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

• 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

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.

与抗氧化性较差的 Nb-Al 和 Nb-Cr 二元合金相比，同时含有铝和铬的溅射沉积 Nb 合金在 1073 K 以上表现出较高的抗氧化性。三元合金的氧化通常遵循抛物线速率定律。物质的扩散传输是速率决定步骤，然而，含有约 40 at% 的三元合金具有高抗氧化性。当三元合金含有约40at时，铌不是由于形成氧化铝垢，而是由于外层氧化铬层和内层由氧化铝、铬-铌和/或铝-铌双氧化物的混合物组成。 %铌在O_2-SO_2气氛中被氧化，铝的优先氧化是由于铝在O_2-SO_2气氛中的瞬时硫化而发生的。然而，优先氧化导致合金内部氧化，而不是形成连续的外部氧化铝氧化皮，通过降低铌含量进一步增加铝含量，最终导致形成高度保护性的α-氧化铝氧化皮。高于 1073 K。将这种富铝铌合金涂层到高温下具有高机械性能的铌基合金可能会引起涂层和基材之间的相互扩散，从而导致作者成功证明，在涂层和基体之间引入阳极氧化铝层作为扩散阻挡层，可以有效抑制相互扩散，从而在高温下保持涂层的高抗氧化性。