纳米CeO_2改性渗Cr涂层在5%O_2-0.1%SO_2-N_2气氛中的高温氧化

OXIDATION OF A NANO-CeO_2- DISPERSED CHROMIZING COATING IN 5%O_2-0.1%SO_2-N_2 ATMOSPHERE

用Ni-CeO2 复合电镀后包埋渗Cr的方法在低碳钢上制备了CeO2 改性的渗Cr涂层 .在 90 0℃、含与不含0 1%SO2 的 5 %O2 +N2 气氛中 ,与低碳钢渗Cr及镀Ni渗Cr涂层的氧化行为进行了对比研究 ,获得如下结果 :(1)CeO2 改性的渗Cr涂层抗高温氧化性能最好 ,低碳钢渗Cr涂层最差 ;(2 )SO2 促进了碳钢渗Cr及镀Ni渗Cr涂层的退化 ,而对CeO2 改性渗Cr涂层的氧化影响不大 .利用光学显微镜 (OM)、X光衍射 (XRD)、扫描电镜与能谱 (SEM/EDAX)对氧化前后试样分析表明 :CeO2 通过细化改性渗Cr涂层晶粒以及改变渗层Cr含量 ,避免氧化膜 /涂层界面附近由于Cr的贫化而析出Ni2 Cr相 ,延缓α相向γ相的快速转变 ,来提高氧化膜的抗剥落性能 ;同时 ,CeO2 还通过改变涂层氧化膜的生长机制降低了SO2

A novel CeO 2-dispersed chromizing coating was fabricated through prior electroplating a Ni-CeO 2 composite film on a mild steel and then chromizing.Comparison of the oxidation of the CeO 2-dispersed chromizing coating with the chromizing mild steel with and without Ni pre-plating was conducted at 900℃ in 5%O 2-N 2 atmospheres with and without adding 0.1% SO 2 respectively.There were two observations:(1)among the above three chromizing coatings the one with CeO 2 dispersion exhibited the best oxidation resistance,while the worst one was the chromiging mild steel,(2) SO 2 accelerated the oxidation of the CeO 2-free coatings,but its effect on the oxidation of CeO 2-modified coating was not significant.The samples before and after oxidation were investigated using OM,XRD and SEM/EDAX.The results indicated that the presence of CeO 2 led to the formation of the chromizing coating with finer- grained structure and higher Cr content in comparison to the coating on the Ni-plated steel.This prevented the precipitation of Ni 2Cr phase at the scale/coating interface due to fast depletion of Cr,and the rapid α→γ phase transformation,leading to an improvement of the coating's resistance against scale spallation.In the meantime,CeO 2 may change the mechanism of scale growth,which minimized the effect of SO 2 on the oxidation of the chromizing coating.