ELECTRODEPOSITED NI-CR AND NI-CR-P ALLOYS

Microcrystalline Ni-Cr and amorphous Ni-Cr-P were electrodeposited on steel substrates. It is easier to obtain the Ni-Cr-P deposit from the aqueous solution incorporating dimethylformamide and methanol in the presence of sodium hypophosphite than from a pure aqueous chloride solution. The chromium contents of the platings decrease as the bath temperature increases. The fcc nickel and r phase of as-deposited low Cr% plating converts to fcc structure upon heat-treatment, while the high Cr% plating is a bcc chromium structure. The amorphous high Cr% Ni-Cr-P plating converts to bee chromium and Ni-Cr phosphide phases upon heat-treatment, which also gives rise to a maximum hardness of approximately Hv 1050 at around 500-degrees-C.