Improvement in the graphite electrode wear characteristic of electrical discharge machined Nimonic 90 through plasma nitriding, laser hardening and duplex process.

An untreated graphite electrode has been observed to have limited applications based on the wear behavior and mechanical properties in the Electrical Discharge Machining (EDM) of superalloys. Hence, to reduce the wear of graphite electrodes below this level, a Plasma Nitriding (PN), Laser Hardening (LH) and a duplex process (PN + LH) on graphite electrodes are proposed to reduce the frontal and lateral wear. In this work, the influences of pulse duration, current and Silicon Nitride (SiN) added EDM oil on frontal and lateral wear of untreated and treated graphite electrodes are investigated. The hardness in untreated graphite and treated graphite electrode surfaces are also studied. The result confirmed that the duplex process produced graphite has 54% higher hardness as compared to the untreated/raw graphite. The 49% frontal and 42% lateral wear are reduced using a duplex process with 900 µs pulse duration. [ABSTRACT FROM AUTHOR]