(北京航空航天大學(xué) 特種功能材料與薄膜技術(shù)北京市重點(diǎn)實(shí)驗(yàn)室，北京 100191)
摘 要: 在800 ℃、75%Na2SO4和25%NaCl的熔融鹽環(huán)境中，對(duì)名義成分為Ti-48Al-2Cr-2Nb的γ-TiAl合金進(jìn)行高溫腐蝕實(shí)驗(yàn)。通過氧化動(dòng)力學(xué)分析、掃描電鏡觀察及X射線衍射分析，研究全片層γ-TiAl合金的氧化腐蝕行為，以及高溫腐蝕性環(huán)境對(duì)合金內(nèi)部微觀組織的選擇性腐蝕機(jī)理。結(jié)果表明：在高溫熔融鹽腐蝕環(huán)境下，γ-TiAl合金主要形成由TiO2和Al2O3組成的氧化膜層，且高溫熔融鹽環(huán)境對(duì)合金內(nèi)部微觀組織存在明顯的選擇性腐蝕，即腐蝕路徑沿α2與γ兩相界面進(jìn)入合金內(nèi)部，并優(yōu)先腐蝕α2相片層及γ相片層中的某些亞結(jié)構(gòu)。合金片層組織中α2相與γ相間的抗氧化性能差異，以及熔融鹽腐蝕性環(huán)境參與氧化中間反應(yīng)并加速合金氧化過程是發(fā)生選擇性腐蝕的主要原因。
關(guān)鍵字: γ-TiAl合金；高溫腐蝕；顯微組織
molten salt environment
（Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology,
Beihang University, Beijing 100191,China）
Abstract:The high temperature corrosion tests of Ti-48Al-2Cr-2Nb γ-TiAl alloy were carried out with salt mixture of 75% Na2SO4 and 25% NaCl (mass fraction) at 800 ℃. The high temperature corrosion behavior of the alloy and the selective corrosion mechanism of microstructure were also discussed, via oxidation kinetics analysis, scanning electron microscope observation and X-ray diffraction analysis. The results show that the oxide layer mainly composed of TiO2 and Al2O3 is formed during high temperature corrosion. The corrosion path initiates at the lamellar interfaces, and α2 phases as well as some substructures in γ phase have priorities of corrosion in molten salt environment, which proves the existence of the selective corrosion of lamellar structure. The difference in oxidation resistance between the two phases and the participation of molten salts in intermediate reaction, which accelerates the oxidation process, are considered as the main reasons of selective corrosion of microstructure in the alloy.
Key words: γ-TiAl; high temperature corrosion; microstructure
