Relationships among crystallographic structure, mechanical properties and tribological behaviour of electroless Ni-P(9%)/B4C films

The tribological behaviour of electroless Ni-P composite coatings was inves tigated by dry sliding tests with a slider-on-cylinder tribometer. The test s were carried out in laboratory air at room temperature against a PVD-TiN coated HSS cylinder. Friction and wear data are discussed on the basis of t he mechanical properties (microhardness, plasticity parameter, fracture tou ghness) of the coatings, that were derived by indentation measurements at l ow loads. The wear depths measured on unreinforced Ni-P were about one orde r of magnitude larger than those obtained on the corresponding composite co atings. Furthermore, wear depth proved to increase with increasing annealin g time, for both pure matrix and composite layers. The wear volume Q was co rrelated to the mechanical properties using Archard-type equations. For com posite coatings the plasticity parameter delta(H) was inserted into the equ ation for the estimation of Q, in order to take into the account the action of a B4C-rich layer observed on the surface of the worn coatings. (C) 1999 Elsevier Science S.A. AU rights reserved.