Tabbin Institute for Metallurgical Studies, Cairo, Egypt.
Faculty of Science, Menofia University, Shebeen El-Koom, Egypt.
Sci Rep. 2023 Jul 12;13(1):11249. doi: 10.1038/s41598-023-38216-4.
Protective oxide layers on Ti-6Al-3Mo-2Nb-2Sn-2Zr-1.5Cr (TC21) alloy with equiaxed microstructure considerably influence micro-hardness and hot corrosion resistance. The present work's thermal oxidation of TC21 alloy was performed at 600, 700, and 800 °C for 5, 20, and 50 h durations. Hot corrosion methods in NaCl and NaCl + NaSO salt media were applied to raw (unoxidized) and oxidized samples at 600 and 800 °C for 50 h. Hot corrosion was conducted at 600 °C for 5 cycles with 10-h steps. The best oxide layer thickness was observed at 800 °C, which increased with increased oxidation time and temperature. The surface hardness of the oxide layer at 800 °C was 900 ± 60 HV owing to the formation of TiO and AlO phases. Raw material hardness was 342 ± 20 HV, increasing threefold due to thermal oxidation. In the case of NaCl, weight loss dominated all samples except at 800 °C for 5 h. In the case of NaCl + NaSO, weight gain occurred at 600 and 800 °C for 5 h. Weight loss occurred for the raw samples and those processed at 800 °C for 20 and 50 h, where the oxide layer flaked off. Surface hardness increased upon hot corrosion testing because of the formation of brittle phases, such as TiO and NaTiO. Samples that oxidized at 800 °C for 5 h had the highest hardness and corrosion resistance.
具有等轴微观结构的 Ti-6Al-3Mo-2Nb-2Sn-2Zr-1.5Cr（TC21）合金表面的保护性氧化层对其显微硬度和抗热腐蚀性有很大影响。本研究对 TC21 合金在 600、700 和 800°C 下进行了 5、20 和 50 h 的热氧化处理。在 600 和 800°C 下，在 NaCl 和 NaCl+NaSO 盐介质中对原始（未氧化）和氧化样品进行了 50 h 的热腐蚀试验。热腐蚀在 600°C 下进行了 5 个循环，每个循环 10 h。在 800°C 下观察到最佳的氧化层厚度，其随着氧化时间和温度的增加而增加。由于 TiO 和 AlO 相的形成，在 800°C 下氧化层的表面硬度为 900±60 HV。原始材料的硬度为 342±20 HV，经过热氧化处理后增加了三倍。在 NaCl 的情况下，除了在 800°C 下氧化 5 h 的情况外，所有样品都以重量损失为主。在 NaCl+NaSO 的情况下，在 600 和 800°C 下氧化 5 h 会发生增重。原始样品和在 800°C 下氧化 20 和 50 h 的样品发生了重量损失，氧化层剥落。在热腐蚀试验中，由于形成了 TiO 和 NaTiO 等脆性相，表面硬度增加。在 800°C 下氧化 5 h 的样品具有最高的硬度和耐腐蚀性。
