Yttria partially stabilized zirconia (YSZ)

a component of thermal barrier coatings

is widely used in complex high temperature conditions. The excellent thermal durability is attributed to non-transformable tetragonal phase (t′). Currently

it is uncertain for the maximum working temperature of t′ phase

and the mainstream view is still around 1200 ℃. Based on this

using atmospheric plasma spray (APS) process

YSZ coatings were fabricated followed by various thermal aging treatment. Evolution of microstructure

phase composition

sintering shrinkage and fracture toughness were investigated. The results show that the coating tested in 24 h@1400 ℃ still maintains m phase free even after 7–year room temperature storage; samples heat treated at 300 h@1400 ℃ and 300 h@1600 ℃ no broken

with m phase volume content of 3.55% and 35.41%

respectively. The average linear shrinkage of 300 h@1600 ℃ heat treated coatings is 0.4%. Grain growth and pore healing occurred during thermal aging treatment

bringing the increase of the bending strength and fracture toughness of coatings. Therefore

APS YSZ coatings can be used at 1400 ℃ for long time (~300 h) service.