The effect of heat treatment on the properties of electroless plating Ni-Fe-P alloy

Abstract

The crystallization behavior and the structure of the electroless Ni68. 6-Fe9. 6-P21. 8 deposit were studied by DSC and XRD. The results show that the as-plated deposit consists of amorphous phase, crystallizes into metastable Ni5P2(P3) and Fe-Ni(Im3 m) at 367.6°C, and transforms into Ni3P (I-4) and FeNi3 (Pm3 m) at 499.2°C. Scanning electron microscopy was performed to observe the surface micromorphology of the as-plated deposit and the deposit heat-treated at 500°C. The heat-treated consists of many grains with diameters of 10-30 nm. The microhardness of the deposit increases with the increase of the annealing temperature up to 500°C, after which it decreases. The as-plated deposit almost has no magnetism, and its magnetic properties increase with the increase of annealing temperature, showing a rapid increase at above 600°C. The saturation magnetization and the coercive force increase greatly with the annealing temperature at above 400°C. The corrosion resistances of the as-plated deposit and the deposit heat-treated at 600°C in w = 3.5% NaCl solution (pH 7.0) were investigated by mass loss tests and anodic polarization experiments. The results indicate that the as-plated deposit has a better corrosion resistance than that of the heat-treated deposit in this environment, and their anodic polarization behaviors are different. The above properties of the deposits were discussed from the structure and micromorphology of the deposits.