Evaluation of Fracture Mechanics in Ceramics Splay-Coated Materials by Using Fast 3-D Digital Image Correlation Method

采用低压等离子喷涂(LPPS)技术制备了耐高温腐蚀和氧化的CoNiCrAlY合金涂层。然而，对燃气轮机叶片寿命有重要影响的LPPS CoNiCrAlY涂层的力学性能尚不清楚。本文研究了CoNiCrAlY涂层在单轴压缩载荷下的单调和循环变形行为。涂层样品的制备不依赖于基材，只需用硝酸溶解基材，即可制得与基材无关的涂层样品。涂层厚度为30 0μm，用激光散斑应变/位移仪测量了涂层的应力应变响应。涂层具有较低的弹性模数，表现出非线性的应力应变响应。结果表明，在压缩载荷作用下，涂层会产生永久应变；压缩载荷作用下，涂层会发生硬化。在循环压缩载荷作用下，产生的应变进一步减小。孔隙率高的涂层具有大应变、大永久应变和低杨氏模量的特点。

Low pressure plasma spraying (LPPS) is used to prepare CoNiCrAlY alloy coatings for insulation from the high temperature corrosion and oxidation. However, mechanical properties of LPPS CoNiCrAlY coatings, which have important effects on the life of a gas turbine blade, have not been clarified. In this study, monotonic and cyclic deformation behaviors of the CoNiCrAlY coatings under uniaxial compressive loading were examined. Coating specimens independent of substrates were fabricated by dissolving out the substrates only at the region of gauge area by nitric acid. The thickness of the coatings were 300μm. The stress-strain response was measured using the laser speckle strain / displacement gauge (SSDG). The coating showed the nonlinear stress-strain response with a considerably low elastic modules. It was found that the coating left permanent strain by compressive loading: the coating was hardened by compressive loading. The generated strain was also found to decrease furthermore by undergoing cyclic compressive load. The coatings with high porosity showed that the large strain, large permanent strain and low Young's modulus.