Effects of pre-oxidation on the corrosion behavior of pure Ti under coexistence of solid NaCl deposit and humid oxygen at 600 °C: the diffusion of chlorine

The effect of pre-oxidation on the corrosion behavior of pure Ti covered with a solid NaCl deposit in the humid O2 flow at 600 °C is studied. The oxide scale, formed by pre-oxidation, protects the substrate from the NaCl induced corrosion during the initial stage. However, the corrosion of the pre-oxidized sample is severely accelerated by solid NaCl after an incubation period. The chlorine, generated from the decomposition of solid NaCl, diffuses into the oxide/substrate interface as ions during the incubation period, which was observed by ToF–SIMS. The chlorine at the oxide/substrate interface induces the fast corrosion after the incubation period although the pre-oxidation scale is complete and compact.

Simulation on the Thermal Stress of Super304H Oxidation Scale at 600°C

In this paper, based on the analysis of cross-section of steam oxidation of Super304H sample at 600°C, thermal stress contours were obtained by using finite element analysis through establishing geometric model and refine meshing. After extracting the stress in the interface of oxide layer and analyzing the thermal stress, it can be found that there exists compressive and tensile stress in the interface between substrate and scale, which is affected by the slope of the interface.

Oxidation Behavior of As-Forged Fe-25wt%Cr Alloys at 1100°C in Air

Fe-25wt%Cr alloys were fabricated by combining Powder Metallurgy (PM) with hot-forging treatment, and their oxidation behavior at 1100°C in air was investigated systematically by using XRD, SEM and EDS, respectively. The results showed that a composite oxidation scale containing both Cr2O3and FeCr2O4formed on the surface of as-forged Fe-25wt%Cr alloys after oxidation at 1100°C in air for 100 hours. The oxidation process of Fe-Cr alloys could be obviously divided into two different stages, and the kinetics of two-stage oxidation agreed well with the parabolic law. The first could be corresponding to the formation of protective Cr2O3layer, while the second could be thought as the growth of FeCr2O4and the further oxidation of the inner Cr2O3oxidation scale. The faster oxidation rate in the second stage could be attributed to both the diffusion of iron ions rapider than that of Cr in the Cr2O3layer and the fast transport velocity of oxygen ions along the cracks.

Effect of TiC Content on Oxidation Behavior of Sintered WC-TiC-TaC Alloys

The effect of TiC content on oxidation behavior of the sintered WC-TiC-TaC alloys with 2 mass% TaC and different TiC amount of 3-45 mass% was investigated through oxidation tests in air at 973K in order to clarify their oxidation mechanism at high temperature. Based on the results of mass change, SEM observation, elemental map analysis and composition analysis of the samples before and after the oxidation test, it was revealed that with increasing TiC content in the alloys, mass changes from oxidation and thickness of the oxidation scale decreased. Thus, it is considered that the main component of the scales changed from WO3 to TiO2 gradually with increasing TiC content in the alloys, and oxygen diffusing through the oxidation scale to the alloys was inhibited more and more.