热处理温度对G3合金耐点蚀性能的影响

Effect of Heat Treatment Temperature on Pitting Resistance of G3 Alloy

摘要:

采用SEM、EDS、TEM等方法研究了不同热处理温度对G3合金组织形态及晶界析出相的影响；进而利用浸泡模拟实验和电化学实验，分析组织变化以及晶界析出相对G3合金耐点蚀性能的影响。结果表明：晶界析出相对G3合金耐点蚀性能起着关键的作用。低温退火时由于G3合金析出相变少，组织均匀性增加，G3合金耐点蚀性能有所增加。而随着退火温度的进一步升高，在晶界生成大量的析出相。析出相的大量生成使得G3合金组织不均匀性增加，同时造成贫Mo区域钝化膜稳定性变差，容易发生局部活化溶解，点蚀敏感性明显增加。

Abstract:

The effect of heat treatment temperature on the microstructure and precipitate at grain boundary of G3 alloy was investigated by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and transmission electron microscope (TEM). And then, the effects of the microstructure change and precipitate at grain boundary on the pitting resistance of G3 alloy were studied by immersion tests and electrochemical measurements. The results show that the pitting resistance of G3 alloy is mainly affected by the precipitates at grain boundary. The pitting resistance of G3 alloy is increased after annealing at low temperature (500 oC), due to fewer precipitates in G3 alloy and the improved microstructure uniformity. With the further increasing annealing temperature, there are a large number of precipitates formed at the grain boundary, which can increase the microstructure inhomogeneity of G3 alloy, and the stability of the passive film in poor Mo region becomes worse. It is prone to local active dissolution in poor Mo region, and the susceptibility to pitting of G3 alloy increases significantly.