Wear Morphology Research Articles

The roles of theaflavins in reducing dentin erosion

This study aimed to evaluate the effect of theaflavins [TFs] on the process of dentin erosion and investigation the potential mechanism. For erosion kinetics of the dentin, 7 experimental groups (n = 5) treated with 10% ethanol [EtOH] (negative control) are erosion for 1, 2, 3, 4, 5, 6, and 7 d erosion cycles (4 cycles/d). For the effect of TFs on dentin erosion, 6 experimental groups (n = 5) were treated with 1% epigallocatechin gallate [EGCG], 1% chlorhexidine [CHX], 1%, 2%, 4%, and 8% TFs for the 30 s and then subjected to erosion cycles (4 cycles/d for 7 d). The erosive dentin wear (μm) and surface morphology were evaluated and compared by laser scanning confocal microscope and scanning electron microscopy. The matrix metalloproteinase inhibition effects of TFs were investigated using in situ zymography and molecular docking. TFs-treated collagen was investigated by ultimate microtensile strength, Fourier-transform infrared spectroscopy, and molecular docking. Data were analyzed by ANOVA, Tukey’s test (P < 0.05). The TFs-treated groups (7.56 ± 0.39, 5.29 ± 0.61, 3.28 ± 0.33, and 2.62 ± 0.99 μm for 1%, 2%, 4%, and 8% TFs) had significantly lower erosive dentin wear than the negative control group (11.23 ± 0.82 μm), and the effect was concentration-dependent at low concentrations (P < 0.05). TFs inhibit matrix metalloproteinase [MMP]. Moreover, TFs crosslink dentin collagen and cause hydrophilic changes in dentin collagen. TFs preserve organic matrix within the demineralized dentin by inhibiting MMP activity and simultaneously improving collagen’s resistance to enzymes, both of which contribute to preventing or slowing down the progression of dentin erosion.

CFD-DEM coupled calculation of wall wear characteristics during particles flow impacting the wall process

The continuous impact of the particles flow on the wall during industrial bulk material transport can lead to wall wear. In this paper, a physical model of the particle flow impacting the wall at different angles is established, and the wear condition of the particles flow impacting on the wall is studied by using the coupling method of CFD-DEM. Firstly, the accuracy of the erosion model is verified by the existing experimental data. Secondly, the effects of particle incidence angle, particle velocity and particle volume fraction on wall wear are analyzed by numerical calculation. The results show that the mass loss and erosion ratio of the target plate are the largest when the particle incidence angle is between 15° and 30°. When the particle incidence angle is near 45°, the maximum wear depth will appear on the wall surface. The increase of particle impact velocity led to an exponential increase in the mass loss, erosion ratio and wear depth of the target plate, but did not change the wall wear morphology. The particle volume fraction is positively correlated with the mass loss of the target plate. With the increase of particle volume fraction, the change of erosion ratio is more obvious at 90° impact, but has little effect at 45° impact. The change of particle volume fraction has an important effect on the wall wear morphology.

Tool Wear and Surface Integrity of γ-TiAl Cryogenic Coolant Machining at Various Cutting Speed Levels

High-speed machining of γ-TiAl alloy is a significant challenge due to high cutting temperatures. From the perspective of environmental protection and improving tool life, appropriate cooling strategies should be adopted. Compared with dry and conventional flood cooling conditions, the feasibility of machining γ-TiAl in cryogenic LN2 cooling conditions was discussed. The cutting force, tool wear and its mechanism, and surface roughness, as well as sub-surface morphology characteristics, were studied by combining macro and micro techniques. The results revealed that the wear morphology of the rake and flank face under the three cooling media shows different degrees. The crater wear of the rake face is expanded at high speeds and then progresses into more serve flaking and notching wear. The main wear pattern on the flank face is gradually transformed from adhesive wear to diffusion and oxidation wear at high speeds in dry machining. In the LN2 condition, the diffusion of workpiece elements and cutting-edge oxidation were restrained. The wear pattern is still mainly adhesive wear. In addition, cryogenic machining shows significant advantages in reducing cutting force, suppressing heat-affected zone, improving surface quality, and inhibiting micro-lamellar deformation.

Influence of solid-liquid two-phase flow conveying parameters on the elbow wear with and without the swirler

Elbow wear is a considerable threat to the multiphase pipeline transportation industry. The swirler placed upstream of elbows could reduce wear. The dense discrete phase model (DDPM) was used to study the effects of different concentrations, particle sizes, and flow velocities on the wear of elbows with and without the swirler, and the formation mechanism of different wear morphologies was revealed. The mathematical models between conveying parameters and the MWR (maximum wear rate) were established, and the conveying parameters that were most suitable for using the swirler to reduce elbow wear were obtained. The bench test proved that the MWR of the horizontal-horizontal (H-H) elbow, horizontal-vertical (H-V) elbow, and vertical-horizontal (V-H) elbow could be reduced by 51.9%, 35.5%, and 23.2%.

Insight on the in vivo wear characteristics of goat artificial cervical disc implanted for 6 months

Since the prosthesis may suffer overload or extreme motion during the daily activities, some special failure modes may be found in service. In order to give an insight on the in vivo stability of artificial cervical disc, the wear characteristics of goat prosthesis were studied after implanted in goat animal for 6 months. The prosthesis was designed with a ball-on-socket structure under the material combination of PE-on-TC4. The X-ray examination was performed to monitor the in vivo wear process. The worn morphology and wear debris were analyzed in detail by EDX and SEM. The result indicated that goat prosthesis revealed good safety and effectiveness during 6-month in vivo wear test. The wear damage occurred only on nucleus pulposus component with the dominant failure mode of surface fatigue and deformation. The damage distribution and wear severity was seriously uneven with a trend that the closer to the edge, the more severe the wear. For example, slippage phenomenon caused a wide and curved severe ploughing damage on the edge. Three kinds of debris were found including bone debris, carbon-oxygen compound debris and PE wear debris. Both bone debris and carbon-oxygen compound debris came from superior endplate while PE wear debris came from nucleus pulposus. The debris proportion for endplate was 82% for bone debris, 15% for carbon-oxygen compound debris and 3% for PE debris while for nucleus pulposus it was 8% for carbon-oxygen compound debris and 92% for PE debris. The size range of PE debris for nucleus pulposus was 0.1–100 μm, with an average size of 9.58 ± 16.34 μm. For the bone debris of endplate components, the size range was 0.1–600 μm, with an average size of 49.18 ± 94.54 μm. After wear test, the equivalent elastic modulus of nucleus pulposus increased from 28.55 MPa to 38.25 MPa. The results of FT-IR spectrum showed that the functional groups on the surface of polyethylene have not changed significantly after wear test. The results indicated that there were some differences in wear characteristics of wear morphology and wear debris between in vivo wear and in vitro wear.

Study on Wear Resistance Evolution of Cold-Rolled Strip Flatness Meter Surface-Strengthened Layer

Seamless flatness rollers are the core equipment for cold-rolled strip flatness detection. The change in wear resistance of the roller surface-strengthened layer has important guiding significance for the prediction of the roller surface life. The experimental results of the five rounds of friction and wear testing show that the volume–wear rate of the original roller surface is only 1.85 × 10−6 mm3 (N·M)−1. After the first grinding, the wear resistance of the roller surface decreased and the wear rate was approximately 2.76 × 10−6 mm3 (N·M)−1. After the second grinding, the wear morphology, wear rate and wear resistance of the samples in each round showed little difference. The average wear rate in the last three rounds of the test is 3.56 × 10−6 mm3 (N·M)−1 and the wear resistance is significantly lower than that of the previous two rounds of the test. The calculation shows that the original surface wear resistance is 32.92% higher than that of the surface after the first grinding, and the average wear resistance of the surface after the first grinding is 22.59% higher than that of the surface after the second, third and fourth grinding. With long-term use and repeated grinding repair, the roller surface will show a trend of wear resistance decline. When the wear resistance decreases to a certain degree, it will reach a stage of stability. These phenomena provide regular and quantitative references for the study of the life prediction of flatness meter rollers.

Failure analysis of slurry TBM discharge pipe in complex strata combined with wear and vibration characteristics

The slurry TBM circulation system plays a crucial role in supplying the slurry to the excavation face and conveying the cut rock particles to the ground. Rock particles in excavated materials will cause damage and failure of slurry discharge pipelines, which seriously restricts the efficiency of slurry TBM tunneling. In this paper, the two major behaviors of wear and vibration that induce slurry discharge pipelines failure are systematically investigated based on a water delivery tunnel located in Beijing. The wear morphology of typical pipes is studied combining the measured wear data and CFD-DEM coupling simulation. The time–frequency characteristics of slurry discharge pipe in different strata are measured and analyzed. Furthermore, the variation of time–frequency characteristics with the decrease of pipe wall thickness is investigated, a multi-parameters early warning methods based on vibration characteristics is proposed for detecting pipe wear. The results show that The CFD-DEM coupling method and Archard wear model can accurately determine the location of the maximum wear point of various pipes conducive to local thickening of pipes. The elbow pipe joints are prone to fatigue damage and have a high risk of slurry leakage during transport of large-sized particles. When the pipeline is severely worn, the interaction between the rock particles and the worn wall causes local elastic deformation, resulting in a high frequency response of 50–150 Hz and a rapid increase in the kurtosis K.

Analysis of tool wear and chip morphology under different machining environments in turning operation

A large supply of coolant can raise machining costs and be potentially harmful to the environment. Therefore, other techniques are needed to solve the issues that arise while using coolant. In this study, the effects of cutting speed, feed, depth of cut, and lubrication conditions (dry: no lubrication, cotton seed oil-based nano fluid: alumna is used during machining). The surface roughness and cutting force were investigated during the turning of 304 stainless steels with minimum quantity lubrication (MQL). L9 orthogonal array was used for the experiments. The findings show that dry may be replaced by alumina nanofluids with MQL. In order to assess the machinability of hardened AISI 304 steel, cutting force and surface roughness are taken into account as technological performance criteria. Al2O3 is combined with cotton seed oil for creating nanofluid sample.

Experimental Study on Titanium Alloy Cutting Property and Wear Mechanism with Circular-arc Milling Cutters

Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness. Nonetheless, these properties also cause general problems in the machining, such as processing inefficiency, serious wear, poor workpiece face quality, etc. Aiming at the above problems, this paper carried out a comparative experimental study on titanium alloy milling based on the CAMC and BEMC. The variation law of cutting force and wear morphology of the two tools were obtained, and the wear mechanism and the effect of wear on machining quality were analyzed. The conclusion is that in contrast with BEMC, under the action of cutting thickness thinning mechanism, the force of CAMC was less, and its fluctuation was more stable. The flank wear was uniform and near the cutting edge, and the wear rate was slower. In the early period, the wear mechanism of CAMC was mainly adhesion. Gradually, oxidative wear also occurred with milling. Furthermore, the surface residual height of CAMC was lower. There is no obvious peak and trough accompanied by fewer surface defects.

Evaluation of microstructural, tribological and tensile characteristics of AA7075 surface composites fabricated through friction stir process

Superior wear resistance and a high level of tensile strength in piston ring materials are achieved using AA7075 surface composites (SCs) that are fabricated by reinforcing the steel slag (SS) particulates through proper selection of friction stir process (FSP) parameters using the multipass technique. The optical structure elucidates that fine and equi-axed grains are ascertained in the stir zone of the processed region, and by increasing the number of passes from one to three, a homogenous dispersion of particulates and a reduced grain size (9 µm) is obtained. In particular, a clear and defect-free interface is prominent on the resulting composite surface. Field emission – scanning electron microscopy (FESEM) identifies the dispersion of reinforcements, while X-ray diffraction (XRD) technique and energy dispersive spectroscopy (EDS) mapping confirm the existence of reinforcing elements. The Orowan strengthening effect and reduced oxygen content around the SiO2 and CaO elements in the three-pass FSP SC specimen tend to increase its load-bearing capacity and result in superior hardness (353.3 VHN) and tensile strength (792.6 MPa). However, the same specimen exhibits a reduced percentage (%) elongation due to multiplied fragmentation of reinforcements, which eventually restricts the plastic movement of the AA7075 matrix. The SEM fracture morphology indicates that failure occurred through a combination of ductile and brittle modes. Furthermore, the SC specimen with two passes prominently decreases the wear rate (333 × 104 mm3/m), which can be attributed to the commendable trilayer formation, and the worn morphology indicates the abrasive wear was the dominant wear mechanism. This fabricated specimen with high-strength characteristics can be beneficial for design engineers. During piston ring design, an increased level of the factor of safety can be achieved.

Research on the wear characteristics of magnetorheological fluid in sealing interface considering the interaction between surface roughness and magnetic particles

In this paper, the influence of magnetorheological fluid (MRF) on the wear mechanism of sealing pairs under different surface roughness is studied from the perspective of theoretical analysis and experimental verification. Simulation analysis shows that the coupling of roughness and microparticles changes contact pressure and frictional stress distribution on O-ring acted by asperities. Combined with wear morphologies, it is further proved that roughness affects the movement pattern of particles in the sealing gap, thereby determining the tribodynamic behavior of MRF. Specifically, the roughest sample shows low friction coefficient and best wear resistance, while the smoothest sample exhibits worse tribological performance. The above analysis is the reason for the sealing wear under MRF is completely opposite to that of base oil.

Influence of Cr on the Surface Properties of the Micro-Textured WC+Co Alloy Coating

In this paper, we investigated the effect of Cr on the surface properties of the micro-textured WC+Co alloy coating. An interactive test was designed that considered the parameters of an AlSiTiN coating and an AlSiTiN–AlCrN double coating. Using hardness and phase composition as evaluation criteria, the influence of Cr on the mechanical properties and microstructure of the coating surface was analyzed. A friction and wear test platform was formed to explore the mechanism of the Cr influence on the friction performance and wear state of the coating surface. The results show that Cr leads to the generation of the α-Cr phase particles in the surface structure of the specimen. They easily combine with C to form carbides, which improve the coating hardness; the atomic radius of Cr is smaller than that of Al, so it can dissolve in AlN. This induces lattice distortion, changing the phase composition in the structure; the coating with Cr exhibits better surface friction performance and wear morphology, simultaneously generating enhanced mechanical vibrations.

Wear behaviour of novel copper alloy as an alternative to copper-beryllium

Copper beryllium age hardenable alloys (Cu–Be) are widely used and appreciated for combining exceptional mechanical and electrical properties. However, the toxicity of these alloys pushes the scientific community to develop alternative alloys. Cu–Ni–Sn alloys are already used in aeronautics and the oil industry to replace Cu–Be when good tribological behaviour is required. Recent studies showed that Cu–Ti alloys, age hardenable, have a higher yield stress and elongation than Cu–Ni–Sn alloys and can approach the mechanical resistance of Cu–Be. In this research work, the wear mechanisms governing the tribological behaviour of a new copper alloy (containing alloying elements such as titanium, nickel or tin) as an alternative to the beryllium containing copper alloys were investigated.Tribological tests under dry conditions were carried out by sliding an alumina ball against three different copper alloys disks applying different loads and during a different number of cycles. Wear volumes were quantified by confocal microscopy while wear morphology and microstructural changes at the surface and subsurface were analysed by SEM and FIB cross-sections. Several wear mechanisms were identified including plastic deformation followed by the build-up of a third body. Friction transitions were measured during sliding as a consequence of the third body formation. The chemical and mechanical properties of the third body were material dependent and determined the wear behaviour of the different copper alloys.

Tribo-corrosion interaction of the parallel steel wires in the suspension bridges

AbstractThe effect of contact load and relative displacement on tribo-corrosion interaction of parallel steel wires of main cable in the suspension bridge was investigated in this study. A self-made tribo-corrosion test bench was employed to conduct tribo-corrosion tests of parallel steel wires in 3.5% (wt%) NaCl solution and deionized water under different contact loads and different relative displacements. The friction coefficient and wear coefficient of wires were presented. Electrochemical corrosion behavior (Tafel polarization curves, Nyquist diagram, and equivalent circuit diagram) was characterized by electrochemical analyzer. Wear morphology was observed by scanning electron microscope. Wear volume loss and corrosion-wear interaction were quantitatively demonstrated by high-precision weighing balance. The results show that the electrochemical corrosion ability of the steel wires increases with the increase of the contact load or relative displacement. The increased contact load or relative displacement increases the volume loss of corrosion-wear and pure wear, but decreases the wear coefficient. The wear mechanisms in 3.5% NaCl solution are adhesive wear, abrasive wear, and corrosive wear as compared to adhesive wear and abrasive wear in deionized water under different contact loads. The wear mechanisms of parallel steel wires are slightly different under different relative displacements. But the main wear mechanisms are similar to that under different contact loads. The interaction effects of corrosion and wear produced by the contact load and relative displacement are all the synergistic effects.

Influences of abrasive particles on tribological behaviours of rotary vane steering gear seals under oil

The wear particles often cause the abnormal wear processes to the rotary vane seals, which lead to seals failure and dropping hydraulic oil pressure, and eventually result in losing of the function of rotary vane steering gear. Clarifying the friction and wear mechanisms between the vane seals and the cylinders and extracting their key wear characteristics are the keys to extend the service life and realize intelligent fault diagnosis of the rotary vane steering gears. Different kinds of hydraulic oils mixed up with different sizes of iron particles were chosen to investigate the abrasive particles on the wear behaviours between the polyurethane polymer and carbon steel specimens. The wear characteristics such as coefficients of friction (COF), wear morphologies, frictional-induced vibration signals were examined and analyzed synthetically. The results showed that the coefficients of friction, wear morphologies, surface roughnesses and vibration signals increased as a function of the iron particle sizes, which indicated that the wear state was gradually worsening. The three-body friction and wear mechanisms were disclosed clearly. There was a certain mapping relationship between the wear characteristics and wear states, and sensing the tribological information between the rubbing pairs, including coefficient of friction, abrasive particle size in hydraulic oil, wear morphology, vibration signal and other characteristics, was a potential and effective way for evaluating or predicting the wear states or failure modes of rotary vane steering gear seals. This study provides a theoretical basis for revealing the friction and wear mechanisms of ship rotary vane steering gear seals, and is useful for accomplishing their intelligent monitoring and fault diagnosis.

Modeling of Dynamic Cutting Force considering Flank Wear and Analysis of Tool Wear Mechanism in Milling 508III Steel

508III steel is widely used to manufacture the key components of water chamber head of nuclear island evaporator because of its excellent performance. Due to the large milling parameters and their high strength, hardness, and adhesion, cemented carbide tools are subjected to large cyclic mechanical load. Serious tool wear and low service life have become more prominent problems in the cutting process. Therefore, the research on the dynamic cutting force and wear mechanism of cemented carbide tools for milling 508III steel is attracting more and more attention. In this study, based on the theory of cutting mechanics and the force balance condition of circular tool cutting unit, the cutting force model under ideal condition was established. On this basis, the tool dynamic cutting force model considering flank wear was constructed. The tool wear experiment of milling 508III steel was carried out under different cutting parameters, and the change curve of tool wear life and the actual dynamic cutting force at different cutting time were obtained. And the accuracy of the established dynamic cutting force model was verified. Scanning electron microscopy and energy dispersive X-ray spectroscopy were used to analyze the wear morphology and mechanism of cemented carbide tools. The research findings can are of great significance for revealing the tool failure mechanism of milling water chamber head, reasonably selecting machining parameters, and improving the machining quality and efficiency of nuclear power parts.

Sliding wear behaviour of salt bath nitrided 316LN austenitic stainless steel

The wear behaviour of AISI 316LN austenitic stainless steel has been studied by varying the duration of nitriding. AISI 316LN steel was nitrided using salt bath nitriding which consist of a mixture of 70:30 ratio of alkaline cynates and carbonates. Nitriding was carried out for two time durations namely 60 min and 100 min. Pin-on-Disc wear test were carried out for both the untreated and treated sample at room temperature. The wear parameters were changed to understand the wear mechanism of AISI 316LN steel along with the nitrided sample by varying the sliding distance for 250 m, 500 m and 1000 m. Due to the presence of different wear mechanism the rate of wear varies as a function of sliding distance. For untreated sample the wear mechanism was dominant with adhesion, abrasion and plastic deformation. An optical micrograph, X-ray diffraction analysis, wear morphology, hardness measurement and surface roughness were carried out. Due to the presence of compound layer as a result of nitriding AISI 316LN austenitic stainless steel, the mechanism of wear was restricted to abrasive wear. Untreated specimens have more significant wear loss when compared to treated specimen as work hardening and an increase in hardness of wear track resulted in material pull out. Stability of the compound layer is achieved as a result of longer duration of nitriding. Abrasive wear is resisted to a greater extend due the availability of compound layer. AISI 316LN steel which was nitrided for 100 min exhibited a more stable compound layer when compared to the same nitrided for 60 min.

Tribological behaviors of FeCoNiCrAlx sliding against Si3N4 ceramics under high temperature condition

Tribological behaviors are system responses that not only depend on material properties but also hinge on external environmental factors. This work investigated the tribological behaviors of FeCoNiCrAlx (x = 0.1, 0.5, 1) sliding against Si3N4 ceramics under high temperature conditions. According to experimental findings, the tribological properties of FeCoNiCrAlx were enhanced as the Al element content increased, particularly FeCoNiCrAl1 could resist the material softening under high-temperature conditions to enhance the wear resistance. Based on the friction coefficient changes, wear morphology, phase composition, and chemistry element, the high-temperature wear mechanisms of FeCoNiCrAlx were discussed including adhesive, attrition, and oxidative wear. These new studies will lead to the further improvement of tribological data of high-entropy alloys.

Effects of Nano-CeO2 on Microstructure and Properties of WC/FeCoNiCrMo0.2 Composite High Entropy Alloy Coatings by Laser Cladding

FeCoNiCrMo0.2 high entropy alloy has many excellent properties, such as high strength, high wear resistance, high corrosion resistance, and high ductility. To further improve the properties of this coating, FeCoNiCrMo high entropy alloy (HEA) coatings, and two composite coatings, FeCoNiCrMo0.2 + WC and FeCoNiCrMo0.2 + WC + CeO2, were prepared on the surface of 316L stainless steel by laser cladding technology. After adding WC ceramic powder and CeO2 rare earth control, the microstructure, hardness, wear resistance, and corrosion resistance of the three coatings were carefully studied. The results show that WC powder significantly improved the hardness of the HEA coating and reduced the friction factor. The FeCoNiCrMo0.2 + 32%WC coating showed excellent mechanical properties, but the distribution of hard phase particles in the coating microstructure was uneven, resulting in unstable distribution of hardness and wear resistance in each region of the coating. After adding 2% nano-CeO2 rare earth oxide, although the hardness and friction factor decreased slightly compared with the FeCoNiCrMo0.2 + 32%WC coating, the coating grain structure was finer, which reduced the porosity and crack sensitivity of the coating, and the phase composition of the coating did not change; there was a uniform hardness distribution, a more stable friction coefficient, and the flattest wear morphology. In addition, under the same corrosive environment, the value of polarization impedance of the FeCoNiCrMo0.2 + 32%WC + 2%CeO2 coating was greater, the corrosion rate was relatively low, and the corrosion resistance was better. Therefore, based on various indexes, the FeCoNiCrMo0.2 + 32%WC + 2%CeO2 coating has the best comprehensive performance and can extend the service life of 316L workpieces.

Experimental characterization of tool wear morphology in milling of Al520-MMC reinforced with SiC particles and additive elements Bi and Sn

Combining aluminium as a soft, lightweight, and low-strength material with reinforcing elements may lead to fabricating materials with excellent abrasion resistance and a high strength-to-weight ratio. However, these fabricated materials are classified as difficult to cut materials due to elevated tool wear size. According to the literature, limited studies were reported on the effects of various reinforcing elements on the machinability of Al520-MMC, mainly tool wear morphology and size. Therefore, in the course of this study, Al520-MMCs were fabricated with various reinforcing elements, such as silicon carbide (SiC), bismuth (Bi), and tin (Sn) particles. No similar work was found in this regard. Accordingly, as an originality of this work, besides fabricating new MMcs, the experimental characterization of tool wear morphology was conducted when milling Al520-MMCs with various reinforcing elements. Despite the reinforcing elements used, higher tool flank wear was observed under dry machining. Furthermore, knowing that Al520-MMC is a soft metal, the built-up edge (BUE) was observed under all lubrication modes and cutting speeds. Additionally, abrasion was found in all cutting conditions used. Therefore, it could be stated that the reinforcing elements and cutting speed had the most significant effects, and the lubrication mode had minimal impact on the wear size. Compared with the recorded values of tool flank wear in machining Al520 + 10% SiC, the flank wear was reduced by around 50% when Bi and Sn were used in the matrix structure. In other words, using bismuth (Bi), and tin (Sn) particles may lead to better tool life.