Fabrication of bulk nanocrystalline Ni-W with plastic deformability electrodeposited from a sulfamate bath

Abstract

Bulk nanocrystalline Ni-W alloys were electrodeposited from a sulfamate bath with 0, 0.1, 1.0, and 5.0 g/L saccharin sodium to improve the tensile ductility. Electrodeposited Ni-W alloys have excellent wear resistance, good corrosion resistance, and high thermal stability. They have attracted much attention with respect to their potential applications to engineering devices such as micro electromechanical systems. However, the electrodeposited Ni-W alloys showed no plastic deformation. The no plasticity was attributed to the low current efficiency of conventional process for Ni-W and high internal stress of electrodeposits. Therefore, we developed a new electrodeposition process for bulk nanocrystalline Ni-W alloys. Using propionic acid and sodium gluconate as a complexing agents increased current efficiency to approximately 90% and saccharin sodium reduced the residual stress. The bulk nanocrystalline Ni-1.3at.%W alloys deposited from a sulfamate bath with 5.0 g/L saccharin sodium exhibited the tensile strength of 1.5 GPa and good tensile ductility of approximately 5%.