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高的化工产品之一，到2010年，对乙烯的需求将超过1亿吨，因为从乙烯中提取的产品正在取代包装、建筑、汽车和其他应用领域的传统材料。碳氢化合物的高温热解已经实践了半个多世纪，每年仍有超过5亿美元的Fe-Ni-Cr基管状产品被消耗。催化结焦是导致管壁温度升高、传热不良、压降增大、内径减小、管内堵塞的罪魁祸首。在役运行和除焦循环的结合使管道寿命缩短了4-6年。该学院早期职业发展（Career）奖将专注于通过以下方式提高工艺效率：(1)通过脉冲激光沉积在传统用于乙烯热解的管道材料的内径上涂附SiC涂层来限制催化结焦的形成；(2)确定SiC涂层的Fe-Ni-Cr管道在使用过程中经历的微观结构变化；(3)确定微观结构变化对管道寿命的影响。由于扩散是涂层自愈机制以及涂层与基体相互扩散降解机制的基础，因此了解该系统的扩散特性至关重要。该计划还将通过改进教学法、课程开发、推广和指导，为终身的卓越教育奠定基础。2004年，在ppi的指导下，ASM认可的东北教师训练营突出了这一努力。

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.