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Tailoring of Oxidation-Resistant Nb-base Alloys at Ultra-High Temperatures and Understanding of their Oxidation Mechanism

超高温抗氧化铌基合金的定制及其氧化机制的理解

基本信息

批准号：
13650770
负责人：
HABAZAKI Hiroki
金额：
$ 0.45万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650770/
关键词：
High temperature oxidation Nb-Al-Cr alloys Sputter deposition Oxidation-resistant coating Alumina scale High temperature materials SO_2 Sulfidation スパッタ蒸着耐酸化性コーティングアルミナスケール SO_2 硫化

项目摘要

Sputter-deposited Nb alloys containing both aluminum and chromium reveal high oxidation resistance above 1073 K, in contrast to less oxidation-resistant Nb-Al and Nb-Cr binary alloys. The oxidation of the ternary alloys generally follows the parabolic rate law, indicating that diffusional transport of matter is the rate-determining step. However, the high oxidation resistance of the ternary alloys containing about 40 at% niobium is not due to the formation of an alumina scale, but due to an outer chromia layer with the inner layer consisting of a mixture of alumina, chromium-niobium and/or aluminum-niobium double oxides. When the ternary alloys containing about 40 at% niobium were oxidized in O_2-SO_2 atmospheres, preferential oxidation of aluminum occurs as a consequence of a transient sulfidation of aluminum at the alloy/scale interface. However, the preferential oxidation results in internal oxidation of the alloys, not in the formation of continuous external alumina scale. Further increase in aluminum content by reducing niobium content, finally results in the formation of highly protective α-alumina scales above 1073 K. Coating of this aluminum-rich niobium alloy to niobium-base alloys with high mechanical properties at high temperatures may induce interdiffusion between the coating and substrate, leading to degradation of the oxidation resistance. The authors have successfully demonstrated that introduction of an anodic alumina layer between the coating and substrate as a diffusion barrier layer suppresses effectively the interdiffusion, thus high oxidation resistance of the coating is sustained at high temperatures.

溅射沉积的Nb合金含有铝和铬显示高的抗氧化性高于1073 K，在抗氧化性较低的Nb-Al和Nb-Cr二元合金。三元合金的氧化一般遵循抛物线速率定律，表明物质的扩散输运是速率决定步骤。然而，含有约40原子%铌的三元合金的高抗氧化性不是由于氧化铝氧化皮的形成，而是由于具有由氧化铝、铬-铌和/或铝-铌双氧化物的混合物组成的内层的外氧化铬层。当含40at%铌的三元合金在O_2-SO_2气氛中氧化时，由于铝在合金/氧化膜界面的瞬时硫化，铝发生优先氧化。然而，优先氧化导致合金的内氧化，而不是形成连续的外部氧化铝膜。通过降低铌含量进一步提高铝含量，最终导致在1073 K以上形成高度保护性的α-氧化铝膜。将这种富铝铌合金涂覆到在高温下具有高机械性能的铌基合金上可能会引起涂层和基材之间的相互扩散，导致抗氧化性的劣化。作者已经成功地证明了在涂层和基体之间引入阳极氧化铝层作为扩散阻挡层有效地抑制了相互扩散，从而使涂层在高温下保持高的抗氧化性。