Next Generation Heat-Resistant Cast Ni-Cr Alloy with Improved Carburization Control

KUBOTA材料加拿大公司和麦克马斯特大学之间的合作伙伴关系的总体目标是：(i)开发下一代耐热铸造UCX （48Ni-41Cr）合金，具有更好的抗渗碳能力，作为通过蒸汽裂解生产乙烯的辐射炉盘管；（ii）为博士级HQP提供体验式培训机会，开发先进材料，提高恶劣环境下的性能。通过蒸汽裂解提高辐射炉盘管在乙烯生产中的渗碳控制的好处包括：(i)减少了能源使用，（ii）减少了二氧化碳的产生，（iii）延长了管的使用寿命（高达50%）。提出的新方向包括通过添加大阳离子直径的活性稀土元素（Ce和/或La）来开发下一代UCX合金，同时与Si“脱合金”，从而改善铬垢保护（更好的附着力和减少内部氧化/渗碳）。添加大阳离子直径的活性元素的两个关键好处包括(i)增强Cr的选择性氧化和（ii）改善与衬底的附着力。在Ni-25Cr合金中，添加活性元素可以改善铬垢保护，但对于Cr含量较高的铸造合金（如UCX）则没有效果。

The overarching goals of the partnership between KUBOTA Materials Canada Corporation and McMaster University are to: (i) develop the next generation heat-resistant cast UCX (48Ni-41Cr) alloy with improved carburization resistance as radiant furnace coil tubes for ethylene production via steam cracking, and (ii) provide experiential training opportunity for a PhD-level HQP with the development of advanced materials with improved performance for harsh environments. Benefits from improved control of carburization of radiant furnace coil tubes in ethylene production via steam cracking include: (i) reduced energy use, (ii) reduced CO2 production and (iii) extended tube lifetime (by up to 50%). The new direction proposed involves developing the next generation UCX alloy by adding large cation diameter reactive rare earth elements (Ce and/or La), whilst simultaneously "dealloying" with Si, with improved chromia scale protection (better adhesion and reduced internal oxidation/carburization). Two key benefits of large cation diameter reactive element addition include (i) enhanced selective oxidation of Cr and (ii) improved adhesion with the substrate. Chromia scale protection improvements associated with reactive element additions have been demonstrated for Ni-25Cr alloys, but not for cast alloys, with higher Cr contents, such as UCX.