Investigation Of Graphite-lead Free Copper Alloy Composite Coatings

CuSn10Pb10 is generally employed in overloading engine bearing areas on account of its higher bearing capacity and prominent wear resistance. However with the growing emphasis of human to the environment, reducing the pollution of lead and seeking lead metal alternatives are imperative. In this essay, for the sake of lead-free, we used tin bronze CuSn10 as the main raw material with adding graphite replaced lead as lubrication group, and adopted powder metallurgy process to prepare graphite-lead free copper alloy composites. Two means were used in enhancing the graphite/copper interface of traditional copper matrix composites, Ni(NO3)2·6H2O addition and Ni coated. We discussed the merits of the two kinds of process flow to seek the best preparation method. Then we made a contrast analysis with CuSn10Pb10 in microscopic structure and macro-performance to explore the feasibility of graphite-lead free copper alloy composites. We wanted to make sure whether it can instead of lead bronze CuSn10Pb10 as sliding bearing materials.Scanning electron microscopy(SEM), energy dispersive spectrum(EDS), hardness testing, friction and wear testing were conducted to analysis the morphologies of graphite particles modified by Ni, microstructure of graphite-CuSn10 composite coating and CuSn10Pb10 coating. The experimental results show: by Ni directly adding, the reduced Ni particles were loaded on the surface of CuSn10 particles, and help to link them together; by Ni coating, the graphite particles were covered completely with Ni layers; Ni addition will enhance the interface between graphite and CuSn10 matrix, and increase the hardness and anti-wear performance of the composite coatings; the optimal graphite content in the composite coatings prepared by these two methods is 10 vol%; the graphite-CuSn10 composite coatings exhibit higher tribological performance than the common used heavy load engine bearing material: CuSn10Pb10, which make them promising lead-free bearing materials for heavy engines.