder, and Nb powder are mixed according to atomic percentages, and Co-based high-entropy alloy powder is prepared by mechanical mixing or gas atomization method, with a particle size of 10~105μm; Step 2: The Co-based high-entropy alloy powder prepared in Step 1 is mixed with WC powder and NbC powder according to the mass percentage, and Co-based high-entropy alloy / WC / NbC ceramic composite powder 1 is prepared by mechanical mixing; the particle size of WC powder is 2~5μm and the particle size of NbC powder is 1~3μm. Step 3: Spread the prepared Co-based high-entropy alloy / WC / NbC ceramic composite powder separately and place it in an insulated box for drying; Step 4: Clean the surface of the substrate with acetone or alcohol and dry it to remove oil stains and dirt. Step 5: Set up the laser cladding process. The laser cladding process parameters are: spot diameter 4~6mm, laser power 2.5~4KW, overlap rate 40%~60%, cladding head scanning speed 5~20mm / s, powder feeding rate 15~90g / min, to prepare a high-performance Co-based high-entropy alloy / WC / NbC ceramic composite coating by laser cladding.

3. The preparation method according to claim 2, characterized in that, The thickness of the composite coating is 0.5~10mm.

4. The preparation method according to claim 2, characterized in that, In step 3, the heat preservation temperature is 80~100℃, and the drying time is 1~5 hours.

5. The preparation method according to claim 2, characterized in that, The drying temperature in step 4 is 50~60℃.