Surface burn behavior in creep-feed deep grinding of gamma titanium aluminide intermetallics: characterization, mechanism, and effects

Abstract

This article presents the surface burn behavior when creep-feed grinding gamma titanium aluminide (γ-TiAl) intermetallic. First, the main characteristics of burnt surface morphology were detected. Subsequently, surface burn mechanism was revealed by analyzing compositional changes in the surface layer via X-ray photoelectron spectroscopy. Lastly, the effects of grinding temperature on grinding force and surface integrity were discussed. Finding showed that a high grinding temperature would lead to a heavy color, from light brown to hyacinthine, on the burnt surface. The burning process was dominated by oxidation of Ti and Al. Ti was generally in the state of TiO2 on the ground surface, whereas lower valence oxide of Ti was found on the subsurface. This oxide layer could produce a reduced ratio of the tangential grinding force to the normal one. Elevated temperature would produce grinding and quenching cracks on a burnt surface, and tensile residual stress might be developed if the temperature is extremely high. Surface morphology and topography characteristics indicated that, unlike conventional titanium alloys (e.g., Ti-6Al-4V), a marginal physical reaction occurred on the workpiece surface during the burning process of γ-TiAl intermetallics due to poor material ductility.