Papers by Author: Luc Rémy

Abstract: Thermally grown oxide (TGO) spallation increases the degradation rate of aluminide protective coatings during thermomechanical cycling. Thermal expansion misfit between TGO, bond coat and substrate, applied mechanical load in the system, and local instabilities are known triggers for spallation. Mechanical tests have been performed on coated and oxidised AM1 superalloy. In situ and post mortem study including digital image analysis and SEM were performed in order to characterise strain fields and associated damage field. Good correlation is found between oxide strain and damage extent.

Abstract: The present work, performed on nickel aluminides deposited on a single Ni-based superalloy AM1, focuses on the effect of the following several parameters on the microstructural and chemical changes occurring during isothermal heat treatment at 1100°C for 50h : -oxygen pressure by comparing heat treatment under ambient air (PO2 = 0.2 bar) and under secondary vacuum (PO2 = 0.2x10-6 bar). -cooling rate after isothermal heat treatment by comparing furnace cooling (3°C/min) and water quenching (500°C/min). -Pt addition in the coating by comparing NiAl and NiPtAl coatings. Characterizations were performed using SEM, analytical TEM and electron microprobe analyses. The results show that these parameters have a strong influence on both the microstructural evolution and the oxidation of the thermal barrier coating (TBC) system. Appropriate heat treatments are essential to improve interfacial resistance and increase the durability of TBC systems.