Effects of the high temperature plasma immersion ion implantation (PIII) of nitrogen in AISI H13 steel

In this paper we report the effect of high temperature PIII of nitrogen on the chemical and physical properties of AISI H13 steel. The implantation of H13 steels was carried out at different temperatures ranging between 300 °C and 720 °C. After the treatment, the surface morphology was drastically changed as observed by SEM analysis. Nitrogen penetration depth reaching up to 12 μm was achieved at 620 °C and 720 °C. The maximum hardness of about 592 HV was obtained for the sample treated at 470 °C that is 17% higher than for untreated specimen. There was a decrease of the hardness values for temperatures above 470 °C. The same hardness behavior with the temperature was confirmed by nanoindentation testing. Although an enriched nitrogen layer was obtained, no evidence of nitride compounds was detected by XRD analyses. On the other hand, improvements of the H13 steel tribological properties and corrosion resistance were obtained. The wear tests were conducted by pin-on-disk tribometer (rotating mode). The wear volume decreased by factor of 4.5 compared to the standard tempered and annealed H13 steel and 2.6 times reduction of the coefficient of friction was achieved. The electrochemical measurements were performed in 3.5% NaCl solution, pH = 6. Open circuit potential curves showed that the potentials are nobler for the PIII treated samples than for untreated specimen. In addition, the corrosion current density of the samples treated at 620 °C and 720 °C diminished to 3 × 10⁻⁸ A/cm².