Roughness studies of NiTi shape memory alloy treated by nitrogen plasma based ion implantation at high temperatures

► NiTi SMA was nitrided by nitrogen PBII at 550 and 770 °C for 120 or 360 min. ► In addition to the austenic and martensitic NiTi phases, TiN and Ni3Ti was detected after treatment. ► Roughness was increased up to 50 nm at 550 °C and 80 nm at 770 °C. ► Nitrogen is incorporated only in the implanted depth (150 nm) at 550 °C, but extends to 1 μm at 770 °C. ► Below the nitrided layer without nickel, the bulk material is depleted in titanium.