TY - JOUR

T1 - On the Elastohydrodynamic Film-Forming Properties of Metalworking Fluids and Oil-in-Water Emulsions

AU - Liu, H. C.

AU - Pape, F.

AU - Zhao, Y.

AU - Ellersiek, L.

AU - Denkena, B.

AU - Poll, G.

N1 - Funding Information: This work was supported by the Priority Program 2231 of the German Research Foundation (DFG) with grant number 439904924. The authors are grateful to Dr. Hatem Baly of Azelis Hannover for valuable discussion, as well as for providing samples for preparing the model fluids, to Mr. Muyuan Liu and Ms. Yi Xu of Leibniz University Hannover for their help on preparing the EHL test rig. Funding Information: Open Access funding enabled and organized by Projekt DEAL. The article was funded by Deutsche Forschungsgemeinschaft, 439904924.

PY - 2023/2

Y1 - 2023/2

N2 - Oil-in-water (O/W) emulsions are water-based lubricants and used as fire-resistant hydraulic fluids and metalworking fluids (MWFs) in industry. The (elasto-)hydrodynamic film-forming properties of O/W emulsions have been studied extensively in literature. Typical elastohydrodynamic lubrication (EHL) behaviors are revealed at low rolling speeds followed by a starved EHL regime at elevated speeds. These emulsions are self-prepared and mostly stable only for a limited time ranging from hours to several days. By contrast, the film-forming behavior of water-miscible commercial MWFs (long-term stable O/W emulsions) has rarely been reported. This restricts the understanding of the lubrication status of many tribological interfaces in manufacturing processes, e.g., the chip-tool contact in cutting. In this work, the (elasto-)hydrodynamic film-forming property of two commercial MWFs is investigated by measuring the film thickness on two ball-on-disc test rigs using different optical interferometry techniques. For comparison, two self-prepared simple O/W emulsions with known formulation have also been investigated. Experimental results from the two test rigs agree well and show that the two self-prepared emulsions have typical EHL behaviors as reported in literature. However, for the two commercial MWFs, there is almost no (elasto-)hydrodynamic film-forming ability over the whole range of speeds used in this study. This could be explained by the cleaning and re-emulsification effects of the MWFs. The lubrication mechanism of the two MWFs is mainly boundary lubrication rather than hydrodynamic lubrication. Graphical Abstract: [Figure not available: see fulltext.].

AB - Oil-in-water (O/W) emulsions are water-based lubricants and used as fire-resistant hydraulic fluids and metalworking fluids (MWFs) in industry. The (elasto-)hydrodynamic film-forming properties of O/W emulsions have been studied extensively in literature. Typical elastohydrodynamic lubrication (EHL) behaviors are revealed at low rolling speeds followed by a starved EHL regime at elevated speeds. These emulsions are self-prepared and mostly stable only for a limited time ranging from hours to several days. By contrast, the film-forming behavior of water-miscible commercial MWFs (long-term stable O/W emulsions) has rarely been reported. This restricts the understanding of the lubrication status of many tribological interfaces in manufacturing processes, e.g., the chip-tool contact in cutting. In this work, the (elasto-)hydrodynamic film-forming property of two commercial MWFs is investigated by measuring the film thickness on two ball-on-disc test rigs using different optical interferometry techniques. For comparison, two self-prepared simple O/W emulsions with known formulation have also been investigated. Experimental results from the two test rigs agree well and show that the two self-prepared emulsions have typical EHL behaviors as reported in literature. However, for the two commercial MWFs, there is almost no (elasto-)hydrodynamic film-forming ability over the whole range of speeds used in this study. This could be explained by the cleaning and re-emulsification effects of the MWFs. The lubrication mechanism of the two MWFs is mainly boundary lubrication rather than hydrodynamic lubrication. Graphical Abstract: [Figure not available: see fulltext.].

KW - Film thickness

KW - Lubrication mechanism

KW - Metalworking fluid

KW - Oil-in-water emulsion

UR - http://www.scopus.com/inward/record.url?scp=85143530589&partnerID=8YFLogxK

U2 - 10.1007/s11249-022-01684-2

DO - 10.1007/s11249-022-01684-2

M3 - Article

AN - SCOPUS:85143530589

VL - 71

JO - Tribology letters

JF - Tribology letters

SN - 1023-8883

IS - 1

M1 - 10

ER -