基于声发射技术的Si-Cr-Ti高温抗氧化涂层弯曲失效机理研究

本研究借助声发射技术对铌基高温抗氧化涂层在常温下的弯曲失效过程进行了研究。利用k均值聚类方法对信号进行了分类,结合截面扫描电镜观测结果确定高温抗氧化涂层在弯曲载荷下的信号分别对应基体变形、表面垂直裂纹、滑动型界面裂纹和张开型界面裂纹,通过快速傅里叶变换得到了各类信号的主频分别为100、310、590和450 kHz,借助小波分析得到了各信号的小波能量系数。涂层弯曲失效过程主要包括四个阶段,分别为受拉侧表面垂直裂纹萌生的初始损伤阶段、表面垂直裂纹增殖阶段、两侧界面裂纹快速扩展的损伤积累阶段和受压侧涂层明显剥落的宏观剥落阶段。

Bending Failure Mechanism Study of Si-Cr-Ti High Temperature Oxidation Resistance Coating via Acoustic Emission Technique

In this study, the bending failure process of niobium-based high-temperature oxidation resistance coatings at room temperature was investigated by the acoustic emission technique. The signals were classified by the k-mean clustering method. Based on the cross-sectional scanning electron microscopy observation results, the signals of the coatings under bending load were classfied to substrate deformation, surface vertical cracks, sliding interface cracks, and opening interface cracks. The frequency ranges of various types of signals and the wavelet energy coefficients were obtained by fast Fourier transform and wavelet analysis. The acoustic emission signal frequencies of substrate deformation, surface vertical crack, sliding interface crack, and opening interface crack are 100, 310, 590, and 450 kHz, respectively. The coating bending failure process mainly includes four stages, which are 1) the initial damage stage where vertical cracks sprout on the surface of the tensioned side, 2) the surface vertical crack proliferation stage, 3) the damage accumulation stage where the interface cracks on both sides expand rapidly, and 4) the macroscopic spalling stage where the coating on the stressed side is found to spall significantly.