Abstract
Abstract In this study, Fe-based nanocrystalline coatings were obtained by crystallization of amorphous coatings through heat treatment with different annealing time of 0.5 h, 5 h, 10 h and 100 h, respectively. Cyclic oxidation behaviours of the Fe-based amorphous coating as well as these annealed ones at 750 °C in still air were investigated and compared. The results showed that the grain size of the annealed Fe-based coatings was significantly increased as the pre-annealing time prolonged. However, the cyclic oxidation kinetic curves indicated that the cyclic oxidation resistance of the annealed Fe-based coatings was unexpectedly improved as the increase in grain size. The coating, which was annealed at 700 °C for 100 h, exhibited the lowest accumulated weight gain of 2.8 mg/cm2 and parabolic rate constant kp values of 1.7 × 10− 11 g2 cm− 4 s− 1, indicating the highest oxidation resistance. The enhanced oxidation resistance of the annealed coatings was mainly attributed to the elimination of cracks, pores and splat boundaries caused by the intersplat sintering during heat treatment. Cracks and splat boundaries were the primary diffusion paths for the oxygen, resulted in the different diffusion models of oxygen or metal atoms in Fe-based nanocrystalline coatings.
Published Version
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