We report here the impact of different alloying elements in steels on friction and wear behavior by performing ball-on-at lubricated reciprocating tribotesting experiments on 52100 ball on steel ats with different compositions (52100, 1045, A2, D2, M2, and a specialty Cu-alloyed steel) heat-treated to give similar hardness and microstructure, with polyalphaole n (PAO-4) as the lubricant. There are small variations of coe cient of friction among these alloys. The major observation is that steels containing high concentrations (≥ 10 wt.%) of Cr, Mo, and V gave rise to markedly reduced wear compared with 52100 or plain carbon steels. D2 steel, which contains 11.5 wt.% Cr as the major alloying element was the most wear-resistant. The wear resistance is strongly correlated with the e ciency of formation of carboncontaining oligomeric lms at specimen surfaces as determined by Raman spectroscopy. This correlation holds for steels heat-treated to have higher hardness and with n-dodecane, a much less viscous lubricant compared with PAO-4. Given the strong a nity of chromium to oxygen, chromium should exist as Cr 2 O 3 at the steel surfaces during testing. We have performed molecular dynamics simulation on Cr 2 O 3 and demonstrated its ability to catalyze the formation of carbon-containing oligomeric lms from hydrocarbon molecules, consistent with its known catalytic activity in other hydrocarbon reactions. We believe that chromium-containing alloys, such as D2, and coatings, such as CrN, derive their wear resistance in part from the e cient in-situ formation of wear-protective carbon tribo lms at contacting asperities.
Abstract. Molecular dynamics simulation has been carried out to go through the evaporation and condensation characteristics of thin liquid argon film in nanoscale confinement having nanostructured boundary. Nanoscale confinement under consideration consists of hot and cold parallel platinum plates at the bottom and top end of a model cuboid inside which the fluid domain comprised of liquid argon film at the bottom plate and vapor argon in between liquid argon and upper plate of the confinement. Three different confinement configurations have been considered here: (i) Both platinum plates are flat, (ii) Upper plate consisting of transverse slots and (iii) Both plates consisting of transverse slots. The height of the slots is 1.5 nm. Considering hydrophilic nature of top and bottom plates, two different high temperatures of the hot wall was set and an observation was made. For all the structures, equilibrium molecular dynamics (EMD) was performed to reach equilibrium state at 90 K. Then the lower wall is set to two different temperatures like 110 K and 250 K for all three models to perform non-equilibrium molecular dynamics (NEMD). Various system characteristics such as atomic distribution, wall heat flux, evaporative mass flux etc. have been obtained and discussed to have a clear understanding of the effect of nanotextured surface on phase change phenomena.
We report here the impact of different alloying elements in steels on friction and wear behavior by performing ball-on-flat lubricated reciprocating tribotesting experiments on 52100 ball on steel flats with different compositions (52100, 1045, A2, D2, M2, and a specialty Cu-alloyed steel) heat-treated to give similar hardness and microstructure, with polyalphaolefin (PAO-4) as the lubricant. There are small variations of coefficient of friction among these alloys. The major observation is that steels containing high concentrations (≥ 10 wt.%) of Cr, Mo, and V gave rise to markedly reduced wear compared with 52100 or plain carbon steels. D2 steel, which contains 11.5 wt.% Cr as the major alloying element was the most wear-resistant. The wear resistance is strongly correlated with the efficiency of formation of carbon-containing oligomeric films at specimen surfaces as determined by Raman spectroscopy. This correlation holds for steels heat-treated to have higher hardness and with n-dodecane, a much less viscous lubricant compared with PAO-4. Given the strong affinity of chromium to oxygen, chromium should exist as Cr2O3 at the steel surfaces during testing. We have performed molecular dynamics simulation on Cr2O3 and demonstrated its ability to catalyze the formation of carbon-containing oligomeric films from hydrocarbon molecules, consistent with its known catalytic activity in other hydrocarbon reactions. We believe that chromium-containing alloys, such as D2, and coatings, such as CrN, derive their wear resistance in part from the efficient in-situ formation of wear-protective carbon tribofilms at contacting asperities.
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