Al2O3改性的渗铬涂层制备与氧化性能研究

Preparation and Oxidation Performance of an-Al2O3-Modified Chromizing Coating

摘要:

采用在Ni基上复合电镀Ni-Al2O3纳米复合涂层后在1100 ℃扩散渗铬3 h的方法，制备Al2O3改性的渗铬涂层。作为对比，采用相同的工艺在单Ni镀层上直接渗铬，获得一种不含Al2O3纳米粒子的渗铬涂层。SEM/EDS和TEM结果表明：Al2O3纳米颗粒均匀分布在Ni纳米晶中， 纳米Al2O3颗粒的加入不仅细化基体Ni的晶粒尺寸，而且明显抑制在渗铬过程中涂层晶粒的长大。900 ℃, 120 h的氧化试验结果表明：与不含Al2O3纳米粒子的渗铬涂层相比，Al2O3改性的渗铬涂层所具有的细晶结构促进了保护性氧化物形成元素Cr沿晶界向氧化前沿的快速扩散，从而有利于保护性Cr2O3氧化膜的快速形成，同时改变氧化膜的形成过程，降低氧化速度，使得Al2O3改性的渗铬涂层表现出更优异的抗氧化性能。并对Al2O3渗铬涂层的组织及氧化机制进行了分析

Abstract:

An Al2O3-modified chromizing coating was produced by chromizing as-electrodeposited Ni-Al2O3 nanocomposite film using pack cementation method at 1100 oC for 3 h. For comparison, the chromizing was also performed in the same condition on as-deposited Ni film without Al2O3 nanoparticles. SEM/EDAX and TEM results indicate that the co-deposited Al2O3 nanoparticles are homogeneously dispersed in the finer-grain nanocrystalline Ni grains. At the same time, the co-deposited Al2O3 nanoparticles restrain the grain growth during chromizing by anchoring the movement of grain boundaries, which leads to the formation of finer grained chromizing coating. It is indicated from oxidation at 900 ℃ for 120 h that although both two chromizing coatings grow chromia scales during oxidation, the Al2O3-modified chromizing coating exhibits an increased oxidation resistance due to the accelerated chromium diffusion to the oxidation front via the increased grain boundaries and consequently accelerated the formation of a continuous chromia layer in a shorter transient time, together with the change of the oxidation mechanism. The effect of Al2O3 on the microstructure and oxidation of the chromizing coatings are discussed in the detail