Ultra-mild wear of a hypereutectic Al–18.5wt.% Si alloy

Chen, M.; Alpas, A.T.

doi:10.1016/j.wear.2007.10.002

Cited by 65 publications

(26 citation statements)

References 15 publications

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“…2. The observed features were consistent with the phases commonly identified with this alloy composition and included the dark primary Si colonies, the needle like secondary Si phase, as well as the lighter grey intermetallic phases which were observed segregated at the aluminium grain boundaries [1].…”

Section: As-cast Microstructuresupporting

confidence: 84%

“…Interest in the use of hypereutectic aluminium-silicon alloys as materials for automotive die cast crankcase blocks continues [1][2][3][4][5][6][7] due to the significant environmental and fuel efficiency benefits resulting from the relatively low density of aluminium [8,9]. For surfaces exposed to tribological contacts such as the cylinder wall surface, exposure of the primary silicon colonies through chemical etching [10,11] or mechanical differential abrasion is necessary to prevent galling of the a-aluminium phase as a result of contact with the piston ring, especially during the running-in phase of operation [12,13].…”

Section: Introductionmentioning

confidence: 99%

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Dry Sliding Friction and Wear Behaviour of an Electron Beam Melted Hypereutectic Al–Si Alloy

Walker¹,

Murray

Narania

et al. 2011

Tribol Lett

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The economic and environmental benefits of using light-weighting technology in automotive applications continue to attract attention for feasible commercial solutions. This study investigates the use of pulsed electron beam melting of a hypereutectic Al-Si alloy as a possible modification procedure for cylinder crankcase bore facing surfaces. Machined surfaces of an A390 alloy were subjected to five pulsed electron doses with an applied cathode potential between 16.5 and 36 kV. It was found that increasing beam accelerating voltages led to an initial decrease (1.4 lm R a ) but subsequent increase (4.0 lm R a ) in average surface roughness values associated with surface crater formation due to sub-surface melting and eruption. Surfaces were tested under dry sliding tribological conditions against 52100 bearing steel in a reciprocating geometry. Average dynamic friction coefficients were higher (0.9) compared to the untreated alloy surface (0.6) as a result of a greater degree of adhesion to the counterface. However, FIB cross sections of worn surfaces indicated that this activated an oxidative type wear process which ultimately led to the formation of a beneficial surface tribo-film on the EBM-treated surfaces, improving the specific wear rates by up to 66%.

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Section: As-cast Microstructuresupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Dry Sliding Friction and Wear Behaviour of an Electron Beam Melted Hypereutectic Al–Si Alloy

Walker¹,

Murray

Narania

et al. 2011

Tribol Lett

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show abstract

“…Hardness measurements on the Al matrix and Si grains indicated 170 and 190 HV, respectively (measured with Mitutoyo Autovick). The former is somewhat higher than the hardness value of the Al matrix measured by Chen and Alpas of about 85 HV for Si 18.5% alloy [23][24][25]. It is recognised that this value for Si grains is probably not the latter's intrinsic hardness and may reflect in part the supporting matrix.…”

Section: Test Materialsmentioning

confidence: 56%

The Influence of Aluminium–Silicon Alloy on ZDDP Tribofilm Formation on the Counter-Surface

Shimizu

Spikes

2017

Tribol Lett

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In order to reduce vehicle weight and thus improve fuel economy, aluminium (Al) alloys have been increasingly adopted as contact surfaces such as piston skirts and cylinder liners in current engines. In general, hypereutectic Al-Si alloys are used, in which hard silicon grains are embedded in a softer Al-Si single phase matrix. It is reported that after rubbing, the matrix is removed to leave silicon grains protruding from the surface. However, the response of the counter-surface by these silicon grains is rarely investigated. In this study, mini traction machinespace layer imaging (MTM-SLIM) has been used to monitor tribofilm formation in situ and investigate the evolution of both surfaces in the contact of a steel ball on an Al-Si disc lubricated by ZDDP solution. In low-load conditions, the top layer of aluminium on the Al-Si disc is removed physically to leave silicon grains protruding from the surface, while ZDDP tribofilm pads are formed mainly on the grains. On the counter-surface (steel ball), ZDDP tribofilms are formed and build up with no wear scars. In high-load conditions, deep gaps are observed to form initially round the silicon grains on the disc. During rubbing, these become shallower, while the silicon grains start to protrude. On the steel ball, ZDDP tribofilm is generated initially over the whole rubbing track, but then the tribofilm in the middle of the track is almost completely removed by rubbing against the protruding silicon grains. Wear of the underlying steel surface then ensues.

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“…Other methods of measuring engine bore wear such as radio-active nuclide tracer (RNT) techniques [22,23] or measurement of subtle changes in height associated with aluminium or silicon particle wear using interferometry [8,9,[24][25][26][27] often refer to the regime of Ultra Mild Wear (UMW) and quote surface losses in nm/h or nm/m. Table 2 showed how the rate of material removal decreased with test length and was estimated to be 35nm/h at the end of the start-stop test compared with 68nm/h for the uninterrupted test.…”

Section: Using a Rutherford Backscattermentioning

confidence: 99%

The influence of start–stop transient velocity on the friction and wear behaviour of a hyper-eutectic Al–Si automotive alloy

Walker¹,

Kamps²,

Wood³

2013

Wear

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As worldwide automotive ownership is set to exceed 2 billion vehicles by 2030 [1], environmental and economical pressures on the automotive industry mean there is a trend to reduce harmful greenhouse gas emissions whilst simultaneously improving fuel economy. The use of electrical hybrid, start-stop idling and materials light-weighting are some of the technological solutions which can offer efficiency savings, however their combined use in a tribological context is less well understood. Interruption of piston sliding as a result of start-stop technology will simultaneously interrupt fluid film lubrication at the ring/liner interface. This could have implications on the friction and wear behaviour of Al-Si cylinder blocks, where scuffing can be an issue. In order to determine the effect of a start-stop velocity cycles on the lubricated friction and wear behaviour of a hyper-eutectic Al-Si liner, an interrupted reciprocating laboratory tribometer test programme was developed based upon the European Urban Cycle standard. Refined cast iron piston ring segments were slid at 23Hz frequency, 4MPa nominal contact pressure and 25mm stroke length against a conformal honed Alusil cylinder liner segment. Regular velocity interruptions at 60s intervals did not significantly inhibit the dynamic friction behaviour between the liner and the cast-iron piston ring segment, indicating that lubricant additive function was not significantly inhibited. However contact potential and FIB-SIMS depth profiles indicated that antiwear tribo-film thickness was reduced as a result of start-stop cycling. Mass loss from the piston ring was also notably higher as a result of the interruption of elasto-hydrodynamic lubrication causing boundary conditions at re-start and subsequent 2-body abrasion by harder protruding Si particles. Specific wear rates for the Al-Si liner as a result of start-stop velocities were surprisingly lower compared to uninterrupted tests and was believed to be due to faster running-in of the piston ring surface. These results are discussed in terms of the viability of Al-Si as engine materials running start-stop technology.

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Ultra-mild wear of a hypereutectic Al–18.5wt.% Si alloy

Cited by 65 publications

References 15 publications

Dry Sliding Friction and Wear Behaviour of an Electron Beam Melted Hypereutectic Al–Si Alloy

Dry Sliding Friction and Wear Behaviour of an Electron Beam Melted Hypereutectic Al–Si Alloy

The Influence of Aluminium–Silicon Alloy on ZDDP Tribofilm Formation on the Counter-Surface

The influence of start–stop transient velocity on the friction and wear behaviour of a hyper-eutectic Al–Si automotive alloy

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