M50 steel was implanted with nitrogen at elevated temperatures ranging from 260 • C to 420 • C using plasma-based ion implantation. The effect of implantation temperature on surface microstructure, hardness, and wear resistance was investigated. It is observed that nitrogen penetrates very deeply from the surface as a result of implantation and thermal diffusion at elevated temperatures. The amount of nitrides and their distribution depth as well as the hardness and the wear resistance in the surface layer increase with the processing temperature. As the implantation temperature increases, the wear mechanism changes from adhesive wear to abrasive wear.Index Terms-Elevated temperature ion implantation, plasmabased ion implantation (PBII), structure, wear.