Lubrication of aluminium–silicon surfaces with ZDDP and detergents

Abstract

A review of the lubrication of aluminium-silicon (Al-Si) substrates by zinc dialkyldithiophosphate (ZDDP) and detergent engine oil additives is presented. Greater attention has been paid to understand the interactions of ZDDP, rather than detergents, with the aforementioned non-ferrous substrates. Zinc dialkyldithiophosphate generates tribofilms on both aluminium and silicon regions of aluminium-silicon alloys. However, film formation is believed to occur on silicon grains within the alloy, and those layers observed on aluminium regions are material transfer or the product of ZDDP thermal decomposition. There were many similarities in terms of film thickness, reduced elastic modulus, tribochemistry and topography of ZDDP derived tribofilms on both ferrous and Al-Si substrates. Calcium carbonate based films were observed on silicon grains when the aluminium alloys were lubricated with overbased calcium sulphonate, the tribochemistry and topography of which were similar to layers formed on ferrous substrates. When lubricated with either fully formulated oil or lubricants containing both detergent and ZDDP, the subsequently generated films were of varying chemistry, but often contained zinc or calcium phosphate compounds. The antiwear characteristics of ZDDP and calcium sulphonate tribofilms on ferrous and aluminium-silicon substrates are discussed, with the mechanical and film thickness data for such layers presented.

Friction and wear performance of multilayered a-C:H:Al coatings

“…Indeed when aluminum is added to an amorphous carbon matrix it can be detected as pure metallic nanocristallites [11] or oxide [18], but never as carbide. According to Burkinshaw et al the presence of aluminum in the coating and especially on its surface can promote the formation of a tribofilm in lubricated conditions [20], leading to the reduction of friction. However it is important to control the amount of aluminum that is added to DLC because its introduction systematically causes a drop in hardness according to the different research groups who measured mechanical properties.…”

Influence of roughness on ZDDP tribofilm formation in boundary lubricated fretting

“…1 However, due to rubbing action and significant energy dissipation at contact interface, an antiwear tribofilm can be formed when zinc dialkyldithiophosphate (ZDDP) or other high pressure additive is present. [2][3][4] The mechanisms by which the ZDDP tribofilm reduces wear are believed to be as follows: 5 (i) protection of surface from corrosion (ii) its mechanical properties (iii) support of load (iv) preferential shearing (v) removal of hard Fe 2 O 3 particles. However, it is important to understand that the formation of tribofilm is a dynamic process; hence, the creation rate should be in balance with the removal rate of the tribofilm in order to form stable layer and to protect the surfaces.…”

“…However, due to rubbing action and significant energy dissipation at contact interface, an antiwear tribofilm can be formed when zinc dialkyldithiophosphate (ZDDP) or other high pressure additive is present 2 – 4. The mechanisms by which the ZDDP tribofilm reduces wear are believed to be as follows:5…”