The Surface Analysis Of Oxide Scale On Two Kinds Of New Ti-based Alloys

Ti-4Al-2V and Ti-2Al-2.5Zr alloys are two new type of alpha Ti-alloys developed in recent years in our country, for their low strength, high fictile, corrosion resistance, good weldability and fine performance in high and low temperature, they are mainly used as heat-conducting tubes in vapour generators and other components in aerospace and nuclear reactors, etc. Working safely for prolonged periods in high-temperature and high-pressure environments, the detailed and systematic study on the behavior of this two kind Ti-alloys in this special environment are very important from both theoretical and applied view points.We have perform surface analysis to Ti-4Al-2V and Ti-2Al-2.5Zr alloys with X-ray diffraction (XRD), Auger electron spectroscopy (AES) and Raman spectrum (Raman), the Ti-alloys oxided in high-temperature and high-pressure water with pH=7.0±0.5 and pH=9.0±0.5, and the oxide time is 500h, 1000h and 13000h, respectively. The results show that: oxide scales are found on the surface of this two Ti-alloys; the oxide scales are mainly composed of boorkite-TiO₂, anatase-TiO₂, Ti₃O₅ and Al₂TiO₅, and no rutile-TiO₂ is found; the segregation of Al to the surface is found in the oxide scales; the oxide scales increased with oxidation time; brookite-TiO₂ and anatase-TiO₂ have a trend of disappear when Ti-alloys oxided in water of pH=9.0±0.5, and the oxide scales are thinner than that of in pH=7.0±0.5; the location of the strongest peaks in XRD spectrum are not superposition if oxided in water of different pH value.