Steady-state Wear Research Articles

An experimental and analytical approach to study the sliding wear performance of epoxy composites with steel wire and glass fiber reinforcement

This study investigates the sliding wear behavior of hybrid epoxy composites reinforced with alternating layers of glass fiber mats and steel wire mesh. The objective is to enhance the wear resistance of glass fiber-epoxy composites with the incorporation of steel wire mesh. Three composite types with different stacking sequences are fabricated using the hand layup technique. Dry sliding wear tests are conducted using a pin-on-disc test rig under various operating conditions, following to ASTM G99 standard. Taguchi analysis with L25 orthogonal array identifies sliding velocity as the most influential factor on wear rate, followed by normal load. Steady-state wear analysis is performed to evaluate the effect of each significant factor independently. Analysis of variance results show sliding velocity significantly affects wear rates, contributing 67.63% for glass-epoxy composite (G11) and more than 75% for glass-steel-epoxy hybrid composites (G7S4 & G4S7). A regression model, based on experimental data, predicts specific wear rates with error margins of 3.17% for glass-epoxy composite and less than 2% for glass-steel-epoxy composites. Additionally, electron microscopy is used to analyze worn surfaces, revealing the primary wear mechanisms.

Microstructural and wear properties of iron slag reinforced aluminum alloy (LM30) based composite prepared through a stir casting method

Aluminum alloys are widely used in various industries due to their as low density, high strength-to-weight ratio, and good corrosion resistance. However, their wear resistance is often inadequate for certain applications. Utilization of industrial waste materials, such as iron slag, as reinforcement in aluminum alloy matrix composites offers a sustainable approach to material development and waste management. The utilization of industrial waste materials for aluminum alloy matrix composite fabrication offers a waste utilization to material development. The loading of this reinforcement varied from 0 to 15 wt.% and different particle size range (220-140, 140-70, and 70-0 µm). A microscopic analysis indicated that the iron slag particles are spread uniformly inside the metallic matrix. There is also a reduction in the size of primary silicon, as well as morphological changes (acicular to globular shape). The wear behavior was calculated using a pin-on-disk wear set up in accordance with ASTM G99 standard. The composites were employed to dry sliding wear test under various operating conditions such as applied pressure (0.2–1.4 MPa), and sliding distance (0–3000 m). The 15F composite outperformed all other composite samples in terms of wear rate under all working conditions. When compared to the base alloy, it demonstrated a remarkable 67% drop in steady state wear rate. The enhancements in wear performance for the 15F composite were attributed to the effects of Fe slag reinforcement. The inclusion of iron slag particles induced strong interfacial bonding between matrix and reinforcement particles improving the durability of the mechanical mixed layer developed during relative motion. Importantly, the wear rate parameters of the 15F composite were similar to those of the brake drum material used in commercial applications. This emphasizes the composite suitability for usage in a variety of automobile components.

Investigating run-in and steady-state wear mechanisms of Al-7075 alloy hybrid composite for brake rotor applications

An effective way for creating superior-grade metal matrix composites (MMCs) using Al composites is the stir-casting technique. Stir-casting stands out among the array of available methods, being a frequently adopted technique. This study focuses on producing Al7075/B4C + Al2O3 hybrid MMCs by incorporating different weight proportions of Al2O3 (3–12%) while maintaining a consistent weight proportion of B4C (6%). The microstructural analysis demonstrates that the B4C/Al2O3 particles are evenly dispersed throughout the Al matrix. A complete investigation was carried out to evaluate the Run in and steady state wear mechanism and hardness throughout distinct phases. Notably, when contrasted with the interface and matrix phases, the particle phase (Top phase) of the hybrid composites achieves the highest hardness. The wear rate and coefficient of friction of the composites were both decreased by the addition of B4C/Al2O3 particles. The composites reinforced with B4C/Al2O3 showed the greatest decreases in wear rate and coefficient of friction. A comparison of the wear characteristics of the created composite and the conventional brake drum material, namely cast iron, was also done with regard to industrial sustainability. It was discovered that the wear rate of B4C/Al2O3-reinforced composites was comparable to that of automotive industry-used cast iron brake drums. According to SEM data, abrasive wear at lower stresses and adhesive wear at higher loads mostly helped in material removal.

Running-in Period During Sliding Wear of Austenitic Steels

The running-in period during dry sliding wear might determine the evolution to steady-state wear behaviour. To this end, the running-in period during sliding wear of austenitic stainless steel, AISI 316L stainless steel, and Hadfield steel were studied through the testing pin (flat-ended)-on-disk configuration. The effects of the normal load, sliding speed, and alloy type were assessed, and the specific wear rate and strain hardening characteristics were determined. The wear rate was correlated with wear mechanism, friction coefficient, hardening, and roughness to characterize the changes occurring during the running-in period. These changes could influence the responses of these materials to wear during the steady-state period. The stabilization of the specific wear rate and hardness was noted to align with the end of the running-in period.Graphical

WEAR LOAD CAPACITY OF CROSSED HELICAL GEARS

The paper presents a wear load capacity of crossed helical gears (gear pair consists of a worm and a helical gear). Crossed helical gears are similar to worm gear pairs, and it is logical to extend the load capacity calculation approach of worm gears for the case of crossed helical gears. One of the disadvantages of crossed helical gear sets is very high running-in wear. The paper explains the transition between running-in and steady-state wear and proposes a joint wear calculation model. The paper outlines a proposal to extend the calculation method for wear load capacity from a worm gear pair to the case of crossed helical gears (a worm with a helical gear). This calculation method for determining the wear load capacity of crossed helical gears is verified for the cases when the wheel is of bronze CuSn12Ni2-C-GCB and sintered steel Fe1.5Cr0.2Mo.

Optimum selection of nano-Al2O3, nano-SiO2, and nano-ZrO2 particulate fillers on physical, mechanical, and wear assessment of Al6061 nanocomposite using preference selection index

The present study investigated the role of three important nano-sized fillers such as nano-SiO2, nano-ZrO2, and nano-Al2O3 on mechanical and wear assessment of Al6061 alloy matrix composite and suggested the optimum compositions for the best performance for Al6067 alloy matrix composites. Preference selection index as optimization tool was used and attributes taken for optimizations were void content, hardness, tensile strength, flexural strength, fracture toughness, impact strength, specific wear rate at normal load of 25 and 55 N load, sliding velocities of 0.5 and 2 m/s, sliding distance of 500 and 2000 m, respectively. In general, all three nanofillers enhanced the mechanical and wear properties of Al6061 alloy matrix composite. In the steady state wear study, on increasing normal load from 25 to 55 N, the specific wear rate of Al6061, Al6061-3Al2O3, Al6061-3SiO2, and Al6061-3ZrO2 was increased by 58.7%, 33.2%, 15.4%, and 26.14%, respectively. On increasing sliding speed from 0.5 to 2 m/sec, the specific wear rate of Al6061, Al6061-3Al2O3, Al6061-3SiO2, and Al6061-3ZrO2 was increased by 27%, 13%, 6%, and 12%, respectively. On increasing sliding distance from 500 to 2000 m, the specific wear rate of Al6061, Al6061-3Al2O3, Al6061-3SiO2, and Al6061-3ZrO2 was increased by 41%, 36%, 9%, and 21%, respectively. Al6061-3SiO2 indicated the best composition in terms of mechanical and wear performance followed by Al6061-3Al2O3 and Al6061-3ZrO2. Hence, nano-SiO2 can be suggested as the best filler to enhance the mechanical and wear performance of Al6061-based nanocomposite. Therefore, nano-SiO2 reinforced Al6061 composite is indicated as the best suitable composite material for a large number of components in structural, automobile, marine, and aerospace industries.

ПРОГНОЗИРОВАНИЕ ИЗНОСОСТОЙКОСТИ ПАР ТРЕНИЯ СКОЛЬЖЕНИЯ

The necessity to predict optimal wear resistance of sliding couplers at the design stage is grounded. A tribological analysis of the wear of sliding couplers is carried out during the entire period of operation in various modes corresponding to the following stages: start-up, steady-state wear and shutdown. The existing approaches to solving contact problems in the interaction of solids, taking into account physico-mechanical processes in the surface layers of couplers during their wear, are analyzed. A wear model is proposed based on the destruction of the contacting surfaces of a coupler with the separation of particles, which size varies depending on the load characteristics, physico-mechanical and structural parameters, thermal properties, quality of the lubricant, etc. The results of testing prototypes for wear resistance and numerical implementation of the proposed model for predicting the wear resistance of a sliding coupler with similar characteristics are presented. It is found out that the proposed wear model makes it possible to predict (calculate) the wear resistance of a sliding coupler in a certain range by changing the initial data, thereby eliminating the need for rather laborious tests of couplers for wear under the influence of various factors.

Minimum 7-year results of cementless total hip arthroplasty with vitamin E-diffused and 2-methacryloyloxyethyl phosphorylcholine-grafted highly cross-linked polyethylene.

The purpose of this study was to evaluate the mid-term clinical results and polyethylene wear of vitamin E-diffused highly cross-linked polyethylene (HXLPE) and 2-methacryloyloxyethyl phosphorylcholine (MPC)-grafted HXLPE in cementless total hip arthroplasty (THA). Thirty-four THAs with vitamin E-diffused HXLPE (VEPE) and 32-mm cobalt-chromium head, and 116 THAs with MPC-grafted HXLPE and 32-mm alumina head were evaluated. The Merle d'Aubigné and Postel scores were administered. Kaplan-Meier survivorship was analyzed. Annual radiographs were analyzed using computerized method and linear steady-state wear rate was measured. The mean duration of follow-up was 9 years (range, 7-11 years) in VEPE group and 8 years (range, 7-10 years) in MPC group. The mean Merle d'Aubigné and Postel scores improved postoperatively in both groups. Kaplan-Meier survivorship with endpoint of revision was 100% (95% confidence interval, 100%-100%) in VEPE group and 98.3% (95% confidence interval, 93.4%-99.6%) in MPC group at 10 years (P = .44). The mean steady-state wear rate was 0.007 mm/year in VEPE group and 0.006 mm/year in MPC group (P = .60). The clinical results of both groups were good and wear rates of both liners were very low.

Influence of Artificially Altered Engine Oil on Tribofilm Formation and Wear Behaviour of Grey Cast Cylinder Liners

This work investigates the influence of altered engine oil on the tribological performance, focusing in particular on wear and interconnected tribofilm formation. For this purpose, Zinc dialkyldithiophosphate (ZDDP) additivated engine oils of different degradation levels, produced in an artificial oil alteration process, were used in tribometer tests with a nitride steel piston ring against a grey cast iron cylinder liner model contact. Parameters were chosen to simulate the boundary and mixed lubrication regime typical for the top dead centre conditions of an internal combustion engine of a passenger car. Wear of the cylinder liner specimens was continuously monitored during the tribometer tests by the radio-isotope concentration (RIC) method, and tribofilms were posteriorly investigated by X-ray photoelectron spectroscopy (XPS). The results clearly show that the steady-state wear rates for experiments with altered lubricants were significantly lower than for the experiments with fresh lubricants. XPS analysis on the formed tribofilms revealed a decrease in sulphide and an increase in sulphate states for altered oils evaluated at 120 °C oil temperature, correlating with a decrease in steady-state wear rate. This finding emphasizes the role of sulphate species in the tribofilm formation process and its anti-wear capabilities, in contrast to the sulphide species and the (poly-)phosphate species, as outlined in most of the ZDDP literature. Moreover, the RIC signal that represents the amount of wear in the engine oil showed a decrease over time for specific altered lubricants and test conditions. These “negative” trends in the wear signal are remarkable and have been identified as an incorporation of wear particles from the lubricant into the tribofilm. This finding is supported by XPS results that detected an iron-oxide layer with a remarkably similar quantity within the tribofilm on the surface. Based on these findings, an assessment of the minimum film formation rate and particle incorporation rate was achieved, which is an important basis for adequate tribofilm formation and wear models.

Dry Friction and Wear Behavior of Laser-Sintered Graphite/Carbon Fiber/Polyamide 12 Composite.

Carbon fiber-reinforced polymers (CFRPs) are being used extensively in modern industries that require a high strength-to-weight ratio, such as aerospace, automotive, motorsport, and sports equipment. However, although reinforcement with carbon fibers improves the mechanical properties of polymers, this comes at the expense of abrasive wear resistance. Therefore, to efficiently utilize CFRPs in dry sliding contacts, solid lubricant is used as a filler. Further, to facilitate the fabrication of objects with complex geometries, selective laser sintering (SLS) can be employed. Accordingly, in the present work, graphite-filled carbon fiber-reinforced polyamide 12 (CFR-PA12) specimens were prepared using the SLS process to explore the dry sliding friction and wear characteristics of the composite. The test specimens were aligned along four different orientations in the build chamber of the SLS machine to determine the orientation-dependent tribological properties. The experiments were conducted using a pin-on-disc tribometer to measure the coefficient of friction (COF), interface temperature, friction-induced noise, and specific wear rate. In addition, scanning electron microscopy (SEM) of tribo-surfaces was conducted to specify the dominant wear pattern. The results indicated that the steady-state COF, contact temperature, and wear pattern of graphite-filled CFR-PA12 are orientation-independent and that the contact temperature is likely to approach an asymptote far below the glass transition temperature of amorphous PA12 zones, thus eliminating the possibility of matrix softening. Additionally, the results showed that the Z-oriented specimen exhibits the lowest level of friction-induced noise along with the highest wear resistance. Moreover, SEM of tribo-surfaces determined that abrasive wear is the dominant wear pattern.

Developing a steady state wear equation for AA7050 hybrid composites/steel interface at elevated temperature

ABSTRACT In this research work, an attempt was made to reinforce AA7050/5Gr composites with multi-walled carbon nanotube (MWCNT) of varying weight percentages processed through stir casting route. SEM with EDS mapping revealed that the particles were uniformly distributed over the composites. Hardness reduces with increasing MWCNT weight percentage owing to the inverse hall petch effect and increment in void content. A third-body abrasion, which happens when the CNT in the aluminium matrix material detaches from the surface and erodes material from the composites pin as well as the counter face, causes the wear resistance to rise with the addition of CNT particles. A mechanically mixed layer, which avoids direct metal-to-metal contact and thus increases wear resistance, was created at the abraded surface and at high temperature, where the reduction of wear rate was due to the development of oxide protective layer. A steady-state wear equation for the contacting surface at high temperature (R = 1/Y √(ln W/2X)) for AA7050 hybrid composites–steel interface was developed. The enhancement in wear resistance was directly proportional to the proportion of ferrous content present on the surface, which was confirmed on the elemental analysis. Pock marks, micropits, craters and cracks were the features observed on the worn surface morphology, whereas delamination and plasticisation were the observed modes of wear mechanism.

In vivo creep and wear performance of vitamin-E-diffused highly crosslinked polyethylene in total hip arthroplasty.

An acetabular liner thickness of around 6mm remains the "gold standard" in total hip arthroplasty. Some surgeons have been recommending the use of the thickest possible liner because contact stress and strain in articulating surfaces decrease with increasing the wall thickness. The purpose of this study was to determine whether in vivo creep and wear performance could be enhanced using a thicker liner over the standard thickness in vitamin-E-diffused highly crosslinked polyethylene (HXLPE). One hundred and twenty-two hips were allocated to age-matched, sex-matched, and body mass index-matched two subgroups implanted either with a 6.8- or 8.9-mm-thick vitamin-E-diffused HXLPE liner against 28-mm cobalt-chrome femoral head, and followed-up for 7years. Linear and volumetric penetration of femoral head into the liners attributed to creep and wear were analyzed for each group. Compressive creep strain generated at the initial 6months was significantly larger in the 6.8-mm group (2.6%) than in the 8.9-mm group (2.2%). The linear steady-state wear observed after 2years was 0.0019 and 0.0015mm/year, whereas the volumetric steady-state wear was 0.54 and 0.45 mm3/years in the 6.8- and 8.9-mm-thick groups, respectively. Although less strain in the thicker group resulted in a slightly less wear, it did not reach significant differences in the steady-state wear rates between the groups. No clinical significance for using a thicker liner over the standard thickness (6.8mm → 8.9mm) was confirmed in the vitamin-E-diffused HXLPE according to the 7-year follow-up. The wear rates for both thicknesses were very low enough to prevent osteolysis, and no mechanical failure was observed at any follow-up interval. Nevertheless, since the significantly higher strain was seen in the thinner liner, further follow-up is needed to compare the longer term wear and the incidence of osteolysis and component fracture.

Deep learning-based CNC milling tool wear stage estimation with multi-signal analysis

In this work, the convolutional neural network (CNN), which is a deep learning method in which the features are extracted by an inner process, was performed to detect the wear stages of the milling tool. These stages that define the total lifespan of the tool are known as initial wear (IW), steady-state wear (SSW), and accelerated wear (AW). Short Time Fourier Transform (STFT) was applied to signals, and signal spectrograms were used to train CNN models with different complex architectures. Vibration signals, acoustic emission signals, and motor current signals from The Nasa Ames Milling Dataset were used to obtain the spectrograms. Pre-trained CNNs (GoogleNet, AlexNet, ResNet-50, and EfficientNet-B0) detected the tool wear stage with varying accuracies. It has been seen that the time duration of model training increases as the size of the dataset grows and the network architecture becomes more complex. The recommended method has also been tested on the 2010 PHM Data Challenge Dataset. CNN shows promise for condition monitoring of milling operations and detecting tool wear stage.

Topography rules the ultra-mild wear regime under boundary lubricated gross-slip fretting corrosion

Fretting corrosion of biomedical taper junctions has raised concerns about adverse local tissue reactions. A low release of ions and other reaction products into the body is desirable, and this can be achieved by, e.g., optimizing the topography. Retrieval analysis has revealed that circumferential machining marks with high ridges and low valleys reduce the release of wear products. Thus, we hypothesized that a rougher titanium surface decreases metal release under gross-slip fretting because of a change in wear mechanisms. Fretting tests (polished CoCr29Mo6 alloy pins (Ra ≈ 0.006 μm) against fluted Ti6Al4V cylinders (Ra ≈ 5.6 μm)) were carried out. The worn surfaces were analyzed using SEM and LRS (Laser-Raman Spectroscopy) while ICP-MS of the lubricant (BCS) rendered the wear loss. Results were compared with the wear loss of identically polished CoCr29Mo6 pins rubbing against fine-machined Ti6Al4V cylinders (Ra ≈ 0.245 μm) reported earlier. The fluted topography led to microploughing and microcutting on both CoCr29Mo6 and Ti6Al4V surfaces, triggering tribocorrosion and mechanical mixing of tribomaterial containing Cr-, Mo-, and Ti-oxides and denatured/cleaved proteins. While friction was controlled by mechanical-dominated microploughing and microcutting the steady-state wear was characterized by chemical-dominated tribocorrosion. The total wear loss of the fluted system was half of the fine machined system, albeit the Co-side lost more. Despite the rougher topography the tribomaterial still acted as boundary lubricant and protected the surfaces.

A new hypothesis of steady-state flank wear progression of cutting tools with similar geometry and its verification

A new hypothesis is proposed and verified in this study to clarify the relationship between the progression and the mechanism of the flank wear of cutting tools in the steady-state region, assuming that the flank wear part expands while maintaining a geometrically similar profile. Based on Preston's law, the proposed hypothesis analytically leads to the conclusions that in the steady-state wear region where the cutting temperature is low and the abrasive wear is dominant, the flank wear width increases linearly, and the normal stress on the flank wear part does not change. Furthermore, this hypothesis suggests that the nonlinear and faster wear progression in the initial wear region is caused by an unsteady transition in the flank wear profile. Cutting experiments were conducted using tungsten carbide tools and carbon steel workpieces. The results demonstrated that the flank wear part expands with a certain similarity profile in the steady-state wear region. The normal stress distribution on the flank wear part was estimated from the similarity profile based on the proposed hypothesis, and the result was in rough agreement with that calculated by the finite element method in the literature.

Impact of processing defects on microstructure, surface quality, and tribological performance in 3D printed polymers

Additive manufacturing (AM), also known as three-dimensional (3D) printing, of polymer-based materials is growing as a time-efficient, economical, and environmentally sustainable technique for prototype development in load-bearing applications. This work investigates the defects arising from the processing in material extrusion-based AM of polymers and their impact on the part performance. The influence of raster angle orientation and printing speed on tribological characteristics, microstructure, and surface finish of acrylonitrile butadiene styrene (ABS) fabricated in a heated build chamber was studied. Comprehensive analysis with fractography and tomography revealed the formation, distribution, and locations of internal voids, while surface defects were studied with the topography analysis of as-printed surfaces. Surface roughness and tribological results show that printing speed can be optimally increased with a minimal impact on interlayer bonding and part performance. Increased printing speed allowed up to 58% effective reduction in printing time obtaining comparable mechanical properties at varying process parameters. 3D printed ABS exhibited dry sliding friction coefficients in the range of 0.18–0.23, whilst the maximum specific wear rate was 6.2 × 10−5 mm3/Nm. Higher surface roughness and increased printing speed exhibited delayed running-in during dry sliding, while insignificant influence was observed for steady-state friction and wear behaviors. The findings indicate that improved surface finish and reduced internal defects can be achieved with a controlled build environment allowing for higher printing speed. The observations in this study are evidence that 3D printing can be adapted for the sustainable manufacturing of polymeric components for tribological applications.

Initial tool wear and process monitoring during titanium metal matrix composite machining (TiMMC)

When machining titanium metal matrix composites (TiMMCs), the abrasiveness of the reinforcement particles of this material leads to numerous machinability challenges, namely severe tool wear and poor machined surface quality. This paper aims to study the initial tool wear and the phenomena occurring during machining of titanium metal matrix composites. Initial wear refers to tool wear that occurs early in the cutting process. When the tool life is relatively short, the initial wear could significantly influence the remaining machining process. Therefore, a better understanding of the initial tool wear mechanisms and characteristics could lead to solutions extending the tool life, thereby improving the cutting process and production efficiency. Hence, the flank tool wear was assessed and thoroughly investigated using a scanning electron microscope (SEM), an energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). A tool condition monitoring system (TCMS) for online tool wear evaluation was employed to detect the transition times between wear stages during the machining process.Based on results, the types of wear in the initial zone were characterized. Abrasion, adhesion and cracking are considered as the critical morphological changes. The reduction of workpiece surface damage and tool wear rate could be related to the formation of a protective layer as a thermal barrier at the first transition time, when the initial tool wear ends and the steady state wear region begins. This moment, as the first transition time can be a short period, less than 15 s, which was detected by fractal analysis of force and vibration signals during machining of TiMMCs. The clear signatures of the transition times were suggested by the results of the fractal analysis.

Transient Wear FEA Modelling Using Extrapolation Technique for Steel-on-Steel Dry Sliding Contact

Total wear in transient regime consists of transient wear and linear wear components. Within the transient regime metal possess higher wear rates than the steady state. FEM computational based wear models ignore transient regime which leads to higher error. This paper emphases on predicting the total wear in transient regime of 316 stainless steel pin against AISI 52100 bearing steel disc for 20 N and 30 N.Novel methodology is proposed to calculate individual wear components. Linear component by FEM based Abaqus software using an extrapolation technique to reduce computational time without compromising the accuracy. Transient component is calculated using Gauss Newton regression method. Further, total wear is modelled by addition of linear and transient wear components. Simulated total wear has good agreement with experimental wear error within 11% for both the loads. Corresponding transient wear rate was found to be approximately 2.5 times higher than steady state wear. This establishes the robustness of proposed methodology.

A Ten-Year Radiostereometric Analysis of Polyethylene Wear Between Oxidized Zirconium and Cobalt Chrome Articulations in Total Hip Arthroplasty.

Oxidized zirconium (OxZi) femoral heads combine the decreased abrasive properties of ceramics with the toughness of metal alloys to lower wear and increase the durability of total hip arthroplasty. The purpose of this study was to compare the 10-year polyethylene wear rates between OxZi/XLPE and cobalt chrome (CoCr)/XLPE articulations. A radiostereometric analysis (RSA) was performed on two cohorts of 23 patients who underwent total hip arthroplasty using either OxZi/XLPE or CoCr/XLPE at a minimum of 10-year follow-up. Cohorts were matched for age, gender, body mass index (BMI), and diagnosis. Polyethylene wear was measured using RSA to determine total and steady-state wear rates for both cohorts. Preoperative and postoperative patient-reported outcome measures (SF12, HHS, and Western Ontario and McMaster Universities Arthritis Index scores) were compared. The mean total head penetration rate was found to be statistically different between the entire cohorts (OxZi 0.048±0.021 mm/y, CoCr 0.035±0.017 mm/y, P= .02) but not when 28-mm heads only (OxZi 0.045±0.016 mm/y, CoCr 0.034±0.017 mm/y, P= .066) were directly compared. The mean steady-state wear rate was not significantly different between the entire cohorts (OxZi 0.031±0.021 mm/y, CoCr 0.024±0.019 mm/y, P= .24) or 28-mm head cohorts (OxZi 0.028±0.019 mm/y, CoCr 0.024±0.019 mm/y, P= .574). Outcome measures showed no statistical difference except for the Harris Hip Score where the OxZi cohort demonstrated higher median scores. Using RSA to evaluate the 10-year in-vivo head penetration, there was no statistically significant difference in steady-state wear rates between OxZi and CoCr articulations. Both bearing combinations demonstrated wear rates well below the threshold for osteolysis.

Wear assessment of a Ti–6Al–4V motion-preserving porous artificial-cervical-joint fabricated by SLM after surface carburization

Adjacent segment degenerative diseases are a major clinical concern for anterior cervical corpectomy with fusion surgery. In this study, a hybrid motion-preserving cervical prosthesis consists of two articulating joints and one porous fusion body is designed to provide motion ability and reduce the occurrence of degenerative diseases. The hybrid design is fabricated from Ti–6Al–4V (TC4) alloy using selective laser melting (SLM) technology. After carburization pretreatment, two types of bearing couple SLM-TC4 self-mating and SLM-TC4/UHMWPE were studied in terms of lubrication regime, contact mechanics and wear performance. According to the ISO 18192-1 standard, five million cycles (Mc) of in vitro spine simulator wear tests were conducted in bovine serum lubricated condition.Hamrock-Dawson minimum lubrication film thickness analysis stated that both bearing was likely under boundary lubrication only, with extensive surface asperities contact. And, the contact stress encountered during in vitro condition was not enough to cause surface fatigue failure of any bearing couple. In term of wear performance, the obtained steady state wear rates were 0.160 ± 0.004 mm3/Mc for SLM-TC4 self-mating and 8.57 ± 0.06 mm3/Mc for SLM-TC4/UHMWPE bearing couples, respectively. According to these outcomes, SLM-TC4 self-mating couple was more promising for the articulating joint bearing design.For SLM-TC4 self-mating couple, the initial wear mechanism was abrasion with potential third-body abrasion wear. As the wear cycle proceeding, the TiC cermet layer was gradually damaged and exposed the local bare metal. Under this circumstance, material loss was consisted of abrasion wear, adhesion wear, and tribo-corrosion. In comparison, the wear mechanism of SLM-TC4/UHMWPE bearing was always abrasion-adhesion of UHMWPE. The surface of UHMWPE socket was severely plowed by the hard micro bulge of the TiC layer, and material loss and plastic deformation occurred only on the UHMWPE socket. In conclusion, carburization pre-treatment causes a hard TiC cermet layer formation on the SLM-TC4, which enhance its hardness and protect underling material from corrosion damage. The thickness and quality of the TiC layer directly affect the longevity of the joint prosthesis in vivo.