Preparation of TiN and TiO2 Coatings on Stainless Steel Surface by Chemical Vapor Deposition and Their Anti-coking Property

In order to avoid the catalytic cokes forming, the TiN and TiO2 coatings were deposited on the surface of the 3105 stainless steel flake with the diameter of 10x10x0.9 mm by atmospheric pressure chemical vapor deposition. The deposition temperature was 850 degrees C for TiN and TiO2, and the deposition time was 2.5 h. The morphologies and structures of the coatings were analyzed by SEM, EDS and XRD. An atmospheric pressure cracking system was set up for evaluating the anti-coking property of TiN and TiO2 coating with n-hexane, cyclohexane, benzene and RP-3 as feedstock. The results show that the TiN and TiO2 coatings are continuous, close-packed and homogeneous; the titanium nitride in the coating has cub phase, Ti and N atomic ratio in the titanium nitride coating is 1:1, and the titanium oxide in the coating is the Ti2O3 Ti3O5 stoichiometrically. TiN and TiO2 coatings exhibit an excellent anti-coking performance. The anti-coking ratio of TiN coating for n-hexane, cyclohexane, benzene and RP-3 is 99.91%, 86.19%, 72.36% and 94.68%, respectively; correspondingly, the anti-coking ratio of TiO2 coating is 83.39%, 85.77%, 57.78% and 68.57%, respectively. Hence, the TiN coating has a better anti-coking performance than TiO2 coating. The morphologies of the cokes on 3105 surface are mainly filamentous cokes, and TiN and TiO2 coatings inhibit the filamentous cokes formation.