Effect of Ni-W microcrystalline coating on plastic deformation behavior of Cu substrate

Abstract

Microcrystalline Ni-W alloy layers with different thickness were electroplated on the surface of Cu substrate. The mechanical properties of coating samples with different thickness were analyzed. The microstructure and fracture morphology between the substrate and the coating were observed by SEM (scanning electron microscopy) and EDS (energy dispersion spectrum). The results show that the coating thickness increases linearly from 0.031 μ m to 7.77 μ m with the increase of electroplating time. With the Ni-W coating thickness increasing, the microstructure of fracture changes from cross cracks to straight cracks, the number of cracks per unit area decreases, and the crack spacing increases from 0.79 ± 0.35 μ m to 153.56 ± 35.16 μ m. The strength and plasticity of samples with Ni-W coating are higher than those of Cu substrate film because of the restriction in dislocation movement and surface work hardening. At the same time, the coating cracks hinder the dislocation movement, absorb energy and restrain the crack growth. When the coating breaks, the dislocation slip behavior will change into plastic deformation, and there is a synergistic mechanism of interface strengthening between the substrate and the coating.

Keywords

• Ni-W microcrystalline coating
• electroplating process
• tensile strength
• plastic deformation
• dislocation behavior
• synergistic mechanism