Nitrogen ion implantation on the mechanical properties of AISI 420 martensitic stainless steel

Nitrogen ions with different energy of 30 keV and 50 keV and dose of 5 × 10¹⁶, 5 × 10¹⁷ and 1 × 10¹⁸ cm^− 2 were implanted into the surface of AISI 420 martensitic stainless steel. The micro topography, roughness, friction coefficient, wear loss, hardness, as well as the chemical composition were investigated. Mounds and craters were found on the ion implanted surfaces, indicating increases in the roughness. However, very little changes in friction coefficient were detected after implantation. Nitrogen ions implantation on AISI 420 significantly improved the nanohardness, and the value of 16.2 GPa at the depth of 17.3 nm was about 2.3 times as hard as the untreated samples at the same depth when the implant energy and dose were 50 keV and 5 × 10¹⁶ cm^− 2, respectively. The wear loss of the implanted samples was less than that of untreated ones, and an optional dose of 5 × 10¹⁷ cm^− 2 could be used for the wear resistance improvement. XPS results demonstrated that chromium nitrides were produced during ion implantation, which possibly contributes to the improvements of the hardness and wear resistance. The N 1s core spectra showed that nitrogen oxides was found in the samples with higher implantation dose, which had counteraction for the improvements of the hardness.