Self healing behavior of enamel incorporated with nickel particles of various sizes during high temperature oxidation process

The self-healing nickel-enamel composite coating can spontaneously heal cracks at a certain temperature, thus ensuring its high-temperature service ability in thermal shock environment. In this study, nickel particles of various sizes (50 nm, 2 µm and 20 µm) were incorporated into a silicate enamel. Flexural strength of the pure enamel and its composites was investigated to analyze their thermal shock and crack healing behavior. Results indicated that nickel particles incorporation enhanced strength and thermal shock resistance of enamel, but such an enhancement depended on the size of particles. When nickel particles were in a scale of 2 µm, the composite performed the highest flexural strength, 34% higher than the enamel free of nickel particles. Moreover, its critical thermal shock temperature (ΔT_C) was increased by 100 ℃. In the meantime, the composite was endowed with the optimum ability of cracks self-healing. After cracks nucleation in the process of thermal shock, they were largely healed in subsequent oxidation stage. Flexural strength was recovered to 87.9% of the value before thermal shock.