Effect of sodium hypophosphite on the structure and properties of electrodeposited Ni-W-P alloys

Amorphous and nanocrystalline Ni-W-P alloy films have been prepared by electrodeposition. The effect of sodium hypophosphite in the bath is important in determining the W and P contents of the alloy. The alloys prepared in the bath containing more than about 0.15 mol/L of sodium hypophosphite are only Ni-P alloys containing high P contents (>21% (at)) and no W at all. However, as the sodium hypophosphite content is decreased, the W content in the alloy increases and reaches about 20% (at) with decreasing P content to about 1% (at) at 6 × 10^-4 mol/L of sodium hypophosphite. The alloys containing high P contents are amorphous, while those containing high W contents have a nanocrystalline phase with apparent grain size of 2.3 nm at 20% (at) W content. These nanocrystalline alloys show high hardness values up to about 780 MVH.