Abstract:
VAT46® alloy has great application potential in engine valves, where it is mandatory that the alloy has good mechanical property and high temperature corrosion resistance. In other alloys commonly used in valves, two factors influence both the process and the type of oxidation: the phase δ and water in value state. In VAT46®, being an alloy in development stage, there is still not enough data about the influence of the water vapour presence during the oxidation process and if the phase δ influences the type of oxidation and the oxides nucleation. Therefore, two specimens were oxidized, one with phase δ and the other without, in different environment: one dry and the other one with water vapor, for 10 hours, a period sufficient to analyze the influence of phase δ and water vapor in the oxidation initial stage. For the experimental purposes, the furnace utilized made it possible to control the pressure and the environment chemical composition, and for the analysis of the results, an electronic scanning microscope and X-ray dispersion spectroscopy were also used. The data indicate a variation in the oxidation rate with the water vapor presence and the preference for oxide nucleation in distinct regions from those rich in phase δ.