NaCl溶液腐蚀后304不锈钢的超声空蚀特征

Ultrasonic cavitation erosion behavior of 304 stainless steel after corrosion in NaCl solution

对经NaCl溶液腐蚀后的304不锈钢进行符合ASTM G32标准的超声空蚀实验,从试样的质量损失、表面显微组织、表面形貌、表面粗糙度、显微硬度和残余应力等方面探究靶距和空蚀时间对空蚀的影响。研究结果表明:与未腐蚀试样相比,经NaCl溶液腐蚀后的304不锈钢的抗空蚀能力增强。在空蚀后期,疲劳损伤为空蚀破坏的主要原因,随着空蚀时间的延长,试样表面的裂纹增多,空蚀坑变深,但局部靶距的增加使表面整体的粗糙度在空蚀240 min后变化不明显。靶距对空蚀的影响明显大于空蚀时间的影响。当空蚀时间一定,靶距为0.4 mm时,试样的累积质量损失和表面粗糙度均达到最大,在该靶距条件下,加工硬化层厚度为250μm,硬度最大值出现在距离空蚀表面50μm处,而当靶距为0.6 mm时,残余应力达到最大。

An ultrasonic cavitation erosion experiment,which conforms to the ASTM G32 standard,was carried out on 304 stainless steel after corrosion in the NaCl solution.The effects of standoff distance and cavitation erosion time were described through mass loss,surface microstructure,surface morphology,surface roughness,microhardness and residual stress.The results show that the capability of resisting cavitation erosion of 304 stainless steel corroded in the NaCl solution is enhanced compared to that of non-corroded samples.In the later stage of cavitation erosion,fatigue damage is the main cause of cavitation damage.With the extension of cavitation erosion time,microcracks in the eroded surface increase and the depth of cavitation erosion pits increases as well,but the surface roughness varies insignificantly after cavitation erosion of 240 min due to the increase of local standoff distance.The effect of standoff distance on cavitation erosion is more remarkable than that of the cavitation erosion time.At certain cavitation erosion time,both the cumulative mass loss and the cumulative mass loss rate arrive at their maxima at a standoff distance of 0.4 mm.At this standoff distance,the thickness of the hardened layer reaches 250μm,the maximum hardness arises at the depth of 50μm,but the highest residual stress occurs at a standoff distance of 0.6 mm.