Specific Wear Mechanisms Research Articles

Enhancing Machining Efficiency: Real-Time Monitoring of Tool Wear with Acoustic Emission and STFT Techniques

Tool wear in machining is inevitable, and determining the precise moment to change the tool is challenging, as the tool transitions from the steady wear phase to the rapid wear phase, where wear accelerates significantly. If the tool is not replaced correctly, it can result in poor machining performance. On the other hand, changing the tool too early can lead to unnecessary downtime and increased tooling costs. This makes it critical to closely monitor tool wear and utilize predictive maintenance strategies, such as tool condition monitoring systems, to optimize tool life and maintain machining efficiency. Acoustic emission (AE) is a widely used technique for indirect monitoring. This study investigated the use of Short-Time Fourier Transform (STFT) for real-time monitoring of tool wear in machining AISI 4340 steel using carbide tools. The research aimed to identify specific wear mechanisms, such as abrasive and adhesive ones, through AE signals, providing deeper insights into the temporal evolution of these phenomena. Machining tests were conducted at various cutting speeds, feed rates, and depths of cut, utilizing uncoated and AlCrN-coated carbide tools. AE signals were acquired and analyzed using STFT to isolate wear-related signals from those associated with material deformation. The results showed that STFT effectively identified key frequencies related to wear, such as abrasive between 200 and 1000 kHz and crack propagation between 350 and 550 kHz, enabling a precise characterization of wear mechanisms. Comparative analysis of uncoated and coated tools revealed that AlCrN coatings reduced tool wear extending tool life, demonstrating superior performance in severe cutting conditions. The findings highlight the potential of STFT as a robust tool for monitoring tool wear in machining operations, offering valuable information to optimize tool maintenance and enhance machining efficiency.

Topography characterization of friction pairs during the real-time wear process in dry condition

At present, the prediction of wear failure is often based on temperature, friction coefficient, vibration, and other single or a few macroscopic parameters to judge the contact condition of the friction pairs. However, there are still deviations between the measured results and the actual situation. In the digital twin system for studying friction and wear phenomena, in-situ measurement and characterization of topography of friction pairs is a challenge problem which does not exist in other procedural twin systems. This paper investigates the relationship between in-situ measured macroscopic parameters and topographical parameters. First, the dynamic relationship between friction coefficient and fractal parameters is derived from the view of a microscopic contact, and the wear periods are determined based on the dynamic changes of fractal parameters. The derived friction-fractal formula is based on mechanical deformation and the Majumdar and Bhushan rough surface contact model, avoiding the assumptions based on specific wear mechanisms, then having the universal property. Second, the experimental verification is carried on which demonstrates good correspondence between the obtained topographical parameters based on the friction-fractal formula with the experimental results. The obtained friction-fractal formula provides a theoretical basis for predicting and analyzing the wear status of friction pairs in the critical equipment and supports the real-time contact state characterization of the friction pairs in the digital twin system.

Microstructure and wear resistance of in-situ TiC reinforced Stellite 6 coating using PTA cladding

To enhance the durability of copper tuyeres in blast furnaces, it is necessary to apply coatings on their surfaces to protect against wear caused by high-temperature coke. In this study, a series of in-situ synthetic TiC-reinforced Stellite 6 alloy coatings containing a Ni60A interlayer were successfully produced on copper substrates using 5–45 wt% TiFe/Cr3C2 precursor powders. The coatings exhibited excellent metallurgical bonding with the Ni60A interlayer, and an elemental transition zone was formed at the interface between the coating and the interlayer. XRD Rietveld refinement analysis revealed that the T45 coating with 45 wt% of precursor powder showed the highest TiC phase content of 12.27 %, with an average hardness of 658.15 HV0.2, which was 31.2 % higher than that of the Stellite 6 alloy. The wear mechanism of the Stellite 6 coating was plastic delamination at 25 °C, and oxidative wear at 500 °C. As the TiC particle content in the coating increased, the dominant wear mechanism tended to shift towards abrasive wear. The specific wear mechanism of the coating was influenced by the content of coating phases and the operating temperature. The best wear resistance was achieved by the T45 coating, which showed an abrasive wear mechanism at both 25 °C and 500 °C, with a wear resistance of 4.47 and 5.94 times higher than that of the Stellite 6 alloy respectively.

Influence of microstructure on degradation of cast graphitic high-speed steel

Work rolls used in hot rolling of steel suffer severe wear caused by combinations of adhesion, abrasion, rolling contact fatigue, thermal fatigue, and tribo-chemical corrosive attack. Depending on the specific wear mechanisms, damage of these rolls may include loss of material, surface, and subsurface cracking, as well as impairment of the surface finish. In this work, wear tests were performed using a custom-designed roll test rig which simulates the contact conditions between the work roll, the back-up roll and the hot-rolled steel. To simulate typical conditions occurring in a hot rolling mill, different contact pressures and rolling temperatures were considered. Wear and damage mechanisms were analyzed by optical microscopy and scanning electron microscopy (SEM). A systematic approach was used for correlating wear and microstructure of the roll materials. Therefore, graphitic high-speed steels (G-HSS) with different fractions and types of carbides were investigated. MC and M2C/M6C were identified to influence mainly the wear behavior of G-HSS. Increasing the fraction of these carbides reduced the wear rate but increased the surface roughness. The optimum balance between carbide types, graphite content and metal matrix has been identified as mandatory for achieving high wear performance of work roll materials.

Wear behavior and microstructural transformation of single fcc phase AlCoCrFeNi high-entropy alloy at elevated temperatures

Abstract In this research, the wear behavior and microstructural transformation of approximately single face-centered cubic phase AlCoCrFeNi high-entropy alloy at elevated temperatures (∼25–600 °C) were investigated in detail. The combined action of environmental temperature and friction force can induce significant and regular transformation of the preferred orientation of crystalline grains at the high-entropy alloy friction interface. Generally as the temperature rises its principal wear mechanism varies fairly regularly from abrasive wear to delamination wear, and then to adhesive wear. It is worth noting that at a test temperature of 100 °C the wear debris formed during friction was rolled repeatedly and then separated by delamination, which played a pivotal role in inhibiting wear. Furthermore, five specific wear mechanisms of face-centered cubic phase high-entropy alloy at elevated temperatures have been elucidated through this study.

Tribological behavior of femtosecond laser-textured leaded brass

The tribological behavior of femtosecond laser-textured leaded brass samples under five surface roughness and four lubrication conditions were studied. The results have shown that under a variety of lubrication conditions, the coefficient of friction of laser-textured leaded brass exhibited consistent changes. As the roughness increased, the friction coefficient first increased and then decreased. Under a variety of friction conditions, the surface roughness was different when the friction coefficient was the smallest. Under the conditions of dry friction, water lubrication, starved-oil lubrication, and oil lubrication, the maximum reduction ratio of the coefficient of friction was 13.28%, 27.64%, 8.09%, 10.79%. The wear mechanism was mainly adhesive wear and abrasive wear, but there were also differences in specific wear mechanisms. Corrosive wear still existed under the water lubrication. The wear area of the laser-textured surface was larger than that of the unprocessed surface. According to the above sequence, except for water lubrication, the maximum reduction ratio of the wear area was 8.54%, 51.35%, and 88.39%.

RETRACTED: Mechanisms involved in the tool life improvement of laser assisted machining 45%SiCp/Al composites

Abstract Published reports indicate that laser assisted machining (LAM) is an emerging manufacturing process for improving the productivity when machining metal matrix composites (MMCs), but there is still debate about whether the LAM is beneficial for improving the tool life, and also many arguments about the tool wear mechanism. This study evaluates the tool life and specific wear mechanisms of the uncoated and coated carbide tools in LAM of 45%SiCp/Al composites. It is discovered that the life of these two carbide tools is longer in LAM than conventional machining (CM) when the cutting temperature increasing from room temperature to 420 °C. Based on the results associated with tool wear, an improved archard-type model of abrasive wear in LAM was developed for predicting the average flank wear (VBavr) of two carbide tools. The corresponding experimental results matches well with it. In LAM abrasive wear was found to be the most predominant wear mechanism. An existing wear model associated with a critical value D/h has been used for characterizing the transition from two-body wear to three-body wear about the particles between the flank face of cutting tool and machined surface in LAM of 45%SiCp/Al composites. In addition, mechanisms involved in the tool life improvement of LAM 45%SiCp/Al composite has been explained by comparing a range of normal and tangential forces between particles and flank face of cutting tools with CM.

Mechanisms of oxide dependent tribological behavior in Ti / Steel sliding and influence of nanostructured surfaces

The tribological behavior of pure titanium having coarse-grained or nanostructured surfaces has been investigated against a steel ball moved with an alternative motion. The nanostructures were obtained by Surface Mechanical Attrition Treatment (SMAT) both at room and at cryogenic temperatures. An unexpected wear behavior was revealed: the hard steel ball was abraded for all cases even if it was several times harder compared to the Ti surface. This was due to the formation of a third body consisting of hard Ti oxides. Interestingly, important variations of the coefficient of friction were also revealed during the rubbing process. These variations could be separated into three successive stages, each with its specific wear mechanisms. The wear regimes were related to changes in the third body layer formed between the Ti and steel surfaces. SMAT changed the formation kinetics of the third body. The temperature at which the SMAT was conducted also introduced different third body formation kinetics. Important variations in the wear resistance were consequently observed between each surface condition.

Wear behavior of composite strengthened gray cast iron by austempering and laser hardening treatment

The present study mainly investigated the phase transformation and wear performance of laser hardened austempered gray cast iron specimens. Ball-on-Plate reciprocating sliding wear tests with PAO4 base oil were carried out on untreated, quench-tempered, austempered, laser hardened austempered gray cast iron specimens. Micro hardness profiles and worn surfaces were analyzed for specific wear mechanisms. It was found that four different zones were formed beneath the laser hardened surface including laser hardened zone (Ledeburite, ≈67HRC), upper heat affected zone (Martensite, ≈69HRC), lower heat affected zone (Tempered Ausferrite, ≈36HRC) and substrate (Ausferrite, ≈39HRC). In the sliding wear tests, the laser hardened austempered gray cast iron specimens showed higher wear resistance than others, which could be associated with the benefits of ausferritic structure with high fracture toughness and laser hardened regions with high hardness. By observing the worn surface, grooves and micro-sized material removal occurred within the substrate. The surface of the substrate ploughed by the asperities of the ball and hard wear debris stopped on the edge of the laser hardened regions since ledeburite and martensite had high hardness and abrasive wear resistance. However, some micro-cracks and spalls were developed within the laser hardened zone. The results obtained from this study could be used as reference in future research and applications of laser hardened austempered gray cast iron.

Study of Ni63-Co37 nanocrystalline electrodeposited alloy as anti-wear coating on mild steel substrate

Ni63-Co37 nanocrystalline electrodeposited alloy is studied as wear protective coating on StW24 mild steel. The analyses of coatings composition by XRF demonstrate an anomalous codeposition behavior of Ni-Co alloy. SEM shows that saccharine leads to the nanometric granular grains of Ni-Co coatings. XRD pattern of Ni-Co deposits confirms that the addition of saccharin in the electrolyte leads to crystallites size in the nanometric order and also to the predominance of (111) as preferential crystallographic orientation. Vickers micro-indentation shows that the solid solution hardening and the Hall-Petch strengthening lead to hardness of Ni-Co coating three times higher than that of substrate. The pin-disc wear tests under dry sliding conditions reveal that Ni-Co coated steel has much higher wear resistance than the uncoated substrate thanks to its relatively higher hardness, but the coated substrate shows higher friction coefficient because the formation of uncompleted tribofilm on its worn surface due to its specific wear mechanism, where SEM observations on the wear tracks morphologies of the uncoated and Ni-Co coated substrate show that the mechanism governing the wear of the bare steel is an abrasive oxidative mechanism, whereas that of the Ni-Co coated substrate is a mixed adhesive-abrasive oxidative mechanism.

Investigations on the mechanical properties and three-body wear behavior of pure Fe2B intermetallic with different chromium additions

The effects of chromium on the mechanical properties and three-body abrasive wear behavior of pure Fe2B intermetallic are investigated in this work. The results show that, with chromium addition from 0 to 4.88 wt%, the fracture toughness of pure Fe2B sample initially increases to the highest value of 7.06 MPa m1/2, and then decreases. The fracture toughness was improved by approximately 161.4% with chromium addition of 4.07 wt%. Simultaneously, with the increment of chromium addition, the wear mass loss decreases and then increases in case of both SiC and SiO2 abrasives. Through systematical analysis of the wear surface and subsurface, it can be found that fracture toughness plays a dominant role in reducing the wear mass loss. Specific wear mechanisms are also explicitly discussed.

Understanding the source of acoustic emission signals during the wear of stamping tools

Stamping tools are prone to wear due to the increased use of advanced high strength steels in the automotive industry. For active monitoring of the wear state of stamping tools using acoustic emission, it is important to establish a correlation between specific wear mechanisms and the acoustic emission signals. An adhesive wear mode (galling), which is commonly observed on the stamping tool, can occur in combination with multiple abrasive wear modes on the workpiece, such as ploughing and cutting. This study will establish a correlation between the sources of the acoustic emission signal to the specific surface wear mechanism observed in the stamping process. Therefore, to investigate the source of acoustic emission signal, sheet metal stamping wear tests were conducted using un-worn and worn tool steel dies (AISI D2) and advanced high strength steel sheet (DP780). Accelerated tribology tests were also conducted using a scratch tester with the same material combination, where galling, cutting and ploughing wear mechanisms were observed. By correlating the acoustic emission features, such as power spectral density from the stamping test and the scratch test, it was observed that the change in the acoustic emission signal observed in the stamping process could be attributed to the galling wear mechanismsThis study contributes to the fundamental understanding of different wear mechanisms in sheet metal forming process, the resulting acoustic emissions, and how these can be utilized to develop active monitoring of the tools in the future.

Carbide tool wear mechanisms in laser-assisted machining of metal matrix composites

Laser-assisted machining (LAM) is an emerging manufacturing process for improving the productivity when machining hard and high-strength materials. Recently, it has been interesting using the process to machine metal matrix composites (MMCs), and published reports indicate that machinability is improved. But there is still ambiguity about whether the new process is beneficial for tool life. The specific wear mechanisms for carbide tools in LAM remain unknown. This work clearly evaluates the tool life and wear mechanism for uncoated and coated tungsten carbide tools in LAM of Al/SiCp/45 % composites at different cutting conditions. It was concluded that abrasive wear was the most predominant wear mechanisms in LAM, controlling the deterioration and final failure of the carbide tools. The adhesion wear and diffusion wear were accelerated to some extent with an increase in the temperature. However, all of the three cutting tools in LAM have a longer tool life over conventional machining at given conditions. Based on the results from tool wear process in LAM, a physical model of tool wear in LAM has been developed. The paper aims at providing an insight into the tool wear characteristics and showing the great potential in the field of LAM of MMCs.

Understanding the tool wear mechanism during thermally assisted machining Ti-6Al-4V

Thermally assisted machining is an emerging manufacturing process for improving the productivity when machining many difficult-to-cut engineering materials. Traditionally the process is reserved for very hard and high strength materials where abrasive and notching wear mechanisms cripple tool longevity. Recently there has been interest in using the process to machine titanium alloys and published reports indicate that machinability is improved, namely though a reduction in cutting forces. However, there is still ambiguity about whether the process is beneficial for tool life and the specific wear mechanisms for carbide tooling remain unknown. This work characterises the tool life and wear mechanism for two uncoated carbide tools when turning Ti-6Al-4V at high speed. While it is observed that thermally assisted machining reduces the cutting forces, it is found that the process has a deleterious effect on tool life because the dominant wear mechanism associated with diffusion is exacerbated during thermally enhanced machining. The process is compared against coolant technologies from the literature using identical tooling and cutting parameters and it is found that cooling the tool suppresses adhesion-diffusion wear and significantly prolongs tool life.

Wear Behavior of CVD-Diamond Tools

Diamond cutting tools are often the only choice for the machining of high-strength and highly abrasive non-ferrous alloys. During machining, a complex interaction of different wear mechanisms takes place on the tools. This interaction considerably hinders a purposeful detection of specific wear mechanisms. Therefore, the objective is to systematically analyze the wear processes that occur when machining a hypereutectic aluminum silicon alloy with CVD-diamond tools. The main wear mechanisms are identified and the limits for the use of various CVD-diamond tools are indicated. The findings gained will serve in the further development of these high-performance cutting materials.

A study of the mechanical and magnetic performance of metal evaporated tape

There are substantial gains to be made in terms of recording density and frequency response if the particulate magnetic media is replaced by a continuous thin metal film. Very thin metal evaporated coatings applied to thin, flexible substrates present a unique set of contact problems, particularly when the recording head is in intimate contact with the tape and in helical scan formats. Some of these contact problems have been addressed in this work where we report on the identification of specific wear mechanism of metal evaporated tape. Mechanical, physical and chemical changes in the surface of the two commercially available ME tapes have been correlated to recording error and signal degradation measurements.

Entwicklung und Verschleißverhalten von Si3N4‐Schneidkeramik

AbstractSchneidkeramiken auf der Basis von Siliziumnitrid ermöglichen hohe Zeitspanvolumina, wenn der Zerspanprozeß und die Schneidstoffsorte aufeinander abgestimmt sind. Im Rahmen der durchgeführten Untersuchungen wurde die Möglichkeit untersucht, die Keramikeigenschaften selbst zu verbessern. Den Mittelpunkt der Untersuchungen bildeten Zerspanversuche zur Beschreibung des Verschleißverhaltens der Keramiken. Dazu wurden Dreh‐ und Fräsoperationen an Gußeisen mit Lamellen‐ und Kugelgraphit sowie Vergütungsstahl durchgeführt. Eingesetzt wurden kommerzielle sowie hartstoffverstärkte und in der Zusammensetzung der Sekundärphase optimierte Siliziumnitrid‐Schneidkeramiken. Zerspanversuche sowie hochauflösende transmissionselektronenmikroskopische Aufnahmen zeigen, daß beim Drehen die thermisch bedingten Verschleißformen zum Tragen kommen, beim Fräsen die durch die mechanische Beanspruchung hervorgerufenen Verschleißformen dominieren. Die konsequente Umsetzung der gewonnenen Erkenntnisse führte zur Entwicklung einer innovativen Siliziumnitridkeramik mit einer deutlich gesteigerten Prozeßsicherheit.

Aspects of various processes for coating and surface hardening

The manufacture of hard surfaces for tribological and many tooling applications normally involves altering the outer microstructure of the original tool or component by introducing a source of strengthening, by effecting a transformation to a harder phase, or by superposing a covalently bonded structure. However, hardened surfaces may not provide the best solution to a wear problem and it may prove preferable to use a coating material in its bulk form, or to use one of the new toughened ceramics. A review is made of relevant processes, the characteristics that provide resistance to specific wear mechanisms, and sources of weakness such as the origin of residual stresses. It is concluded that despite the concentrated effort in research on processes for coatings and for hardening surfaces the understanding of the dependence of mechanical properties on microstructure in very thin coatings is poor. No reliable tests exist for measuring mechanical properties and as a result, attempts at characterizing hard surfaces provide little information to guide a potential user.

Toward a Mechanical Wear Equation

It is first shown that the simple form of linear wear/load relation of the adhesive and abrasive wear laws arises from the nature of the asperity distribution. Without recourse to specific wear mechanisms, simple concepts for material properties, size of wear particles, and the production of wear particles are introduced. This procedure leads to an increasing appreciation of those factors which might be embraced by the specific wear constant. Of particular interest is the role of ductility in wear behavior. Finally, these ideas are extended to deal with the wear of surface films where it is seen that the film thickness is of paramount importance. Some experimental evidence for the concepts used is also provided.