Surface modification for steel rods based on atmospheric-pressure nitrogen plasma treatment at room temperature

A surface modification process for steel rods based on atmospheric-pressure nitrogen plasma (APP) at room temperature was developed. Steel rods were irradiated with APP generated by dielectric-barrier discharge in a nitrogen atmosphere. Elemental analysis using an electron-probe microanalyzer revealed strong nitrogen signals at the top surface, which suggests the formation of a modified layer due to the generation of excited nitrogen sources by APP. However, no noticeable nitrogen diffusion into the steel was observed. This is because the excited nitrogen sources reacted with elemental iron emitted by APP and nitrides were deposited on the surface of the steel. The proposed APP treatment is a promising approach for modifying the surface of steel rods without heat treatment.