Change In Wear Rate Research Articles

Study of the Wear Resistance Plasma Nitrided GGG60 by Optimization of Surface Treatment Conditions Using Response Surface Methodology

AbstractIn this study, the wear performance of spheroidal graphite cast iron subjected to plasma nitriding at different temperatures and treatment durations was investigated. The plasma nitriding parameters were optimized by response surface methodology (RSM) due to the output performance. Plasma nitriding was applied at three different temperatures (400, 450, 500 °C) and three different heat treatment durations (0.5, 2, 4 h). Wear tests were performed by ball-on-disk method for 60 minutes and for three different wear loads (10, 20, 30 N). The specimens were investigated for hardness, microstructure and wear performance. The RSM model was then created by using the wear resistance features. Plasma nitriding showed better wear performance than the untreated specimen for all treatment conditions. Hardness, nitrided layer thickness and wear performance remarkably improved with increasing temperature and process duration. The parameter that affects volume loss the most is wear load with 70.66% according to RSM modeling results. The most effective parameter in the wear rate change was found to be treatment duration at 42.85%. The model was able to predict the results with an error of 2.11% for volume loss and 9.14% for wear rate. The prediction results are very close to the experimental results. This clearly shows that the model can be used to determine the plasma nitriding parameters.

Interrelation of wear rates of accelerator gear teeth

This paper considers the interrelation of wear rate of the accelerating gear pinion head and teeth foot, which depends on the number of pinion teeth involved in the meshing and gear ratio. Patterns of wear rate changes occurring between the head and the gear teeth leg, hardened by volume hardening, hardening by high-frequency current, cementation and nitriding, in the presence and absence of abrasive particles in the working environment, when the gear ratio has an increasing (accelerating) tendency, have been established.

Entropy-based fluid–solid–thermal coupled wear prediction of journal bearing during repeated starting and stopping

The novelty of the present study is to construct an Entropy-based wear and fluid-solid-thermal (FST) coupled model for journal bearings, which reveals the transient interaction behavior between wear evolution and FST evolution during repeated starting and stopping. The wear rate is measured experimentally and the contact temperature, friction coefficient and normal contact force are obtained from the validated FST model. Wear tests for the lubricated journal bearing at three constant speeds are used to validate the predicted wear rate. Numerical calculations give the time-varying wear and FST evolution of journal bearings during repeated starting and stopping at the same or different start-stop time, including wear rate, wear depth, temperature, fluid pressure and contact pressure. The effects of the bearing thickness, maximum speed, radial clearance and load on the wear and FST performances are evaluated. The simulation results reveal that the rate of change of wear rate in the start-stop cycle first increases rapidly and then decreases slowly as the number of start-stop cycles increases. The distributions of the contact pressure and the fluid pressure become wider along the circumferential direction with the increase in the number of start-stop cycles while the maximum values become smaller. The maximum wear depth increases with increasing start-stop time for an identical number of start-stop cycles, and the shorter the start-stop time is, the higher the maximum temperature tends to be. Furthermore, the effect on the maximum wear depth and maximum temperature of journal bearings will become significant when the maximum speed and bearing thickness are relatively small or the radial clearance and load are relatively large.

Wear Behaviour of a Cu-Ni-Sn Hybrid Composite Reinforced with B4C prepared by Powder Metallurgy Technique

Cu matrix composites benefit from the high electrical and thermal conductivities of Cu and the mechanical wear/erosion resistance of hard reinforcement. In this study, an attempt has been made to determine the effect of the addition of reinforcement B4C in Cu-Ni-Sn. The B4C is reinforced to form a hybrid Cu matrix composite with powder metallurgy technique. The hybrid composites are obtained by milling, blending, and compacting the powders to obtain a fine grain-sized particle without aggregation. The grain size and particle nature were characterized using scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques, respectively. The microstructure, density, hardness, and wear rate of the composites were studied. The pin-on-disc method is equipped to study the wear behaviour and coefficient of friction. The sintered density of the prepared Cu-15%Ni is 98.25 %, Cu-8%Sn is 98.20 %, Cu-15%Ni-8%Sn is 98.10 % and Cu-15%Ni-8%Sn-2%B4C is 95.26 % and lower specific wear rate has been recorded for Cu-15Ni-8Sn-2B4C 121×10-6 mm3/(Nm) and the addition of reinforcement B4C in Cu-Ni-Sn displays remarkable changes in wear rate and friction coefficient.

High crystallinity makes excellent wear resistance in crosslinked UHMWPE

Nowadays, irradiation crosslinking is still a primary method to improve the wear resistance of ultrahigh molecular weight polyethylene (UHMWPE). As a semi-crystalline polymer, crystalline structure of UHMWPE will also significantly affect the abrasion performance. Due to the difficulty in obtaining a wide range of crystallinity (Xc), there is less knowledge on the synergistic enhancement of crosslinking and crystallization to wear resistance. Herein, a combination of using low entanglement nascent powder and adjusting thermal history of sinter molding causes the Xc of UHMWPE varied in a range of 44%∼56%, and then γ-ray irradiation is utilized to form crosslinking between molecular chains. The significances of crystallization on the wear resistance of crosslinked UHMWPE are manifested as follows. (1) When Xc maintains almost constant, the wear rate per 105 cycles doesn't decrease continuously with the increase of molecular weight (MW), indicating the effect of MW on abrasion performance is limited. (2) For the crosslinked samples with same MW but different Xcs, the wear rate reduces monotonously as increasing Xc. It drops for −41% at the highest Xc, which means the wear resistance is susceptible to the amount of crystalline phase. (3) By exposing to γ-irradiation, the wear rate of the low-Xc sample (44%) reduces for −12%, while it reaches −21% for the counterpart with Xc∼56%. Obviously, crosslinking at high Xc is more effective in tailoring wear resistance. In addition, the fact that among the samples with similar Xc the wear rate changes faintly regardless of distinct variations in crystalline microstructure, suggests Xc plays a vital role on anti-abrasive behavior rather than other structural factors. According to these results, we propose an effective strategy to improve the wear resistance of crosslinked UHMWPE by utilizing high crystallinity, which has potential for developing high-performance artificial joint prosthesis materials.

Dry Sliding Wear Behavior and Mild–Severe Wear Transition of the AA2195-T6 Alloy under Different Loads

The mild–severe wear transition of aluminum alloys is considered evidence that the wear changes from a stable state to an unstable state, which is of great importance in engineering applications. The purpose of this study is to evaluate the mild–severe wear transition of the 2195 Al–Li alloy for different loads and to elucidate the causes behind it. To this end, dry sliding tribometric tests were carried out by varying the normal load from 2 to 40 N at room temperature. The results show that the change in wear rate can be divided into three distinct stages, including weak growth at low load (2–4 N), rapidly increased growth at medium load (8–16 N), and gradually increased growth at high load (32–40 N). The transition from mild to severe wear is observed at loads ranging from 4 to 8 N. Characterization of the worn surface of the Al–Li alloy via scanning electron microscopy shows that abrasion and oxidation are the dominant wear phenomena in the mild wear regime. On the other hand, delamination, adhesion, and severe plastic deformation become dominant in the severe wear regime. The reason for the occurrence of the transition is the tribo-induced plastic deformation of the substrate.

Effect of cryogenic treatment holding time on mechanical and microstructural properties of Sverker 21 steel

Abstract This study investigated the effects of shallow and deep cryogenic treatment on the microstructural and mechanical properties of Sverker 21 tool steel. After conventional heat treatment, shallow cryogenic treatment at −80 °C for 2, 12, and 24 h and deep cryogenic treatment at −180 °C for 2, 18, and 36 h were applied on the steel samples. After that, the samples were tempered at 200 °C for 2 h. As a result of these treatments, the steel samples’ hardness, toughness, and wear rate changes were determined, and their microstructural properties were investigated. As a result of the study, it was observed that the cryogenic treatment had positive effects on the mechanical and microstructural properties of Sverker 21 steel. Mechanical properties also improved with increasing holding time for both cryogenic treatment types. It has been found that the deep cryogenic treatment provides better mechanical properties compared to the shallow cryogenic treatment. The maximum hardness and wear resistance were obtained in the deep cryogenically treated sample for 36 h. Compared to the CHT sample, the hardness and impact energy of the DCT(36) sample increased by approximately 11.75% and 17.36%. An improvement of approximately 64% was observed in the wear rate.

Towards modeling of Grid to Rod and the effect of its nonlinear dynamic behaviors on grid-to-rod fretting wear

The grid-to-rod fretting (GTRF) wear is always a significant cause of fuel failure. The dynamic behavior of fuel rods during actual operation is complex, so understanding the dynamic mechanism of the grid-to-rod system is essential for wear analysis. This paper developed a mathematical model of a fuel rod subjected to sinusoidal excitation loads with gap constraint. The partial differential equation was discretized by the Galerkin method and solved by Runge–Kutta scheme. The vibration response and the wear rate of cladding in the possible gap range under numerous hypothetical cases were studied. The result shows that the nonlinear vibration motion significantly impacts GTRF wear. The wear rate changes are linear under harmonic and low-period vibration, and most high-period movement significantly affects the wear rate. Some exciting and fresh results allow us to understand better GTRF wear propagation and optimize fuel assembly design.

ВЗАИМОСВЯЗИ СКОРОСТЕЙ ИЗНАШИВАНИЯ ЗУБЬЕВ МЕЖДУ ВЕДУЩЕЙ И ВЕДОМОЙ ШЕСТЕРЕН

The article reviews interrelation of wear speeds of the accelerating and decelerating gears’ teeth heads and legs, at an account of the ratio of a relative wear of the teeth depending on the number of gear teeth participating in meshing and gear ratio. Regularities of wear rate changes between gear teeth head and foot, hardened by bulk hardening, hardening by high frequency current, cementation and nitriding, in the presence and absence of abrasive particles in the working environment, when the gear ratio has increasing (accelerating) or decreasing (reducing) tendency, have been established. Hardness laws of the friction surfaces of the driven gear wheel teeth friction surfaces of the accelerating and reducing gears have been determined.

Comparative study on microstructure, mechanical, and tribological property of gamma‐irradiated polytetrafluoroethylene, polyetheretherketone, and polyimide polymers

In this paper, three commercial polymers (polytetrafluoroethylene [PTFE], polyetheretherketone [PEEK], and polyimide [PI]) were irradiated by gamma rays in the ambient air. The changes in microstructure, mechanical, and tribological properties of these three polymers after irradiation were investigated comparatively. The results display that both the surface and internal structures of PTFE are degraded due to the irradiation chemical reaction, and the molecular chain scission at the surface is more severe than that at its internal as a result of the involvement of oxygen. The oxidative degradation also plays a dominant role in the PEEK surface, but the molecular chain crosslink is dominant in the PEEK internal. The top layer of PI also shows the characteristics of oxidative irradiation degradation, but its internal exhibits excellent irradiation resistance and no structure change occurs even at irradiation doses up to 20 MGy. The microhardness and scratch resistance of irradiated surfaces for all three polymers decrease but only the scratching damage mode of PTFE changes after irradiation. Friction experiments show that the friction coefficients of PTFE increase but that of PEEK decrease after irradiation. The wear rates on the irradiated surfaces of all three polymers increase compared with the unirradiated samples. Moreover, there is a depth gradient effect on the wear properties of both irradiated PTFE and PEEK polymers. The changes in wear rates of irradiated surfaces are consistent with the structural variations of all three polymers.

Ultralow Wear Poly(tetrafluoroethylene): A Virtuous Cycle of Wear Reduction and Tribochemical Accumulation

Certain nanofillers have demonstrated a remarkable wear-reducing effect on poly(tetrafluoroethylene) (PTFE), a common solid lubricant polymer. In these unusual cases, ultralow wear rates are accompanied by tribochemical changes that stabilize surfaces by anchoring polymer chains to dispersed nanoparticles and the countersurface. The leading hypothesis is that nanofillers catalyze these favorable tribochemical processes, which ultimately causes ultralow wear rates. However, the extent to which reduced wear rates contribute to the accumulation of favorable tribochemistry remains untested. In this study, we used indexed reciprocation to eliminate the protective effects of transfer films, control the wear rate, and independently determine how wear rate and filler morphology affect these tribochemical outcomes. Despite large and important differences between the fillers tested (from nanoparticles to microparticles), we observed surprisingly little effect from the filler on tribochemistry when controlling the wear rate. By contrast, tribochemistry was extremely sensitive to the changes in wear rate regardless of the filler. Standard reciprocation, which promoted the development of protective transfer films, caused low wear rates and significant tribochemical accumulation for all three filler conditions. By removing the protective effects of transfer films, indexed reciprocation increased wear rates by 100-fold while effectively eliminating tribochemical accumulation and tribofilm formation on the polymer pin. In contrast to prior studies, which demonstrate that tribochemical accumulation enables ultralow wear rates, this study demonstrates that a pre-existing condition of low wear is needed to enable tribochemical accumulation. The results from this study and prior studies of PTFE wear appear to be most consistent with the hypothesis that protective transfer films initiate low wear rates, that low wear rates enable tribochemical accumulation, and that tribochemical accumulation reduces wear rates in a virtuous cycle.

INVESTIGATION ON DRY SLIDING WEAR BEHAVIOR OF TITANIUM DIOXIDE-REINFORCED MAGNESIUM MATRIX COMPOSITE

In this work, the dry sliding wear behaviors of pure monolithic magnesium and magnesium–titanium dioxide (Mg–TiO2) composites were studied using pin-on-disc tribometer against an oil-hardened nonshrinking die steel (OHNS) counter-disc with a normal load of 0.5–2[Formula: see text]kg and a sliding velocity of 1.5–2.5[Formula: see text][Formula: see text] with the sliding distance and wear track diameter of 1500[Formula: see text]m and 90[Formula: see text]mm, respectively. The pin samples were characterized for their microstructural, nanomechanical and tribological properties such as wear rate, coefficient of friction and wear fractographs. Scanning electron microscopy (SEM) was used to analyze the worn-out surfaces of each pin sample in order to identify the different types of wear and wear mechanisms and the chemical constituents of each element were quantified by energy-dispersive spectroscopy. The influence of TiO2 reinforcements on the nanomechanical behavior was studied by nanoindentation technique. As compared with pure Mg, the nanoindentation strengths of Mg–1.5TiO2, Mg–2.5TiO2 and Mg–5TiO2 composites were found to increase by 11.9%, 22.2% and 35.8%, respectively, which was due to the addition of TiO2 particles and also due to the good bonding at the interface of TiO2 and magnesium particles. From the wear test results, a significant change in wear rate was observed with the change in normal load than that of sliding speed, whereas a significant change in coefficient of friction was noticed with the changes in both normal load and sliding velocity. The dominant wear mechanisms involved under the testing conditions were identified through plotting the contour maps and SEM fractographs. Also, from the fractographs it was noticed that delamination and plowing effect have been the significant wear mechanisms observed during low wear rate of samples, whereas melting, delamination and oxidation wear have been observed during high wear rate of pure Mg and its composites.

A Novel Image Processing Technique for Analyzing Wear Worn Surface Roughness and Corrosion Behavior of Sintered Mg/B4C Composites

The pure Mg and Mg-B4C composites are produced with dissimilar weight percentages (Mg-5% B4C, Mg-10% B4C, and Mg-15% B4C) using powder metallurgy methods. To find the consequences of B4C in pure Mg, the Vickers micro-hardness, dry sliding wear, 3D roughness profile, and immersion corrosion tests were conducted. To quantify the texture of the composite surface, the local binary co-occurrence pattern quantification technique was used in this analysis and the related texture features were extracted to evaluate the composite surfaces. The wear analysis of Mg-B4C composites was examined in disparate loads of 30, 60, and 90 N with a constant sliding velocity of 2 m/s and in 2000 m constant sliding distance. The changes in wear rate, wear depth, and friction coefficient were compiled and analyzed. It was identified that the wear rate increased with the increment of load. To comprehend the wear mechanism of pure Mg and all Mg-B4C (5–15%) composites, its worn surfaces were subjected to SEM and EDS mapping analyses. The surface roughness of the worn surfaces was explored using a 3D roughness profile test and atomic force microscopy analysis. The obtained results exhibited that the hardness of Mg-B4C composites increased with increasing of B4C weight percentages. The rate of corrosion was discovered using the weight loss method. The corrosion rate decreased to a great extent with the increasing weight percentage of B4C in the Mg matrix.

Effects of Al substitution with Si and Sn on tribological performance of Ti3AlC2

Since their discovery, the MAX phases have elicited engineering interest as potential choices for wear resistant parts. One such compound is Ti3AlC2 with nano-layered structure, low density (4.25 g/cm3), good oxidation resistant and self-lubrication properties. The purpose of this investigation was to evaluate the dominant effect of the A-site solid solution elements addition on dry sliding characteristics of Ti3AlC2 against 0.45% C steel (S45C) disk, a material which is widely used in wear-critical applications such as impeller, gear and axles. Dry sliding tribological behaviors of hot-pressed Ti3Al0.94C2, Ti3Al0.78Sn0.22C2 and Ti3Al0.67Si0.28C2 solid solutions were conducted using a block-on-disk type tester at surface sliding speed range from 10 to 30 m/s and in the normal load range from 20 to 80 N. The results show that friction coefficient of Ti3Al0.94C2 is higher than that of Ti3Al0.78Sn0.22C2, but lower than that of Ti3Al0.67Si0.28C2. However, the change in wear rate as a function of normal load for different sliding speed shows almost reversed trend. Difference in the phase composition of friction films were found to be responsible for observed change in tribological behaved after partial substitution of Al in Ti3AlC2 with Sn and Si. This study shows that friction coefficient of Ti3AlC2 can be adjusted from 0.2 to 0.38 by partially substituting Al with Si and/or Sn.

Effects of 3D printed surface texture on erosive wear

Abstract Additive Manufacturing (AM), which more commonly known as 3D printing, is an extremely popular, fast and flexible manufacturing method. Rectangular prismatic textures are created on a surface via 3D printing technique. It is observed that the surface texture obtained by AM reduces particle erosion by half under the same erosion direction, and the angle of blasting direction on the prepared surface texture has a major effect, where there is an evident change in wear rate when the surface texture is smaller than the particle size. Also, it is seen that small changes in the dimension of the texture has no remarkable effect on particle erosion.

Investigation of wear resistance of drill bits with WC, Diamond-DLC, and TiAlSi coatings with respect to mechanical properties of rock

Drilling is an important engineering operation with extensive application in many fields of industry including mining engineering, oil and gas exploration and exploitation, civil engineering, groundwater management, etc. Drill bits must be able to endure enormous stresses that gradually wear them down during the drilling operation. In rock drilling, wear resistance is a key determinant of the drill bit lifetime and hence the drilling cost, thus basically affecting the choice of drilling method for any given rock type. With the advent of new wear-resistant materials, they can be used to improve the resistance of drill bits against wear and erosion. This study investigated the wear resistance of drill bits with tungsten carbide (WC) coating, DLC-Diamond coating, and titanium-silica‑aluminum (TiAlSi) coating when drilling in three types of hard rock, namely Khoshtinat Granite (A1), White Natanz Granite (A2) and Nehbandan Granite (A3). The drilling tests were performed on cuboid specimens using a drilling machine at rotation speeds of 850, 900 and 950 rpm and penetration rates of 12, 18 and 24 mm/min. The results showed that for any fixed drilling conditions, the wear rates of the TiAlSi drill bit in A1, A2, and A3 were respectively 48%, 52%, and 60% lower than those of the WC drill bit. In the same rocks, the Diamond-DLC drill bit also showed 42%, 44.25%, and 55% lower wear rates than the WC drill bit. in addition to the observed changes in wear rate of the drill bits, the surface roughness created by these drills represents the optimum performance of the TiAlSi drill bit. It was observed that, as the mechanical properties of the rock (uniaxial compressive strength, Mohs hardness, Schimazek's abrasivity index and Young's Modulus) increased, the tested drill bits showed wider differences in terms of wear resistance. As the TiAlSi drill bit had the lowest wear rate (27%) and after that, the Diamond-DLC drill bit showed a better wear (30%) performance than the WC drill bit (60%).

Підвищення зносостійкості трибоспряжень зразків "сталь 45-чавун СЧ20" з геомодифікатором КГМТ-1

Increase of wear resistance of different types of tribomating which are functioning in fluid lubrication is possible due to: choosing more expensive and high quality material of samples that is not always sensible; applying some wear resistant coatings on them; selection and formation of complex composition of oil additives. Due to nanomaterials development there is a possibility of efficient use of functional additives such as geo modifiers in tribology. Due to geo modifier-based oil composites use it’s not necessary to make any structural changes of machines mated parts though their wear resistance is increased. It requires the conducting of some experimental tribological research. It was found that oil media modified by a geo modifier increase the wear resistance of working surfaces of different types of tribomating. The use of geo modifier КGМF-1 (Katerynivka friction geo modifier-1) has been suggested. Samples division into 4 types of mating according to the following characteristic features: mobility, material hardness and friction area has been suggested for more accurate picture of wear resistance changes of samples tribomating which are functioning in base and modified oil. Lower friction torque of different samples couplings in modified oil by geo modifier КGМF-1 in comparison with base oil M-10G2K was recorded while using Friction machine 2070 SMT-1 with add-on module "ring-ring". The samples wear rate in modified oil by geo modifier КGМF-1 in comparison with base oil M-10G2K was studied by method of acoustic signal amplitude measurements directly from the friction zone by a commercially produced instrument of Brüel & Kjear company. Moreover, it was recorded that the maximum wear rate of samples in their functioning in modified oil M-10G2K + КGМF-1 was 2...3 times lower, and friction torque change law is similar to the wear rate change depending on the time of testing

Wear Evolution of the Glass Fiber-Reinforced PTFE under Dry Sliding and Elevated Temperature.

The wear evolution of the glass fiber reinforced Polytetrafluoroethylene (PTFE) sliding against duplex steel at elevated temperature was investigated using the interrupted wear tests coupling with the worn surface observations. The morphological changes of the PTFE composite during the sliding were related to the variation of the tribological properties to analyze the underlying wear mechanisms. Results show that the coefficient of friction and wear rate change with the increase of temperature. During the sliding, three regions can be identified regardless of the temperature. The high temperature is beneficial to the formation of tribo-film. The sequence of wear evolution is PTFE removal, load transfer to glass fiber, and minor formation of tribo-film for the low temperature condition. For high temperatures, the wear behaviors are more complicated. The different phenomena include the third body abrasion, flake delamination of PTFE matrix, scratching and reformation of transfer film on the counterface, and the filling of the large scale PTFE groove. These behaviors may dominate the different stages in the stable region, but occur simultaneously and cause the dynamic steady wear. As a result, the wear rate at 200 °C is slightly fluctuant.

Optimization analysis of track comprehensive quality in micro-plasma cladding process

The purpose was to clarify the relationship between the main process parameters of micro-plasma cladding and the comprehensive quality (geometry, microstructure and wear rate of cladding track). Self-fluxing ferrous alloy powders were fabricated on Q235 substrate. Based on the uniform design, the distribution of the experimental samples was designed reasonably in the sample space, which greatly improved efficiency and reduced costs. After a series of microstructural characterization, there was no difference in the phase composition of all samples, but the average grain size had a significant difference, which resulted in the change of wear rate. And the relationship among micro-hardness, average grain size and wear rate of the track had also been investigated. Subsequently, an optimization model was established and the optimal process parameters were obtained with excellent wear rate under the geometric constraints. The correctness of optimization model was verified by experiments.

Investigation on dry sliding wear behavior of Mg/BN nanocomposites

Abstract The present research objective is to investigate the effect of boron nitride nanoparticles reinforcement on dry sliding wear behavior of pure Magnesium and magnesium nanocomposites. The fabricated nanocomposites contains varied percentages of boron nitride such as 0% (pure Mg), 0.5%, 1.5% and 2.5% were synthesized by using powder metallurgy technique and followed by a hot working process called hot extrusion. The pin on disk equipment was used for conducting the wear tests for traditional loads of 5 N, 7 N and 10 N at different sliding speeds of 0.6, 0.9 and 1.2 m/s against the steel disk at room temperature. For all traditional loads and sliding speeds, the changes in wear rate and friction co-efficient (µ) with respect to sliding distances were observed and analyzed. The wear characteristics are observed with the help of scanning electron microscopy under given test conditions. To investigate dominant wear mechanisms for various test conditions, the morphologies of all worn composites surfaces were analyzed. Final results show that, for all nanocomposites the wear level raises with respect to the sliding speeds and loads. Magnesium reinforced with 0.5% boron nitride shows lower wear rates and low friction coefficient values compare with magnesium reinforced with 1.5% boron nitride and 2.5% boron nitride nanocomposites.