Ni-20Cr/hBN自润滑材料的高温氧化行为

High temperature oxidation behaviours of Ni-20Cr/hBN self-lubricating composites

采用粉末冶金法制备六方氮化硼(hBN)含量为8%、10%和12%(质量分数)的Ni-20Cr/hBN自润滑复合材料,研究其在600、700和800℃的高温氧化行为,绘制氧化动力学曲线,并利用XRD和SEM分析氧化层的成分和形貌。结果表明:Ni-20Cr/hBN复合材料在600℃氧化300 h后氧化反应不明显;在700和800℃氧化300 h后出现较明显的氧化产物,主要有Cr2O3、NiCr2O4和CrBO3。氧化反应前100 h的氧化行为符合氧化增量动力学曲线,800℃的氧化抛物线速率常数比700℃的高一个数量级;而氧化100 h后,由于B2O3的熔融,试样质量保持不变或甚至呈下降趋势;在700℃下连续氧化膜基本形成,起到较好的保护作用,在800℃时氧化膜出现不同程度的腐蚀。

The Ni-20Cr/hBN self-lubricating composites were prepared by powder metallurgy with hBN contents of 8%, 10% and 12% （mass fraction）. Its oxidation behaviors were studied in air at 600, 700 and 800 ℃. The oxidation kinetics curves were gained, and the oxide compositions and morphologies were analyzed by XRD and SEM. The results show that the oxidation of Ni-20Cr/hBN composites oxidized at 600 ℃ for 300 h is not obvious. The oxide products consist of Cr203, NiCr204 and CrBO3 at 700 and 800 ℃ for 300 h. The kinetic curves of the composites obey the parabolic rate law at the beginning oxidation of 100 h, and the oxidation parabolic rate at 800 ℃ is a magnitude higher than that at 700 ℃. Meanwhile, the masses of Ni-20Cr/hBN composites become stable or even decrease after 100 h due to melt of B203. The oxide scales are complete and do well in protection at 700 ℃, while are corroded to some extend at 800 ℃.