表面粗糙度对Ni-20Cr合金高温氧化行为的影响

Effect of surface roughness on high temperature oxidation behavior of Ni-20Cr alloy

表面粗糙度作为重要的参数,对合金高温氧化膜剥落有重要影响。为此,研究表面粗糙度对Ni-20Cr合金氧化20 h内的氧化动力学及氧化膜剥落行为的影响。通过热重法绘制动力学曲线,可以看出2.5μm砂纸磨痕的合金氧化速率明显低于90μm砂纸磨痕的氧化速率。利用扫描电镜观察氧化膜表面形貌,显示粒状的氧化物在2.5μm砂纸磨痕合金表面生成,而刻面状的氧化物在90μm砂纸磨痕合金表面形成。XRD分析表面,在2.5μm砂纸磨痕合金表面生成的氧化物为Cr2O3,在90μm砂纸磨痕表面形成的氧化物为NiO。结果表明:平滑的Ni-20Cr合金表面有利于生成保护性的Cr2O3而不发生脱落,具有优良的抗氧化性能。

This paper is motivated by the study on the effect of initial surface roughness on the oxida- tion kinetics and oxide-scale spallation during oxidation of Ni-20Cr alloy up to 20 h thanks to the recogni- tion the that as an important parameter, surface roughness has a significant effect on oxide-scale spallation during high temperature oxidation. The oxidation kinetics measured by thermogravimetry （TGA）suggests that the 2.5 μm polished surface has a much lower oxidation rate than does 90 μm polished surface. Top- view image, observed by scanning electron microscope （ SEM）, shows the formation of granular oxide formed in the case of 2.5 μm polished surface, and generation of faceted oxide on samples with 90 μm polished surface. XRD results indicate that Cr2O3 forms on samples with 2.5 μm polished surface, and NiO forms on rougher surface （90 μm）. It follows that smooth surface is in favor of the formation of pro- tective Cr2O3 on Ni-20Cr alloys, which displays excellent oxidation resistance.