Al_2O_3和Y_2O_3改性的渗铬涂层循环氧化性能

Cyclic oxidation performance of Al_2O_3 and Y_2O_3-modified chromizing coatings

采用在Ni基上分别电镀Ni-Al2O3复合涂层,单Ni镀层和Ni-Y2O3复合涂层+1100℃扩散渗铬3 h的方法,制备了3种渗铬涂层,并对其进行循环氧化实验。SEM分析表明:与Y2O3微米粒子相比,Al2O3纳米颗粒更加均匀分布在Ni纳米晶中,而且抑制了渗铬过程中涂层晶粒的长大。氧化实验表明:与普通渗铬涂层相比,Al2O3改性的渗铬涂层所具有的细晶结构促进了氧化初期保护性Cr2O3氧化膜的快速形成,随后涂层晶界处Al2O3抑制了Cr的外扩散,降低了氧化速度并提高涂层的抗剥落性能;微米Y2O3粒子通过溶解和重新析出来抑制渗层晶粒长大,且具有稀土活性元素的效应,从而提高渗层的抗循环氧化性能。

Three chromizing coatings were produced by chromizing on electrodeposited Ni-Al2O3nano composite coating,pure Ni film and Ni-Y2O3composite coating using pack cementation method at 1100 ℃ for 3 h.The oxidation performance of these coatings was studied by the cyclic oxidation experiment.SEM observation indicates that compared to Y2O3microparticles,the deposited Al2O3nanoparticles are not only homogeneously dispersed in nanocrystalline Ni grains but also retarded the grain growth in the coatings during chromizing.Oxidation experiment results indicate that compared to chromizing coating formed on pure Ni film,the Al2O3modified chromizing coating exhibite an increased cyclic-oxidation resistance due to the fast formation of a continuous chromia layer,together with the retarding effect of Cr outward diffusion by Al2O3particles along grain boundaries in the chromizing coating.The dissolution and precipitation of Y2O3 microparticles not only have the same effect as Al2O3particles to improve the cyclic-oxidation resistance,but also have'reactive element effect'to increase the cyclic-oxidation resistance.