材料期刊网

本文研究了Na_2SO_4,NaCl混合介质对一种镍基高温合金持久性能的影响。试验结果表明:75％Na_2SO_4+25％NaCl的混合介质使合金在750,800℃的持久寿命缩短,断裂塑性降低,持久曲线左移;90％Na_2SO_4+10％NaCl的混合介质对750℃的持久性能无明显影响;95％Na_2SO_4+5％NaCl的混合介质对800℃的持久性能也无明显影响;电解抛光增加合金对热盐腐蚀的敏感性。经金相、扫描电镜、电子探针等分析表明:热盐介质对持久性能影响是通过破坏试样表面保护性氧化膜使基体金属被氧化,且在应力作用下,氧化沿晶界向内部深入而造成。其影响程度与表面状态、盐的组分、应力大小有关。

A study was made of the corrosive effect of hot salt mixed by Na_2SO_4 and NaCl on the creep rupture life of a Ni-base superalloy. It was shown that for such superaUoy the rupture life is shortened, the rupture elongation is reduced and the creep rupture curve is shifted toward the left when its specimens coated with a mixture of 75% Na_2SO_4 and 25% NaCl layer and heated under testing temperatures of 750 and 800℃. No marked influence upon their creep rupture lifes of specimens seems to be resulted either with 90% Na_2SO_4+10% NaCl under 750℃ or with 95% Na_2SO_4+5% NaCl under 800℃. The susceptibility of the superalloy to hot salt corrosion is increased by treatment of electrolytic polishing. Observations under metalloscope, SEM and EMPA revealed that the effect of the hot salt corrosion on the creep rupture life of the superalloy is substantially due to destroying of the protective oxide film on its surface, and then caused by oxidization along the grain boundaries under stress applied. Hence, the harmfulness of this corrosion effect may be concerned with the surface condition, salt composition and stress applied at elevated temperatures.