钇离子注入对Co-40Cr(wt%)合金氧化行为的影响

INFLUENCE OF YTTRIUM IMPLANTATION ON OXIDATION BEHAVIOR OF Co-40Cr(wt%) ALLOY

研究了Co－40Cr（wt％）合金在空气中、1000℃下的恒温氧化和循环氧化行为。通过SEM／EDXA等测试手段，对合金表面形成的氧化膜进行了分析．并且，与合金表面离子注入3×1016Y+／cm2和3×1017Y+／cm2后的氧化行为进行了比较．结果表明，注钇和未注钇样品氧化后表面形成的都是纯Cr2O3膜，离子注钇明显改善了合金的氧化性能．其原因主要是稀土钇能以离子或细小氧化物颗粒的形式偏聚于Cr2O3晶界，通过阻碍氧化膜中Cr3＋阳离子向外扩散，降低了氧化膜的生长速率．同时，通过阻碍氧化膜／合金界面附近"kirkendall"空洞的形成，增强了氧化膜与合金基体之间的结合强度，提高了氧化膜的粘附性及合金的抗氧化性能．

Isothermal and cyclic oxidation behavior of Co-40Cr(wt%) alloy in air at 1000℃ was evaluated.SEM/EDXA was used to examine the scale formed on the alloy. By comparing the different oxidation behavior of Co-40Cr alloys which were implanted with 3×1016y+/cm2 and 3×1018Y+/cm2 or unimplanted,it was found that only Cr2O3 scale was formed on all alloys with and without implanted yttrium, but the oxidation resistance of the alloy was greatly improved by yttrium implantation. SIMS method was also used to examine the yttrium concentration depth profile. The main reason for the improvement is that yttrium can segregate at Cr2O3 grain boundaries, this may change the scale growth mechanism from predominant Cr3+ canon outward diffusion to predominant O2- anion inward diffusion, and greatly decrease the diffusion rate. In the mean time, yttrium implantation inhibited the formation of 'Kirkendall' holes at the scale/alloy interface, thus remarkably enhanced the adhesion of the scale formed on yttrium-implanted Co-40Cr alloy.