Fig. 10

Gas nitriding of S21 sample, at 900 °C for 15 min in electric furnace. (a) sample S21 after nitriding, (b) OM of cross-section microstructure on top part of the sample, (c) SEM image on the top part of S21 cross-section, (d,e) line scan SEM–EDS analysis on the top of S21 cross-section.