Characteristics of Ni–P alloy electrodeposited from a sulfamate bath

The effect of H3PO3 concentration on Ni–P electrodeposition from sulfamate bath and the material properties of the deposit with heat treatment were investigated. With increasing H3PO3 concentration in the bath, the phosphorus content in the deposit increased, while the current efficiency slowly decreased and stress in the deposit increased. This result seems to be related to the increase of hydrogen evolution and absorption reactions accompanied by the increase of phosphorus content in the deposit. The size of the grains and the precipitates in Ni–1.52 wt.% P deposit rapidly increased during heat treatment at temperatures equal to or higher than approximately 490 °C, fairly consistent with the results of Vickers hardness tests. The microstructural and mechanical property variation of the deposits with heat treatment were explained by precipitation of Ni3P at 310 °C and recrystallization at 575 °C with the supplemental help of DSC (differential scanning calorimetry) results.