Wear Morphology Research Articles

Thermal effects on wear behavior of additively manufactured NiTi shape memory alloys

NiTi alloys fabricated by laser powder bed fusion (LPBF) additive manufacturing technology not only address the compositional instability resulting from complex processes but also solve the challenges of difficult machining of intricate aerospace structures. However, there are very few reports on the wear behavior of LPBF-NiTi alloys. In the present work, the effects of microstructure and thermal treatment, including heat treatment and frictional heat, on the wear behavior of LPBF-NiTi alloy and 100Cr6 ball were analyzed through a series of tribological experiments with different sliding speeds. As the average sliding speed increases (0.079–0.216 m/s), the wear rate of the as-built and heat-treated samples tends to decrease in the range of 2.69 × 10−3–0.97 × 10−3mm3/m. Although the heat-treated LPBF-NiTi alloy is 46 % harder than the as-built alloy is, the latter has a higher toughness (505 MJ/m3) and greater transformation strain of SIM (0.097). This leads to a coupling effect of heat treatment and sliding speed on the wear resistance. In addition, the wear track morphologies under different sliding speeds are asymmetric due to the 24% greater acceleration at the far end from the motor and the 2.15 mm deviation between the maximum speed position and the geometric center of the track. The wear modes of the as-built and heat-treated samples included adhesive, abrasive and delamination wear. Moreover, the wear morphologies and dominant wear modes change with the frictionally caused heat release induced by the sliding speed.

On dry machining of AZ31B magnesium alloy using textured cutting tool inserts

Magnesium alloys have many advantages as lightweight materials for engineering applications, especially in the fields of automotive and aerospace. They undergo extensive cutting or machining while making products out of them. Dry cutting, a sustainable machining method, causes more friction and adhesion at the tool-chip interface. One of the promising solutions to this problem is cutting tool surface texturing, which can reduce tool wear and friction in dry cutting and improve machining performance. This paper aims to investigate the impact of dimple textures (made on the flank face of cutting inserts) on tool wear and chip morphology in the dry machining of AZ31B magnesium alloy. The results show that the cutting speed was the most significant factor affecting tool flank wear, followed by feed rate and cutting depth. The tool wear mechanism was examined using scanning electron microscope (SEM) images and energy dispersive X-ray spectroscopy (EDS) analysis reports, which showed that at low cutting speed, the main wear mechanism was abrasion, while at high speed, it was adhesion. The chips are discontinuous at low cutting speeds, while continuous at high cutting speeds. The dimple textured flank face cutting tools facilitate the dry machining of AZ31B magnesium alloy and contribute to ecological benefits.

Examining Wear Mechanisms in Railway Wheel Steels: Experimental Insights and Predictive Mapping

Railway systems play a pivotal role in modern transportation networks, contributing to both efficiency and environmental sustainability. This study investigated the multifaceted aspects of wear phenomena in railway engineering, focusing on their significant implications for environmental costs and operational efficiency. Experimental trials were conducted using a high-performance bi-disc apparatus, evaluating a range of materials, contact pressures, and lubrication conditions. Shakedown maps were employed to assess ratcheting behaviour, while the wear rate was analysed as a function of the fatigue index (FI). The results reveal the intricate interplay of contact pressure, slip ratio, material properties, and lubrication in determining wear and ratcheting behaviour. Oxidative and mild wear mechanisms were identified, and wear debris composition and morphology were characterised. The outcomes from this research clarify the pivotal role that wear processes play within railway systems and the far-reaching environmental repercussions they entail. This exploration contributes to the ongoing optimisation of railway operations, offering valuable insights aimed at mitigating unavoidable pollution sources and strengthening sustainability efforts. By delving into the intricate dynamics of wear phenomena within wheel–rail material, this research paves the way for innovative solutions that not only enhance operational efficiency but also minimise the ecological footprint of railway transportation.

A comparative study on the electrical contact behavior of CuZn40 and AgCu10 alloys under fretting wear: Effect of current load

The current load is one of the most significant factors in the reliability of electrical contact under fretting conditions. In this paper, the fretting wear experiments are conducted for CuZn40 and AgCu10 alloys with varied current loads. The variations of electrical contact resistance (ECR), ECR endurance, temperature, and wear volume with the increasing current load of two alloy materials under fretting conditions are investigated, and the differences between their electrical contact behaviors are compared. The microstructures of the surface wear morphology are examined to reveal the mechanisms of fretting wear and electrical contact failure. In addition, the fretting wear volume evolution of both alloys under different fretting cycles is studied. The results show the current load impacts the wear morphology. The wear particles become smaller and the oxide layer becomes stable with the increase of current load. The effect of current load on ECR and temperature is more significant for CuZn40 alloy. The ECR endurance for both materials first increases and then decreases. This is attributed to two competitive mechanisms controlling the evolution of ECR endurance under varied current loads.

Analysis of the crack initiation and short crack propagation of laser cladding IN718 enduring fretting fatigue at 650 ℃

In order to reveal the behaviors of crack initiation and short fatigue crack propagation in laser cladding IN718 under high temperature conditions, very high cycle fretting fatigue (VHCFF) experiments were conducted at 650 ℃ with a transverse clamping force of P=400N and different axial stress loading conditions to obtain S_N data. The surface wear morphology and fracture morphology characteristics were analyzed by scanning electron microscope (SEM) and white light interferometer. Additionally, the microstructure characteristics of grains in the short fatigue crack region were examined through electron back scatter diffraction (EBSD). Parameters such as equivalent grain size, grain elastic modulus, Schmid factor, geometric compatibility factor, twist angle, and tilt angle were considered in the analysis of the characteristics of fatigue crack initiation and propagation. The results indicate that fretting fatigue cracks tend to initiate on grains with higher Schmid factors, larger equivalent grain size, and lower grain elastic modulus on the fretting contact surface. Moreover, the short fatigue cracks tend to propagate along the grains with the microstructural features of the high Schmid factor, the geometric compatibility factor of m′>0.4, the twist angle of α<50°, and the tilt angle of β<50°.

Investigation of tribological behavior of poly(methyl methacrylate) biocomposite containing hydroxyapatite

Poly(methyl methacrylate) (PMMA), is widely used in biomedical applications such as bone cement. However, it is known to have low wear resistance. To enhance its tribological behavior, a reinforcement phase is necessary. For this purpose, in this study, homemade hydroxyapatite (HAp) was utilized to enhance the mechanical properties and wear resistance of PMMA while also increasing its biocompatibility. Using the thermal extraction method, natural raw materials were used to synthesize homemade HAp powder successfully. The d 0.5 of HAp powders in particle size analysis was 7.464 μm. Hot isostatic pressing (HIP) was used to create PMMA–HAp biocomposites with various HAp ratios (5, 10 and 15 wt%) in PMMA. The wear morphology was characterized by scanning electron microscopy (SEM). The SEM images showed a severe abrasive wear mechanism, but a relatively stable wear surface was observed that indicated slight abrasion during the wear tests with the increase in HAp ratio. The highest wear rate was obtained in 15% HAp-reinforced PMMA at a sliding speed of 1.0 m/s and had value of 4.72 × 10−4 mm3/(N m) under a 20 N load. The HIP’ed densities of the samples increased from 1.15 to 1.31 g/cm3 with increasing amount of HAp. Similarly, the Vickers test results showed that the hardness values increased from 14.76 to 22.03 HV.

Synergistic enhancement in mechanical properties of graphene/MWCNT reinforced Polyaryletherketone – carbon fiber multi-scale composites: Experimental studies and finite element analysis

This investigation focuses on the synergistic performance improvement in graphene/MWCNT reinforced Polyaryletherketone (PAEK) - carbon fiber (CF) multi-scale composites. FTIR revealed the chemical interactions while HRTEM, XRD and 3D X-ray microscopy gave insight into nanofiller dispersion and microstructural features. The functional groups on nanofillers along with structural features integrated various components of the multi-scale composites by formation of graphene/MWCNT/CF complex network that provided larger interfacial area, bridging effect and physico-chemical interaction with PAEK while restricting its segmental mobility. Multi-scale composites displayed significantly improved strength, fracture toughness, interlaminar shear strength, glass transition temperature and tribological performance. Under dynamic load, graphene/MWCNT reinforcement of matrix and CF synergistically increases the storage modulus and energy absorption characteristics. Wear and fracture surface morphology of nano and multi-scale composites showed ductile failure confirming interfacial adhesion. The failure behavior in experimental studies was supported by Abaqus/Explicit-based FEM models of fracture toughness response. This work provides a promising avenue to develop next generation high performance thermoplastic composites for structural applications.

Effects of turbulence and bush wear on the transient tribo-dynamic characteristics of water-lubricated bearings

This research proposes a transient mixed elastohydrodynamic model considering turbulence and bush wear, as well as the concept of contact work, to study the transient tribo-dynamic characteristics of water-lubricated bearings. The effects of turbulence, wear depth, and wear deviation angle on transient tribo-dynamic characteristics of water-lubricated bearings are investigated. The findings show that turbulence significantly affects the dynamics of stable conditions and enhances the hydrodynamic effect, but little affects the frictional contact behavior. An appropriate wear depth favors improving the tribo-dynamic characteristics of the water-lubricated bearings, but it deteriorates as the wear depth continuously increases. Negative deviation angles are better for minimizing contact work and enhancing rotor stability. The lubrication and dynamic properties of water-lubricated bearings can be enhanced through a rational approach to wear morphology design. This research is important for the optimal design and diagnosis of water-lubricated bearings wear failures.

Research on the effect of fretting wear on the vibration characteristics of the tenon joint bladed disk

The tenon joint structure is a typical structure of aero-engine bladed disk. Under external excitation, micro-slip inevitably occurs between the tenon and the tenon groove of the blade, which will cause fretting wear on the contact surface. The resonance frequency and margin of the bladed disk structure will change after fretting wear occurs. In this paper, a finite element subprogram is compiled based on the basic principle of Archard wear, which realizes the generation of surface wear morphology and multi-step iterative update of the double-tooth fir-tree joint model under fretting load. The subroutine is used to quantitatively analyze the wear depth distribution of the tenon joint surface under fretting loads. On this basis, the resonance margin and the vibration response characteristics of the bladed disk are quantitatively studied after fretting wear. The research results show that the natural vibration frequency of the bladed disk structure decreases at different wear times. This caused a decrease in the resonance margin of more than 80% of the measuring points. In addition, the resonance response amplitudes all showed an upward trend with the increase of wear depth.

A life-cycle dynamic wear degradation model of planetary gear systems

An accurate prediction model for surface wear in planetary gear systems is essential to decipher wear fault mechanisms and facilitate model-driven failure prognosis. A high-fidelity dynamic wear model relies on the appropriate characterization and updating strategy of the tooth macro-geometry, contact parameters and dynamic load. A geometrically adaptive-loaded tooth contact analysis (GA-LTCA) method is proposed to “bridge” wear morphology and dynamic behaviours. The finite element method and run-to-failure test are adopted to verify the GA-LTCA method and wear prediction model, respectively. Based on the proposed wear model, the life-cycle wear characteristics and the updating strategy of wear geometry are investigated. Owing to the consideration of the micro-cycle of the contact stress and geometrical updating, the predicted wear profile exhibits a desirable agreement with experimental results. The tooth profile deviation vector should be updated more frequently than the finite element model of worn gears. Only the finite element grid of the sun-planet gear pair should be updated because the wear of the sun-planet is much more serious than that of the ring-planet. Numerical results indicate the potential of the proposed high-fidelity model for digital twin-based wear prediction and life cycle failure prognosis.

Effects of shear thickening fluid preparation on tool performance in the milling of Ti6Al4V titanium alloy

The performance and quality of tools can directly affect the efficiency and quality of machining, and preparation methods of the cutting edge have an important impact on the machining performance and tool life. As a method that can adapt to the unique and complex geometry of the cutting edge, shear thickening passivation is an innovative application of shear thickening fluid. In this study, the effects of shear thickening passivation methods on the milling performance and tool life of cemented carbide milling cutters were investigated. The cutting force, tool wear, tool life and surface morphology were analyzed by side milling Ti6Al4V titanium alloy with cemented carbide milling cutters that were unprepared, drag finished and shear thickening passivated, respectively. The results demonstrate that shear thickening passivation can remove the micro-defects of the tool after grinding. After shear thickening passivation, the cutting edge is rounded, and the rake and flank surfaces are flat, and the defects of the cutting edge are removed. Compared with the unprepared tool, the life of the shear thickening passivated tool is improved by 50 %. Therefore, the shear thickening passivation can effectively improve the tool life and tool performance and significantly reduce the economic cost in practical machining.

Wear behavior of MIG manufactured 12Cr-xC (x=0.3, 0.4) hardfacings under different temperatures and loads

Metal inert gas (MIG) hardfacing technology has developed high-performance materials on carbon steel, which exhibit superior thermal wear resistance linked to Cr and C contents. In this study, the 12Cr-xC (x = 0.3, 0.4) hardfacings were manufactured by the MIG method, and the corresponding wear behavior on different loads and temperatures was characterized. The results revealed that the 12Cr-xC hardfacings exhibited good forming quality, with microstructure consist of martensite matrix, retained austenite, varying shape of the martensite-austenite continent (M/A), and a small number of carbides. The hardness reaches 483.1 and 520.3 HV0.2. The coefficient of friction (COF) of the 12Cr-xC hardfacings showed a range of 0.27-0.43 and decreased with temperature increased from 150 °C to 300 °C at 200 N. The 12Cr-xC hardfacings exhibited a good wear resistance and the wear loss rates at a low level (10-5 mm3/(N·m)). The SiC balls' worn morphology is irregular, with abrasive wear and embedded oxide debris. Adhesive wear occurs under specific conditions, with a low wear loss rate compared to hardfacings. At 150 °C, 12Cr-xC hardfacings exhibit low Whardfacing/Wball (4–11), with abrasive mechanisms. Higher loads lead to more pronounced sacrifice of SiC balls, with abrasive wear and oxides covering the worn surface at 300 °C, with tribochemical reactions being the dominant mechanism.

Influence of diamond-like carbon coatings and micro-texturing on friction and wear of seal interfaces: Experiment and simulation study

For mechanical seal friction vice in dry friction conditions, due to friction wear serious failure, is the slurry pump and other instruments in the operation of the process of the urgent need to solve the problem. In this paper, in order to optimize and enhance the friction and wear problem of mechanical seal end face of slurry pump. Surface treatment of mechanical sealing rings with diamond-like carbon (DLC) coating and surface microtexturing, and at different rotational speeds and normal forces, the surface hardness, wear coefficient and dry friction coefficient of the sealing rings were analyzed by experimental comparison, and the wear morphology was collected by electron microscopy, having analyzed the results of the sets of, the end face structure of the mechanical seal was optimized. Based on Archard wear model simulation calculations, the seal ring wear depth and wear quality were obtained. The results show: under dry friction conditions, the synergistic effect of the DLC coating and the surface micro-texture (MT), the coefficient of friction is reduced by approx. 68% and the quality and depth of wear is minimized. Excessive speeds and normal forces are more prone to wear behavior caused by abrasive wear. Simulation results of surface treatment groups, DLC / MT group maximum wear depth is the smallest; wear quality test and simulation of the maximum error within 15.7%. The results of the study can provide a basis for a phosphoric acid plant slurry pump mechanical seal design.

Improvement of thermal conductivity and wear property of Gr/EP composites with CNTs/Cu foam as 3-dimensional reinforcing skeleton

The graphite-reinforced epoxy resin composite (Gr/EP) is considered one of the promising solid lubricating materials. However, the low thermal conductivity and correlated poor wear resistance cause limitations to its tribological applications. With the expectation to improve the thermal conductivity and wear property, carbon nanotube (CNT)-reinforced copper foams (CNTs/Cuf) are introduced as 3-dimensional skeletons to reinforce Gr/EP composites. Herein, comprehensive testing was conducted to assess the wear resistance, thermal conductivity, microstructure, and wear morphology of the composites. The results revealed that incorporating Cu or CNTs/Cu foams into the Gr/EP matrix significantly enhanced thermal conductivity and wear resistance, with only minor elevation of the friction coefficients, which showed a consistent decline trend with increasing CNTs contents. Notably, with the CNT content of 0.159 wt%, the composites reached the favorable combination of a 25.4 % improvement in thermal conductivity and a 34 % reduction in wear rate compared to pure copper foam-reinforced Gr/EP composites.

Analysis of the Sand Erosion Effect and Wear Mechanism of Wind Turbine Blade Coating

The wind–sand climate prevalent in the central and western regions of Inner Mongolia results in significant damage to wind turbine blade coatings due to sand erosion. This not only leads to a decline in power generation but also poses safety risks. This study replicated the wind–sand environment of Alashan and numerically simulated the erosion and wear process of the blade coatings of a 1.5 MW horizontal axis wind turbine under rotational conditions using the DPM model. Additionally, erosion tests were conducted on the operating wind rotor in a wind tunnel. The simulation results demonstrate that sand particle trajectories in the rotating domain are influenced by vortex, incoming wind speed, and sand particle size. For small-sized sand particles, variations in wind speed do not substantially alter the number of particles in contact with the wind turbine blades. However, alterations in the momentum of these particles lead to changes in the impact force on the coating surface. Conversely, the change of wind speed will not only alter the number of large-size sand particles in contact with the wind rotor but also modify the impact force on the coating surface. Furthermore, after impacting the blade, small sand particles continue to move along an approximate helical trajectory with the airflow, while large-size sand particles swiftly rebound. Through statistical analysis of erosion pits on the blade surface after the erosion experiments, it was observed that, in comparison among the leading edge, windward side, trailing edge, and leeward side, the leading edge presents the greatest number of erosion pits, whereas the leeward side has the fewest. Along the spanwise direction, the 0.7R-blade tip segment exhibits the highest count, while the blade root-0.3R section displays the fewest number of pits. The wear morphology of the blade coating was observed from the blade root to tip. The leading edge coating exhibits a range from shallow pits to coating flaking and deeper gouge pits. On the windward side, the coating displays wear patterns varying from tiny cutting pits to cutting marks, and then to gouge pits and coating flaking. Erosion morphology of the trailing edge evolves from only minor scratches to spalling pits, further deepening and enlarging. These research findings provide a basis for the study of zoning-adapted coating materials for wind turbine blades in wind–sand environments.

Numerical Investigation of the Impacts of Large Particles on the Turbulent Flow and Surface Wear in Series-Connected Bends

The deep sea harbors abundant mineral, oil, and gas resources, making it highly valuable for commercial development, including the extraction of minerals. Due to the relatively large particle size of these minerals, how they interact with fluids is significantly different from that of small particles. However, there has been limited simulation research on the impacts of large particles (the diameter of particles is at the level of centimeters) on the flow and wear characteristics in bends, because the simulation of the particles at such a size is difficult. Additionally, in the field of deep-sea mining, multiple bends are simultaneously connected in series, and the wear in such bends has garnered increasing attention. Based on an improved CFD-DEM model, this article solved the issue that traditional unresolved CFD-DEM methods cannot accurately simulate large particles in a hydraulic conveying pipe and bend. After validating the accuracy of this model against classical experiments, the paper comprehensively analyzes the modulation effect of large particles on turbulence, and the effects of different particle diameters, particle transport concentrations, and transport velocities on the wear of bends connected serially. Finally, the bends connected serially in various configurations are simulated to study the wear on the bent interior surfaces. Results indicate a pronounced modulation effect of large particles on turbulence at higher transport concentrations; the wear rate in the combined bends does not exhibit a linear correlation with the collision frequency of particles on the wall surface. Furthermore, different configurations of serially connected bends exhibit significant differences in the wear morphology of the second bend.

Exploring the influence and mechanism of hardfacing STL12 on impact wear performance at high temperature and heavy load

As one of the most important contact pairs of an engine, the performance improvement of the valve and seat insert contact pair is of great concern. In this study, commonly used industry tempered seat inserts and hardfacing seat inserts were selected (named tempered group and hardfacing group respectively). The impact wear performance test was carried out, under conditions consistent of temperature of 650 °C, load of 30 kN, frequency of 12 Hz, and stroke of 1 mm. The wear process of the wear zone was investigated using 3D scanner, optical microscope (OM), scanning electron microscope (SEM), and X-ray photo-electron spectroscopy (XPS). The wear mechanism of the wear area was analyzed according to macro profile and micro wear morphology. The results showed that after the impact test, a layer of oxide film was formed on the surface of the hardfacing seat insert, which isolated direct contact of the valve and the seat insert, greatly improving the wear performance of the pairs. In addition, the hardness of the hardfacing seat insert was higher than the tempered seat insert, this further reduced the weight loss between the contact pairs. The weight loss of hardfacing group was 0.36 g and tempered group was 1.62 g, the weight loss of hardfacing group was reduced by 77.78 % compared with that of tempered group. So in conclusion the impact wear performance of the hardfacing pair is better than the tempered pair.

Multi-Field Coupling Numerical Analysis and Experimental Validation of Surface-Textured Metal Seals in Roller Cone Bits

Metal seals play a crucial role in ensuring the dependable functioning of the bearing system in roller cone bits. Due to the intricate nature of downhole conditions, the microstructure design of sealing end faces, specifically the surface texture, is rarely used in metal seals. This study focuses on examining the applicability of surface texture technology in metal seals for cone bits to enhance the lubrication characteristics and friction and wear properties of liquid film between end faces. A multi-field coupling model of surface-textured metal seals was established and experimentally verified. The liquid film carrying the capacity and sealing performance of five different shapes of surface-textured end faces (circle, ellipse I (horizontal), ellipse II (vertical), triangle, and chevron) were investigated under varying rotational speeds and environmental pressures. The influences of texture parameters, including depth and area ratio, on the lubrication characteristics and friction reduction effects of surface-textured metal seals were investigated, and the microscopic wear morphology characteristics of the sealing end faces were analyzed. The results show that surface textures can effectively improve the liquid film state and comprehensive performance of metal seals. Specifically, triangle textures significantly enhance the hydrodynamic pressure effect and weaken the abrasive wear and adhesive wear of the end faces. However, when the environmental pressure is p ≥ 30 MPa, the surface textures gradually lose the advantages of dynamic lubrication but can still reduce friction. The proper texture depth and area ratio can achieve zero leakage (obtained theoretically) and minimal friction in metal seals.

The influence of competition between thermal expansion and braking parameter on the wear degradation of friction block

A simulation method is adopted to study the influence of the competition between thermal expansion and braking parameters on friction block wear. The reliability of the simulation is verified through the braking tests. The results indicate that the dynamic wear distribution of friction blocks is jointly affected by thermal expansion and relative motion of the friction pair. The thermal expansion causes concave wear and the relative movement causes eccentric wear of the friction block. The extreme numbers of the wear morphology can be used as an indicator for the wear evolution process. The changes in braking parameters affect the wear distribution of the friction block, the increase in braking pressure and speed exacerbates the eccentric wear and the concaved wear of the friction block, respectively. According to the results, a good match between thermal expansion behavior and braking parameters can optimize the wear behavior of the friction block.

Study on the Formation Mechanism for High Rail Corrugation

This research employed a tracking investigation and numerical study to examine the initiation of high rail corrugation. Beginning with the trial operation of Metro Line 6 in Chengdu, China, we conducted a follow-up investigation for 2½ years that recorded the rail surface wear morphology of a 600-m radius curved track. The field observation results show that high rail corrugation occurred 12–17 months after the subway was officially put into operation, whereas the low rail of the same track did not show any corrugation. The distribution of high rail corrugation was discontinuous. Due to wear, the profiles of the rails and wheels changed. Two points of contact may occur between the leading outer wheel and high rail, with one contact point at the gauge corner and the other in the vicinity of the railhead (hereafter referred to as two-point contact). We developed a finite-element model that used the measured worn profiles to predict the self-excited frictional vibrations of a leading wheelset–rails system under the condition of two-point contact. We predicted the occurrence trend of self-excited frictional vibrations via the complex eigenvalue analysis. The simulation results show that in the condition of two-point contact, the self-excited frictional oscillation produced at an outer wheel–high rail interface can induce high rail corrugation. The use of straight or double S-shaped web plate wheels and an increase in railpad damping can help to reduce high rail corrugation.