Erosion-Corrosion Behavior of Electrodeposited Amorphous Ni-W-P Coating in Saline-Sand Slurry

The amorphous Ni-W-P coating with 4.8 wt% W and 9.8 wt% P was electrodeposited from the electrolytic bath. Using a slurry pot erosion tester, the erosion-corrosion behavior of this Ni-W-P coating was investigated in 3.5 wt% sodium chloride (NaCl) slurry with 3 wt% sand particles (80 μm to 120 μm) at the impact velocities of 3.14, 5.23, and 8.37 m s⁻¹, respectively. After erosion-corrosion in the saline-sand slurry, the hardness of Ni-W-P coating was increased from HV616 to HV722. The mechanical effect of sand particle impact causes crystallization of the coating surface and the work-hardening leads to accelerated corrosion. The microstructure was transformed from amorphous to a mixture of amorphous and multiple crystal phases. With the observation of an eroded surface of the Ni-W-P coating, the fracture of the cracking lips was aggregated by the interaction between impacts of sand particles and corrosion pitting of Cl⁻ solution. The total mass-loss rate of amorphous Ni-W-P coating was increased obviously with the increase of impact velocity and could be evaluated with kV^2.9, which was approximately 10 mg h⁻¹ at the impact velocity of 8.37 m s⁻¹. Compared with Ni-P coating, the enhancement of hardness and corrosion current density of Ni-W-P coating is benefit to its lower synergism rate and higher relative wear resistance.