Uncoated Tools Research Articles

A new model to predict the tool life in turning of titanium aluminides

Several tool wear models for machining operations have been reported in the literature. However, most of them are capable of modeling only a part of the wear curve, designed for quasi-linear curves or need to be fitted by means of differential equations. In this research, a new analytical easy-to-use wear model is proposed, taking into consideration the geometry of the cutting insert and the influence of the cutting speed and the tool-workpiece contact stress. In addition, the effect of the critical machining time, relative to the tool degradation, has also been introduced. The wear model describes completely the wear curve, from the initial rapid wear stage to the thermal-activated wear rate acceleration. The constants and parameters of the equation are determined by cutting experiments from the cutting forces and flank wear registers under a variety of technological parameters. This model has been validated for turning process on Ti48Al2Cr2Nb aluminide with uncoated carbide tool under different cutting conditions, varying the cutting speed and the geometrical position of the tool. It has been demonstrated its suitability to predict tool life, according to a defined wear criterion.

Estimation of temperature in the cutting area during orthogonal turning of grade 2 titanium

The authors introduce an experimental-analytical method for determining the average temperature values in the PSZ (primary shear zone) and the SSZ (secondary shear zone) during orthogonal turning of grade 2 titanium with a use of an uncoated carbide tool with a positive rake angle and a flat rake face. The presented method is based on an algorithm in which the values of shear stress in the PSZ and the SSZ are calculated by means of the Johnson–Cook constitutive equation and Oxley’s model of cutting mechanics. Average temperature values in the PSZ and the SSZ are determined by iteratively finding the minimum difference between the calculated stress values. As its inputs, the algorithm uses the values of the feed and the tangential cutting force components, the value of chip flow velocity on the rake face, and the constants of the Johnson–Cook constitutive equation. The model was validated with a use of empirical data collected during the experiments. The test rig consisted of a KNUTH Masterturn 400 precision lathe equipped with a dynamometer, a high-speed camera, and a thermal imaging camera.

Effect of increased mechanical strength on the machinability of graphite cast irons in face milling

Due to the low cost and high vibration damping capacity, gray cast irons are commonly used in machine tool bases, in addition to applications with noise restrictions, such as engine blocks, housings, and brakes. The matrix’s graphite, sulfides, and ferrite/pearlite ratio are some of the most important parameters governing the machinability of the gray cast irons. This work aims to evaluate the machinability of high-resistance gray cast irons of the FC 300 grade, in two versions, with the addition of molybdenum (FC 300 (Mo)) and with refined graphite and addition of molybdenum (FC 300 (Mo+RG)), for use in cylinder heads and engines blocks, compared to materials that have been used for this purpose, gray cast iron FC 250 and the compacted graphite cast iron FV 450. The materials were characterized according to the cementite interlayer spacing and microhardness of the perlite matrix, the number of eutectic cells, and the distribution of manganese sulfide inclusions, with those characterizations being correlated with the machinability results. The face milling process was chosen for the tests with uncoated cemented carbide tools without cutting fluids; the cutting speed and feed rate varied in addition to the type of cast iron. Analysis of tool life, wear mechanisms, and machined surfaces’ quality (Ra roughness parameter) were the output variables considered. Using harder materials such as FC 300 (Mo) or FC 300 (Mo+RG) for the engine would bring benefits such as increased durability, reduced weight, and improved efficiency, but it has a cost in machining. These harder materials have a shorter tool life compared to the commonly used gray cast iron FC 250, but the difference in performance is less pronounced under more extreme cutting conditions, such as high cutting speed and feed rate. When analyzing the surface roughness, FC 250 produced a smoother surface at low cutting speeds but performed worse than FC 300 (Mo) and FC 300 (Mo+RG) at higher cutting speeds.

Influence of advanced coated tools on surface integrity characteristics of Nimonic C263

Advanced coated tool and cooling techniques were used for trial on Ni-based superalloy Nimonic C 263 to improve surface integrity, such as a white layer, grain refinement, and surface defect. Toolmaker microscope, Field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD) system were employed to characterize the tool after machining, machined surface, and subsurface alteration. A possible cause of tool failure at high cutting speed and feed was severe plastic deformation and chipping of the cutting edge and nose, abrasive nose and flank wear, and the formation of a built-up layer (BUL). The white layer, surface defect, and grain refinement are always found less on machined surfaces with the PVD-coated tool under dry machining than with an uncoated tool under wet machining at a high rate. TiN/TiAlN multilayer coated WC tool can be suggested for good machinability and surface integrity in a sustainable, eco-friendly way to the industry for machining Nimonic C-263. MQL and flood mode cooling are also preferred at a cutting speed near 84 m/minute and a feed rate of 0.14 mm/rev.

Investigation of the Properties of Multilayer Nanostructured Coating Based on the (Ti,Y,Al)N System with High Content of Yttrium

The studies are focused on the properties of the multilayer composite coating based on the (Ti,Y,Al)N system with high content of yttrium (about 40 at.%) of yttrium (Y). The hardness and elastic modulus were defined, and the resistance to fracture was studied during the scratch testing. Two cubic solid solutions (fcc phases), including c-(Ti,Y,Al)N and c-(Y,Ti,Al)N, are formed in the coating. The investigation of the wear resistance of the (Ti,Y,Al)N-coated tools during the turning of steel in comparison with the wear resistance of the tools with the based on the (Ti,Cr,Al)N system coating and the uncoated tools found a noticeable increase (by 250%–270%) in rake wear resistance. Active oxidation processes are observed in the (Ti,Y,Al)N coating during wear. It can be assumed that yttrium oxide is predominantly formed with a possible insignificant formation of titanium and aluminum oxides. At the same time, complete oxidation of c-(Y,Ti,Al)N nanolayers is not observed. Some hypotheses explaining the rather high performance of a coating with a high yttrium content are considered.

Influence of Cutting Speed during the Turning of Inconel 718 on Oxidation Wear Pattern on the Zr-ZrN-(Zr,Mo,Al)N Composite Nanostructured Coating

The properties and oxidation wear patterns in the composite nanostructured coating of Zr-ZrN-(Zr,Mo,Al)N were studied during the turning of Inconel 718 alloy at the cutting speeds of vc = 125 and 200 m/min. The hardness of the coating, its elastic modulus, and critical fracture load during the scratch testing were determined. The study focused on the tribological properties of the Zr-ZrN-(Zr,Mo,Al)N coating at temperatures of 400–900 °C paired with an insert made of Inconel 718, which exhibited a certain advantage over the reference coatings of Zr-ZrN and Ti-TiN-(Ti,Cr,Al)N of similar thickness. The coating of Zr-ZrN-(Zr,Mo,Al)N provided for the longest tool life at the cutting speed of vc = 125 m/min (the tool life was four times longer in comparison with that of the uncoated tool and 15% longer in comparison with that of the Ti-TiN-(Ti,Cr,Al)N-coated tool) and at the cutting speed of vc = 200 m/min (the tool life was 2.5 times longer in comparison with that of the uncoated tool and 75% longer in comparison with that of the Ti-TiN-(Ti,Cr,Al)N-coated tool). While at the cutting speed of vc = 125 m/min, the surface coating layers exhibit only partial oxidation of the external layers (to a depth not exceeding 250 nm), with mostly preserved cubic nitride phases, and then the cutting speed of vc = 200 m/min leads to almost complete oxidation (to the depth of at least 500 nm), however, with a partially preserved nanolayered structure of the coating.

Determination of the friction coefficients between uncoated WC-Co tools and L-PBF and wrought Ti-6Al-4V alloys for micro-milling simulations

This study aims to determine the friction coefficient in the function of the sliding velocity between uncoated WC-Co tools and Ti-6Al-4V alloys processed by Laser Powder Bed Fusion (L-PBF) and the wrought one. A series of tribological tests combined with numerical simulations were performed under different sliding velocities and a constant contact pressure using spherical WC-Co pins and wrought and L-PBF Ti-6Al-4V. The obtained friction coefficients in the function of the sliding velocity were then integrated into two micro-milling models to predict the cutting forces in machining of wrought and L-PBF Ti-6Al-4V, respectively.

Development and Status of Tool Coating

With the development of modern machining technology, the use of cutting fluid is removed in theprocess of cutting workpiece, and it is gradually developing towards the direction of green, so that thecutting becomes more satisfied with the machining accuracy of the workpiece and improves themachining efficiency of the workpiece. Although the dry cutting without cutting fluid has been adoptedbythe majority of machine tools, there are many shortcomings that need to be improved. For example, drycutting will aggravate the friction between the tool and the workpiece surface, reduce the tool life andincrease the cutting cost. Therefore, the development of tool coating has become the mainstreamdirection of today's society. By designing experiments, changing the process and coating on thecuttingtools, we can compare domestic coated tools, uncoated tools and experimental preparation of coatings totest which cu tting tools are more suitable for today's harsh cutting conditions. This paper mainlyintroduces the development of coatings in recent years from two aspects of hard coating and superhardcoating.

Performance analysis of novel TiN coated and uncoated carbide tool in CNC wet turning of Super Duplex Stainless steel to minimize tool wear

Performance analysis of novel TiN coated and uncoated carbide tool in CNC wet turning of Super Duplex Stainless steel to minimize tool wear

Performance study of uncoated and AlTiN-coated tungsten carbide tools in micromilling of Ti6Al4V using nano-MQL

Performance study of uncoated and AlTiN-coated tungsten carbide tools in micromilling of Ti6Al4V using nano-MQL

Influences of tribological and mechanical properties of (Ti /Al)N and diamond like carbon coated tungsten carbide tool on machining and dynamic stability in micro milling of Ti6Al4V

In this article, the performances of thin-film PVD coated tools of similar chemical compositions such as TiAlN and TiN, and dissimilar chemical compositions like diamond like carbon (DLC) with respect to Ti6Al4V workpiece have been intended to analyze. The suitability of thin film coated tools for micro milling of Ti6Al4V is assessed by comparing machining responses such as cutting force, surface roughness, burr height, tool wear and dynamic stability. These are correlated with tribological properties of the coating and tool materials, which has not been reported yet for micro milling of Ti6Al4V. The value of coefficient of friction (COF) for coated and uncoated WC surfaces has been evaluated by considering Ti6Al4V as a counter surface. Among all coated and uncoated tools, the DLC coated surface gives the lowest value of COF which is 0.14. Adhesion is found as the major cause of higher COF of TiAlN coated surface (0.47) and TiN coated surface (0.44) as compared to the uncoated tungsten carbide (WC) surface (0.41). Among all the tools, the DLC coated tool manifested the best machining performance reducing percentage of diameter reduction, burr height, surface roughness, and cutting force by 30 %, 35 %, 17.5 % and 22.2 %, respectively, as compared to the uncoated WC Surface. Further, the critical stability limits of the uncoated and coated tools have been evaluated analytically through the dynamic stability analysis. The DLC coated tool exhibited the best dynamic stability performance enhancing the critical stability limit by 17.04 % compared to the uncoated tool.

Surface Roughness in High Speed Turning of Alloy Steel M303 Using Carbide Tools in Dry Cutting Condition

M303 is a corrosion resistant martensitic chromium steel offering excellent toughness, corrosion, and wear resistance, characterized by improved machinability and polish ability. It is widely utilized in industries such as in mould and die making, machinery and automotive equipment, bearing housing, and tooling. Recently, this material has also been used in locomotive bearing housing. This paper presents surface roughness achieved in the turning process of M303 in dry cutting condition using coated and uncoated carbide tools. The turning parameters included a high cutting speed regime (260-340 m/min) and feed rate at 0.1-0.2 mm/rev, suitable for the finishing process. The experiment was conducted according to the Taguchi method (L18). Average surface roughness (R<sub>a</sub>) was in the range of 0.395-1.356 μm, in which a mirror finish was achieved for certain cutting conditions that could eliminate the grinding process. Results of surface roughness were analysed using Analysis of Variance (ANOVA) for linear models and revealed that feed rate is the main significant factor contributing to surface roughness, followed by type of cutting tool, and cutting speed. These findings show that good and dition, therefore it is recommended to eliminate the acceptable R<sub>a</sub> values for M303 turning are obtained in dry con use of flooding condition as normally practiced in the industry.

Multi-Objective Optimization of Process Parameters during Micro-Milling of Nickel-Based Alloy Inconel 718 Using Taguchi-Grey Relation Integrated Approach

This research investigates the machinability of Inconel 718 under conventional machining speeds using three different tool coatings in comparison with uncoated tool during milling operation. Cutting speed, feed rate and depth of cut were selected as variable machining parameters to analyze output responses including surface roughness, burr formation and tool wear. It was found that uncoated and AlTiN coated tools resulted in lower tool wear than nACo and TiSiN coated tools. On the other hand, TiSiN coated tools resulted in highest surface roughness and burr formation. Among the three machining parameters, feed was identified as the most influential parameter affecting burr formation. Grey relational analysis identified the most optimal experimental run with a speed of 14 m/min, feed of 1 μm/tooth, and depth of cut of 70 μm using an AlTiN coated tool. ANOVA of the regression model identified the tool coating parameter as most effective, with a contribution ratio of 41.64%, whereas cutting speed and depth of cut were found to have contribution ratios of 18.82% and 8.10%, respectively. Experimental run at response surface optimized conditions resulted in reduced surface roughness and tool wear by 18% and 20%, respectively.

Study of Wear, Stress and Vibration Characteristics of Silicon Carbide Tool Inserts and Nano Multi-Layered Titanium Nitride-Coated Cutting Tool Inserts in Turning of SS304 Steels.

Cutting tool characterization plays a crucial role in understanding the behavior of machining operations. The selection of a suitable cutting material, the operating conditions for the work piece, is necessary to yield good cutting-tool life. Several pieces of research have been carried out in cutting-tool characteristics for turning operation. Only a few pieces of research have focused on correlating the vibrations and stress with wear characteristics. This research article deals with stress induced in silicon carbide tool inserts and coated tool inserts while machining SS304 steel. Since this material is much less resistant to corrosion and oxidation it is widely used in engineering applications such as cryogenics, the food industry and liquid contact surfaces. Moreover, these materials have much lower magnetic permeability so they are used as nonmagnetic engineering components which are very hard. This article focuses on the machining of SS304 by carbide tool inserts and then, the cutting forces were observed with a tool dynamometer. Using observed cutting forces, the induced stress in the lathe tool insert was determined by FEA investigation. This research also formulates an idea to predict the tool wear due to vibration. Apparently, the worn-out tool vibrates more than new tools. Using the results, the relation between stress, strain and feed rate, depth of cut and speed was found and mathematically modeled using MINI TAB. It was observed that carbide tool inserts with coating withstand better than uncoated tools while machining SS304. The results were anticipated and correlation between the machining parameters furnished the prediction of tool life and obtaining the best machining outcomes by using coated tool inserts.

Performance of Si-doped TiAlxN supernitride coated carbide tool during dry machining of Inconel 718 superalloy

Conventional high speed dry machining using uncoated carbide tool is challenging for machining of difficult-to-cut aerospace superalloy Inconel 718. On the other hand, coolant-assisted machining may not be a feasible solution always due to issues related to operator's safety and environmental protection. Use of harder tool materials is also not wise always in purview of production economics. Application of coated carbide tools is therefore being given importance since last several decades. In this context, present work examines performance of newly developed Si-doped TiAlxN supernitride nanocomposite (HSN2) coated carbide tool during dry machining of Inconel 718. Tool performance is assessed in perspectives of a few machinability criteria such as cutting force, tool-tip temperature and width of tool flank wear. Different tool wear mechanisms are explained in correlation with properties of tool substrate and coating material. The work also includes study of chip's micro-morphology. It is experienced that HSN2 coated tool outperforms uncoated WC-Co tool. As compared to uncoated tool, lower cutting force, reduced tool-tip temperature and shorter width of tool flank wear are obtained during application of HSN2 coated tool. HSN2 coated tool produces chips with better underside surface morphology and lower microhardness than its uncoated counterpart.HSN2 coated tool experiences ~17 % reduced temperature at the tool-tip when compared to uncoated counterpart, operated at cutting velocity = 47 m/min. As compared to uncoated carbide tool, HSN2 coated tool causes ~56 %, ~ 57 % and ~43 % reduced tangential cutting force, feed force and radial force respectively, at cutting velocity = 134 m/min. Usage of HSN2 coated tool causes lower flank wear (~ 15 % reduced) than that of uncoated counterpart, operated at the highest cutting speed (134 m/min). Chips evolved by using HSN2 coated tool corresponds to ~9 % reduced microhardness (within shear band) than that obtained using uncoated tool at cutting velocity = 103 m/min.

Prediction of cutting forces using MRA, GMDH and ANN techniques in micro end milling of titanium alloy

Micro End Milling is an specific procedure for manufacturing biomedical, automotive, naval, aerospace and mining parts especially for super alloys. Surface finish is the necessity output parameter after machining these alloys in the said applications. The study of cutting forces is mandatory to know the required surface finish to be generated on the work material. The influence of machining parameters can be investigated by experimental and predicted results that are very useful for the practitioner engineers inorder to evaluate. In this manuscript, experimental investigation of cutting forces was done and a comparison of the modelling methods - multiple regression analysis (MRA), Group method data handling (GMDH) and Artificial Neural Network (ANN) were presented. In the manuscript, the impact of input factors in machining of Ti-6Al-4 V (Grade-5) titanium alloy using uncoated tungsten carbide tools was studied on cutting forces. From the experimental interpretations, it is found that while increasing machining input parameters cutting forces on workpiece subsequently increases. After the adherences of experiments, experimental values are in good agreement with the accuracy of neural network prediction.

Sustainable Machining of Mg-9Al-1.4Zn Foam Used for Temporary Biomedical Implant Using Cryogenic Cooling.

In this study, the drilling performance of biodegradable grade Mg-9Al-1.4Zn alloy reinforced with hollow thin-walled Al2O3 microspheres is inspected under different coolant environments such as dry, Almag® mineral oil, and liquid nitrogen. Drilling experiments were carried out using titanium aluminum nitride PVD coated and uncoated K10 tools on varying volume fractions of magnesium syntactic foams (5%, 10%, and 15%) reinforced with hollow Al2O3 microspheres. Test results showed a 30–60% higher thrust force generated with liquid nitrogen drilling in comparison to dry and oil-based drilling while cutting higher volume fraction foams. Higher microsphere volume fractions of syntactic foam recorded higher machining forces, which is roughly a 200% increase as the volume fraction raised to 15%. The performance of TiAlN PVD tool coating is reflected through a reduction in thrust forces by 20% during cryogenic drilling. Scanning electron microscope (SEM) investigation of cryogenic-machined bore surfaces showed minimal drilling-induced surface defects compared to dry and Almag® mineral oil conditions. A three-dimensional, thermo-mechanical finite element-based model for drilling Mg-9Al-1.4Zn syntactic foam using AdvantEdgeTM is developed for different sustainable lubrication conditions. Surface finish (Ra) showed a 45–55% improvement during cryogenic drilling of 15% syntactic foams with minimized subsurface damages compared to dry and wet cutting conditions. The higher the volume fraction, the higher the surface roughness (Ra) and thrust force under cryogenic machining.

Self-lubricating CrAlMoN high performance tool coatings for machining of TiAl6V4

TiAl6V4 allows significant performance improvements in industrial applications. However, the machining is a considerable challenge due to low thermal conductivity, Young’s modulus and strong adhesion tendency. This leads to high thermal and mechanical loads on the cutting edge resulting in early tool failure. Today, uncoated cemented carbide tools are commonly used. However, temperature active physical vapor deposition (PVD) coatings like CrAlVN and CrAlMoN provide a promising approach to increase tool life. For this, the coating’s ability to form lubricating oxide phases is vital. In the present study, CrAlVN and CrAlMoN coatings were investigated to determine the more suitable version for increasing the economic efficiency of machining TiAl6V4. The coatings were deposited by hybrid direct current magnetron sputtering/high power pulsed magnetron sputtering (dcMS/HPPMS) processes. Morphology, thickness, chemical composition, indentation hardness, indentation modulus and oxide phase composition were analyzed. Moreover, friction and wear behavior of the coated tools were determined using a pin on disc (PoD) tribometer at various temperatures. Additionally, tool life and deformation behavior were analyzed after turning TiAl6V4. The CrAlVN and CrAlMoN coatings show a dense morphology and a smooth surface topography. Both variants have a good adhesion to the cemented carbide tools. For increased temperatures, the tribological analyses showed a reduction in the coefficient of friction. In case of CrAlMoN coated samples, a friction reduction compared to CrAlVN was observed at lower temperatures. Due to this, an increased tool life was achieved for CrAlMoN coated cutting inserts during turning of TiAl6V4.

Study on the working performance of CrAlCN coated and uncoated carbide twist drill

A drilling test was carried out for a 6 mm diameter carbide twist drill with CrAlCN coating and an uncoated carbide twist drill to grasp the effect of CrAlCN coating on the tool performance. Drilling and machining tests on ASTM1045 steel workpieces using CrAlCN coated and uncoated tools. Observe the pattern of variation of surface morphology and roughness of holes with the number of drilled holes using SEM and optical microscope. The effect of CrAlCN coating on carbide twist drill on drilling quality was analyzed by comparing the wear, surface roughness and chip shape of twist drill at different periods and parameters of drilling. The study concluded that using CrAlCN coated tools improved the wear resistance of the drill and significantly reduced BUE. Compared to the uncoated bit, the diameter of the drill decreased to 5.91 mm for the coated tool and 5.79 mm for the uncoated tool after 80 holes. The roughness of the coated bit was 3.324 µm at a feed rate of 0.12 mm/r and several holes of 40, which was significantly lower than that of the uncoated bit. Chip analysis showed that the coated tool maintained well-broken and tightly spiraled chips. In contrast, the uncoated tool produces tightly spiraled chips and short ribbon chips at a feed rate of 0.18 mm/rev, and the edges of the chips can appear significantly serrated. The research results improve the understanding of the drilling wear mechanism, provide new technical means to improve the analysis of working tool performance and provide a reference basis for the design of new coating tools.

Characterization and Evaluation of Engineered Coating Techniques for Different Cutting Tools-Review.

Coatings are now frequently used on cutting tool inserts in the metal production sector due to their better wear resistance and heat barrier effect. Protective hard coatings with a thickness of a few micrometers are created on cutting tools using physical or chemical vapor deposition (PVD, CVD) to increase their application performance. Different coating materials are utilized for a wide range of cutting applications, generally in bi-or multilayer stacks, and typically belong to the material classes of nitrides, carbides, carbonitrides, borides, boronitrides, or oxides. The current study examines typical hard coatings deposited by PVD and CVD in the corresponding material classes. The present state of research is reviewed, and pioneering work on this subject as well as recent results leading to the construction of complete “synthesis–structure–property–application performance” correlations of the different coatings are examined. When compared to uncoated tools, tool coatings prevent direct contact between the workpiece and the tool substrate, altering cutting temperature and machining performance. The purpose of this paper is to examine the effect of cutting-zone temperatures on multilayer coating characteristics during the metal-cutting process. Simplified summary and comparisons of various coating types on cutting tools based on distinct deposition procedures. Furthermore, existing and prospective issues for the hard coating community are discussed.