TiAl合金表面Al-Y渗层的抗热腐蚀性能  

Microstructure and hot corrosion properties of an Al-Y coating on TiAl alloy

作　　者：李涌泉 郝清锐 梁国栋 刘广君 刘树静 LI Yong-quan;HAO Qing-rui;LIANG Guo-dong;LIU Guang-jun;LIU Shu-jing(College of Mechatronic Engineering,North Minzu University,Yinchuan 750021,China;School of Materials Science&Engineering,North Minzu University,Yinchuan 750021,China)

机构地区：[1]College of Mechatronic Engineering,North Minzu University,Yinchuan 750021,China [2]School of Materials Science&Engineering,North Minzu University,Yinchuan 750021,China

出　　处：《Journal of Central South University》2024年第2期330-345,共16页中南大学学报（英文版）

基　　金：Projects(52161009,51961003)supported by the National Natural Science Foundation of China;Project(2022AAC03224)supported by the Natural Science Foundation of Ningxia,China;Project(XAB2022YW07)supported by the West Light Foundation of the Chinese Academy of Science。

摘　　要：针对TiAl合金抗热腐蚀性能不足的问题,采用扩散渗法在其表面制备了Al-Y渗层,研究了催化剂类型对渗层组织结构的影响,分析了渗层的热冲击性能,对比研究了TiAl基体和Al-Y渗层在25%NaCl+75%Na2SO4熔盐(质量分数wt.%)中的热腐蚀行为。结果表明:用不同催化剂制备的Al-Y渗层具有相似的结构,与基体均为良好的冶金结合,由外向内均由富Al外层、TiAl_(3)中间层和TiAl_(2)内层构成,但当采用NH_(4)Cl为催化剂时,渗层的致密度和均匀性较用NaF和AlCl_(3)∙6H_(2)O催化剂好。在1000℃热冲击下,Al-Y渗层较基体合金具有更强的抗热冲击性能。TiAl合金在热腐蚀时,基体中的片层状α_(2)-Ti_(3)Al相首先与O、S介质发生选择性腐蚀,随后形成灾难性腐蚀;而Al-Y涂层在热腐蚀初期会形成致密的Al_(2)O_(3)氧化膜,有效地保护了渗层,随着热腐蚀时间的延长,由于渗层内原子的内外扩散和腐蚀应力,渗层逐渐开裂,裂纹成为O和S元素的扩散通道,但在此过程中,渗层中的TiAl_(3)相发生分解,为裂纹部位提供Al源并形成Al_(2)O_(3)来填补裂纹,延缓了O和S原子的内扩散速率,增强了TiAl合金的耐热腐蚀性能。To improve the hot corrosion performance of TiAl alloys,an Al-Y coating was prepared by a pack cementation process.The effect of catalysts on the structure of the Al-Y coating and its thermal shock resistance was studied.The thermal corrosion performance of both the TiAl alloy and the coating in a mixed molten salt system of 25%NaCl+75%Na2SO4(wt.%)was comparatively investigated.The results showed that the Al-Y coatings prepared with different catalysts had similar structures and good metallurgical bonding with the substrate,which was mainly composed of an Al-rich outer layer,a TiAl_(3)middle layer,and a TiAl_(2)inner layer.However,the coating prepared using NH_(4)Cl as the catalyst was more uniform and denser than those formed using NaF and AlCl_(3)·6H_(2)O.The Al-Y coating improved the thermal shock resistance of the TiAl alloy under thermal shock at 1273 K.Hot corrosion tests showed that the lamellarα_(2)-Ti3Al phase in the TiAl alloy first underwent selective corrosion by O and S atoms in the medium,followed by catastrophic corrosion.Moreover,the Al-Y coating formed a dense Al_(2)O_(3)film in the early stage of hot corrosion,which effectively protected the permeable layer.Upon extending the hot corrosion time,the coating gradually cracks due to the internal and external diffusion of atoms and corrosion stress.The formed cracks served as diffusion channels for S and O atoms,and the TiAl_(3)phase in the coating continued to decompose,providing more Al atoms to the cracks.This eventually formed a dense layer of Al_(2)O_(3)to compensate for the cracks,delaying the internal diffusion rate of S and O atoms,and significantly improving the thermal corrosion resistance of the TiAl alloy.

关 键 词：TIAL合金 Al-Y渗层 组织结构 热冲击 热腐蚀 

分 类 号：TG174.4[金属学及工艺—金属表面处理]