预氧化提高Ti-48Al-2Nb-2Cr合金的抗热腐蚀性能

Improving of Hot Corrosion Resistance of Ti-48Al-2Nb-2Cr Alloy Via Pre-Oxidation

摘要:

TiAl合金具有优异的高温性能，但在高温下的抗氧化性和耐腐蚀性较差，从而阻碍了其在工程中的实际应用。以Ti-48Al-2Nb-2Cr合金为研究对象，为其免受热腐蚀侵蚀，通过预氧化在其表面制备一层致密的保护膜，研究预氧化处理对Ti-48Al-2Nb-2Cr合金在Na₂SO₄（质量分数75%）+NaCl（质量分数25%）混合盐环境中的热腐蚀行为及氧化层组成和结构的影响。结果表明：经700 ℃氧化100 h后，预氧化试样的氧化增重仅有0.47 mg?cm^-2；预氧化处理的Ti-48Al-2Nb-2Cr合金表面为多层氧化物结构，最外层形成了连续、致密的TiO₂层，并且氧化层与基体具有良好的结合力，从而有效阻止了熔盐向合金内部扩散，进而显著提高了合金的抗热腐蚀性能。因此，通过预氧化的方式可提高TiAl合金表面的抗热腐蚀性能。

Abstract:

To protect Ti48Al2Nb2Cr alloy from hot corrosion at elevated temperatures， a compact protective coating was prepared on the surface of alloy by pre-oxidation process. The effects of pre-oxidation treatment on the hot corrosion behavior and oxide layer composition and structure of Ti48Al2Nb2Cr alloy were studied in the mixed salt consisting of 75 wt.% Na₂SO₄ and 25 wt.% NaCl at 700 ℃ for 100 h. The results showed that the surface of the pre-oxidized Ti48Al2Nb2Cr alloy had a multi-layer oxide structure， and a continuous and dense TiO₂ layer was formed in the outermost layer. At the same time， the oxide layer had a good adhesion with the matrix， which could effectively prevent the inward diffusion of molten salt， thus significantly improving the hot corrosion resistance of the alloy. After oxidation at 700 ℃ for 100h， the mass gain of the PO-Ti48Al2Nb2Cr alloy was only 0.47 mg·cm^-2. Therefore， the anti-hot corrosion performance of TiAl alloy could be effectively improved via pre-oxidation process.