Super duplex stainless steels (SDSS) have high corrosion resistance because of their high contents of chromium, nickel, molybdenum and nitrogen but low wear resistance. To improve the wear resistance of these steels without affecting their corrosion resistance, samples of SDSS were treated by plasma ion nitriding at temperatures ranging from 350 °C to 570 °C for two hours. This thermochemical treatment resulted in the formation of different types of nitrides that affected the microhardness, the microwear behaviour and the corrosion resistance of the metal surface. The microwear resistance decreased at 400 °C because different nitrides formed on the surface, thereby increasing the hardness and volume wear resistance of the steel. The test results showed that the alloys that were nitrided at 400 °C and 450 °C exhibited the highest corrosion resistance to a solution medium containing chloride ions.

The great interest in the study of diamond-like carbon films (a-C:H) is justified by its mechanical and tribological properties. However, the high internal stress of the film results in its difficult adhesion to the metallic substrate, which can be solved by nitrogen incorporation in the a-C:H film, allowing a formed film of lower internal stress. The objective of this work is to evaluate the influence of flow (20, 30 and 40sccm), CH₄/Ar ratio (90/10 and 70/30) and voltage (400, 500, 600 and 700 V) in the a-C:H formation. For the best condition of the film, we studied the effect of nitrogen incorporation in the hardness and wear resistance of the a-C:H(N), modifying the nitrogen percentage in the treatment at 10% to 60% N₂. The treatments were carried out in the Ti₆Al₄V substrate by DC-PECVD for two hours. For good adhesion of the films on the substrate, a silicon interlayer must be produced. The increase in the voltage above 600 V increases the I_D/I_G and film thickness, causing its delamination, and the gas ratio did not influence the a-C:H characteristics. The a-C:H film deposited with 30 sccm, 90/10 and 500 V was characterized as a-C:H (hard), with properties such as the hardness of 17 GPa, 30% H, 39% sp³ and I_D/I_G ratio of 0.58. Since nitrogen reduced the deposition rate, the total gas flow for the production of a-C:H(N) was performed with 40 sccm. The Raman spectra of a-C:H(N) films showed changes in D band intensity and displacement in relation to the nitrogen-free film spectrum, evidencing the incorporation of nitrogen in the film. The XPS analysis showed the linear increase of the nitrogen incorporation in the a-C:H(N) film with the increase of the amount of the N₂ gas in the treatment, which caused, in general, a decrease in the amount of C–C sp³ bonding, increasing the adhesion of the film in the substrate and not necessarily the low wear resistance of the formed film.