Dry sliding wear in binary Al-Si alloys at low bearing pressures (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
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].
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.
Progression of wear in the mild wear regime of an Al-18.5% Si (A390) alloy
Wear, 2006
The mild wear regime of a cast Al-18.5% Si (A390), a lightweight alloy used in automotive components requiring wear resistance, was investigated in order to characterize the progression of the sliding wear processes. Block-on-ring (SAE 52100 steel) type sliding wear tests were conducted under a controlled dry air environment with 5% relative humidity. It was observed that the mild wear regime consisted of two sub-regimes: The first sub-regime of mild wear (MW-1) occurred at loads between 0.2 N and 35 N, and the second sub-regime of mild wear (MW-2) between 60 N and 150 N. A common characteristic of MW-1 and MW-2 was the attainment of steady-state wear conditions. The load (L) dependence of the steady-state wear rates (W) in both sub-regimes was expressed as W = C(L) n , where C 1 = 1.08 × 10 −4 , n 1 = 0.56 for MW-1 and C 2 = 2.18 × 10 −4 , n 2 = 0.67 for MW-2. A transition regime, where the wear rates of MW-1 increased by 270%, occurred in the 35-60 N load range. The transition between MW-1 and MW-2 was accompanied by a rapid increase (25%) in the amount of material transferred to the counterface. Sliding wear in both sub-regimes proceeded by the formation of tribolayers that were initiated by iron transfer from the steel counterface to the silicon particles on the contact surfaces. Compared to MW-1, tribolayers were formed at a faster rate in MW-2 and the amount of material transferred to the counterface was larger. Also, in MW-2 the magnitudes of plastic strains (ε) in the deformed aluminum subsurfaces below the tribolayers were higher, e.g., at 40 m below the surface ε = 3 at 60 N, compared to ε = 0.1 at 10 N at the same depth. In addition, in MW-2, both the tribolayers and the material transferred to the counterface contained layers of aluminum, implying that the aluminum matrix became in contact with the counterface. Spallation of thick tribolayers formed in MW-2 as well as extrusion of exposed aluminum surfaces over the tribolayers were among the main reasons for the higher wear rates in this regime compared to MW-1.
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.
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.
Effect of Si Content and Microstructure on the Wear Behaviour of Al-Si Alloys
Dry sliding wear of Al-Si cast alloys with three different compositions and different microstructures have been examined. A pin-on-disk machine was used for this purpose with silicon carbide paper counterface. Worn surfaces and microstructures of Al-Si alloys were examined by scanning electron microscopy and optical microscopy, respectively. Optical microscopy examinations revealed that the microstructures of these alloys were altered by heat treatments and with Na additions. The results show that the microhardness and the wear resistance increase as the silicon content increases. Spheroidising heat-treatment and Na-modification are observed to enhance the hardness and the wear resistance of these alloys.
Effect of element additions on wear property of eutectic aluminium-silicon alloys
Wear, 1996
The effects of cerium, zinc and zirconium additions and subsequent heat treatment on wear of the eutectic aluminium-silicon alloys have been investigated in dry sliding against a steel counterface by using a pin-on-disc machine. Wear surfaces and debris were examined by scanning electron microscopy. Wear characteristics of both binary Al-Si alloys and a commercial LM 13 alloy, were also studied and compared with those of the Al-Si alloy containing the Ce, Zn and Zr. The k-values of the ALSI (Al-12.3%Si), LM13, ASMC-1 (Al-12.3%Si-0.75%Mg-0.26%Ce) and ASMC-1 (heat-treated) obtained are 5.795 X 10e4, 4.750 X 10m4, 4.311 X 10m4 and 3.981 X lO-4 mm3 N-' m-', respectively.
Crystals, 2022
The microstructure, mechanical properties, and wear behavior of three Al–Si alloys, namely: Al–1.3%Si, Al–1.5%Si and Al–13.5%Si were investigated. The specimens were examined by using an optical microscope to investigate the microstructural features of pin materials. Microhardness numbers and mechanical behavior parameters were determined by using a microhardness indenter and compression test, respectively. The dry sliding wear test was carried out using a pin-on-disc apparatus by varying the rotational speed (250, 350, and 450 rpm), normal load (5, 10 and 20 N) and test time (5, 10 and 15 min) at a constant sliding diameter of 300 mm. The surface roughness index (Ra) of the worn surfaces was determined by using a profilometer. The microstructure of Al–1.3%Si alloy was described as a fine eutectic colonizing in the FCC-Al phase matrix. Coarse eutectic dendrites surrounding the primary FCC-Al grains were observed in Al–1.5%Si alloy. The microstructure of Al–13.5%Si alloy showed a uniform layered structure of FCC-Al + Diamond Si eutectic. The average microhardness number was directly proportional to the Si concentration. Al–13.5%Si alloy with a high microhardness number (47.16 HV) showed excellent resistance to wear and exhibited a smoother surface at the end-of-wear test. The improved wear resistance in this case could be due to the presence of Diamond-Si hard phase in large quantities compared with other compositions. On the other hand, Al–1.5%Si alloy showed poorer resistance to wear because the mass loss action was dominated by a particle detachment mechanism. The response surfaces of the mass loss vs. speed, normal load and time showed increased mass loss when the three controlled parameters were increased. However, Pareto charts of the main effects of parametric interactions showed that the normal load was the main factor that must be considered when studying the tribological properties of Al–Si alloys. View Full-Text