Study of H2/N2Mixture Plasma Treatment on the AISI 1045

In the present work, we analyzed the effect of the plasma treatment of 80% H2 /20% N2 mixture plasma over the AISI 1045 steel. To produce the plasma, an AC discharge of 0.1 A at 350 V was produced at a total pressure of 3.0 Torr. The mixture plasma was analyzed using optical emission spectroscopy (OES), in the wavelength range of 200 to 1100 nm. The principal species observed in the plasma were NH, N2 , N2 +, H2 , and Hα. The electron temperature and ion density have been measured using a double Langmuir probe. The samples of steel were treated by plasma at different discharge times, between 3 and 12 h, at the same pressure and AC parameters (0.1 A and 350 V). The treated samples were characterized using X-ray analysis, finding the phases gamma and epsilon of iron nitride. The thickness of the nitrided layers was measured using a scanning electron microscope (SEM). From the images obtained, it is possible to appreciate the interphase between the nitrided layer and the steel matrix. The relationship between the morphology of the surface of nitrided steel and the wetting was analyzed by measuring the contact angle between the surface and a drop of 5 µL of distilled water. The contact angle of the drop increased with the increase of plasma treatment time. The control sample without treatment presented a smaller angle, and after the treatment the surfaces of the steel became hydrophobic. This may be related to the morphology change of the steel surface produced by plasma treatment.