不同组织形态的Rene80合金在含硫气氛中受载时的高温腐蚀

HIGH TEMPERATURE CORROSION OF THE RENE 80 SUPERALLOY WITH DIFFERENT MICROSTRUCTURES IN THE SULFUR-CONTAINING ATMOSPHERE UNDER APPLIED LOAD

研究了普通铸造与定向凝固的Rene 80高温合金在含SO_2气氛中受载时的高温腐蚀行为。研究结果表明:在含SO_2气氛中普通铸造合金沿晶界发生灾害性硫化-氧化腐蚀,并导致合金早期断裂。而定向凝固合金由于横向晶界的消除,并不发生上述灾害性硫化-氧化腐蚀。因此在高温腐蚀环境中受载时的合金破坏是高温腐蚀、蠕变以及合金组织形态交互作用的结果。

The high temperature corrosion behaviour in SO_2-contaminated atmosphere of Rene 80 superalloy with two different microstructures, i.e. equiaxed-grain structure by conventional casting (C. C.) or columnar-grain by directional solidification (D. S.) was studied. Analysis were carried out on the longitudinal sections and fracture surfaces of the tested specimens by SEM, EDAX and EPA. Similar tests were also conducted in air in order to compare with the results in SO_2-containing atmosphere. The results showed that severe sulphidation-oxidation corrosion along the grain boundaries of the conventional-cast Rene 80 alloy occurred in SO_2-containing environment, which led to premature failure of the alloy. However, owing to the elimination of transverse grain boundaries, the sulphidation-oxidation corrosion of the directionally solidified superalloy was hardly observed, and the rupture life of the alloy in SO_2-containing environment kept the same level as that in air. It is suggested that the damage of the superalloy in corrosive environment at high temperature under applied load was due to the interaction of high temperature corrosion-creep and mierostructure of the superalloy.