材料期刊网

作者研究了添加0.1％和0.8％Ce的Ni—Cr—Cu合金在空气中1200℃100小时等温氧化和500小时循环氧化。Ni—Cr—Cu合金中添加微量Ce后,显著降低了氧化速率,增加了氧化膜的剥落抗力。氧化速率降低是添加Ce后各种效应综合作用的结果。它们是:(1)由于Cr的扩散加快,富Cr保护膜更迅速形成;(2)聚集在膜/合金界面附近的含Ce氧化物与空位复合,减少了膜/合金界面的空洞;(3)固溶于氧化膜中的含Ce氧化物阻碍了Cr~(3+)沿氧化物晶界的短程扩散。 提高耐剥落抗力主要原因是:(1)添加Ce使氧化膜晶粒变细,从而改善了塑性变形和适应热应力的能力;(2)0.8Ce合金中稀土氧化物“钉扎”(Keying)作用改善了膜与合金粘附性,并改变了热应力的分布状态。

The authors have investigated the effect of the addition of 0.1% and 0.8% Ce on isothermal oxidation of Ni—Cr—Cu for 100 hours at 1200℃in air, and on cyclic oxidation for 500 hours at 1200℃ in air. It is thought that a small amount of addition of cerium to the Ni—Cr—Cu alloys reduces the oxidation rate considerably in the later stage. The spalling resistance of the scale is also increased with the addition of cerium. The decrease of oxidation rate results from a combination of various effects, They are: (1) Cr rich protective scale is more rapidly formed because of faster diffusion of chromium; (2) cerium-containing oxide concentrating near scale/alloy interface complexes with vacancies, so that voids at scale/alloy interface are reduced; (3) cerium-containing oxide dissolved in the scale blocks the short-circuit diffusion of Cr~(3+) along oxide grain boundries. The main causes for the increase of spalling resistance with cerium addition are: (1)the grains of scale are refined by addition of cerium, thereby improving the ability of such scales to plastic deformation and to accommodation to thermal stress; (2) the keying effect of rare-earth oxide in the 0.8% Ce-containing alloy improves oxide adherence with substrate, and changes the distribution state of thermal stress.