科研之友
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摘要
Ni-W coatings of different tungsten content (2-50 wt%) were electrodeposited on a steel substrates from an aqueous complex sulfate-citrate galvanic baths, under controlled hydrodynamic conditions in a Rotating Disk Electrode (RDE) system. The optimum conditions for the electrodeposition of crack-free, homogeneous nanocrystalline Ni-W coatings were determined on the basis of the microstructure investigation results. The XRD structural characterizations of Ni-W alloy coatings obtained under different experimental conditions were complemented by SEM and TEM analysis. Results of the study revealed that the main factor influencing the microstructure formation of the Ni-W coatings is the chemical composition of an electrolyte solution. X-ray and electron diffraction patterns of all nanocrystalline Ni-W coatings revealed mainly the fcc phase structure of an alpha-Ni( W) solid solution with a lattice parameter increased along with tungsten content. The use of additives in the plating bath resulted in the formation of equiaxial/quasifibrous, nanocrystalline Ni-W grains of an average size of about 10 nm. The coatings were characterized by relatively high tensile residual stresses (500-1000 MPa), depending on the electrodeposition conditions. Ni-W coatings exhibited weakly pronounced fiber type {110} crystallographic texture, consistent with the symmetry of the plating process. Coatings of the highest tungsten content 50 wt% were found to be amorphous.
- 出版日期2014-3-25
