Microstructures Of Worn Surfaces Research Articles

A research on the electrical sliding behavior wear of dual-scale particulate reinforced copper matrix composites

This work aims to investigate the electrical sliding wear behavior of the dual-scale particulate reinforced copper matrix composites by a self-developed pin-on-disk wear tester. Cu-xCr-0.3Zr-1ZrB2 (x = 0, 0.5, 1.0) composites were fabricating by casting and cold rolling. The microstructure of worn surfaces was examined using scanning electron microscopy (SEM) and laser scanning confocal microscope to unravel the wear mechanisms. The results indicated that the combined effect of mechanical wear and electrical wear dominated the wear process with an increase in the apparent normal load. Amplifying the electrical current increased the wear loss of the sliding pair, in the meantime alleviated the fluctuation of the friction coefficient with marginal changes in the average values. After introducing Cr element and ZrB2 particles, the wear rate decreased from 0.197 mg/m to 0.141 mg/m under moderate operating test conditions. Adhesive wear and abrasive wear occupied an important position in the wear mechanism of the Cu-1wt%Cr-0.3wt%Zr-1wt%ZrB2 composite under electrical current due to the elevation of thermal stability and the formation of a tribolayer introduced by these reinforcements.

Effect of TiC nanoparticles on microstructural and tribological properties of Cu-TiC nano-composites

The present study has investigated the role of the addition of TiC nanoparticles on the microstructural, mechanical, physical, and metallurgical properties of the Cu-TiC nanocomposites. A Powder metallurgy route was used to fabricate the samples. Cold compaction of powders was done at 480 MPa which was followed by sintering at 950°C. Wt.% of TiC was varied from 0% to 20%. A Pin-On-Disc tribometer was used to carry out the wear and friction tests. SEM and EDS techniques were used to explicate the morphology and microstructures of worn surfaces and to comprehend the underlying wear mechanism. The fabricated samples were investigated against the applied normal load (10, 20, and 30 N), sliding speed (0.5, 1.0, and 1.5 m/s), and sliding distance (900, 1800, and 2700 m). The results revealed that the Hardness and tensile strength were improved by 88.76% and 37.26% respectively due to the addition of TiC and were maximum for Cu-20%TiC while the relative density shows the reverse trend. Further, it was found that wear resistance and coefficient of friction were improved by 87.18% and 51.85% respectively as a function of nano-TiC content. The presence of oxide layers and mechanically mixed layers are detected from worn surface analysis which modulates the tribological behavior of the contact.

Influence of Graphite/Graphene on the Tribological Behaviors of Self-Lubricating Fabric Composite.

Graphite/graphene particles were employed as functional fillers to modify hybrid polytetrafluoroethylene/polyisophthaloyl metaphenylene diamine (PTFE/Nomex) fabric-reinforced phenolic composites. The tribology behavior was investigated using a ball-on-disk wear tester, together with a 3D digital microscope. The graphite/graphene exhibits the synergetic effect from the results, which not only reduces the friction efficient but also improves the wear resistance of the composites. Moreover, the wear mechanisms were studied by the wear surface microstructure analysis. It is proposed that the synergetic effect includes mainly the positive rolling effect from the graphene and an improved load-carrying capacity brought by graphite. In addition, in order to obtain the optimized formulation to satisfy the bearing application, the influence of graphite and graphene content on the tribological property of the composites was studied in detail. On the basis of that, the application research was carried out on the bearing oscillating wear test, which will evaluate the engineering service life of the composite.

Role of Calcium Carbonate(CaCO3) in improving wear resistance of Polypropylene(PP) components used in automobiles

Abstract Compounds of Polypropylene (PP) will continue to play as an important materials for automotive applications because of its good mechanical properties including mold ability combined with excellent appearance, colorability ,environmental suitability and high performance at low cost. PP compounds are used in automotive interior parts, instrumental panels, door panels, pillars, Loading platform for light pick-up trucks, battery boxes, indoor carpets. These parts easily porn to wear because of its frequent usage. In this work calcium carbonate(CaCO3) has been blended with PP in different proportions using twin screw extruder machine and tested it in Pin-on-Disc machine for varying load, speed and sliding distance to study its wear characteristics. The wear phenomenon has been investigated and discussed based on wear loss of the material and microstructure of worn surfaces.

Effect of mechanical vibrations on the wear behavior of AZ91 Mg alloy

AZ91 Mg alloy is the most promising alloy used for structural applications. The vibration induced methods are effective and economic viable in term of mechanical properties. Sliding wear tests were performed on AZ91 Mg alloy using a pin-on- disc configuration. Wear rates were measured at 5 N and 10N at a sliding velocity of 1m/s for varied frequency within the range of 5- 25Hz and a constant amplitude of 2mm. Microstructures of worn surfaces and wear debris were characterized by field emission scanning electron microscopy (FESEM). It is observed that wear resistance of vibrated AZ91 alloy at 15Hz frequency ad 2mm amplitude was superior than cast AZ91 Mg alloy. Finer grain size and equiaxed grain shape both are important parameters for better wear resistance in vibrated AZ91 Mg alloys. FESEM analysis revealed that wear is considerably affected due to frictional heat generated by the relative motion between AZ91 Mg alloy and EN31 steel surface. No single mechanism was responsible for material loss.

Dry Sliding Wear Behavior of Ti-6Al-4V Alloy

Titanium and its alloys exhibit a unique combination of physical and corrosion resistance properties which make them ideal materials for space flight engine component such as disks and blades of compressor, marine applications, chemical industries and many bio medical applications. However the use of these materials is limited due to its poor tribological properties. Dry sliding wear tests were performed on Ti-6Al-4V using a pin-on-disc (EN31 steel) configuration. Wear rates were measured with different load and sliding velocity at a constant sliding distance. Microstructures of worn surfaces were characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).

The Effects of Counterparts on the Wear Properties and Surface Microstructure of TC4 Alloy

The wear properties and wear surfaces microstructure of TC4 alloy were studied with GCr15 and SiC counterparts, respectively. The results show that the friction coefficients of TC4 alloy with GCr15 was higher and the mass loss was lower compared with those of SiC. The wear mechanisms of TC4 alloy with GCr15 and SiC could be concluded as grinding abrasion, adhesion abrasion and oxidation abrasion. However, adhesion abrasion and oxidation abrasion mechanisms were predominant with GCr15 counterpart.

Investigation of abrasion in Al–MgO metal matrix composites

In this study, the effects of reinforcement volume fractions on abrasive wear behavior were examined in Al–MgO reinforced metal matrix composites of 5%, 10% and 15% reinforcement – volume ratios produced by melt-stirring. Abrasive wear tests were carried out by 60, 80 and 100 mesh sized Al2O3 abrasive papers and pin-on-disc wear test apparatus under 10, 20 and 30N loads at 0.2m/s sliding speed. The mechanical properties such as hardness and fracture strength were determined. Subsequent to the wear tests, the microstructures of worn surfaces were examined by scanning electron microscope analyses. While increased MgO reinforcement volume fraction in the composite resulted increased hardness, fracture strength was determined to decrease. Additionally, it was found that increased MgO reinforcement volume fraction in the composite was accompanied with increased wear loss and porosity as well as reinforcement – volume ratio was identified to be significant determinants of abrasive wear behavior.

Microstructure and tribological properties of REs borided TC21 alloy

The hard titanium boride layers are produced on titanium alloy TC21 using rare earth (RE) additions boriding technique. The microstructural evolution and phase transformations of the boride layers are examined using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy and X-ray diffraction. Moreover, the friction and wear behaviour of boride layers under dry sliding conditions are evaluated using an HT-1000 friction and wear tester, and the microstructures of worn surfaces are also characterised by SEM. The results show that the boron concentrations in the surface layer during surface boriding have been improved with a small amount of RE additions, coupled with enhanced surface hardness and coating layer thickness. Moreover, all of the borided alloys appear to have better wear resistance and lower friction coefficient than as received alloy; furthermore, the RE borided samples show higher hardness and better wear resistance than conventional one, without RE additions.

Influence of Martensite Phase on the Tribological Properties of Plain Carbon Steel

In the present paper wear behaviour of plain carbon steel having martensite phase under dry sliding condition has been investigated. Plain carbon steel material BS 970/ En 42 in the form of rods were selected to produce heat treated wear test pin specimens. Compositions, morphologies and microstructures of worn surfaces were characterized by scanning electron microscope (SEM), and energy dispersive spectroscopy analysis (EDS). Volumetric wear rate was investigated for these pins on pin on disc wear testing machine. Volumetric wear rate of martensite phase is more under low speed for all the normal pressure conditions. Wear behaviour was studied at different combinations of sliding speeds and the normal pressures with respect to the volumetric wear rate. Also the effect of parameters such as friction force and coefficient of friction on volumetric wear rate under the prevailing sliding speed and normal pressure condition was also studied.

The effect of the addition of aramid fibers on tribological properties of the polyimide after ultraviolet or atomic oxygen irradiation

The aramid fibers reinforced polyimide composites were fabricated by means of a hot-press molding technique. The mechanical and tribological behaviors of the reinforced composites were studied. The friction and wear properties of the composites, rotating against a GCr15 steel ball, were investigated on a ball-on-disc test rig. To contrast the effects of the ultraviolet radiation and atomic oxygen, experiments without radiation or after ultraviolet or atomic oxygen radiation were conducted. Experimental results revealed that 20% aramid fiber reinforced polyimide exhibited higher modulus. However, the coefficient of friction decreased with the increase of the aramid fiber content. The composites had a lower wear rate value after atomic oxygen radiation. Microstructure of worn surface of the tested composites was inspected by scanning electron microscopy, and X-ray photoelectron spectroscopy study of the composite surface showed that the chemical composition of the surface changed after ultraviolet or atomic oxygen radiation because of the oxidation.

Mechanical and Tribological Properties of Phenol Formaldehyde Resin Reinforced with Nano-Silica

Reinforced phenol formaldehyde resin (PF) matrix nanocomposites with different nano-SiO2 were fabricated with two-roll compounding and compression molding technology. The mechanical and tribological behaviors of the reinforced composites were studied. The friction and wear experiments were tested on a constant speed machine (D-SM). The impact and flexural strength of nanocomposites were increased by the addition of various types of SiO2, but the flexural modulus was decreased. The effects of the addition of various types of SiO2 on tribological properties of the composites were explored in this study. The results showed that the coefficient of friction of the composites increased, while the wear rate values decreased at various temperatures. Microstructure of worn surface of the tested composites was observed by scanning electronic microscope (SEM) and the wear mechanism of the reinforced composites was studied.

A comparative study of the wear behavior of as-cast and hot extruded ZE41A magnesium alloy

Dry sliding wear tests were performed on as-cast and hot extruded ZE41A magnesium alloy using pin-on-disc (EN32 steel) configuration. Wear rates were measured in an applied load range of 30–150 N, sliding velocity range of 0.5–2.5 m/s and at a constant sliding distance of 1500 m. Microstructures of worn surfaces were characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Wear maps were drawn. The dominant wear mechanisms in each wear regime were identified and classified in wear mechanism maps. Extruded alloy showed better wear resistance and exhibited good tribological properties than as-cast alloy due to grain refinement, decrease in porosity, strengthening and hardening of the material.

Dry sliding wear behavior of hot extruded ZE41A magnesium alloy

Dry sliding wear tests were performed on a hot extruded ZE41A magnesium alloy using a pin-on-disc (EN32 steel) configuration. Wear rates were measured in a load range of 30–150 N, sliding velocity range of 0.5–2.5 m/s at a constant sliding distance of 1500 m. Microstructures of worn surfaces were characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Wear maps were drawn. An empirical wear transition map has been constructed to delineate the conditions under which severe wear and ultra severe wear initiated. The dominant wear mechanisms in each wear regime were identified and classified in a wear mechanism map.

Wear behaviour of nanostructured and conventional 8 wt-%Y2O3–ZrO2 coatings against Si3N4 ball

The aim of the present paper is to investigate and compare the wear and tribological behaviour of two types of yttria–partially stabilised zirconia coatings, i.e.nanostructured and conventional zirconia. The coatings, 8 wt-%Y2O3–ZrO2, were produced using an air plasma spraying (APS) technique. Substrates used were made from AISI 304 stainless steel. To perform the wear tests, a pin on disc wear testing machine, using a 10 mm silicon nitride (Si3N4) ball as the pin, was employed. Coatings produced were characterised before and after being subjected to wear testing, using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray diffraction. Regarding the wear tests, effects of various parameters, such as wear distance, substrate temperature, disc rotating speed (sliding velocity) and applied normal load, were investigated. Results obtained (weight loss, wear rate, coefficient of friction and worn surface microstructure) revealed that under the wear conditions applied, the nanostructured zirconia coating exhibited a better wear resistance and tribological properties than the conventional one. Also it was observed that the difference in wear resistance between both coatings tested is a function of wear testing parameters such as wear distance, substrate temperature, disc rotating speed and applied normal load.

Sliding wear transition for the CW614 brass alloy

Dry sliding wear tests were performed on a CW614 brass alloy using a pin-on-ring configuration. Wear kinetics were measured within a load range of 20–80 N and sliding velocity ranging from 1 to 7 m/s. Chemical compositions, morphologies and microstructures of worn surfaces and wear debris were characterised by scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS). Two main wear regimes have been observed: severe wear and mild wear. The results of wear tests and metallographic investigations on worn surfaces have been summarised in a wear mechanism map. It was found that the wear transition is controlled by a critical temperature at the contact surface.

Sliding wear map for the magnesium alloy Mg-9Al-0.9 Zn (AZ91)

Dry sliding wear tests were performed on a Mg-9.0%, Al-0.9%, Zn (AZ91) alloy using a block on-ring (AISI 52100 steel) configuration. Wear rates were measured within a load range of 1–350 N and a sliding velocity range of 0.1–2.0 m/s Compositions, morphologies and microstructures of worn surfaces and wear debris were characterised by scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and X-ray diffractometer (XRD). A wear mapping approach, consisting of identification of micromechanisms of wear leading to the generation of loose debris and surface damage and determination of the range of applicability of each mechanism as a function of load and speed, has been adopted. Two main wear regimes, namely a mild wear regime and a severe wear regime have been observed. The role of contact surface temperature on the mild to severe wear transition was investigated in detail. It was shown that the transition from mild to severe wear was controlled by the contact surface temperature of the alloy and that the onset of the severe wear coincided with a surface temperature of 347 K. In the mild wear regime two different micromechanisms operated, i.e. two sub-wear regimes, namely an oxidational wear regime and a delamination wear regime, were identified. Similarly, in the severe wear regime two different wear mechanisms were responsible for surface damage and debris formation. These were classified as the severe plastic deformation induced wear and the melt wear regimes. The results of wear tests and metallographic investigations on worn surfaces have been summarised in a wear mechanism map. An empirical contact surface temperature model, which serves to predict the critical surface temperature at the onset of severe wear, has been developed.

On the wear of short carbon fiber reinforced carbon matrix composite

AbstractThe wear rate and friction coefficient of carbon–carbon composites have been investigated as a function of sliding velocity. Wear and friction models derived for fibrous polymer composites appear to be applicable for this carbon–carbon composite system. The microstructure of worn surfaces has been examined and correlated with the wear mechanism.