Dry sliding wear of eutectic Al–Si

The wear of as-cast eutectic Al–Si was studied using pin-on-disk tribotests in two different environments, air and dry argon. The counterface in all tests was yttria-stabilized zirconia. It was found that wear of the Al–Si was reduced by about 60% by the removal of oxygen from the test environment. The zirconia counterfaces showed measurable wear after tests performed in air, while there was very little wear of the zirconia for tests conducted under argon. The near-surface regions of the Al–Si pins were examined using a transmission electron microscope (TEM), using specimens produced by focussed ion beam milling. The specimens that had been worn in air were characterized by a near-surface mechanically mixed layer containing a considerable amount of both aluminum oxide and zirconium oxide—the aluminum oxide particles had evidently acted as abrasive agents to remove material from the zirconia counterface. In contrast, TEM analysis of the Al–Si tested in argon showed little zirconium oxide in the near-surface regions.     

Hardness and wear behaviour of electroless Ni–B coatings

Depth-dependent hardness variation of dimethylamine borane-reduced electroless Ni–5?wt-%B deposits has been examined using the nanoindentation technique. The deposits were characterised using ICP-OES, FESEM, XRD and DSC for evaluating the composition, morphology, structure and phase transformation behaviour, respectively. Coatings were also analysed for hardness and wear resistance. The surface of the as-plated deposit exhibits a typical nodular morphology. DSC traces show the presence of a single exothermic peak at 313°C conforming to its phase transformation. X-ray diffraction pattern of as-prepared deposit contains a mixture of amorphous and sharp microcrystalline nickel peaks. Heat-treated coating exhibits improved hardness and wear resistance. Depth-dependent nanohardness profile of as-deposited film neither obeys Nix–Gao nor the Lam–Chong model of indentation.     

A systematic approach to design against wear for Powder Metallurgy (PM) steel parts: The case of dry rolling–sliding wear

Aim of this work is proposing a systematic design approach for wear resistant components produced by Powder Metallurgy (PM). Wear is a cause of failure for many industrial PM parts. Gears and cams, for example, are subjected to rolling and rolling–sliding wear, dry or lubricated depending on the applications. The design criteria are mostly empirical, thus resulting fully conservative, sometimes excessively conservative. A need for defining design criteria for wear resistant PM parts is thus revealed, to exploit at best the specific characteristics of both technology and materials.     

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.     

Sol–gel derived nickel-doped TiO2 films as wear protection coatings

Thin films of pure and Ni-doped TiO₂ were prepared on a glass substrate by sol–gel and spin-coating process from specially formulated ethanol sols. The morphologies of the films surface were observed with atomic force microscope (AFM). The tribological properties of the obtained thin films sliding against steel ball were evaluated on a one-way reciprocating friction tester. AFM results show that by the addition of the Ni in TiO₂, smooth surfaces were obtained. As a result, the Ni-doped TiO₂ films exhibit better wear protection properties than pure TiO₂. The best protection was observed for 5% Ni-doped TiO₂ films in this study.     

Influence of nanolubricant particles’ size on flank wear in hard turning

This paper presents the effects of cutting speed, nanoparticles’ size, and their concentration in water-based TiO₂ nanofluid on the magnitude of tool flank wear and tool wear rate. The types of nanoparticles and base fluid, nanoparticle size, and nanoparticle concentration can affect the tribological and heat transfer properties of nanofluids, and thereupon, these parameters can affect the cutting forces and temperatures during the metal cutting process, thereby affecting tool wear and nanolubricant consumption. According to the achieved results, with an increase in the size of nanoparticles from 10 to 50 nm, the average decrease in cutting tool flank wear reduces from 46.2% to 34.8%.     

Fretting wear study of surface modified Ni–Ti shape memory alloy

A combination of shape memory characteristics, pseudoelasticity, and good damping properties make near-equiatomic nickel–titanium (Ni–Ti) alloy a desirable candidate material for certain biomedical device applications. The alloy has moderately good wear resistance, however, further improvements in this regard would be beneficial from the perspective of reducing wear debris generation, improving biocompatibility, and preventing failure during service. Fretting wear tests of Ni–Ti in both austenitic and martensitic microstructural conditions were performed with the goal of simulating wear which medical devices such as stents may experience during surgical implantation or service. The tests were performed using a stainless steel stylus counter-wearing surface under dry conditions and also with artificial plasma containing 80 g/L albumen protein as lubricant. Additionally, the research explores the feasibility of surface modification by sequential ion implantation with argon and oxygen to enhance the wear characteristics of the Ni–Ti alloy. Each of these implantations was performed to a dose of 3 × 10¹⁷ atom/cm² and an energy of 50 kV, using the plasma source ion implantation process. Improvements in wear resistance were observed for the austenitic samples implanted with argon and oxygen. Ion implantation with argon also reduced the surface Ni content with respect to Ti due to differential sputtering rates of the two elements, an effect that points toward improved biocompatibility.     

Microstructure,mechanical and wear properties of Cu–ZrO2 nanocomposites

Cu–ZrO₂ nanocomposites were produced by the thermochemical process followed by powder metallurgy technique. Microstructure development during fabrication process was investigated by X-ray diffraction, field emission scanning electron microscope and transmission electron microscope. The results show an improved distribution of zirconium dioxide (ZrO₂) nanoparticles (45?nm) in the copper matrix, which resulted in the improvement of mechanical properties of Cu–ZrO₂ composites. The nanocomposite with 9 wt-% ZrO₂ possesses the highest hardness (136.5 HV) and the superior compressive strength (413.5?MPa), resulting in an overall increase by 52 and 25%, respectively. The wear rate of the nanocomposites increased with increasing applied loads or sliding velocity.     

Microstructure and wear behaviour of silicon doped Cr–N nanocomposite coatings

Hard Cr–N and silicon doped Cr–Si–N nanocomposite coatings were deposited using closed unbalanced magnetron sputtering ion plating system. Coatings doped with various Si contents were synthesized by changing the power applied on Si targets. Composition of the films was analyzed using glow discharge optical emission spectrometry (GDOES). Microstructure and properties of the coatings were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and nano-indentation. The harnesses and the elastic modulus of Cr–Si–N coatings gradually increased with rising of silicon content and exhibited a maximum at silicon content of 4.1 at.% and 5.5 at.%. The maximum hardness and elastic modulus of the Cr–Si–N nanocomposite coatings were approximately 30 GPa and 352 GPa, respectively. Further increase in the silicon content resulted in a decrease in the hardness and the elastic modulus of the coatings. Results from XRD analyses of CrN coatings indicated that strongly preferred orientations of (111) were detected. The diffraction patterns of Cr–Si–N coatings showed a clear (220) with weak (200) and (311) preferred orientations, but the peak of CrN (111) was decreased with the increase of Si concentration. The XRD data of single-phase Si₃N₄ was free of peak. The peaks of CrN (111) and (220) were shifted slightly and broadened with the increase of silicon content. SEM observations of the sections of Cr–Si–N coatings with different silicon concentrations showed a typical columnar structure. It was evident from TEM observation that nanocomposite Cr–Si–N coatings exhibited nano-scale grain size. Friction coefficient and specific wear rate (SWR) of silicon doped Cr–N coatings from pin-on-disk test were significantly lower in comparison to that of CrN coatings.     

Abrasive wear behaviour of hard powders filled glass fabric–epoxy hybrid composites

The effect of incorporation of tungsten carbide (WC) and tantalum niobium carbide (Ta/NbC) powders on three-body abrasive wear behaviour in glass fabric–epoxy (G–E) composites was investigated and findings are analysed. A vacuum assisted resin transfer moulding (VARTM) technique was employed to obtain a series of G–E composites containing different fillers (WC and WC + Ta/NbC). Dry sand rubber wheel abrasion test was carried out at 200 rpm speed. The effect of different loads (22 and 32 N) and abrading distances (from 135 to 540 m) on the performance of the wear resistance were measured. The wear volume loss of the composites was found increasing with the increase in abrading distances and under the same conditions the specific wear rate decreases. The hard powders filled G–E composite systems exhibit lower wear volume loss and lower specific wear rate as compared to unfilled G–E composite system. The features of worn surfaces of the specimen were evaluated at higher and lower abrading distances at load of 32 N were using scanning electron microscope (SEM) and results indicate more severe damage to matrix and glass fiber in unfilled composite system as compared to hard powder filled composites.     

Wear characteristics of TiC reinforced cast iron composites Part 2 – Abrasive wear

Abstract

The presence of carbide particles in metal matrix composites improves abrasive wear resistance properties. Abrasive wear characteristics of TiC reinforced cast iron composites have been investigated. The TiC particle size and distribution influence the wear properties of the composites. TiC reinforced cast iron composites possess better wear resistance properties than those of chromium cast irons with and without nitrogen.     

Studies on mechanical and dry sliding wear of Al6061–SiC composites

Particulate reinforced Al-MMCs exhibits better mechanical properties and improved wear resistance over other conventional alloys. In the present paper, the experimental results of the mechanical and tribological properties of Al6061–SiC composites are presented. The composites of Al6061 containing 2–6 wt% SiC were prepared using liquid metallurgy route. The experimental results showed that the density of the composites increase with increased SiC content and agrees with the values obtained through the rule of mixtures. The hardness and ultimate tensile strength of Al6061–SiC composites were found to increase with increased SiC content in the matrix at the cost of reduced ductility. The wear properties of the composites containing SiC were superior to that of the matrix material.     

Microstructure and wear performance of Ni–20 wt.% Pb hypomonotectic alloys

The tribological properties of Ni–20 wt.% Pb alloys were measured by using a ball-on-disc reciprocating tribo-tester. The effects of load, sliding speed and melt undercooling on wear rate of the sample were investigated. The worn surface of Ni–20 wt.% Pb was examined using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results show that the wear properties of the samples undercooled by 85 and 390 K are obviously superior, which is attributed to more efficient transfer of Pb from the bulk material to the worn surface. The lubricating film is identified as a mixture of Ni₂O₃ and lead oxide by XPS analysis. At the same load or sliding speed, the predominant wear mechanisms can be identified as oxidative wear for the lower and larger undercooling and plastic deformation for the medium undercooling.     

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.     

Note on POD test parameters to study wear behaviour of alumina–titania coatings

Wear behaviour of atmospheric plasma sprayed (APS) alumina–titania coating is investigated using Pin-On-Disc (POD) test. Mean friction coefficient values are assessed using the cumulative probability plot. Results showed that the friction coefficient increased with both sliding velocity and applied load.     

Oxidation and abrasive wear of Fe–Si and Fe–Al intermetallic alloys

In the present work, intermetallic alloys Fe–Si and Fe–Al (Fe₃Si–C–Cr and Fe₃Al-C), produced by induction melting, were evaluated regarding their oxidation and abrasive resistance. The tests performed were quasi-isothermal oxidation, cyclic oxidation, and dry sand/rubber wheel abrasion. As reference, the ASTM A297-HH grade stainless steel was tested in the same conditions. In the oxidation tests, the Fe–Al based alloy presented the lowest oxidation rate, and the Fe–Si based alloy achieved the best results in the abrasion test, showing better performance than the HH type stainless steel.     

Dry sliding wear behaviour of hypereutectic Al–Si piston alloys containing iron-rich intermetallics

The effect of iron-rich intermetallics on the wear behaviour of Al–Si hypereutectic alloys has been studied. Dry sliding wear tests have been conducted using a pin-on-disk machine under different normal loads of 18, 51, 74 and 100 N and at a constant sliding speed of 0.3 m/s. The addition of 1.2 wt.% Fe to the LM28 alloy increased the wear rate due to the formation of needle beta intermetallics. Introducing 0.6 wt.% Mn to the iron-rich alloy changed the beta intermetallics into the modified alpha phases, and therefore reduced the detrimental effect of iron. TIG welding method as a surface melting process was applied on the iron and manganese containing alloy and led to a fine microstructure and increased the wear resistance.     

Accelerated wear testing for evaluating the life characteristics of copper–graphite tribological composite

Sliding wear is a key determinant of the performance of electrical sliding contacts used in electrical machines. The behavior of the contact in sliding couple is controlled by the mutual metal transfer, friction and wear. Product life and reliability of sliding contacts are dictated by wear phenomenon. The present paper focuses on evaluation of tribological performance of copper–graphite composites using reliability theory. These composites are made up of a high electrical and thermal conductivity matrix with a solid lubricant reinforcement, making it most suitable for sliding contacts. Traditional life tests under normal operating condition would be a time consuming process due to a very long expected life of the composite. Hence, accelerated wear testing was carried out for evaluating the life characteristics. Analysis was then performed on the times-to-failure data and reliability models were developed. Life-stress relationship based on the inverse power law-Weibull model was used to make reliability predictions at normal usage level.     

Development,characterization and erosion wear response of plasma sprayed fly ash–aluminum coatings

This paper describes the processing, characterization and the erosion wear response of a new class of metal–ceramic composite coatings deposited on metal substrates by plasma spraying. Coatings are developed on aluminum substrates using fly ash pre-mixed with aluminum powder in different weight proportions at various plasma torch power levels ranging from 9 to 18 kW DC. The coatings are characterized in terms of thickness, interface adhesion strength and deposition efficiency. Maximum adhesion strength of about 35 MPa is recorded with coatings deposited at 12 kW power level. It is noticed that the adhesion strength of fly ash coating is improved with pre-mixing of aluminum up to 15 wt.% in the feed material. To study the erosion wear behavior of the coatings, a plan of experiments based on the Taguchi technique is used to acquire the erosion test data in a controlled way. An orthogonal array and signal-to-noise ratio are employed to investigate the influence of the impingement angle, impact velocity, erodent size, stand-off-distance and the aluminum content in the feed stock on the erosion rate. The study reveals that the impact velocity is the most significant factor influencing the erosion wear rate of these coatings.     

Dry sliding wear behavior of aluminum based hybrid composites with graphite nanofiber–alumina fiber

The wear behavior of aluminum based hybrid composites reinforced with graphite nanofiber (GNF) and alumina short fiber (Al₂O_3sf) in different volume fraction of fibers (10%, 15% and 20%) was studied under dry sliding conditions. The Taguchi approach to experimental design was used to identify those testing parameters that have the largest effects on wear loss and coefficient of friction of the composites. Sliding distance was found to be the prominent parameter affecting wear loss; applied load affected coefficient of friction most significantly. The results of Taguchi analysis indicate that wear loss increases with increasing load and sliding distance, but it is reduced with increasing sliding speed. Coefficient of friction decreases with increasing applied load and sliding speed whereas it increases with increasing sliding distance. The composites with 10 vol.% and 15 vol.% of fiber had the lowest wear loss and friction because of the mixture effect of GNFs and Al₂O_3sf. However, due to the effect of agglomerated GNFs, there was an increase in wear loss and friction at 20 vol.%.