Novel Fe-Based Amorphous Composite Coating with a Unique Interfacial Layer Improving Thermal Barrier Application.

To improve thermal barrier applications in advanced vehicle engines, a novel Fe-based amorphous composite coating was designed by introducing ceramic oxides and was prepared by atmospheric plasma spraying (APS). The microstructure and related properties of the as-deposited coating were investigated in detail. The composite coating comprises a well-formed FeCrNbBSi amorphous metallic matrix and dispersed yttria-stabilized zirconia (YSZ) splats. A unique Si-oxide interfacial layer with a thickness of several nanometers and an amorphous structure forms between the metallic matrix and ceramic phase, which is attributed to a combination of multiple effects. The composite coating displays extremely low thermal conductivity from 2.28 W/mK at 100 °C to 3.36 W/mK at 600 °C and can increase the surface temperature of the piston crown by 18.93 °C, which implies a significant means of enhancing the power efficiency. The improved thermal barrier ability of the composite coating is revealed as the crucial effect of the Si-oxide interfacial layer, which induces an increased interfacial thermal resistance. The fracture toughness of the composite coating remains at 3.40 MPa·m, comparable to that of the monolithic amorphous coating, 3.74 MPa·m, which is closely related to the formation of a Si-oxide layer and its nanoscale thickness. Therefore, the Fe-based amorphous composite coating developed here demonstrates great potential as an innovative metal-based thermal barrier coating for application in vehicle engines and provides specific inspiration for future works exploring the interfacial engineering of coating.