Wear and corrosion behavior of selected up-quenched and step-quenched CuZnSn shape memory alloys

The effect of thermal treatment on the wear and corrosion behavior of three categories of Cu-Zn-Sn-Fe SMAs designated A, B, and C is studied. Wear properties were investigated using a tribometer whilst corrosion in 0.3a? M H₂SO₄ and 3.5%NaCl media was studied using the potentiodynamic polarization method. The microstructure of the alloys mainly consists of FCC Cu-rich phase and Cu₅Zn₈ phase. The up-quenched A alloys show the highest hardness and lowest wear rate values of 72.1 HRB and 0.143 mm³/N/m respectively. Average COF was higher for the samples subjected to direct-quenching (0.35- 0.12) than the up-quenched (0.16- 0.12) and step-quenched (0.2- 0.08) samples. Wear occurred by mixed mode mechanisms of abrasion and adhesion evident by grooves and wear particles on the surface. In 0.3a M H₂SO₄ medium, step-quenched alloys had corrosion rates in the range of 0.1022 to 1.1705a? mm/yr, which is lower than the range of 0.1466 to 0.2855a mm/yr, and 0.1730 to 0.6027a mm/yr obtained for direct quenched and up-quenched samples respectively. In 3.5% NaCl solution, step-quenched alloys had the lowest corrosion rates 0.0251a mm/yr relative to samples subjected to up-quenching and direct quenching treatment. Generally, step-quenching treatment effectively improved the corrosion resistance of alloys in both media.