The effect of ethanol fuel dilution on oil performance and MoDTC tribofilms formation and composition  

作　　者：Juan RUIZ-ACERO Felipe KESSLER Henara COSTA Tiago COUSSEAU 

机构地区：[1]Polytechnic School,Universidade de São Paulo,São Paulo 05508-030,Brazil [2]School of Food and Chemistry,Universidade Federal do Rio Grande,Rio Grande 96203-000,Brazil [3]School of Engineering,Universidade Federal do Rio Grande,Rio Grande 96203-900,Brazil [4]Mechanical Engineering Department,Univ.Tecnológica Federal do Paraná,Curitiba 81280-340,Brazil [5]University of Newcastle,Callaghan,SW 2308,Australia

出　　处：《Friction》2024年第9期2108-2125,共18页摩擦（英文版）

基　　金：funded by Fundação de AmparoàPesquisa do Estado de São Paulo(FAPESP)through the R&D ConsortiumTribological challenges in flex-fuel engines,ref.2009/54891-8,and Centro Nacional de Pesquisa em Energia e Materiais(CNPEM-LNLS-National Synchrotron Light Laboratory,grant number 20170101);the partial financial support from the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico(CNPq)grant number 305374/2021-4;the partial financial support from Fundação de AmparoàPesquisa do Estado do Rio Grande do Sul(FAPERGS),Process number:172551-000901-0;the National Research Institute on Green Tribology for the Energy Transition(CT-Trib)with financial support by CNPq/Brazil via the grant number 406654/2022-0.

摘　　要：Ethanol has emerged as a promising alternative to fossil fuels,but its use can lead to significant dilution in lubricants,particularly during cold start or heavy traffic.This dilution can affect the performance of additives,including friction modifiers like molybdenum dithiocarbamate(MoDTC),which are designed to reduce friction under extreme contact conditions.Prior research suggests that ethanol may impact the performance of MoDTC,prompting this study’s goal to investigate the effects of ethanol on MoDTC tribofilms and their friction response under boundary lubrication conditions.Therefore,reciprocating tribological tests were performed with fully formulated lubricants containing MoDTC with varying ethanol concentrations.The results indicate that a critical ethanol dilution level inhibits friction reduction by MoDTC activation,resulting in friction coefficients(COFs)similar to the base oil.Surfaces tested with simple mixtures of polyalphaolefin(PAO)+MoDTC showed increased COFs with added ethanol.Analysis of tested surfaces using Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),and X-ray absorption spectroscopy near the edge structure(XANES)revealed the presence of sulfates,MoO_(3),MoS_(2),and MoS_(x)O_(y)compounds in the tribofilms formed on the surfaces,with and without ethanol diluted in the lubricant.However,the addition of ethanol increased the sulfates and MoO_(3)content of the tribofilms at the expense of friction-reducing compounds such as MoS_(2)and MoS_(x)O_(y).These findings suggest that ethanol dilution in lubricants containing MoDTC creates an oxygen-rich interfacial medium that favors the formation of compounds with insufficient friction-reducing capabilities.

关 键 词：molybdenum dithiocarbamate(MoDTC) ethanol TRIBOFILM friction modifier additive LUBRICANT 

分 类 号：TH117[机械工程—机械设计及理论]