Wear Response Research Articles

Corrosion and Wear Behaviour of Spark Plasma-Sintered NiCrCoAlTiW-Ta Superalloy

NiCrCoAlTiW-Ta superalloy was sintered using spark plasma sintering technique. The influence of starting powder particle size on the corrosion and dry sliding wear behaviour of sintered NiCrCoAlTiW-Ta superalloy was investigated. The nickel matrix (> 60 wt%) was varied over three different particle sizes (3–44, 45–106 and 106–150 µm). The powders were sintered at 1100 °C, heating rate of 100 °C/min and pressure of 32 MPa. The effect of particle sizes on sintered density, microhardness, corrosion and wear were reported. The results show that the sintered density of 97.48% and microhardness value of 382.88 HV0.1 were reported for the smallest starting powder. Furthermore, the microstructures of the sintered alloy revealed the presence of three major phases: γ, γ′ and the precipitated solid solution phase. There was an improvement in the corrosion response in relation to the particle size of the starting powder. This indicates that the least corrosive alloy has the least starting powder particle size. It has a corrosion rate of 0.047 and 0.056 mm/year in saline and acidic media, respectively. Also, the coefficient of friction increased with increase in powder particle size. However, the poor wear response of the alloys with bigger powder particle size could be attributed to poor adhesion of the oxide layer.

Wear and thermal stability of nano-TiB2 modified TiCN-WC-Co-Cr3C2 cermet

This work discusses the friction, wear and thermal response of TiCN-WC-Co-Cr3C2 cermet modified by the addition of TiB2 nanoparticles. The specimens were prepared by spark plasma sintering by adding different weight percentages (5, 10 and 15) of TiB2 nanoparticles in TiCN-WC-Co-Cr3C2 cermets. The sintered pieces were subjected to sliding wear under an unlubricated condition and a constant load of 20 N at sliding velocities of 0.23 m/s, 0.35 m/s and 0.47 m/s against a steel disc of 48 mm diameter. Friction was the maximum at a sliding velocity of 0.23 m/s. The wear loss decreased with increasing speed of sliding and was between 10−5 to 10−6 mm3. The wear rates and coefficient of friction were highly dependent on microstructure and mechanical properties of the cermets. Abrasion and adhesion were the active modes of wear. Heating of the samples was carried out at 600 °C, 800 °C and 1000 °C for 4 h. A substantial mass gain and decrease in hardness were observed in the specimen annealed at 1000 °C, for which Scanning Electron Microscopy revealed considerable grain growth and XRD showed oxide phases. A cermet containing 15% TiB2 nanoparticles displayed the lowest volumetric wear at room temperature, but had rather low thermal stability. Response surface methodology was used to develop models and regression equations for wear and thermal stability.

Temperature dependent two-body abrasive wear of polycarbonate surfaces

During the lifetime of polycarbonate surfaces, which for example are used as helmets or protective eye visors, friction and abrasive wear may result from scratching or sliding cycles. Previous research showed that it is essential to understand the intrinsic mechanical response of the polymer in order to further investigate its frictional and wear response. The Eindhoven Glassy Polymer (EGP) model is a 3D elasto-viscoplastic constitutive model, developed to describe the intrinsic mechanical response of polymer glasses. Temperature is a crucial player in the intrinsic response and also plays a pivotal role in the resulting frictional response as tested via a single-asperity scratch test. In the current study, a finite element model is used to investigate the effect of temperature on the frictional response of polycarbonate and detect the onset of crack formation and wear initiation. The results show that temperature has a strong effect on the intrinsic response of the polymer, i.e. drop in yield stress and altered strain-hardening and strain-softening response. However, it has a minute effect on its frictional response, the simulation model is able to capture this response quantitively. In addition, cracks are observed experimentally at elevated temperature. A critical positive hydrostatic stress value is selected as a criterion for crack formation. It has been shown that at elevated temperatures the value of the maximum positive hydrostatic stress increases due to the altered intrinsic response of the material on one hand, and the increased adhesion between the tip and the polymer on the other hand.

On the multi-parametric optimization of quality characteristics of the hybrid Al-6061 composites fabricated through powder metallurgy

Aluminium matrix composites (AMCs) have gained enormous attention of almost all types of manufacturing sectors owing to their excellent strength to weight ratio, ease of processing, good thermal conductivity, corrosion resistance, and desirable mechanical properties. Amongst the various processing routes available for AMCs, mechanical alloying assisted powder metallurgy (MA2PM) is particularly efficient in achieving the required physical, mechanical, and metallurgical characteristics. Therefore, in this present work, an effort has been made to develop the hybrid Al-6061 composites via MA2PM route under the influence of controllable and significant process variables. A specified proportion of graphite, silicon carbide (SiC), magnesium (Mg), zinc (Zn), and fly ash were selected and the process parameters (such as compaction pressure, sintering temperature, and sintering time) were varied as per Taguchi L9 orthogonal array. It has been found that the hardness and wear responses of the developed samples were significantly influenced by the processing parameters at 95% confidence level. Overall, the study conducted indicated that for hardness and wear rate only the compaction pressure found as significant parameter with 89.40 and 72.52% contribution.

Wear behavior of glass microballoon based closed cell foam

Present work deals with dry sliding wear response of hollow glass microballoons reinforced lightweight epoxy syntactic (closed cell) foams using a pin on disc apparatus. Influence of glass microballoons content on wear behavior of hollow glass microballoons/epoxy foams in dry sliding mode is investigated. Effects of sliding velocity (1 and 3 m s−1), normal load (30–50 N), sliding distance (1 and 3 km) and glass microballoons content (20, 40 and 60 volume%) are investigated. The rate of wear declines with increasing glass microballoons content and sliding distance. Syntactic foams with perfectly spherical glass microballoons exhibit enhanced resistance to wear as compared to neat resin samples due to better constituents compatibility. Specific wear rate shows noticeably decreasing magnitude with higher applied load. Decrease in frictional coefficient is observed with higher filler loadings. Lowest wear rate of 1.6 mm3 km−1 is noted for sliding velocity and load of 3 m s−1 and 50 N respectively with 60 filler volume %. Low wear values with higher glass microballoon loadings support the feasibility of utilizing such foams in wear-prone applications in weight sensitive structures. Wear mechanisms are studied using scanning electron microscopy. Finally, property map is presented to compare the observed wear results with the existing studies available on dry sliding wear response.

Optimization of SiC Concentration and Process Parameters for a Wear-Resistant UHMWPE Nancocomposite

Taguchi methodology was implemented to optimize and evaluate the effect of process parameters such as the applied pressure and time of holding on the tribological properties of ultra-high molecular weight polyethylene (UHMWPE) nanocomposite reinforced with different loadings of silicon carbide (SiC) nanoparticles. An L9 orthogonal array was used to design experimental matrix in terms of pressure, holding time, and the loading of SiC. UHMWPE/SiC nanocomposites were synthesized via ultrasonication and hot pressing. Pin on disk wear tests were carried out on the composites to evaluate the tribological properties such as specific wear rate and coefficient of friction. Friction and wear response were analyzed using analysis of variance and regression models. The effect of each parameter and optimal process parameters that result in minimum friction and specific wear rate were determined. The confirmation tests carried out verified the validity of the developed experimental design model.

Sliding wear performance of thermally sprayed Ni-Cr based alloy deposited on SAE 1045 steel

ABSTRACTThe present work has been carried out in order to investigate the sliding wear performance of a Ni-Cr based alloy, containing boron, carbon, silicon and iron, deposited onto a SAE 1045 steel substrate. The coatings were thermally sprayed by means of a High Velocity Oxy-Fuel system and post heat-treated for one hour at 760°C in an argon atmosphere. The relative sliding performance was evaluated under unlubricated dry conditions at different applied normal loads and sliding velocities, in order to analyze the influence of these parameters on the wear response. Test results are discussed and interpreted on the basis of both microstructural evaluations and mechanical properties measurements. The surface morphology and topography of the wear scars have been studied through of a Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) techniques. The results have shown an improved wear resistance of the coated steel samples as compared to the uncoated ones.

Effect of Poly(ε-Caprolactone) as a bio-lubricant additive in AISI 4140 Steel/Al2O3 tribosystem

ABSTRACTSince ancient times, lubricants have been used to reduce friction and wear problems of mechanical systems. However, nowadays, there is a constant effort to improve their performance through additives so that they can accomplish properly in this modern world. In that sense, in this study, it was proposed the use of Poly(ε-Caprolactone) (PCL) as a biodegradable additive in Castor oil. The effect that this additive has on the tribological properties of AISI 4140 steel/Al2O3 tribosystem was analyzed. For this purpose, PCL was dissolved in Castor oil at 65 °C for 15 minutes. Later, once the lubricant formulations got into room temperature, friction tests were conducted with a ball-on-disk configuration. Several experiments were systematically carried out in order to study the factors that could influence the performance of the tribological system, for instance: additive concentration, velocity, temperature, and wear track radius. The kinetic friction coefficient was used to analyze the results as an output variable. The parameters in which the best friction behavior was observed were employed again to compare the efficiency of the polymeric additive by profoundly analyzing and comparing the wear response of the system. The PCL additive showed great results by decreasing friction up to 30% compared to the neat Castor oil. Nevertheless, as the opposite effect, this additive increased the steel wear to almost half an order of magnitude. Given the above, this investigation showed that, with further studies, Poly(ε-Caprolactone) could be used as an additive in vegetable oil-based lubricants for the improvement of friction performance.

Thermo-mechanically coupled modelling of a single-asperity scratch on an isotropic isotactic polypropylene surface

Abstract Isotactic polypropylene (iPP) is a low cost semi-crystalline polymer that is easy to process, has a wide variety in properties and is, therefore, used in many applications. Many of these applications require enhanced wear-resistance to prolong the lifetime of the product. Essential is to first investigate the intrinsic response of the material in order to describe its friction and wear response. In this respect, a hybrid experimental-numerical approach is used to couple the intrinsic response to the single-asperity scratch response. The numerical model used is a 3D elasto-viscoplastic model based on the Eindhoven Glassy Polymer (EGP) model. For the first time a coupled thermo-mechanical EGP model is implemented in a Finite Element Method (FEM)-framework. The model is capable of accurately describing the intrinsic response of the material, which opens the door to qualitatively and quantitatively describe its frictional response and understand the damage formation mechanism (i.e. the initiation of wear). In this study, α- and β-phase iPP are studied. We show that the difference in the intrinsic response between the two phases has a significant influence on the friction and wear response. Moreover, a stick-slip phenomenon is proven to be the main responsible for the damage mechanism observed. The observed periodic “fish-scale” damage pattern results from periodic changes in resistance during the tip movement. A relation between the polymer intrinsic response and the damage formation mechanism is established. The influence of the applied load and scratch speed on damage formation is investigated as well.

Sliding wear behaviour study of alumina-silicate short fiber reinforced AA2014-Al alloy composite (SFRAC)

In this study, short alumina-silicate fiber reinforced AA2014 Al-alloy matrix composite was prepared through squeeze infiltration technique. Dry sliding wear behaviour of the synthesized composite was carried out using a pin on disc under the application of varying loads (20–60 N) and velocities (2–4 m s−1) and the obtained results were compared with that of squeeze cast and gravity cast Al-alloy. The wear response of the investigated materials has been explained on the basis of microstructure, wear surface heating and wear-mechanism. The wear mechanism in composite has been explained schematically with supporting wear surface and subsurface micrographs. It is noted that composite suffered from relatively higher coefficient of friction, wear rate and frictional heating as compared to the alloys, irrespective of applied load and sliding speeds.

Tribological properties of HVOF sprayed WC-Cr3C2-Ni coating

The deposition of WC-Cr3C2-Ni coating was done by High velocity Oxy Fuel (HVOF) technique. Microstructural and mechanical properties of coating were measured. Friction and abrasive wear response was evaluated with varying loads and sliding velocities. An increase of 1.6–2 times in friction coefficient (COF) was noted with rise in load and COF reduced by around 15%–20% for rise in sliding velocity. Abrasion wear rate reduced by around 2 times with rise in sliding velocity. The decrease in wear rate and COF at higher sliding velocity was due to lubricating properties of tribo oxides formed due to frictional heating. The composition of tribo oxides on worn surface as indicated by XRD analysis revealed different oxides of tungsten, chromium and nickel such as WO3, W3O8, NiO2, NiWO4, NiCr2O4 and CrO2. With increasing load, carbide pull out, delamination cracking, carbide fracture and inter splat fracture were the dominating mechanisms of material removal, whereas with increasing velocity tribo oxidation leading to oxidative wear was dominant wear mechanism.

Characterization of Ti6Al4V–Ti6Al4V/30Ta Bilayer Components Processed by Powder Metallurgy for Biomedical Applications

The design and fabrication of a bilayer Ti6Al4V–Ti6Al4V/30Ta component were performed by using the powder metallurgy process and solid-state sintering as the consolidation step. Phase change and sintering densification of the component were studied by dilatometry. The addition of 30 vol% of Ta to the Ti6Al4V matrix had a noticeable effect over the microstructural and mechanical properties of the alloy, which showed decrements of up to 12.2 and 21.5% in nano-hardness and elastic modulus, respectively. The decrement of these properties strongly affected the wear and corrosion performance of the component. Special attention was focused on the intermediate zone between layers denoted by a transition zone, which presented better wear response because of the properties and microstructure caused by the gradient diffusion of Ta. Ti6Al4V/30Ta alloy showed an improved corrosion behaviour compared to Ti6Al4V alloy, decreasing 2.4 times their susceptibility to corrosion and about two orders of magnitude their corrosion rate. The bilayer component in this study is proposed as an alternative to decrease the consumption of expensive materials with improved properties.

Rolling contact fatigue: Damage function development from two-disc test data

The concept of the rail damage function provides vital understanding of the operational performance of rail grades in terms of surface degradation. Previously, material specific damage functions have been derived from measurements in track combined with vehicle-track simulations. However, from the occurring wide range in track loading conditions it is difficult to achieve clear characterisation results from track data only.To reach more controlled loading conditions, a rolling-sliding two-disc laboratory set up could be applied. The validation of a two-disc test approach in order to define rail/wheel interface wear and RCF response is the topic of the here presented study.

Evaluation of the Microstructural Aspects, Mechanical Properties and Dry Sliding Wear Response of MoTaNbVTi Refractory High Entropy Alloy

MoTaNbVTi refractory high entropy alloy was synthesized by the vacuum arc melting technique in its equi-atomic composition. The modification of its microstructural features along the vertical cross-section of the sample was associated with undercooling phenomena and the release of heat of fusion. The examined system exhibited high micro and macro-hardness values, while concerning its compression tests, it presented an improved mechanical behavior compared with other refractory systems studied, ensuring the highest ductility values. In terms of sliding wear response, the use of a metallic counterbody partner combined with the increase in sliding distance, led to possible thermal fatigue effects, while the presence of a ceramic counterbody ball was associated with the lubrication action of the formed oxides and the improvement of the alloy’s tribological response, as the sliding distance increased.

Effect of Silicon Content on the Wear Behavior of Low-Carbon Dual-Phase Steels

The aim of this study is to understand the influence of the silicon content and volume fraction of martensite obtained by intercritical annealing at three temperatures (750, 780, and 800 °C) on the wear behavior of low-carbon dual-phase steels. Dry sliding wear tests were carried out in three sliding intervals (0–200, 200–600, and 600–1000 m) by using a pin-on-disk machine at normal load of 30 N, room temperature, and fixed sliding velocity of 0.5 m/s. The weight loss of the specimens was measured and the wear rate calculated. For all the samples, the wear rate decreased with increasing sliding distance. The results of the present investigation clearly show that the effect of the intercritical annealing temperature is greater than that of the silicon content. Among the three tested temperatures, the wear resistance was more sensitive to the silicon content at the lowest (750 °C). Both the content and hardness of the martensite were factors affecting the wear resistance of the dual-phase steels. The wear response of the samples can be described on the basis of the interaction between the martensite volume fraction and hardness. The role of the silicon content in the oxidation of steels was also examined.

Wear and mechanical characterization of Mg–Gr self-lubricating composite fabricated by mechanical alloying

Abstract In this research, the wear and mechanical responses of pure magnesium-graphite (Mg–Gr) composite have been investigated aiming to get the optimum composition of reinforcement. The composite materials were fabricated by mechanical alloying. The percentage of graphite reinforcement was chosen as 3, 5, 7 and 10 wt.% to identify its potential for self-lubricating property under dry sliding conditions. The mechanical properties including hardness, tensile strength and flexural strength of the composites and the base material were tested. The wear tests were conducted by using a pin-on-disc tribometer. The results show that the mechanical properties decrease with increasing graphite content as compared to that of the base material. The wear rate and average coefficient of friction decrease with the addition of graphite and was found to be minimum at 5 wt.% graphite reinforcement. The addition of 5 wt.% graphite in the composite exhibits superior wear properties as compared to that of the matrix material and other compositions of the Mg–Gr composites.

Sliding wear and solid particle erosion response of aluminium reinforced with tungsten carbide nanoparticles and aluminide particles

AbstractIn the present effort, aluminium matrix composites (AMCs) were produced by the addition of submicron‐sized WC particles of low (up to 2.5 vol%) content into a melt of Al1050. Casting was assisted by the use of K2TiF6 as a wetting agent and mechanical stirring in order to limit particle clustering. Particle distribution was reasonably uniform comprising both clusters and isolated particles. Various different reinforcing particles' phases were identified, both in situ (Al‐W, Al‐Ti, and Al‐W‐Ti intermetallic phases) and ex situ (WC particles) of various morphologies shapes and sizes. Increase of the reinforcing particle content led to an increase of the tendency for clustering. The wear properties of the composite were examined by dry sliding wear. The worn surfaces and the produced debris were examined by SEM‐EDX, and an effort to correlate the wear response of the produced materials with the matrix and the reinforcing phase characteristics was attempted. In general, the increase of the reinforcing phase content led to an improvement of the sliding wear response. Solid particle erosion experiments were carried out for impact angles of 30°, 60°, and 90°. Τhe eroded surfaces were examined with SEM‐EDX, and possible erosion mechanisms were proposed based on morphological and other material characteristics. Intensive particle clustering seemed to deteriorate the erosion resistance of the systems. Medium concentrations of the reinforcing particles (1.0‐1.5 vol% WC) are proposed as a recipe for optimum sliding wear and solid particle erosion resistance behavior.

Influences of wear on dynamic characteristics of angular contact ball bearings

Wear between balls and races has significant effects on the dynamic characteristics of bearing, which is the main reason to cause bearing failure. Some existing contact stiffness models were established to study the dynamic characteristics of bearing. However, the wear of bearing has been rarely investigated due to the complexities of contact load and wear mechanism. This paper presents a new dynamic wear simulation model of angular contact ball bearings mounted in pairs to solve this problem. A final contact stiffness model is established based on the wear model. The effects of running distance, horizontal load, preload, initial contact angle, number and diameter of balls on wear performances are analyzed. A generalized time-varying and piecewise-nonlinear dynamic model of angular contact ball bearings is established to perform an accurate investigation on its dynamic characteristics, especially considering the coupling effects of wear and rolling contact. The effects of wear on the contact stiffness and nonlinear dynamic characteristics are analyzed according to the dynamic model. Additionally, the variations of the contact stiffnesses and frequency responses with different preloads are discussed and the results indicate that parameter selection has significant effects on the wear and nonlinear response.

The effect of a boride diffusion layer on the tribological properties of AISI M2 steel

AISI M2 high speed steel is commonly used as cutting tool in the machining process. Nevertheless, their useful life can be easily reduced by an eventual failure. In the last few years, thermochemical surface hardening process in which boron atoms diffuse into metals surface have been reported as an alternative to improve tribological properties. In the present work, a diffusional boron heat treatment was carried out at 950 °C by 6 h on AISI M2 steel sample. Scanning Electron Microscopy (SEM) and Micro-hardness testing was undertaken with the purpose to assess the diffusional boride microstructure and its effect on mechanical properties. On the other hand, tribological test was performed using a ball on disc tribometer tracking their friction coefficient and volume loss. Surface damage was analysed using stereomicroscopy and SEM. The boride diffusional layer achieved 50 µm with an increment of 7 times in the microhardness regarding to untreated sample and 4 times regarding to the adjacent zone to the boride layer. In addition, a reduction of the friction coefficient and better wear response was achieved as a result of boride heat treatment.

Characterization and tribological analysis of graphite/ultra high molecular weight polyethylene nanocomposite films

Wear of Ultra-High Molecular Weight Polyethylene (UHMWPE) plays an important role in medical industry. In this work the UHMWPE was reinforced with graphite nanoparticles at different concentrations. The nanocomposite films were prepared by cryo-milling followed by sintering. The mechanical test results showed that with increasing the graphite concentrations, Hardness, Young's modulus and the yield strength of the Graphite/UHMWPE composite increased, but the strain at fracture decreased. Hot pressed composite structures were characterized for their tribological behavior in a ball-on-disk tribometer using a normal load of 30 N. Graphite nanoplates reinforcement improved on the wear resistance, which is a combined effect of lubrication as well as toughening offered by graphite nanoplates. The best wear responses seen at lower concentrations of graphite viz. 0.1, 0.3 and 0.5 wt%. The prepared Graphite/UHMWPE composites could be an appropriate candidate to be used in joint articulations, where low friction and high wear resistance are required.