Study on surface roughness of large size TiAl intermetallic blade in electrochemical machining

Abstract

Large size TiAl alloy blades as a core component in aero-engines have received a lot of attention due to their light weight and superior performance. However, precision manufacturing of such blades is very difficult using traditional mechanical cutting methods because of the large size, super twisted profile and typical difficult-to-cut materials. Electrochemical machining (ECM) is a preferred method for such blades due to its inherent characteristics. In this work, the surface quality of such blades is studied in detail and some defects on the surface of the blade are overcome. Exploratory experiments of DC ECM and pulse ECM at different pulse frequencies are carried out, and the results show that pulse ECM at low pulse frequency is more likely to obtain blade with high surface quality. A two-step variable parameter ECM strategy is proposed based on low pulse frequency, which completely removed the “patchy” morphology and raised defects on the blade surface, and reduced the surface roughness from about Ra 5.5 μm to about Ra 1.8 μm. A control method of multi-channel pressure difference at the inlet is proposed based on the direction of the flow mark, which effectively eliminated the flow mark defect on the blade surface, further reduced the surface roughness to about Ra 0.9 μm, and obtained the blade with high surface quality.