Isothermal and cyclic oxidation resistance of boron-modified and germanium-doped silicide coatings for titanium alloys
Isothermal and cyclic oxidation resistance of boron-modified and germanium-doped silicide coatings for titanium alloys
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DOI：
10.1007/bf01046846
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发表时间：
1996-06
影响因子：
2.2
通讯作者：
B. Cockeram;R. Rapp
中科院分区：
文献类型：
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作者：
B. Cockeram;R. Rapp
由于尚未开发出机械性能和高温抗氧化性充分平衡的钛合金，因此需要保护涂层。在我们之前的论文中，描述了通过卤化物激活的包渗方法在CP Ti、Ti− 24 Al − 11 Nb、Ti− 22 Al − 27 Nb和Ti− 20 Al − 22 Nb上生长的B改性和Ge掺杂的硅化物扩散涂层。在这项研究中，等温和循环氧化被用来评估这些涂层的氧化性能相比，未涂覆的基板。在高温下的等温氧化的速率控制机制是固态扩散通过SiO2规模，而低温氧化的机制涉及晶界扩散通过TiO 2。B-改性和Ge-掺杂的硅化物涂层的等温和循环氧化速率比纯TiSi 2慢得多。对于Ti−Al−Nb合金，在500-1000°C下，或对于CP Ti，在500-875°C下，在200次氧化循环后，通过显微硬度测量，在涂层基材中未检测到氧污染。讨论了最佳涂层组成的优异抗氧化性能。
Since titanium alloys with an adequate balance of mechanical properties and high-temperature oxidation resistance have not been developed, protective coatings are required. In our previous paper, B-modified and Ge-doped silicide diffusion coatings grown on CP Ti, Ti−24Al−11Nb, Ti−22Al−27Nb, and Ti−20Al−22Nb by the halide-activated, pack-cementation method were described. In this study, isothermal and cyclic oxidation were used to evaluate the oxidation performance of these coatings in comparison to uncoated substrates. The rate-controlling mechanism for isothermal oxidation at high temperature was solid-state diffusion through a SiO2scale, while the mechanism for low-temperature oxidation involved grain-boundary diffusion through TiO2. Both isothermal and cyclic oxidation rates for the B-modified and Ge-doped silicide coatings were much slower than for pure TiSi2. Oxygen contamination was not detected by microhardness measurements in the coated substrates after 200 oxidation cycles at 500–1000°C for the Ti−Al−Nb alloys, or at 500–875°C for CP Ti. The excellent oxidation resistance for the optimum coating compositions is discussed.