Surface Wear Characteristics Research Articles

Assessment of wear characteristics, longevity and stiffness of Essix-type retainers

ObjectiveTo compare four commercially available Essix-type retainers in terms of longevity, wear characteristics, stiffness and their range of rigidity.Materials and methodsAn in vitro study was conducted at Queen Mary University of London. Four groups of thermoplastic materials were included: Duran (PETG), Essix C + (Polypropylene), Vivera and Zendura (Polyurethane). A working typodont was fabricated to evaluate surface wear characteristics using a wear machine with a customized jig. Retainers were measured for tensile test, and water absorption was measured at five different time points up to 6 months after initial immersion in two different physical states and two different solutions. Hydrolytic degradation was also evaluated using FTIR spectroscopy.ResultsEssix C + was the most flexible retainer with Vivera the stiffest material. Zendura and Essix C + had the most surface wear (413 μm ± 80 and 652 μm ± 12, respectively) with absorption rates of up to 15 wt% in artificial saliva occurring with Zendura. Only Essix C + displayed signs of degradation following water absorption.ConclusionsAll materials had characteristic levels of flexibility and were susceptible to water absorption. Duran 1.5 mm performed similarly to Vivera in relation to stiffness and wear properties. While Zendura and Vivera have similar chemical structures, they exhibited differences concerning wear resistance and water absorption. Further clinical research evaluating the clinical relevance of these laboratory findings is required.Clinical relevanceCharacteristic patterns of wear and rigidity of four commercially available Essix-type retainers were observed. This information should help in the tailoring of retainer material on a case-by-case basis considering treatment-related factors and patient characteristics including parafunctional habits.

Material deformation mechanism of lamellar twined high–entropy alloys during machining

The effects of sample structure and tool geometry are studied under cutting simulation to verify the deformation, removal mechanisms, and subsurface defection of lamellar twined CoCuFeNiPd alloys. These findings suggest that the twin boundary spacing (TBS) and twin inclination angle (β) are the main determinants of surface wear characteristics and cutting-induced surface harm. The maximum cutting force achieved with TBS = 8a and β = 90°. The high friction coefficient with the sample has TBS = 8a and β = 90°, showing that the tool’s moving in the substrate is strongly restricted. Furthermore, the surface topography is not sensitive to the TBS and β. The best-machined surface is achieved with TBS = 3a and 4a under twin inclinations of 0° and 30°. The effect of edge radius (R), rake angle (γ), and clearance angle (α) on the deformation behavior is examined. The negative of γ, small α, or larger R results in a higher cutting force, a worse subsurface, and a lower cutting pile-up height. With a positive γ, a large α or small R has a larger average friction coefficient, which implies a higher resistance rate. The tool with a smaller R or positive γ can improve the machined surface’s smoothness.

Investigating surface wear characteristics of single-crystal SiC based on metal electrochemical corrosion

Aiming at the environmental pollution of the polishing solution in chemical mechanical polishing, this study introduces a chemical mechanical polishing technique for single-crystal SiC based on metal electrochemical corrosion. The wear properties of the SiC C-surface, as influenced by different materials on grinding balls (Cu, Fe, Al, and Al2O3), and different solutions (KCl, Na2SO4, Fenton, and H2O), were examined through wear experiments to elucidate the material removal mechanisms involved. The experiments demonstrated that the most significant wear marks, with a peak cross-sectional area of 46.89 μm2, were obtained when the C-face of SiC was ground with Al-paired grinding balls in an Na2SO4 electrolyte solution. Energy dispersive spectroscopy analysis of the wear debris revealed an O elemental content of 11 %, and X-ray photoelectron spectroscopy analysis indicated the existence of SiO2 and Al2O3 oxides. Subsequently, the effects of Na2SO4 solution concentration and pH on the wear pattern of the C-surface were investigated. The largest wear cross-sectional area (approximately 50 μm2) was observed when using an Na2SO4 electrolyte solution with a concentration of 1.25 mol/L at a pH of 9 in an alkaline solution. The proposed mechanism of material removal in single-crystal SiC via metal electrochemical corrosion involves the Al metal acting as a cathode. This causes galvanic coupling corrosion, generating a corrosion current, which subsequently induces oxidation of the SiO2 oxide layer on the anode SiC surface. The oxidized layer is then mechanically removed.

Frictional behavior and micro-damage characteristics of rough granite fractures

Natural faults or discontinuities in general are usually rough at different scales, and the roughness of fault surfaces plays a dominant role in determining the mode of sliding (stable or unstable). Understanding the frictional behavior of rough fractures is important for investigating the mechanics and nucleation of earthquakes, and other dynamic geo-hazards such as induced seismicity and fault slip rockburst. We perform direct shear tests on rough granite fractures to investigate the shear behavior, microscopic asperity damage and surface wear characteristics under different normal stresses (10 to 40 MPa). We then compare our test results with those obtained using ground saw-cut fault surfaces. Results indicate that stick-slip occurs on all the rough fractures during the sliding stage, and the amount of stress drops and fault gouges tends to increase with normal stress. The peak friction coefficient is much higher than that of ground fault surfaces, while the steady-state friction coefficient is comparable with that of the ground surfaces. We identify three different scales of brittle fractures, which are considered to be closely related to the stick-slip sliding, namely shear-off of asperities, fracturing of the survived asperities and off-fault tensile fractures propagating into the host rock. The micro-damage of the post-shear surface occurs in the form of powder-sized gouge, micro-cracks and grain edge wear; and the micro-crack number, maximum length and aperture tend to increase with increasing normal stress. Influence of different fault types (rough fractures, ground saw-cut surfaces and gouges) on the stress drop is not very discernable, which is partly because that stick-slip is highly susceptible to different loading conditions. Friction drops for different fault types are found to be clustered around 0.1 but lower than 0.3 below 50 MPa normal stress, which also depend on the loading conditons (e.g., stiffness). Our study contributes to a better understanding of the mechanics underlying the dynamic geohazards (earthquakes, induced seismicity, fault slip rockburst) which are associated with the unstable shear failure on rough faults or fracture surfaces.

Study on Sliding Wear Characteristics of Non-Gaussian Rough Surface in Mixed Lubrication

Under mixed lubrication, when there is direct rough contact between two contact surfaces, surface wear occurs, altering surface morphology, which in turn changes their lubrication state. The tribological performance of materials can be improved with in-depth understanding of the coupling mechanism linking surface wear and lubrication. A numerical model was established to predict the lubrication state and wear characteristics of the surface wear process based on non-Gaussian surface reconstruction technology and a mixed elastohydrodynamic lubrication sliding wear model. The evolution of wear characteristics in Gaussian and non-Gaussian rough surfaces was investigated, and the effect of surface skewness and kurtosis on lubrication and wear characteristics was discussed. The results indicated that as the wear cycle increases, the contact area and contact load ratios of the rough surfaces decrease before gradually stabilizing, while the coefficient of friction and maximum flash temperature rise and then gradually decrease. Increasing surface skewness and kurtosis increases the probability of wear, leading to increased accumulated wear, friction coefficient, and maximum flash temperature rise.

Studies on wear characteristics of surface hardened tractor drawn rotavator blade

In agriculture, seed bed preparation is the prime operation in crop production schedule.Tillage operation is performed to acquire a seed bed with improved soil health that is free from weeds and insect pest and for this purpose normally land is ploughed by using plough and cultivators. But these implements invert only the upper layer of soil, without proper mixing of soil. Therefore, additional field operations using rotavator, harrow etc. is essential for good soil health. The rotavators do simultaneous ploughing and harrowing. By using rotavator time can be saved upto 30-35% and the cost of operation may reduce by 20-25%. But by having advantages in rotavator their has been emerged as a serious problem of abrasive wear in rotavator blades, because the material used are softer than the natural abrasives in the soil. Due to this wear the operating and maintenance cost of rotavator increased, hence lowers its productivity. So their is a need to give a proper treatment to soil engaging parts which reduce the rate of wear. But the rotavator blades which available in the market are not properly heat treated so the wear rate is considerably more as compare to the heat-treated blades. So, there is a need to study wear characteristics of rotavator blades.

Structural transformation and strain localization at twin boundaries in Al0.4CoCrFeNi high-entropy alloy

Surface nanotribological properties and subsurface damage of Al0.4CoCrFeNi high-entropy alloy during the nano-scratching processes are investigated using molecular dynamics. The results show that the surface wear characteristics and scratching-caused surface damage significantly depend on the crystallographic orientation, spacing and inclination angle of the twin boundary. For the variation of crystallographic orientation, the largest friction coefficient belongs to the crystallographic orientation [001], indicating that the movement of the indenter in this substrate is most restricted. The microstructure evolution reveals the formation of Lomer-Cottrell and Hirth dislocation locks because of the distinctness of angle between various slip systems. Both the Hall–Petch and inverse Hall–Petch relationships are observed for the difference of twin boundary spacing, and the maximum indentation force is achieved with a tilt angle of 0° resulting from the various interactions among the dislocations and twin boundaries. The microstructure evolution and the atomic flow are greatly dependent on the spacing and the inclination angle of twin boundary, where the twin boundary migration is the significant factor. Furthermore, the surface morphology is distinct between workpieces due to the elastic recovery at the surface, nucleation and slipping of dislocation, which implies that the wear volume depends on the material microstructure.

Influence of different corrosive environments on friction and wear characteristics of lubricated wire ropes in a multi-layer winding system

Corrosion, friction and wear of wire ropes always exist in multi-layer winding systems. They lead to the lubrication failure and service performance degradation of wire rope. To reveal the tribological properties of wire rope in service, the coefficient of friction (COF), friction temperature rise and surface wear characteristics of wire rope with different lubrication and corrosion conditions were investigated. The experimental results show that friction parameters of the lubricated wire ropes are relatively small, which are obviously affected by the sliding stroke and velocity. The COF fluctuates between approximately 0.15 and 0.28, and the friction temperature rise is reduced to below 7 °C. Additionally, the corrosion solutions degenerate the anti-friction and anti-wear properties of the lubricating grease and oil. The COF and friction temperature rise of the oil lubricated wire rope increase greatly when the rope sample is corroded by sea-water and dilute sulfuric acid solution. The sliding wear mechanism and lubrication stage of the lubricated wire ropes is adhesive wear and boundary lubrication, respectively. Furthermore, dilute sulfuric acid solution is the most harmful to the friction-reduction and wear-resistance of the lubricating grease and oil used for wire rope, followed by sea-water solution and fresh water solution.

The Wear Resistance Characteristics Analysis of the Ball-End Milling Topography Surface

The surface topography has an important influence on the friction and wear characteristics of the contact surface. In this paper, the topography surface after the ball-end milling is taken as the research object, based on the Archard wear model, through the finite element simulation analysis method, the quadrilateral pit topography surface and the ideal smooth surface wear characteristics are compared and analysed, and found that the surface of the quadrangular pit topography has more excellent wear resistance. Then, using the basic principles of the grey system theory, quantitative analysis of the relevance between the real contact area of the topography surface and the surface roughness parameters, it provides a useful idea for the study of friction and wear characteristics of topography surfaces.

Field evaluation of rutting in concrete pavements

Surface wear by studded tires is a primary cause for rutting in portland cement concrete (PCC) pavements, and may, for the pavement sections with high traffic intensities, become a primary factor controlling the length of pavements maintenance intervals. In the present study, PCC pavement field performance with respect to surface wear is examined based on the transverse surface profile measurements performed yearly during first five years of pavements service life. Continuous transverse surface profile measurements have been performed yearly on a 20 km long rigid pavement section in Moscow region, Russia. Based on the measurements, quantitative parameters describing rut depth evolution are obtained and evaluated; the obtained results are discussed in context of previous research findings reported in the literature. The effect of pavement surface wear on the further rutting accumulation rate is examined. The particular attention is also given to the spatial variability of the measured pavement surface wear characteristics, i.e. rut depth and accumulation rate. The implications of the obtained results on the length of rigid pavement maintenance intervals are discussed.

Suppression of Friction-Induced Stick–Slip Behavior and Improvement of Tribological Characteristics of Sliding Systems by Introducing Damping Materials

An experimental study is conducted for friction systems introducing damping components consisting of different materials and different configuration. A number of experiments are performed on a pad-on-disc experimental test rig. Dynamic and tribological analyses are performed to evaluate the effects of different damping components on the stick–slip behavior. The obtained results indicate that friction systems introducing damping components of styrene butadiene rubber (SBR) or Mu-Cu damping alloy (DA) materials effectively reduce the friction-induced stick–slip behavior. The best performance was observed for the SBR damping component with a specific structure. The mechanism of introducing SBR or DA damping components into friction systems to influence the stick–slip behavior is discussed. For the SBR damping component, deformation is the dominant factor to suppress the stick–slip behavior. This is because the larger deformation of damping component could dissipate the vibration energy of friction systems and alleviate severe wear phenomena at the contact interface. For the DA damping components, the main reason for the reduction in stick–slip behavior is that the material has a higher damping capacity. Therefore, damping components of DA material only affect the vibration characteristics and not surface wear characteristics of the contact interface. The purpose of this article is to provide novel insights for the reduction or elimination of stick–slip motion at low speeds in relevant engineering applications.

Erosion Wear Characteristics of Surface Modified Grey Cast Iron by WC–Co–Cr/NiCrBSi Coating Using HVOF Thermal Spray Process

Abstract Pump casings made of grey cast iron (GCI) used in lignite mines for dewatering are subjected to erosive wear and fail catastrophically. An attempt was made to modify the surface of GCI by WC–Co–Cr/NiCrBSi coating using HVOF process for the application under mining conditions. Grey cast iron samples with and without WC–Co–Cr/NiCrBSi coating were subjected to slurry jet erosion tests by varying the impingent velocity and angle under two different pH conditions of 3 and 7 which pertain to the mining environment. XRD characterization was done to identify and confirm phase composition. Eroded surface morphology studies were carried by SEM on both the substrate and coating, which revealed the erosion of GCI surface, predominantly due to ploughing mechanism. In the case of WC–Co–Cr and NiCrBSi coating, at an oblique angle of impact, the material removal from the surface is by micro cutting of the matrix, ploughing, and abrasive mode mechanisms. At normal impingement, the fluctuating stress creates the cracks, which interlink each other to form lips and craters followed by material degradation through fatigue. Performance of WC–Co–Cr coating is found to be better than NiCrBSi Coating.

Tribology in coal-fired power plants

Material wear and degradation is of great importance to the economy of South Africa especially within the mining, agriculture, manufacturing and power generation fields. It has been found that unexpected and high rates of fly-ash erosion occur at certain sections of power plants, this is particularly evident at the Majuba power station. The loss of small amounts of material due to erosion can be enough to cause serious damage and significantly reduce the working lifetime of, for, e.g. hopper liners. This study investigated the long-term solid particle erosion of a range of oxide and nitride-fired SiC-based ceramics and alumina with the aim of reducing erosive wear damage in power plants. This entailed carrying out experimental tests on an in-house built erosion testing machine that simulate the problems encountered in the industry. The target materials were eroded with 125–180 μm silica sand at shallow and high impact angles. The surface wear characteristics were studied using both light and scanning electron microscopy (SEM). The results obtained indicate that the erosion rates of the materials remain fairly constant from the onset. It was found that prolonged exposure to erosion results in the progressive removal of the matrix and subsequent loss of unsupported SiC particulates. The fact that the particles were relatively small did not have a significant effect on the erosion rate. This would explain the observed constant rates of erosion for longer periods. These behaviours can be further explained in terms of the composition and mechanical properties of the erodents and target ceramics.

Wear behavior of nitrocarburized JIS SKD61 tool steel

The surface wear characteristics of the nitrocarburized JIS SKD61 tool steel were investigated. The ferritic substrate (FS) JIS SKD61 tool steel as received was pretreated in quenching and tempering processes to obtain the tempered martensitic microstructure. Specimens were then nitrocarburized for 1, 3, and 5 h. The chemistry, microstructure, and hardness of the nitrocarburized coatings were analyzed. Wear behavior was examined on a block-on-roller wear tester under unlubricated conditions. The results have shown that white layers were predominantly composed of the ϵ-phase iron nitrides dispersed with γ′-phase, and a large amount of nitrogen and carbon trapped in the ferrite phase was observed in the diffusion layer for FS. The nitrocarburizing treatment increased the surface roughness, hardness and the friction coefficients of the specimens. Wear contact pressures and nitrocarburized holding time also affected the friction coefficients of the nitrocarburized specimens. In this study, both the FS and the tempered martensitic substrate (TMS) specimens treated with subsequent nitrocarburizing process have shown significant improvement of the wear resistance. Wear behaviors of the specimens nitrocarburized for 1, 3, and 5 h did not vary significantly.

Friction and Wear of Surface Modified Rollers in High Vacuum. Comparison of the Results in Two cylinder Test and Gear Test.

To clarify the friction and wear characteristics of surface modified rollers in vacuum, two cylinder test was carried out under non-lubricating condition in high vacuum less than 2 × 10-3 Pa. Thermal diffusion after Sn plating (Sn), electroless Ni-P plating (Ni-P) and sulfurizing were employed here. Friction coefScient of the surface modified rollers was smaller than that of non-coated rollers. The initial friction coefficient of Sn plated rollers increased under low contact pressure, where wear particles were transferred onto the frictional surface, while the friction coefficient decreased when surface modified layer worn uniformly. The sulfurizing contributed to the reduction of the initial friction. The friction behavior of Ni-P plated rollers indicated the most stable in all test rollers. In addition, the relation between the test results in the two cylinder tests and the previous gear tests in high vacuum using the same surface modification treatment as employed in these two cylinder tests was evaluated. The initial friction in the two cylinder test was greater than that in the gear test in the cases of non coat, Sn and Ni-P. However, where sliding distance was large enough, the friction behavior in the gear test was similar to that in the two cylinder test.

Friction and Wear Characteristics of Surface Modified SUS440C Spur Gears in High Vacuum.

In order to investigate the friction and wear characteristics of surface modified spur gears made of stainless steel SUS440C in high vacuum, gear tests were carried out under non-lubricating condition in vacuum to be on the order of 10-4 Pa. In addition, dynamic load on spur gear teeth with surface modified layer was evaluated. Electroless Ni-P alloy plating (Ni-P plating), sulfurizing and Sn plating with thermal diffusion (Sn plating) were employed. From the gear tests, the following results were obtained. (1) The friction coefficient of the surface modified gears was smaller than that of the non-coated gears. (2) The initial friction of Sn plated gear increased under low pressure and low rotational speed conditions. After Sn plated layer wore uniformly, the friction coefficient was the smallest by the lubricating effect of thermally diffused layer of Sn. (3) The sulfurized layer contributed to the reduction of initial friction. However, the friction behavior of sulfurized gear was the same as that of non-coated gears, after the sulfurized layer wore completely. (4) Wear amount and tooth profile error of Ni-P plated gears were the largest of all the test gears.

Lithological and Structural Controls on the Surface Wear Characteristics of Glaciated Metamorphic Bedrock Surfaces: Ossian Sarsfjellet, Svalbard

Although there is an established relationship between geological structure and the morphology of certain glacial erosional landforms, the role of lithology is less clear. This is particularly true of the surface wear characteristics of glaciated bedrock. In order to examine this relationship, the surface wear characteristics of eight recently deglaciated metamorphic bedrock slabs in the Kongsfjorden area of Svalbard were mapped and recorded using detailed “micro‐maps.” Features recorded included lee‐side fracture surfaces, lee‐side cavities, and the location and depth of open joints and quartz veins. On schist, glacial erosion is favored by situations where ice movement is parallel to the trend of the bedrock foliation. In these situations, cavities may be elongated in the direction of ice flow. On more homogeneous lithologies such as marble, cavity formation is suppressed and more uniform glacially abraded rock surfaces develop. On all the metamorphic rocks examined, glacial abrasion is favored in situations where bedrock foliation is normal to ice flow. The structure of the parent bedrock, especially the orientation of foliation, exerts a strong influence on the surface wear characteristics of glaciated bedrock slabs and on the location of subglacial cavities. Geological structure therefore has the potential to influence rates of ice flow across bedrock surfaces.

Role of chromium carbide in tungsten carbide based hard composites

The surface wear characteristics of the nitrocarburized JIS SKD61 tool steel were investigated. The ferritic substrate (FS) JIS SKD61 tool steel as received was pretreated in quenching and tempering processes to obtain the tempered martensitic microstructure. Specimens were then nitrocarburized for 1, 3, and 5 h. The chemistry, microstructure, and hardness of the nitrocarburized coatings were analyzed. Wear behavior was examined on a block-on-roller wear tester under unlubricated conditions. The results have shown that white layers were predominantly composed of the ϵ-phase iron nitrides dispersed with γ′-phase, and a large amount of nitrogen and carbon trapped in the ferrite phase was observed in the diffusion layer for FS. The nitrocarburizing treatment increased the surface roughness, hardness and the friction coefficients of the specimens. Wear contact pressures and nitrocarburized holding time also affected the friction coefficients of the nitrocarburized specimens. In this study, both the FS and the tempered martensitic substrate (TMS) specimens treated with subsequent nitrocarburizing process have shown significant improvement of the wear resistance. Wear behaviors of the specimens nitrocarburized for 1, 3, and 5 h did not vary significantly.

Characteristic features of wear in tools made of high-speed steels with surface engineered coatings I. Wear characteristics of surface engineered high-speed steel cutting tools

Characteristic features of wear in tools made of high-speed steels with surface engineered coatings incorporating ion nitriding and (Ti, Cr) nitride CAPDP (cathode arc plasma deposition process) coatings were investigated at increased cutting speeds in the vicinity of 50–100 m min−1. The wear kinetics, the change of micro-relief of cutter surface and the depth of the unhardened zone of cutting indexable inserts made of high-speed steels with surface engineered coatings were studied. A significant tool life was found for the surface engineered high-speed steel under the greatest possible localization of thermomechanical effects in the CAPDP coating layer. The application of a surface engineered system composed of a heat resistant high-speed steel T15 (P12M3φ2K5) substrate, with surface modified by ion nitriding and then by CAPDP (Ti, Cr) N coating, provides this result.

Wear characteristics of surface coating for rock engaging tool of construction machinery: Tatsuro Muro and Yoshichika Matsunaga

Wear characteristics of surface coating for rock engaging tool of construction machinery: Tatsuro Muro and Yoshichika Matsunaga