CAREER: Structure/ Property Relationship of Adherent SiC Coated Fe-Ni-Cr Alloys in Ethylene Pyrolysis Environments

乙烯是世界上产量最大的化学商品之一，由于从乙烯衍生的产品正在取代包装、建筑、汽车和其他应用中的传统材料，到2010年，对乙烯的需求将超过1亿吨。碳氢化合物的高温热解已经进行了半个多世纪，每年仍消耗超过5亿美元的Fe-Ni-Cr基管材产品。其罪魁祸首是催化结焦，导致管壁温度升高、换热不良、压降增大、管内直径减小、管子堵塞。在役操作和除焦周期的结合使管道寿命缩短了4-6年。该学院早期职业发展(CALEAR)奖将集中于通过(1)通过脉冲激光沉积将附着的碳化硅涂层应用于传统上用于乙烯热解服务的管材的内径来限制催化结焦形成，(2)确定碳化硅涂层的Fe-Ni-Cr管材在使用过程中经历哪些微观结构变化，以及(3)确定微观结构的变化对管材的使用寿命有何影响，从而集中于提高工艺效率。由于扩散是涂层自我修复机制的基础，也是涂层通过与基材相互扩散而退化的机制的基础，因此了解该体系的扩散特性是非常重要的。该计划还将通过改进教学方法、课程开发、外展和指导，为终身卓越的教育奠定基础。这方面的努力突出表现在ASM批准的、在PIS指导下于2004年开始的东北教师训练营。

The demand for ethylene, one of the highest production chemical commodities in the world will exceed 100 million metric tons by 2010 as products derived from ethylene are displacing conventional materials in packaging, building, automotive and other applications. High temperature pyrolysis of hydrocarbons has been practiced for over a half century and still over a half billion dollars of Fe-Ni-Cr based tubular products are consumed each year. The culprit, catalytic coke formation, leads to increased tube wall temperature, poor heat transfer, increased pressure drop, inner tube diameter reduction, and tube plugging. The combination of in- service operation and decoking cycles has reduced tube life by 4-6 years. This Faculty Early Career Development (CAREER) award will concentrate on improving process efficiency by (1) limiting catalytic coke formation by applying adherent SiC coatings via pulsed laser deposition to the inner diameter of tube material traditionally used for ethylene pyrolysis service, (2) determining what microstructural changes the SiC coated Fe-Ni-Cr tubing undergoes during service, and (3) determining what influence changes in microstructure have on the life of the tubing. Since diffusion underlies the self- healing mechanism of coatings as well as the mechanism of coating degradation by interdiffusion with the substrate, knowledge of the diffusion characteristics of the system is of fundamental importance. The program will also establish a foundation for a lifetime of educational excellence through improved pedagogy, curriculum development, outreach, and mentoring. This effort is highlighted by the ASM endorsed Northeast Teachers' Training Camp beginning in 2004 under the PIs direction.