Characterization and wear behavior of pulsed electrode surfacing coatings

Pulsed electrode surfacing (PES), which is a micro-welding process, was adopted for depositing a sintered electrode of a mixture of TiC+2%B+2% Fe, on an AISI 8030 steel substrate. Different circuits were used and the deposition was carried out during 50 μs, with pulses having a current amplitude of 50 A and different frequencies of 50, 75 and 100 Hz. Sample characterization has been performed by using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Ball-on-disc tests were carried out to determine the friction and wear properties for every processing condition. The tests were conducted under non-lubricated conditions, in air with a relative humidity of 50±2% and ambient temperature of 24±1°C. Alumina balls of 6 mm diameter were loaded with a normal force of 5 N. The specimens were rotated there at a velocity of 0.1 m s−1 for a sliding distance of 1000 m. It was determined that the steady-state friction coefficients did not vary with the deposition parameters (μaverage=0.53) although the running in friction coefficient values were different, due to variation in the average roughness, Ra, of the treated samples. The wear resistance was evaluated by calculating the wear factor, k, considering that the wear volume is linearly proportional to the load and the sliding distance. Wear scar morphologies, on both coatings and alumina balls, were examined by using SEM and X-ray elemental mapping in order to establish the wear mechanism.