MOS2/Ti low-friction coating for gears

The applicability of a multilayer composite surface coating in gears is discussed in this work, mainly in what concerns to gear efficiency at normal operating conditions and to scuffing load capacity. The average friction coefficient between gear teeth is discussed and compared with uncoated steel gears. The disulfide molybdenum/titanium (MOSZ/Ti) composite coating is studied and the deposition procedure is described. Several screening tests, like Rockwell indentations, ball cratering, pin-on-disc and reciprocating wear, were performed to evaluate the adhesion to the substrate, the tribological performance of this coating and his applicability in heavy loaded rolling-sliding contacts, such as found in gears. FZG gear efficiency tests were performed using type C gears in order to evaluate the influence of the surface coating in gear efficiency, for a wide range of operating conditions. These tests in conjunction with a numerical model for the energetic balance of the FZG gearbox allowed the determination of the average friction coefficient between gear teeth, taking into account the presence of the surface coating. FZG gear scuffing tests were also performed using type C gears in order to evaluate the coating anti-scuffing performance, which proved to be very significant. (c) 2006 Elsevier Ltd. All rights reserved.