Enhanced Fatigue Endurance and Electrical Contact Stability of Flexible Rings via Optimized Cu/Ni/Au–Co Multilayer Electroplating

Rolling electrical transmission devices for aerospace applications require high power capacity, long service life, and high reliability. As a critical rolling-contact component, the flexible ring undergoes repeated mechanical deformation and electrical loading, making its surface condition essential to fatigue endurance and contact stability. This study developed an optimized Cu/Ni/Au-Co multilayer electroplating strategy to mitigate surface degradation and unstable electrical contact. The coating comprised an optimized copper layer, a low-stress nickel sulfamate layer, and a gold–cobalt layer deposited from an electrolyte containing 0.6 g/L Co2+. The multilayer coating improved the surface and mechanical properties of flexible rings while maintaining stable electrical performance. Under current-carrying tension–compression loading, coated rings withstood over 100 million cycles, compared with approximately 30 million cycles for uncoated rings. Dynamic resistance tests using a rolling-joint verification device further confirmed stable electrical contact and good loop-to-loop consistency. These results demonstrate that the optimized multilayer coating effectively enhances fatigue endurance and dynamic contact stability, providing a practical surface-engineering solution for high-reliability aerospace rolling electrical transmission devices.