NiTi Shape Memory Alloy Etching Using Mask Fabricated by Laser Irradiation

Abstract

Etching of NiTi shape memory alloy (SMA) using mask fabricated by laser irradiation is studied in this paper. Thermal oxidized at 200-700°C in air atmosphere and unheated SMAs are electrochemically etched in 1 mol/l LiCl-ethanol electrolyte. Both unheated and heated at 200°C samples are etched and other samples (heated over 300°C) are not etched. Over 300°C heating, oxidized film was formed on SMA surface and the film has etching resistance property. To fabricate oxidized film, SMA surface was irradiated by focused Ar ion laser beam. Laser beam irradiated point is observed with optical microscope, AFM and SEM. No visible changes are found after 200mW laser beam irradiation. When laser power is 300mW, pale color discoloration area is observed. Uplift is found after 500mW X over 1s, 600mW X 0.1s or over 700mW irradiation. Laser beam irradiated surfaces are etched and etching shapes are observed. Micro pillars are found when the laser beam irradiation conditions are 300mW X over 0.7s or 400mW. When laser power is over 500mW defects are fabricated on the pillar. Fabricated pillar diameter is 2.8-15.6μm and height is 7.5-8.5μm after 5min etching. Etching after 100μm/s laser beam scanning make 5.7-7.0μm width and 9.1-10.2μm height wall shape.