Effect of Bond Coat Processes and Surface Characteristics On the Failure Mechanism of Thermal Barrier Coatings

摘要

This paper explores the effect of bond coat processes and surface characteristics on the failure mechanism of thermal barrier coatings (TBC's). TBC's consist of a 300μm thick air plasma sprayed (APS) top coating of ZrO-2-8Y_2O_3w% and CoNiCrAlY bond coats which were deposited using low pressure plasma spray (LPPS~R), shrouded air plasma spray (SPAS) and high velocity oxy-fuel (HVOF) combustion spray and different size powder. Bond coat surface profiles were measured by profilometric techniques and surface roughness was calculated according to the measured results. TBC performance and failure mechanisms were evaluated by adhesive bond strength testing, image analysis measurements of porosity, thermal cycling testing, X-ray diffraction and microstructural analyses. Research results show that bond coat deposition processes and surface characteristics had significant effects on the thermal cycling lifetime and failure mechanism.