High cycle fatigue behaviour of Ti–47Al–2Cr–2Nb and Ti–6242s with (Al,Cr)₃Ti plasma spray protective coating

Certain γ-TiAl alloys are slated for use in aeroengines where they will serve in intermediate temperature environments (500–650°C). Under these conditions, such alloys will provide long service life with substantial weight savings over current materials and designs. With use, it is expected that there will be interest in extending the use of γ-TiAl alloys to more aggressive engine environments where protective coatings will be necessary. Likewise, high performance Ti alloys used in certain other applications could benefit from an effective protective coating. Several very successful plasma spray coatings based on cubic trialuminide alloys, i.e. (Al,Cr)₃ Ti, have been developed to fill these needs. However, to properly design these coating–substrate systems, it is necessary to understand the influence of the coatings on the mechanical properties of the substrates. Recent high cycle fatigue (HCF) tests performed on three (Al,Cr)₃ Ti based coating designs applied to γ-TiAl and a Ti alloy show that effective protection can be provided without compromising HCF response.