Experimental study on ultrasonic-assisted electrochemical polishing of NiTi alloy

Abstract NiTi alloy has a wide range of applications due to its unique superelasticity and shape memory, the superelastic function of NiTi alloy made it had been applied in building shock absorption, advanced bearings and other scenes, the shape memory function made it also applied in the fields of aerospace engine heat exchanger, cardiac medical stent and so on. In order to made NiTi alloy better applied in practice and improve its surface quality, it was crucial to polish it. In this paper, a new method of ultrasonic-assisted electrochemical polishing of NiTi alloy was innovatively proposed, and an ultrasonic electrochemical polishing device was built independently. The effects of ultrasonic amplitude, voltage and temperature on roughness were explored by Box-Behnken experimental design method. The results show that after ultrasonic-assisted electrochemical polishing, the roughness R a had been reduced from about 2 μ m to the minimum of 0.048 μ m. The surface quality of NiTi alloy was improved. The impact of micro-jet of cavitation bubble on NiTi alloy mainly occurs in the early stage, and the equivalent stress on the surface of NiTi alloy was annular, showing an increasing and decreasing trend. In the whole ultrasonic electrochemical polishing solution, a large number of micro-jets will impact the surface of NiTi alloy, thus realizing the material removal. This study enhances traditional electrochemical polishing techniques by integrating ultrasonic energy fields, thus broadening the scope of electrochemical polishing applications. Additionally, it presents a novel approach and establishes a foundation for the polishing of NiTi alloys with intricate geometries in additive manufacturing.