High temperature oxidation and hot corrosion behaviors of PEO and PEO/polysilazane preceramic-based dual-layer coatings on Ti6Al4V alloy
Shuqi Wang, Yaming Wang, Gui Cao, Cuoliang Chen, Yixing Zhu, Maria Serdechnova, Carsten Blawert, Mikhail L. Zheludkevich, Yongchun Zou, Jia‐Hu Ouyang, Dechang Jia, Yu Zhou
Abstract
The high temperature oxidation and corrosion behaviors of a plasma electrolytic oxidation (PEO) coating and a PEO/polysilazane (PEO/PSZ) dual-layer coating are investigated. After exposure in NaCl+Na 2 SO 4 salt at 600 ℃ for 240 h, PEO coating tends to generate porous and loose scales, causing cracking or even complete peeling off from the substrate, and corrosion scales follow the law of formation-shedding-reformulation. After exposure in NaCl+Na 2 SO 4 salt at 600 ℃ for 480 h, the PEO/PSZ coating exhibits a three-layer structure including the outermost corroded layer with sandwich structures, uncorroded Al 2 O 3 particles-containing interlayer, and PEO bottom layer, which retards the continuous penetration of corrosive media and further diffusion of oxygen to the inner bulk alloy , resulting in a remarkable reduction of oxidation and corrosion rate .