Abstract
TiN films have been prepared by reactive rf magnetron sputtering on mild steel substrates, and electroless Ni-P plating has been introduced as an interlayer. A hypophosphite-based bath has been used in this study to produce electroless Ni-P coatings. The electroless Ni-P deposits crystallize during rf sputtering due to the high sputtering temperature and a TiN/Ni 3 P/Fe coating assembly is formed. The pH value of the bath will affect the phosphorus content of the electroless Ni-P deposits, and the phosphorus content changes from 6.7 wt.% to 11 wt.% for pH 5.5 to pH 4.0. It is observed that the Ar/N 2 flux ratio has a significant influence on the phase and structure of the deposited TiN film. The deposition rate increases as the nitrogen content is decreased. Pure TiN coatings are obtained for the Ar/N 2 flux ratio range from 90/10 to 70/30. Unreacted Ti is found at an Ar/N 2 ratio of 95/5 and 60/40 due to the incomplete reaction to form TiN. The employment of an electroless Ni-P deposit results in an increase in the surface microhardness and the adhesion strength. The surface hardness values were as high as 2266 HK 1 , close to the hardness of bulk TiN with the formation of an Ni 3 P interlayer modified TiN coating. © 1993.