Thermal analyses and weight gain modeling study on Ti–Al – based intermetallic coated Ti6Al4V alloy

Abstract

Ti6Al4V alloy is a commonly used α + β alloy among titanium alloys. In this study, in order to improve the oxidation resistance of the Ti6Al4V alloy, Ti–Al – based aluminum coating was deposited to the surface by the pack cementation method. The aluminizing process was carried out in an open atmosphere oven at 700 °C for 4 and 6 h. It has been observed that the coating layer thickness varies between 13 and 17 µm depending on the duration of cementation process. From XRD analysis, it has been detected the TiAl3, TiAl2, and TiAl phases on the coating layer. Aluminum coated and untreated Ti6Al4V alloys were subjected to oxidation tests at 800, 850, and 900 °C for 4, 20, and 40 h. The obtained nonlinear weight gain characteristic has been modeled to determine the coating status of the samples. It was determined that the highest weight gain was in the untreated sample. Using the provided model, samples were classified in terms of coating condition by systematic approach based on weight gain profile versus time. Oxidation tests also supported with DTA and TG analyses.