A Basic Study of Developing Refractory Metals for Waste Burner

利用热重分析仪研究了不同金属在HCl气氛中的高温腐蚀行为，结果表明，纯Fe在700 ℃时的腐蚀速率高于纯O2气氛。而在900 ℃以上，尽管有挥发性FeCl_2的生成，但在HCl气氛中的腐蚀速率较低。这些现象是由于Fe的氧化和氯化同时进行的结果。在750 ℃ ~ 850 ℃的温度范围内，在含HCl的气氛中，Cr_2O_3的生成大大加快，而在其它温度范围内，腐蚀速率与纯O_2中的腐蚀速率基本相同。在700 ~ 1000 ℃的温度范围内，纯Ni在含HCl的气氛中，由于生成了挥发性的NiCl_2，腐蚀过程中试样质量逐渐减少。试验后在试样上观察到薄的NiO氧化皮层。在1%HCl气氛中的腐蚀速率高于纯O_2气氛。结果表明，Fe-Cr合金在HCl气氛中的腐蚀是由Ni的氧化和氯化共同作用的结果;在1%HCl气氛中，随着Cr含量的增加，Fe-Cr合金的腐蚀速率降低。而含几个Cr的合金，其腐蚀速率比纯O_2中的高。结果表明，元素Cr集中在金属/氧化皮界面周围的氧化皮中。因此，Fe-Cr合金的抗氧化性能是由于在金属/氧化皮界面上形成了Cr_2O_3膜。

High temperature corrosion behaviors of various metals were examined in an atmosphere including HCI by a thermogravimetric apparatus.For pure Fe, the corrosion rate at 700ﾟC in the atmosphere including HCI was higher than that in pure O_2. However, the corrosion rate above 900ﾟC was lower in the atmosphere including HCI in spite of the formation of a volatile FeCl_2. These phenomena were due to the simulaneous progress of oxidation and chlorination of Fe.For pure Cr. the formation of Cr_2O_3 was tremendously accelerated in the temperature region from 750ﾟC to 850ﾟC in the atmosphere including HCI.However, in the other temperature region the corrosion rate was almost the same as that in pure O_2. These were thought to be attributed to the fact that the formation of CrCl_2 playd an important role on the corrosion behavior.For pure Ni, the corrosion proceeded with a decrease in mass of the specimen due to the fotmation of a volatile NiCl_2 at the temperatures from 700ﾟC to 1000ﾟC in the atmosphere including HCl. A thin NiO scale layr was observed on the specimen after the test. The corrosion rate in an 1%HCl atmosphere was higher than in pure O_2. These suggested that the corrosion in the atmosphere including HCI was attributable to both oxidation and chlorination of Ni.For Fe-Cr alloys, the corrosion rate in an 1%HCl atmosphere was decreased with an increase in Cr content. For the alloys containing several percent Cr, however, the corrosion rates were higher than those in pure O_2. It was revealed that elemental Cr was concentrated in the scale around the metal/scale interface. Therefor, such higher oxidation resistance for the Fe-Cr alloys was due to the formation of Cr_2O_3 film at the metal/scale interface.