短时氧化对定向凝固高温合金不同取向腐蚀性能的影响

Influence of Short-time Oxidation on Corrosion Properties of Directionally Solidified Superalloys with Different Orientations

为了研究定向凝固高温合金不同取向氧化前后的常温腐蚀性能,选择镍基高温合金DZ125和钴基高温合金DZ40M在1050℃下进行不同时间的短时氧化,研究合金不同取向的氧化行为;对氧化前后合金在3.5%NaCl溶液中进行电化学实验,研究氧化对定向凝固高温合金不同取向常温腐蚀性能的影响。结果表明:定向凝固高温合金晶界或亚晶界附近容易发生局部腐蚀,纵截面晶界和亚晶界面积分数小,因此耐蚀性优于横截面;与合金横截面相比,纵截面晶界结构不利于扩散,故其氧化速率小于横截面;短时氧化后在合金表面生成分层结构的氧化物,对合金起到保护作用,一定程度上提高耐蚀性。

In order to investigate the corrosion performance on intersecting and longitudinal surfaces of unoxidized and oxidized directionally solidified superalloys,Ni-base directionally solidified superalloy DZ125 and Co-base directionally solidified superalloy DZ40 M were selected.Oxidation behavior on both alloys with different orientations was investigated at 1050℃ at different times,simulating the oxidation process of vanes or blades in service;subsequent electrochemical performance in 3.5%NaCl aqueous solution was studied on two orientations of unoxidized and oxidized alloys,simulating the corrosion process of superalloy during downtime.The results show that grain boundaries and sub-boundaries of directionally solidified superalloys are susceptible to corrosion and thus longitudinal surface with lower area fraction of grain boundaries has higher corrosion resistance.Compared to intersecting surface of alloys,the structure of grain boundaries of longitudinal surface is less conducive to diffusion and thus the oxidation rate on longitudinal surface is lower.Formation of oxide layers on alloys after short-time oxidation provides protective effect and enhances the corrosion resistance.