Wear Process Research Articles

In vitro degradation and dry sliding wear behaviour of AZ31-Sn/Al2O3 nano metal matrix composites in simulated body fluid for biomedical application

In this research, tin was added to the AZ31/2Al2O3 magnesium metal matrix composite to investigate its influence on degradation rate in the presence of simulated body fluid (SBF) and wear behaviour in dry conditions. The AZ31- xSn/2Al2O3 ( x = 0, 2, 4, 6, 8, and 10 wt%) composites were manufactured using the bottom pouring stir casting route. The microstructure of the manufactured AZ31/2Al2O3 and AZ31- xSn/2Al2O3 composites revealed that they were composed of the α-Mg solid solution and the intermetallic compound □-Mg17Al12, which was situated near the grain boundaries. When tin was added, the Sn-rich intermetallic compound Mg2Sn was formed, increasing the volume fraction of the Mg2Sn phase. Compared to AZ31/2Al2O3 composite, the wear test revealed that AZ31/2Al2O3 composites containing Sn particles exhibited a higher ability to generate more stable tribo-layers at higher applied loads, which protected the worn surface and reduced the wear rate. The wear resistance of composites was improved primarily by the behaviour of the tribo-layer in the wear process. The degradation rates (mm/year) of the AZ31 composites were carried out for 72 h in SBF. The degradation rate was reduced when the Sn content in the AZ31/2Al2O3 composite was increased to 6 wt% and then increased with further Sn addition. It was observed that when the amount of Sn particles increases up to 6 wt%, the severity of the degradation decreases.

Tool Wear Monitoring with Artificial Intelligence Methods: A Review

Tool wear is one of the main issues encountered in the manufacturing industry during machining operations. In traditional machining for chip removal, it is necessary to know the wear of the tool since the modification of the geometric characteristics of the cutting edge makes it unable to guarantee the quality required during machining. Knowing and measuring the wear of tools is possible through artificial intelligence (AI), a branch of information technology that, by interpreting the behaviour of the tool, predicts its wear through intelligent systems. AI systems include techniques such as machine learning, deep learning and neural networks, which allow for the study, construction and implementation of algorithms in order to understand, improve and optimize the wear process. The aim of this research work is to provide an overview of the recent years of development of tool wear monitoring through artificial intelligence in the general and essential requirements of offline and online methods. The last few years mainly refer to the last ten years, but with a few exceptions, for a better explanation of the topics covered. Therefore, the review identifies, in addition to the methods, the industrial sector to which the scientific article refers, the type of processing, the material processed, the tool used and the type of wear calculated. Publications are described in accordance with PRISMA-P (Preferred Reporting Items for Systematic review and Meta-Analysis Protocols).

Failure diagnosis and physical interpretation of journal bearing for slurry liquid using long-term real vibration data

Pumps are important machines used in rivers, social infrastructure, and industrial facilities. During long-term operation, journal bearings that support the pump shaft are subject to wear and peeling caused by liquids, including slurry. Wear and peeling can change the characteristics of journal bearings and cause abnormal shaft vibration. If wear and peeling progress, it can severely damage the pump. Thus, periodic maintenance and replacement are required. However, the frequency of periodic maintenance should be reduced as much as possible from a cost standpoint. Therefore, it is desirable to monitor the condition of the machine and perform maintenance only when necessary. In this study, the long-term vibration of a submerged journal bearing with slurry-containing water was monitored and recorded to identify the features that are important for condition monitoring and diagnosis and to interpret their contributions. First, an experimental test rig for a rotating shaft system was developed and long-term vibration data and changes in wear were recorded. A machine learning model (support vector machine (SVM)) was trained to predict the wear and damage conditions of the bearings, and its effectiveness was verified. In addition, two important features were selected as major contributors to the wear and peeling phenomena of journal bearings. These important features were interpreted using partial dependence (PD), Individual Conditional Expectation (ICE), and SHapley Additive exPlanations (SHAP), and the degree of contribution and characteristics of these features were clarified. Later, a reduced SVM model was trained using only these important features, and its effectiveness was clarified using another bearing’s data of wear and peeling processes.

A study on predicting the wear of TBM disc cutters using Cerchar testing

Estimating the disc cutter wear life or change time is a critical part of performance prediction for the application of hard rock TBMs. This paper examines the disc cutter wear rate and the number of required discs during the excavation of the Kanisib (or Zab) tunnel based on the transpositioning concept. The study covers the disc changes due to the normal wear process, leaving out those replaced due to mechanical/bearing failures. This study also analyzes TBM field performance and actual cutter consumption using a method, specific mass loss per volume (SMLV) excavated. SMLV considers the wear mass of a disc cutter relative to the disc cutters replacement for a given volume of excavated rock. Generally speaking, the disc SMLV incorporates critical parameters, and a formula is introduced to calculate it from the rock properties. The new model can be utilized for estimating disc life for any disc cutter size, diameter, and tip width. The predictive model developed in this study allows for estimating cutter life based on the location of disc cutters on the cutterhead. The proposed model uses rock mass parameter, namely the rock quality designation (RQD), and rock material parameters measured in a laboratory, including rock abrasion and strength. Rock abrasion is estimated by Cerchar abrasivity index (CAI) or modified Cerchar abrasivity index (MCAI). Furthermore, a new approach to Cerchar indices has been used, which is based on the pin mass loss instead of pin tip flat size, and as a result, new indices called CAIML and MCAIML are introduced. The correlation between predicted and observed values shows that the proposed model for specific mass loss per volume can predict the normal wear of disc cutters. Furthermore, the Cerchar indices calculated using the pin mass loss offered better correlations with field data than those specified based on the diameter of the pin tip flat. Overall, MCAIML exhibited the best correlation with the field observations compared to the other Cerchar indices.

Simulation Analysis of Stir Tool Wear Considering the Effect of Temperature Rise caused by Material Deformation on Flow Stress

Background: Wearing is a prominent problem in friction stir welding. The material flow stress equation is a key factor that decides the accuracy of the simulation of the wearing process. Objective: We aim to propose a material flow stress equation based on material true stress and true strain curve, which takes proper factors into account and leads to good accuracy in numerical simulation of stir tool wear. Methods: The value of the material temperature rise caused by the material deformation heat and the value of the effect caused by the temperature rise on flow stress was calculated, and the effect value was used to modify the material flow stress and the related curve, and then the modified flow stress equation was obtained. On this basis, the equation was used to simulate the stir tool wear, and the simulation results were compared with those results without considering the effect of temperature rise. Results & Discussion: the wear amount of the stir needle when considering the effect of temperature rise is significantly less than that when the effect of temperature rise is not considered. Conclusion: In the simulation of the wear of the stir tool, it is necessary to adopt the modified flow stress equation considering the effect of temperature rise.

Mechanical and tribological properties of aluminium based metal matrix composites: An overview

This paper presents a comprehensive review of open literatures to segregate the effects of composite fabrication process parameters, reinforcement types and its contents on mechanical and tribological properties of the developed metal matrix composites (MMCs). Effects of various wear factors (i.e. load, sliding speed and sliding distance) on wear rate (WR) and coefficient of friction (COF), along with different dominating wear mechanisms are emphasized. Outcomes of the review revealed that increase in stirring time affects the mechanical properties adversely, whereas increase in ball milling time improves these. Incorporation of ceramic and carbonaceous reinforcements in Al alloy improves its mechanical and wear resistance properties. Effects of wear process parameters on WR and COF depend upon the types of matrix-reinforcement combinations, reinforcement content and test conditions.

Results of modelling the effect of temperature on the thickness of the surfactants layer

Problem. Earthmoving machines operate under high loads, so their tribo-joints periodically operate under unsteady load conditions, which leads to their increased wear and, as a result, a rapid decrease in the residual service life of the units and the reliability of the machines in general. Under unsteady load conditions, friction in the joints of hydraulic drive elements occurs under the boundary lubrication regime. This lubrication mode occurs at high contact loads, high temperatures in the contact zone, and relatively low sliding speeds of the mating surfaces. The combination of boundary lubrication and high dynamic loads often leads to partial destruction of the boundary layer. This leads to direct contact of individual micro-irregularities of the friction surfaces, which is accompanied by a wear process. Hence the importance of the quality of both the parameters of the surface layer of friction surfaces and the parameters of the applied lubricant (oils, working fluids) on the strength and wear resistance of hydraulic drive elements. Goal. The aim of this work is to determine the effect of temperature and radius of curvature of a microroughness on the thickness of the layer of surface-active substances adsorbed on it. Methodology. The solution of the tasks involved the formation of a model of adsorption-desorption equilibrium in the system "working fluid - micron-surface", taking into account the ambient temperature, and its application to determine the dependence of the thickness of the adsorbed surfactant layer under conditions of temperature change. Results. The thickness of the adsorption layer depends mainly on the size of the adsorbing surface field and the energy of thermal vibrations of molecules. It decreases with increasing PP and increases with increasing radius of curvature of the micron roughness. The change in the thickness of the adsorption layer of surfactant molecules on the surface of the micron roughness with a change in the temperature of the RS is not uniform. With an increase in the PP temperature within 300...400 K, the thickness of the adsorption layer of surfactant molecules on the surface of the micron roughness decreases by ~24 %. With an increase in the temperature of the PP in the range of 400...450 K, the thickness of the adsorption layer of surfactant molecules on the surface of the microroughness decreases by ~76 %. The formation of a surfactant adsorption layer on the surface of the microroughness at a temperature above 443 K stops. Originality. A model of the formation of a surfactant adsorption layer on the surface of a separate microroughness on the basis of adsorption-desorption equilibrium in the system "working fluid - microroughness surface" was proposed, taking into account the ambient temperature, which allows us to analyse the nature of the temperature effect on the thickness of the adsorbed surfactant layer. Practical value. The use of the proposed mathematical model makes it possible to estimate the parameter of the surfactant adsorption layer on the surfaces of microroughnesses and rough friction surfaces based on the ambient temperature and the geometry of individual microroughnesses.

Influence of crystallographic effect on tool wear, cutting stress, cutting temperature, cutting force and subsurface damage in nano cutting of single crystal silicon carbide

Single crystal 3C-SiC as a typical hard and brittle material. Due to its extremely high hardness and brittleness, diamond tools can have drastic wear problems in a short period of time when performing nano-machining processes. Single-crystal 3C-SiC has good anisotropy. In order to gain insight into the effect of crystal orientation on the tool wear behavior during nano-cutting, this paper investigated the tool wear for six cutting crystals downward using molecular dynamics simulation. The tool wear process was analyzed in terms of tool wear, cutting stress, cutting temperature, cutting force and subsurface damage. The results showed that the tool is subjected to large hydrostatic stress concentrations, radial forces and tool temperature concentrations during machining. Under these effects, abrasive wear, graphitic wear and amorphous phase change were produced. In addition, the clearance face of the tool is more severely worn than the rake face. By reasonably selecting the cutting crystal orientation, well control and improvement of tool wear and machined surface quality can be achieved.

An Atlas of the Knee Joint Proteins and Their Role in Osteoarthritis Defined by Literature Mining

Osteoarthritis (OA) is the most prevalent rheumatic pathology. However, OA is not simply a process of wear and tear affecting articular cartilage but rather a disease of the entire joint. One of the most common locations of OA is the knee. Knee tissues have been studied using molecular strategies, generating a large amount of complex data. As one of the goals of the Rheumatic and Autoimmune Diseases initiative of the Human Proteome Project, we applied a text-mining strategy to publicly available literature to collect relevant information and generate a systematically organized overview of the proteins most closely related to the different knee components. To this end, the PubPular literature-mining software was employed to identify protein-topic relationships and extract the most frequently cited proteins associated with the different knee joint components and OA. The text-mining approach searched over eight million articles in PubMed up to November 2022. Proteins associated with the six most representative knee components (articular cartilage, subchondral bone, synovial membrane, synovial fluid, meniscus, and cruciate ligament) were retrieved and ranked by their relevance to the tissue and OA. Gene ontology analyses showed the biological functions of these proteins. This study provided a systematic and prioritized description of knee-component proteins most frequently cited as associated with OA. The study also explored the relationship of these proteins to OA and identified the processes most relevant to proper knee function and OA pathophysiology.

Wear characteristics of single-layer cBN abrasive tools using ultrasonic vibration–assisted induction brazing techniques

Single-layer brazed superhard abrasive tools have been widely employed in grinding of difficult-to-machine materials in aerospace, aiming at the improvement of the grinding performance and quality. However, the chemical metallurgical reaction during conventional induction brazing (CIB) is severe, and the brazing quality is poor, resulting in a rapid wear and thus reducing service life of abrasive tools. In this case, the single-layer brazed cBN abrasive tools were fabricated using ultrasonic vibration-assisted induction brazing (UVAIB) technology, and the wear comparative experiments of Ti–6Al–4V alloys was carried out using UVAIB and CIB abrasive tools. Results indicate that compared to the CIB abrasive tool, the UVAIB abrasive tool has the higher average exposure height of abrasive grains, lower grinding forces and more stable grinding force ratio during wear processes. Meanwhile, the UVAIB abrasive tool has a slowly decreased exposure height of abrasive grains, a superior wear state and low proportion of macro-fracture as the material removal volume raises. In addition, UVAIB abrasive tool possesses micro-cracks at the top of abrasive grains, leading to micro-fractures of abrasive grains to improve the self-sharpening ability and grinding performance.

Influences of B4C and carbon nanotubes on friction and wear performance of Cu base self-lubricating composite

Mechanical and friction performance of Cu base composites strengthened by B4C and carbon nanotubes (CNTs) were investigated. The CNTs vary between 2 vol% −6 vol% and B4C proportion is a set number 2 vol%. SEM, EDS and TEM were applied to characterize the polished composite surface, worn surface, cross section of friction layer, and debris. The wear mechanisms of all samples were explored. Compared with pure copper, both the physical and wear properties of the composite are improved. The composite containing 4 vol% CNTs and 2 vol% B4C has the lowest, steadiest friction coefficient and the highest wear resistance among all materials. This is attributed to combining effects of B4C and CNTs with the proper proportion. It not only enhances the composite’s mechanical properties, but promotes a continuous and uniform self-lubrication layer forming between friction pairs during the wear process. The wear mechanisms of pure Cu and composites (2, 4, 6 vol% CNTs) are severe plastic deformation and adhesion, abrasive wear, slight abrasive wear, abrasive and slight adhesive wear, respectively.

Erosion by turbulence: Discovering the counter-wise vortex events and their effect on wear

Understanding the wear process has been critical for developing and maintaining engineered systems handling particle-laden flows, such as pipelines, valves, pumps, and mixers. This work explores the use of ultrasound velocimetry for determining the velocity and impact angle of particles projected from a turbulent slurry flow onto a moving target surface. The flow is generated in a slurry pot configuration at four levels of rotational frequency: 1900, 2200, 2500 and 3300 rpm. Acoustic images acquired in the B-mode are processed by Ultrasound Particle Tracking Velocimetry (U-PTV) and Ultrasound Particle Image Velocimetry (U-PIV) to determine the impact velocities and impact angles of individual particles in the radial plane. Particle impacts at velocities higher than the tangential velocity of the rotating axis are observed and named counter-wise impact due to their association with counter-wise vortices impacting in the direction contrary to the translation of the moving surface. The applicability of U-PTV and U-PIV for the study of particle-laden turbulent flow is discussed and a statistical analysis of particle impacts energy is conducted. The counter-wise impacts are found relevant to erosive wear because of their relatively high velocity (upper quartile) and because most of the impact energy is conveyed through the tangential component.

A hybrid analytical-FEM 3D approach including wear effects to simulate fretting fatigue endurance: Application to steel wires in crossed contact

Fretting fatigue causes failures in steel wire ropes. A crossed wires set-up was used to investigate the influence of displacement amplitude on fretting fatigue damage. The analysis confirms previous literature results, showing a beneficial effect of wear in gross slip regime, which extends the contact area and thus decreases the contact stresses. The computation of such combined cracking and wear processes is very expensive using a classical FEM strategy, particularly for 3D contact geometries. To palliate such limitations, a hybrid analytical-numerical strategy was developped. It consists in estimating pressure and shear stress surface fields using analytical formulations, then to transpose these fields to an FEM model. This allows to simulate contact geometry modifications in a fast and efficient way.

New two-stage running-in process with particle effect in three-body lubrication

Running-in is essential for improving the performance and lifetime of a machine. This study proposed a two-stage running-in procedure based on the lubrication regime and nanoparticle effect to increase running-in efficiency; the method was verified using a disk-on-block experiment. The first stage involved wearing down the high peaks of the surface asperities in relatively severe mixed lubrication. The second stage was a mild wear process, in which the shape of the asperity peak was trimmed with soft CuO particles in three-body mixed lubrication. The CuO concentrations were divided into three concentration variations (0.1 wt%, 0.5 wt%, and 1.0 wt%) to investigate the effect of CuO concentration on the smoothing surface processes. The tribological parameters, including the surface roughness value, peak radius of asperity, plasticity index, adhesion index, real contact area, true friction power intensity (TFPI), and modified true friction power intensity (MTFPI) index, were investigated to evaluate the friction coefficient, wear, and anti-scuffing performance. The result after first stage showed that the surface roughness value decreased to similarly low values for the different initial roughness values. After the second stage of the trimming process, the asperity peak radius, contact angle, real contact area, plasticity index, and anti-scuffing improved considerably. The obvious reduction in the friction coefficient in the second stage was due to the decrease in ratchet friction, deformation, and plowing friction. These methods effectively enhanced the efficiency of the running-in process.

Investigation of erosion wear performance and mechanism of mold materials

Abstract The surface of an injection mold is prone to erosion and wear under the impact of the filler during plastics injection molding, which leads to premature failure of the mold. The mechanism of erosion and wear of a filler on the mold has not been clarified yet. A numerical technique was employed to simulate the erosion and wear process, and the influence of environmental parameters and particle characteristics, such as erosion velocity, erosion angle, temperature, and particle shape were studied. The results showed that the erosion velocity and erosion angle are important factors that affect erosion and wear. Finally, the relationship between change of particle energy and erosion and wear of the material is studied from the perspective of energy.

Influence of surface burnishing process with single strain path and reciprocating strain path on copper wear behavior

A single strain path (SSP) and reciprocating strain path (RSP) burnishing processes are implemented on copper surfaces using a multi-ball surface burnishing tool. Dry wear tests are performed on both machined samples to investigate the effect of different strain paths on the wear behavior. A backscattered scanning electron microscope and nanoindentation are operated to characterize the microstructure and mechanical properties between samples machined via different strain paths. Molecular dynamics models are developed to explore the mechanism that enhances wear resistance through the gradient grain structure in the surface layers machined by SSP and RSP. The wear test results show that the wear scar volumes of the SSP treated samples are about 70% of the original samples, while the RSP treated samples are about 60%, indicating that the RSP further enhances the wear resistance of copper. Compared to SSP machining, RSP machining activates the Bauschinger effect in the copper to produce the gradient structure with a larger thickness (500 μm–700 μm) and greater hardness (1.72 GPa–1.82 GPa). Consequently, RSP machining further improves the resistance to crack initiation and expansion, resistance to plastic deformation, total strain capacity, and elastic recovery in the wear process, which is why samples machined with RSP have better wear resistance.

Three-dimensional finite element simulations of fretting wear in steel wires used in coal mine hoisting system

Fretting wear is a surface damage phenomenon that occurs at contacting surfaces due to the micro relative movements of contacting surfaces. It is not easy to consider the parametric study of this phenomenon by experimental methods. For example, it is not straightforward to measure the contact stresses and wear scars under different loading conditions during the experimental process. Furthermore, the experimental process is economically expensive and time-consuming. In this paper, the fretting wear behavior of steel wire ropes used in coal mine technology is numerically investigated and the results are compared with experimental data. The numerical results of the effect of contact parameters on the fretting wear process during the fretting cycles are also analyzed. For this purpose, a three-dimensional Finite Element (FE) model is created and validated with an analytical solution. The simulations of the FE model are performed using the commercially available FE tool ABAQUS combined with subroutine UMESHMOTION. The available experimental data of fretted wires in the form of coefficient of friction is used to define the interaction between the contacting surfaces of FE model and the maximum wear depth is used to validate the wear depth obtained through the numerical model. A convergence study is also carried out to select the most suitable parameters for the simulation of contacting surfaces. After the validation of the FE model, the effect of fretting amplitude, contact load and different contacting angles of fretted wires on wear characteristics is considered. The results show that higher fretting amplitude and contact load have a significant effect on wear profile, wear depth, and wear scar. The maximum wear depth, wear depth increasing rate and contact stress decreasing rate is high for higher contact angles compared to smaller contact angles.

Dry sliding wear and friction behavior of powder metallurgy FeCoNiAlSi0.2 high-entropy alloys

Wear behaviors of the FeCoNiAlSi0.2 high-entropy alloy (HEA) and Si-free FeCoNiAl during the reciprocating sliding wear process were evaluated for automotive piston rings. The HEAs were prepared using on advanced powder metallurgy route to solve the inherent shrinkage porosity and segregation defects during casting, poor densification, and wear resistance of HEAs while reciprocating motion. The morphology, hardness, wear, and friction properties were investigated. FeCoNiAl had biphasic face-centered cubic (FCC) and body-centered cubic (BCC) solid solution structures, whereas FeCoNiAlSi0.2 HEAs had a single BCC solid solution structure. Si addition significantly enhanced the hardness and wear resistance of the HEAs under reciprocating conditions because of the increased solid solution strengthening and lattice distortion effects. The maximum hardness of the FeCoNiAlSi0.2 HEA reached approximately 582 HV, which is higher than that of the equiatomic FeCoNiAl HEA (491 HV). The findings depict that FeCoNiAlSi0.2 maintains better tribological behavior than FeCoNiAl HEA against the tungsten carbide (WC) ball indenter. Oxidative delamination and cracking occurred in the FeCoNiAl/WC pair, whereas a mixed adhesive–abrasive wear mechanism was prominent in the FeCoNiAlSi0.2/WC pair because of the harder BCC solid solution phase. This study explores an effective strategy for enhancing the tribology behavior of automotive piston structures under varying loads and reciprocating dry sliding motions.

Numerical simulation and experimental study on adhesion effect of powder lubricating layer

PurposePowder lubrication is widely used in industrial production, but most of the research that analyze the wear process and speculate on the wear mechanism of the tested specimens lacks reliability, and it is difficult to reveal the essence of the friction and wear process. The purpose of this paper is using the optical in situ observation method to observe the condition of the powder lubrication layer in real time and dynamically, and directly obtain the morphology change of the specimen during the whole wear process, which is helpful to the establishment of new tribological basic theories such as friction and wear mechanism and lubrication theory.Design/methodology/approachMechanical model of powder lubrication is established considering asperity and powder layer, and the influence of adhesion effect on load and friction force is analyzed. The finite difference method is used to solve the above physical model, and the influence of the adhesion effect on load and friction force is analyzed. The total load and friction of the friction pair are composed of two parts: fluid and asperity. Based on the optical in situ observation method to build a test platform. The interface of the adhesion stage was observed by SEM.FindingsWhen the film thickness ratio is less than 1, the local damage and diffusion of the powder layer are basically completed and the adhesion stage is entered. At this time, the asperity is not fully loaded, the powder layer is loaded by 50%, the asperity is less loaded, the deformation is small and the possibility of plastic flow is reduced. However, in the adhesion stage, the friction force is basically generated between asperity, and the friction force ratio of the asperity is 80%. Heavy load and surface roughness of the specimen are the necessary conditions for the powder adhesion period.Practical implicationsIn this paper, the failure process of the powder layer at the friction interface with different roughness and load is studied based on the optical in situ observation method. Second, the contact surface with the micro-convex body and powder layer is simulated, and the influence of adhesion effect on the mechanical properties of the real contact surface in the process of powder lubrication is analyzed, thus providing theoretical guidance for mechanical processing, workpiece operation and lubrication design.Originality/valueMechanical model considering asperities and powder layer powder lubrication was established to analyze the influence of the adhesion effect on load and friction. Based on the optical in situ observation method to build a test platform. The tests found that the failure process of the powder lubricating layer includes five stages: powder complete stage, local failure stage, local failure diffusion stage, powder adhesion stage and complete failure stage.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0322/

Sliding Friction and Wear Behavior of Flash-Welded U75V Steel Joints in Air and Water Environments

U75V high-strength steel has been widely used to improve the service life of high-speed rails. Considering the consecutive cold and wet condition of the Sichuan–Tibet highway, water plays an important role in the wear process of U75V welded joints. In this study, we investigated the wear behaviors of flash-butt-welded U75V joints in dry air and water environments using a ball-on-disk sliding wear tester. The worn surfaces were tested using optical microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The cross-sectional profiles of the wear scar were tested using a wear volume tester. The results show that the U75V welded joint has a lower wear resistance than the base metal owing to its nonuniform structure and exhibits a high friction coefficient (0.64) and wear loss (0.21 mm3) in dry air. Water exerts a lubricating function on the fretting wear of U75V welded joints and reduces the friction coefficient (0.36) and wear loss (0.15 mm3). Furthermore, abrasive wear and micropitting are predominant in water environment, accompanied by the formation of a protective-oxide layer on the surface. In contrast, microcutting and microcracking are the dominant wear mechanisms of U75V welded joints in dry air.