Co-deposition of W and Mo in electroless Ni–B coating and its effect on the surface morphology, structure, and tribological behavior

Abstract

The Ni–B binary alloy deposited by autocatalytic chemical deposition technique has tremendous potential of wear/friction reduction and wide industrial usage. A significant improvement in mechanical properties, higher hardness, and wear resistance can be achieved in electroless nickel coatings by deposition of poly-alloy coatings rather than the binary variant. The present work therefore investigates the outcome of co-deposition of both tungsten and molybdenum in binary Ni–B coatings on the morphology, structure, and tribological behavior. Ni–B–W–Mo poly-alloy coatings were deposited by chemical reduction on AISI 1040 steel. Ni–B–W and Ni–B–Mo ternary coatings were also deposited along with Ni–B for effective comparison. Tribo-tests in the as-deposited and heat-treated condition (400°C for 1 h) revealed that the anti-wear properties of Ni–B–W and anti-friction properties of Ni–B–Mo could be realized in Ni–B–W–Mo coatings. Also, Ni–B–W–Mo coatings were observed to have high W content and a compact defect-free surface morphology with dense nodules. Backscattered electron images of the worn surface of the Ni–B–W–Mo coating in the as-deposited and heat-treated condition revealed low deformation of the coating with mild abrasion and an excellent overall tribo-performance.