Environmental Protection of Gamma Titanium Aluminides by Coatings

摘要

Titanium aluminides have attracted significant attention for automotive and aerospace applications since materials properties have been strongly improved over the last years,and engineers have become more familiar to design with a material that shows limited ductility and damage tolerance.Part of the reason for slow introduction into service is the complexity of materials processing which is attributed to - a strong dependency of component properties on alloy chemistry and microstructure.Moreover,titanium aluminides can suffer from substantial degradation caused by interaction with the environment at elevated temperatures,typically beyond 750℃. The paper will provide an overview of the research and development activities on coatings for protection of gamma titanium aluminides as part of the European Framework Programme project INNOVATIAL led by the author.The paper addresses different coating development strategies followed in this project,such as intermetallic coatings,nitride coatings as well as thermal barrier coatings.It will be shown,that some of the candidates provide good protection against oxidation up to 900℃.The oxidation results indicate that in addition to coating chemistry the deposition process plays a major role in improving properties.Here, a new HIPIMS('High Power Impulse Magnetron Sputtering) process has demonstrated its capability to provide coatings with very good adhesion and high density that can effectively protect titanium aluminides against environmental attack.