Development of a Laser Heating Method for Evaluating Thermal Shock/Fatigue Resistance of Ceramic Thermal Barrier Coating for Gas Turbine Blade

Toshiyuki Hashida, Tsuyoshi Ishikawa, Tsutomu Tobe, Hideaki Takahashi

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

In this paper, an attempt to develop a thermal shock and fatigue test of ceramic thermal barrier coating (TBC) for gas turbine blades is presented, using a laser heating technique. This method uses a cylindrical specimen which simulates the curvature of the leading edge of a gas turbine blade. A plasma-sprayed ZrO2-Y2O3/NiCrAlY TBC system was tested. The cylindrical specimens used consisted of ZrO2-8wt%Y2O3 thermal barrier layers (0.35 mm thick) deposited on a stainless steel substrate, with a NiCrAlY bond coat (0.15 mm thick). A CO2 laser (maximum output = 50 W) was used for the thermal shock and fatigue tests, where a laser beam with a diameter of 4 mm was irradiated onto the coating surfaces. The specimen inner surfaces were air-cooled or water-cooled to achieve various temperature drops within the ZrO2 coating. Concurrently, laser experiments on coating surface temperature (Ts) and back-surface temperature (Tb) were measured, and acoustic emission (AE) monitoring was carried out to detect the onset of the coating damage. Using the experimental results, a thermal shock fracture mechanism map was constructed for the ZrO2 TBC as a Ts - Tbdiagram. The Ts - Tb diagram indicated that the most probable damage of the TBC system under the advanced gas turbine environments was delamination growth at the ZrO2/NiCrAlY interface which leads to the spalling of the ZrO2 layer. In order to improve the thermal shock/fatigue resistance of the ZrO2 coating, vertical cracks were induced within the ZrO2 coating by laser heating, and the effect of the laser heat processing on the thermal resistance was examined. It is demonstrated that the thermal resistance of the TBC is significantly enhanced by the laser precrack processing.

Original languageEnglish
Pages (from-to)15-19
Number of pages5
JournalTransactions of the Japan Society of Mechanical Engineers Series A
Volume58
Issue number545
DOIs
Publication statusPublished - 1992
Externally publishedYes

Keywords

  • Ceramic Thermal Barrier Coating
  • Delamination
  • Gas Turbine
  • Laser Heating
  • Material Testing
  • Spalling
  • Thermal Fatigue
  • Thermal Shock
  • Vertical Crack
  • Zirconia

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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