Laser Shock Processing of 9Cr18 Steel and Synergistic Preparation of Surface Micro-pits

The work aims to explore the feasibility and related processes of preparing surface micro-pits by secondary laser impact after laser shock processing of 9Cr18 steel. The single-point impact of 9Cr18 steel samples with different process parameters was carried out, the Laser Confocal was used to measure the two-dimensional morphology profile of micro-pits texture by single-point laser shock induction and the hardness of micro-pit induced by single-point impact was measured by microhardness tester. The full coverage surface of 9Cr18 steel was impacted by laser shock processing to obtain the surface strengthening layer, and the micro-pit texture was treated by secondary laser impact induction to form the surface texture. For the micro-pit prepared by single-point impact, the depth of the surface micro-pits increased with the increase of laser impact energy, but it was not linear. When the impact energy was 12 J, the depth of the micro-pits reached 38.39 µm. When the single-point double impact was carried out under the same energy, the depth of the surface micro-pits slightly increased compared with the single-point single impact under the same energy. When the impact energy was 12 J, the maximum depth of the micro-pits obtained by the double impact was 49.05 µm. When the superimposed impact of different energy gradients was carried out and 6 J was used as the first impact energy and the second impact energy gradually increased to 12 J, the surface micro-pit depth after the superimposed gradient energy reached 58.61 µm. For the impact of different energy and different pulse width, when the pulse width was 26 ns, the micro-pit depth under the impact of different energy reached the deepest and gradually increased to a stable depth with the increase of pulse width. After laser shock processing, different energies were used for secondary impact, and the depth of the micro-pits reached 19.79 µm when the secondary impact energy was 12 J. After laser shock processing, the depth of the micro-pits reached 13.61 µm when the secondary impact pulse width was 22 ns and 26 ns. It can be concluded that the depth of surface micro-pits increases to varying degrees with the increase of energy, pulse width, and impact times, and then reaches a stable state at a certain parameter. The hardness of surface micro-pit under single impact with different parameters increases significantly with the increase of energy and impact times, and decreases firstly and then increases with the increase of pulse width. The preparation of micro-pits on the strengthening layer is realized, the surface is strengthened by laser impact to improve the surface hardness to obtain a good surface strengthening layer, and the secondary single-point impact on the surface is used to prepare micro-pits, which can achieve the ideal hardness and micro-pit depth. Through step-by-step experimental research, the reasonable synergistic treatment of the laser shock processing can achieve the strengthening of 9Cr18 steel surface and the preparation of a certain depth of micro-pits, providing theoretical guidance and process basis for the strengthening and textured surface of 9Cr18 steel by laser impact. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.