No abstract

A new concept of composite phase ceramic had been proposed for the topcoat of a durable thermal barrier coating (TBC) system which is one of the critical technologies for advanced turbine engines. The composite phase TBCs showed promising performance related benefits over conventional single phase TBCs, including durability, material affordability, thermal stability and low thermal conductivity. The present work is to continue the effort to exploring the TBC behaviors of erosive wear by solid particle erosion test and thermal cyclic shock by special burner rig test. In the erosion test, the investigation was focused on the most important characteristics of erosion test results using different characterization methods, including the variations of erosion damages with impingement angle and finally the effect of high temperature sintering. In the burner rig test, the TBC was exposed to a rapidly thermal cycling condition introduced by a high heat flux and high-velocity combustion torch. The TBC damages and failure modes were identified and explained in terms of microstructural observation and mechanism discussion. The composite phase c ? t 0 TBC demonstrated improved erosion resistance relative to a Gd 2 Zr 2 O 7 TBC and equivalent thermal shock resistance to a conventional 8YSZ TBC. Keywords air plasma spray Á burner rig test Á coating characterization Á erosion test Á thermal barrier coating This article is an invited paper selected from abstracts submitted for the 2020 International Thermal Spray Conference, ITSC2020 that was to be held from June 10-12, 2020, in Vienna, Austria. The conference was cancelled due to the coronavirus (COVID-19) pandemic. The paper has been expanded from the planned presentation.

In this paper, a novel concept in the field of phase composite ceramics has been proposed and applied for creating the topcoats of durable thermal barrier coatings (TBCs), which is one of the most critical technologies for advanced high-efficiency gas turbine engines in extreme environments. The phase composite ceramic TBCs were designed to demonstrate superior and comprehensive performance-related merits, benefits, and advantages over conventional single-phase TBCs with a topcoat of 8YSZ or Gd2Zr2O7, including thermal phase stability, thermal shock durability, low thermal conductivity, and solid particle erosion resistance. In this paper, we review and summarize the development work conducted so far related to the phase composite ceramic concept, coatings processing, and experimental investigation into TBC behaviors at elevated temperatures (typically, ≥1250 °C) using different evaluation and characterization methods, including isothermal sintering, a burner rig test, a solid particle-impinging erosion test, and a CMAS corrosion test. Two-phase (t’+c) zirconia-based TBCs demonstrated improved thermal shock and erosion resistance in comparison to conventional single-phase (t’), 8YSZ TBC, and Gd2Zr2O7 TBC, when used separately. Additionally, a triple-phase (t’+c+YAG) TBC sample demonstrated superior CMAS resistance. The TBC’s damage modes and failure mechanisms for thermal phase stability, thermal cycling resistance, solid particle erosion behavior, and CMAS infiltration are also characterized and discussed in detail, in terms of microstructural characterization and performance evaluation.