Nanocrystalline ceramic coating on γ-TiAl by bipolar plasma electrolysis (effect of frequency, time and cathodic/anodic duty cycle)

The present work reports the usage of plasma electrolysis for nanocrystalline coating of γ-TiAl alloy by applying pulsed current in an organic electrolyte based on glycerol. Response Surface Methodology (RSM) was applied to optimize the operating conditions for small nanocrystallite sizes of coatings. The levels studied were the ratio of duty cycle of cathodic direction to duty cycle of anodic direction of 0.2–0.4, frequency of pulsed current range between 5 and 15 kHz, and treatment time of 10–30 min. The usage of high applied frequencies and low ratios of duty cycle of cathodic direction to duty cycle of anodic direction and also treatment time is more suitable for achieving lower sizes of complex nanocrystallites. The samples with high height to width ratio of distribution curves of nanocrystallites have simultaneously smaller average sizes of nanocrystallites and lower length to diameter ratio of nanocrystallites.