Abstract
The paper presents the results of studies of modification of the surface structure of structural steels AISI 321 (12Х18Н10Т) and AISI 201 (12Х15Г9НД) after plasma treatment with several pulses. The topology of the surface and the evolution of the relief are studied depending on the main processing parameters. In particular, the sequence of phase transitions in modified layers depending on the processing multiplicity was studied. It is shown that under a small number of treatments (n = 2) in investigated stainless steel samples may occur plasma etching and redistribution of crystallites. In addition, in samples detected traces of blister formation and the presence of a layered structure, which can be due to planar and linear defects. When increasing the multiplicity of treatments to 10, the structure becomes more ordered, the columnar blocks are located relatively evenly over the surface and their tracks are located mainly along the grain boundaries. The changes in the structure of the studied structural steels are associated with the formation of new phases (iron nitride) and microarrays in the crystal lattice. A decrease in crystallites size to 16 nm was detected. It is shown that the multiple pulse plasma processing is most effective for grinding austenite crystallites, especially the iron nitride in stainless steel.