Surface integrity analysis of electrochemical machining of γ-TiAl alloys

Surface integrity is directly related to component performance and service life. Various characteristics of the surface integrity of the three typical γ-TiAl alloys by electrochemical machining (ECM) were studied, including surface morphology, 3D profile, surface roughness, cross section, microhardness, residual stress and element analysis. Two current densities 5 and 50 A/cm2 were selected for comparative experiments. The results show that the three γ-TiAl alloys exhibit their own unique morphologies at low current density, and there is severe localized corrosion on the machined surface, resulting in the rough surface. However, the three γ-TiAl alloys show very smooth surfaces at high current density. This result also shows that the surface roughness values of the three γ-TiAl alloys all decrease gradually with the current density increasing, in which the extruded Ti-48Al-2Cr-2Nb has lowest surface roughness value (about Ra 0.506 μm) at 50 A/cm2. It is found that the microhardness of the machined surface of the three γ-TiAl alloys all decreased slightly, with a decrease of about 10 HV compared with the matrix. The residual stress of the samples decreases slightly after ECM, and the influence of different current density on the residual stress is not obvious. Finally, it is also proved that ECM has no effect on the elements of the machined surface.