| REN Qiannan,HU Hongxiang,ZHENG Yugui.Effect of Width-to-Depth Ratio and Duty Cycle of Surface Microstructure on Cavitation and Cavitation Erosion on Martensitic Stainless Steels[J],53(11):67-79 |
| Effect of Width-to-Depth Ratio and Duty Cycle of Surface Microstructure on Cavitation and Cavitation Erosion on Martensitic Stainless Steels |
| Received:February 02, 2024 Revised:April 18, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.11.006 |
| KeyWord:cavitation erosion surface microstructure numerical simulation volume fraction of vapor phase absolute pressure duty cycle width-to-depth ratio |
| Author | Institution |
| REN Qiannan |
Institute of Metal Research, Chinese Academy of Sciences, Shenyang , China;School of Materials Science and Engineering, University of Science and Technology of China, Shenyang , China |
| HU Hongxiang |
Institute of Metal Research, Chinese Academy of Sciences, Shenyang , China |
| ZHENG Yugui |
Institute of Metal Research, Chinese Academy of Sciences, Shenyang , China |
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| Abstract: |
| The work aims to investigate the effects of surface microstructure on cavitation erosion. In this paper, a series of dot array-shaped microstructures were successfully established by Gambit. Ansys Fluent was employed to simulate the cavitation of the flow domain around the surface microstructure with different geometry characteristics. Absolute pressure, volume fraction of vapor phase, and bubble movement velocity were utilized to characterize the cavitation and cavitation erosion. Finally, a cavitation erosion test was performed to confirm the simulation results with a magnetostrictive-vibration cavitation facility. The mass loss method was used to evaluate the cavitation erosion. The results showed that both the width-to-depth ratio and the duty cycle of the microstructure affected the cavitation process. For the width-to-depth ratio of the surface microstructure, when it was less than 2.5, the volume fraction of the vapor phase on the bottom surface of the microstructure was reduced to less than 0.1. A layer of "liquid buffer" was formed in the groove, which could alleviate cavitation erosion. For the duty cycle of the surface microstructure, the volume fraction of the vapor phase was the smallest when the duty cycle was 0.91, remaining below 0.4. The "liquid cushion" was also formed on the surface of the sample, which absorbed the impact energy of the bubbles on the surface of the material as they collapse. As the duty cycle increased, the absolute pressure on the microstructured surface increased, reducing the degree of cavitation and similarly acting to slow down cavitation erosion. The cavitation experiments were performed on microstructured samples at different duty cycles with smooth samples as a control group. It was found that the mass loss and the SEM morphology of cavitation erosion of samples with microstructures were lighter than those of smooth samples, implying that surface microstructures could effectively mitigate the cavitation erosion of materials. Combined with the analyses of the simulation results, it was concluded that the microstructure had different mechanisms to mitigate cavitation erosion under different duty cycles. At the duty cycle of 0.38, the microstructure pushed the bubbles away from the sample surface to mitigate cavitation erosion, and at duty cycles of 0.71 and 0.91, the microstructure mitigated cavitation erosion by reducing the vapor phase volume fraction. When the duty cycle was 0.91, the mass loss of the microstructured samples was 5.95 mg, much smaller than that of the microstructured samples at the duty cycles of 0.71 and 0.38. It was also demonstrated that the larger the duty cycle of the surface microstructure, the better the cavitation erosion resistance of the material. In conclusion, the width-to-depth ratio of the surface microstructure mainly affected the vapor phase volume fraction of the bottom surface of the microstructure, while the duty cycle affected the absolute pressure across the surface and the vapor phase volume fraction at the top surface of the microstructure. It was proved that the surface microstructure could improve the cavitation erosion resistance of martensitic stainless steel. When the microstructure width-to-depth ratio was small and the duty cycle was large, the vapor phase volume fraction was low, which could further mitigate cavitation erosion. In this paper, the effect of the width-to-depth ratio and duty cycle of the surface microstructure on the reduction of cavitation erosion is investigated in terms of numerical simulation as well as experimentally. Reasonable microstructure width-to-depth ratios and duty cycles are determined, and an intrinsic mechanism based on surface vapor phase volume fraction affecting cavitation erosion resistance is proposed. The vapor phase volume fraction is used as an indicator to provide a reference for subsequent quantitative control of the degree of cavitation erosion. |
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