Lowest Specific Wear Rate Research Articles

Tribological Property Investigation of Self-Lubricating Molybdenum-Based Zirconia Ceramic Composite Operational at Elevated Temperature

Abstract Three mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) with 0.5 wt% of magnesium oxide (MgO) and 6 wt% of molybdenum (Mo) were prepared by the pressureless sintering process, and the friction and wear behavior of the ceramic composite were studied against the alumina disc. Tribological tests were carried out both at room temperature as well as at an elevated temperature (500 °C). The result revealed that a substantial reduction of ∼50% in the friction coefficient and ∼31% reduction in the wear rate were achieved while 6 wt% Mo was added into the 3Y-TZP matrix operational at 500 °C. No significant tribological influence was observed with the addition of Mo at the normal operating temperature. The minimum coefficient of friction and low specific wear rate were achieved because of the formation of MoO3 in between the mating surfaces at elevated temperature. The worn surfaces were characterized by means of field emission scanning electron microscopy (FESEM). The formation of MoO3 phases was identified by wear debris analysis which was performed with the help of X-ray photoelectron spectroscopy (XPS).

Friction and Wear Behavior of Polyimide Composites Reinforced by Surface-Modified Poly-p-Phenylenebenzobisoxazole (PBO) Fibers in High Ambient Temperatures.

(1) In order to improve the properties of antifriction and wear resistance of polyimide (PI) composite under high temperature conditions, (2) 3-Aminopropyltriethoxysilane (APTES) and Lanthanum (La) salt modifications were employed to manufacture poly-p-phenylenebenzobisoxazole (PBO)/PI composites with different interface properties. The representative ambient temperatures of 130 and 260 °C were chosen to study the friction and wear behavior of composites with different interface properties. (3) Results revealed that while both modification methods can improve the chemical activity of the surface of PBO fibers, the La salt modification is more effective. The friction coefficient of all composites decreases with the increase of sliding velocity and load at two temperatures, and the specific wear rate is increases. Contrary to the situation in the 130 °C environment, the wear resistance of the unmodified composite in the 260 °C environment is greatly affected by the sliding velocity and load, while the modified composites are less affected. Under the same test parameters, the PBO–La/PI composite has the lowest specific wear rate and friction coefficient, and (4) La salt modification is a more effective approach to improve the properties of antifriction and wear resistance of PI composite than APTES modification in high ambient temperatures.

Atomic Layer-Deposited Al2O3 Interlayer for Improved Tribological and Anti-corrosion Properties of TiN Hard Coating on 316L Stainless Steel

A dense Al2O3 interlayer was inserted into TiN to enhance the tribological and anti-corrosion properties of TiN hard coating via a hybrid process of magnetron sputtering and atomic layer deposition (ALD). The influence of the ALD-Al2O3 layer on the microstructure, mechanical, tribological and anti-corrosion properties of TiN was examined. The TiN-Al2O3 coating exhibits low friction coefficient and specific wear rate, due to the structure change and columnar refinement caused by the addition of amorphous ALD-Al2O3 interlay which improves the mechanical properties of hard coating. The improved corrosion properties of TiN are attributed to the fact that the insulating ALD-Al2O3 used as a sealing layer can prevent the corrosive chlorine ions migrating into the lower TiN layer and block the charge transport in coatings. Moreover, raising the insertion position of ALD-Al2O3 layer away from the steel substrate results in a further increase in the anti-corrosion property of TiN-Al2O3 composite coating.

Correlation between crystal structure and mechanical performance of Cr-implanted 300M high-strength steel using X-ray diffraction method

In order to study the influence of crystal structure change due to implantation dose on the hardness and wear performance of 300M high-strength steel, samples were surface modified by Cr implantation with dosages of 5.0 × 1016, 1.5 × 1017 and 3.0 × 1017 ions/cm2. X-ray diffraction method, which was already applied in studies on the microstructure of deformed and heat-treated materials, was used to study the crystal structure of the implanted steel, and the results were corrected with the hardness and wear performance. The solid solution strengthening effect and microstructure vary with increase in implantation dose. Owing to strong solid solution hardening of Cr, small average crystallite size and high dislocation density, the hardness and wear resistance of implanted steel with dose of 5.0 × 1016 ions/cm2 were found to be the highest compared with other samples. Moreover, although the crystallite size of the implanted sample with dose of 3 × 1017 ions/cm2 was similar to that of substrate and the dislocation density was lower than that of the substrate, its higher hardness and lower specific wear rate were due to the solid solution hardening and perhaps Cr clusters reinforcement.

Effect of SiC nanoparticles on the wear behaviour of squeeze-cast AZ91–2.0Ca–0.3Sb alloy

ABSTRACTThe dry sliding wear behaviour of the AZ91–2.0Ca–0.3Sb alloy and the AZ91–2.0Ca–0.3Sb–xSiCnp nanocomposites have been investigated. The wear rate is lower for all the nanocomposites compared to the alloy. All the nanocomposites demonstrate the lower specific wear rates than the alloy. Among the nanocomposites, the one containing 2.0SiCnp exhibits the best tribological performance. The values of the coefficient of friction are lower for the nanocomposites than the alloy. The abrasion, adhesion, oxidation, and delamination are the dominant wear mechanisms. The 3D topography depicts that the addition of SiCnp to the AZ91–2Ca–0.3Sb alloy results in the reduced surface roughness during the wear tests, confirming the superior wear behaviour of the nanocomposites compared to the alloy.

Diamond-like carbon coatings deposited by deep oscillation magnetron sputtering in Ar-Ne discharges

In a previous work, the authors have shown that a recently developed variant of high power impulse magnetron sputtering (HiPIMS), called deep oscillation magnetron sputtering (DOMS), was suitable for the deposition of hard hydrogen-free DLC films with tribological properties comparable to DLC films deposited by other state of the art deposition processes. Adding Ne to the discharge gas has been shown to be an effective method to increase the ionization fraction of the sputtered carbon species in an HiPIMS discharge. In this work, the effect of adding Ne to the discharge gas on the film growth processes and on the tribological performance of the films.On the overall, the substitution of Ar by Ne in the discharge gas up to 50% results in a progressive transformation of the dense columnar microstructure obtained in pure Ar into a featureless one. On the other hand, the hardness of the films increases from 14 to 22 GPa while a progressive increase of the sp3 content of the films is detected by Raman spectroscopy. The addition of Ne to the discharge gas results in much lower specific wear rates, reaching a minimum value of 4 × 10−17 m3/Nm, without any significant increase of the films residual stresses. Moreover, the higher wear resistance of the Ne films is achieved with only a small increase of the coefficient of friction, which remains close to 0.15, i.e., within the range of typical values for DLC films tested in relatively humid conditions. Thus the tribological properties of the DLC films deposited in this work are already interesting for application in the automotive industry, such as for the replacement of the CrN coatings nowadays standardly deposited onto the piston rings of internal combustion engines.

Concentrated solar energy for in-situ elaboration of wear-resistant composite layers. Part I: TiC and chromium carbide surface enrichment of common steels

Having already demonstrated the feasibility of using Concentrated Solar Energy (CSE) as a high temperature heat source for the in-situ elaboration of composite surface layers onto steel base metal, the present study focuses on the comparative evaluation of such “solar” titanium and chromium carbide hardfacings with respect to their microstructure characteristics and tribological performance. TiC and Cr3C2 powders were pre-deposited onto common steel base metal and the effects of solar irradiation time and repetition of solar exposure on the obtained microstructure of the surface layer were used as criteria for determining an adequate solar processing path for each specific carbide type. In the case of TiC powder, a single-step solar processing was sufficient to induce homogeneous dispersion of the carbide particles and, hence, surface reinforcement. For the Cr3C2 powder, single-step solar processing above a certain threshold solar processing time period was found to be necessary for the complete incorporation of the chromium carbide within the liquid metal pool, resulting in, however, carbides dissolution and surface alloying rather than carbides dispersion within the ferrous matrix. Thus, a second step of solar exposure of the previously obtained surface alloy above temperatures sufficient to cause re-melting, is necessary to obtain primary chromium carbide precipitates that provide the high wear resistance required. This was, indeed, demonstrated via dry sliding friction tests performed against an Al2O3 ball during which both “solar” surface layers exhibited relatively low specific wear rates. Microscopic observations on the worn surfaces indicated the synergy of distinct wear micro-mechanisms, different for each carbide particle type dispersed in the metallic matrix. These results in combination with the respective ones for WC-based hardfacing layers obtained via the same route and reported in the second part of this study, assist to identify the crucial metallurgical reactions that govern the successful implementation of the proposed “solar” technology.

Influence of Artificial Aging on Mechanical Properties and High Stress Abrasive Wear Behaviour of Al–Mg–Si Alloy

The present study evaluated hardness, tensile properties and two-body abrasive wear behaviour of Al–Mg–Si alloy specimens artificially aged at 448 K for different durations ranging from 0.5 to 504 h. In addition to the measurements of Vickers hardness and tensile properties, wear tests of differently aged alloys were conducted against SiC abrasive paper of 220 grit size under normal load of 9.81 N with the help of a pin-on-disc tribometer. Abrasive wear characteristics were assessed in terms of measurements of specific wear rate and roughness of the abraded surfaces. These were substantiated via examinations of worn surfaces, collected wear debris and subsurfaces of worn specimens to comprehend the micro-mechanisms of abrasion. The abrasive wear performance varied significantly with the duration of artificial aging and the lowest specific wear rate as well as roughness of the abraded surfaces corresponded to the peak-aged condition. An attempt was also made to correlate mechanical properties and tribological performance. It was found that the specific wear rate exhibited direct linear relation with the strain hardening exponent, and inverse linear relationships with hardness, yield strength and strength coefficient. Microplowing, microcutting and microcracking were identified as mechanisms of abrasion; the extents of these processes were found to be governed by the state of aging that determined the mechanical properties.

Application of HVOF WC-Co-Cr coatings on the internal surface of small cylinders: Effect of internal diameter on the wear resistance

Due to the restrictions and mediocre performance of current methods of coating complex shaped parts in which line of sight processes currently struggle, the development of new coating methods is essential, with High Velocity Oxy-Fuel (HVOF) thermal spray coatings being a good candidate. In this study, a new compact High Velocity Oxy-Air Fuel (HVOAF) thermal spray torch designed to coat internal surfaces was traversed within cylindrical pipes of internal diameters (IDs) of 70 mm, 90 mm and 110 mm and a WC-10Co-4Cr coating was applied with a commercially available powder feedstock. Powder and coating microstructures were analysed using SEM/EDX and XRD. Fracture toughness and microhardness of the coatings were measured, and dry sliding wear performance was investigated at two loads: 96 and 240 N. It was found that the coating sprayed at 90 mm (medium ID) had a lower specific wear rates at both test loads due to the highest fracture toughness and microhardness; whereas, the coating sprayed at 110 mm (high ID) showed the highest specific wear rates at both low and high conditions due to poor fracture toughness.

Cu, Cu-SiC functionally graded coating for protection against corrosion and wear

This work presents the performance of the Copper (Cu) based functionally graded coatings (FGCs) when subjected to corrosion in the 3.5 wt% NaCl aqueous solution and sliding wear under the different loads (2, 5, 8 and 10 N). The Cu FGC, with three layers of Cu (each 20 μm thick), has a gradual decrement in the crystallite size from bottom to the top surface. The Cu, Cu-SiC FGC consists of three-layered Cu FGC (each Cu layer 12 μm thick) followed by two layers of Cu-SiC nanocomposite (each 12 μm thick) with a steep increase in the amount of reinforced SiC nanoparticles from 2 to 7 vol% towards the top. A comparison is made among the equally thick (60 μm) electrodeposited FGCs, i.e., Cu FGC and Cu, Cu-SiC FGC, single-layered Cu coating with the finest microstructure (smallest crystallite size) and Cu-SiC nanocomposite coating with 7 vol% SiC. A drastic reduction in the corrosion and wear rate is observed in the Cu and Cu, Cu-SiC FGCs when compared with the same of single-layered Cu and Cu-SiC nanocomposite coatings, respectively. It is also observed that the Cu, Cu-SiC FGC has higher corrosion resistance than the Cu FGC. The Cu, Cu-SiC FGC is found to be more wear resistant than the Cu FGC at high load, while the latter shows lower specific wear rate at low loads.

Hybrid three-dimensional graphene fillers and graphite platelets to improve the thermal conductivity and wear performance of epoxy composites

Based on our recent work on the three-dimensional graphene fillers (3DGF) reinforced epoxy (EP) composite, here commercially available graphite platelets (GP) were incorporated together with 3DGF to modify EP in order to further improve the thermal conduction and wear resistance of the EP composites. Remarkably, only 0.14 vol% 3DGF was needed to enhance the thermal conduction of EP by 170%, in contrast with the fact that 37 times content of graphite fillers were required to achieve almost the same enhancement. Moreover, in the presence of both 5.38 vol% GP and 0.14 vol% 3DGF, the thermal conductivity of EP was further enhanced by 258%. Meanwhile, the tribological test results revealed the advantage of 3DGF over GP. The ternary EP composite modified with both 0.28 vol% of 3DGF and 5.38 vol% GP had much lower specific wear rate and coefficient of friction than those binary composites with either 3DGF or GP.

Effect of nanorelief structure formed in situ on tribological properties of ceramics in dry sliding

Abstract Nanorelief structure formed on the surface of B4C–SiC ceramics by an in-situ method is reported. The nanorelief structure formed by the in-situ method, which differs from the relief structure produced by laser treatment, results from preferential wearing of SiC particles, which have lower hardness, by free diamond particles and mixed wear particles of B4C and SiC during polishing and sliding, respectively. The effect of the nanorelief structure formed by the in-situ method on the sliding dry friction against a SiC ball is examined using a pin-on-disk tribometer. A comparison of dry sliding of the B4C–SiC composite ceramics with nanorelief structure to that of SiC ceramics without nanorelief structure reveals that B4C–SiC composite ceramics have a lower coefficient of friction and a significantly lower specific wear rate than the SiC ceramics. Worn surface analysis indicates that the nanorelief structure does not disappear after a dry sliding test. The depth of the nanorelief structure formed by the in-situ method ranges from 10 to 40 nm. The friction and wear results are associated with the nanorelief structure formed by the in-situ method.

The wear resistance improvement of fibre reinforced polymer composite gears

This paper presents experimental investigations into the wear performance of non-reinforced POM (Polyoxymethylene) and 28% GFR POM (glass fibre reinforced POM) gear pairs; polymer running against polymer is a little studied but important system. All the gears were manufactured locally by injection moulding. The injection mould design and manufacturing process are briefly described and progress in the control of injection moulding processes for polymer and fibre reinforced polymer gears is discussed. A specifically designed polymer composite gear test rig was used for this research. Performance differences for the POM and GFR POM gears are observed, notably their loading capacity and failure modes. Both POM and GFR POM gear pairs, showed a clear wear transition torque for a given running speed. Above the transition torque the wear rate accelerated rapidly causing thermal failure, while below the transition torque the gears had a very low specific wear rate. Significant performance enhancements were seen for the GFR POM gears, with an increase of around 50% in load carrying capacity when compared to the non-reinforced POM gears. The wear mechanisms are briefly discussed, noting that most data available for polymer gear design is not representative of these polymer against polymer pairings.

On the significant enhancement in the performance properties of PAEK composite by inclusion of a small amount of nano-mica particles

Abstract The paper reports on the comparative potential of nano-particles and micro-particles of mica in glass fiber reinforced Polyaryletherketone (PAEK) composite containing graphite (10 wt%). Very high PVlimit value (>100 MPa-m/s), very low specific wear rate (K0) (2–∼8 × 10−16 m3/Nm) along with very low friction coefficient (μ) (0.04–0.08), were exhibited by the composites. The PVlimit values of a nano-composite (NC) and micro-composite were 126 and 84 MPa m/s respectively. Friction and wear performance of a nono-composite was significantly better at lower PV conditions (40% lower in wear rate and 20% in friction). Worn surfaces were studied by scanning electron microscopy (SEM) and 3D profilometer, while the interaction of the constituents with a disc surface was investigated with the X-ray photoelectron spectroscopy (XPS).

Experimental research on tribological properties of liquid phase exfoliated graphene as an additive in SAE 10W-30 lubricating oil

Abstract In this study, the graphene was prepared by liquid phase exfoliation method, and then through microfluidization technique it was uniformly dispersed into SAE 10W-30 lubricating oil. The lubricating oils without graphene and with four different graphene concentrations were tested twice respectively on a pin-on-disc tribometer under high specific pressure of 10 MPa and low linear velocity of 0.3 m/s. After testing, the scratches on discs were observed by scanning electron microscope (SEM) and three-dimensional (3D) surface metrology system. The oil with 0.05 wt% graphene exhibited the minimum friction coefficient, lowest specific wear rate and slightest scratch. The results illustrated that the graphene dispersed into SAE 10W-30 oil with optimum concentration improved the anti-friction and anti-wear performances.

Tribological performance of graphite-like carbon films with varied thickness

Graphite-like carbon (GLC) films with different thickness were deposited on 316 L stainless steel using closed field unbalanced magnetron sputtering system to investigate the influence of film thickness on the microstructure, mechanical and tribological properties. The results showed that the surface of the deposited films exhibited granular-like morphology, and the sp2 content, surface roughness increase with the increase of film thickness, leading to the lower of hardness and higher of the internal stress. Both of the friction curves obtained by nano-tribological tests and fretting wear experiments revealed a three-stage evolution tendency with the same wear mechanism for the first two stages. The intermediate thick GLC film had the lowest specific wear rate, whilst the fretting fatigue life increased with film thickness.

Effect of counter-face material on the tribological characteristics of UHMW polyethylene under synovial fluid lubrication

Abstract UHMW polyethylene is widely used for cartilage replacement in joint Arthroplasty. This study is focused on the tribological characteristics of UHMW polyethylene against biomedical grade 316L SS and TiAl6V4 counter-face materials under Synovial fluid lubrication. The Friction Co-efficient and wear rate of the UHMWPE was obtained from the tribological tests performed on the recipro-cating tri-bometer. Lower Friction Co-efficient and specific wear rate was achieved for UHMWPE against TiAl6V4 counter-face material than 316L SS under Synovial fluid lubrication. From the in-vitro tribological tests, it was demonstrated that the UHMWPE/TiAl6V4 is a good tribo-pair for artificial joints.

Experimental analysis of tensile, flexural, and tribological properties of walnut shell powder/polyester composites

Polyester composite specimens with varying wt% of walnut shell powder (WSP) were prepared and characterized for their mechanical and tribological properties. The results of mechanical testing showed that the specific tensile modulus increased with an increase in WSP wt%, whereas the specific flexural modulus slightly decreased at 30 wt%. However, the specific tensile and flexural strength of neat polyester specimen were found to be more than the doped specimens. The specific tensile strength decreased with an increase in WSP wt%, whereas the flexural strength substantially varied with wt%. The tribo-properties were investigated using a wear and friction-monitoring apparatus. It was found from the tribo study that the doped specimens offered higher wear resistance than the neat polyester specimen at all the sliding conditions. The friction coefficient of the doped specimens also remained higher than the neat polyester specimen at most of the sliding conditions. Based on these favorable properties, i.e., increased stiffness, lower specific wear rate, and higher friction coefficient, the WSP can be used as a potential bio-filler in friction composites where such properties are highly desirable.

Sliding wear characteristics of as-deposited and heat-treated electroless Ni-P coatings against AISI E52100 steel ball

In the present experimental study, the wear characteristics of as-deposited and heat-treated, nickel phosphorus (Ni-P) coatings were studied against bearing steel ball (AISI E52100) at ambient dry conditions using linear reciprocating tribometer. The Ni-P coatings were deposited on En24 grade steel using electroless acidic bath and subjected to heat treatment at 400 °C for 1 h under air atmosphere. The phase structure and surface morphology of the coatings were characterized using x-ray diffraction (XRD) analysis and scanning electron microscopy (SEM), respectively. Grain size of the coatings was analysed using Scherrer technique. Heat-treated coatings showed 50% improvement in Vickers hardness compared to as-deposited coatings, which is attributed to the formation of Ni3P phase. The stable friction coefficient (∼0.21) and low specific wear rate (4.49E-05 mm3/N-m) were observed for heat-treated coatings in comparison to those of as-deposited coatings. Wear tracks were characterized using SEM and energy dispersive spectroscopy (EDS) in order to understand the wear mechanisms.

Design of Fe-Based Bulk Metallic Glasses with Improved Wear Resistance.

The application of bulk metallic glasses (BMGs) as advanced wear-resistant materials has remained limited despite optimistic expectations. In this work, we develop a series of novel Fe-based BMGs with improved wear resistance by altering the Cr and Mo contents in an Fe-Cr-Mo-C-B-Y glass-forming system. Experimental results demonstrate that increasing Cr and Mo contents enhance the thermal stability and hardness ( Hv) of the resulting BMGs without reducing their fracture toughness ( Kc). The enhanced hardness is mainly attributed to the increased fraction of the stiff (Cr,Mo)-C covalent bonds in the resultant BMGs, as revealed by X-ray photoelectron spectrograph measurement. Worn surface/subsurface observations and stress field modeling reveal the activity of two kinds of wear mechanisms, i.e., hardness-controlled abrasion wear and toughness-controlled fatigue wear. We further clarify the enhanced wear performance of the Fe-based BMGs according to an effective indicator Kc3/4 Hv1/2 that correlates positively with the wear resistance of the samples. The optimal Fe-based BMG sample possessed versatile properties, including a strong glass-forming ability (i.e., a critical diameter of 8 mm), a high hardness of 1335 Hv, and a very low specific wear rate of ∼1.3 × 10-6 mm3 N-1 m-1, which represents one of the most outstanding Fe-based BMGs reported thus far.