SOME ASPECTS OF PROPERTIES DESIGN OF PLASMA-SPRAYED THERMAL BARRIER COATINGS

The properties of zirconia-based thermal barriers produced by thermal spraying substantially differ from those manufactured by sintering. Barriers deposited by spraying are characterized by high porosity, micro and macro cracks and very fine voids formed by incomplete particle contact during coating build-up. In consequence, their thermal conductivity is much lower than that of bulk material. Heating at an elevated temperature of plasma-sprayed coatings produces an increase in thermal conductivity due to sintering of micro cracks and fine voids between particles. The thermal conductivity of plasma-sprayed coatings is a function of porosity, too. When designing plasma-sprayed thermal barrier coatings the increase of thermal conductivity under working conditions and the influence of porosity should be taken into account.