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A Study of the Microstructure and Oxidation Behavior of CrN Thin Films
Ching, Wang Chun
|關鍵字:||CrN;氮化鉻;microstructure;Oxidation Behavior;Residual Stress;微結構;氧化行為;殘留應力||出版社:||材料工程學研究所||摘要:||
CrN coatings were deposited by unbalanced magnetron sputtering (UBM) on AISI 304 stainless steel. The oxidation behavior of the CrN-coated steel at elevated temperatures was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the hardness of the films was measured by Vickers hardness indentor. In addition, the residual stress of the CrN-coated steel was determined by deflection method.
The residual stress in the as-deposited CrN films was measured to be about 4.25 GPa. From SEM results, it can be found that the surface of the specimens oxidized in air below 500℃ for 60 min remains similar to the as-deposited specimens, and the surface roughness of the CrN coatings increases with oxidation temperatures at above 600℃. XRD and TEM results indicate the phase transformation from CrN to Cr2N occurs at 500℃, and the extent of β-Cr2N and Cr2O3 and the grain size of the phases increase with the oxidation temperature. Not only the Cr2O3 oxides but also the phase transformation of CrN are observed during the oxidation process of the coatings.
The hardness of the specimen oxidized at 300℃ is almost the same as the as-deposited specimens, and the hardness of the CrN-coated steel increases with the oxidation temperatures up to 700℃. This can be explained by the fact that the hardness of Cr2N is higher than that of CrN.The sharp decrease in the hardness of the specimens oxidized at 800℃ is partly due to the grain growth of the CrN and Cr2N coating layer at high temperature.
|Appears in Collections:||材料科學與工程學系|
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