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Micro morphological observation and mechanism analysis of boundary layer evolution in mixed powder lubrication
Author(s) -
Wang Chao,
Wang Wei,
Liu Yong,
Liu Kun
Publication year - 2018
Publication title -
lubrication science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.632
H-Index - 36
eISSN - 1557-6833
pISSN - 0954-0075
DOI - 10.1002/ls.1407
Subject(s) - materials science , lubrication , abrasion (mechanical) , composite material , boundary layer , layer (electronics) , blisters , shearing (physics) , tribology , metallurgy , boundary lubrication , brass , alloy , mechanics , physics , copper
In mixed‐powder‐lubricated interfaces, the lubrication performance is strongly affected by evolution of the boundary layer features. Therefore, the current investigation uses a laser microscopy system to observe the behaviours of boundary layer formed on the brass specimens during the process of graphite‐lubricated 0.45 C steel (HRC56) sliding upon brass alloy (HV160). The evolution process of mixed powder lubrication can be divided into 4 typical stages: running‐in, stable, deterioration, and damage. Multiple micro phenomena are observed in the boundary layers at different stages. These include extent of layer coverage, flaking, local adhesion, lamellar shedding, blisters, pits, and abrasion damage. These phenomena indicate that the boundary layer deteriorates from full coverage to a damaged powdery film, and eventually the serious wear on metal substrate. Moreover, an interface model of mixed powder lubrication is established to explain the changes in boundary layers. The model displays that the typically micro events above are related to the quantitative degree of overlapping of the asperities between opposing surfaces. At first, many particles bear the load collectively and adapt to velocity differences through inner shearing in powder layer. Later, plastic deformation and abrasion between asperities play a major role in surface velocity accommodation, and the metal substrates bear the load more directly.

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