Elevating fatigue life in nickel-based superalloys through suppression of persistent slip bands/markings via high-density pulsed electric current treatment

Abstract

This study investigates the inhibitory effects of high-density pulsed electric current (HDPEC) treatment on fatigue crack initiation in directionally solidified nickel-based superalloy. Experiments were conducted under fully reversed conditions (R = -1) using low-cycle fatigue tests to assess the impact of HDPEC on crack initiation. The distribution of misorientation at different stages before and after crack initiation of untreated and HDPEC-treated samples was analyzed through kernel average misorientation maps by electron backscatter diffraction method. The results demonstrate that the HDPEC treatment significantly delays the initiation life of cracks, extending from approximately 2000 cycles to 5000 cycles. Additionally, the average fatigue life of the samples increased from 3851 cycles to 10881 cycles, more than doubling the fatigue life. Furthermore, the formation of persistent slip markings on the surface of the HDPEC-treated samples was completely suppressed, indicating changes in the persistent slip band’s structure. This phenomenon led to a distinct pattern of crack formation and propagation compared to untreated samples, suggesting that HDPEC treatment effectively alters the pattern of crack initiation and propagation by homogenizing dislocation distribution and alleviating residual stresses caused by cyclic loading. The result confirms the potential of HDPEC technology to enhance the fatigue life of nickel-based superalloys, and underscores the potential for further research in this domain.

Keywords

• ni-based superalloy
• high-density pulsed electric current
• persistent slip band
• dislocation motion
• electron wind force