| Worn steel surfaces | ||
 |
Radical
reduction of sulphur content in diesel fuel from the mid 90’s had disastrous
impact on diesel fuel’s lubricity. Due to the desulphurization process
the lubricity of diesel fuel dropped significantly and got crucial nowadays.
The lubricity performance of the diesel fuel is evaluated by the HFRR test
in Europe. The HFRR value is determined by measuring the equivalent wear
scar diameter occurred on the steel ball specimen during the test. The
topographies of these wear scars were investigated by AFM and correlation
between the morphology of the worn surfaces and the different HFRR values
has been found.
AFM imaging revealed pilled off scratch lines on the worn surface at low additives concentration with a relatively high roughness. The morphology of the worn steel surfaces was found to depend on the amount of additives. At higher additive concentration the additives and possibly the wear products might build a layer coating the steel surface. In this layer holes (lubricant pockets) were found by AFM. Left:
|
|