The Thermal Conductivity of 8 Yttria Stabilized Zirconia and Mullite Thermal Barrier Coating on Medium Carbon Steel Substrate

Abstract

Thermal conductivity is one of the main features of a thermal barrier coating (TBC) that is important in making sure that the TBC gives its best functionality to the system. A good TBC has low thermal conductivity, so that the temperature can drop across the coating which allows the system to operate in extremely high temperatures. There are several factors that can influence the thermal conductivity of the TBC such as the type of ceramic material used, the deposition method and the physical features of the TBC itself. For this research, air plasma spray (APS) is used to deposit 8 wt% yttria stabilized zirconia (8YSZ) and mullite on medium carbon steel substrates to study their respective thermal conductivities. The aim here is to develop a heat shield using TBC to protect the electric motor in an electrical turbocompounding system. The characteristics of the deposited TBC such as microstructure, element composition, phases and thermal conductivity are studied. The thermal conductivity is reduced when medium carbon steel substrate deposited with TBC. The thermal conductivity of 8YSZ, mullite and uncoated sample at minute 60 is 0.868 W/mK, 0.903 W/mK and 1.057 W/mK, respectively. Therefore, the deposition of 8YSZ TBC can lower the thermal conductivity of the medium carbon steel heat shield.