Structural aspects of European and American diesel engine piston deposits

Abstract

The formation of carbonaceous deposits on upper lands and ring grooves of diesel pistons is believed to be a t least partially responsible for excessive cylinder bore wear and loss of oil control infzeld service. A properly formulated diesel lubricant has, among other performance characteristics, the ability to control piston deposits, thereby fmproving overall engine performance.lhis paper describes both the chemical and physical composition, and themorphology, ofpistondeposits formedinseveralmqjorEuropeanand American diesel lubricant qualijlcationengines. Lubricant chemistry and piston temperature are shown to have a mafor influence upon deposit composition, whereas combustion soot constitutes a minorfraction of the deposit structure. Fine details within crown land and top ring groove deposits are examined through the application of Fourier Transform Infrared Spectroscopy, Thermal Gravimetric Analysis and Scanning Electron Microscopy .

Microcharacterization of heavy‐duty diesel engine piston deposits

“…This is consistent with previous observations of there being a higher inorganic content to the deposit nearer the top of the piston, 1 where higher temperatures and more aggressive conditions may be expected.…”

“…Overall, the data are similar to those recorded elsewhere. 1,2,11,12 They show absorbances due principally to C O, attributed to organic oxidation products, in the range 1800-1650 cm 1 , carboxylate and aryl -C C-absorbances in the range 1650-1500 cm 1 , carboxylate and methyl absorbances in the range 1500-1300 cm 1 , inorganic compounds and -C-Oabsorbances in the range 1300-800 cm 1 , aryl absorbances in the range 800-700 cm 1 and inorganic compounds in the range 700-500 cm 1 .…”

“…The presence of carbonaceous and other deposits in the upper land and ring groove area of diesel engine pistons is known to lead to reduced engine durability and performance, 1 therefore control of piston deposit formation is a key factor in heavy-duty diesel engine oil (HDDEO) formulation. However, piston deposit formation is not well understood and little is known about the precise chemical composition and structure of typical deposits and how these are affected by oil formulation, engine type and operating conditions.…”

“…Calcium sulphate may be found as very small crystallites, possibly submicron spherical particulates, that are speculated to form a binder layer to which the organic resinous components bond. 1 Zinc phosphates are thought to arise from thermal and/or oxidative degradation of the anti-wear additive ZDDP (zinc dialkyl dithiophosphate). In general, it appears that the inorganic content is higher at the crown/top land position and decreases towards lower positions on the side of the piston, with the organic content showing the opposite trend.…”

“…In general, it appears that the inorganic content is higher at the crown/top land position and decreases towards lower positions on the side of the piston, with the organic content showing the opposite trend. 1 Here, we describe the results of detailed microcharacterization of the deposits themselves and of the deposit/substrate interfaces. New observations are reported from which we have derived a schematic model for the structure and growth of these deposits.…”