Method for improving abrasion and erosion resistance of impulse runner

Abstract

The present invention relates to the technical field of the production and manufacturing of impulse runners, and discloses a method for improving the abrasion and erosion resistance of an impulse runner. The method comprises the following steps: S1, milling an area prone to abrasion and erosion on an impulse runner to form a filling area; S2, filling the filling area with high-strength abrasion- and erosion-resistant martensitic stainless steel that serves as a filling material, and performing laser cladding; S3, machining laser-cladded positions to conform to the profile of the impulse runner; S4, performing an aging treatment on the machined runner at a temperature lower than the initial austenite transformation temperature (Ac1); and S5, polishing the surface of the aged impulse runner until the surface is smooth. The present invention can effectively improve the surface strength, hardness, and abrasion and erosion resistance of an impulse runner.

Description

A method for improving the wear and corrosion resistance of impact impellers Technical Field

[0001] This invention relates to the field of impact wheel manufacturing technology, and in particular to a method for improving the wear and corrosion resistance of impact wheels. Background Technology

[0002] Impact impellers are subjected to the cyclic impact of high-speed water flow during operation, with wear and cavitation being the two main material loss mechanisms. Due to the high kinetic energy and impact force of the water flow in impact impellers, wear patterns along the water flow direction are typically formed on the impeller surface during service, especially in impellers operating in waters with high sediment content, where the wear on the flow surface is more severe. Besides wear, cavitation is also a major form of surface failure in impact impellers. As water flows through different regions of the flow surface, its fluid pressure changes significantly. When high-pressure water flows through low-pressure flow areas, cavitation occurs, forming numerous bubbles in the water flow. When the water flows through a high-pressure area again, these bubbles annihilate, simultaneously generating localized high-pressure jets that impact the impeller's flow surface. Under the repeated impact of these high-pressure jets, the impeller surface is fatigued, forming honeycomb-like cavitation pits. Typically, wear and cavitation in impact impellers occur simultaneously, and the combined effect of these two mechanisms dramatically accelerates the surface erosion rate of the impeller. When the surface of the impact runner is severely eroded, it will affect the force of the water flow, and thus affect the mechanical stability of the generator set. When the runner is eroded too much, it may even threaten the safety of the runner structure, thus creating a safety hazard.

[0003] Currently, with the continuous increase in the design capacity of single impulse turbine generator units, the impact loads on the impulse runners during service are also increasing, and correspondingly, the wear and cavitation problems of the impulse runners are becoming more and more serious. Nowadays, using martensitic stainless steel to manufacture impulse runners can no longer meet the wear and corrosion resistance requirements of large-capacity units during service.

[0004] Therefore, it is necessary to design a scheme to improve the wear and corrosion resistance of impact rollers. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the wear and corrosion resistance of impact rollers, which can effectively improve the surface strength, hardness and wear and corrosion resistance of impact rollers, in order to address the problems mentioned above.

[0006] The technical solution adopted in this invention is as follows: A method for improving the wear and corrosion resistance of impact impellers, comprising the following steps:

[0007] S1: Milling is performed on the easily worn areas of the impact wheel to form a filling area;

[0008] S2: High-strength, wear-resistant, and corrosion-resistant martensitic stainless steel is used as the filler material to fill the filling area, and laser cladding is performed;

[0009] S3: Machin the laser cladding position to match the profile of the impact wheel;

[0010] S4: Aging treatment is performed on the machined impeller at a temperature below the initial temperature of austenite transformation (Ac1);

[0011] S5: Polish the surface of the impact wheel after aging treatment until smooth.

[0012] Furthermore, in step S1, it is necessary to determine the easily worn areas on the impact wheel.

[0013] Furthermore, when determining the easily worn areas, the easily worn areas on the model are theoretically calculated based on the model of the impact wheel, and the easily worn areas are marked on the actual impact wheel according to the location of the easily worn areas on the model.

[0014] Furthermore, the number of easily abraded areas is four.

[0015] Furthermore, in step S2, the composition of the high-strength, wear-resistant, and corrosion-resistant martensitic stainless steel includes the following elements in mass percentage:

[0016] C (0-0.03%); Cr (11.5%-14.0%); Ni (7.5%-9.5%); Cu (1.0%-2.5%); Nb (0.3%-0.6%); Ti (0.5%-1.4%); Mo (0.1%-0.3%); Mn (0.1%-0.3%); Si (0.1%-0.3%); Al (0.1%-0.3%); P (0-0.04%); S (0-0.03%); O (0-0.04%); N (0-0.04%); the remainder being Fe and unavoidable impurity elements.

[0017] Furthermore, in step S2, the power of the laser cladding is 15000W.

[0018] Furthermore, in step S2, the laser cladding rate is 600 mm / min.

[0019] Furthermore, in step S2, the overlap rate of laser cladding is 50%.

[0020] Furthermore, in step S4, the aging treatment temperature is 460℃~520℃, the aging time is 3h~4h, and the cooling method is air cooling.

[0021] Furthermore, in step S5, during grinding, the surface of the impact wheel is considered smooth after reaching the designed roughness.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] 1. By laser cladding wear-resistant alloy materials in the wear-prone areas of the impeller and precipitating dispersed nano-precipitates (Al2Cu and Ni3Al) in the surface laser cladding layer through aging treatment, the surface strength, hardness and wear resistance of the impact impeller can be significantly increased, thereby enabling the impact impeller to meet the wear resistance performance requirements.

[0024] 2. The wear-resistant alloy powder of the present invention contains reinforcing alloying elements such as Ti and Nb, thereby improving the material hardness and wear resistance; in addition, the Cu, Al, Ni and other elements contained therein can easily form nanoparticle reinforcing phases, thereby further improving the strength and surface wear resistance of the components. Attached Figure Description

[0025] The present invention will be described by way of example and with reference to the accompanying drawings, wherein:

[0026] Figure 1 shows the distribution of easily worn areas on the flow surface of the impact impeller.

[0027] Figure 2 shows the dimensions and schematic diagram of the erosion test sample;

[0028] Figure 3 shows the erosion experiment process (45° angle erosion);

[0029] Figure 4 shows the erosion experiment process (90° angle erosion). Embodiments of the present invention

[0030] In the description of this specification, it should be noted that if terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," or "outer" appear to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, they are only for the convenience of describing this specification and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this specification.

[0031] Furthermore, the use of terms such as "horizontal" or "vertical" in this specification does not imply that the component must be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0032] In the description of this specification, it should also be noted that, unless otherwise expressly specified and limited, the terms “set up,” “install,” “connect,” and “link” should be interpreted broadly. For example, a link can be a fixed link, a detachable link, or an integral link; it can be a mechanical link or an electrical link; it can be a direct link or an indirect link through an intermediate medium; it can be a connection within two components.

[0033] A method for improving the wear and corrosion resistance of an impact impeller includes the following steps:

[0034] S1: Based on the model of the impact wheel, the easily worn areas on the model are theoretically calculated, and the easily worn areas are marked on the impact wheel entity according to the location of the easily worn areas on the model, thus completing the determination of the easily worn areas on the impact wheel; the easily worn areas on the impact wheel are milled to form filling areas.

[0035] It should be noted that there are four easily worn areas. The morphology and location distribution of these easily worn areas on the impact impeller are shown in Figure 1, as detailed below:

[0036] (1) Water bucket notch and water cutting edge area, characterized by wear at the notch;

[0037] (2) The water-split blade area is characterized by inward-facing wave-like erosion;

[0038] (3) The area near the water outlet at the root of the water bucket is characterized by directional pitting, raindrop erosion and cavitation;

[0039] (4) The upper part of the water bucket is close to the water outlet, characterized by scale-like erosion that matches the flow direction.

[0040] S2: High-strength, wear-resistant, and corrosion-resistant martensitic stainless steel is used as the filler material in four filling areas, followed by laser cladding; the laser cladding power is 15000W, the speed is 600mm / min, and the overlap rate is 50%; and among them:

[0041] The composition of high-strength, wear-resistant, and corrosion-resistant martensitic stainless steel includes the following elements in the following mass percentages:

[0042] C(0-0.03%); Cr(11.5%-14.0%); Ni(7.5%-9.5%); Cu(1.0%-2.5%); Nb(0.3%-0.6%); Ti(0.5%-1.4%); Mo (0.1%-0.3%); Mn (0.1%-0.3%); Si (0.1%-0.3%); Al (0.1%-0.3%); P (0-0.04%); S (0-0.03%); O (0-0.04%) N (0-0.04%); the remainder is Fe and unavoidable impurity elements; preferably, C: 0.02%; Cr: 12.5%; Ni: 8.6%; Cu: 1.5%; Nb: 0.5%; Ti: 0.8%; Mo: 0.23%; Mn: 0.24%; Si: 0.27%; Al: 0.15%; P: 0.009%; S: 0.005%; O: 0.023%; N: 0.007%, wherein P, S, and N are impurity elements, and the remainder is Fe.

[0043] S3: Machin the laser cladding position to match the profile of the impact wheel.

[0044] S4: The processed impeller is aged at a temperature below the initial austenite transformation temperature (Ac1); the aging temperature is 460℃~520℃, the aging time is 3h~4h, and the cooling method is air cooling; the preferred aging temperature is 480℃ and the holding time is 4h.

[0045] S5: Polish the surface of the impact wheel after aging treatment until it is smooth. During polishing, the surface of the impact wheel is considered smooth after it reaches the designed roughness.

[0046] In this embodiment, a flat plate component is used for laser cladding, aging treatment and wear resistance testing; the flat plate component that has undergone laser cladding and aging treatment is machined and polished to prepare an erosion test sample, and the size diagram of the erosion test sample is shown in Figure 2; and the erosion test sample is subjected to erosion test.

[0047] Specifically, the thickness of the cladding layer formed by laser cladding is 2.5 mm. To compare the wear resistance of traditional impeller materials without laser cladding and aging treatment, impact samples with the same dimensions as shown in Figure 2 were prepared. One type consisted of samples after laser cladding and aging treatment, while the other consisted of the substrate without laser cladding and aging treatment. The erosion test equipment was developed by the Institute of Metal Research, Chinese Academy of Sciences. The erosion test relies on the high-speed scouring of sand-laden water, thus involving important parameters such as sand content, sand hardness, sand particle size, water flow velocity, and scouring angle. Based on the actual working conditions of the impact impeller, the sand in the experimental sand-laden water flow was selected as 400-mesh quartz sand (approximately 38 micrometers); the water flow velocity on the scouring surface was 65.5 m / s; and the scouring angle was selected based on the difference in impact angle at different positions on the flow surface of the impact impeller, with two typical scouring angles of 45° and 90° (as shown in Figures 3 and 4). The erosion time for each sample was 8 hours.

[0048] For characterizing the abrasion resistance of samples, the commonly used method in the industry is the gravimetric method. This involves ultrasonically cleaning and drying the sample before testing and recording its mass. After testing, the sample is cleaned, dried, and weighed again. The difference in mass before and after testing is used to describe the relative abrasion resistance of the sample. The erosion resistance test results for samples that have undergone laser cladding and aging treatment, and for substrates that have not undergone laser cladding and aging treatment, are shown in Tables 1 and 2.

[0049] Table 1. Erosion test results of the samples after laser cladding and aging treatment

[0050]

[0051] Table 2. Results of erosion tests on the matrix samples

[0052]

[0053] As shown in Tables 1 and 2, the erosion resistance test results at 45° and 90° show that the laser-clad and aged samples have 1.32 times and 1.91 times the wear resistance of the substrate, respectively. The erosion resistance of the cladding layer is higher than that of the substrate without laser cladding and aging treatment, indicating that the "plowing" and "micro-cutting" behavior of impact particles has a more significant effect on the low-hardness substrate. At a 90° angle of attack, the difference in wear resistance between the cladding layer and the substrate is even greater because there are no velocity and force components during 90° erosion, thus allowing the high hardness and ultra-wear-resistant characteristics of the cladding layer to be better utilized.

[0054] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A method for improving the wear and corrosion resistance of an impact impeller, characterized in that: Includes the following steps: S1: Milling is performed on the easily worn areas of the impact wheel to form a filling area; S2: High-strength, wear-resistant, and corrosion-resistant martensitic stainless steel is used as the filler material to fill the filling area, and laser cladding is performed; S3: Machin the laser cladding position to match the profile of the impact wheel; S4: Aging treatment is performed on the machined impeller at a temperature below the initial temperature of austenite transformation (Ac1); S5: Polish the surface of the impact wheel after aging treatment until smooth.

2. The method according to claim 1, characterized in that: In step S1, it is necessary to determine the easily worn areas on the impact wheel.

3. The method according to claim 2, characterized in that: When determining the easily worn areas, the easily worn areas on the model of the impact wheel are theoretically calculated based on the model, and the easily worn areas are marked on the actual impact wheel according to the location of the easily worn areas on the model.

4. The method according to claim 3, characterized in that: There are 4 easily worn areas.

5. The method according to claim 1, characterized in that: In step S2, the composition of the high-strength, wear-resistant, and corrosion-resistant martensitic stainless steel includes the following elements by mass percentage: C (0-0.03%); Cr (11.5%-14.0%); Ni (7.5%-9.5%); Cu (1.0%-2.5%); Nb (0.3%-0.6%); Ti (0.5%-1.4%); Mo (0.1%-0.3%); Mn (0.1%-0.3%); Si (0.1%-0.3%); Al (0.1%-0.3%); P (0-0.04%); S (0-0.03%); O (0-0.04%); N (0-0.04%); the remainder being Fe and unavoidable impurity elements.

6. The method according to claim 1, characterized in that: In step S2, the power of laser cladding is 15000W.

7. The method according to claim 1, characterized in that: In step S2, the laser cladding rate is 600 mm / min.

8. The method according to claim 1, characterized in that: In step S2, the overlap rate of laser cladding is 50%.

9. The method according to claim 1, characterized in that: In step S4, the aging treatment temperature is 460℃~520℃, the aging time is 3h~4h, and the cooling method is air cooling.

10. The method according to claim 1, characterized in that: In step S5, during grinding, the surface of the impact wheel is considered smooth once it reaches the designed roughness.

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