Corrosion inhibition and surface hardening of KP1 and KP4 mold steels using pulsed electron beam treatment

We report the use of pulsed electron beam polishing (PEBP) as a surface treatment for KP1 and KP4 steels for applications in molds for injection molding. The corrosion of the re-solidified layer was analyzed using potentiodynamic polarization tests. The corrosion potentials became nobler by 50 and 30 mV vs. the saturated calomel electrode (SCE) for KP1 and KP4 steels, respectively, and the corrosion currents decreased by 50 μA for both materials. Variations in the contact angle and formation of oxides in the re-solidified layer indicated that the surface became more stable following PEBP. The corrosion mechanism was pitting of the re-solidified layer. The nano-hardness of KP1 increased by 316%, and that of KP4 increased by 144%, which is attributed to the increased density of dislocations in the re-solidified layer.