An approach to control the interlamellar bonding of plasma-sprayed y ₂O₃-ZrO₂ coatings through deposition temperature

The ceramic coatings plasma-sprayed by the conventional route exhibit a lamellar structure with a maximum interlamellar mean bonding ratio of about 32%. The limited interlamellar bonding dominates the properties of coatings including electrical conductivity, thermal conductivity and mechanical properties. Consequently, the controllable span of the coating performance is limited. Based on the understanding of dominant factor controlling lamellar bonding formation, the coating surface temperature as a key parameter is introduced for extending the mean bonding ratio. For the proof of the concept, 8YSZ (SmOlY₂O₃-ZrO₂) coatings were deposited under different substrate surface temperatures (deposition temperatures) from room temperature up to 1100°C during spraying process. The lamellar mean bonding ratio was estimated from the ionic conductivity of YSZ coatings. It was found that with the increase of deposition temperature, the bonding ratio of YSZ coatings increases from about 32% for the deposits prepared at room temperature to over 75.2% for the deposits prepared at 1100°C. The results clearly revealed that through controlling of the deposition temperature the adjustable extent of the lamellar interface bonding and subsequently the coating properties can significantly extended to fulfill different application requirements for thermal spray coatings.