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    Effect of Zr and Sc on Intermetallic Morphology and Hardening of an Al–Fe Alloy
    (2023-01-01)
    Chankitmunkong, Suwaree
    ;
    Eskin, Dmitry G.
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    Limmaneevichitr, Chaowalit
    ;
    Pandee, Phromphong
    ;
    Diewwanit, Onnjira
    We studied the effect of zirconium and scandium on an Al-7 wt% Fe cast alloy with potential heat- and wear-resistant applications. An addition of 0.2% Zr resulted in thinning of primary Al<inf>3</inf>Fe particles, while an addition of 0.15% Zr and 0.15% Sc changed the morphology of primary intermetallics from needles to flower-like shape. While the addition of Zr did not affect the properties, the Zr + Sc joint additions increased the hardness of the as-cast Al–Fe alloy. The hardness of the base alloy increased upon annealing from 40 to 80 HV (450 °C, 2 h) and to 110 HV (350 °C, 20 h). The wear resistance of the Al–Fe alloy was also improved by Zr and Sc addition, especially after annealing. The observed effects are likely to be linked to the supersaturation of Zr and Sc in the aluminum solid solution during solidification and precipitation of dispersoids during annealing.
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    Impact of oil additive characteristics on biofuel engine wear using electron microscopy and confocal microscopy
    (2019-01-01)
    Rungsritanapaisan, Panyakorn
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    Karin, Preechar
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    Tanprayoon, Dhritti
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    Tongsri, Ruangdaj
    ;
    Hanamura, Katsunori
    Soot particles are produced during combustion process in the diesel engine. These particles will later exhaust into the thermosphere and part of them will contaminate the engine oil. When the lubricant is contaminated with soot, diesel engine abrasion or in a worst-case scenario lubricant starvation occurs. This situation will eventually lead into engine wear. High volume of soot also raises acid level of the area. If this state co-occurs with high temperature of the engine and volatile gases during operation, engine corrosion may also be produced. This research study the effect of additive volume on the dispersion of soot in engine oil and effect of additive on size and volume of soot which affect to mechanism of wear in metal by tribology four-ball tester, image analysis by scanning electron microscope and particle size analysis by laser diffraction technique.
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    Lubrication and wear of artificial knee joint materials in a rolling/sliding tribotester
    (2007-04-01)
    Kennedy, Francis E.
    ;
    Van Citters, Douglas W.
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    Wongseedakaew, Khanittha
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    Mongkolwongrojn, Mongkol
    This paper describes the influence of lubrication on wear during testing of materials for artificial knee joints in a rolling/sliding tribotester built to simulate contact conditions in a total knee replacement. The test configuration consists of parallel cylinders (pucks) of ultrahigh molecular weight polyethylene (UHMWPE) and polished cobalt-chrome alloy in oscillatory rolling/sliding contact in a bath of dilute (25%) bovine serum. Wear tests of three different UHMWPE materials were run under constant load at 40% sliding for 1.5 million oscillation cycles at 1.5 cycles/s. Wear of the UHMWPE was determined by measuring the profile of the cylindrical contact surface of the puck before and after each test. Profile measurements were repeated after at least 53 days to eliminate the contribution from creep. Differences between initial and final profiles were attributed to wear of the UHMWPE. It was found that the largest wear depth in the lubricated tests occurred near the ends of the oscillatory contact area, while dry (unlubricated) tests of the same materials showed a peak wear depth near the center of the contact area. In the lubricated tests, the worn depth was lowest for the most heavily irradiated material. Analysis of the elastohydrodynamic lubrication in the rolling/sliding contact was carried out assuming a line-contact situation with smooth cylindrical surfaces. The time-dependent modified Reynolds equation and the elasticity equation with initial conditions were solved numerically using a multigrid technique with full approximation scheme, and using a Newton Raphson method to solve the highly nonlinear system of equations. The thickness of the lubricating film of bovine serum was determined for points along the length of the wear track. It was found that the smallest film thickness (h<inf>min</inf>) occurs very close to the location in the oscillating contact where the greatest wear occurs, owing to the very low entraining velocity near the ends of the oscillation cycle. The coefficient (K) for wear of the UHMWPE was found to be relatively constant over the central section of the oscillatory motion, but increased to a higher value where h<inf>min</inf> decreased to near zero. Thus, the important influence of lubrication on wear of artificial knee bearings was demonstrated. Copyright © 2007 by ASME.