Pin Materials Research Articles

On the Wear Behaviour of Bush Drive Chains: Part II—Performance Screening of Pin Materials and Lubricant Effects

In this second part of the paper series, parameter investigations of the tribological system chain pin/bush contact, carried out on a specifically developed pin on bush plate model test technique, are presented. Both the pin material and the lubricant varied widely. In case of the pin materials, a Cr-N monolayer coating and a Cr-N-Fe-based multilayer coating were investigated. As for the lubricants used, two different performing engine oils from the field were tested as well as fresh oils, some of which were diluted with a soot surrogate (carbon black) and diesel fuel in different amounts. The results show, among other things, that friction and wear performance strongly depend on the combination of pin material and lubricant used. In this context, especially the Cr-N-Fe in combination with the used engine oils showed a high wear resistance and low friction losses compared to the Cr-N reference. In the case of fresh oils with soot, the friction losses were higher but comparable between the pin materials, and a slightly better wear performance of the Cr-N was observed due to an agglomeration effect of the soot surrogate. In general, it was found that especially soot-free oils show clear wear advantages independent of the pin material used. Thus, soot clearly has a wear-promoting component. The investigations of this study suggest that a leading mechanism that is based on a corrosive–abrasive effect in the tested system, but this is more related to the soot surrogate carbon black than engine soot.

Microstructural, Mechanical and Wear Properties of Al–1.3%Si Alloy as Compared to Hypo/Hyper–Eutectic Compositions in Al–Si Alloy System

The microstructure, mechanical properties, and wear behavior of three Al–Si alloys, namely: Al–1.3%Si, Al–1.5%Si and Al–13.5%Si were investigated. The specimens were examined by using an optical microscope to investigate the microstructural features of pin materials. Microhardness numbers and mechanical behavior parameters were determined by using a microhardness indenter and compression test, respectively. The dry sliding wear test was carried out using a pin-on-disc apparatus by varying the rotational speed (250, 350, and 450 rpm), normal load (5, 10 and 20 N) and test time (5, 10 and 15 min) at a constant sliding diameter of 300 mm. The surface roughness index (Ra) of the worn surfaces was determined by using a profilometer. The microstructure of Al–1.3%Si alloy was described as a fine eutectic colonizing in the FCC-Al phase matrix. Coarse eutectic dendrites surrounding the primary FCC-Al grains were observed in Al–1.5%Si alloy. The microstructure of Al–13.5%Si alloy showed a uniform layered structure of FCC-Al + Diamond Si eutectic. The average microhardness number was directly proportional to the Si concentration. Al–13.5%Si alloy with a high microhardness number (47.16 HV) showed excellent resistance to wear and exhibited a smoother surface at the end-of-wear test. The improved wear resistance in this case could be due to the presence of Diamond-Si hard phase in large quantities compared with other compositions. On the other hand, Al–1.5%Si alloy showed poorer resistance to wear because the mass loss action was dominated by a particle detachment mechanism. The response surfaces of the mass loss vs. speed, normal load and time showed increased mass loss when the three controlled parameters were increased. However, Pareto charts of the main effects of parametric interactions showed that the normal load was the main factor that must be considered when studying the tribological properties of Al–Si alloys.

In-situ observation of influence of metal types on wear process in dry conditions

We conduct in-situ observations of the wear process of metals in dry conditions. To this end, we constructed an experiment to observe the wear process of a point contact area, created between a rotating sapphire disc and a metal pin. The experimental setup included a microscope and a camera with visible-light and near-infrared detectors. Several steels, including stainless steel, and copper alloys were tested as pin materials. The wear comprised plastic flow, formation of transfer layers from the metal pin onto the sapphire disc, and expansion of the contact area. The influences of metal compositions and base metals on the wear behaviour were discussed.

Advanced glass seals for implantable medical devices

AbstractLanthanum Borate (LaBor) glass is used as the insulating glass seal material in feedthroughs used in implantable medical devices. Guided by finite element analysis modeling, alumina was selected as a promising additive for the LaBor glass to tailor its material properties for glass seals that are better matched with lower CTE pin materials. Thermal expansion and elastic properties were measured for LaBor glass containing up to 20 wt% alumina. Trends for thermal expansion and elastic modulus were reasonably predicted by literature descriptions. As predicted by finite element modeling, the modified glass showed good resistance to crack growth and the hermetic behavior of the seal was confirmed by helium leak detection and fluorescent dye observations.

Effects of ferromagnetic & carbon-fibre Z-Pins on the magnetic properties of composites

This paper investigates for the first time the effects of Z-pins on the magnetic properties of composite laminates. In-plane and out-of-plane M-H curves of IM7/8552 laminates with and without Z-pins have been characterised by an MPMS3 SQUID magnetometer. Two kinds of pin materials (T300/BMI composite and ferromagnetic Ni/Fe alloy) have been studied at three different volume fractions (nominally 0.5%, 2% and 4%). The unpinned and carbon-fibre pinned laminates were found to be diamagnetic. The carbon-fibre pin had no significant influence on the global magnetic properties of the laminates. The Ni/Fe alloy pin increased the laminate linear-part magnetic volume susceptibility up to 1.87 and 0.13 for the out-of-plane and in-plane directions, respectively. Numerical modelling has been conducted to support the investigation of the effect of the pin volume fraction on the overall magnetic susceptibility and saturation magnetisation. The laminate out-of-plane susceptibility exhibits a nonlinear behaviour dependent on pin volume fraction, due to interactions between adjacent pins. The saturation magnetisation is proportional to the pin volume fraction and independent of field direction.

Investigations of contact stresses and wear parameters for pin on disc using different pin materials

Wear component is an important factor influencing products service life which is based on material property and their behavior under given conditions. Therefore it is important to predict wear rate of components. In this paper we have discussed the wear parameters of pin on disc by varying pin materials. Numerical analysis was conducted on basis of load for different material components. When two bodies are in contact, contact pressure induces stresses in components.. Due to coefficient of friction, heat is generated between components. Hertz theory has been considered to determine the wear characteristic by using different pin materials on a steel disc. It was observed that aluminium alloy pin on steel disc generated low coefficient of friction, temperature rise and wear rate.

A review on tribological behaviour of steel against steel

This paper summaries the wear behavior of steel vs steel for various industrial application. In today’s world, many new materials are developed and manufactured. Tribological behaviour of material is investigated in terms of wear and frictional characteristics using pin on disc machine. This paper reviews the experimental investigation of tribological behavior of different grade of steel considering various aspects such as coated/uncoated disc and pin materials, effect of magnetic field and lubricant under different operating and loading conditions at room and at high temperature. The summary of various research papers is tabulated and discussed. It observes that the common objective of wear analysis is to minimize the weight loss (wear), roughness, and coefficient of friction etc. This paper gives an idea of material selection, range of operating and loading conditions under dry and lubricated conditions for various applications and future direction.

A rapid and simple measurement method for biofilm formation inhibitory activity using 96-pin microtiter plate lids.

The purpose of this study was to develop a rapid and simple measurement method for biofilm formation inhibitory activity, and to screen food additives and foodstuffs that inhibit biofilm formation. The measurement method for biofilm formation inhibitory activity was developed by combining biofilm formation on pins of microtiter plate lids and staining using crystal violet. The optimum conditions for biofilm formation on the pins were established for seven Gram-positive and six Gram-negative bacteria by investigations of media, incubation time, and pin materials. Minimum concentrations of food additives required to inhibit biofilm formation were determined using the proposed method. The values obtained by the proposed and conventional methods agreed well. In addition, by sequential measurements of minimum inhibitory concentrations and minimum bactericidal concentrations using the proposed method, mechanisms of inhibition of biofilm formation were assessed. Furthermore, inhibitory activities of the water extracts of 498 different plant foodstuffs on biofilm formation by Streptococcus mutans were measured; five of the extracts showed potent inhibitory activities. The method proposed here circumvents the tedious and time-consuming conventional method in which biofilms are cultivated on the bottom of wells of microtiter plates.

Tribological and rheological properties of palm and brassica oil with inclusion of CuO and TiO2 additives

In the present study, tribological properties of vegetable oil addition of nanoparticles have been carried out using pin on disc tribometer. Vegetable oils are Palm oil and Brassica oil are used in tribological test. Copper oxide (Cuo) nanoparticles and Titanium oxide (Tio2) nanoparticles are used as additives on weight percentage of 0.1% and 0.5%. From the study it was perceived that Palm oil with 0.5% Cuo based lubricant sample illustrations significantly reduce in coefficient of friction and wear than rest of lubricant samples. Viscosity and thermal conductivity properties also increase with increasing nanoparticles concentrations in vegetable oils (palm and Brassica). SEM (Scanning Electron Microscopy) images shows the worn surface of pin materials.

Characterization of the Effect of Moisture on Tribology of Titanium Rubbed Against Different Pin Materials

Tribology investigations were conducted to understand the effect of humidity and water adsorption at the interfacial surface on the friction coefficient of titanium. Pin-on-disk tribometer tests were conducted at different levels of humidity ranging from 0% to 71% RH using aluminum and steel pins on a titanium plate. The variation of the mean coefficient of friction was plotted as a function of relative humidity. The friction coefficient slightly decreased when the relative humidity was increased from 0% to 10% RH. However, it increased with a further increase in humidity. The maximum friction coefficients were observed at 55% and 65% RH for steel and aluminum, respectively. The thickness of the wear tracks also showed the same trend as the friction coefficient. Under high humidity conditions, water vapor can condense on the surface of the moving machine parts. To understand the influence of this water film, a pin-on-disk test was carried out on a sample where a thin film of water masks metal surfaces from contact. Although the coefficient of friction was similar for both the aluminum and steel pins’ interaction with titanium (~0.36), the wear tracks were not formed for steel pin/titanium interaction even though this experiment was conducted for more cycles.

Failure analysis of die casting pins for an aluminum engine block

This paper describes an investigation which was done on prematurely failed pins used in die-casting dies for aluminum engine blocks. To investigate the causes of the failures, static and fatigue strength evaluations of the pin materials and the deterioration degree of the strength due to exposure to high temperatures were evaluated. SEM observations of the fracture surfaces of broken pins revealed that the fractures were the fatigue failure type caused by thermal stresses upon thermal expansion and cooling during the repeated die-casting process. A solidification analysis of the die-casting process was conducted to determine the temperature distribution of the dies and pins, and a coupled thermal-structure analysis was carried out using the temperature distribution information to determine the magnitude of the thermal stress in the pin. The maximum thermal stresses were used to predict the fatigue lifetime of the pin. The result of this investigation reveals that cooling holes at the center of the pin were machined with some degree of eccentricity, leading to a concentration of the thermal stress at the thin part and, ultimately resulting in a premature failure. Appropriate machining of a cooling hole in the die pins must be carried out in order to avoid premature failures of these components.

Wear behavior of TC11 and AISI M2 in pin–disk tribo-system

The wear behavior and mechanism of TC11 (pins) and AISI M2 (disks) under different test conditions were studied. The results show that tribo-layers formed on the worn surfaces of both TC11 alloy and AISI M2 steel. As for TC11 alloys at 25 °C, the wear rate increased to high values with an increase in the load; and abrasive wear and adhesive wear prevailed. However, at 600 °C, the wear rate decreased sharply and oxidative wear prevailed. As for AISI M2 steels, at 25 and 600 °C, the wear rates were relatively low. The wear mechanisms at 25 and 600 °C were abrasive wear and oxidative wear, respectively. The wear rates of AISI M2 steel were lower than those of TC11 alloy at 25 and 600 °C. The wear performance of the tribo-pair was noticed to be closely related to their mutual contact mode except for the test conditions and the pin and disk materials, and the intermittent contact mode reduced wear of AISI M2 steel.

Tribological investigation of copper and AISI 304 steel during dry sliding wear

Copper-based metal matrix (CBMM) composite is used in ball bearings and other tribological components due to significant improvement in thermal and mechanical properties. However, copper alloys based bearings are likely to fail due to severe surface fatigue wear in rolling/sliding condition. To understand the fatigue wear of copper-alloy which is dominated by the evolution of asperity characteristics, the study of topography evolution in dry sliding condition is essential. The purpose of this study is to study the tribological behavior of copper-steel material combination in dry sliding condition. The tribological properties of copper are also compared with AISI 304 steel. Experiments are performed on pin-on-disc tribometer. The AISI 52100 steel disc is used as a counter body during the experiments on AISI 304 and copper pin materials. The effect of normal load on friction coefficient and wear is studied. Surface topographies of the worn surfaces are measured using a 3D optical profiler. Scale-sensitive fractal analysis (SSFA) is performed on worn surfaces to analyze the complexity of the surface. It is found that surface complexity increases with an increase in normal load. At low scale, worn surfaces are rough and can be simplified by applying fractal theory. At lower load, an oxide layer is formed on the copper surface which reduces the direct asperity contacts. At higher load, distortion in the shape of autocorrelation is observed due to an increase in adhesion and plowing wear.

Effect of Biodegradable Refrigeration oil on the Tribological Behaviour of Liner/Ring Tribo pair material of Hermetically Sealed Compressors

Abstract An improvement in co-efficient of performance (COP) of a vapour compression refrigeration (VCR) system is largely depends upon the work of compression which in turn rely on the quality of lubricants. Further the compatibility of cylinder liner/piston ring tribo pair material of a hermetically sealed compressor is another vital aspect to consider during the development of refrigeration oil. The base oil, which has been used for the formulation of refrigeration oil, is derived from petroleum products. However the depletion of petroleum reserves, uncertainty in crude oil prices, energy demand and increased environmental awareness has promoted the crucial requirement to synthesize refrigeration oil from environmentally friendly energy resources. The present investigation is intended to formulate a rapeseed oil based trimethylolpropane tri ester as biodegradable refrigeration oil with good thermo-oxidative stability and cold flow behaviour via chemical modifications. Thermo gravimetric Analysis (TGA) and Differential Thermal Analyses (DTA) were performed to study the thermo-oxidative stability of biodegradable refrigeration oil. This investigation is also addressing the issue of the tribological behaviour of cylinder liner/piston ring material of a hermetically sealed compressor in VCR system under the influence of biodegradable refrigeration oil and synthetic refrigeration oil (ISO 68 grade-POE oil) using a pin-on-disc tribometer. The surface morphology analysis of tested pin materials was also carried out using scanning electron microscope. The tribological experiments were carried out in accordance with ASTM G99. Under similar experimental conditions, biodegradable refrigeration oil exhibited good friction reduction behaviour and inferior wear reduction behaviour as compared to synthetic refrigeration oil.

Application of the voltammetry of microparticles for characterizing wear debris produced in the sliding wear regimes of steels

Electrochemical characterization of wear metallic particles produced during pin-on-disc sliding tests is not conventionally carried out, possibly because of their small grain size, irregular shape and heterogeneous composition. The characterization of its reactivity can be important in the study of the relationship between oxidative and mechanical processes occurring at the sliding interfaces. Towards this goal, here we report the application of voltammetry of microparticles methodology to investigate the reactivity of sliding wear debris from steels. Low alloy (AISI 4140) and tool (AISI H13) steels were used as pin and disc materials, respectively, during the sliding wear tests. The variations of hardness of both sliding bodies resulted in the operation of mild and severe wear regimes. The worn surfaces were examined by stereoscopic and scanning electron microscopes. The wear particles were mechanically immobilized on the surface of a paraffin-impregnated graphite rod electrode and characterized by voltammetry in 0.1M HClO4. The voltammograms reveal important information on oxidation stability of worn surfaces. Results were confirmed by electrochemical impedance spectroscopy measurements of both pin and disc surfaces for the mild and severe wear.

Dry Sliding Wear Behaviour of Rheocat Al-5.7si-2cu-0.3mg Alloy

In this study, the effect of improved microstructure of Al-5.7Si-2Cu-0.3Mg alloys by using semisolid process on hardness and dry sliding wear behaviour were investigated. The microstructures of conventional cast alloy were totally dendritic, while in rheocasting the dendritic transfer to fine globular microstructures after using cooling slope casting. Tribological tests were carried out by using a pin-on-disc apparatus in dry sliding conditions. Wear tests were at low sliding speed 1ms-1 ,applied load at 50N and three different sliding distance (i.e., 1.8Km, 5.4Km and 9Km) respectively. An optical microscope and a scanning electron microscope were used to examine the microstructure and to understand the wear mechanism on the worn surface of both samples. The results showed that, the wear resistance of rheocast alloy was improved and higher than that those produce by conventional casting. The volume loss of rheocast alloy show reduction more than 18% at 1.8Km and 10% at 9Km compared to as-cast alloy. Moderate wear regimes were appeared in both alloys, according to the range of wear rate. The friction coefficient had increased due to increase in the contact point between pin and disc materials. The dominant wear mechanism for conventional and rheocasting alloys was adhesion wear and abrasive wear respectively.

Experimental Investigation on Tribological Characteristics of Biodegradable Refrigeration Oil using Pin on Disc Tribometer

The present study addresses the issue of the tribological behaviour of cylinder liner and piston ring material of a hermetically sealed reciprocating compressor of Vapour Compression Refrigeration system under the influence of pentaerythritol ester based biodegradable refrigeration oil and compare with synthetic refrigeration oil (Polyol ester-ISO 68grade) using the pin on disc tribometer. Synthesis of pentaerythritol ester based biodegradable refrigeration oil for household domestic refrigeration compressors was carried out via successive transesterification of rapeseed oil. The biodegradable refrigeration oil was blended equally with synthetic refrigeration oil to formulate the best biolubricant. Further Energy Dispersive X-ray (EDX) technique was adopted for the chemical characterisation of the pin material surfaces. The wear behaviour of the tested pin materials were evaluated using scanning electron microscope. The results show that under same investigational conditions 50% blend of pentaerythritol ester biodegradable refrigeration oil (PBRO 50) with synthetic refrigeration oil demonstrated superior friction reduction performance and inferior wear reduction performance as compared to synthetic refrigeration oil.

Microstructure and nanohardness of Ag and Ni under friction in boundary lubrication

Evolution of deformation microstructure and nanohardness of Ag and Ni after friction in the BL regime was studied. All friction tests were conducted under lubricated conditions using a pin-on-disk rig. Pure fcc metals such as Ag and Ni, with different SFE (16 and 125 mJm−2, respectively), were chosen as pin materials. Cross sectional transmission electron microscopy (TEM) lamellae were prepared from the pins using a focused ion beam (FIB). Using TEM, we analysed the regions of the pins that are in steady state after friction; the friction coefficient (μ) and hardness (Hs) remained unchanged with deformation in the BL regime. After the wear tests, the specimens were cross-sectioned in longitudinal and transverse directions (parallel and perpendicular to the direction of friction). Nanoindentations were performed using a Berkovich diamond tip. A gradient of grain sizes during the friction of Ag and Ni in BL regime was revealed by TEM imaging. Deformation twinning followed by limited recovery within the surface of Ag led to the formation of a relatively thick top layer of ultra-fine equiaxial grains. Thermally activated processes for the rearrangement and annihilation of dislocations are accelerated during the friction of Ni due to high SFE and contact temperature. Cross-sectional microstructures observed normal and parallel to the direction of friction are dissimilar. Steady state values of grain size, ds, and hardness, Hs, after friction in lubricated conditions are explained by the balance between hardening and dynamic recovery in surface layers, and they strongly depend on the SFE and temperature. A correlation between the wear properties (wear coefficient) and total work of deformation during nanoindentation shows a similarity in the nano- and microscales in lubricated friction.

Parametric optimization of dry sliding wear and friction of germanium doped lead calcium titanate borosilicate glass ceramic

In this study, specific wear rate (SWR) and coefficient of friction (COF) of the synthesized samples in 55[(PbxCa1−x)O.TiO2]−44[2SiO2.B2O3]−1Ge with (0 ≤ x ≤ 0.7mol%) system of glass ceramics was optimized using Taguchi method. The ASTM standards were used for preparing the samples for friction and wear tests on a pin-on-disc tribometer. The glass ceramic samples were used as pin materials that slid against a disc made up of EN32 steel. For assessing the tribological properties of the glass ceramics, three control factors, viz. material-compositions with varying fraction of x (x = 0.0, 0.1, 0.3, 0.5 and 0.7mol%), sliding speeds (2.61, 3.14, 3.66, 4.18 and 4.71m/s) and loads (10, 15, 20, 25 and 30N) were considered in an L25 orthogonal array design. The optimum input parameters for the minimum SWR and COF were selected based on signal to noise ratios and main effect plots. Analysis of variance (ANOVA) revealed that the sliding speed and lead oxide content of the material are the most contributing factors on SWR and COF, respectively. The optimization for minimizing the SWR and COF was carried out and confirmed. The surface morphologies of the tested glass ceramic sample were studied using scanning electron microscope (SEM) and the elemental analysis of the samples was done using energy dispersive analysis of X-rays (EDAX). The Vickers hardness at the free surface of the glass ceramic samples increased up to 9.59mol% of lead oxide with the maximum hardness of 23.59GPa. The compressive strength of glass ceramic samples could reach up to 190MPa.

Dry sliding behavior and friction layer formation in copper-free barite containing friction materials

The tribological behavior of materials used for vehicular car brakes is investigated using pin-on-disc tests. In particular, the disc was made of a commercial gray cast iron, used for real brake discs. The pins were made of newly developed formulations of friction materials, whose thread-line is the elimination of copper. This element was present in the selected bench-mark friction material, which is a low-metallic material, in which copper is replaced by re-arranging the overall composition and by adding increasing amounts of barite, up to a total maximum concentration of 33.5wt%. Wear products, namely the friction layers that formed on the mating surfaces of the pin materials, have been characterized to identify the main phenomena involved and influencing wear rate and friction coefficient. The main outcome of the research is the beneficial influence of barite, the compositional range that is important to target, the possible routes to be pursued, to improve the results achieved so far.