HIGH TEMPERATURE OXIDATION OF SOME 2ND-GENERATION SINGLE CRYSTAL NI-BASE SUPERALLOYS AT 1000 °C IN AIR AND MOISTURE

摘要

Some 2nd generation single crystal Ni-base superalloys (PWA 1484, PWA 1487, Rene' N5, Rene' N5 + Y and CMSX 4 + La, Y) were oxidized in different atmospheres (air, air + 10% steam, air + 30% steam) at 1000 °C for 100h. The experiments were carried out in order to compare the oxidation behavior of the listed alloys in different atmospheres and also to study the influence of moisture on the oxidation behavior. The formed crystalline compounds were detected by using X-Ray Diffraction (XRD). The morphology of the grown oxides was investigated by SEM (Scanning Electron Microscopy) imaging of prepared cross-sections. For all oxidation experiments an Al_2O_3 layer on the interface substrate-oxide was observed, and depending on the atmosphere and the alloy different spinels and oxides were observed. The thickness of these oxides was dependent on the oxidation atmosphere. The experiments reveal that the addition of certain alloying elements such as Yttrium, Lanthanum as well as the microstrucrure play an important role on the oxidation behavior of the alloys. The role of the alloying elements in the oxidation mechanisms will be discussed.