微量元素对低膨胀Fe-Ni基高温合金抗氧化性能的影响

为了保持低的膨胀系数,低膨胀GH909合金中不含Cr,导致合金的抗氧化性能较差为了解决这一问题,在GH909合金的基础上调整成分,加入少量Cr和稀土元素Y与La等,并提高Co/(Co+Ni)比例,使合金在膨胀系数基本未变的情况下,抗氧化性能得到较明显的改善用X射线衍射、金相显微镜、扫描电镜等检查了合金的氧化层,发现GH909合金氧化层很厚,其主要成分为Fe3O4,Fe3O2等,氧化层组织较疏松,有内氧化现象.加入Cr和稀土元素的合金氧化层较薄,氧化层主要成分还有Cr2O3等,氧化层组织致密,未见内氧化.温度愈高,Cr和稀土的有益效果愈明显,它们有效地抑制了氧的扩散.

THE OXIDATION-RESISTANCE PROPERTIES OF LOW-EXPANSION SUPERALLOYS

To obtain low thermal expansion coefficient, the alloying element Cr is removed from the alloy GH909, which made the oxidation resistance property of GH909 very poor. To solve this problem, a small amount of alloying element Cr, and rare earth elements Y and La were added into the alloy GH909 and the rate of Co/(Co Ni) was increased, these made the oxidation resistant property improved obviously, while the expansion coefficient keeps unchanged obviously. The X-diffraction, optical and electrical microscope were used to inspect the structure of oxidation layer. For the alloy GH909 the layer of oxidation is very thick and the main constitution is Fe3O4, Fe3O2 and so on f the structure of oxidizing layer is looser and the interior-oxidation appeared. For the alloy adding small amount of Cr and rare earth elements on the GH909, the layer of oxidation is very thin, the main constitution includes Cr_2O_3, aside from Fe_3O_4, Fe3O2, the structure of oxidation layer is very closed and the interior-oxidation disappeares. The elements of Cr, Y and La hinder the diffusion of element O effectively, and the above beneficial effect increases with increasing the temperature.