Volumetric Wear Rate Research Articles

Study on Wear and Corrosion Resistance of Ni60/WC Coating by Laser Cladding on Reciprocating Pump Plunger: Comparison with Flame-Sprayed Plungers.

Reciprocating pumps are widely used in the current oil extraction process, and the plunger is a vulnerable part of these pumps that directly determines the service life of the reciprocating pump. To improve the service life of plungers, Ni60/WC coatings were applied to the surface of 45-steel plungers via laser cladding technology to improve wear and corrosion resistance. Defect-free and dense Ni60/WC coatings were successfully applied to the plunger surface with strong metallurgical bonding between the coating and the substrate. The coating consists mainly of a γ-(Ni, Fe) phase, which contains isotropic and isotropic-like crystals, dendritic crystals, and columnar crystals in the top, middle, and bottom regions of the coating, respectively. The service performance of the laser cladding coating was compared to the flame-sprayed plunger, which is widely used, and the laser cladding coating has a microhardness of up to 821.8 HV0.5, which is higher than that of the flame-sprayed coating (545.5 HV0.5) and the 45-steel substrate (200 HV0.5). The laser cladding coating has a lower friction coefficient and a smaller volumetric wear rate, and the corrosion current density and corrosion rate in the NaCl solution are 2.52 × 10-7 A/cm2 and 2.96 × 10-3 mmPY, respectively, which indicates superior corrosion resistance to the flame-sprayed coating and the substrate. The laser cladding of reciprocating pump plunger surfaces has a significantly improved comprehensive performance and is a promising way to increase the service life of reciprocating pumps.

Linear and Volumetric Polyethylene Wear Patterns after Primary Cruciate-Retaining Total Knee Arthroplasty Failure: An Analysis Using Optical Scanning and Computer-Aided Design Models.

(1) Background: Analyses of retrieved inserts allow for a better understanding of TKA failure mechanisms and the detection of factors that cause increased wear. The purpose of this implant retrieval study was to identify whether insert volumetric wear significantly differs among groups of common causes of total knee arthroplasty failure, whether there is a characteristic wear distribution pattern for a common cause of failure, and whether nominal insert size and component size ratio (femur-to-insert) influence linear and volumetric wear rates. (2) Methods: We digitally reconstructed 59 retrieved single-model cruciate-retaining inserts and computed their articular load-bearing surface wear utilizing an optical scanner and computer-aided design models as references. After comprehensively reviewing all cases, each was categorized into one or more of the following groups: prosthetic joint infection, osteolysis, clinical loosening of the component, joint malalignment or component malposition, instability, and other isolated causes. The associations between volumetric wear and causes of failure were estimated using a multiple linear regression model adjusted for time in situ. Insert linear penetration wear maps from the respective groups of failure were further processed and merged to create a single average binary image, highlighting a potential wear distribution pattern. The differences in wear rates according to nominal insert size (small vs. medium vs. large) and component size ratio (≤1 vs. >1) were tested using the Kruskal-Wallis test and the Mann-Whitney test, respectively. (3) Results: Patients with identified osteolysis alone and those also with clinical loosening of the component had significantly higher volumetric wear when compared to those without both causes (p = 0.016 and p = 0.009, respectively). All other causes were not significantly associated with volumetric wear. The instability group differentiated from the others with a combined peripheral antero-posterior wear distribution. Linear and volumetric wear rates showed no significant differences when compared by nominal insert size (small vs. medium vs. large, p = 0.563 and p = 0.747, respectively) or by component (femoral-to-insert) size ratio (≤1 vs. >1, p = 0.885 and p = 0.055, respectively). (4) Conclusions: The study found increased volumetric wear in cases of osteolysis alone, with greater wear when combined with clinical loosening compared to other groups. The instability group demonstrated a characteristic peripheral anterior and posterior wear pattern. Insert size and component size ratio seem not to influence wear rates.

Microstructure and properties of Al/FeCoNiCrMo coatings prepared by different plasma spraying currents on carbon fiber reinforced plastic surfaces

Al/FeCoNiCrMo high-entropy alloy (HEA) coatings were prepared on the surface of carbon fiber reinforced plastic using plasma spraying technology. The microstructure of the HEA coatings was characterized under different spraying currents, and the hardness, interfacial bonding, corrosion resistance and friction and wear properties of the coatings were tested. The results showed that with the increase of the current, the unfused particles in the coatings decreased, and the coating porosity and thickness also decreased gradually; the hardness, corrosion resistance and friction and wear resistance properties increased with the increase of the current, in which the maximum hardness was 740.3 HV0.1, and the minimum self-corrosion current was 1.21 × 10−5 A·cm−2, and the minimum volumetric wear rate was 7.66 × 10−5 mm3·N−1·m−1.

Surface melt nitriding and strengthening mechanism of plasma torched M50 bearing steel

This paper presents a new plasma torch nitriding technology for the first time to realize the surface nitriding of bearing steel for strengthening. By adjusting the plasma torch current parameters in the range of 120–160 A, M50 bearing steel was carried out at a nitriding speed of 2 s/cm2. After nitriding, the nitrogen content was increased from 0.00732 wt% in the original M50 steel up to 0.416 wt%, and the thickness of the nitrided layer was up to 2.51 mm. FeN0.076, Fe2N and Fe3N phases were formed in the steel, which was beneficial to increase the hardness and strength of bearing steel. The Vickers hardness of the original M50 bearing steel was 241 HV0.2. However, the highest surface hardness of specimen after nitriding was increased up to 778 HV0.2, which was attributed to the effect of sub-surface hardness strengthening within 2 mm from the depth of nitride surface. The average wear coefficient and the volumetric wear rate of the specimen after nitriding were decreased by about 32 % and 70 %, respectively. TEM observation showed that after nitriding, the structure of nitrided layer was martensite. The precipitates in the steel changed from large-sized, irregular and aggregated carbides (M23C6, M4C3 and M2C) to small-sized, spherical and uniformly distributed carbon‑nitrogen composite precipitates (M23(C, N)6, M7(C, N)3) in the steel sub-surface, but no obvious precipitates were formed on the surface of nitrided specimens. At depths of 1 mm and 2 mm, the size of the precipitates was reduced by about 68 % and 41 %, respectively, and the area of the precipitates was reduced from 18.4 % to 2.3 % and 3.7 %, respectively, compared to the original M50 bearing steel. It was concluded that the nitrided layer were strengthened synergistically with nitrogen solid solution, nitrogen-containing precipitates and martensite.

Improving wear and corrosion resistance of HVAF sprayed 316L stainless steel coating by adding TiB2 ceramic particles and CeO2

316L stainless steel is used in a wide variety of corrosion-prone locations. However, its low hardness and poor tribological properties limit its application under heavy wear conditions. In this study, 316L Fe-based composite coatings co-doped with TB2 hard phases and rare-earth CeO2 exhibited excellent wear and corrosion resistance. Firstly, 316L-TiB2 cermet powder and (316L-TiB2)/CeO2 composite powder with high sphericity and density were prepared by high energy ball milling (HEBM), spraying drying granulation (SD), plasma spheroidization (PS) process. Then, 316L coatings, 316L-TiB2 and (316L-TiB2)/CeO2 cermet coatings were deposited by high velocity air fuel (HVAF) spraying. Finally, the effects of TiB2 and CeO2 additions on the microstructure, wear and corrosion behavior of the coatings were investigated. The results showed that TiB2 hard particles and CeO2 were uniformly distributed in the HVAF sprayed 316L-TiB2 and (316L-TiB2)/CeO2 coatings. The wear resistance of the coating prepared by 316L Fe-based composite powder with TiB2 and CeO2 is significantly improved. The hardness of the (316L-TiB2)/CeO2 composite coating was increased from 269 Hv0.3 to 826 Hv0.3 for the pure 316L coating, while the volumetric wear rate was only 3.6 % of that of the pure 316L coating (110 × 10−5 down to 4 × 10−5 mm3/N). Electrochemical tests show that the corrosion resistance of the coating decreases with the addition of TiB2 alone, but it can be improved by doping CeO2. The 316L Fe-based coating prepared by adding TiB2 and CeO2 can significantly improve the wear resistance of the coating, while the corrosion resistance decreases only slightly.

High-performance liquid metal-based SiC/Graphene-Mo hybrid nanofluid for hydraulic transmission

A novel liquid metal-based SiC/Graphene-Mo hybrid nanofluid (LMNF) has been fabricated. The nanoparticles are uniformly dispersed, and LMNF temperature-viscosity characteristics is stabler in a wider temperature range than traditional hydraulic media. With this, the LMNF tribological performance on Al2O3 and SS316L friction pairs is studied: The LMNF has superior severe-pressure and high-temperature lubrication with the nanoparticle-enabled wear resistance. The SS316L surface forms composite nanofilm with the LMNF, which prevents adhesive wear and mitigates liquid metal corrosion. Comparatively, the nanoparticles function as "micro-bearings" on the Al2O3 surfaces to assist lubrication. These benefits are reflected in the gear pump volumetric efficiency and wear rate of our industry-level hydraulic system, approving LMNF as a potential hydraulic transmission medium in harsh conditions.

Nano-cutting mechanism of ion implantation-modified SiC: reducing subsurface damage expansion and abrasive wear

This study utilized ion implantation to modify the material properties of silicon carbide (SiC) to mitigate subsurface damage during SiC machining. The paper analyzed the mechanism of hydrogen ion implantation on the machining performance of SiC at the atomic scale. A molecular dynamics model of nanoscale cutting of an ion-implanted SiC workpiece using a non-rigid regular tetrakaidecahedral diamond abrasive grain was established. The study investigated the effects of ion implantation on crystal structure phase transformation, dislocation nucleation, and defect structure evolution. Results showed ion implantation modification decreased the extension depth of amorphous structures in the subsurface layer, thereby enhancing the surface and subsurface integrity of the SiC workpiece. Additionally, dislocation extension length and volume within the lattice structure were lower in the ion-implanted workpiece compared to non-implanted ones. Phase transformation, compressive pressure, and cutting stress of the lattice in the shear region per unit volume were lower in the ion-implanted workpiece than the non-implanted one. Taking the diamond abrasive grain as the research subject, the mechanism of grain wear under ion implantation was explored. Grain expansion, compression, and atomic volumetric strain wear rate were higher in the non-implanted workpiece versus implanted ones. Under shear extrusion of the SiC workpiece, dangling bonds of atoms in the diamond grain were unstable, resulting in graphitization of the diamond structure at elevated temperatures. This study established a solid theoretical and practical foundation for realizing non-destructive machining at the atomic scale, encompassing both theoretical principles and practical applications.

Investigating the wear resistance of AISI 410/AISI 2205 hybrid weld cladding on annealed EN 8 medium carbon steel

A new multi-layer and multi-material hybrid configuration of weld cladding an annealed EN 8 substrate has been developed and investigated. The AISI 410 martensitic stainless steel is used as the bottom and top clad layers and the AISI 2205 duplex stainless steel is used as the middle weld cladding layer which creates a composite multi-material clad structure with distinct interfacial characteristics. Examination of microstructure unveiled lamellar morphology of the top layer with martensitic-austenitic constituents with maximum hardness, whereas the intermediate layer exhibited ferritic-austenitic morphology with lower hardness. The bottom layer exhibited a tempered martensite structure with a relatively smaller grain size and exhibited intermediate hardness. The bottom-substrate interface displaying the highest interfacial hardness, followed by the middle-bottom interface and the top-middle interface in descending order. Incorporation of AISI 2205 in the intermediate contributed to an increased toughness of 30 MPa√m. During the ball-on-flat sliding wear test, the coefficient of friction displayed an intriguing pattern after a critical load threshold. Higher applied loads led to decreased absorbed energy and a reduction in wear track dimensions. Elevated heat levels promoted tribofilm formation, contributing to lower wear rates, with the optimum condition observed at 7 N, displaying the lowest volumetric loss and wear rate. The primary wear mechanism predominantly involved plastic deformation and plowing, with no apparent indications of brittle fracture.

Effect of Various Polyimide (PI) Ratios on the Wear Resistance and Mechanical Properties of PI/Polytetrafluoroethylene (PTFE) Blends

Filling polytetrafluoroethylene (PTFE) with polyimide (PI) could effectively improve the properties of PTFE-based blends. In our research described in this article, five PI/PTFE-blend specimens with various conditions were prepared by a cold-pressing, sintering method using various ratios of PI. The PI/PTFE blends were tested for mechanical and wear resistance properties. The surface morphology of the blends was observed using an ultra-field electron microscope. The maximum tensile strength was 32.18 MPa at a PI ratio of 12.5 wt.%. The variation of the PI ratio caused changes in the dispersion of the filler in the matrix, which affected the mechanical properties of the blends. When the PI content was 15 wt.%, the lowest volumetric wear degree of the PI/PTFE blends occurred, 7.8327 × 10−7 mm3/Nm. When the ratio of PI was too high, the PI filler was more likely to be detached from the PTFE matrix in a large area during the friction experiments. This would lead to the blends being more prone to generating abrasive debris during friction, and the buildup and sliding of these abrasive debris on the friction interfaces increased the volumetric wear rate and the coefficient of friction of the blends.

The Microstructure, Mechanical, and Friction-Wear Properties of Boron Carbide-Based Composites with TiB2 and SiC Formed In Situ by Reactive Spark Plasma Sintering.

The paper presents the influence of the temperature of the sintering process on the microstructure and selected properties of boron carbide/TiB2/SiC composites obtained in situ by spark plasma sintering (SPS). The homogeneous mixture of boron carbide and 5% vol. Ti5Si3 micropowders were used as the initial material. Spark plasma sintering was conducted at 1700 °C, 1800 °C, and 1900 °C for 10 min after the initial pressing at 35 MPa. The heating and cooling rate was 200 °C/min. The obtained boron carbide composites were subjected to density measurement, an analysis of the chemical and phase composition, microstructure examination, and dry friction-wear tests in ball-on-disc geometry using WC as a counterpart material. The phase compositions of the produced composites differed from the composition of the initial powder mixture. Instead of titanium silicide, two new phases appeared: TiB2 and SiC. The complete disappearance of Ti5Si3 was accompanied by a decrease in the boron carbide content of the stoichiometry formula B13C2 and an increase in the content of TiB2, while the SiC content was almost constant. The relative density of the obtained boron carbide composites, as well as their hardness and resistance to wear, increased with the sintering temperature and TiB2 content. Unfortunately, the reactions occurring during sintering did not allow us to obtain composites with high density and hardness. The relative density was 76-85.2% of the theoretical one, while the Vickers hardness was in the range of 4-12 GPa. The mechanism wear of boron carbide composites tested in friction contact with WC was abrasive. The volumetric wear rate (Wv) of composites decreased with increasing sintering temperature and TiB2 content. The average value of coefficient of friction (CoF) was in the range of 0.54-0.61, i.e., it did not differ significantly from the value for B4C sinters.

Study of frictional wear and desorption of nanoparticle‐rubber blend modified UHMWPE composites

AbstractTo address the issues of abrasive wear, impact wear, and soil adhesion that can lead to wear failure and excessive operational resistance in agricultural soil touching parts during farming. This study focuses on UHMWPE composites, modified by filling Nano‐SiC as a hard phase filler and XNBR as an elastic filler. These fillers were dispersed into the UHMWPE matrix through melt blending technology to create a high‐performance composite material for the surface protective material of soil touching parts. The study discovered that by adding hard and elastic fillers to the UHMWPE matrix, the density, hardness, flexural modulus and thermal stability of the materials were all increased. Specifically, the density increased by 5.67% and the flexural modulus increased by 107%. In the block on ring wear test the volumetric wear rate decreased by 98%, while in the mortar wear test the mass wear rate decreased by 64.64%. Additionally, the contact angle on the surface of the specimen after mortar erosion and wear increased to 102.76°, 18% higher than that of pure UHMWPE. These results demonstrate that the modified fillers can improve the abrasion and plastic deformation resistance and hydrophobic desorption of UHMWPE. UHMWPE composite material, serving as the surface protection for soil touching parts, resolves the issues of abrasion of soil abrasive particles and excessive soil adhesion resistance on these parts. This significantly prolongs the service life of soil touching parts of agricultural machinery and improves the operational efficiency and economy.Highlights Research on nanoparticles and elastomer‐modified composite materials. Research has shown the enhancement of UHMWPE composite materials by Nano‐SiC. XNBR improves the plastic deformation resistance of UHMWPE composites. Effects of Nano‐SiC and XNBR on the desorption behavior of composite materials. UHMWPE composites reduce soil contact wear and soil adhesion.

Fabrication of nano SiC and BF-bonded magnesium alloy (AZ80) hybrid nanocomposite via liquid state stir casting process: characteristics study

ABSTRACT Concerning various materials in the engineering domain, magnesium alloy-based composites are found to have specific properties. They are prepared with ceramic particles via a liquid stirring process, and oxidation results in porousness. Due to this, this research aims to develop cast magnesium alloy (AZ80), nanocomposite and hybrid nanocomposites via a liquid state stir casting process with an argon atmosphere. It contains 0, 2, 4 and 6 wt% of silicon carbide nanoparticles (SiC) and 6 wt% SiC with 3, 6 and 9 wt% of basalt fibre. The developed cast AZ80 alloy, nano and hybrid nanocomposites are subjected to physical, mechanical and wear behaviour studies, and their results are compared. The composite contained 6 wt% SiC, and 9 wt% BF showed low porosity (1.03%), superior tensile strength (359 ± 7 MPa), elastic modulus (23044.58 ± 230 MPa), strain (2.114 ± 0.01 mm), hardness (121 ± 1.02 HV), coefficient of friction (0.421 ± 0.02) and low impact strength (18.25 ± 0.34 J/mm2) and volumetric wear rate (5.36 ± 0.4 mm3/m) compared to others.

Highly Cross-Linked Polyethylene in Patients 50 Years of Age and Younger: A 20-year Follow-Up Analysis

BackgroundHighly cross-linked polyethylene (HXLPE) has been an excellent bearing for total hip arthroplasty (THA) due to improved wear characteristics compared to conventional materials. Patients 50 years of age or younger are at high risk for wear-related complications of their THA, and few studies have followed these patients who have HXPLE into the third decade. MethodsIn a retrospective review of 88 consecutive THAs performed in 77 patients aged 50 years and younger (mean 41; range, 20 to 50), in which HXLPE was utilized, they were evaluated for their clinical and radiographic results at an average of 20-year follow-up (range, 18 to 24). The current study reports on longer-term follow-up from our previously published series at shorter follow-up times. Patients were categorized by femoral head material: cobalt chrome (n = 14), ceramic (n = 30), and oxidized zirconium (n = 22) and by femoral head size: 26 mm (n = 12), 28 mm (n = 46), and 32 mm (n = 8). Harris Hip Scores were collected preoperatively and at the most recent follow-up. Radiographs were evaluated for linear and volumetric wear, radiolucent lines, and osteolysis. ResultsMean Harris Hip Scores improved from 47.1 (standard deviation [SD] 8.8) preoperatively to 92.0 (SD 7.7) (P < .0001) at 20-year follow-up. There was one hip that was revised for recurrent instability, and no hip demonstrated radiographic evidence of loosening or osteolysis. The mean polyethylene linear wear rate was 0.017 (SD 0.012) mm/y, and the mean polyethylene volumetric wear rate was 3.15 (SD 2.8) mm3/year, with no significant differences based on articulation type or head size. ConclusionsTotal hip arthroplasty with HXLPE in patients ≤ 50 years of age continues to demonstrate excellent long-term clinical and radiographic outcomes with low wear characteristics at 20-year follow-up, regardless of femoral head material or size.

Effect of Heat Treatment and Reinforcement Content on the Wear Behavior of Al–4Cu/Al2O3–CNT Nanocomposites

In the study, the effects of hybrid reinforcement (nano-alumina and MWCNT) and heat treatment on the wear behavior of the Al–4Cu nanocomposites were investigated under dry sliding condition against W–6Co ball by means of a ball-on-disk type tribometer. The load and the sliding speed were kept constant and selected to be 10 N and 0.1 m s−1, respectively, in the course of the wear tests. Meanwhile, the wear tests were completed after a total sliding distance of 1500 m was reached for each case. During these tests, the wear loss of the nanocomposites was measured at every 250 m. The worn surfaces of the nanocomposites were examined with the help of stereo and scanning electron microscopes. The volumetric wear rates, wear coefficients and wear mechanisms were identified for the nanocomposites to clarify the influence of reinforcement content and heat treatment on their wear resistance. The volume loss at the wear distance of 1500 m was obtained as 24.9 and 8.2 mm3 for the annealed and aged Al–4Cu alloy, respectively. On the other hand, it decreased to 4.6 and 3.2 mm3 in the case of the nanocomposites with 15% hybrid reinforcement in the annealed and aged conditions, successively. Moreover, increasing the hybrid reinforcement amount decreased the wear loss of the aged nanocomposites substantially in such a way that it resulted in the mild wear.

Investigation of stair ascending and descending activities on the lifespan of hip implants

Total hip arthroplasty (THA) surgeries among young patients are on the increase, so it is crucial to predict the lifespan of hip implants correctly and produce solutions to improve longevity. Current implants are designed and tested against walking conditions to predict the wear rates. However, it would be reasonable to include the additional effects of other daily life activities on wear rates to predict convergent results to clinical outputs. In this study, 14 participants are recruited to perform stair ascending (AS), descending (DS), and walking activities to obtain kinematic and kinetic data for each cycle using marker based Qualisys motion capture (MOCAP) system. AnyBody Modeling System using the Calibrated Anatomical System Technique (CAST) full body marker set are performed Multibody simulations. The 3D generic musculoskeletal model used in this study is a marker-based full-body motion capture model (AMMR,2.3.1 MoCapModel) consisting of the upper extremity and the Twente Lower Extremity Model (TLEM2). The dynamic wear prediction model detailing the intermittent and overall wear rates for CoCr-on-XLPE bearing couple is developed to investigate the wear mechanism under 3D loading for AS, DS, and walking activities over 5 million cycles (Mc) by using finite element modelling technique. The volumetric wear rates of XLPE liner under AS, DS, and walking activities over 5-Mc are predicted as 27.43, 23.22, and 18.84 mm3/Mc respectively. Additionally, the wear rate was predicted by combining stair activities and gait cycles based on the walk-to-stair ratio. By adding the effect of stair activities, the volumetric wear rate of XLPE is predicted as 22.02 mm3/Mc which is equivalent to 19.41% of walking. In conclusion, in this study, the effect of including other daily life activities is demonstrated and evidence is provided by matching them to the clinical data as opposed to simulator test results of implants under ISO 14242 boundary conditions.

Long-term polyethylene wear rates and clinical outcomes of oxidized zirconium femoral heads on highly cross-linked polyethylene in total hip arthroplasty.

Oxidized zirconium (OxZi) and highly cross-linked polyethylene (HXLPE) were developed to minimize wear and risk of osteolysis in total hip arthroplasty (THA). However, retrieval studies have shown that scratched femoral heads may lead to runaway wear, and few reports of long-term results have been published. The purpose of this investigation is to report minimum ten-year wear rates and clinical outcomes of THA with OxZi femoral heads on HXLPE, and to compare them with a retrospective control group of cobalt chrome (CoCr) or ceramic heads on HXLPE. From 2003 to 2006, 108 THAs were performed on 96 patients using an OxZi head with a HXLPE liner with minimum ten-year follow-up. Harris Hip Scores (HHS) were collected preoperatively and at the most recent follow-up (mean 13.3 years). Linear and volumetric liner wear was measured on radiographs of 85 hips with a minimum ten-year follow-up (mean 14.5 years). This was compared to a retrospective control group of 45 THAs using ceramic or CoCr heads from October 1999 to February 2005, with a minimum of ten years' follow-up. Average HHS improved from 50.8 to 91.9 and 51.0 to 89.8 in the OxZi group and control group, respectively (p = 0.644), with no osteolysis in either group. Linear and volumetric wear rates in the OxZi group averaged 0.03 mm/year and 3.46 mm3/year, respectively. There was no statistically significant difference in HHS scores, nor in linear or volumetric wear rate between the groups, and no revision for any indication. The radiological and clinical outcomes, and survivorship of THA with OxZi femoral heads and HXLPE liners, were excellent, and comparable to CoCr or ceramic heads at minimum ten-year follow-up. Wear rates are below what would be expected for development of osteolysis. OxZi-HXLPE is a durable bearing couple with excellent long-term outcomes.

Investigating the load and temperature-dependent dry sliding wear performance of Al–12Ce alloys with Si and Mg additions

The current study investigates the effect of load and temperature on the wear characteristics of gravity-cast Al–12Ce, Al–12Ce-X alloys (where X = 4Si, 0.4Mg, and 4Si+0.4Mg), and commercial A356 alloys at 5, 10, and 20 N; and at 25, 100, and 200 °C newly fabricated for diesel engine applications. The addition of 4Si and 0.4Mg increased the Al–12Ce alloy's hardness and decreased the volumetric wear rate of the alloy at all loads and temperatures. However, the Al–12Ce–4Si-0.4Mg alloy had the lowest wear rates at all loads and temperatures. The friction coefficient and surface roughness diminish with 4Si and 0.4Mg addition to Al–12Ce alloys, which was the lowest in the Al–12Ce–4Si-0.4Mg alloy. Under the loading and temperature conditions, friction coefficient and surface roughness are the lowest in the Al–12Ce–4Si-0.4Mg alloy. All of the alloys are subject to abrasion, adhesion, oxidation, and delamination wear mechanisms under experimental conditions. However, the wear mechanisms are the most severe and mildest in the Al–12Ce and Al–12Ce–4Si-0.4Mg alloys, respectively. The superior wear response of the alloy Al–12Ce–4Si-0.4Mg is attributed to its smaller grain size, less amount of Al11Ce3 phase, and higher amount of thermally stable CeAlSi2 phases.

A Comparison Study on the Microstructure, Mechanical Features, and Tribological Characteristics of TiN Coatings on Ti6Al4V Using Different Deposition Techniques

Titanium alloys are considered lightweight alloys and are widely applied across various industries. However, their low hardness, poor wear resistance, and limited oxidation resistance restrict their prospects for wider application. In this paper, nitride coatings were prepared using three preparation processes, namely laser surface nitriding (LSN), physical vapor deposition (PVD), and plasma ion implantation (PII). Their microstructure, microhardness, tribological behavior, and high-temperature oxidation characteristics were compared. The experimental results revealed that nitrided coatings were successfully prepared using the three methods. However, a comparison of these data shows that the LSN coating exhibited superior comprehensive performance. It achieved the maximum thickness within the shortest preparation time: the thickness was about 280 μm and the deposition rate of the LSN method was 2250 and 90,000 times higher than those of the PVD and PII methods. Nitrides have high hardness, but the carrying capacity could be attributed to the thickness of the coatings: the PVD coating could withstand a force of 500 g, while the PII coating only withstood a force of less than 25 g. In addition, as hardness is the most important factor for excellent wear resistance, the average volumetric wear rate of the LSN and PVD coatings was about 9 × 10−6 mm3/m·N, and their relative wear resistance was 49.2 times that of Ti6Al4V. Meanwhile, the excellent bond between the LSN coating and the substrate was evidenced by a high-temperature oxidation test during a rapid heating–cooling cycle.

Fretting wear assessment in PHWR pressure tubes using transient dynamic FEA and Archard’s wear model

In Pressurized Heavy Water Reactors (PHWRs), the fuel bundles are placed in a pressure tube (PT). These bundles rest on inside of pressure tubes through the bearing pads. The pressure tubes are part of the primary pressure boundary of the reactor, and are crucial from functionality and safety point of view. Any phenomena/ factors that may cause structural degradation of PT and may affect its structural integrity, requires thorough investigation. The fretting of pressure tube at bearing pad locations is one such phenomenon, wherein the local material removal due to fretting may lead to stress concentration and associated structural degradations. Therefore, a detailed assessment of the PT fretting damage incurred during its intended life is required. Present paper covers the premise and methodology based on Archard’s wear model for evaluation of the volumetric wear rate of pressure tube. A case study has been done to evaluate the fretting wear in pressure tubes of a large Indian PHWR. 3D transient computational fluid dynamic analysis and finite element analysis with contact modelled between the fuel bundle bearing pads and pressure tube are carried out to evaluate the contact force and sliding distance time histories. Based on the analyses results, the work rate and average saturated fret depth are evaluated. The assessment revealed insignificant concern owing to the fretting of pressure tube for the considered cases.

The Effect of Micron-Sized TiB2 Particles on the Properties of Al6061 Strengthened with 4% TiB2 Nano-TiB2.

Dual-scale (nano and micron) particle-reinforced TiB2/6061Al matrix composites with different contents of TiB2 were prepared using powder metallurgy, and then analyzed via microstructure observation and tests of microhardness, tensile properties, and friction and wear properties. The 6061Al powders' particles changed from spherical to flaky after two rounds of high-energy ball milling, and the TiB2 enhancer was embedded in or wrapped by the matrix particles after high-energy ball milling. Metallurgical bonding between TiB2 particles and the matrix was achieved, and Al3Ti was synthesized in situ during sintering. The hot-pressing process eliminated the internal defects of the composites, and the TiB2 particles were diffusely distributed in the matrix. The best comprehensive mechanical properties (hardness and tensile strength) were achieved when the mass fraction of TiB2 was 5% (1% micron + 4% nano); the hardness and tensile strength of the composites reached 131 HV and 221 MPa-79.5% and 93.9% higher than those of the pure matrix, respectively. The composites' average coefficient of friction and volumetric wear rate were reduced. Composites with a TiB2 mass fraction of 7% (3% micron + 4% nano) had the highest average coefficients of friction and the lowest volumetric wear rate of 0.402 and 0.216 mm3∙N-1∙m-1, respectively. It was observed that adhesion influences the friction mechanism, which transitions from adhesive wear with slight oxidative wear to abrasive wear.