Evaluation on Effectiveness of CVD and PVD Coated Tools during Dry Machining of Incoloy 825

With wide applications of nickel-based superalloys in strategic fields, it has become increasingly necessary to evaluate the performance of different advanced cutting tools for machining such alloys. With a view to recommend a suitable cutting tool, the present work investigated various machinability characteristics of Incoloy 825 using an uncoated tool, chemical vapor deposition (CVD) of a bilayer of TiCN/Al₂O₃, and physical vapor deposition (PVD) of alternate layers of TiAlN/TiN-coated tools under varying machining conditions. The influence of cutting speed (51, 84, and 124 m/min) as well as feed (0.08, 0.14, and 0.2 mm/rev) was comparatively evaluated on surface roughness, cutting temperature, cutting force, coefficient of friction, chip thickness, and tool wear using different cutting tools. Although the CVD-coated tool was not useful in decreasing surface roughness and temperature, a significant reduction in cutting force and tool wear could be achieved with the same coated tool under a high cutting speed of 124 m/min. On the other hand, the PVD-coated tool outperformed the other tools in terms of machinability characteristics. This might be attributed to the excellent antifriction and antisticking property of TiN and good toughness due to the multilayer configuration in combination with a thermally resistant TiAlN phase. Adhesion, abrasion, edge chipping, and nose wear were the prominent wear mechanisms of the uncoated tool, followed by the CVD-coated tool. However, remarkable resistance to such wear was evident with the PVD TiAlN/TiN multilayer-coated tool.     

Evaluation of the performance of coated carbide tools in face milling TC6 alloy under dry condition

Titanium and its alloys are well known as the typical different-to-cut materials because of their low thermal conductivity, high chemical reactivity, and low modulus of elasticity. During machining of titanium alloy, advanced high-speed, high-efficiency processing technologies are adopted to improve the production efficiency and reduce the production costs. The main goal of this work is to compare the performance of physical vapor deposition (PVD)-coated (TiN/TiAlN) and chemical vapor deposition (CVD)-coated (TiN/Al₂O₃/TiCN) carbide inserts in face milling TC6 alloy. To this end, the present paper reviewed the main works on the application of PVD- and CVD-coated tools in machining titanium alloys and the material performance of TC6 alloy, especially the machinability in machining process. Several tool life tests and tool wear experiments were carried out on a milling center with a five-axis spindle drive. Cutting forces were measured with a Kistler dynamometer. The failure modes and chip morphology were observed. Surface roughness and tool wear evolution were determined. The wear mechanism was discussed to compare the performance of PVD and CVD-coated tools. The main conclusions of this work were that the cutting tools made with PVD coating (TiN/TiAlN) had the excellent tooling quality and the main wear mechanisms were spalling and adhesion. PVD-TiN/TiAlN insert was more suitable to milling TC6 alloy than CVD-TiN/Al₂O₃/TiCN insert.     

Wear mechanisms of WC coated and uncoated tools in finish turning of Inconel 718

This paper presents the results of an experimental investigation on the wear mechanisms of uncoated tungsten carbide (WC) and coated tools (single-layer (TiAlN) PVD, and triple-layer (TiCN/Al₂O₃/TiN) CVD) in oblique finish turning of Inconel 718. Tool wear rate and wear mechanisms were evaluated for cutting speeds, 50<V<100 m/min, and feed rates, 0.075<f<0.125 mm/rev, at a constant depth of cut of 0.25 mm. It was concluded that abrasive and adhesive wear were the most dominant wear mechanisms, controlling the deterioration and final failure of the WC tools. While the triple layer CVD coated tools exhibited the highest wear resistance at high cutting speeds and low feeds, uncoated tools outperformed the single and multi-layer coated tools in the low range of cutting speeds and intermediate feeds. The cutting tool with single-layer PVD coating outperformed the other tools at the medium cutting speed.     

High-Speed Machining of Malleable Cast Iron by Various Cutting Tools Coated by Physical Vapor Deposition

The coating material of a tool directly affects the efficiency and cost of machining malleable cast iron.However,the machining adaptability of various coating materials to malleable cast iron has been insufficiently researched.In this paper,turning tests were conducted on cemented carbide tools with different coatings(a thick TiN/TiAlN coating,a thin TiN/TiAlN coating,and a nanocomposite(nc)TiAlSiN coating).All coatings were applied by physical vapor deposi-tion.In a comparative study of chip morphology,cutting force,cutting temperature,specific cutting energy,tool wear,and surface roughness,this study analyzed the cutting characteristics of the tools coated with various materials,and established the relationship between the cutting parameters and machining objectives.The results showed that in malleable cast iron machining,the coating material significantly affects the cutting performance of the tool.Among the three tools,the nc-TiAlSiN-coated carbide tool achieved the minimum cutting force,the lowest cutting tempera-ture,least tool wear,longest tool life,and best surface quality.Moreover,in comparisons between cemented-carbide and compacted-graphite cast iron machined under the same conditions,the wear mechanism of the coated tools was found to depend on the cast iron being machined.Therefore,the performance requirements of a tool depend on multiple factors,and selecting an appropriately coated tool for a particular cast iron material is essential.     

Statistical model to determine surface roughness when milling hastelloy C-22HS

The aim of this study is to develop the surface roughness prediction models, with the aid of statistical methods, for hastelloy C-22HS when machined by PVD and CVD coated carbide cutting tools under various cutting conditions. These prediction models were then compared with the results obtained experimentally. By using response surface method (RSM), first order models were developed with 95 % confidence level. The surface roughness models were developed in terms of cutting speed, feed rate and axial depth using RSM as a tool of design of experiment. In general, the results obtained from the mathematical models were in good agreement with those obtained from the machining experiments. It was found that the feed rate, cutting speed and axial depth played a major role in determining the surface roughness. On the other hand, the surface roughness increases with a reduction in cutting speed. PVD coated cutting tool performs better than CVD when machining hastelloy C-22HS. It was observed that most of the chips from the PVD cutting tool were in the form of discontinuous chip while CVD cutting tool produced continuous chips.     

Performance of PVD Coated Carbide Inserts When Machining a Nimonic (C-263) Alloy at High Speed Conditions

Physicals Vapor Deposition (PVD) coated carbide inserts were used to machine a nickel-base, C-263, superalloy under severe cutting conditions. Test results show that the TiN/TiCN/TiN coated, inserts with positive, honed and chamfered edges (Tool A) outperformed similar tools with double positive edges and no edge protection (Tool B) in terms of tool life as well as lower flank wear rate when machining under roughing conditions. The double positive edges of Tool B inserts are more susceptible to chipping action due to reduced tool-chip and tool-workpiece contact lengths/areas and associated increase in applied stresses at the cutting edge during machining. Increase in cutting conditions and variation of the cutting edge geometry did not increase the surface roughness value due to the elastic recovery of the C-263 alloy. Prolonged machining causes appreciable increase in the feed force due to the rapid work hardening of the nimonic alloy as well as the formation of hard burrs during machining     

Investigation of the performance of carbide cutting tools with hard coatings in hard milling based on the response surface methodology

Machining of hard materials has become a great challenge for several decades. One of the problems in this machining process is early tool wear, and this affects the machinability of hard materials. In order to increase machinability, cutting tools are widely coated with nanostructured physical vapor deposition hard coatings. The main characteristics of such advanced hard coatings are high microhardness and toughness as well as good adhesion to the substrate. In this paper, the influence of hard coatings (nanolayer AlTiN/TiN, multilayer nanocomposite TiAlSiN/TiSiN/TiAlN, and commercially available TiN/TiAlN) and cutting parameters (cutting speed, feed rate, and depth of cut) on cutting forces and surface roughness were investigated during face milling of AISI O2 cold work tool steel (～61 HRC). The experiments were conducted based on 3¹³ factorial design by response surface methodology, and response surface equations of cutting forces and surface roughness were obtained. In addition, the cutting forces obtained with the coated and uncoated tools were compared. The results showed that the interaction of coating type and depth of cut affects surface roughness. The hard coating type has no significant effect on cutting forces, while the cutting force F _z is approximately two times higher in the case of uncoated tool.     

不同涂层刀具切削淬硬H13钢加工性能研究

为了研究不同涂层刀具切削淬硬H13钢的切削性能,进行了多层Ti化合物涂层、TiAlN涂层以及MTTiCN厚Al_2O_3TiN涂层材料刀具车削加工淬硬H13钢试验,分析了不同的涂层材料刀具与切削力、切削温度、涂层刀具磨损以及刀具寿命的关系。研究得出:多层Ti化合物涂层刀具受到三个方向的力都大于其它两种涂层的刀具,而且切削温度最高;用TiAlN涂层刀具切削时温度最低;切削过程中三种刀具后刀面磨损程度不同,发现多层Ti化合物涂层刀具磨损最为严重,寿命最短;MT-TiCN厚Al_2O_3Ti N涂层材料刀具比多层Ti化合物涂层刀具寿命长30%;TiAlN涂层刀具的切削寿命最长比多层Ti化合物涂层刀具寿命长45%。     

Performance evaluation of PVD TIALN coated carbide tools vis-à-vis uncoated carbide tool in turning of titanium alloy (Ti-6Al-4V) by simultaneous minimization of cutting energy,dimensional deviation and tool wear

Titanium alloys are difficult-to-machine materials because of their poor machinability characteristics. Machining and machining performance evaluation for such materials is still a challenge. Individual machining performance indices like cutting forces, cutting energy and tool wear lead to ambiguous understanding. In this work, a Cumulative Performance Index (CPI) is defined which amalgamates non-dimensional forms of specific cutting energy, back force and average principal flank wear in turning. The CPI focuses upon simultaneous minimization of specific cutting energy, dimensional deviation and average principal flank wear. The defined index is then used to evaluate performance of five commercially available physical vapor deposited (PVD) TiAlN coated tungsten carbide/cobalt inserts vis-à-vis uncoated tungsten carbide/cobalt insert in turning of Ti-6Al-4V. Cutting forces were monitored during turning and tool wear was measured after turning experiments. The results showed that the performance of coated inserts was either comparable or poor than uncoated insert; and in no case, coated inserts performed better than uncoated insert. Although commercial recommendations are in place to use PVD coated inserts for enhanced machinability of titanium alloys, the use of coated inserts is not justified keeping in view the energy spent in coating and insignificant improvement in performance.     

Wear behaviors of single-layer and multi-layer coated carbide inserts in high speed machining of hardened AISI 4340 steel

Flank wear progression and wear mechanisms of uncoated, coated with PVD applied single-layer TiAlN, and CVD applied multi-layer MT-TiCN/Al₂O₃/TiN cemented carbide inserts were analyzed during dry turning of hardened AISI 4340 steel (35 HRC). Experimental observations indicate that by applying a coating to the uncoated insert the limiting cutting speed increase from 62 to 200 m/min, which further extends up-to 300–350 m/min when using multi-layer coating scheme. Relatively lower wear rate seen when using single-layer TiAlN coated inserts. However, after removal of the thin layer of coating the wear rate increase rapidly, subsequently dominates the wear rate of multi-layer coated inserts. Cutting forces; especially axial and radial components have also shown the similar behavior and increase rapidly when the tool failure occurs. Flank wear, crater wear and catastrophic failure are the dominant forms of tool wear. Digital microscope and SEM images coupled with elemental analysis (EDAX) have been taken at various stages of tool life for understanding the wear mechanisms.     

Effects of Coating Materials on the Machinability of a Nickel Base,C-263, Alloy

PVD coated (TiN/TiCN/TiN, TiAIN and TiZrN) and uncoated carbide tools were used to machine a nickel base, C-263, alloy at high-speed conditions. The test results show that the multiple TiN/TiCN/TiN coated inserts gave the best overall performance in terms of tool life when machining at cutting speeds up to 68 m min and at depths of cut of 0.635 mm, 1.25 mm and 2.54 mm. All the tool grades tested gave fairly uniform surface roughness (Ra) values, below the rejection criterion, at lower speed conditions. The TiZrN coated inserts gave the lowest component forces when machining at lower cutting speed conditions while the TiA/N coated inserts gave the lowest component forces when machining at a higher speed of 68 m min^?1 and depth of cut of 1.25 mm. This tool performance can generally be attributed to the difference in their ability to provide effective lubrication at the cutting zone, thermal conductivity of the coating materials as well as the cutting conditions employed. The uncoated carbide tools generally encountered more severe crater wear, chipping/fracture of the cutting edges as well as pronounced notching during machining. This is due to their inability to provide effective lubrication at the cutting zone, thus impeding the gliding motion of the chips along the rake and flank faces respectively, thus accelerating flank wear. Analysis of the worn tool edges revealed adhesion of a compact “fin-shaped” structure of hardened burrs with saw-tooth like edges. This generally alters the initial geometry of the cutting edge, consequently resulting to poor surface finish with prolonged machining.     

A comparative study on performance of multilayer coated and uncoated carbide inserts when turning AISI D2 steel under dry environment

The present work deals with a comparative study on flank wear, surface roughness, tool life, volume of chip removal and economical feasibility in turning high carbon high chromium AISI D2 steel with multilayer MTCVD coated [TiN/TiCN/Al₂O₃/TiN] and uncoated carbide inserts under dry cutting environment. Higher micro hardness of TiN coated carbide samples (1880 HV) compared to uncoated carbide (1430 HV) is observed and depicts better resistance against abrasion. The low erosion rate was observed in TiN coated insert compared to uncoated carbide. The tool life of TiN coated insert is found to be approximately 30 times higher than the uncoated carbide insert under similar cutting conditions and produced lower surface roughness compared to uncoated carbide insert. The dominant wear mechanism was found to be abrasion and progression of wear was steady using multilayer TiN coated carbide insert. The developed regression model shows high determination coefficient i.e. R² = 0.977 for flank wear and 0.94 for surface roughness and accurately explains the relationship between the responses and the independent variable. The machining cost per part for uncoated carbide insert is found to be 10.5 times higher than the multilayer TiN coated carbide inserts. This indicates 90.5% cost savings using multilayer TiN coated inserts by the adoption of a cutting speed of 200 m/min coupled with a tool feed rate of 0.21 mm/rev and depth of cut of 0.4 mm. Thus, TiN coated carbide tools are capable of reducing machining costs and performs better than uncoated carbide inserts in machining D2 steel.     

Optimization of surface roughness and tool wear in hard turning of austempered ductile iron (grade 3) using Taguchi method

In this work, the cutting parameters are optimized in hard turning of ADI using carbide inserts based on Taguchi method. The cutting insert CVD coated with AL₂O₃/MT TICN. Experiments have been carried out in dry condition using L₁₈ orthogonal array. The cutting parameters selected for machining are cutting speed, feed rate and depth of cut with each three levels, nose radius in two levels maintaining other cutting parameters constant. The ANOVA and signal to noise ratio are used to optimize the cutting parameters. The cutting speed is the most dominant factor affecting the surface roughness and tool wear. In optimum cutting condition, the confirmation tests are carried out. The optimum cutting condition results are predicted using signal to noise ratio and regression analysis. The predicted and experimental values for surface roughness and tool wear adhere closer to 9.27% and 1.05% of deviations respectively.     

The effect of cutting parameters and cutting tools on machining performance of carbon graphite material

Abstract

The present study focuses on the effects of cutting speed, feed rate and cutting tool material on the machining performance of carbon graphite material. Polycrystalline Diamond (PCD) cutting tools are used in machining experiments and its performance is compared with the tungsten carbide (WC) and Cubic Boron Nitride (CBN) tools. Machining performance criteria such as flank and nose wear and resulting surface topography and roughness of machined parts were studied. This study illustrates that feed rate and cutting tool material play a dominant role in the progressive wear of the cutting tool. The highest feed rate and cutting speed profoundly reduce the tool wear progression. The surface roughness and topography of specimens are remarkably influenced from the tool wear. Major differences are found in the wear mechanisms of PCD and WC and CBN cutting tools.     

The Effect of Coolant Concentration on the Machinability of Nickel-Base, Nimonic C-263, Alloy

This paper investigates the effect of coolant concentration on tool performance when machining nickel-base, C-263, alloy with triple coated (TiN/TiCN/TiN) carbide insert at various (3–9%) coolant concentrations and under different cutting speed conditions. Tool life, tool-failure modes, wear rates, component forces and surface finish generated during machining were recorded, analyzed and used to formulate mechanisms responsible for tool wear at the cutting conditions investigated. Analysis of the recorded data shows that tool performance during machining is dependent on coolant concentration. 6% coolant concentration gave the best overall performance as effective combination of cooling and lubrication functions were achieved during machining. Increasing coolant concentration to 9% reduced tool performance due to a reduction of the tool-chip contact length area and the consequent increase in compressive stresses at the tool-chip and tool-workpiece interfaces. This action often leads to pronounced chipping of the tool cutting edge during machining. Friction coefficient between the workpiece material and substrate increases once the coating layer(s) is broken as a result of the direct contact between the tool substrate and the work material. This action increases mechanical wear of the tool, which in turn leads to a significant increase in the cutting force with negligible effect on the feed forces during machining.     

An experimental analysis and measurement of process performances in machining of nimonic C-263 super alloy

Nimonic C-263 alloy is extensively used in the fields of aerospace, gas turbine blades, power generators and heat exchangers because of its unique properties. However, the machining of this alloy is difficult due to low thermal conductivity and work hardening characteristics. This paper presents the experimental investigation and analysis of the machining parameters while turning the nimonic C-263 alloy, using whisker reinforced ceramic inserts. The experiments were designed using Taguchi’s experimental design. The parameters considered for the experiments are cutting speed, feed rate and depth of cut. Process performance indicators, viz., the cutting force, tool wear and surface finish were measured. An empirical model has been created for predicting the cutting force, flank wear and surface roughness through response surface methodology (RSM). The desirability function approach has been used for multi response optimization. The influence of the different parameters and their interactions on the cutting force, flank wear and surface roughness are also studied in detail and presented in this study. Based on the cutting force, flank wear and surface roughness, optimized machining conditions were observed in the region of 210 m/min cutting speed and 0.05 mm/rev feed rate and 0.50 mm depth of cut. The results were confirmed by conducting further confirmation tests.     

Analysis of the life of cemented carbide drills with modified surfaces

The performance of cemented carbide cutting tools during machining is influenced not only by the mechanical properties of the coating and substrate but also by the topographies of their surfaces. A tool with good coating and substrate properties but unsuitable topographies may exhibit accelerated wear and, consequently, impaired performance. In this work, drills coated using physical vapor deposition (PVD) were produced with different substrate textures, which in turn generated different coating textures. The surface roughness values of the coated drills were measured together with the residual stress at the interface between substrate and coating. Drilling tests were performed and tool wear was measured during the machining process. Two different tool coatings were studied: TiAlN and TiAlCrSiN. The goal was to study how the characteristics of the substrate and coating (material, surface topography, and residual stress) influence tool life. Tool life experiments were carried out using drilling tests in AISI 1548 steel, which is often used in crankshafts. The primary tool wear mechanism was attrition in all the drills. The main conclusion of this work is that the tool with the lowest roughness and a TiAlCrSiN coating had the best performance in the conditions tested here.     

Some studies on hard turning of AISI 4340 steel using multilayer coated carbide tool

Hard turning with multilayer coated carbide tool has several benefits over grinding process such as, reduction of processing costs, increased productivities and improved material properties. The objective was to establish a correlation between cutting parameters such as cutting speed, feed rate and depth of cut with machining force, power, specific cutting force, tool wear and surface roughness on work piece. In the present study, performance of multilayer hard coatings (TiC/TiCN/Al₂O₃) on cemented carbide substrate using chemical vapor deposition (CVD) for machining of hardened AISI 4340 steel was evaluated. An attempt has been made to analyze the effects of process parameters on machinability aspects using Taguchi technique. Response surface plots are generated for the study of interaction effects of cutting conditions on machinability factors. The correlations were established by multiple linear regression models. The linear regression models were validated using confirmation tests. The analysis of the result revealed that, the optimal combination of low feed rate and low depth of cut with high cutting speed is beneficial for reducing machining force. Higher values of feed rates are necessary to minimize the specific cutting force. The machining power and cutting tool wear increases almost linearly with increase in cutting speed and feed rate. The combination of low feed rate and high cutting speed is necessary for minimizing the surface roughness. Abrasion was the principle wear mechanism observed at all the cutting conditions.     

Process investigation on meso-scale hard milling of ZrO2 by diamond coated tools

This paper investigates the feasible machining of zirconium oxide (ZrO₂) ceramics, in the hard state, via milling by diamond coated miniature tools (from here on briefly indicated as meso-scale hard milling). The workpiece material is a fully sintered yttria stabilized tetragonal zirconia polycrystalline ceramic (Y-TZP). Diamond coated WC mills, 2 mm in diameter, four flutes and large corner radius (0.5 mm) are chosen as cutting tools, and experiments are conducted on a state-of-the-art micro milling machine centre. The influence of cutting parameters, including axial depth of cut (a_p) and feed per tooth (f_z), on the achievable surface quality is studied by means of a one-factor variation experimental design. Further tests are also conducted to monitor the process performance, including surface roughness, tool wear and machining accuracy, over the machining time. Mirror quality surfaces, with average surface roughness Ra below 80 nm, are obtained on the machined samples; the SEM observations of the surface topography reveal a prevailing ductile cutting appearance. Tool wear initiates with delamination of the diamond coating and progresses with the wear of the WC substrate, with significant effect on the cutting process and its performance. Main applications of this research include three dimensional surface micro structuring and superior surface finishing.     

CVD金刚石薄膜涂层刀具精密切削表面质量的研究

CVD金刚石薄膜刀具的表面粗糙度及加工过程中的切削用量是影响加工工件表面质量的关键因素。为改进CVD沉积工艺 ,减小金刚石薄膜表面粗糙度 ,提出了合理控制沉积气压的新工艺方法 ,并通过切削试验研究了不同沉积工艺下制备的CVD薄膜涂层刀具和加工过程中不同切削用量对精密切削表面质量的影响。