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A novel approach has been developed to fabricate a thin layer of titanium oxide (TiO2) on the surface of 316L stainless steel by a combination of Sol-Gel method and subsequent active screen plasma annealing (ASPA) method. Dip coated layers were plasma annealed in a titanium cylindrical mesh from 300 to 500 ℃. The effect of ASPA temperature on the particles size, morphology, and crystallinity of the coating layers was studied in comparison with conventional annealing. Also, electrochemical impedance spectroscopy and potentiodynamic polarization were employed to study the corrosion behavior of both types of coatings. The results showed that, a crack-free TiO2 coating with a thickness of about 1–5 μm can be obtained using the ASPA method at different calcination temperatures. Plasma annealing led to the decline of calcination temperature and formation of nanostructured anatase phase with higher crystallinity and structural uniformity in comparison to conventional annealing method. Moreover, the corrosion resistance of the coating was significantly increased compared to conventional annealing method. It was found that, the coating of titanium oxide can reduce by eight-fold the corrosion rate of 316L stainless steel.

The formation mechanism of Ti3SnC2 was evaluated in the present work. A stoichiometric ratio of a Ti-Sn-C powder mixture was prepared and milled for 50 h. To synthesize and detect intermediate reactions, a 50 h milled sample was thermally analyzed by STA. XRD instrument was utilized to detect phases of powder samples and the microstructure of the final product was obtained by SEM. The results showed that only Ti6Sn5 and Ti5Sn3 with Fe3Sn2 formed after 50 h milling, and no peaks related to MAX phases were found. To detect the reaction mechanism, the 50 h milled powder after STA analysis was characterized by XRD. Many intermediate reactions such as TixSny, TiC, and Ti2SnC formations took place. The melting of FexSny during STA analysis promoted the Ti3SnC2 formation. These results confirmed that Ti3SnC2 formation is not happened by a single reaction and many intermediate phases must be formed and Ti3SnC2 was synthesized after 50 h ball milling and thermally treated by STA analysis to 1400 °C.