Ti_3Al及其渗铝涂层的热腐蚀性能

采用电化学方法并结合各种物相分析技术研究了Ti_3Al金属间化合物在熔融(Na,K)_2SO_4-NaCl中的热腐蚀行为及渗铝涂层对其耐蚀性能的影响。结果表明,Ti_3Al耐热腐蚀性能较差。形成了外层为TiO_2,中间层为富铝的TiO_2-Al_2O_3复合层,内层为富铌的Nb_2O_5-TiO_2-Al_2O_3层的三层结构。渗铝涂层能在合金表面形成Al_2O_3氧化膜而明显改善Ti_3Al的耐蚀性能。

MOTLEN SALTS INDUCED HOT CORROSION OF Ti_3Al INTERMETALLIC COMPOUND AND ITS ALUMINIDE COATING

Hot corrosion of Ti_3Al and its aluminide coating was studied by electrochemical techniques combined with physical analyses. It is observed that hot corrosion resistance of Ti_3Al is inferior to that of HK40 alloy. The corrosion product scale is of a three-layer structure with a outer scale of TiO_2 ,an intermediate layer of Al_2O_3-TiO_2 rich in Al_2O_3 and an inner layer of Nb_2O_5-TiO_2-Al_2O_3 rich in Nb_2O_5 . The inferior protectiveness of the intermediate layer may result from the presence of Ti~(4+) in Al_2O_3 , which promotes the diffusion of oxygen. Rapid outward diffusion of Ti and inward diffusion of oxygen are believed to be responsible for the fast thickening of the corrosion product scale. It is proved that aluminide coating can provide better hot corrosion resistance.This effect is attributed to the rapid formation of a thin Al_2O_3 film on its surface.