环境障涂层含钙镁水汽条件下热冲击行为

Thermal Shock Behavior of Environment Barrier Coatings in a Calcium/Magnesium-Included Water Vapour Condition

环境障涂层(EBC)在实际服役过程中不仅面临高温水汽环境,还会面临钙镁的腐蚀。对等离子喷涂的双硅酸镱EBC涂层进行了1 250℃、300次的含钙镁水汽热冲击考核试验,并进行了涂层微观组织分析。结果表明,考核后涂层表面生成了双层腐蚀结构,其中最外层主要受到了钙腐蚀,生成了明显的多相组织,且包含大孔洞等形貌,该区生成了(Yb/Ca)_(2)Si_(2)O_(7)、(Yb/Ca)_(2)SiO_(5)和(Ca/Yb)_(2)SiO_(4)多相组织;次表层则受到了以镁为主的钙镁离子共同腐蚀,也生成了多晶相(Yb/Mg/Ca)_(2)SiO_(5)和(Mg/Ca/Yb)_(2)SiO_(4),组织相对致密。通过结合表面形貌、横截面组织、微观能谱成分和XRD相结构等分析方式,对EBC涂层在含钙镁水汽热冲击环境下的化学反应机制进行了分析,给出了涂层失效机理分析。

Environment Barrier Coatings(EBCs) working in real service process meet not only environment of high-temperature water vapour, but also face of calcium and magnesium corrosion.In this paper, EBCs made by plasma spray with Yb_(2)Si_(2)O_(7) coatings were tested by thermal shock in a calcium/magnesium-included water vapour environment at 1 250℃ for 300 cycles.The results showed that there formed two-layer corrosion structures at the coating surface.The topmost layer sustained calcium corrosion, forming obvious multi-phase structure with large pores with phases of(Yb/Ca)_(2)Si_(2)O_(7),(Yb/Ca)_(2)SiO_(5)and(Ca/Yb)_(2)SiO_(4).The subsurface layer sustained both calcium and magnesium corrosion but mainly the magnesium corrosion, also forming multi phases(Yb/Mg/Ca)_(2)SiO_(5) and (Mg/Ca/Yb)_(2)SiO_(4) with relatively dense structure.Via analyses on surface morphology, cross section microstructure, micro-EDS composition and XRD phase structures, the chemical reaction mechanism of the EBC coatings was studied under the calcium/magnesium-included water-vapour thermal shock environment, and the failure mechanism of the coating was provided.