Electrical contact strengthening of induction-clad Ni–40% WC composite coatings on 40Cr substrates

• Ni–40% WC composite coatings were treated by electrical contact strengthening (ECS).
• Metallurgically bonded composite coatings with low porosities and fine grains were obtained after ECS.
• The coating microhardness increased with increasing contact current.
• The wear resistance of the Ni–40% WC composite coating increased with increasing contact current.

Ni–40% WC composite coatings were prepared on 40Cr surfaces by high frequency induction cladding and then were treated by electrical contact strengthening (ECS) to further improve the coating properties. The effects of ECS on the coating microstructure, microhardness, phase transformation and wear behaviour were investigated using optical microscopy, field emission scanning electron microscopy, Vickers hardness measurements, X-ray diffraction and rolling contact wear tests. As the contact current increased, the porosity and grain size of the resulting composite coating decreased, and its cohesion increased. The hard phase in the coatings also diffused further. After ECS treatment, the average hardness of the Ni–40% WC composite coatings ranged from 652 HV0.1 up to 906 HV0.1. As demonstrated by the results of the rolling contact wear tests, the composite coatings treated by ECS exhibited improved wear resistance.