Formation of amorphous electrodeposited Ni-W alloys and their nanocrystallization

Ni-W Amorphous/Nanocrystalline Duplex Composite Produced by Electrodeposition

“…11,12) The conceptual model of grain-boundary phase has been employed to describe the dependence of the mechanical property on the grain size. The composite model 13,14) explains that Hall-Petch breakdown is attributed to the increased volume fraction of a comparably soft grain boundary phase as the grain size decreases. Somekawa, et al suggested that nanocrystalline and amorphous phases coexists in Ni-W alloys with grain size of 5 nm, and the amorphous phase affect the deformation and fracture.…”

Evaluation of Corrosion and Tribological Behavior of Electrodeposited Tungsten Alloys

“…Overall, Fe-W alloy coatings are characterized by higher hardness than that of Co-W deposits in the range of normal loads of 2-100 mN [18]. The maximum hardness values for Ni-W deposits usually are lower (in the range of 734±70 HV 10 ) than for Co-W and Fe-W alloys [12,14,22,23]. At higher applied loads the hardness of Fe-W and Co-W alloys can decrease, e. g. for Fe-24 at.% W deposits decreases up to 500 HV 980 [19], and for Co-13 at.% W -up to 600 HV 980 [24].…”

“…Amorphous and crystalline Fe-W, Ni-W and Co-W electrodeposits have been reported in the literature [6][7][8]. XRD analysis results indicated that as-deposited Ni-W alloys having tungsten content in their composition higher than 19-23 at.% forms nanocrystalline ("amorphous-like") structure [9][10][11][12]. Meanwhile for electrodeposited Co-W and Fe-W alloy coatings the crystallographic structure is changing from polycrystalline to nanocrystalline at tungsten content above 20 at.% [4,11].…”

“…Annealing also yields reduced internal stresses of the deposit that were related to the hydrogen evolution reaction occurring simultaneously during tungsten alloy codeposition with iron group metals. For example, the hardness of Co-27 at.% thin film increases up to 1200 HV 250 after the heat treatment at 600 °C for 2 hours in Ar atmosphere [26]; for Ni-25 at.% the hardness reaches maximum of 1450 HV 200 at annealing temperature of 600 °C for 24 h in vacuum [12]. Other authors have also reported the maximum hardness for Ni-W alloys with different compositions after annealing at 700 °C [27][28][29].The hardness of as-deposited Co-12 at.% W sample increased from 450 HV 980 (as-deposited) to 700 HV 980 following heat treatment for 1 h at 600 °C in the air [30].…”

“…Other authors have also reported the maximum hardness for Ni-W alloys with different compositions after annealing at 700 °C [27][28][29].The hardness of as-deposited Co-12 at.% W sample increased from 450 HV 980 (as-deposited) to 700 HV 980 following heat treatment for 1 h at 600 °C in the air [30]. At the higher temperatures, the hardness decreases due to the increased grain size [12].…”