"Effects of Nano Si3N4 and Plasma Treatment on Thermal Shock Behavior of Plasma Sprayed Al2O3-YSZ Coatings"

Al₂O₃-YSZ coatings were prepared on 304 stainless steel by air plasma spraying. Nano Si₃N₄ was added during feedstock preparation process. The feedstocks with and without nano Si₃N₄ were treated by plasma flame. The effects of nano Si₃N₄ and plasma treatment on thermal shock behavior of the coatings at 800℃ and 1000℃ were studied. Scanning electron microscope and X-ray diffractometer were used to study the morphologies and phases of the coatings before and after thermal shock tests. The experimental results show that plasma treatment improves the thermal shock resistance of the coating with nano Si₃N₄. The thermal shock cycles of the coating with nano Si₃N₄ accompanied by plasma treatment increase 0.7 times and 1.1 times compared with those of the coating without nano Si₃N₄ and plasma treatment. During the thermal shock process, the α-Al₂O₃ in the coatings transforms into γ-Al₂O₃. Obvious wide cracks formed in the coatings when thermal shock tests were carried out at 1000℃, the thermal shock cycles of which decrease apparently.