A novel low-thermal-conductivity plasma-sprayed thermal barrier coating controlled by large pores

In order to reduce the thermal conductivity of thermal barrier coatings (TBCs) for land-based gas turbine applications, porous TBC (P-TBC) with a microstructure consisting of a distribution of large open pores was developed. A powder mixture of zirconia and polyester was used to form such open pores within the microstructure. The results showed that the thermal conductivity of the P-TBC monotonically decreased as the porosity increased. In addition, compared with conventional TBC with a thermal conductivity value of 1.2 W/(mK), the thermal conductivity of P-TBC with a polyester content 15 wt.% achieved a value as low as 0.3 W/(mK). This implies that the presence of large open pores leads to a dramatic reduction in the thermal conductivity, and the thermal conductivity can be freely controlled by adjusting the polyester content of the powder. A SEM-image-based finite element model was constructed. The FE analysis revealed that the presence of pores disturbed the heat flow. Thus, compared with the relatively straight lines that occurred for the TBC, which possessed few pores, it was considered that the presence of open pores within the P-TBC increased the length of the heat flow lines. This provides an explanation for the reduction in the apparent thermal conductivity of the P-TBC.