Main Wear Form Research Articles

Laser cladding Ni60-SiC/Ti3SiC2 self-lubricating composite coatings on IN718 alloy: Wear mechanisms and oxidation behaviors

To enhance the service performance of IN718 alloy under severe working conditions, the self-lubricating composite coating of Ni60-SiC/Ti3SiC2 was fabricated on its surface using laser cladding. By systematically analyzing the microstructure and properties of composite coatings, the wear mechanism at different temperatures and the oxidation behavior at 800 °C of coatings were discussed in depth. The results demonstrate that an increase in coatings’ microhardness by a factor of 1.9–3.1 over IN718 was achieved, benefiting from the fine-grained and solid-solution strengthening actions, and the hard phases such as C23C6, Ni3Si, TiC distributed diffusely inside the coatings. The tribological performance of coatings was also significantly improved, in which the coating with 10 wt% Ti3SiC2 added had the lowest wear rates of 2.13 and 3.57 × 10−5 mm3/N·m at RT and 600 °C, respectively, which were reduced by 82.74 % and 87.43 % compared to the substrate. When the test temperature changes from RT to 600 °C, the main wear form of coatings changes from adhesive and abrasive wear to oxidative wear. With the Ti3SiC2 content increasing, the oxide film is gradually dense and uniform, and the oxidation resistance is significantly improved.

Investigation of curve minimum radius in heavy-haul railway to improve wheel wear evolution and wheel-rail contact geometry

To determine the minimum and reasonable radius of horizontal curve for reducing wheel wear in heavy-haul railway design, a HXD locomotive with the wheel arrangement of C0-C0 is taken as the research object. Both the corresponding locomotive dynamic model and wheel wear model are established. Based on the measured wear data in a specific line, the simulation model is verified with the prediction error of wheel wear depth below 0.5 mm in general. The wheel wear evolution rules in 400∼1000m radius curves are studied and compared. The results indicate that, the wheel wear is large and sensitive to curve radius within 400∼600 m. The larger radius curve will be helpful to reduce wheel flange contact and wheel wear. For curve radius increasing from 600m to 1000m, the wheel average wear reduces slowly. Especially for curve radius below around 740 m, the wheel flange wear will be predominant. For radius above 740m, the wheel tread wear becomes the main wear form and the wheel flange wear can be reduced significantly. The increase of curve radius will also improve the wheel-rail equivalent conicity. If the minimum curve radius is set as 800m, the equivalent conicity difference between new wheelset and 1st ∼ 3rd worn wheelset can be kept below 21%, 52% and 9% respectively. In this case, the equivalent conicity is closest to the initial state and reaches a steady state, which will not change significantly with the radius further increasing. Viewed from the aspects of reducing wheel wear, avoiding wheel flange contact and keeping conicity stable simultaneously, the minimum radius of horizontal curve should be limited to 800 m. The research results validate the minimum curve radius suggested in Code for Design of Heavy-haul Railway in China, and provide a scientific explanation for the determination of this value.

Wear-resistant ZrN/Ti functionally graded coating prepared on TA18 alloy by double glow plasma alloying

Despite being an excellent structural material, α-Ti alloy is with low shear deformation resistance, resulting in susceptibility to friction damage during service, and limits its further application. A wear-resistant ZrN/Ti functionally graded coating (FGC) was prepared on TA18 alloy by double glow plasma alloying technique in this paper. The morphology, phase structure, mechanical properties and wear behavior of ZrN/Ti FGCs were studied and analyzed. The results proved that a gradient structure formed in the coating: the topmost layer was ZrN ceramic phase, in the transition layer were ZrN, TiN, and Ti2N phases, and in the inner layer was α-Ti phase. The coating was dense and metallurgically bonded with the substrate. It exhibited better load bearing capacity and fracture toughness. Upon conclusion of wear tests under different loads, only slight damage was observed on the coating. The main wear form of the coating was delamination wear, and the ZrN layer on the topmost surface was not worn through. More specifically, the Zr pre-diffusion treatment was used to increase the content of ZrN in the transition layer, reducing the unfavorable Ti nitride phase formed. Therefore, the stress concentration caused by the difference in elastic modulus between the different phases was relieved. Thus, ZrN/Ti FGC with continuous properties and good wear resistance was successfully synthesized.

Wear behaviour of abrasive tools and its effect on surface integrity during polishing superalloy GH4169G with abrasive cloth flap wheels

In polishing nickel-based superalloys, the surface quality and dimensional accuracy of the workpiece are closely related to the wear of the abrasive tools. Over the years, several researchers have studied the wear of grinding wheels or abrasive belts, including the effects of various machining methods, abrasive materials, and machining parameters on the wear of abrasive tools. However, there is not enough research on the wear mechanism of the abrasive cloth flap wheel (ACFW). In this paper, during polishing GH4169G with ACFW, the wear evolution mechanism of ACFW and its effect on the surface integrity of GH4169G were investigated. First, the variations in material removal and ACFW wear amounts during the polishing process were analysed, and the different wear stages were divided based on the polishing ratio. Second, the mic-morphology and surface element distribution of ACFW at different wear stages were investigated using SEM and, EDS, and the wear evolution mechanism of ACFW was analysed. Finally, the effects of ACFW wear on the surface morphology, surface oxidation and microstructure of GH4169G were investigated by SEM, EDS, XRD, and EBSD. The results showed that the primary wear forms of ACFW were stepped fracture, cleavage fracture, blunt, pull-out, and adhesion wear. During the initial wear stage, the proportion of each wear form was relatively balanced. In the medium wear stage, fracture wear was the main wear form. Blunt and adhesive wear were the primary forms of wear during the final wear stage. In addition, with ACFW wear, the surface roughness tend to decrease first and then increase, however, the refinement level of the grains, the intensity of plastic deformation and the intensity of the oxidation reaction gradually increased. This study provides effective guidance for developing more wear-resistant abrasive tools and optimising the grinding and polishing processes.

Physicochemical properties of soot in diesel engine lubricating oil: characterizations and impact on frictional characteristics

The study investigates the effects of the physicochemical properties of engine sump soot on the frictional characteristics of its contaminated engine oils. Moreover, the relationship between soot physicochemical properties and its frictional characteristics was also discussed. The results showed that the properties of the two kinds of lubricating oil (A, B) used in diesel engines affect the properties of engine sump soot (Soot-A, Soot-B), i.e. Soot-A showing smaller aggregate size, larger primary particle diameter, more disordered nanostructure, and higher functional content than those of Soot-B. For both soot particles, as the amount of soot particles added to the formula oil went up from 1 wt.% to 2 wt.%, the wear scar diameter (WSD) and friction coefficient of the wear spot increased. For both soot particles, the main wear form of the steel ball wear area was abrasive wear (more than 90%), accompanied by a small amount of plastic deformation and pitting (less than 2%). With the same amount of soot in lubricating oil, soot with a higher degree of graphitization, low oxygen content and low reactivity may cause smaller WSD and lighter wear. Moreover, a larger soot accumulation would result in deeper plow marks and pits in the abrasion areas.

Fabrication of multi‐scale TiC and stainless steel composite coatings via circular oscillating laser towards superior wear and corrosion resistance of aluminum alloy

The poor wear and corrosion resistance of aluminum alloys has led to the easy failure of surface performance. In this work, composite coatings of TiC/martensitic stainless steel (TiC/MSS) on aluminum alloy are fabricated by a novel approach of circular oscillating laser for enhanced surface performance of aluminum alloys. The oscillation of laser leads to dense microstructure, and nano/micro scale TiC particles are formed simultaneously. The structure of coatings transforms from dendritic to ring-like with the addition of TiC, and the hardness of the substrate is increased by 4.5–7.8 times. The main wear form of coatings is adhesive wear. The refinement of microstructure and formation of multi-scale TiC have given rise to an increase in the resistance of the coating to plastic deformation, which reduces the degree of adhesion and improves wear resistance. Besides, the barrier effect of TiC particles to the electrolyte solution in the passive film gives rise to the drop in corrosion current density. The Cr-rich stacking faults can provide nucleation sites for the formation and growth of passive films with high continuity and stability, thereby improving the corrosion resistance of the coatings. The superior anticorrosion and wear resistance properties of the composite coatings in this work have emphasized the merits of oscillating laser in fabricating high-performance coatings and would enlighten the design of more advanced composite coatings.

High-temperature wear mechanism of roller cone bit spiral seal

When drilling, the spiral seal of the roller cone bit and the journal are prone to collision and wear, and the friction heat and downhole high temperature will affect the wear process. The friction and wear experiments of the spiral seal material (20CrNiMo–40Cr) at different temperatures were carried out to study the wear mechanism of the spiral seal and journal of roller cone bit at high temperatures to determine the wear amount, friction coefficient and main wear forms. The wear model of friction pairs is established based on the Archard wear model and experimental results; The wear results at different temperatures are obtained by establishing the spiral seal structure model and simulation research of the roller cone bit. The results show that:(1) Through the friction and wear experiment of friction pair materials, the higher the temperature is the greater the wear amount and friction coefficient are. When the temperature exceeds 100 °C, the wear amount and friction coefficient begin to decline with the increase in temperature. By observing the wear surface morphology, abrasive and adhesive wears occur simultaneously, and the main wear form is adhesive wear under high-temperature conditions.(2) The maximum temperature rise caused by friction and the relationship between wear volume and time at different temperatures are obtained through the simulation of the spiral seal structure. Taking the groove depth value as the index to evaluate the sealing effect, the roller cone bit works in the temperature range (25 °C-400 °C), and high-temperature wear does not affect its sealing performance.

Investigation on the machinability of SiCp/Al composite by in-situ laser assisted diamond cutting

As a difficult-to-cut material, high-quality machining of SiCp/Al composite is a huge challenge for conventional machining techniques. In this study, an in-situ laser assisted diamond cutting technology was innovatively applied to SiCp/Al composite machining. The influence of machining parameters on machined surface roughness and morphology was analyzed. The wear mechanism of the diamond tools with conventional and in-situ laser assisted diamond cutting was revealed. Subsurface damage was investigated from residual stress and crystal defects. Experimental results show that the in-situ laser assisted diamond cutting technology effectively inhibits the generation of large-sized surface defects such as scratches and pits, and improves surface quality. Compared with conventional diamond cutting, the best surface roughness Sa is significantly decreasing by 89.5% to 10.2 nm. In addition, residual stress is effectively reduced by 42%. In in-situ laser assisted diamond cutting, the main tool wear form is flank wear caused by abrasive wear and chemical wear. During processing, an amorphous layer of about 40 nm is generated on the machined surface, accompanying subsurface defects such as particle fracture, micro-crack, dislocations, and stacking faults. The in-situ laser assisted diamond cutting is an effective and promising method for ultra-precision machining SiCp/Al composites.

Wear and rolling contact fatigue competition mechanism of different types of rail steels under various slip ratios

This study aims to explore the wear and rolling contact fatigue (RCF) competition mechanism of the hypoeutectoid, eutectoid rail, and bainitic rail steels under different slip ratios. The results showed a clear competition relationship between wear and RCF of rail steel. With the increase in slip ratio, the wear rate of hypoeutectoid and eutectoid rail steels was increased and then remained stable, and the wear rate of bainitic rail steels was increased. Bainitic rail steels suffered catastrophic wear when the slip ratio exceeded 2%. With the slip ratio increased, the RCF crack propagation rate of the hypoeutectoid rail and eutectoid steels rail increased rapidly at first and then increased slowly. Except for the slip ratio of 5%, the RCF crack propagation rate of the bainitic rail increased with the increase in slip ratio. With the increase in slip ratio, the degree of wear rate increase and crack propagation rate was not consistent, which led to the competition between wear and RCF. The competitive relationship between wear and RCF was reflected in the variation of rail wear form. As the slip ratio increased, the main wear form of the hypoeutectoid and eutectoid rail steels was transformed from adhesive wear to adhesive wear and fatigue wear, whereas for bainitic rail steel, it was changed from adhesive wear to fatigue wear, and finally to adhesive wear. At high slip ratios, the retained austenite of bainite rail steel was seriously broken, so cracks in the bainitic rail steel could easily propagate along the plastic deformation layer.

Cutting performance of a tool with continuous lubrication of atomized cutting fluid at the tool-chip interface

To improve the tool lubrication performance and reduce the use of cutting fluid as much as possible, a new type of tool with continuous lubrication on the tool-chip contact interface has been fabricated. The atomized cutting fluid can be directly delivered to the tool-chip contact interface through the inner microchannel. Experiments were conducted on the new lubrication method, dry cutting, and traditional MQL cutting of 45 steel. The three-dimensional cutting forces and the cutting temperatures were measured. The wear surface of the rake face was analyzed through SEM micromorphology and EDS element detection. The results showed that the main cutting force of the tool with continuous lubrication at the tool-chip interface decreased by 14.5% and 5.9% compared with the conventional tools of dry cutting and MQL cutting. Moreover, the friction coefficient decreased by 14.2% and 9.8%, the length of the tool-chip contact interface decreased by 35.4% and 19.1%, and the amount of cutting fluid was only 1/10 of that in MQL cutting. The new lubrication method had better cutting fluid penetration and lubrication film formation performance than the traditional MQL method on the tool-chip interface. Furthermore, the surface wear of the new lubrication method was significantly reduced, and the main wear form of the new lubrication method was adhesive wear.

Cutting performance and tool wear in laser-assisted grinding of SiCf/SiC ceramic matrix composites

Ceramic matrix composites have high hardness, so their machining requires high grinding forces that cause severe wear of the grinding head. To investigate this problem, the present study investigated the cutting performance of conventional grinding (CG) and laser-assisted grinding (LAG) of SiCf/SiC ceramic matrix composites using electroplated diamond grinding heads. Firstly, a three-dimensional transient heat transfer model based on a Gaussian heat source was developed to observe the surface and internal temperature field distributions of SiCf/SiC ceramic matrix composites subjected to laser irradiation. Secondly, the effects of laser heating temperature on the workpiece surface on the grinding forces were analysed. It was found that the axial and feed grinding forces were more than 40% lower under LAG than CG due to the removal mechanism of the SiC matrix changing from brittle fracture to ductile fracture and the oxidation reactions occurred in the SiCf/SiC ceramic matrix composites. Thirdly, the material removal mechanism was analysed by observing the morphology of machined surfaces, which showed that ductile removal from the SiC matrix occurs during LAG. Finally, it is also founded that the mean height of exposed abrasive grains from machined surface was reduced by 1.02 μm, 12.52 μm in LAG and CG respectively. The forms of wear caused by abrasive grains were studied. Under CG, the abrasive grains mainly exhibit cleavage fractures; while under LAG, micro-abrasion is the main wear form.

Wear behavior of alumina abrasive belt and its effect on surface integrity of titanium alloy during conventional and creep-feed grinding

Abrasive belt grinding is commonly used in the surface processing of key components of major equipment, such as blade, blisk and rail, due to its cold and flexible processing characteristics. Creep feed belt grinding (CFBG) can effectively improve the processing efficiency; however, it will result in severe abrasive belts wear and low grinding quality. This study comparatively investigated the abrasive belt wear behavior and its effect on surface integrity of titanium alloy during CFBG and conventional belt grinding (CBG), It was revealed that CFBG led to more severe abrasive belt wear than CBG, and the main wear form of abrasive belt was abrasive grain fracture (account for more than 40%) during CFBG, while that was abrasive grain attrition during CBG. Besides, the grinding temperature and grinding force in CFBG were more significant than those in CBG. With the increase of the abrasive belt wear, the grinding temperature and grinding force gradually decreased. Furthermore, as the abrasive belt worn, the ground surface was gradually flattened, and the roughness of CFBG reduced from 1.16 to 0.50 μm, while that in CBG reduced from 0.704 to 0.560 μm. Compared with CBG, an apparent plastic flow and oxidation of titanium alloy occurred due to the temperature effect during CFBG, and the surface residual stress transformed from compressive to tensile as abrasive belt wore.

Evaluation of wear mechanism between TC4 titanium alloys and self-lubricating fabrics

Self-lubricating spherical plain bearings are important product components in the aerospace industry. With technological advances, the limitations of steel self-lubricating spherical plain bearings with high quality but poor corrosion resistance became quite evident. The preparation of self-lubricating spherical plain bearings made of titanium alloys is of great interest. In general, titanium alloys have poor tribological properties as well as unsatisfactory tribological performance when they rub with soft self-lubricating fabrics. To understand the wear mechanism of TC4 titanium alloys, half-ring wear tests were conducted between TC4 titanium alloys and self-lubricating fabrics under different pressures and swing frequencies, namely, 50 and 100 MPa, and 0.2 and 0.4 Hz, respectively. The corresponding results showed that the friction coefficients (COFs) between TC4 titanium alloys and self-lubricating fabrics greatly fluctuated in the range of 0.1–0.25. The main wear form of titanium alloys was a combination of abrasive wear and adhesive wear, and the accumulated debris generated during the friction process was the main cause of surface damage of TC4 titanium alloys. The accumulated debris tended to increase with increasing pressure and swing frequency. The debris scratched and made large grooves in titanium alloy surfaces and aggravated the wear of self-lubricating fabrics, which led to severe fibre breakage. This paper describes a novel wear mechanism of accumulated debris and offers a solid theoretical foundation for the application of titanium alloys in the field of self-lubricating spherical plain bearings.

Research on Tribological Properties and Viscoelasticity of EPDM Rubber in the Main Drive Sealing System of Shield Machine

Abstract The tribological properties and wear mechanisms of ethylene propylene diene monomer (EPDM) with different carbon black contents under dry friction conditions are studied on an UMT Tribolab friction and wear tester. The variation of carbon black content in EPDM does not lead to the formation of new compounds. However, it significantly improves the shore hardness and tribological properties of EPDM. In addition, significant stick-slip phenomenon occurs during the wear process of EPDM with different carbon black content. During the wear process of EPDM, there are both adhesive wear and abrasive wear, and adhesive wear is the main wear form. Therefore, the results reveal the relationship between carbon black content and tribological properties of EPDM, which can contribute to improve the tribological properties of EPDM.

Effect of adding different silane coupling agents on metal friction and wear in mixing process

AbstractThe function of silane coupling agent in rubber mixing field is to combine inorganic matrix with rubber organic matrix. Silica is commonly used in the rubber mixing field to strengthen rubber. The size and amount of silica aggregates in the mixing process are important factors affecting the wear of the mixing chamber. The wear of the mixing chamber would lead to a increasing gap between the mixer chamber and the rotor, which caused the mixing efficiency reducing. It also affected the dispersion effect, then affected the mechanical and physical properties of the vulcanized rubber. In this paper, the effects of rubber compound on metal friction and wear were studied by using four silane coupling agents commonly used in rubber mixing field. The experiment was carried out at 15°C, and the attention should be paid to drying during sample preparation to avoid the deviation of the experiment caused by hydrolysis of silane coupling agent. The results showed that silanization reaction occured between silica and silane coupling agent in the mixing process. The mixing temperature was usually maintained at 145 to 155°C for 1 min in the mixer, and the silanization reaction rate was the fastest during this time. We took this rubber compound as the research object and studied the friction and wear of the rubber compound on the mixing chamber in the mixing process. The products of the silylation reaction are alcohol and water. This paper studies the corrosion and abrasion of the mixing chamber by water at high temperatures. In the mixing process, abrasive wear was the main wear form, but the corrosion wear caused by high temperature steam still occupied a large proportion.

Microscopic Study on the Mechanism of Tool Bond Wear in Cutting Ni–Fe-Cr-Co–Cu Series Nickel-Base Superalloy

In the process of nickel-based alloy machining, chips are easy to bond on the tool surface, which weaken the tool performance and make the tool wear. Therefore, it is very important to study the mechanism of tool bond wear in the process of nickel-based superalloy machining. In order to reflect the wear process of the tool from the perspective of micro cutting, the molecular dynamics simulation model for cutting Ni–Fe-Cr-Co–Cu nickel-based alloy with SiC tool was established. The Morse potential functions between the tool and workpiece are calculated, and the simulation results are analyzed visually. It is found that the bond wear is the main wear form of tool in the process of cutting nickel-based alloy, and the wear processes are divided into three stages: contact, adhesion and shedding. The stress and strain in the cutting area are calculated and it is found that the bond occurs when the tool-workpiece extrusion is strong. Through the calculation of radial distribution function and formation energy, it is found that Ni-Si compound is formed on the tool surface, and the newly generated Ni-Si compound reduces the tool performance compared with the silicon carbide structure. This study provides a more complete microscopic explanation of the tool wear mechanism, which is helpful to find a method to prolong tool life.

Multilayer graphene for reducing friction and wear in water-based sand cleaning liquid

Two dimensional (2d) lubricant materials further explore their application in oil and gas field with the research direction of reducing friction and wear. In this study, we added multilayer graphene into water-based sand cleaning liquid to reduce friction and wear of the CT80 coiled tubing. The results showed that the addition of multilayer graphene significantly improved the anti-friction and wear resistance. Adding 0.5% multilayer graphene effectively reduced COF and wear by 75%. Additionally, the higher multilayer graphene concentration, the greater CT80 material withstood the load of severe wear. Multilayer graphene can be adsorbed on the wear debris or form a lubrication film on both worn surfaces, which facilitated the transportation of the debris. Moreover, the wear analysis indicated the main wear form of the CT80 material was abrasive wear and fatigue wear.

Influence of contact form on mechanical wear characteristics of single diamond scratching on Ta12W

Purpose Mechanical wear is the main wear form of abrasive single crystal diamond (SCD) grit. The mechanical wear of SCD grit has a significant influence on the tool life and machining quality. This paper aims to investigate the influence of grit–workpiece contact form on the mechanical wear characteristics of SCD grit. Design/methodology/approach Three different grit–workpiece contact forms, which involved point/line/face contact forms, are investigated to reveal the wear mechanism of SCD grit scratching on Ta12W. The wear morphology, wear volume and scratching forces are measured, and the stress models of different contact forms are analyzed. Findings The results show that mechanical wear mainly occurs in the grit–workpiece contact area and increases gradually from contact area to entire SCD grit. The scratching forces vary with the mechanical wear progress of SCD grits. The SCD grit with point contact form is the most prone to produce wear. The SCD grit with face contact form can remove more material volume than the other two SCD grits, and it is the most wear resistant. The stress state is closely related with the mechanical wear of SCD grit. The contact form has a significant influence on the mechanical wear of SCD grit. Originality/value The results of this study can provide a theoretical basis for the fabrication of abrasive tools.

Effects of in-situ TiB2 particles on machinability and surface integrity in milling of TiB2/2024 and TiB2/7075 Al composites

In-situ ceramics particle reinforced aluminum matrix composites are favored in the aerospace industry due to excellent properties. However, the hard ceramic particles as the reinforcement phase bring challenges to machining. To study the effect of in-situ TiB2 particles on machinability and surface integrity of TiB2/2024 composite and TiB2/7075 composite, milling experiments were performed, and compared with conventional 2024 and 7075 aluminum alloys. In-situ TiB2 particles clustered at the grain boundaries and dispersed inside the matrix alloy grains hinder the dislocation movement of the matrix alloy. Therefore, the milling force and temperature of the composites are higher than those of the aluminum alloys due to the increase of the strength and the decrease of the plasticity. In the milling of composites, abrasive wear is the main wear form of carbide tools, due to the scratching of hard nano-TiB2 particles. The composites containing in-situ TiB2 particles have machining defects such as smearing, micro-scratches, micro-pits and tail on the machined surface. However, in-situ TiB2 particles impede the plastic deformation of the composites, which greatly reduces cutting edge marks on the machined surface. Therefore, under the same milling parameters, the surface roughness of TiB2/2024 composite and TiB2/7075 composite is much less than that of 2024 and 7075 aluminum alloy respectively. Under the milling conditions of this experiment, the machined subsurface has no metamorphic layer, and the microhardness of the machined surface is almost the same as that of the material. Besides, compared with 2024 and 7075 aluminum alloy, machined surfaces of TiB2/2024 composite and TiB2/7075 composite both show tensile residual stress or low magnitude of compressive residual stress.

Tribological Performance of Si3N4-PTFE Composites Prepared by High-Pressure Compression Molding

The tribological performance of ceramic–polymer composites prepared by high-pressure (3 GPa) compression molding of silicon nitride (Si3N4) and polytetrafluoroethylene (PTFE) with epoxy resin (EP) binder was investigated under dry friction conditions. Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy, and energy-dispersive spectroscopy (EDS) were utilized to characterize Si3N4-PTFE-EP composites. The Vickers hardness and shore hardness were tested and the thermal stability was evaluated by thermogravimetric analysis (TGA). The results indicate that the lowest wear rate reaches 10−7 mm3 (Nm)−1 and the lowest friction coefficient is about 0.06. With an increase in the PTFE mass fraction, the main wear form gradually changes from abrasive wear to adhesive wear, but fatigue wear always exists.