Electroless Ni-P/Ni-B Duplex Coatings: Microstructural and Mechanical Properties

Electroless Ni-B coatings are more wear resistant than tool steel and hard chromium coatings. Also, it can replace gold in electronic industries. The columnar structure of Ni-B coatings is useful in retaining lubricants under conditions of adhesive wear. However, this same structure stands for the major limitation of Ni-B coatings: a relatively poor corrosion resistance compared to electroless Ni-P deposits. Multilayer coatings obtained from dual baths have received considerable attention, considering that the combination of different coatings can improve the behavior of the whole system. The present work aims to prepare Ni-P/Ni-B duplex coating using dual bath technique to evaluate its hardness, wear resistance and scratch tests resistance. Single coatings of each electroless nickel composition with a thickness of 20 mµ were synthesized and compared with duplex layers.