腐蚀和空化腐蚀性能是评估流体机械元件性能和可靠性的重要指标，而激光熔化沉积(LMD)作为材料表面改性和复杂构件制造的重要技术手段，是提升材料力学性能的有效途径。本工作利用激光熔化沉积制备了316L不锈钢样件，系统研究了激光功率、扫描策略、重熔及打印方向对成形件电化学腐蚀及空化腐蚀性能的影响，并与锻造316L不锈钢的腐蚀与空化腐蚀特性进行了比较。用开路电位测量法和动电位极化法测试了各沉积态试样在3.5%NaCl溶液中的耐腐蚀性能，并分析了不同工艺参数下LMD-316L不锈钢样品的空化腐蚀性能。与锻造316L不锈钢的均匀等轴晶显微结构相比，LMD-316L不锈钢具有与工艺参数相关的非平衡微观结构，即：大/小角度晶界、晶粒、胞/枝晶亚结构、与工艺相关的缺陷等，LMD-316L不锈钢的晶粒尺寸远大于锻造316L不锈钢，提高激光功率、打印方向从水平方向变为垂直打印时，材料的晶粒尺寸和枝晶臂间距均呈增大趋势，然而，表面重熔和90°旋转扫描策略处理后，材料的晶粒尺寸和枝晶臂间距变化趋势明显不同，显微硬度测试结果表明，相比晶粒尺寸，枝晶臂间距能够更好地解释显微硬度的变化规律。这种显著的微观结构差异也导致了LMD-316L不锈钢的电化学及空化腐蚀性能明显不同于锻造316L不锈钢。电化学腐蚀测试结果表明LMD-316L不锈钢的耐腐蚀性能远优于锻造316L不锈钢，不同工艺参数下LMD-316L不锈钢样件的极化电阻(R_p)相比锻造316L不锈钢提高了2~98倍，而腐蚀电流密度(i_corr)降低了1~2个数量级；超声振动空化系统测试结果表明LMD-316L不锈钢的抗空蚀能力优于锻造316L不锈钢，但LMD-316L不锈钢内孔洞、晶界等作为应力集中源会优先发生空化损伤，并在随后的空化腐蚀进程中呈现“突出状”并逐渐消失形成大量韧窝。材料的抗空化腐蚀能力主要取决于其局部力学性能，LMD-316L不锈钢的硬度显著高于锻造316L不锈钢，因此其抗空蚀能力显著提高，然而由于LMD-316L不锈钢内部存在不均匀的微观组织和与工艺相关的孔洞缺陷，导致LMD-316L不锈钢的显微硬度云图呈现空间不均匀分布的特点，因而LMD-316L不锈钢空化后的表面形貌在某些局部区域存在较为严重的空化损伤。

Corrosion and cavitation erosion are important indicators for evaluating the performance and reliability of hydraulic machinery. Laser metal deposition (LMD), as an important technique for both surface modification and complex component fabrication, is proven to be effective in enhancing the mechanical properties of materials. In this study, 316L stainless steel (316L SS) samples were fabricated using LMD and the effects of laser power, scanning strategy, surface remelting, and build direction on the electrochemical corrosion and cavitation erosion resistance of the LMD-produced samples were systematically studied. The obtained results were compared with those of a wrought counterpart. The corrosion resistance of the LMD-produced samples in a 3.5%NaCl solution was tested via open-circuit potential measurement and potentiodynamic polarization tests. Also, the cavitation erosion resistance of the LMD-produced samples was studied according to different process parameters. The microstructure of the forged 316L SS sample was characterized with uniformly distributed equiaxed grains, whereas the LMD-produced samples exhibited a process-dependent nonequilibrium microstructure consisting of high-/low-angle grain boundaries, tortuous grains, cellular/dendritic substructures, and processing-related defects. The grain size of the LMD-produced 316L SS sample was much larger than that of the forged 316L SS. By increasing the laser power or changing the sample from horizontally built to vertically built, both the grain size and dendritic arm spacing of the material tended to increase. However, when surface remelting and the 90°-rotation scanning strategy were adopted, the changes in the grain size and dendritic arm spacing of the material were obviously different. Results of a microhardness test showed that the dendritic arm spacing can better match the microhardness evolution than the grain size. This microstructural difference also led to a significantly different electrochemical corrosion and cavitation erosion performance from that of the forged 316L SS. Results of an electrochemical corrosion test showed that the corrosion resistance of the LMD-produced 316L SS sample was much better than that of the forged 316L SS, i.e., the polarization resistance (R_p) of the LMD-produced 316L SS sample under different processing increased by about 2-98 times, while the corrosion current density (i_corr) decreased by one to two orders of magnitude. The test results of an ultrasonic vibration cavitation system showed that the cavitation erosion resistance of the LMD-produced 316L SS sample was better than that of the forged 316L SS. However, stress concentration may be induced in local areas such as pores and grain boundaries, which, in turn, facilitate preferentially cavitation damage in these areas. Also, protrusion topography appeared, and gradually disappeared to form a large number of dimples in the subsequent cavitation erosion process. The cavitation erosion resistance of the material mainly depended on its local mechanical properties. The microhardness test results showed that the hardness of the LMD-produced 316L SS sample was significantly higher than that of the forged sample, so its cavitation erosion resistance was significantly improved. However, because of the heterogeneous microstructure and process-related pore defects formed in the LMD-produced samples, the microhardness contour exhibited a spatially nonuniform distribution characteristic; hence, the surface morphology of the LMD-produced 316L SS sample was seriously eroded in some local areas after cavitation.