常压和低压环境下反应等离子喷涂Al/Fe_(2)O_(3)复合材料的合成机理

Synthesis Mechanism of Reactive Plasma Sprayed Al-Fe_(2)O_(3) Composites Under Atmosphere and Low-Pressure Ambient Conditions

反应等离子喷涂(RPS)技术被广泛用于制备不同使用需求的高性能涂层材料。基于经典的铝热反应原理,采用反应等离子喷涂技术分别在近常压和低压环境下制备了Al-Fe_(2)O_(3)涂层,通过XRD、SEM和EDS等分析方法对所制备涂层的相组成和显微结构进行了表征。阐明了Al和Fe_(2)O_(3)在加热和反应等离子喷涂过程中的反应机理。DTA分析结果表明,氩气氛下长时间热处理产物主要为Fe、Al_(2)O_(3)和FeAl相。然而,在等离子喷涂过程中,低氧分压环境导致中间产物FeAl2O4铁尖晶石相的生成,由于近常压等离子喷涂过程的冷却速度极快,该相可以保留在最终涂层结构中。而低压反应等离子喷涂等离子体射流飞行距离长,还原性气氛和较长的反应时间将其进一步还原为FeAl相。

Reactive plasma spray(RPS) technique is frequently used to prepare high-performance coating materials with different application requirements. Based on the classical thermite reaction, the Al-Fe_(2)O_(3)coatings were fabricated by RPS under atmosphere and low-pressure ambient. The phase compositions and microstructures of the obtained coatings were characterized by XRD, SEM and EDS. Moreover, the reaction mechanisms of thermite reaction of Al and Fe_(2)O_(3)in sintering and RPS process were elucidated. The DTA analysis results indicate that the main sintering products are Fe, Al_(2)O_(3)and FeAl phases under prolongated reaction condition with Ar gas protetion. However, low oxygen partial pressure leads to the formation of FeAl2O4hercynite phase as an intermediate product during spraying. In atmosphere-reactive plasma spraying(A-RPS), such phase can be retained in the final coating under extremely fast cooling rate. Furthermore, it can also be continuously reduced to FeAl phase in the low pressure Ar-H2ambience due to the deoxidation effect and long in-flight distance of plasma jet.