Effect of laser glazing on the thermo-mechanical properties of plasma-sprayed LaTi₂Al₉O₁₉ thermal barrier coatings

ABSTRACT

Conventional duplex (DL) and functionally graded (FG) LaTi₂Al₉O₁₉ (LTA) coatings were deposited over C263 nickel alloy by air plasma spray (APS) and compared with subsequent laser glazing processes. The effect of laser glazing on adhesion strength and thermal barrier performance was investigated. The thermal barrier effect was measured using the temperature difference technique involving infrared (IR) rapid heater and the adhesion strength was measured using the scratch tester. The surface morphology and microstructure were analyzed by optical microscopy (OM), Scanning Electron Microscope (SEM) and 3D profilometer. Based on the experimental results, the laser glazing showed a remarkable temperature drop after IR rapid heating. The changes in porosity and grain refinement make more contributions to the temperature drop of the laser-glazed coatings than that of as-sprayed coatings. The temperature drop is about 110°C for laser-glazed LTA FG coating after 100 s of IR flash, while the drop in DL as-sprayed coating is 60°C compared to the base material.

KEYWORDS:

• Functionally graded
• IR rapid heating
• laser glazing
• LaTi₂Al₉O₁₉
• plasma spray
• scratch
• thermal barrier coating
• thermal drop