Studies of electroless plating of Ni–Fe–P alloys and the influences of some deposition parameters on the properties of the deposits

Electroless Ni–Fe–P alloys have been deposited from a bath using boric acid as a buffer agent and sodium citrate as a complexing agent. The effects of deposition parameters, such as pH and mole ratios of FeSO4/(FeSO4+NiSO4), on the plating rate and the composition of the deposits were examined. It was found that the presence of ferrous sulphate in the bath has an inhibitory effect on the alloys deposition. As a consequence, the percentage of iron in the deposits never reaches high values which were less than 15.62 at.%. Both of the two exothermic peaks in DSC curves move to higher temperature as the Fe content in the deposits increases. The microhardness of deposits increases as in deposits the Fe content increases and the P content decreases. The structure of the as-plated Ni–Fe–P alloys plated at all conditions is amorphous. The crystallization behavior of Ni-10.7Fe-20.3P alloy was studied comparatively by using differential scanning calorimetry and X-ray diffractometry. The deposit tranformed into square Ni3P phase at 377 °C, then changed into cubic FeNi3 phase at 491 °C. The microhardness of the deposit increases with the increase of the annealing temperature up to approximately 500 °C, after which it decreases.