Scratch and Sliding Wear Testing of Electroless Ni–B–W Coating

Abstract

Electroless Ni–B–W coating is deposited on low carbon steel in an alkaline sodium borohydride-reduced electroless bath. The mechanical and tribological properties of such coatings are much necessary to be assessed to carry out application-based studies. The present work focuses mainly on the evaluation of hardness and fracture toughness of electroless Ni–B–W coatings using a scratch tester. Coating's response toward scratching is also studied thoroughly. The characteristic short-range order present in its lattice structure causes the generation of a specific behavioral pattern. Furthermore, a linear sliding wear test is carried out on coatings' surface to analyze the wear behavior at different loading conditions. The specific wear rate is observed to be minimum at a normal load of 22.5 N against Si3N4 counterbody. The patterns of tribological behavior of the coating at different load values are examined from the worn surface morphologies. But before embarking on the scratch and sliding wear tests, the synthesized coatings are characterized under field emission scanning electron microscope and X-ray diffraction in an exhaustive manner. The growth rates with respect to time and the changes in morphological aspects of the coating are also evaluated. The present study establishes electroless Ni–B–W deposits as a suitable option for protecting mechanical components against wear.