Laboratory Wear Tests Research Articles

Developing an optimised method for accurate wear testing of dental materials using the ‘Rub&Roll’ device

Dental materials are challenged by wear processes in the oral environment and should be evaluated in laboratory tests prior to clinical use. Many laboratory wear-testing devices are high-cost investments and not available for cross-centre comparisons. The ‘Rub&Roll’ wear machine enables controlled application of force, chemical and mechanical loading, but the initial design was not able to test against rigid antagonist materials. The current study aimed to probe the sensitivity of a new ‘Rub&Roll’ set-up by evaluating the effect of force and test solution parameters (deionized water; water + abrasive medium; acid + abrasive medium) on the wear behaviour of direct and indirect dental resin-based composites (RBCs) compared with human molars against 3D-printed rod antagonists. Molars exhibited greater height loss than RBCs in all test groups, with the largest differences recorded with acidic solutions. Direct RBCs showed significantly greater wear than indirect RBCs in the groups containing abrasive media. The acidic + abrasive medium did not result in increased wear of RBC materials. The developed method using the ‘Rub&Roll’ wear machine in the current investigation has provided a sensitive wear test method to allow initial screening of resin-based composite materials compared with extracted human molars under the influence of different mechanical and erosive challenges.

Wear Behavior of SBR/BR Compounds Including Different ZnO Types

Zinc complexes have considerable impact on human health and environment especially on aquatic wildlife. One of the main sources of zinc release to the environment is worn rubber particles from tires. Environmental footprint of zinc oxide during production, ecological and economical concerns have prompted the researchers to reduce its use in rubber formulations. Rubber compounds used in the tread, which is the part of the tire in contact with road, must have high wear resistance. In order to determine the wear performance, laboratory wear tests need to be carried out prior to road tests. In the present study, a tread compound recipe based on SBR/BR blend is designed using conventional and composite ZnO materials having CaCO3 as core. Wear behavior of the control and trial compounds prepared with these ZnO materials are tested at room temperature by using Lambourn test instrument. Wear rates and wear energies are calculated using the weight loss data at different slip rates. Based on the wear performance of the trial compounds as well as their cure and mechanical properties, it can be concluded that composite ZnO materials are good candidates to replace the conventional activators in rubber compounds to provide environmental and economic gains.

Field and Laboratory Wear Tests of Machine Components Used for Renovation of Dirt Roads-A Case Study.

Renovation of dirt roads requires a reliable and durable work tool. This article includes the methodology of field and bench tests as well as the results of these tests and conclusions for cutters used for dirt road renovation. The main novelty of the research presented in this article was to determine the wear mechanisms occurring during field and laboratory tests, to determine the differences in wear levels and the cost of renovation of one kilometer of dirt road. Calculations of the efficiency of replacing these working elements and the cost of operating various cutters per km are also presented. The lowest mass loss was characterized by milling cutters Ø25 mm mounted on an expansion sleeve and amounted to 130 g. The dominant wear mechanism that was observed after the renovation of dirt roads was micro-scraping and micro-bruising. For this variant, the cost per 1 km of road renovation was also the lowest and amounted to about PLN 2.

Comparative study of fabricated superhydrophobic surfaces via LST with carbon soot, chemical etching and auto-oxidation

The present work aims to fabricate superhydrophobic surfaces (SHS) on commonly used low carbon steel (AISI 1018). Laser surface texturing (LST) was used for creating circular textures on substrate while varying the diameter and pitch of the texture geometry with the help of fiber laser machine. Three different methods, (a) LST followed by waxing and candle sooting, (b) LST followed by chemical etching, and (c) LST followed by auto-oxidation were introduced to fabricate SHS and to make a comparison among them. Also, the mechanical stability and durability of the modified surface via these methods were evaluated by the mean of small-scale laboratory wear tests like tape peeling, sand abrasion, and water impact test. The developed surfaces were characterized for surface roughness, FESEM analysis, EDS analysis, besides water contact angle (WCA) and sliding angle (SA) have been evaluated. The highest WCA and lowest SA were discovered on textured and chemical etched followed by dip coated specimens and was found to be ∼159° and ∼5° respectively. However, the auto-oxidized laser textured samples showed best results among other methods in terms of mechanical stability. These processes are simple, effective and can be of great interest for producing SHS for various industrial applications.

Development and Verification of Triple-Ridge-Shaped Cutter for PDC Bits

Summary Polycrystalline diamond compact (PDC) cutter is the key component of PDC bits, whose rock-breaking characteristics are particularly crucial for the bit performance. Based on the understanding on rock-breaking characteristics of various shaped cutters, the multiridge-shaped cutter has been developed to improve the cutting efficiency and durability of PDC cutters. The design of multiple ridges combines the advantages of both the shaped cutter and the reasonable narrow cutter spacing of the bit cutting structure. More specifically, a triple-ridge-shaped cutter (TSC) was compared with the widely used axe-shaped cutter (ASC) in this work to recognize the superiority of the novel multiridge cutter shape. Numerical simulation, laboratory experiments, and field testing were performed to investigate the cutter-rock interactions of TSC and ASC. Numerical simulations were carried out using nonlinear finite element software LS-DYNA and verified by the single cutter testing. Both numerical and experimental results proved that the stress concentration caused by the triple-ridge cutter shape of TSC is significantly greater than that of ASC during the cutter-rock interaction. And the tangential force of TSC is much less than that of ASC under the same cutting conditions, indicating that the PDC bit equipped with TSCs requires less torque while drilling. According to the results of the fractal analysis model of cuttings and the mechanical specific energy (MSE), TSC consumed less drilling energy than ASC to break the same volume of rock, which demonstrated that the TSC has greater cutting efficiency than ASC. Beneficially, the greater cutting aggressivity of TSC in turn improves the wear resistance. The laboratory wear and impact tests presented that TSC outperforms ASC in both wear resistance and impact resistance, indicating better durability under downhole. Although only one controlled experiment was conducted in the field, the field test result showed over 100% improvement in average rate of penetration. In short, the numerical, laboratory, and field testing have confirmed a great potential of TSC in improving the cutting efficiency and durability of PDC bits. The results of this work will provide valuable guidance for the development of shaped PDC cutters to overcome engineering limitations.

Enhanced tribological properties of wind turbine engine oil formulated with flower-shaped MoS2 nano-additives

Wind energy has become one of the most viable green and sustainable energy sources. A major concern of this sector is the damage of mechanical components and energy losses caused by repeated friction and wear, which lead to reduced efficiency and increased maintenance costs. The development of new lubricant additives with high anti-wear properties and friction reduction capabilities is of paramount importance to ensure long service life and high efficiency of mechanical devices. Herein, flower-shaped MoS2 nano-additives of about 150 nm were prepared under mild conditions through a hydrothermal process. Octyl- and octadecyltrichlorosilane were used as surface hydrophobization agents to enhance the colloidal stability of MoS2 nano-additives formulations in wind turbine engine oil. Increasing the length of the alkyl chain grafted onto the particles improved the colloidal stability up to at least one year and, more importantly, resulted in the lowest friction and best wear reduction capabilities, as shown by the pin-on-disk tribometer and laboratory wear tests.

Tribological performance of high-strength cast iron in lubricated contact containing carbon black

It is well-known that diesel engines generate soot during the combustion process, leading to a higher level of pollutant emissions and severe wear of contact surfaces in relative motion, resulting in worse engine performance. Carbon black has been used in laboratory wear tests to simulate soot in engine components such as piston rings and cylinder liners. However, there are still many questions to be answered, especially concerning the interaction between the particles, lubricants, and surface topography in contact. In the past years, compacted graphite iron (CGI) has been substituting grey cast irons in engine blocks because of its improved mechanical properties, resulting in thinner walls for lighter blocks and improving engines' performance. However, CGI's tribological behavior of higher strength grades has been scarcely studied due to its production cost and complexity. In the present study, two CGIs of high strength (JV450 and JV500 – ISO 16112/2017) were used as cylinder liners on ring-on-cylinder lubricated wear tests a CETR-UMT-Bruker tribometer. The cylinders' surfaces were honed to a plateau finishing, and the counterbody used was a commercial compression ring of nitrided stainless steel. Carbon black particles were added to commercial SAE CF-30 lubricant, simulating the presence of soot. The testing load and oil temperature were 175 N and 100 °C, respectively, creating a severe wear condition. Roughness measurements using interferometry were performed on the worn surfaces to compare with the plateau's topography and roughness parameters honing texture. The variation of structure height was used as the indicative of liner wear. Results showed almost the same coefficient of friction (COF) for all tested conditions. Still, the reason for each case was different, the ejection of graphite during sliding being more critical for JV450 iron. The carbon black was able to change the contact conditions. The high-strength GJV500 iron performed better, considering a tribological merit index (TMI), less sensitive to the presence of carbon black in the lubricant oil.

Research methods for the evaluation of the relevance of application oriented laboratory wear tests

In this work, different research methods and test procedures were examined and compared in order to have a better understanding of the relevance of various application oriented laboratory wear tests relative to the in-service performance of the steels in mining conditions. One of the important results of this study is that quite different wear events can be compared, when the wear rates are presented as the mass loss of the sample divided by the wear area, contact time, and density of the material. However, this kind of information is commonly very difficult to obtain for the in-service samples, and thus normalizing of the results with a reference material is often an easier route. On the other hand, thorough characterization and comparison of the wear surfaces and deformations is essential for the confirmation of the similarity of the wear mechanisms in different cases or different tests. In the studied case of the wear plate of a dumper truck body, several test methods were needed for the experimental simulation of the complex wear environment in the haulage of minerals.

Investigating the corrosion-fatigue wear on CrN coated piston rings from laboratory wear tests and field trial studies

The interacting mechanisms of corrosion and fatigue wear of the CrN coated piston rings were investigated in two ways: (1) by comparing the laboratory test data to field results, and (2) by simulating the stress distribution and crack origins in the CrN coating using a Finite Element Method (FEM). The surface and interface characterizations confirmed that fatigue wear resulted in cracking and spalling of the CrN coating. At the same time, corrosive wear was promoted by sulfur incursion along boundary defects in the CrN coating. FEM simulations showed that the magnitude of stresses at the interface of Cr particle/CrN matrix was a function of Cr particulate sizes, and they also identified crack initiation sites at rubbing contacts. The dominant factors contributing to the propagation of the surface/subsurface cracking were elucidated. Inherent defects initiated cracks, and the repetitive shear stress coupled with the effects of corrosive species gave rise to an acceleration of crack enlargement and subsequent severe spalling of the CrN coating.

On the Critical Assessment into Damage Behavior of a WC–Co Hard Metal Alloy Used in the Form of Rock Drill Bits

Cemented carbide possesses a good combination of wear resistance, strength and toughness. Therefore, it is mainly used as a tool material. During rock drilling and coal cutting operations, the cemented carbide undergoes a complex condition which limits the service life. It has been an interesting area of research to characterize different wear mechanisms in various working environments. The durability of the cemented carbide has been tested after using it for rock drilling, coal cutting and laboratory wear testing. The present work deals with rock drilling experiments. Granite samples were drilled by using three different grades of cemented carbides (possessing 5, 10 and 15% cobalt) based twist drill bits. All the experimental parameters were kept the same for each sample. After drilling, suitable samples of worn-out cemented carbides were prepared for examining under field emission scanning electron microscope and energy-dispersive spectroscopy. A critical characterization of wear mechanisms was performed. An attempt was made to identify wear behavior among the three grades of cemented carbide.

Effect of High Temperature Aging on Wear Resistance of a High-Nitrogen Stainless Steel

The wear resistance of a Cr19Mn19Mo2N0.7 stainless steel treated by solution treatment 1160°C for 6h then aging at 900°C for different times is investigated in this paper. Microstructures are analyzed using optical microscopy (OM) and scanning electron microscopy (SEM). A fingerprint nitride (Cr2N) structure is formed during aging, which first nucleates within ferrite laths and along the austenite grain boundaries, and then grows into austenite with increasing aging time. It is shown from the laboratory wear test that the optimum wear resistance is obtained through a solution treatment at 1160°C for 6h and aging at 900°C for 3h, which is mainly attributed to a moderate amount of fingerprint nitrides formed within ferrite laths.

Improvement of the useful life of the machining tool with the carbonitrides multilayer system

Multilayer effect was studied systematically on the carbon-nitride system and its effect on the flank wear of cutting inserts. In this sense, tungsten carbide (WC) inserts were used as substrates to improve their tribological properties. The heterostructure coatings were grown via reactive r.f. magnetron sputtering technique by methodically varying the bilayer period (Λ) and the bilayer number (n) while maintaining constant the total coating thickness (~ 3 μm) of the films. The heterostructures were characterized by transmission microscopy (TEM), and the wear tests were supported by scanning electron microscopy (SEM), and laser interferometry. The results showed that the increase of (n) produced a significant increase of the wear resistance in both laboratory wear tests and in real wear tests. In summary, these results encourage the use of the [TiCN/TiNbCN]n system as coatings for machining tools with a drastic enhancement of the wear life. This work has seldom been addressed in literature focused on the tribological properties of the carbon-nitride system.

High-stress abrasion of wear resistant steels in the cutting edges of loader buckets

Abstract To simulate the wear behavior of the cutting edge of the mining load-haul-dumper bucket, high-stress abrasion laboratory wear tests were conducted and compared to the in-service tests. The effects of test parameters and different abrasives on the wear rates and wear mechanisms of wear resistant steels were studied using the high-speed slurry-pot with a dry abrasive bed (dry-pot) and in the actual in-service use as a cutting edge. The laboratory wear tests produced results that are well comparable with the in-service case observations. Especially at the higher sample rotation speed with granite as an abrasive, the wear rates were quite similar as determined from the cutting edge of a loader bucket that had been used in a mine.

Comparison of laboratory wear test results with the in-service performance of cutting edges of loader buckets

The in-service cutting edge of a mining loader bucket was investigated and its wear behavior compared with samples tested in the laboratory to assess how well the wear testing methods correlate with the in-service conditions. The examined in-service cutting edge of a bucket made of a wear resistant steel had been run in an underground mine with quarry gravel. The wear behavior of the cutting edge was simulated in the laboratory scale with several application oriented abrasive and impact-abrasive wear testing methods. In addition to the contact mode, high loads, large abrasive size, abrasive type, and the comminution of the abrasive formed the basis for the design of the laboratory experiments. The wear surfaces and cross-sections of the original cutting edge and the test samples were characterized, and the wear behaviors were compared with each other. Work hardening of the steels occurred in all cases, but the amount of plastic deformation and the depth of the wear scars varied.

An approach to increasing the service lifetimes of nitrided dies for aluminium hot extrusion: A case study

In this investigation we studied the relationships between the design of dies for aluminium hot extrusion, the contact pressures on the die's bearing surface, the length of the bearing surface, the quality of the nitrided layer and the service lifetimes of the dies. Four nitrided dies for Al hot extrusion with a specific die design were selected to outline the approach for increasing their service lifetimes. The different die designs resulted in different contact-pressure distributions on the die's bearing surface and, consequently, in different service lifetimes. The relative values of the contact pressures, i.e., their higher or lower values with respect to the reference die, were assessed in terms of the observed wear patterns on the nitrided samples previously obtained during laboratory wear testing. The proposed approach makes it possible to optimize the geometry of the extrusion dies, which can, together with the optimization of other technological parameters, result in a prolongation of the service lifetimes of the dies.

Tribological Properties of CrAlN and TiN Coatings Tested in Nano- and Micro-scale Laboratory Wear Tests

We investigated the tribological properties of CrAlN and TiN coatings produced by electron beam plasma-assisted physical vapor deposition by nano- and micro-scale wear tests. For comparison, we also conducted nano-indentation, nano-scanning wear tests, and pin-on-disk tribotests on uncoated M2 steel. The results indicate that, after nano-scale sliding tests against diamond indenter and pin-on-disk tests against ceramic alumina counterface pins, the CrAlN coating presents superior abrasive wear resistance compared to the TiN-coated and uncoated M2 steel samples. Against aluminum counterface, aluminum is more prone to attach on the CrAlN coating surface compared to TiN coating, but no apparent adhesive wear was observed, which has occurred on the TiN coating.

Characterization of gasoline soot and comparison to diesel soot: Morphology, chemistry, and wear

Soot from gasoline turbocharged direct injection (GTDI) engines and diesel engines, from exhaust and extracted from oil, were characterized by XRF, XPS, Raman spectroscopy, HRTEM, and Soxhlet extraction followed by GC–MS. Laboratory wear tests with drains and supernatants were also conducted. GTDI soot had less carbon content than diesel soot and can have different PAHs associated with it. GTDI soot extracted from oil either showed the turbostratic structure typical of diesel soot, or appeared sludge-like and decomposed under the TEM beam. The different morphology and chemical composition of GTDI soot from diesel soot can lead to changes in the polarity and hardness of the soot particles and affect the wear mechanism in GTDI and diesel engines.

The influence of copper ore lithology on the grinding media wear

The paper presents results of investigations aimed to find relationship between grinding media wear rate and lithology of ores processed in copper production. Laboratory wear tests of grinding media were carried out for “pure” lithological components, natural copper ores and artificial mixtures prepared in the laboratory. Test samples were characterized in terms of lithology, and the results were used for interpretation of results of grinding media consumption. Based on the laboratory tests results a new wear function of grinding media consumption related to lithology of ores was established.

LOAD DEPENDENT WEAR CHARACTERISTICS OF POLYMER-METAL SLIDING

ABSTRACTIn tribological applications, such as sliding bearing, polymers tends to wear morequickly than indicated in laboratory wear tests. The reason for this discrepancy hasbeen attributed to the effect of loading conditions. In the current study, the influenceof loading mode on the wear characteristics of polyamide (PA66) against steelcounterpart was investigated in dry and wet sliding conditions. The polymer wastested under different static and cyclic loading conditions in order to provide acomprehensive understanding of its wear behavior. All tests were performed usingreciprocating pin-on-plate tribometer which was constructed to perform wear testsunder constant and cyclic loads at constant sliding speed. There was consistentevidence of the effect of loading mode on the wear behavior. At cyclic load, thepolymer shows significant increase in wear rates than those found under constantload. Furthermore, under wet sliding, the polymer showed generally higher wearrates compared to dry tests.

Increasing of Service Times of Nitrided and CrN Coated Dies for Al Hot Extrusion

The main reasons for decreased service times of selected nitrided and CrN coated dies were revealed and explained. Results of analysis of wear on industrial dies were combined with results obtained in laboratory wear tests. The main influential parameters in this study refer to contact pressure, die design, length of bearing surface, quality of nitrided layer, surface preparation prior coating and maintenance. It was found that lower quality of nitrided layer in combination with short bearing surface and occurrence of increased contact pressure close to exit edge of bearing surface can considerably decrease die service time and that appropriate shaping of die contours around inlet and outlet areas of bearing surface has decisive influence on die service time.