Comparison of tensile properties between NiCoCrAl/YSZ microlaminates and the monolithic NiCoCrAl foil fabricated by EB-PVD

Two NiCoCrAl/YSZ microlaminates and a monolithic NiCoCrAl foil were fabricated by EB-PVD. The two microlaminates contained 20 and 26 alternating layers of NiCoCrAl and YSZ respectively; and their metal layers were 35 and 14 times thicker than their ceramic layers (thickness ≈ 1 μm) respectively. Tensile testing was performed at room temperature, 700 °C and 1000 °C, and fracture surfaces were examined using SEM. The fracture toughness was estimated using measured data in room-temperature tensile testing. Among the three foils, the 14 μm metal-layer microlaminate displayed the greatest ductility of metal layers, tensile strength and elastic modulus; however, the 35 μm metal-layer microlaminate showed the greatest fracture toughness. The ratios of the strength of the microlaminates to that of the monolithic NiCoCrAl foil increased with increasing testing temperature. The result was discussed in terms of metal strengthening mechanism.