Evaluation of the performance of electroless Ni-B coated brass contacts under fretting conditions

The performance of electroless (EL) Ni–B coated brass contacts under fretting conditions was evaluated. The contact resistance of EL Ni–B coated brass contact was measured as a function of fretting cycles. The surface profile and wear depth of the fretted zone were measured using laser scanning microscope. The study reveals that EL Ni–B coated contacts exhibit better performance under fretting conditions. However, at conditions which are prone for severe oxidation such as, low frequency (3 Hz) or high temperature (155°C), EL Ni–B coated contacts fail to exhibit a better stability. The quick removal of the oxide film by fretting motion, rapid oxidation of the fresh metallic particles and trapping of the oxidation products in the remaining coating, cause the contact resistance to increase to unacceptable levels at such conditions. The study concludes that EL Ni–B coating is not a suitable choice for connector contacts that could experience fretting under highly oxidizing conditions.