Wear Land Research Articles

Occurrence of catastrophic tool wear patterns through systematic thermomechanical modeling

To achieve optimal tool performance, it is essential to not only comprehend the wear patterns during the steady wear stage but also the final one where catastrophic wear patterns are usually involved. However, previous focus has been put individually into them, thereby the mechanism connections in between have not yet been completely demonstrated. This study aims to bridge this gap by developing an analytical model based on the slip-line theory and imaginary heat source formulations for worn tools with cutting edge geometry extracted from the steady wear stage. The model computes the thermomechanical loads on the tool surface, which are then incorporated into a mechanism-based wear rate model that has been carefully calibrated. Finally, a nodal-displacement algorithm is used to iteratively determine the further tool edge profiles until the final wear stage. The sequential edge profiles demonstrate that the most significant wear increments occur at the rear of the tool flank wear land, resulting in a gradually deepening and widening notched region. These predictions are consistent with experimental findings where a notch belt wear is observed to grow along the tool main cutting edge during the steady wear stage, which ultimately decreases the edge toughness and leads to catastrophic wear patterns.

Wear mechanism analysis and its effect on the cutting process of CBN tools during laser ultrasonically assisted turning of tungsten carbide

Tungsten carbide, known for its high hardness and brittleness, presents a challenge in traditional processes due to severe tool wear and shortened tool life, impacting machining efficiency. This paper introduces a hybrid turning method – laser ultrasonically assisted turning (LUAT) – for precision and efficient machining of tungsten carbide. LUAT combines tool ultrasonic vibration with laser-induced workpiece heating to enhance the cutting performance of tungsten carbide. Thermal modeling is utilized to determine suitable LUAT parameters. Comparative experiments are conducted to assess the advantages of LUAT in enhancing tool performance and improving surface quality. Results indicate that, compared to traditional turning, ultrasonically assisted turning, and laser assisted turning, LUAT significantly reduces tool wear and enhances tool lifespan. In LUAT of tungsten carbide, the tool wear on the rake face exhibits long strips parallel to the tool edge, while the flank face presents triangular wear land, shallow pits, and grooves. Investigation into wear characteristics and mechanisms of cubic boron nitride (CBN) tools reveals that adhesion, oxidation, and diffusion are major wear factors, with chipping and tipping being abnormal wear patterns for CBN tools. Intensified tool wear elevates cutting forces and cutting temperatures, deteriorating the surface quality of tungsten carbide turning. However, LUAT mitigates these effects, resulting in lower cutting forces and temperatures within the same wear time, improving surface quality.

The Study of Tool Wear Mechanism Considering the Tool–Chip Interface Temperature during Milling of Aluminum Alloy

ADC12 aluminum alloy has been widely used in the aerospace, ship, and automotive fields because of its high specific strength, excellent die-casting performance, and wear resistance. Adhesion wear is the main wear mechanism of high-speed milling ADC12 aluminum alloy. The most important factor affecting adhesion wear is the tool–chip interface friction, which is directly manifested in the tool–chip interface temperature. Therefore, the temperature variation during the milling of aluminum alloy is analyzed using a temperature field model and infrared temperature measurement technology. Then, the tool wear morphology and the tool wear land width are observed using a scanning electron microscope. Finally, the tool wear mechanism considering the tool–chip interface temperature is discussed. The tool–chip interface temperature is related to the friction angle, tool–chip contact length, and friction force at the rake face, which increases first and then decreases as the cutting speed and feed rate increase. During the formation of the adhesive layer, the tool–chip interface temperature increases, the change rate of the cutting force and the tool wear rate increase, and adhesion, oxidation, and abrasive and delamination wear are generated on the tool surface. With the increase in temperature, the tool wear rate increases, the molten adhesive layer on the tool surface is accompanied by crack propagation, and adhesion wear, oxidation wear, and abrasive wear occur on the tool surface.

Multi-attribute optimization of drilling CFRP/Ti-6Al-4V alloy hybrid stacks using VIKOR

Drilling carbon reinforced polymer composites (carbon fiber-reinforced polymers, CFRP) and the hole quality produced are highly critical and significantly influence the performance and reliability of structures used in aircraft components. When CFRP composites are stacked together with titanium alloy, the damage caused by the machining operation is incalculable due to the burr and chip evacuation of metallic phases. In this article, efforts were made toward the identification of optimal machining conditions in drilling CFRP/titanium hybrid stacks. Experimental investigations on dry drilling of CFRP/titanium stacks were conducted with the aid of tungsten carbide drills. This research article discusses an improved compromise ranking method named VIKOR (VIseKriterijumska Optimizacija I Kompromisno Resenje) to determine the optimal machining parameters in drilling of CFRP/titanium stacks to produce high-quality holes. Attributes measured from experimental trials are: delamination factor of CFRP, burr height of titanium alloy, thrust force, torque, surface roughness, roundness and hole diameter of CFRP and titanium alloy. Experimental trial 13 with a combination of speed of 30 m/min, feed of 0.025 mm/rev was chosen as an ideal machining parameter in drilling CFRP/Ti-6Al-4V stacks without any trade-off. Confirmation tests convey that the results agree well with optimal parameters and the decision making in drilling such multimaterial stacks is highly consistent and judicious. In regard to the optimal parameters determined, investigations on tool life were performed and a tool life of 20 min for 0.10 mm flank wear land was observed.

Pembangunan Pangkalan Data Daya Pemotongan S45C untuk Pemonitoran Status Haus Mata Alat

The process of machining involves the removal of metal from the work material using one or more cutting tool and depending on the type of machine and machining process such as turning, milling, or grinding processes. These are the major machining processes in the manufacturing industry. In this study, a turning process of S45C carbon steel work material was conducted using a carbide cutting tool. Due to its desirable characteristics in term of qualities and affordable for mass production, S45C material is frequently used in the industry to produce automotive components. The focus of this study was to develop a database for monitoring the condition of the cutting edge during the machining operation by referring to the cutting force and the average of flank wear land (VB) at the cutting edge. The machining process was conducted in a dry condition without lubricants or coolants. The machining parameters used were cutting speed, V = 200 m/min, feed rate, f = 0.2 mm/rev, and depth of cut, d = 0.25 mm. The machining condition chosen in this study is similar with the machining condition used in the industry for machining S45C. The machining results found that the tool life was 119 minutes at flank wear, Vb = 0.3 mm. The relationship between cutting force and flank wear has been developed to establish a database based on the 2D I-Kaz coefficient. The 2D I-Kaz coefficient is then used for the purpose of monitoring and predicting the status of the cutting tool condition in the next machining process. The online monitoring of the cutting tool condition is expected to be able to control the quality of the components produced as well as to ensure that only worn-out cutting tool is replaced.

Oxidation and wear behavior of CrAlMoN with varied Mo-content for cutting Ti6Al4V

The cutting of difficult to machine materials such as titanium alloys is challenging for the machining industry. In case of the titanium alloy Ti6Al4V, the properties of the material cause high temperatures, mechanical loads as well as high frequency vibrations at the cutting edge, leading to premature tool failure. The use of uncoated carbide tools is very common for machining of Ti based alloys. However, temperature active, self-lubricating physical vapor deposition (PVD) coatings like CrAlMoN showed promising results to reduce friction and wear during turning of Ti6Al4V. In the present study, self-lubricating (Cr34Al41Mo25)N, (Cr29Al36Mo35)N and (Cr25Al31Mo44)N coatings were investigated on cemented carbide tools. These were deposited by a hybrid process combining direct current Magnetron Sputtering and High Power Pulsed Magnetron Sputtering. Coating morphology, thickness, chemical composition, indentation hardness and modulus at ϑ = 20 °C, ϑ = 200 °C, ϑ = 400 °C and ϑ = 600 °C as well as the oxidation behavior were analyzed. Moreover, wear development after cutting tests using a CNC-lathe was investigated. Independent of Mo-content, all coating variants possessed a dense morphology and a smooth surface topography, as well as a coating adhesion class of HF1 to the cemented carbide substrate in Rockwell indentation tests according to DIN 4856. With an increasing amount of Mo, heat treatment temperature and time, more self-lubricating molybdenum oxides such as MoO3 and Mo4O11 were detected by Raman spectroscopy. Therefore, the coating with the highest amount of Mo possessed the highest amount of molybdenum oxides. After cutting tests, molybdenum oxides were also found on the tool flank face by Raman spectroscopy. The level of flank wear land width decreased with increasing amount of Mo.

Built-up edge formation and flank wear evolution in conventional machining of AZ91 magnesium alloy

Magnesium alloys are largely desirable in numerous industries today because of their intrinsically attractive properties. Low density and high strength coupled with significant biocompatibility are the main advantages. Machining of magnesium alloys is challenging as a result of the persistent chip ignition risk as well as material build-up on the tool due to their softness. Therefore, magnesium alloys’ machinability has not been fully assessed in the available literature. The present work aims to address this aperture by assessing flank wear progression and the prevalence of adhesion-driven built-up edge (BUE) and built-up layer (BUL) in different tool coating materials during the dry short-interval conventional orthogonal turning of AZ91 magnesium alloy. A higher and lower combination of feed rates and cutting speeds were utilized for all tools to compare the possible range of maximum flank wear land width, average flank wear land width, and chip contact length while capturing and assessing said parameters through digital and optical microscopy. The data presented a large prevalence of adhesion wear across all tool coating types which is portrayed by the cyclic behaviour of the flank wear land width plots, which resulted from the repeated accumulation and wear of deposited workpiece material. The TiCN-coated tool presented the least amounts of BUL and BUE throughout both levels of testing, while the TiN-coated tool presented the largest amounts of average flank wear land width due to recurrent aberrative local deposition accumulation and extended streak line depositions. TiN-coated, Al2O3-coated, and uncoated tools presented higher average flank wear land width than the TiCN-coated tool by 8.5%, 3.1%, and 27.2% during level 1 cutting conditions and 84.8%, 21.3%, and 37.2% during level 2 cutting conditions. This implies the TiCN coating's increased resistance to elevated cutting temperatures, and in turn, reduced deposition of material through adhesion.

Improved life of circular saws used in primary wood processing

The effects of the Engineered Micro-Geometry (EMG) of the carbide teeth of circular saws on their wear rate and resulting sawing variation for 2-time intervals were studied. The objective was to improve the wear resistance of circular saws used during the primary transformation of wood. The tests were carried out under industrial production conditions with two series of circular saws; 1- with up-sharp tips, and 2- with cutting edges honed to adopt a waterfall geometry. The duration of the tests was 255 min and 645 min. Wood studs were sampled to measure sawing variation. Recession on the rake and clearance faces of the tips as well as the width of the wear land were measured. The wear mechanisms of the cutting edges of both types of saws were studied. Chipping and cracking were the two dominant wear mechanisms observed on the up-sharp tips. Saws with waterfall hone tips showed remarkably reduced chipping and cracking. Wear rate of the latter was notably lower than that of saws with up-sharp tips at both periods of sawing. Between-stud, within-stud, and total sawing variations decreased when saws with modified cutting edges were used.

Tool wear characteristics analysis of cBN cutting tools in high-speed turning of Inconel 718

Nickel-based superalloy is a critical material for turbine engine components in the aerospace application, but the poor machinability and low machining efficiency have further hampered it to be used widely. Cubic boron nitride (cBN), having extreme hardness and chemical inertness, is the potential candidate to process superalloys. In this paper, we systematically investigated the tool wear characteristic of cBN at different cutting speeds in dry turning of Inconel 718 by experiments and FEM simulations. The FEM model with initial flank wear land (VB) was established and validated. Effects of cutting speeds (200–400 m/min) on cBN tool life and wear mechanisms were systematically investigated. Effects of tool flank wear on cBN tool cutting edge temperature field and Inconel 718 machined surface layer stress distribution were analyzed by FEM simulations.

Obrada struganjem kaljenih čelika alatima od PcBN

The paper discusses the results of the experimental investigation of the performance of several grades of PcBN cutting composites in conditions of the interrupted machining of hardened steel. Both BH and BL types of PcBN indexable inserts with additions of Si3N4, TiC, and TiCN were tested, and cutting speed varied to assess the possibility of applying these cutting tools in different conditions. It has been shown that BL PcBN can be utilized for turning with shock loads in case of high cutting speed and low depth of cut (0,2 mm). While in the range of comparatively low cutting speeds BL cutting tools are actually inoperable, and because of microchipping of polycrystalline fragments and brittle destruction of the cutting edge, an increase of the cutting speed to 210 m/min changes wear pattern and formation of the wear land. As well as this, measurement of the form and values of the cutting forces impulses revealed the effect of their peak growth by up to 40%. The danger of shock impulses was analyzed by FEM modeling, and it was demonstrated that during impacts, the maximal value of the third Principal stress exceeds the average level of compressive stresses during continuous cutting by 1.6 times, which can cause damage to the cutting tool. The data on the estimation of tool fracture probability depending on loading conditions are presented, and the possibility of reducing such probability is shown.

Improvement of the Wear Resistance of Circular Saws Used in the First Transformation of Wood through the Utilization of Variable Engineered Micro-Geometry Performed on PVD-Coated WC-Co Tips

Reduced performance of circular saws due to premature chipping of their teeth has been a critical issue in woodcutting industry for many years. This research examined the impact of surface coating and variable engineered micro-geometry of the cutting edges of carbide teeth (tips) on the wear resistance of circular saws used in primary wood processing. CrN/CrCN/DLC, CrN/AlTiN, CrN/CrCN, and CrCN/TiSiCN were deposited on tungsten carbide-cobalt (WC-Co) substrates using the cathodic arc evaporation technique. The CrN/CrCN coating proved to be the one with highest wear resistance and adhesion among those studied. No sign of delamination was observed around the indentation of the CrN/CrCN coating after the adhesion test. Furthermore, no abrasion, delamination or crack was observed on the surface of the CrN/CrCN coating after the three-body abrasion wear test. The results of the dry-sliding wear test revealed that CrN/CrCN coating significantly decreased the wear rate of WC-Co substrates by 74%, 66% and 77% at sliding speeds of 50, 100 and 250 mm/s, respectively. Afterwards, a CrC/CrCN coating was deposited on the teeth of conventional circular saws. Next, the cutting edges of teeth were modified through variable engineered micro-geometry. Tests were conducted at a sawmill with three series of saws: 1-coated and edge-modified, 2-coated and conventional edge geometry, and 3-uncoated and edge-modified. Wood processing was performed during two shifts of 480 min each. The width of the wear land was the criterion used as the wear index. The results of industrial tests showed that saws with edge-modified teeth had significantly less chipping and no breakage at their corners compared to the saw without edge modification (conventional saw). After 480 min of sawing, the wear rate of the coated saw with edge modification decreased by 46% and 16%, compared to the coated saw without edge modification and the uncoated saw with edge-modified teeth, respectively. Those values reached 73 % and 41%, respectively, after 960 min of sawing. The study shows that by optimizing the surface chemistry and the geometry of the cutting edge of WC-Co tips, tool life can be significantly increased therefore reducing downtime due to saw replacement and resharpening, thus significantly increasing productivity in the first transformation of wood.

Study of the Machinability of an Inconel 625 Composite with Added NiTi-TiB2 Fabricated by Direct Laser Deposition

This work studies the process feasibility of milling a metal-matrix composite based on Inconel 625 with added NiTi-TiB2 fabricated by direct laser deposition. The composite is intended for manufacturing turbine blades and it has strength characteristics on par with those of Inconel 625. However, the addition of TiB2 has improved its heat and wear resistance. This material is new, and its machinability has not been studied. The new composite was milled with end mill cutters, and recommendations were worked out on the cutting speed, feed per tooth, cutter flank angle, as well as depth and width of milling. The wear of cutter teeth flank was more intense. After the flank wear land on the back surface of a tooth had reached 0.11–0.15 mm, there was a sharp increase in the forces applied which was followed by brittle fracture of the tooth. Milling at a speed of 25 m/min ensured 28 min of stable operation. However, afterwards the critical wear value of 0.11 mm was quickly approached at a cutting speed of 50 m/min, and critical wear followed after 14 min. Dependencies of the cutting forces vs. time for all the selected cutting speeds and throughout the entire testing time period have a tendency to increase, which indicates the influence of cutter wear on the cutting forces. It was found that the durability of the cutters increases with an increase in the milling width and a decrease in the milling depth.

NEW GENERATION NANO-CBN CUTTING TOOL FOR INCREASING SUSTAINABILITY OF HARD TURNING PROCESS

In this paper, the effect of minimum quantity lubrication (MQL) on tool wear in the hard turning of 100Cr6 ball bearing steel has been investigated and the results are compared to those obtained through dry and wet lubrication methods. The tools used in the study include CBN and nano-CBN tools. The nano-CBN tool is a new generation of CBN tools manufactured based on nanotechnology. No research has been conducted on the impact of this tool on machining processes. The ratio of NCBN tool flank wear land to the CBN tool flank wear land in dry, wet and MQL methods were 0.18, 0.23 and 0.28, respectively. The wear of CBN tool in turning with MQL was 2.8 times greater than the wear of nano-CBN tool in dry machining. In turning with nano-CBN tool, the height of the tool flank wear with MQL was reduced by 22% and 7% concerning wet and dry methods, respectively, while these values were 51% and 24%, respectively, for the CBN tool. The CBN tool wear depends on the lubrication method but the wear of the nano-CBN tool is almost independent of the lubrication method.

Simulation-based design of flank face modification for the milling of Ti-6Al-4V and Inconel 718

The milling of titanium and nickel-based alloys leads to high tool wear due to the high thermomechanical load on the tool. By modifying the flank face on end mills, it is possible to limit the increase in the width of flank wear land, thus increasing tool life, component quality and increasing the allowable productivity of the tools. The flank face modification is characterized by the width and depth of the undercut and the rounding in the undercut of the modification. Through a simulation-based approach, a method is created to design the flank face modification in a load-optimized way and thus to use the full potential in the respective application cases.

Raman spectroscopic investigation of the wear effect on the titanium carbonitride/aluminum oxide/titanium nitride coated cutting tool

In this study, micro-Raman spectroscopy technique in combination with multivariate statistical analysis was carried out to investigate the worn surfaces and metallurgical changes in the wear land of chemical vapor deposition—applied titanium carbonitride/aluminum oxide/titanium nitride-coated cutting inserts. To understand the wear process, detailed scanning electron microscopy analysis was also performed. The structural change at the molecular level of the coating due to the wear of the cutting-edge layers was investigated. Tool life was determined at 0.5 mm flank wear of the cutting tool. Thirty-four Raman spectra recorded from the different points of the worn parts of nine cutting inserts were investigated in comparison with the seven spectra of the different points of three unused cutting inserts. The principal component analysis followed by linear discriminant analysis performed on 41 Raman spectral data, clearly separated the samples as worn and unworn cutting inserts, and showed the wear effects. The comparison of the mean Raman spectrum of worn and unworn (unused) cutting inserts showed that the intensities of the aluminum oxide and titanium nitride bands were decreased, whereas the titanium carbide band at 672 cm−1 was increased, as a result of the wear effect. Moreover, the relative intensity of disordered carbon (D band) band to the graphitic sp2 bonded carbon (G band) band was found to increase, due to wear.

Tool Wear and Milling Characteristics for Hybrid Additive Manufacturing Combining Laser Powder Bed Fusion and In Situ High-Speed Milling.

We report on milling and tool wear characteristics of hybrid additive manufacturing comprising laser powder bed fusion and in situ high-speed milling, a particular process in which the cutter mills inside the powder bed without any cooling lubricant being applicable. Flank wear is found to be the dominant wear characteristic with its temporal evolution over utilization period revealing the typical s-shaped dependence. The flank wear land width is measured by microscopy and correlated to the achievable surface roughness of milled 3D-printed parts, showing that for flank wear levels up to 100 m a superior surface roughness below 3 m is accessible for hybrid additive manufacturing. Further, based on this correlation recommended tool, life scenarios can be deduced. In addition, by optimizing the finishing tool start position and the number of afore-built layers, the milling process is improved with respect to the maximum millable angle for undercut surfaces of 3D-printed parts to 30° for the roughing process and to 40° for the entire machining process including finishing.

On deformation characterisation of machined surfaces and machining-induced white layers in a milled titanium alloy

Machining-induced white layers and severely deformed layers are undesirable surface integrity features which can be formed when machining high-strength aerospace alloys. An orthogonal milling process has been designed and performed to assess the impact of cutting speeds, tool wear, cutting edge radius and climb vs conventional milling on white layer formation and plastic strain distribution. The plastic deformation in the machined surface associated with the formation of white layers in Ti-6Al-4V has been quantified using micro-grids of different length scales printed using the electron beam lithography technique. It was found that white layers formed via the severe plastic deformation mechanism, at equivalent plastic strain values in excess of 1.2 and in regions of the cutting arc with the instantaneous chip thickness of less than the cutting-edge radius and ploughing and rubbing being the dominant mechanisms. The results indicated that the magnitude of the measured strains and the depth of plastically deformed material was greater at lower cutting speeds, during climb milling and when machining with a larger cutting edge radius and tool flank wear land.

Wear and failure mechanisms of SiAlON ceramic tools during high-speed turning of nickel-based superalloys

Nickel-based superalloys have become one of the most promising and potential materials in gas turbine engine components contributing to aerospace industry due to their outstanding mechanical properties (high ductility, high temperate strength, etc.). However, the poor machinability (lower thermal conductivity, high work hardening, etc.) and low machining efficiency of nickel-based superalloys have further hampered it to be widely applied in the potential aerospace applications. In this work, we systematically investigated the effects of various cutting speeds (i.e. 100–400 m/min) on tool wear and failure mechanisms of the SiAlON ceramic tools in the dry cutting of nickel-based superalloys by performing high-speed turning experiments. The tool life and wear evolution with the cutting distance at various cutting speeds were studied; the response relationship of tool flank wear, cutting speed, and cutting distance was visually presented. The optimal cutting speed range could be 200 m/min∼300 m/min in our cutting conditions considering the tool life and the response relationship. Further, tool wear and failure mechanisms are demonstrated to be the adhesion, catastrophic fracture, and microcracks at flank wear land; and the micro-chipping is observed at rake face at a low cutting speed of 100 m/min. Additionally, at a higher cutting speed of 400 m/min, the wear and failure mechanisms are severe adhesion, cutting edge micro-chipping, microcracks, but none of catastrophic fracture failure. This disparity can be attributed to the different alternating dominant effects in strain hardening and thermal softening mechanisms behind the machining process.

Wear behavior of tool flank in the side milling of Ti6Al4V: An analytical model and experimental validation

Due to the poor machinability of Ti6Al4V material, the cutting tool can easily suffer flank wear during the process of high-speed side milling, which reduces the tool life as well as the surface integrity of workpiece. Further, an effective method for predicting the flank wear of end mill during side milling of Ti6Al4V is lacking in the existing literature, which makes it difficult to improve the productivity of the overall process. To this end, in this study, a flank wear prediction model is constructed based on three main mechanisms: abrasive wear, adhesive wear, and diffusive wear. Subsequently, a normal stress model and temperature field model of wear land on the flank of end mill are established. Finally, these two models are incorporated in the flank wear model to obtain the variation rate of wear land width, which is regarded as a criterion to evaluate the reliability of the proposed flank wear prediction model of side mill. The prediction results are found to be in excellent agreement with the experimental results, which verifies the high prediction accuracy of the proposed model. Overall, this model can serve as a useful theoretical basis for the rational selection of tool geometry and cutting parameters.

FE analysis of the effects of process representations on the prediction of residual stresses and chip morphology in the down-milling of Ti6Al4V

Abstract In part II of these two-part papers, the effects of four FEM representations of the milling process on the prediction of chip morphology and residual stresses (RS) are investigated. Part II focuses on the milling of conventional uncut chip thickness h with finite cutting edge radius and flank wear, while part I of these two-part papers has reported on the results in the case of milling small uncut chip thickness in the micrometre range with finite cutting edge radius. Two geometric models of the flank-wear land composed of flat and curved wear land are proposed and assessed. The four process representations are: i) orthogonal cutting with flat wear land and with the mean uncut chip thickness h ¯; ii) orthogonal cutting with flat wear land and with variable h, which characterises the down-milling process and which is imposed on a flat surface of the final workpiece; iii) modelling the true kinematics of the down milling process with flat wear land and iv) modelling the true kinematics of the down milling process with curved wear land. They are designated as Cte-h, Var-h, True-h and True-h*. The effectiveness of these representations is assessed when milling Ti6Al4V with a flank-wear land of VB = 200µm.