Sliding temperature and wear behaviour of cast Al–Si base alloy

Abstract

The influence of sliding interface temperature on friction and wear behaviour of eutectic (LM13) and hypereutectic (LM28) Al–Si base alloy in as cast and heat treated condition has been investigated. LM13 and LM28 alloys having nominal composition Al–12Si–1Ni–0.8Cu–0.6Mg and Al–17Si–1Ni–0.8Cu–0.6Mg used in this study. Wear and friction tests were performed under dry sliding conditions using a pin on disc type of friction and wear monitor with the data acquisition system conforming to ASTM G99 standard. It was found that sliding interface temperature has a close relation with wear and friction response of these alloys. Initial rise in temperature reduces the wear rate and as soon as a critical temperature (CT) is crossed, wear rate abruptly increases. The friction coefficient of both alloys first decreases with rise in temperature then subsequently increases beyond a certain temperature. The influence of temperature on wear behaviour in particular was found to be a function of alloy composition and heat treatment. For as cast LM28 alloy, the critical temperature (140°C) was found to be lower than that in the heat treated condition (180°C). A temperature–wear mechanism is proposed for these alloys.     

The effect of titanium addition on the microstructure,mechanical and tribological properties of Ni3Si alloys prepared by powder metallurgy method

Ni₃Si alloy with different content of titanium was fabricated by powder metallurgy method. The microstructures, hardness and tribological properties of the alloys were investigation. The results showed that pure Ni₃Si alloy was composed of β₁‐Ni₃Si phase and γ‐Ni₃₁Si₁₂ phase, and Ni₃Ti phase formed with titanium addition. The hardness of the alloy decreased with the increasing titanium content. The friction coefficient of pure Ni₃Si alloy increased with the increasing load, while the friction coefficient of the alloy with titanium addition decreased. The wear rates of the alloys were all increased with increasing load, and the alloy with 5 % titanium addition had the best wear resistance properties. The wear mechanisms of the alloys were abrasive wear at low load, and the wear mechanisms changed to oxidative wear at high load.     

Properties of reactively cast aluminium–TiB2 alloys

Abstract

A salt base reactive casting process has been employed to produce A356 aluminium casting alloys containing fine dispersions of TiB₂. These have been compared with commercially available Duralcan A356 material with SiC particles which have also been incorporated by a casting technique. Structural, mechanical, and wear properties have been measured. These show that TiB₂ is extremely effective in enhancing modulus in addition to significantly reducing the coefficient of friction when used against an alloy steel plate. The wear rate of the alloy is found to be independent of particle type but is governed mainly by volume fraction, as is the load transition from mild to severe wear. However, the wear mechanisms for TiB₂ and SiC composites are different when the steel disc is taken into account and the wear debris examined. The plate is effectively machined by SiC, resulting in extensive damage of the mating plate. Alloy A356 with TiB₂ additions is made by reactive casting a simple alloy to process and is thereby a viable alternative to low cost Al–SiC cast composites.

MST/1854     

(Mg2B2O5w+ND)/ZK60镁基复合材料的摩擦磨损性能研究

在湿球磨条件下以600 r/min高能球磨混粉,并将球磨后的粉末经过热压烧结-热挤压成型制备(Mg2B2O5w+ND)/ZK60镁基复合材料。研究了(Mg2B2O5w+ND)/ZK60镁基复合材料在不同载荷和转速下的干摩擦磨损性能。结果表明:干摩擦条件下,材料的摩擦系数随着滑动距离的增加会经历跑和阶段和稳定阶段;材料的质量磨损率随着转速的增大而降低,随着载荷的增大而增大,且基体镁合金的质量磨损率始终低于复合材料。随着摩擦载荷和转速的增加,材料的摩擦系数减小,然后逐渐趋于平稳。混杂增强的镁基复合材料相比基体合金具有更低的摩擦系数。     

Microstructure and wear characteristics of spray formed and hot extruded Al–Si alloys

Abstract

The microstructural and wear properties of spray formed Al–6.5Si, Al–18Si and Al–18Si–5Fe–1.5Cu (wt-%) alloys have been investigated. The microstructure of the Al–6.5Si alloy exhibits the equiaxed grain morphology of the primary α-Al phase with eutectic Si at the grain boundaries. The size of the primary Si particulates in the Al–18Si alloy varied from 3 to 8 μm embedded in the eutectic matrix. Complex intermetallic phases such as β-Al₅ SiFe and δAl₄ Si₂ Fe are observed to co-exist with primary Si in the spray formed Al–18Si–5Fe–1.5Cu alloy system. The periphery of the preforms invariably showed pre-solidified particles with a large amount of interstitial pores. An extrusion ratio of 6 : 1 for these alloys led to drastic porosity reduction and extensive breaking of second phase particles. These microstructural features showed distinct variation in the wear behaviour and the coefficient of friction of the alloys. The Al–18Si–5Fe–1.5Cu alloy shows better wear resistance compared with the other two alloys, particularly at higher loads. The coefficient of friction shows a dependence upon the applied load. However, this becomes steady at higher loads. The wear behaviour of these alloys is discussed in light of the morphology of debris particles as well as that of the worn surfaces.     

Investigation of the abrasive wear behaviour of ZA-27 alloy and CuSn10 bronze

In this study, abrasive wear behaviours of ZA-27 alloy and CuSn10 bronze were investigated using a purpose-built wear tester. The ZA-27 alloy was produced by permanent mould casting. The abrasive SiC particles having 63 μm grit size was added to the lubricant oil. The wear rate and friction coefficient of alloys were determined at the different test conditions such as sliding distance, applied load, linear velocity and percentage SiC weight content. The wear surfaces of alloys were examined using SEM and EDS analysis. The results showed that the wear rate of alloys decreased with the increasing of applied load and increased with the increasing linear velocity and abrasive SiC content. It was found that the SiC particle fracture was an important mechanism determining the friction and the wear rate of alloys. CuSn10 bronze showed higher wear resistance than ZA-27 alloy under abrasive test conditions except at high linear velocities.     

Tribological behaviour and worn out surface analysis of hot extruded Al-Si-Pb alloys

Abstract

The tribological behaviour of Al-Si-Pb alloys has been studied. Specimens of these materials were tested in both the as cast condition and a hot extruded condition. It was found that hot extrusion considerably improved mechanical properties of stircast Al-Si-Pb alloys and greatly decreased the porosity that was caused by powerful stirring in atmosphere conditions. The friction coefficient and wear rate decreased with increasing lead content, in particular the antiseizure properties of Al-Si-Pb alloys containing 20 and 25 wt-%Pb were improved remarkably. The reason is that a black compact film of lubricant was formed and covered almost the entire worn surface of specimens at highly applied load level. This film is a mixture of different constitutes containing Al, Fe, Si, O, and Pb.     

Friction and wear of P/M Al-20Si-Al2O3 composites in kerosene

The results of friction and wear of powder metallurgy (P/M) Al-20 wt% Si-3 wt% Cu-1 wt% Mg-(2.5–10) vol% Al₂O₃ particulate-reinforced composites have been compared with those of the P/M aluminium alloy matrix and A-390 cast piston aluminium alloy. It was found that Al₂O₃ reinforcement reduces wear by five to eight times when mating with cast iron in kerosene: The higher the reinforcement volume, the lower was the wear. With increased volume of reinforcement the wear mechanism of composites changed from the adhesive to the fatigue/delaminating one. The wear of the cast-iron counter sample was several times higher than that for P/M composites. Considering the life of the piston-piston ring couple, the piston composite with 10 vol% Al₂O₃ appears to be the best. The rate of clearance development for this couple is twice as low as that for the conventional piston alloys.     

Effect of secondary processing on the microstructure and wear behavior of spray formed Al–30Mg2Si–2Cu alloy

In the present work, Al–30Mg₂Si–2Cu alloy has been spray formed and subsequently hot pressed for densification. The alloy is then subjected to solutionizing and isothermal aging treatments. The microstructural features, hardness and wear behavior of spray formed and secondary processed alloys have been evaluated individually and compared with that of as-cast alloy. The microstructure of spray formed alloy showed refined and globular shaped primary Mg₂Si intermetallic particles and Al₂Cu precipitate particles uniformly distributed in Al matrix. The microstructure was refined further after hot consolidation. The microstructure after solution heat treatment appeared similar to that of the spray formed alloy but aging led to a further refinement in the microstructure compared to that of the hot pressed alloy. The evaluation of wear behavior of these alloys, under dry sliding condition, showed that the age hardened alloy exhibits maximum wear resistance and minimum coefficient of friction over the entire range of applied load (10–50 N) at a sliding speed of 2 ms⁻¹ followed by hot pressed, spray formed and solution heat treated alloys. The as-cast alloy showed the least wear resistance and highest coefficient of friction. Similar trend has been observed even in their hardness values too. The wear resistance of the alloys is discussed in light of their microstructural modifications induced during spray forming and subsequent secondary processing and also the topography of worn surfaces.     

Effect of nickel aluminides on tribological behaviour of Zn-Al alloy

Abstract

Zinc-aluminium alloys are known to possess excellent bearing properties, particularly at high load and low speeds. The present work investigates the effect of nickel additions on the dry sliding wear and friction characteristics of a Zn-Al alloy at low load and high speed. Along with grain refinement, the presence of nickel improves the adhesive wear resistance as well as the friction characteristics of the Zn-Al alloy. The tribological behaviour of the alloy is explained on the basis of the nature of its microconstituents.     

Effect of titanium implantation on the friction and surface chemistry of a Co-Cr-W-C alloy

The effects of the implantation of titanium ions, to a fluence of 5 × 10¹⁷ Ti ions cm^-2 at 190 keV, on the tribological behavior of a centrifugally cast cobalt-based alloy (Stoody 3) were investigated by friction tests against a variety of alloy and carbon counterfaces. Dry sliding friction coefficients were compared with those made on similarly prepared, but non-implanted, and fatty-acid-coated samples. High friction coefficients (μ_K ≈ 0.6) for the alloy-Stoody 3 couples coincided with the formation of debris, with the same composition as the softer of the mating alloys, in the wear scars. Much lower μ_K values were measured on titanium-implanted (μ_K ≈ 0.25) and acid-coated (μ_K ≈ 0.1) surfaces. Optical microscopy indicated a change in the surface texture of the implanted surfaces attributable to sputtering. Auger spectroscopy showed that vacuum carburization of both carbide and matrix phases of the Stoody alloy occurred during implantation. The friction and wear mechanisms involved are discussed.     

Effect of sillimanite particle reinforcement on dry sliding wear behaviour of aluminium alloy composite

Abstract

The effect of sillimanite reinforcement on the dry sliding wear behaviour of aluminium silicon alloy (BS LM6) composite was investigated using a pin-on-disc sliding wear test machine. The composite specimens were prepared using the liquid metallurgy technique and 10 wt-% of sillimanite particles were incorporated in the matrix alloy. Sliding wear tests were conducted at applied pressures between 0.2 and 1.6 MPa and speeds of 1.89, 3.96 and 5.55 m s^-1. The matrix alloy was also prepared and tested under identical conditions in order to enable comparison. It was observed that the sillimanite reinforced composite exhibited a lower wear rate than the matrix alloy. Increase in applied load increased the wear rate while increase in speed exhibited the reverse effect. The seizure pressure of the composite was significantly higher than that of the matrix alloy. The temperature rise near the contacting surface and the coefficient of friction were less in the composite than in the matrix alloy. SEM micrographs of the worn surface and subsurface were used to predict the nature of the wear mechanism.     

Effect of sliding distance on the wear and friction behavior of as cast and heat-treated Al–SiCp composites

The present investigation aims to evaluate the effect of sliding distance on the wear and friction behavior of as cast and heat-treated Al–SiCp composites using pin-on-disc wear testing machine, giving emphasis on the parameters such as wear rate and coefficient of friction as a function of sliding distance (0–5000 m) at different applied pressures of 0.2, 0.6, 1.0 and 1.4 MPa, and at a fixed sliding speed of 3.35 m/s. Characterizing the alloy and composites in terms of microstructure, X-ray diffraction analysis, microhardness and wear surface analysis. The results revealed that the heat-treated composite exhibited superior wear properties than the base alloy, while the coefficient of friction followed an opposite trend. Moreover, the wear rate of the composite is noted to be invariant to the sliding distance and increased with applied pressures. Microstructure of composite shows fairly uniform distribution of SiC particles in the metallic matrix. The hardness value of heat-treated composite increased 20–30% by addition of SiC particles to the alloy, intermetallic phases like Al₂Mg₃ and Al₂CuMg, etc., were obtained from X-ray analysis. The wear mechanism of the investigated materials was studied through worn surfaces examination of the developed wear tracks.     

Dry sliding wear behaviour of Mg–10Gd–3Y–0.4Zr alloy

In present work, the wear behaviour of a Mg–10Gd–3Y–0.4Zr alloy during dry sliding has been investigated. The experiments were carried out using Ball-on-Flat type wear apparatus against an AISI 52100 type bearing steel ball counterface in a load range of 3–15 N, sliding speed range of 0.03–0.24 m/s, temperature range of 298–473 K and at a constant sliding distance of 400 m. Analyses of the wear tracks, worn surfaces and wear debris of the Mg–10Gd–3Y–0.4Zr alloy were carried out using scanning electron microscope. As a comparison, the wear properties of common AC8A aluminium alloy under the same condition also presented. The results indicated that the Mg–10Gd–3Y–0.4Zr alloy exhibited low wear rate compared with cast+T6 AC8A aluminium alloy under the same condition. The wear rate of as-cast Mg–10Gd–3Y–0.4Zr alloy was lower than that of cast+T6 Mg–10Gd–3Y–0.4Zr alloy. The Mg₂₄(Gd, Y)₅ eutectic compound of as-cast Mg–10Gd–3Y–0.4Zr alloy could resist the material flow during friction and wear, and affected its wear rate. At high sliding speed, the retained wear debris was the major constituent of producing the severely deformed layers along the sliding direction. The trapped wear debris acted as a protective layer and reduced the wear rate.     

Tribological behavior of NiTi alloy against 52100 steel and WC at elevated temperatures

The dry tribological behavior of a Ti–50.3 at.% Ni alloy at temperatures of 25 °C, 50 °C and 200 °C was studied. The wear tests were performed on a high temperature pin-on-disk tribometer using 52100 steel and tungsten carbide pins. The worn surfaces of the NiTi alloy were examined by scanning electron microscope. The results showed that in the wear tests involving steel pins, the wear rate of the NiTi decreased as the wear testing temperature was increased. However, for the NiTi/WC contact, a reverse trend was observed. There was also a large decrease in the coefficient of friction for the NiTi/steel contact with increasing wear testing temperature. The formation of compact tribological layers could be the main reason for the reduction of the wear rate and coefficient of friction of the NiTi/steel contact at higher wear testing temperatures.     

Effects of Al2O3 particle reinforcement on the lubricated sliding wear behavior of ZA-27 alloy composites

The present investigation deals with the effect of Al₂O₃ particle reinforcement on the lubricated sliding behavior of ZA-27 alloy. The composites with 3, 5, and 10 wt% of Al₂O₃ particles were produced by the compocasting procedure. Tribological properties of alloy and composites were studied, using block-on-disk tribometer at different specific loads and sliding speeds. The test results revealed that composite specimens exhibited significantly lower wear rate, but higher coefficient of friction than the matrix alloy specimens in all the combinations of applied loads and sliding speeds. The improved antiwear characteristics of the composites were influenced by positive effects of higher frictional heating on compatibility of the composite phases and suppressing micro-cracking tendency. Due to that, effects of reinforcing hard particles were manifested through the reduced wear rate of composites, especially in conditions of higher load, lower sliding speeds and higher Al₂O₃ particle content. In present wear tests, the significant forming of mechanically mixed layers was not noticed, what is confirmed by the SEM microphotographs.     

Comparative studies on wear behaviour between as cast AZ91 and Mg97Zn1Y2 magnesium alloys

Abstract

The wear behaviour of as cast magnesium alloys, Mg₉₇Zn₁Y₂ and AZ91, was investigated under dry conditions in load ranges of 20–380 and 20–240 N respectively, using a pin on disc wear testing machine. The microstructure, thermal stability and elevated temperature tensile properties were characterised by optical microscopy, X-ray diffraction, differential thermal analysis and tensile testing respectively. The wear behaviour can be divided into three successive phases in terms of surface temperature induced by frictional heat, i.e. ambient temperature to eutectic temperature or precipitate dissolution temperature, eutectic temperature or precipitate dissolution temperature to the liquidus temperature and above the liquidus temperature. The Mg₉₇Zn₁Y₂ alloy exhibited good wear resistance compared with the AZ91 alloy for applied loads in excess of 80 N, which has been explained in terms of thermal stability of the intermetallic phase and elevated temperature mechanical properties of the two materials tested, by surface temperature analysis and subsurface observation.     

The sliding wear behavior of TiCp/AZ91 magnesium matrix composites

The AZ91 metal matrix composites (MMCs) reinforced with 5, 10 and 15 wt.% TiC particulates are fabricated by TiC_p–Al master alloy process combined with mechanical stirring. The effects of TiC particulate content, applied load and wearing time on the sliding wear behaviors of the composites were investigated using MM-200 wear testing apparatus. The results show that the wear resistance and friction coefficient of the composites increased and decreased with increase of the TiC particulate content, respectively. The wear volume loss and friction coefficient of the reinforced composites as well as the unreinforced AZ91 matrix alloy increased with increase of applied load or wearing time, but the increase rates of the reinforced composites in two performance is lower than those of the unreinforced AZ91 matrix alloy. Furthermore, the sliding wear behavior of the composites and the unreinforced AZ91 matrix alloy is characterized by ploughing, adhesion and oxidation abrasion.     

Effect of Sn addition on microstructure and dry sliding wear behaviors of hypereutectic aluminum–silicon alloy A390

In this study, the effect of Sn addition on the microstructure and dry sliding wear behaviors of as-cast and heat-treated hypereutectic A390 alloys was investigated. The microstructural features of the alloys were characterized by means of optical microscope, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy techniques and their wear characteristics were evaluated at different loads. The worn morphologies of the wear surface were examined by SEM. The results show that the β-Sn in as-cast A390 alloy precipitates mainly in the form of particles within the Al₂Cu network on the interface of the eutectic silicon and α-Al phases and the grain boundaries of α-Al phase. The addition of Sn promotes the disintegrating and spheroidizing of both the eutectic and primary silicon of the A390 alloy during solid solution-aging treatment and β-Sn phase grains coalesces and grows, and some of them form the structure of Sn wrapping Si. The wear rates and friction factors of the as-cast and heat-treated A390 alloys with Sn are lower than those without Sn. At lower load, the addition of Sn changes the wear mechanism of as-cast A390 alloy from the combination of abrasive and adhesive wear without Sn into a single mild abrasion wear with Sn; at higher load, the wear of as-cast A390 alloy without Sn includes abrasion, adhesive, and fatigue one, while the addition of Sn effectively restrains the net-like cracks on the worn surface of the alloy and avoids the fatigue wear emerged.     

The effect of silver on wear behaviour of zinc–aluminium-based ZA-12 alloy produced by gravity casting

The aim of this study was to investigate the effect of different weight concentrations of silver (0.1, 0.3, 0.5 and 0.7 wt.%) on the microstructure, hardness and wear properties of the gravity cast zinc–aluminium based alloy ZA-12. The alloys were manufactured under nitrogen protective atmosphere by a gravity casting process. Metallographic studies reveal that the addition of silver to the standard ZA-12 alloy changed the volume fraction and structure of the primary β-dendrites in the ZA-12 alloy. Also, it was observed that the addition of silver to ZA12 alloy enhanced the hardness and wear properties effectively. However, the corrosion resistance was decreased with increasing silver content. In addition to this, the highest hardness value among experimental alloys was obtained for the alloy containing 0.7 wt.% Ag with 116 HB. The wear rate for all applied loads is decreased with rising silver content. A similar trend was observed for the friction coefficient. The alloy containing 0.7 wt.% Ag exhibited the highest wear resistance at all loads.