Inconel 718镍基超合金的空蚀行为研究

Investigation of the Cavitation Erosion Behavior of Inconel 718 Nickel-based Superalloy

采用超声振动空蚀试验机对Inconel 718镍基超合金与316L不锈钢进行空蚀磨损研究.通过扫描电子显微镜(SEM)、场发射电镜(FESEM)以及高分辨X射线衍射仪对测试样品空蚀磨损表面形貌、微观结构演变和物相进行观察及分析.结果表明:Inconel 718表现出更优异的抗空蚀磨损性能,其空蚀600 min累计质量损失约为316L的1/3,空蚀孕育期时长为316L不锈钢的2倍左右.在空蚀孕育期,Inconel 718空蚀损伤首先发生在晶界、孪晶界等界面处,且并未出现明显的塑性变形.316L在此期间呈现较为明显的塑性变形,空蚀表面起伏波动显著.在空蚀加速期,Inconel 718质量损失的显著提升是由于空蚀表面微裂纹的扩展导致材料逐渐剥落引起的,316L则是由于空蚀表面大量凹坑的不断形成与合并导致质量损失的增加.Inconel 718空蚀120 min后,观察到空蚀磨损表面有明显的形变孪晶,且与空蚀前的金相形貌相比,形变孪晶有明显增多的趋势.

The cavitation erosion behavior of Inconel 718 nickel-based superalloy and 316 L stainless steel were investigated using an ultrasonic vibration apparatus.The eroded surface,microstructure evolution and phase analysis were also observed and explored through scanning electron microscopy,cold field emission scanning microscopy and high-resolution X-ray diffractometer.The results show that Inconel 718 had excellent cavitation erosion resistance,its cumulative mass loss in 600 min and incubation time was about 1/3 and 2 times than that of 316 L,respectively.At incubation period,the eroded region of Inconel 718 mainly located on the grain boundary,twin boundary and other interfaces.In contrast,316 L behaved marked plastic deformation which was characterized by the surface fluctuation.During the acceleration period,it was noted that the notable increase of mass loss about Inconel 718 was caused by the gradual spalling of material with propagation of microcracks on cavitation surfaces.At the same time,the remarkable mass loss of 316 L was contributed to the continuous formation and merger of numerous pits on cavitation surfaces.After cavitation erosion for 120 min of Inconel 718,obvious deformation twins were observed on the eroded surface.Compared with the metallographic morphology before cavitation,the number of the deformation twins significantly increased.