Initial Surface Roughness Research Articles

Research on prediction method of surface roughness in weak magnetorheological shear thickening fluid polishing

A joint prediction method of “mathematical modeling and finite element calculation” is proposed to improve the prediction of machining quality in weak magnetorheological shear thickening fluid polishing of complex surfaces. The study proceeded in several steps. First, based on both impact energy model and material removal model, a numerical prediction model of surface roughness is established. Second, based on the multi-peak fitting method, the field-induced rheological properties of the polishing fluid are characterized and material properties of the flow field medium in the polishing zone are defined. Third, the numerical boundaries of polishing flow velocity and shear stress in the above prediction model are obtained. Fourth, the polishing experiments with parameters consistent with the above simulation model are conducted, and the initial surface roughness values are substituted into the above prediction model. The results show that the joint prediction method can effectively predict the machining quality of workpiece surface. The absolute error of Sa value of surface roughness is up to 10.6 nm, and the maximum relative error is 12.3%.

Surface roughness and gloss alteration of polished resin composites with various filler types after simulated toothbrush abrasion

Background/purposeFew studies have focused on the influence of simulated toothbrush abrasion on the surface qualities of novel nanofilled and nanohybrid composites. The aim of the study was to evaluate the surface roughness and gloss values of resin-based composite (RBC) materials with various filler types before and after simulated toothbrush abrasion. Materials and methodsOne nanofilled (Filtek Z350 XT [FT3]), two nanohybrids (Harmonize [HM] and Clearfil Majesty [CM]) and one microhybrid (Filtek Z250 [FT2]) were evaluated. Twelve specimens of each material were made and polished with silicon carbide sandpapers. Initial surface roughness and gloss values were measured as negative controls. Then, all specimens were subjected to simulated toothbrush abrasion on a custom-made apparatus. After 2000, 4000 and 8000 cycles, the surface roughness and gloss values of all specimens were tested. One additional specimen from each group was selected for scanning electron microscope (SEM) analysis. ResultsFor FT3, Ra and GU values did not significantly change until after 8000 cycles during the process of toothbrushing (P > 0.05). For HM, CM and FT2, the Ra and GU values significantly decreased after 4000 and 8000 cycles of toothbrush abrasion (P < 0.05). After 8000 cycles of toothbrush abrasion, FT3 presented the lowest surface roughness and highest gloss values of all materials (P < 0.05). SEM images showed that surface textures and irregularities corresponded to the results of surface roughness and gloss. ConclusionSurface roughness and gloss after simulated toothbrush abrasion were material dependent. Nanofilled resin composite presented the lowest Ra values and highest GU values.

Femtosecond laser polishing of additively manufactured parts at grazing incidence

Surface polishing is usually a requisite for making additively manufactured (AM) parts ready for practical applications. Due to its advantages of being flexible and noncontact, laser polishing has attracted increasing research interest. In this research, femtosecond (fs) laser polishing was established to post-process both the top surfaces and sidewalls of AM parts. The challenge to remove three levels of roughness (i.e., the initial surface roughness of the AM parts, the undulations newly introduced during fs laser polishing, and the micro-nanoscale surface features induced by fs laser irradiation) was identified and addressed. Mirror surfaces with Sa < 200 nm were achieved on stainless steel parts printed with an initial roughness >20 µm. Both parallel- and perpendicular-incidence were investigated for the polishing, with the former verified to be more effective in eliminating the initial roughness of the AM parts, due to the elongated focal intensity profile of a Gaussian beam irradiated on the AM part surfaces. The challenge of forming three-zone surfaces during the parallel-incidence was further addressed through a grazing-incidence polishing approach, and uniform smooth surfaces were realized. Fine-tuning the laser power enabled controlling the submicron surface features formed under fs laser irradiation, which determined the final achievable surface roughness.

Micro/nanoscale bioactive oxide coatings on Ti6Al4V fabricated by SLA and induction heating

Titanium (Ti)-based implants with micro/nano multiscale structures have been highlighted in dental and orthopedic fields due to the enhanced osteogenic abilities and mechanical interlocking. In this study, induction heating treatment (IHT) was developed to superimpose nano structure on microrough sandblasted and acid-etched (SLA) Ti6Al4V surface. The influences of SLA and IHT on the phase compositions, microstructures, properties, and formation mechanism of the coatings were explored. IHT for 12, 18 and 24 s realize the transformation of initially generated nanodot-like crystallites into a relatively uniform and high density of nanoscale protuberances. The oxide coating obtained by SLA + IHT has larger grains compared with that obtained by IHT separately. The nanoscale protuberances comprise crystalline rutile TiO2 and a small amount of α-Al2O3. IHT results in a successive increase of roughness on smooth surface with extension of IHT period, while samples induction heated for 18 and 24 s following SLA retain the initial microscale roughness of SLA surface. Since the larger porosity inside the oxide and local plastic deformation from SLA enhance adsorption and interaction ability of Ti6Al4V with oxygen, the thickness of oxide coating obtained by SLA + IHT increases to 861 nm compared with the 408 nm formed by IHT for 24 s. The micro/nano-structured oxide coating is in favor of improving the hydrophilicity of SLA surface in terms of the decreased contact angle from 129.4° to 69.1°, and shows good capability to induce hydroxyapatite deposition in simulated body fluid.

Quasicylindrical Waves for Ordered Nanostructuring.

Laser-induced self-organization of periodic nanostructures on highly absorbing materials is widely understood to be due to interference between laser and surface plasmon polaritons (SPPs) that are excited by initial surface roughness. The structure order naturally emerges from the propagation phase of SPPs. Here, we reveal an unexplored mechanism that is predominantly induced by quasicylindrical waves (QCWs) with negligible contributions from SPPs. This mechanism features a new principle of order emergence in growth of periodic nanostructures through short-range electromagnetic interactions between QCWs and marginal nanofringes. In this scenario, the periodicity of nanostructures is not simply determined by the electromagnetic wavelength. With suppressed long-range interactions, the formation of nanostructures shows a domino-like growth process, thus significantly improving structure uniformity. An in situ microscopic observation is performed to characterize the temporal dynamics of structural growth and verify the new mechanism. Further, the QCWs are directly observed in experiments, which are theoretically supported by a scattering model.

Effect of roughness and acidic medium on wear behavior of dental resin composite

BackgroundThe aim of the study was to investigate whether the citric acid and rough surface have a synergistic effect leading to severe wear behavior of resin composite.Materials and methodsDisk-shaped (Ø15 × 1.5 mm) specimens of resin composite (n = 12) with different initial roughness were prepared. Reciprocating ball-on-flat wear tests were performed under distilled water and citric acid (pH = 5.5) respectively. The coefficient of friction (COF), wear volume loss, and duration of the running-in period were quantified to assess the wear performance. And the values were analyzed with one-way ANOVA (α = 0.05). Regression analysis was applied to examine the influence of Ra values and mediums on the wear data. The wear morphology was analyzed by scanning electron microscopy and a 3D profilometer.ResultsThe average COF was higher in distilled water than in citric acid but was independent of the surface roughness. For the composite, the volume loss of worn area and running-in period increased with surface roughness when tested under distilled water. However, these increasing trends were not found in citric acid. All specimens exhibited mild wear behavior with low COF and less superficial abrasion in acidic medium.ConclusionsThe effect of initial roughness on wear behavior depends on the medium. In distilled water, resin composites with high initial roughness exhibit a longer running-in time, which eventually leads to a significant increase in material loss. The adverse effects of high roughness can be alleviated by the lubrication of citric acid, which can maintain a mild wear behavior regardless of initial surface roughness.

Study on Size Effect of Surface Roughness Based on the 3D Voronoi Model and Establishment of Roughness Prediction Model in Micro-Metal Forming

The primary purpose of this paper is to study the size effect of surface roughness and realize the quantitative description of the surface roughness in micro-forming process. This work is a continuation of the previous work by the authors. The effects of the initial surface roughness of the specimen, the grain size, and grain orientations on the surface roughness of micro-upsetting products were investigated. The ratio of the number of grains of the surface layer to the total number of grains was adopted to characterize the size effect. The variation of the size effect on the contact normal pressure during the compression process was also analyzed. And the quantitative description of the evolution law of surface roughness for micro-formed parts was realized. The corresponding micro compression experiment was done in order to testify the prediction model.

Investigation on the grain size effect on the copper shaped charge jet stretching behavior

The grain size effect on the shaped charge jet (SCJ) stretching process was analytically formulated and experimentally verified by penetration tests. The present analytical model predicts an optimum grain size for the SCJ performance, deduced from the concurrent effect of grain size on flow stress, strain rate sensitivity, and surface roughness. Specifically, reducing the grain size will improve the initial surface roughness and decrease the initial perturbation amplitude, favoring the SCJ stretching. On the other hand, the strain rate sensitivity and flow stress for copper increase with the decrease of grain size, facilitating the perturbation growth and leading to a premature breakup. Thus, the present analytical model predicts that the optimum grain size of the SCJ is about 1–5 μm. The penetration test verified that the shaped charge liner with an average grain size of about 3.6 ± 2.5 μm exhibited the largest penetration depth. The consistent results from the analytical model and the penetration experiments certify the feasibility of the present analytical model on the SCJ performance.

Impacts of Surface Texture and Nature of Friction on Energy-Force Efficiency of Surface Plastic Deformation during Burnishing

Burnishing, the plastic deformation of the workpiece surface due to sliding contact with a tool called burnisher, is a finishing operation widely used in various industries. In this work, impacts of the initial surface roughness Ra of the workpiece being burnished, the nature of friction in the contact zone, and the clamping force on the stability and energy efficiency of burnishing have been investigated. Experiments have been conducted with and without lubricant, represented by low-viscosity deep-hydrogenated fraction of sour oils, at initial surface roughness Ra of 0.8 and 1.25 μm and variable (100–200 N) clamping force. A key process indicator, which largely controls mechanics of burnishing, the temperature in the tool-workpiece contact zone has been measured using natural thermocouple method. Microhardness of the workpiece surface after burnishing has also been measured. It has been shown that changes in the temperature of the tool-workpiece contact zone are proportional to the changes in the squared tool clamping force. This dependence appeared to be universal and equally applicable to burnishing with and without lubrication. Based on the analysis of the experimental data, a new criterion of the burnishing efficiency has been developed. The new criterion simplifies the choice of optimum operational parameters and helps in preventing adverse impacts of structural phase transformations in the workpiece surface layer that unavoidably lead to reduced product quality and operational reliability and in reducing tool wear, which is critically important in the case of dry burnishing. The obtained results show that the nature of friction accompanying the surface plastic deformation has a significant impact on the stability and energy efficiency of the burnishing process. While the clamping force is equally important for burnishing with and without lubrication, the initial roughness Ra has an impact on dry burnishing only. Application of minimum quantity lubrication (MQL) under experimental conditions typical for industrial burnishing is found to be favorable. In particular, it was shown that MQL not only enhances the stability of burnishing process and but also increases its energy efficiency by more than 20%.

On the wetting behavior of laser-microtextured stainless steel using Direct Laser Interference Patterning

Microtextures generated by pulsed lasers allow for changing the surface properties of a wide palette of materials by replicating nature's most effective topographies. In the case of laser-induced microtextures, the surface's wetting properties evolve over time and eventually stabilize. The size of the fabricated features and the initial surface roughness strongly influence this transition and play a key role in the determination of the final wetting state. This work aims to study the wettability of textured stainless-steel with two different surface finishes. Nanosecond Direct Laser Interference Patterning was applied to fabricate a wide range of dot-like microtextures that were evaluated in terms of surface roughness. The water contact angle was monitored for up to 90 days, showing a transition from hydrophilic to hydrophobic. Applying the Wenzel model, the wettability transition was analyzed in regard to surface roughness, and the transition of the average Young contact angle could be extrapolated. In the steady-state, the textured surfaces exhibited the rose-petal effect, where contact angles up to 154.4° were attributed to the microtextures, while a simultaneous high drop adhesion could be related to the initial surface finish. Measurements with water and diiodomethane showed that the textures were both hydrophobic and oleophilic in the steady-state. The surface free energy was estimated and decreased on all textures compared to the untextured reference.

Laser Polishing Die Steel Assisted by Steady Magnetic Field.

To improve the surface roughness of SKD61 die steel and reduce the secondary overflow of the molten pool, a steady magnetic field-assisted laser polishing method is proposed to study the effect of steady magnetic field on the surface morphology and melt pool flow behavior of SKD61 die steel. Firstly, a low-energy pulsed laser is used for the removal of impurities from the material surface; then, the CW laser, assisted by steady magnetic field, is used to polish the rough surface of SKD61 die steel to reduce the material surface roughness. The results show that the steady magnetic field-assisted laser polishing can reduce the surface roughness of SKD61 die steel from 6.1 μm to 0.607 μm, which is a 90.05% reduction compared with the initial surface roughness. Furthermore, a multi-physical-field numerical transient model involving heat transfer, laminar flow and electromagnetic field is established to simulate the flow state of the molten pool on the surface of the SKD61 die steel. This revealed that the steady magnetic field is able to inhibit the secondary overflow of the molten pool to improve the surface roughness of SKD61 slightly by reducing the velocity of the molten pool. Compared with the molten pool depth obtained experimentally, the molten pool depth simulation was 65 μm, representing an error 15.0%, thus effectively demonstrating the accuracy of the simulation model.

Whitening efficacy of popular natural products on dental enamel.

The objective of this study was to evaluate the effect of natural bleaching products on the color, whiteness, and superficial properties of dental enamel. Seventy fragments of bovine teeth were obtained (6mm x 6mm x 2mm). Initial surface roughness (Surfcorder SE1700, Kosakalab), microhardness (HMV-2, Shimadzu), color (EasyShade, VITA), and surface gloss (Micro-Gloss 45º BYK, Gardner) readings were done. Samples were separated into five groups (n=14) according to the treatments used: CT-conventional toothpaste (negative control); CH-charcoal; TU-turmeric; BP-banana peel, and CP16%-16% carbamide peroxide gel (positive control, 4 h/day for 14 days), and then brushed for 560 cycles (T1) and 1200 cycles (T2), equivalent to 14 and 30 days of brushing. New measurements were performed after T1 and T2. The whiteness index for dentistry change (∆WID) and Weight loss (Wl) were calculated. CP16% demonstrated the highest (p<.05) color change (ΔE00) and ∆WID (2-way ANOVA, Bonferroni, p<.05). Surface gloss alterations were lower for TU, CP16%, and BP. CT and CH increased surface roughness (p<.05). CP16% decreased enamel microhardness. CH presented medium abrasiveness, and CT and TU, low abrasiveness. The popular bleaching products were not efficient for tooth whitening. Furthermore, brushing with charcoal increased the enamel surface roughness, and CP16% decreased enamel microhardness over time.

Modeling and Performance of Continuous Wave Laser Polishing of Electron Beam Melted Ti6Al4V

Continuous wave laser polishing is a promising technique for post-built smoothening of rough metallic surfaces produced by additive manufacturing. In laser polishing, a laser source melts a thin surface layer and redistributes the material resulting in a reduction of surface roughness. This paper develops a first principles-based three-dimensional numerical model for continuous wave laser polishing. The model is validated by comparing the simulated melt pool dimensions to laser polished rolled Ti6Al4V samples. The model predictions of melt pool diameter and melt depth are within 10% of the experimental results. Further, the performance of continuous wave laser polishing as a method to polish rough surfaces of electron beam melted Ti6Al4V parts is investigated. Laser polishing resulted in a maximum reduction of ∼87.6 % in surface roughness average, reducing it from 10.5 microns to 1.3 microns. The melt depth predictions from the numerical model were compared with those of polished electron beam melted samples. The model underestimates the melt depth as it assumes an initially flat surface and does not account for the energy accumulation due to light entrapment between peaks and valleys of the rough electron beam melted surface. It was also observed that this energy accumulation due to initial surface roughness has a significant impact at higher scan speeds than at lower scan speeds.

Mathematical Modeling of Material Removal and Surface Roughness in Ultrasonic-Assisted Magnetic Abrasive Flow Machining Process

Abstract Ultrasonic-assisted magnetic abrasive flow machining (UAMAFM) process shows enhanced finishing performance compared to conventional abrasive flow machining (AFM). In this present research paper, mathematical models for M˙R and Ra have been developed for the UAMAFM process by considering both steady-state and transient phenomena. The external ultrasonic and magnetic field assistance enhanced the velocity and length of contact of active abrasives, calculated from the kinematic analysis. The resultant finishing forces have also been evaluated by considering these external aids. The steady-state material removal per finishing cycle remains constant and depends on the velocity of motion, length of contact, resulting forces, number of active abrasives, and work material hardness. The transient material removal per finishing cycle was calculated in terms of the volume of irregularities present over the work surface, i.e., initial surface roughness. The mathematical model for surface roughness was developed in terms amount of material removed (MR), and initial (Ra0) and critical surface roughness (Racr). The predicted values of material removed and surface roughness from developed mathematical models agreed with experimental results with a deviation of 7.80% and 2.44%, respectively.

Surface roughness evaluation and whitening efficiency on tooth enamel after using whitening toothpaste: a randomized double-blinded study

The aim of this randomized double-blinded study was to evaluate the enamel surface roughness and color change after one month of whitening toothpaste use and the color stability obtained 1 month after its interruption. 30 volunteers were divided into 3 groups (n = 10) corresponding to the dentifrices: 1) Colgate Total 12 Clean Mint (TD) (Control), 2) Colgate Luminous White (LW) and 3) Sensodyne Whitening Extra Fresh (SB). The volunteers were impression with addition silicone to obtain an epoxy resin replica of the upper central incisor for the initial surface roughness evaluation using a profilometer and the initial color of the incisors and canines was evaluated with a spectrophotometer after one week of wash-out. After 1 month, the color of the central incisors and canines was measured again, and the volunteers were molded to obtain a second replica to the final roughness analysis. Data were submitted to ANOVA-one way (p≤0.05). The results showed that there was no statistical difference between the dentifrices for color difference and surface roughness for all the studied conditions. It was possible to conclude that the whitening dentifrices used in this study were not able to alter the initial color of the teeth and did not cause changes in the surface roughness of enamel.

Response surface methodology based parametric study for AISI H13 die steel using customized designed 3D printed Ti64 multi-nozzle polishing tool

The work presents a study on FJP polishing of AISI H13 die steel using 3D printed multi nozzle (dual orifice) polishing tool and Silicon Carbide (SiC) abrasive slurry. It presents a simultaneous effect of feed rate and spindle rotation on the percentage change in surface roughness (%[Formula: see text]). Central Composite Design (CCD) method was used to design the experimentation plan and Analysis of Variance (ANOVA) was performed to evaluate the optimum values of the process parameters. The regression model developed for the FJP process was validated by polishing the AISI H13 workpiece with 39[Formula: see text] average initial surface roughness with the optimized process parameters; feed rate of [Formula: see text] and spindle rotation of [Formula: see text]. The optimized FJP parameters were able to generate the surface roughness of [Formula: see text]. The results obtained from the confirmatory experiments were found to be very close to the predicted results which validated the developed regression model. To further enhance the polishing efficiency, the optimum process parameters were used to polish AISI H13 die steel workpiece, the surface roughness was reduced from 390 to 110 nm in 15 min with 12 number of passes which shows the reduction in peaks and valleys with surface improvement of 71.79%.

Surface roughness prediction and optimization in the REMF process using an integrated DBN-GA approach

Surface roughness is a crucial factor affecting the surface quality of workpieces in manufacturing industries. Thus, it is important to provide an accurate performance of surface roughness prediction and optimal parameters to reduce the burden of time and costs during the process. In this study, two predict models, namely multiple linear regression and deep belief network (DBN) models, were performed to accurately predict change in surface roughness in the rotational electromagnetic finishing (REMF). Compared to the statistical-based model, the data-driven model based on the DBN architecture was a significantly considerable effect on surface roughness prediction in the REMF process. Among the considered DBN models, DBN5 architecture as [7, 14, 14, 1] showed effective features of the nonlinear relationship between process parameters and response with the highest determination coefficient (R2) of 0.9340 and the lowest mean squared error (MSE) of 1.3037 \(\times\) 10−3 in the testing datasets. In addition, a genetic algorithm (GA) as a heuristic optimization technique was adopted to optimize the input parameters of the best derived DBN model. It showed that the maximum change in surface roughness was 0.530 at particle length of 3 mm, particle diameter of 0.7 mm, particle weight of 1.3 kg, liquid water quantity of 1.0 l, a rotational speed of 1323 rpm, working time of 35 min, and initial surface roughness of 2.5478 m\(\upmu\).

Characterization of wear resistance and corrosion during magnetorheological fluid assisted finishing (MFAF) of Ti-6Al-4V and duplex stainless steel for enhanced biocompatibility

The sustainability of biomaterials relies on their interaction with the proteins, fluid, and cells present inside the human body. The biomaterials’ enhanced surface roughness parameters and mechanical properties (i.e. wear resistance) are responsible for reducing degradation (i.e. corrosion rate) to enhance life span during musculoskeletal interaction. The present study compares the biocompatibility between two biomaterials (i.e. Ti-6Al-4V and DSS) polished through the Magnetorheological Fluid Assisted Finishing ( MFAF) process. MFAF process can produce nano-level average surface roughness ( Ra) and is used to improve the quality of the biomaterial's surface. However, apart from Ra, two other surface roughness parameters, namely skewness ( Rsk) and kurtosis ( Rku) analyze the characteristics of the irregularities formed on the polished surface. During the MFAF process, Trochoidal, a high-speed surface finishing toolpath, is used to map the workspace on the Duplex Stainless Steel ( DSS) and Ti alloy (Ti-6Al-4V) biomaterials to enhance their biocompatibility with a reduced finishing time. However, during the pin-on-disc wear tests, an Ultra High Molecular Weight Polyethylene ( UHMWPE) is used as the disc to imitate the interface of the bone with the implants for analyzing wear resistance. During experimentation, it is observed that the wear resistance of DSS and Ti-6Al-4V is improved to 3.19 × 10−6 and 0.123 × 10−5 mm3/min from its initial value of 7.65 × 10−6 and 2.68 × 10−5 mm3/min, respectively. Furthermore, the dependency of initial surface roughness parameters over the wear resistance of the biomaterials is also analyzed. A three-electrode-based electrochemical test with 0.5 M NaCl concentration is utilized to replicate the human body fluid while analyzing the corrosion resistance of the biomaterials. It is observed that the MFAF process enhances the corrosion resistance of the DSS and Ti-6Al-4V to 0.0037 and 0.0114 mm/year, from its initial values of 0.0079 and 0.0130 mm/year, respectively.

Improving the surface integrity of laser cladded layer by ultrasonic-assisted burnishing at medium temperature with considering initial surface conditions

Improving the surface integrity of laser cladded layer via burnishing is an important research topic in remanufacturing field. However, the initial surface roughness condition induced by mechanical machining generates great influence on the strengthening mechanism of subsequent burnishing. In this study, the effects of ultrasonic-assisted burnishing (UB) and ultrasonic-assisted warm burnishing (UWB) on the surface integrity of laser cladded layer were analyzed when treated on different surface conditions obtained by turning with different feed parameters. The results indicated that both the UB and UWB treatments would cause great improvements in microhardness, surface roughness including height and functional parameters, and residual stress of the laser cladded layer when compared to those by turning. First, the severe plastic deformation in UB and UWB treatments counteracted the thermal softening effect in turning process, so that the machined surface could maintain high hardness. Second, UB treatment reduced the roughness by 70% compared with turning, while the surface roughness after UWB treatment was even 30% lower than that obtained by UB. Third, the tensile residual stress shifted to deep compressive state by both UB and UWB treatments, though the thermal load in UWB generated a negative effect on generating compressive residual stress. According to the surface integrity evaluation results by radar diagrams, turning with feed f = 0.2 mm/r and UWB is preferred in machining of the laser cladded layer for enhanced surface integrity. On the basis of this research, it is expected to achieve the purpose of high-efficiency and high-quality cutting of the laser cladded layer.

Bio‐tribological characterisation of ultra‐high molecular weight polyethylene against different metal counterparts

Excessive wear is a key issue affecting the performance of ultra-high molecular weight polyethylene (UHMWPE)-based artificial prosthesis. This work is focussed on the bio-tribology behaviours of UHMWPE when mating with different metal counterparts (iron-based 316L, Co-based Stellite-S21 and Stellite-S22). According to the ASTM F732 standard, two million cycles comparative wear tests were carried out under bovine serum lubrication. When coupled with S21, S22, and 316L metal counterparts, the obtained average wear factors of UHMWPE were 1.333 ± 0.192, 1.360 ± 0.160, and 1.190 ± 0.177 × 10−6 mm3/N · m, respectively. Initial surface roughness of the metal counterpart has shown an important role in controlling the volume of UHMWPE wear, especially the first one million cycles. Compared with 316L, CoCrMo-based counterparts possessed relative higher hardness and exhibited less rise in surface roughness caused by wear. For UHMWPE-on-metal bearings, random scratch, surface pit, and wear debris attachment were commonly seen, which suggested the coexistence of abrasion, third-body abrasion, and adhesion-based wear. In contrast, the metal counterpart was slightly scratched with no polymer transfer film formation. The work conducted in the present study gives useful knowledge regarding the UHMWPE-on-metal bearing design. With an intention to minimise wear, surface roughness of metal counterpart should be carefully controlled.