Wear Transition Research Articles

Experimental study on tribological behavior of a binderless cemented carbide at high contact stress

Knowledge of frictional evolution and associated damage mechanism during sliding wear conditions using binderless WC-based cemented carbide is lacking. In this study, the frictional evolution and corresponding transformation of microstructure, and wear mechanisms of Al2O3/WC-based cemented carbide due to the effect of different contact pressure, especially high pressure have been explored using a reciprocating ball-on-flat sliding wear tester, which was experimentally simulated following the ASTM G133–02 standard. The dynamic curves in friction coefficient with the sliding time were described. The microscopic 3D topography of contact surface was obtained by the MFP-3D atomic force microscope. The material removal and the wear rate were discussed. Worn surface morphologies at different moments, cross-sectional images of wear tracks at different loads, and wear debris were taken by field emission scanning electron microscope. The results suggested that the pressure plays a decisive role in frictional evolution and wear characteristics. Two models of frictional evolution were declared. A novel “surge” phenomena in friction coefficient was found and explained at high contact pressure. Wear transition from mild wear to severe wear was confirmed. More than one wear mechanism was observed, including micro-cutting (polishing), generation and propagation of cracks, cracking-induced spalling, plastic deformation, and the formation of tribolayer.

Chaotic dynamic analysis of electrical contact resistance measured in sliding current-carrying friction

This work explores the dynamic laws of electrical contact resistance (ECR) signals measured in the sliding current-carrying friction tests based on chaos theory. It is found that ECR time series have a chaotic nature, strongly verified by the positive largest Lyapunov exponent λ1. The chaos may originate from the combined friction effects on short and long timescales. Phase space analysis indicates that the ECR phase trajectory adheres to the “convergence–stability” evolution law over time, which pertains closely to energy dissipation. Hence, the chaotic attractor exists during current-carrying friction. Strikingly, wear surfaces confirm that the ECR phase trajectory evolution process corresponds to the stages of “formation–keeping” of the chaotic attractor, and also agrees with the electrical wear stages of “running-in–steady-state”. Further, the chaos quantifier variation is consistent with the phase space analysis results to identify wear transition quantitatively.

Temperature-copper content induced wear mechanism transition in Cu/Ni60A composites

Coppery blast furnace tuyere is easily damaged in high temperature wear environment. Preparing a Ni60A coating by plasma cladding is an effective method to improve its wear resistance and service life. Controlling the appropriate dilution rate is the key to obtain high-quality coatings. The existing research has no clear conclusion on the range of dilution rate of coating for coppery tuyere. In this paper, a series of Cu/Ni60A composites with different copper content (10 wt%, 20 wt%, 40 wt% and 60 wt%) were prepared to mimic Ni60A coatings exhibiting distinct dilution rate. Under the coupling change of temperature and copper content, the wear mechanism of Cu/Ni60A composites showed a complex transition law. Copper content, surface oxide layer (NiO or CuO) and high-temperature softening temperature were the decisive factors of wear transition. The applicable temperatures of Cu/Ni60A composites with low copper content (10 %, 20 %), middle copper content (40 %) and high copper content (60 %) were about 600 °C, 400 °C and 300 °C, respectively. Combined with the heat transfer analysis results, the suitable dilution rates for the coating applied to the inner wall (＜10 %) and front end (10 %-20 %) of tuyere was revealed.

Ti6Al4V interacting with Al2O3 under ambient and vacuum conditions: Effect of plastic deformation and tribo-chemical reactions on wear mechanisms

Tribological interaction is a synergy between several mechanisms. In this paper, those pivotal mechanisms are studied by investigating the sliding interaction of Ti6Al4V (referred to as Ti64) pins against an Al2O3 disc under both ambient and vacuum environments. The impact of sliding speed was examined by altering the rotation rate (measured in ms−1) of the disc. This assessment utilized a 6.6 mm diameter pin, while keeping the load and environmental conditions consistent across all experimental trials. The findings reveal that in ambient environment, the frictional characteristics and wear rate of the tribological pair are intricately influenced by a synergistic interplay between plastic deformation and tribo-chemical reactions (TCR). A transition in wear mechanism occurs from abrasion to composite type (abrasion + oxidative) to oxidative with step-wise increment in sliding velocity (0.01–1.5 m/s). Coupled action of the TCR sub-mechanisms, viz. tribo-oxidation and formation of mechanically mixed layers (MML) play a pivotal role in the aforementioned wear transition. For vacuum-based experiments, the prevailing wear mechanism is exclusively dictated by plastic deformation. This phenomenon is in turn regulated by adiabatic shear banding (ASB)/strain rate response (SRR) at lower speeds, while at higher speeds, temperature-induced effects (phase transformation assisted thermal softening) come into action. Adhesion takes precedence in governing the material removal process, given that the development and activity of tribo-oxides and MML are impeded in the absence of air. Further, additional tests to study the effect of change in the pin-diameter (2.1, 4.6, and 6.6 mm) on the tribological response are performed and analysed.

Research on tool wear state identification method driven by multi-source information fusion and multi-dimension attention mechanism

Cutting tool wear condition monitoring technology is the key technology of advanced manufacturing system and a crucial component of machining. The stage of the tool wear has a direct impact on performance of the workpiece and efficacy of machine tool. However, the duplication and lack of wear information and the fuzzy area of the tool wear transition stage are the key factors contributing to the incorrect estimation of the tool wear state when extracting cutting tool wear feature information. As a consequence, this study presents a data fusion from several sources-based intelligent tool wear state detection technique. The fusion of data from several sources can effectively realize the complementarity of machining information. This provides the model with more comprehensive identification data. The mapping between wear state and wear characteristics is precisely established. To address these issues, the attention mechanism of channel and spatial latitude is integrated into the feature extraction. The model that was constructed in the present investigation has a comprehensive identification accuracy of 0.982. The F1 score of initial, normal and severe wear stage of tool wear are 0.977, 0.968 and 0.993, which are better than other models. Experiments show that the identification method proposed in this study may provide accurate tool wear condition identification based on machining process data, allowing for more flexible and precise cutting tool change decisions in machining.

Comparison of Tribological Characteristics of LM13/B4C and LM13/Ilmenite Composites at High-Temperature Conditions

Abstract In this work, high-temperature tribological characteristics of ilmenite-reinforced LM13 aluminum alloy–based matrix composites (AMCs) and boron carbide–reinforced AMCs are compared. Stir-cast composites were processed using boron carbide (covalently bonded discontinuous particles (CDP)) and ilmenite (natural discontinuous particles (NDP)) particles separately as reinforcements. The particle size range was 106–125 µm, and reinforcement levels were 5, 10, and 15 wt% for both types of composites. Both composites exhibited a uniform distribution of reinforced particles and grain refinement. Compared to the LM13 base alloy, NDP composite containing 15 wt% reinforcement showed significant improvement in hardness (57%), coefficient of friction (57%), mild-to-severe wear transition temperature, average steady-state wear-rate (49%), and coefficient of thermal expansion (55%). CDP-15 composite showed slightly better properties than NDP-15 composite. Microstructure refinement, increased dimensional stability, formation of the oxide layer, and formation of tribolayer due to reinforcement of the ceramic fillers were the main reasons for the improvement in properties of processed AMCs. Scanning electron microscope (SEM)-energy dispersive spectroscopy (EDS) of wear tracks-debris showed abrasive/delamination wear as the main mechanism for materials loss. The research showed that the low-cost ilmenite particles can substitute for the very costly boron carbide particles as reinforcements in AMCs used for dry sliding wear applications under high operating temperatures–applied load conditions of the order of 300 °C–49 N.

Dry and Lubrication Sliding Wear Characteristics and Wear Mechanism Mapping for In Situ Al–25Mg2Si Composites

This study investigates the wear characteristics of Al–25Mg2Si composite synthesized via gravity casting. The research aims to understand the influence of applied load, test temperature, contact condition (dry and lubrication), and sliding distance on wear characteristics. Results show that higher loads and temperatures lead to increased wear loss and coefficient of friction. The worn surface morphology for higher loads and temperature shows deeper scratches and grooves, indicating severity in wear. The debris size and volume increase with an increase in load and temperature. The dominant mechanism is abrasive, adhesive, and oxidative for both the room‐ and high‐temperature dry sliding conditions. However adhesive and oxidative wear increase with the increase in test temperature. Abrasive wear is the only wear mechanism present during the lubricating sliding condition. Wear transition is noticed during the wear map analysis subjected to load, temperature, and sliding distance. In the case of room‐temperature test, severe–moderate–mild wear transition occurs with the increase in sliding distance and mild–moderate–severe wear transition occurs with the increase in test temperature and applied load. The roughness of the worn surface increases with an increase in applied load and temperature and the use of lubricant hugely reduces the surface roughness.

A study on the tribological behavior of AZ31 magnesium alloy sheets processed by temperature-assisted ultrasonic shot peening

Mg alloy, as a promising lightweight structural material, finds applications in various fields. However, poor surface properties like wear resistance greatly limit its applications. As a surface modification technology, ultrasonic shot peening (USP) has gained significant popularity. In this study, temperature-assisted USP (TA-USP) was firstly applied to AZ31 Mg alloy. The influence of peening duration and temperature on microstructural evolution and mechanical properties was investigated in details. The ball-on-disk dry sliding wear test was performed to examine the tribological behavior. The results show that a gradient microstructure and surface nanocrystallization are introduced by TA-USP. The gradient becomes significantly pronounced as the peening duration extends. The surface hardness increases from the as-annealed 60.9 ± 1.8 HV to 159.0 ± 6.1 HV after processed at room temperature with 800 s, and a depth of about 600 μm for the affected region is achieved. When the peening temperature is raised, the gradient weakens, even disappears at 300 °C, and the hardness decreases. Notably, the gradient microstructure and enhanced hardness exhibit significant thermal stability below 200 °C. The wear curves and morphology analysis suggest that TA-USP obviously improves wear resistance. The surface nanocrystalline results in an easy formation of MgO patches and reduces the coefficient of friction. Moreover, the presence of gradient microstructure also retards the delamination phenomenon. Increasing peening duration or temperature to a moderate level will lead to an enhanced wear resistance, owing to its dependence on both hardness and toughness. A simplified wear transition map is roughly established to predict optimum wear resistance.

Tool anisotropic wear prediction and its influence on surface topography in diamond turning of oxygen-free copper

Oxygen-free copper components are widely used in high energy physics engineering, which are usually fabricated by the diamond machining process for achieving low roughness surface. However, the wear of diamond tool heavily affects the surface quality. In this work, the wear law of diamond tool in machining of oxygen-free copper is studied with consideration of the anisotropy of diamond strength. Firstly, the stress distribution on the tool face in machining is calculated. The results show that the cutting stress near the flank face is larger than that near the rake face. Secondly, the strength distribution of tool cutting edge is modeled. The theoretical prediction reveals that the anisotropy of diamond crystal leads to the great differences in the strength of cutting edge at different positions, and further affects the cutting edge wear resistance. Thirdly, the wear model of diamond tool is established with consideration of cutting stress distribution and tool edge strength, in which the mechanical wear is the dominant wear process. Finally, the variation of the surface roughness is analyzed on the basis of the tool wear through the cutting experiments. The experiment results indicate that the surface material deformation is closely related to the tool cutting edge wear transition area and results in different values of surface roughness. The obtained results can improve the understanding of the diamond tool wear law and estimate the diamond tool wear in machining of oxygen-free copper.

Influence of abrasive characteristics on the wear micro-mechanisms of NbC and WC cermets during three-body abrasion

The present study has developed new insights into the wear transition mode of cermets and provides a better understanding of the role of abrasive characteristics in three-body abrasive wear. Two sintered and fully densified cermets, NbC–Ni (NbC–12Ni–10Mo2C) and WC-Co (WC-9.5Co) with similar micro-hardness (HV30 ≈ 13.5 GPa) were selected in this study. The abrasion response of cermets against different abrasive characteristics namely size (67–245 μm), hardness (silica, alumina and SiC), and shape (round and angular) was experimentally investigated according to the ASTM G65 standard. The test results showed that the specific wear rate (SWR) of the cermets increased significantly with increasing abrasive size and hardness. The size effect shows that the dominant wear micro-mechanisms shift from binder removal (rolling) to mixed binder-carbide extrusion (sliding) as the abrasives particle size changes from smaller (67 μm) to larger (245 μm). The hardness ratio between the abrasives and cermets (Ha/Hs) highlights that silica and alumina abrasives provide mild wear (Ha/Hs < 1.5), while SiC abrasives cause severe wear (Ha/Hs > 1.5). Both cermets exhibited similar SWR during mild wear, but NbC–Ni showed 7 times higher SWR than WC-Co during severe wear. The abrasives shape effect does not show a significant difference on the wear rate of the cermets.

The effectiveness of protective layer in reducing fretting wear of Alloy 690TT tubes/ 405 stainless steel plates

Fretting experiments of Alloy 690TT tubes against 405 stainless steel (405 SS) plates were carried out to evaluate the influence of temperature on fretting performance of Alloy 690TT tubes in air. The results indicated that an adhesive and smooth protective third body layer was generated on Alloy 690TT tubes above a certain temperature, between 150 ℃ and 200 ℃ for given conditions. The protective layer was a mixture of oxides and transferred 405 SS, which was directly associated with fretting conditions. Thus, a wear transition map of Alloy 690TT was established. Besides, the results of this work also revealed that the plastic deformation of 285 ℃ was slighter than that of 150 ℃.

Evaluation of physical, mechanical and sliding wear properties of in-situ AB-TiC composite: a comparison with NAB alloy

The purpose of the present study is to evaluate the physical, mechanical and sliding wear properties/response of cast in-situ aluminium bronze (AB)-TiC [(Cu10Al3Fe)5TiC] composite and compare with cast nickel aluminium bronze (NAB) [Cu10Al5Ni5Fe] alloy. Sliding wear tests were conducted in dry and partially lubricant conditions using a pin-on-disc machine. A test material in the form of pin was evaluated against a rotating heat-treated EN-31 steel disc. Wear loss, frictional heating and friction coefficient properties were examined. The NAB alloy showed higher tensile strength (32.7%), compressive strength (7.68% at room temperature. and 4.18% at 500 °C), hardness (8.78%) and density (3.17%), whereas thermal conductivity of the AB-TiC composite was found 4.89% higher than NAB alloy. In dry sliding condition, composite outperformed NAB alloy in terms of wear resistance up to a critical applied load and/or sliding speed. Beyond this point, the wear behavior altered. Increasing sliding speed caused to reduce wear transition load. While friction coefficient showed mixed trend. Under lubricated wear test conditions, AB-TiC composite displayed considerably higher wear resistance (50.08%, 44.41% & 51.55%) and friction coefficient (26.37%, 40.75% & 14.96%) than the NAB alloy when tested in only oil, oil with 100 μm graphite and oil with 7–10 μm graphite respectively. Arrival of seizure in general caused significantly higher wear loss and temperature rise. In addition, it caused large adhesion of the specimen material to the disc surface. The reported wear behaviour of the samples has been validated using the features of wear surfaces and subsurface regions. The latter also permitted to comprehend the working wear processes. The analysis significantly shows good impacts of the oil lubrication (with and without solid particles) in terms of decreasing wear rate, frictional heating, and friction coefficient. Formation of steady lubricating film/layer was reported to be responsible for the better wear performance of the samples. Furthermore, irrespective of material composition and microstructure there exists a precise set of test parameters (e.g. load and speed) leading to optimal wear performance wherein the beneficial impacts of load bearing capability, thermal stability of various phases predominates.

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.

Dry wear characteristics of TC21 titanium alloy at elevated temperatures

TC21 alloy is a new type of high damage tolerance titanium-based alloy, but its elevated-temperature wear characteristics such as wear mechanism and wear transition are still unknown. In present study, dry wear tests of TC21 alloy were carried out at experimental temperatures of 20 °C–300 °C under various applied loads. Volumetric wear rate was plotted against experimental temperature under each applied load to exhibit its variation trend and mild-severe wear transition. Scanning electron microscopy was used to examine worn surface morphologies. Confocal scanning laser microcopy and Vickers microhardness tester were utilized for characterizing the friction-affected microstructure and mechanical property in the subsurfaces. Four wear mechanisms, namely abrasion, adhesion, mild surface deformation and severe surface deformation, were observed. Severe surface deformation was found responsible for severe wear behavior, and it was aroused by the near-surface softening originating from dynamic recrystallization (DRX). The severe wear transition temperature was found to be decreased linearly with increasing applied load. By linearly fitting the relation between applied load and transition temperature, a critical surface temperature of 399.4 °C for severe wear transition is estimated, and it is further deduced to be the critical temperature for DRX realization of surface material during sliding.

Temperature-frequency wear mechanism maps for a heat-resistant austenitic stainless steel

A systematic experimental investigation is used to establish the influence of temperature and cycling frequency on the friction and wear behavior of the high-Cr, high-Ni heat-resistant austenitic stainless steel 310S (25%Cr–20%Ni) under gross slip fretting wear. The contact configuration is cylinder-on-flat using a like-on-like tribopair. Temperatures range from 20 °C to 700 °C and cycling frequencies range from 1 Hz to 50 Hz. A workflow to generate the wear maps with minimal number of tests, namely hierarchical probing and sampling strategy, is used to clearly establish the severe-to-mild wear transition associated with glaze layer formation. The critical temperatures related to this transition along with the number of cycles needed to establish effective glaze layer protection are obtained. A recent model reported in the literature that determines the number of cycles needed to establish effective glaze layer protection at different temperatures and frequencies gives good prediction if the temperature rise at the contact surface due to Coulomb heating is accounted for.

Effect of the normal load on the sliding wear behavior of Hadfield steels

This work studies the tribological behavior of Hadfield steel under sliding wear conditions. Wear tests were performed on Hadfield steel in the pin-on-disk configuration. The pins were manufactured from Hadfield steel, and the discs were manufactured from H-13 (600 HV). The normal load varied in 6 levels between 50 N and 500 N, and the test time and sliding speed were 0.18 m/s and 60 min, respectively. The friction force was monitored during the tests, and the mass loss was obtained afterward. Microhardness profiles were taken in the cross section. The worn surfaces and subsurface were analyzed with scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that the mass loss increases with increasing normal load until the load reaches 100 N, but the mass loss decreases for subsequent increments until the load reaches 300 N. After increasing the normal load to 500 N, the mass loss increases again. The lowest and highest values of mass loss occur at loads of 50 N and 500 N, respectively. The peak mass loss is at a 100 N normal load, suggesting that some of the tests were conducted after the known severe–moderate wear transition. The coefficient of friction decreases monotonically with increasing normal load. Worn surface analyses show evidence of more severe wear after applying higher loads (300 N–500 N). The wear mechanisms of the higher loads are plastic deformation, abrasion, rupture, and oxidation of the oxide layer; the wear mechanisms of the lower loads are oxidation and adhesion. The area fraction of oxides on the worn surface increases with increasing normal load, justifying the reduction in the coefficient of friction. A martensitic transformation occurs in tests with normal loads between 300 N and 500 N, justifying the increase in hardness after the tests.

Investigation of the wear transition in CoCrMo alloys after heat treatment to produce an HCP structure

This study reports that the wear rate of the heat-treated CoCrMo alloy shows a sudden transition of more than 5-fold when the load/contact pressure increases from 45 N (3.6 GPa) to 50 N (3.7 GPa). Heat treatment was used to change the structure of the commercially available CoCrMo from the initial face-centred cubic (γ-fcc) with a small amount of hexagonal close-packed (ε-hcp) to predominantly hcp ε-phase with dispersed nanoscale precipitates of σ-phase. PeakForce QNM was used to quantitatively map the local mechanical properties of the surface at the nanoscale. High-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscope (STEM), energy-dispersive X-ray spectroscopy (EDX), and precession electron diffraction (PED) integrated with the TEM is used to characterize the structure and chemical composition of the worn surface and tribofilm. The possible reason for wear transition was discussed.

Elevated-temperature wear behavior of Ti6Al4V alloy: microstructural evolution and properties change in subsurfaces and mild-severe wear transition

Dry sliding wear behavior of Ti6Al4V alloy was studied at elevated temperatures of 50 °C–400 °C. The constituent phases and morphologies of worn surfaces were examined to evaluate the roles of oxide layers and wear mechanisms in mild-severe wear transition (M-SWT). Microstructural evolution and hardness change in subsurfaces were also investigated to reveal the most fundamental reason for M-SWT. The results showed that M-SWT happened via severe plastic deformation (SPD) within 20 °C–350 °C, while mild wear prevailed via a protective mechanically mixed layer (MML) containing multiple oxide phases at 400 °C. Large surface plastic deformation and frictional heat activated dynamic recrystallization (DRX) softening in subsurface, which resulted in M-SWT. The critical load for M-SWT presented an approximate linear relationship with testing temperature within 20 °C–250 °C, from which a critical temperature of 555.8 °C for M-SWT was obtained by linearly fitting method. It was thought as the critical temperature for DRX realization in surface layer, and it was utilized to calculate the transition loads at 300 °C and 350 °C.

On Friction, Heat Input, and Material Flow Initiation during Friction Stir Welding: Tool and Process Optimization

The Friction Stir Welding (FSW) process depends entirely upon mechanical contact between the tool and the workpiece. As a result of this, all process phenomena and process outcomes such as weld geometry and mechanical properties are governed by FSW’s frictional system. The following work characterizes this system with a focus on process initialization, heat input and material flow. For this purpose, an experimental program for the isolated investigation of the frictional system was carried out. Short-term effects such as contact initiation, run-in behavior and frictional transitions are considered as well as the influences of process parameters and geometry. The system and its behavior are analyzed quantitatively and qualitatively by experiments altering the normal pressure, relative velocity, and tool geometry. The experiments demonstrate a self-similar behavior of the process, including an important wear transition which initiates the material flow, and a subsequent equilibrium of forces, heat balance, and temperatures. The interaction between the tool and the welded material is described, as is the link between the frictional interface and material flow initialization. Based on these findings, recommendations are provided for process optimization and tool design.

A grey-fuzzy based multi-response optimisation study on the friction and wear characteristics of titanium diboride reinforced aluminium matrix composite

Aluminium matrix composites are nowadays used globally as a substitute for other cast alloys because of their augmented properties. The present experiment deals with the fabrication and characterisation of tribological behaviour of titanium diboride reinforced aluminium matrix composite on a pin-on-disc tribotester under dry sliding condition. In this work, an attempt has been made to minimise the friction and wear characteristics of Al2024-TiB2 composite, by optimising the tribological parameters viz. applied load, sliding speed and sliding distance using grey-fuzzy approach. The tests are carried out based on Taguchi’s L25 orthogonal array. Grey-fuzzy analysis is used for converting the multi-objective optimisation problem into a single-objective optimisation. Based on the grey-fuzzy analysis, the optimal combination of tribological parameters is L1S4D2 (10N load, 2.0 m/s sliding speed and 1000 m sliding distance). The optimal combination of parameters has also been validated with a confirmatory experiment. Analysis of variance (ANOVA) for grey fuzzy grade shows that sliding distance is the most significant parameter affecting tribological performance. SEM analysis of the worn surfaces revealed that, increase in sliding distance results in wear transition from mild to severe. The proposed grey-fuzzy method is found to be successful in solving multi-response tribological problems.