الفهرس 
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Abstract
The impact of tungsten incorporation on the chemical composition of electroless Ni-Zn-P coating and elemental distribution through the thickness of the coating were studied on copper subtstrate.
The effects of electroless nickel baths containing hypophosphite, as reducing agents, Zinc and tungsten ions were investigated. It can be shown that deposition of Ni-P-Zn-W layers with of the bath.
The speed of desposition increases by increasing sodium tungstate concentrations up to 15g/1 and further increasing of it decreases the quality of the coating. The effect of changing bath temperatures on the coating thickness at different plating times for the two Ni-P-Zn and Ni-P-Zn-W baths were studied. A noticeable change in coating thickness was found for Ni-P-Zn-W at all bath temperatures and heat treatment conditions.
The composition of electroless Ni-P-Zn and Ni-P-Zn-W were examined by energy dispersive X-ray analysis (EDAX).
The corrosion resisrant measurements showed that heat treatment of electroless nickel deposits from 500 to 700 0C for one hour is an excellent means for improving the corrosion resistance.
It was noticed that heat treatment improves the surface wear resistance and hardness value. After heat treatment at 400 0C for one hour, the wear resistance and hardness of Ni-Zn-W deposits were higher than that of Ni-P-Zn.
The effects of heat trearments on the crystallization behavior of electroless Ni-P-Zn-Wwere studied. For the as-planted samples, the X-ray diffraction patterns showed microcrystalline deposits. Good crystalline structure was achieved by heat treatment.