Molten Salt Vapour Corrosion of Ti_3Al and TiAl Based Intermetallics

摘要

Hot corrosion tests were performed with Ti_3Al, Ti-44Al, Ti-48Al, Ti-52A1, Ti-48Al-2Cr and Ti_3Al-11Nb (at%) intennetallics. The salt mixture used in the present study consisted of 80wt%Na_2SO_4 + 20wt%NaCl, with a melting point of ～ 700℃. The specimens were suspended in the salt vapour at 800℃. It was found that the hot corrosion resistance generally increases with increasing Al content. Ti-48Al-2Cr showed the best corrosion resistance due to its relatively high Al content and Cr addition. Ti_2Al-11Nb unexpectedly showed poor corrosion resistance. It is suggested that the Nb addition might accelerate the formation of sulphide at the interface, playing a detrimental role in the corrosion process. Electron microscopy and X-ray diffraction were used to study the morphologies, compositions, and phases of the corrosion products. The mechanisms of hot corrosion were also discussed based on the experimental results.