Investigation of Sintering Mechanism for Novel-Structured Thermal Barrier Coatings with Embedded Micro-Agglomerated Particles

Abstract

A micro-agglomerated particle embedded thermal barrier coatings (TBCs) structure was prepared by an improved plasma spray process to withstand sintering-induced degradation of TBCs during service. In this study, the sintering resistance, thermophysical and mechanical properties of conventional and novel structured TBCs were systematically characterized. The results suggested that the thermal conductivity and sintering shrinkage of the novel-structured TBCs were approximately 30% lower than those of conventional APS TBCs. The elastic modulus of the novel-structured coating is only 32% of that of the conventional structure after thermal exposure at 1300 °C for 100h. The distinct structure of the coating is the main factor that influences its performance. The relationship between the structural evolution and residual strain of the coating was analysed using electron backscatter diffraction and transmission electron microscopy. Significant differences were observed in the sintering behaviour of the dense matrix and embedded particle regions in the coating. Some columnar grains near the intersplat pores in the dense matrix have similar lattice orientations, and they tend to connect and consequently heal the intersplat pores. The large pores between the agglomerated particles and non-oriented submicron-sized grains that constitute these particles are responsible for the sintering resistance of the coating.

Keywords: Thermal Barrier coating, Sintering mechanism, Structure design, Electron backscatter diffraction