Vacuum heat treatment of electroless Ni-B coatings

Electroless nickel-boron plating with subsequent rapid heat treatment in vacuum has been tried on steel substrate in an effort to obtain hard engineering coatings. By selected conditions of heat treatment in a high vacuum environment (a type of rapid quenching), the plating can acquire chromium equivalent hardness without the effluents of the hard chromium plating process. The resulting surfaces were examined and characterized under an optical and a scanning electron microscope. XRD analysis was also performed to investigate re-crystallization effects. The fabricated materials were also tested under corrosion conditions and linear polarization measurements were performed. The results show that after a 5-min heat treatment in vacuum, the plating acquires a crystalline structure with very good adhesion to the substrate material, obtained so far by several weeks/months thermal treatment. (C) 2003 Elsevier B.V. All rights reserved.