Investigations on the structure and properties of nanocrystalline Ni-Mo alloy coatings

Ni-Mo coating with different Mo content is prepared by electrodeposition. The influences of Mo content and heat treatment on the structure, hardness, and wear and corrosion properties of coatings are studied. It is found that Ni-Mo coatings consist of nanocrystalline, and the grain size is <= 18.5 nm. MoNi intermetallic precipitates out when the annealing temperature is >= 499 degrees C. Both of the Mo content and the heat treatment are important to strengthen coatings. The highest hardness is about 10.3 GPa, corresponding to the Ni-19.1 at% Mo coating after annealing at 500 degrees C. The lowest wear rate is about 2.1 x 10(-4) mm(3) N-1 m(-1), which related to Ni-22 at.% Mo coating annealed at 450 degrees C. Additionally, Ni-16.7 at.% Mo coating after annealing at 450 degrees C shows the best corrosion resistance in 0.5 M H2SO4.