Tribological characteristics of electroless Ni–B coating and optimization of coating parameters using Taguchi based grey relational analysis

Electroless nickel coating is an autocatalytic coating whose characteristics are very much dependent on the composition of electroless bath. The present study is an attempt to minimize the friction and wear characteristics of electroless Ni–B coatings simultaneously by optimizing the three coating parameters viz. bath temperature, concentration of reducing agent and concentration of nickel source together with the annealing temperature. Taguchi based grey relational analysis is employed for the optimization of this multiple response problem using an L27 orthogonal array. Analysis of variance reveals that concentration of reducing agent has the maximum contribution in controlling the friction and wear behaviour of Ni–B coating. The interaction between bath temperature and nickel source concentration is also found to possess significant contribution in controlling the friction and wear characteristics. The surface morphology, composition and phase structure analysis are done with the help of scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD), respectively. Moreover the wear mechanism is studied and found to be in general abrasive in nature.