Material corrosion characteristics of heat-treated SLM-ed Hastelloy X in electrochemical machining process

Abstract

Selective laser melting (SLM) technology and electrochemical machining (ECM) offer new methods for producing nickel-based superalloys with complex structures and high surface quality, including Hastelloy X parts. However, SLM-fabricated parts exhibit significant anisotropy, and there are no effective criteria for evaluating material corrosion characteristics in actual ECM due to the detachment of research and application, making the parameter selection challenging in actual ECM. To address this issue, this article proposes a comprehensive evaluation system based on the corrosion characteristics in the actual machining process and investigates the effect of heat treatment temperature on the corrosion characteristics of Hastelloy X in ECM. The results show that at a heat treatment temperature of 1000°C, machining efficiency, accuracy, and localization can all be achieved at a good level with good consistency in different directions at the expense of a certain machining accuracy. The 800℃ heat-treated specimen exhibits strong corrosion resistance, providing a significant advantage in machining localization and accuracy. When the heat treatment temperature exceeds the solid solution temperature (more than 1175℃), the mechanical properties and corrosion characteristics of the specimen are significantly degraded. The results of various material testing methods, including electrochemical testing, EBSD, XRD, and EDS indicate that changes in grain size due to recrystallization and the galvanic effect of precipitates are the primary causes of these changes.