The effects of applied voltage on surface texturing during cathodic plasma electrolysis process

Cathodic plasma electrolysis (CPE) process was applied on cast iron samples for about 1 minute to obtain a crater-liked surface texture with intention to reduce the friction and increase the wear resistance. During the treating process, the plasma discharging was initiated at the surface of cast iron samples, leading to the explosion of gas bubbles and then generating an irregular array of micro craters. The scanning electron microscopy (SEM) observations showed that the recessed and protruded surface textures were obtained when the CPE-process was conducted at low and high voltages, respectively. The textured surfaces were measured and characterized using skewness and kurtosis Pin-on-disc tribotests on those textured samples demonstrated that the samples with negative skewness and higher kurtosis had a smaller coefficient of friction (∼0.08), while the samples with positive skewness and higher kurtosis had a larger coefficient of friction (∼0.104), which was even higher than that of untreated blank sample (∼0.1). The results indicate that the applied voltage significantly influences the surface finish in terms of surface texture and morphology, and thus the coefficients of friction.