Self-lubricating metal-matrix composite CuZn-graphite coatings obtained by electrodeposition from near neutral solutions. Surface morphological analyses and chemical composition

Abstract

CuZn coatings were obtained from cyanide-free electrodeposition solutions, pH 6.6, containing graphite particles (2 µm) dispersed on them. The aim is to obtain CuZn metal-matrix composites with lubricating graphite particles as the dispersed phase. These composites, obtained by electrodeposition are called electrocomposites. They can be considered self-lubricating. Surface morphological analysis of these deposits reveal a compact fine-grained layer and above this a 7 ARTICLE TH 56 Self-lubricating metal-matrix composite CuZn-graphite coatings obtained by electrodeposition from near neutral solutions. Surface morphological analyses and chemical composition. poorly adherent coarse-grained one. The last is due to the presence of graphite particles in the solution, since this poorly adherent layer is not present in deposits obtained from free-of-graphite conditions. Only in few cases it was observed occlusion of graphite particles in the CuZn matrix. However, this occlusion occurs in the poorly adherent layer. Under the analyzed conditions of electrodeposition it was difficult to obtain CuZn-graphite electrocomposites. Regardless of graphite occlusion, chemical composition of CuZn matrix was affected by graphite dispersed in the electrodeposition solution. When comparing with CuZn matrix obtained from free-of-graphite conditions, graphite caused enrichment in Cu content of the matrix for all current densities.