Authors: Maura Crobu Antonella Rossi Filippo Mangolini Nicholas D Spencer
Publish Date: 2010/05/23
Volume: 39, Issue: 2, Pages: 121-134
Abstract
Zinc polyphosphate glasses are the principal component of the antiwear tribofilms formed on steel surfaces in the presence of additives such as zinc dialkyldithiophosphates In this work amorphous zinc metaphosphate glasses have been synthesized and characterized by means of Xray diffraction XRD Fouriertransform infrared spectroscopy FTIR elemental analysis and Xray photoelectron spectroscopy XPS Tribological tests were performed by rubbing steel balls against the zinc metaphosphate discs in a polyαolefin PAO bath at room temperature XPS was used in order to characterize the tribostressed areas on both metaphosphate discs and steel balls A transfer film constituted of iron and zinc polyphosphates was formed on the contact area of the balls This transfer film was found to reduce friction and prevent ball wear A reduction in the relative intensities of XPS signals related to bridgingoxygen species and a binding energy shift of 04 eV of the P 2p toward lower values demonstrated the presence of shorterchainlength phosphates inside the tribotracks on the discs Furthermore iron was transferred to the glass during the tribological tests A tribochemical reaction between zinc metaphosphate and iron oxide has been proposed as an explanation for the depolymerization of the glass and the formation of iron phosphate
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