Tribological Behavior, Mechanical Properties and Electrochemical Corrosion Response of Ultrasonically Assisted TiO2 Reinforced Electroless Ni–B Coatings

This study involves the investigation into the effect of nano-TiO 2 (Titania) reinforced into electroless Ni–B coating. The electroless coating method used in the study involves the addition of an ultrasonicated colloidal solution of nano-Titania into the electroless coating bath during deposition. Four sets of coating are prepared for the study with 0 g/l, 5 g/l, 10 g/l and 15 g/l concentrations of Titania. These as-deposited coatings are characterized using energy-dispersive X-ray analysis, X-ray diffractometry and scanning electron microscopy. The samples are also subjected to mechanical property evaluation using microhardness test, scratch test and nanoindentation test. Tribological behaviour and corrosion resistance of the coatings are evaluated in pin-on-disk tribometer and electrochemical corrosion test, respectively. The titania concentration of 10 g/l performs best among the coatings under study. The coating with titania concentration of 10 g/l shows an improvement in scratch hardness of nearly 2 times as compared to the binary Ni–B coating. The same coating when compared to the unreinforced coating also shows an increase of elastic modulus by nearly 1.5 times. The electrochemical corrosion resistance as well as the wear resistance of the same coating with a titania concentration of 10 g/l also show improvement over unreinforced Ni–B coating. This study provides a detailed analysis of the TiO 2 reinforced Ni–B coating based on their tribo-mechanical properties. Also, a saturation concentration of TiO 2 is established beyond which the coating properties start to deteriorate.