Progression of wear in the mild wear regime of an Al-18.5% Si (A390) alloy (original) (raw)
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Some studies of wear of an Al-22wt.%Si alloy under dry sliding conditions
Wear, 1982
Aluminium-based alloys, which are considered useful for applications in which the strength-to-weight ratio is important, are also being studied for substitution as wear-resistant alloys [l] for cast iron components. Al-Si alloys have been used for tribological applications under conditions of both dry and lubricated contact. The wear behaviour of hypereutectic Al-Si alloys has been studied [2 -41 under various test conditions. It was observed [l] that, among several materials studied, a hypereutectic Al-Si alloy exhibited the lowest wear rate. Thus the hypereutectic Al-Si alloys have gained a definite status as wear-resistant materials. However, there have been conflicting
Wear mechanisms experienced by an automotive grade
2015
The wear mechanisms experienced by a cast hypereutectic Al-Si-Cu alloy were studied using a pin on disc tribometer, under lubricated sliding conditions at different normal loads. The microstructure of the alloy comprised primary silicon particles and intermetallic compounds dispersed in an aluminium matrix. Optical microscopy (OM) and scanning electron microscopy (SEM) coupled with energy dispersive X-rays (EDX) were used to characterize distinctive wear features after the tests. Wear of the alloy was characterized by fracture and spallation the intermetallic compounds and the primary silicon phases from the matrix. Under this test condition, the wear rate of the material corresponded to a mild wear regime. The reasons for the development of each wear mechanism and the variations of the friction coefficient of each test condition are discussed. Vol. 5 No. 3 (2015) 339 345 Wear mechanisms experienced by an automotive grade Al-Si-Cu alloy under sliding conditions Fecha de recepción: 0...
Ultra-mild wear mechanisms of Al–12.6wt.% Si alloys at elevated temperature
Wear, 2011
An internal combustion engine made of Al-Si alloys should operate in ultra-mild wear (UMW) regime. The objective of this work was to understand the wear mechanisms operating in Al-12.6 wt.% Si alloys tested at 100 • C under boundary lubricated condition simulating UMW regime. The sliding tests were conducted on surfaces etched to protrude silicon above the aluminum surface and optical profilometery was used to analyze changes in Si morphology during sliding. Three different stages of UMW were identified. During UMW-I, formation of a discontinuous island-like tribofilm primarily consisting of zinc sulphide from lubricating oil on top of silicon particles was observed and silicon particles progressively became embedded in the matrix. A criterion for transition between UMW-I and UMW-II was developed in terms of the ratio of pile-up height to silicon height. In UMW-II, the piled-up aluminum started to wear and an approximately 100-150 nm thick continuous oil-residue layer (ORL) formed on the worn surface primarily consisting of smeared island-like tribofilm mixed with aluminum. The ORL was also supported by a sliding induced ultrafine grain aluminum layer, and consequently microstructure evolution led to a stabilized surface with lower wear loss in UMW-III compared to UMW-II. UMW-III wear rates at 100 • C were similar to those at 25 • C.
Dry/wet sliding activation wear of pure Al / R. M. Nasir...[et al.]
Faculty of Mechanical Engineering Universiti Teknologi MARA (UiTM), 2017
An experimental work to study the wear behavior of pure Aluminium (Al) block was conducted against steel counter surface in Pin-on-Disc (POD) and the aluminium ball using four ball testing (4BT) method on dry/wet sliding wear technique at room temperature. Wear test conditions of 10-50 N load with sliding speed of 20-100 rpm was used to assess the friction coefficient, wear rate and the severance of wear mechanism on the damage surface. Due to the friction from the third body abrasive and protruded Al surfaces showcased mild wear with a steady state coefficient friction ranging from 0.0019-0.0043 for dry sliding and on wet condition ranging from 0.12-0.23 in vegetable oil (with average scar area of 8.0752 mm 2) and from 0.058-0.085 for mineral oil used (with average scar area of 17.1549 mm 2). Stress generation of the uncoated sample allowed the abraded plastic deformation to be classified as severe wear.
A DISSERTATION ON WEAR BEHAVIOUR OF ALUMINIUM & BRASS
Abstract: Wear is major problem in industry and its direct cost is estimated to vary between 1 to 4 % of gross national product. Therefore many efforts have been made to produce more durable materials and techniques to reduce the wear of the tools and the engineering components. These include modification of bulk properties of the materials, surface treatments and application of the coating, etc. over the last few years many efforts have been made to understand the behavior of the surfaces in sliding contact and the mechanism, which leads to wear. The applications of the Aluminum, Mild steel composites for the machine parts, particularly due to some very attractive characteristics such as high strength to weight ratio, excellent cast ability, pressure tightness, low coefficient of thermal expansion, good thermal conductivity, good mechanical properties and corrosion resistance The composites are mainly used in aerospace, automobiles, marine engineering and turbine compressor engineering applications. MMCs are used for light weight as well as high temperature applications. MMCs found wide applications in marine castings, motor cars & lorry fittings/pistons & engine parts, cylinder block and heads, cylinder liners, axles & wheels, rocker arms , automotive transmission casings, water cooled manifolds and jackets , piston for internal combustion engines , pump parts, high speed rotating parts and impellers etc.
Effects of Dry Sliding Wear of Wrought Al-Alloys on Mechanical Mixed Layers (MML)
Aluminium alloys are very attractive compared to other materials like steels, particularly for their mechanical properties. Despite of having a relatively low density (2.7 g/cm 3 as compared to ± 7.9 g/cm 3 of steel), they also possess high ductility (even at room temperature), high electrical and thermal conductivity and resistance to corrosion and high thermal conductivity. However, aluminium by itself exhibits poor tribological properties and their usage, for example in automotive applications, has been limited by their inferior strength, rigidity and wear resistance, compared with ferrous alloys. With respect to friction and wear behaviour, it has been well understood that the tribological behaviour of aluminium alloys is strongly influenced by the mechanical, physical and chemical properties of the near-surface materials. Whether lubricated or dry sliding, there is evidence that substantial work-hardening occurs at the worn surface. Surface strains can be well in excess of those found in conventional mechanical working. Intimate contact between ductile materials in particular, normally involved transferred materials, which may result in the formation of a mechanically mixed layer (MML). The MML was generally found to be comprised of materials from both contact surfaces, and may also include oxygen, and was known to have very different properties to the Al-alloy. Although the formation of an MML was known to modify wear behaviour, the exact manner was not fully understood. Moreover, very little was known about the effect that matrix alloy composition had on MML formation although it was claimed that the MML could improved wear resistance.
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 1998
In this investigation, effects of the shape and size of silicon particles have been studied on the sliding wear response of two Al-Si alloys, namely, LM13 and LM29. The LM13 alloy comprised 11.70 pct Si, 1.02 pct Cu, 1.50 pct Ni, 1.08 pct Mg, 0.70 pct Fe, 0.80 pct Mn, and remainder Al. The LM29 alloy contained 23.25 pct Si, 0.80 pct Cu, 1.10 pct Ni, 1.21 pct Mg, 0.71 pct Fe, 0.61 pct Mn, and remainder Al. Wear tests were conducted under the conditions of varying sliding speed and applied pressure. The alloys were also characterized for their microstructural features and mechanical properties. The presence of primary silicon particles in the alloy led to a higher hardness but lower tensile properties. Further, refinement in the size of the primary particles improved the mechanical properties of the alloy system. The wear behavior of the alloys was influenced by the presence of primary Si particles and was a function of their size. Samples with refined but identical microconstituents (e.g., pressure cast vs gravity cast LM29 in terms of the size of primary Si particles and dendritic arm spacing) exhibited better wear characteristics. Their overall effect was further controlled by the test conditions. It was observed that test conditions leading to the generation of an optimal degree of frictional heating offer the best wear resistance. This was attributed to the reduced microcracking tendency of the alloy system otherwise introduced by the Si particles. The reduced microcracking tendency in turn allows the Si phase to carry load more effectively and impart better thermal stability to the alloy system. This caused improved wear resistance under the circumstances. Further, the primary Si particles improved the wear resistance of the alloy system (e.g., gravity-cast LM29 vs gravity-cast LM13) under high operating temperature conditions. Additional thermal stability and protection offered to the matrix by the primary Si phase, under the conditions of reduced microcracking tendency, were the reasons for the improved wear characteristics of the alloy system. Conversely, a reverse effect was produced at low operating temperatures in view of the predominating microcracking tendency. The study suggests that shape, size, microcracking tendency, and thermal stability of different microconstituents greatly control the mechanical and tribological properties of these alloys. The extent of effective load transfer between the phases plays an important role in this regard. Further, the overall effect of these factors is significantly governed by the test conditions.
Dry sliding wear of aluminium-high silicon hypereutectic alloys
Wear, 2014
One of the main limitations on using aluminium-high silicon (with silicon contents greater than about 20 wt%) alloys is the formation of coarse, brittle silicon particles under conventional solidification conditions. However, an increase in silicon content generally gives an improvement in wear properties so there is a drive to produce the high silicon alloys with relatively fine microstructures. Rapid solidification processing (RS) is very effective in limiting the coarsening of primary silicon due to the high cooling rate. Here flakes of material produced by chopping melt-spun ribbon have been degassed, consolidated, hot isostatically pressed and then extruded. The resulting material has been subjected to dry sliding reciprocating multi-pass wear testing at room temperature against a steel ball bearing at 10N and 100N load. The alloys compared can essentially be characterised as 'low in silicon (around 21 wt%), high in intermetallic-forming elements (Fe, Cu, Ni)' and 'high in Si (around 30 wt% Si), low in intermetallic forming elements'. The wear results show that extruded bar with composition Al 21Si 3.9Cu 1.2 Mg 2.4Fe 1.4Ni 0.4Zr has higher hardness, and hence wear resistance, than extruded bar with composition Al 29.8Si 1.3Cu 1.4 Mg 0.3Fe 0.3Ni 0.3Zr, despite the higher Si content. It is thought that, at the higher Si content, there may be silicon particle pull-out which may subsequently lead to a three-body abrasive wear mechanism. In addition, for the lower Si alloy, the higher amounts of intermetallic-forming elements are thought to be contributing to the wear resistance.
The Effects of Primary Silicon Particles on the Sliding Wear Behavior of Aluminum-silicon Alloys
Journal of Materials Science Letters, 1998
Al±Si alloys are well known for their tribological applications involving the sliding motion of one component against another [1±4]. The process of material removal or failure under those circumstances becomes quite complex in view of a large number of factors relating to materials in contact and their conditions of movement. Material-related variables include the nature, shape, size, content and mode of distribution of various microconstituents of the sliding pairs [5±14]. On the other hand, experimental parameters that could be applied include load, sliding speed, environment, test con-®guration, and so on [5±14]. Several studies have been conducted to assess the sliding wear behavior of Al±Si alloys [1±8]. However, attempts made to understand the role of microstructural features on the sliding wear behavior of the alloy system have been quite limited [5±7].
Ultra-mild wear of a hypereutectic Al–18.5wt.% Si alloy
Wear, 2008
Material removal rate from an automotive engine bore surface should not exceed a few nanometers per running hour. This corresponds to the ultra-mild wear (UMW) conditions. Understanding the role of the microstructure on the wear mechanisms in the UMW regime is essential for the development of lightweight automotive engines. In this work, sliding wear tests were performed on a hypereutectic Al-Si alloy containing 18.5 wt.% Si under a light load of 0.5 N and boundary lubricated conditions corresponding to the UMW regime using a ball (AISI 52100 steel)on-disc tribometer. Sample surfaces were chemically etched to expose silicon particles. After sliding to 6 × 10 5 cycles, no measurable mass loss was detected using an analytical balance with an accuracy of 10 −4 g. Wear damage was limited to the contact surfaces of the silicon particles. The calculated maximum contact pressure applied on the protruded silicon particles was less than the matrix hardness of the alloy, which was consistent with the experimental observations that large silicon particles in this alloy carried the applied load and prevented plastic deformation of the matrix. A eutectic Al-12% Si alloy with a softer aluminum matrix was tested under the same conditions and showed more extensive damage. In this alloy, silicon particles became embedded into the aluminum matrix, which in turn formed pileups near the particles and consequently were exposed to damage by the counterface. In 18.5% Si, neither silicon particle sinking-in nor damage to aluminum matrix in the form of plastic deformation and wear was observed. Accordingly, Al-18.5% Si was effective in maintaining a minimal surface damage under UMW conditions.