PVD Coated Carbide Inserts Research Articles

Mathematical modeling and optimization of machining parameters in CNC turning process of Inconel 718 using the Taguchi method

To remain competitive, machining processes must be optimized to provide increased productivity and higher quality products. The aim of most efforts in these machining processes is to establish the optimal parameters to obtain the maximum material removal rate with minimum surface roughness which represents two of the main quality responses. This paper focuses on the optimization of process parameters in dry turning of Inconel 718, a nickel-based superalloy with PVD-coated carbide inserts based on single-objective optimization Taguchi technique, desirability function approach combined with response surface methodology (RSM), which is known as the multi-objective Desirability Optimization Methodology (DOM). Taguchi’s orthogonal-array design L9 (33) and ANOVA analysis of variance are used to study the relationship between cutting parameters (cutting speed, feed rate and depth of cut) and the dependent output variables i.e., the arithmetic mean deviation of the profile's surface roughness (Ra) and material removal rate (MRR). A regression analysis was used to develop a mathematical model based on the first-order model to predict the Ra and MRR model. Using multiple regression analysis, first order linear prediction model was obtained to find the correlation between surface roughness and MRR with independent variables. In the range of parameters investigated, the obtained mathematical models accurately represent the response index, and the results of the experiments demonstrate that the feed rate and the depth of cut are the most important factors influencing Ra and MRR, respectively. Finally, confirmatory tests proved that Taguchi's method, desirability function approach combined with linear regression models was successful in optimizing turning parameters for minimum surface roughness and maximum MRR.

Surface integrity investigation and VIKOR optimisation during the milling of aluminium–lithium alloy using uncoated and PVD-coated carbide tools

ABSTRACT In this study, the effect of face milling on the surface integrity of an aluminium–lithium alloy is investigated through an L27 Taguchi design of experiments. Uncoated and PVD-coated carbide inserts are used to investigate the material surface characteristics such as roughness, microhardness, microstructure and residual stresses. Both inserts showed their ability in achieving a better surface finish (Ra ∼ 0.04 µm) than the raw material (Ra ∼ 0.52 µm). Hardness improvement of up to 216.7 HV (uncoated) and 229.3 HV (PVD-coated) from the raw material (180.7 HV) surface is observed. Both inserts showed their ability to generate compressive residual stresses with uncoated inserts producing stresses on the surface. Microstructural changes from milling using both inserts are observed to be minimal. ANOVA showed the effect of process parameters on the surface roughness and microhardness. Furthermore, VIKOR statistical analysis technique is used to identify the optimal conditions for good roughness and microhardness of the alloy.

Analysis of cutting temperature during turning of SS 304 using uncoated and PVD coated carbide inserts

Cutting temperature is one of the most important parameters controlling the tool wear and consequently the life duration and other parameters of the machined surface. Hence, it would be essential to do tool temperature measurements during machining tests. To understand the physical phenomena of temperature generated during cutting processes, especially in the machining of difficult-to-cut materials, the characterization of the temperature field is essential. In the present paper, an attempt is made to determine the tool-chip interface temperature using an experimental approach during the turning of SS 304 material. It is considered to be difficult to cut material due to its properties like low thermal conductivity, and work hardening. The application of tool-work thermocouple method is used for the experimental approach whereas the empirical model is prepared and validated based on experimental results. Cutting tests were carried out on SS 304 work material by using uncoated (K-313 grade) and TiAlN PVD coated (KC 5525) cemented carbide insert at the cutting speed of 140–260 m/min and feed of 0.08–0.20 mm/rev, keeping the depth of cut constant as 1 mm. Experimental observations indicate that temperatures generated during machining are strongly dependent on the cutting speed. The high temperature was observed during turning using TiAlN Coated tools. However, due to the better thermal stability of the coating, the coated tool performs 10–12 % more than the uncoated tool.

HARD TURNING PERFORMANCE EVALUATION USING CVD AND PVD COATED CARBIDE TOOLS: A COMPARATIVE STUDY

This study emphasizes the comparative cutting performance evaluation of CVD- and PVD-coated carbide inserts in hard turning of AISI D2 steel. The cutting factors, namely cutting speed (100[Formula: see text]m/min), tool feed rate (0.08[Formula: see text]mm/rev), and depth of cut 0.2[Formula: see text]mm, have been fixed for the entire study. The comparative study is based on the analysis of the obtained test results of flank wear, tool life, auxiliary flank wear, surface roughness, and surface texture. Both tools are catastrophically failed when tool wear reached limiting flank wear ([Formula: see text][Formula: see text]mm) criteria. SEM and EDS analysis of both the tools (at their end of tool life) are carried. Diffusion followed by adhesion is found to be the prime mechanism at the end of tool life. Based on limiting flank wear criteria, the tool life of CVD and PVD tools was estimated as 65 and 57[Formula: see text]min, respectively, i.e. the tool life of the CVD tool is 14% longer than that of the PVD tool. Considering the limiting criteria of surface roughness ([Formula: see text]m), the tool life of the CVD tool was estimated as 63[Formula: see text]min while for the PVD tool, it was found as 54[Formula: see text]min i.e. about 14.3% higher tool life was found for the CVD tool relative to the PVD tool. The auxiliary flank wear was observed to be lower for the CVD tool relative to the PVD tool. Surface roughness for both the tools increased with cutting time and the relatively larger rough surface was obtained with the PVD tool. The machining cost of one pass of the CVD tool is 2.5% less than that of the PVD tool. However, for mass production, the CVD tool is more efficient than the PVD tool for machining hard D2 steel ([Formula: see text] HRC).

Investigating a novel Ag/ZnO based hybrid nanofluid for sustainable machining of inconel 718 under nanofluid based minimum quantity lubrication

Sustainable machining, with implementation of eco-friendly dry and minimum quantity lubrication (MQL) methods, has gained attraction of researchers and engineers to solve the environmental and health allied issues caused by bulk usage of the conventional cutting fluids. Nanofluids have recently became more obvious choice as a cutting fluid in MQL applications owing to their superior thermo-physical properties. In this work, a novel hybrid nanofluid, consisting of Ag coated ZnO (Ag/ZnO) nanoparticles in ethylene glycol base, has been proposed as cutting fluid for MQL application. Initially, the Ag/ZnO hybrid nanoparticles were synthesized by a chemical precursor method. Then, synthesized nanoparticles were blended in ethylene glycol at several volume concentrations (Φ = 0.05 % to 0.2 %). The nanofluids were characterized for their thermo-physical properties and stability criterion, and then a nanofluid with the best performance was selected for nanofluid based MQL (NFMQL) experiments. The performance of NFMQL was compared with dry, MQL environments during milling of difficult-to-cut Inconel 718 superalloy with PVD coated carbide inserts. Taguchi L9 orthogonal array was incorporated for experimental design to investigate the effect of cutting speed, feed rate and machining environment on the machining performance in terms of the average surface roughness and cutting temperature. Analysis of variance shown that the cutting environment contributed to the average surface roughness and cutting temperature by 24.52 % and 44.74 %, respectively. As compared to dry and MQL condition, the NFMQL improved the surface finish by 23.5 % and 13.07 %, respectively, and reduced the cutting temperature by 15.38 % and 8.56 %, respectively, owing to proposed hybrid nanofluids enhanced lubrication and heat dissipation properties. Furthermore, the field emission scanning electron microscopic (FESEM) images of used cutting tool inserts reveal that the NFMQL condition induces the minimum tool wear as compared with MQL and dry environments. Finally, the multi-response optimization was achieved through the implementation of Taguchi grey relational analysis (TGRA) with the optimum combination of cutting speed of 30 mm/min, feed rate of 0.036 mm/tooth, and NFMQL cutting environment.

A machinability evaluation based on the thermal and mechanical properties of two engine valve steels

Iron-based superalloys are difficult to machine because of their thermal and mechanical properties provided by alloying elements as nickel, chromium, titanium, and aluminum. However, parts made with this kind of material has to be machined during their production processes. In this work, two different automotive engine valve steel grades, VAT 30® and VAT 36®, were compared in terms of machinability, considering cutting power consumption, roughness of the machined surface, and tool life, besides the identification of the main tool wear mechanisms that have led to the end of tool life. The main goal of this work is to understand the difference in these machining outputs based on the thermal and mechanical properties of these two materials. In order to reach this goal, turning tests were held using two different cooling conditions, conventional and high-pressure coolant. Also, two PVD-coated carbide inserts were applied, one with negative rake angle and another neutral. Finally, cutting speed was tested in two levels, providing a full 24 factorial planning. Results show that VAT 30® has shown higher machinability in terms of tool life in almost every condition, although this steel presents higher hardness, mechanical strength, and strain hardening coefficient, besides lower thermal conductivity. However, it also presents lower ductility and abrasiveness, features that retarded abrasion and attrition as tool wear mechanisms, in such a way that tool life could have been lengthened.

Face milling of Inconel 625 via wiper inserts: Evaluation of tool life and workpiece surface integrity

Ni-based superalloy Inconel 625, despite its extensive applications (in aerospace, oil and gas, marine, chemical processing and alike industry) is categorized as difficult-to-cut material due to distinct thermal and physical characteristics. Incidentally, the use of novel multi radii insert (wiper) geometry, that is reported to provide extended machining capabilities for different materials and machining scenarios has not been found to be reported for this alloy. This work employs PVD coated carbide inserts with novel wiper edge geometry for face milling of Inconel 625 under dry cutting conditions. Cutting speed, feed per tooth and axial depth of cut have been taken as input variables and machining performance is evaluated in terms of tool life, tool wear analysis, material removed and surface integrity aspects (namely roughness and microhardness). Taguchi L8 array has been employed for experimentation phase followed by post experimental analysis. It is found that for tool life, axial depth of cut is the most significant factor with contribution of 45.43%. Maximum tool life of 42.8 min was achieved when machining was done employing lower values of feed (0.08 mm/tooth) and axial depth of cut (0.25 mm) with higher value of cutting speed (45 m/min). For the case of surface roughness, feed/tooth is found to be the most contributing factor (PCR 46.25%). Results are found to be correlating well with the cutting temperatures generated during the process. Experiments with minimum axial depth of cuts resulted in lesser temperatures and better output parameters in general. Review of the wear pattern via SEM analysis indicate adhesion, BUE, attrition and chipping to be the main wear mechanism in general except where higher axial depth of cut (0.5 mm) was employed that culminated in fracture. For the conditions where maximum tool life was obtained, a work-hardened layer was observed beneath the machined surface extending up to ∼400 μm depth. An indirect comparison of the results with other literature reported face milling scenarios of Inconel 625 (where other tool types are employed), seems to indicate the effectiveness of wiper inserts employed herein. The results are well explained and supported by the physical phenomenon involved.

Experimental Investigation into Wear and Tool Life of Milling Cutter PVD Coated Carbide Inserts While Armox 500 Steel Hard Milling

Experimental Investigation into Wear and Tool Life of Milling Cutter PVD Coated Carbide Inserts While Armox 500 Steel Hard Milling

Comparative Investigation on Tool Wear during End Milling of AISI H13 Steel with Different Tool Path Strategies

Tool wear prediction plays a significant role in machining industry for proper planning and control machining parameters and optimization of cutting conditions. This paper aims to investigate the effect of tool path strategies that are contour-in and zigzag tool path strategies applied on tool wear during pocket milling process. The experiments were carried out on CNC vertical machining centre by involving PVD coated carbide inserts. Cutting speed, feed rate and depth of cut were set to vary. In an experiment with three factors at three levels, Response Surface Method (RSM) design of experiment with a standard called Central Composite Design (CCD) was employed. Results obtained indicate that tool wear increases significantly at higher range of feed per tooth compared to cutting speed and depth of cut. This result of this experimental work is then proven statistically by developing empirical model. The prediction model for the response variable of tool wear for contour-in strategy developed in this research shows a good agreement with experimental work.

A Comparative study of tool wears in dry turning of Inconel X-750 and Waspaloy

Machining of Nickel based superalloys has posed considerable challenges due to rapid work hardening and low thermal conductivity. The present investigation aims to compare the tool wears in dry turning of Inconel X-750 and Waspaloy by analyzing the variation of flank and nose wears with machining length. The experiments were designed using the following parameters: cutting speed=50 m/min, 75 m/min, 100 m/min; feed rate= 0.05 mm/rev. The depth of cut was kept at a constant value of 0.5 mm. PVD coated carbide inserts were used for the turning operation and tool wear was analyzed using a digital microscope. The wear rate was higher while machining Waspaloy as compared to Inconel X-750 for all experiments.

Content Comparative Investigation on Tool Wear During End Milling of AISI H13 Steel with Different Tool Path Strategies

Tool wear prediction plays a significant role in machining industry for proper planning and control machining parameters and optimization of cutting conditions. This paper aims to investigate the effect of tool path strategies that are contour-in and zigzag tool path strategies applied on tool wear during pocket milling process. The experiments were carried out on CNC vertical machining centre by involving PVD coated carbide inserts. Cutting speed, feed rate and depth of cut were set to vary. In an experiment with three factors at three levels, Response Surface Method (RSM) design of experiment with a standard called Central Composite Design (CCD) was employed. Results obtained indicate that tool wear increases significantly at higher range of feed per tooth compared to cutting speed and depth of cut. This result of this experimental work is then proven statistically by developing empirical model. The prediction model for the response variable of tool wear for contour-in strategy developed in this research shows a good agreement with experimental work.

Tool wear analysis in the machining of hardened steels

The machinability of a material can be assessed using many output parameters of the machining process, tool life being undoubtedly the most common. Tool life depends mainly on the tool wear rate, which in turn is very dependent on the prevailing wear mechanisms. It is therefore very important to study and analyze correctly the possible wear mechanisms on the rake and flank faces of the tool. When machining materials with high hardness, usually over 35 HRC, the difficulties are enormous because of the high cutting forces and heat generated, causing rapid tool wear and short tool life. When the hardness exceeds 45 HRC, the difficulties are even worse because the chips change from continuous to serrated types formed by localized shearing, increasing forces and temperatures even further. To tackle these adversities, ceramic and ultra-hard (CBN) tool materials are normally used, although other materials are also suitable. In interrupted cutting, for example, cemented carbides are frequently used. Wear mechanism analysis in hard machining is thus of particular importance. This article analyzes the tool wear mechanisms that occur in the machining of several hardened steels during continuous and interrupted cutting. All the analyses were performed after the tools have reached the stipulated end of the tool life criteria. Different types of tool material, such as cubic boron nitride, ceramics, and PVD-coated carbide inserts applied in turning and milling operations had their wear mechanisms analyzed. The main goal of this work was not to compare the tool lives of the conditions tried but to provide a greater understanding of tool wear phenomena and thus contribute to the development of tools with improved properties. Most of the worn tools had their wear region analyzed using a scanning electronic microscope (SEM) with the help of energy dispersive spectroscopy (EDS) technique. The wear analysis performed using the pictures taken in the SEM/EDS system was based on the main literature of this field of knowledge.

Manifestations of reduced tool-chip friction during turning of AISI 1045 steel with PVD-coated carbide inserts

Short duration turning tests were performed with uncoated and various PVD-coated straight grade carbide inserts against AISI 1045 steel, without coolant. Cutting forces, built-up edge (BUE) intensity, and characteristics of the chips (length, curl diameter, and colour) were made and related to measurements of friction coefficient obtained from a custom heavy-load, high-temperature tribometer as well as from reported thermal conductivity values obtained from the literature. At lower cutting speeds, where the size of BUE tends to be larger, it is proposed that reductions in cutting forces and BUE intensity observed for certain PVD-coated inserts pertain more to reduced sticking intensity between tool and chip, for which the friction coefficient results from the tribometer are a helpful guide. At higher cutting speeds, hotter temperatures and greater thermal softening of work material at the tool-chip interface seem to be responsible for reductions in cutting force and BUE size, which is linked to the thermal conductivity of the coatings. As well, delamination of certain coatings was observed both during cutting tests as well as tribometer tests, suggesting the potential merit of the tribometer as a method for screening coatings for adequate substrate-adhesion. Investigations of tool wear during longer duration turning tests suggest that tribometer COF results can be predictive of relative tool wear rates among tool candidates, under cutting conditions that give rise to attrition as the dominant wear mechanism.

Experimental Study of Surface Integrity of Al/SiC Particulate Metal–matrix Composites in Hot Machining

Al/SiCp Metal Matrix Composites (MMCs) are the new class of materials and are rapidly replacing conventional materials in various applications industrial and aerospace applications. These materials are generally regarded as extremely difficult to machine, because of the abrasive characteristics of the reinforced particulates. It has poor machinability such as excessive tool wear and fracturing of the reinforcement particles on machined surface. It leaves behind adhered particle fragments, pits and cavities despite superior excellent engineering properties. These characteristics in machining of Al/SiCp MMCs tend to adversely affect the machined surface quality/integrity. Hence, an attempt is made to improve the machinability of Al/SiCp MMCs and surface quality by hot machining. This paper presents the results of an experimental research on hot machining of Al/SiCp MMCs produced by stir casting. PVD coated carbide inserts were used under dry cutting conditions. Experiments were carried out on CNC lathe. Experiments on Al/SiCp 10% composites of two different particle size of Silicon carbide reinforcement i.e. coarse and fine (220 and 600 mesh size respectively) are performed using L16 orthogonal array as per the Taguchi method. The study of Al/SiCp MMCs on the basis of surface integrity was tried out in order to know the machinability. The experimental study showed that feed, depth of cut and preheating temperature have a significant influence on cutting force, feed force, thrust force, surface roughness and micro-hardness variation beneath the machined surface. The micro-hardness is found to be higher near the machined surface layer and decreases with the depth of machined subsurface for all experimental conditions. Qualitative analysis of surface and subsurface damage is analysed using SEM photographs. A SEM photograph reflects the SiC particulates debonding, fracture, feed marks and smeared layer on machined surface. Better values of surface roughness are obtained at 60°C temperature during machining of both Al/SiC/10p/220 (0.776μm) and Al/SiC/10p/600 (0.640μm) MMCs.

Cutting Temperature Behaviours in End Milling of Pocket by Applying Contour-In Tool Path Strategy

Cutting temperature generated during high speed machining operations has been recognized as major factors influence tool performance and workpiece geometry. This paper aims to model the cutting temperature and to investigate cutting temperature behaviours when contour-in tool path strategy applied in high speed end milling process. The experiments were carried out on CNC vertical machining center by involving PVD coated carbide inserts. Cutting speed, feed rate and depth of cut were set to vary. Results obtained indicate that cutting temperature is high in the initial stage of milling and at the corners region or turning points region. Portion of radial width of cut with workpiece in combination with the abrupt change of the milling path direction occur particularly in acute internal corners of a pocket leads to rise of cutting temperature.

Experimental Investigations on Cryogenic Cooling in the Drilling of Titanium Alloy

In this study, a drilling experiment was conducted on titanium ASTM B265 Grade 2 material using PVD coated carbide inserts. Two types of coolants (Wet and LN2) were used. The variables in the experiment were feed rate (f) and cutting speed (Vc). The depth of the drilling was constant. Cutting temperature (T), thrust force (Ft), surface roughness (Ra), and the hole quality (circularity, cylindricity, and perpendicularity) were analyzed. The tool wear and chip morphology were studied. The result of the experiment indicates that there is 6–59% reduction in cutting temperature when LN2 is used, high thrust force values were recorded for LN2 coolant condition, surface roughness (Ra) values were higher for LN2 coolants. Hole quality is not favorable in LN2 coolant supply.

Influence of the cutting edge preparation method on characteristics and performance of PVD coated carbide inserts in hard turning

The use of cemented tungsten carbide inserts in hard machining requires proper coatings and edge micro-geometries. A suitable choice of these factors enables the reduction of cutting forces, the increase of tool life and the improvement of workpiece surface quality. However, the effects of the edge preparation method and coating process on the substrate properties influence the performance of the insert during cutting. In this context, the influence of two different edge preparation methods (plunge-face grinding and brushing) on the performance of TiAlN-coated cemented tungsten carbide inserts during hard turning is investigated. In general, higher values of surface roughness (Rz≅0.3μm) and edge chipping (Rk≅4.5μm) were observed for brushed inserts in comparison to the ground tools (Rz≅0.2μm, Rk≅3.7μm). Moreover, higher compressive residual stresses are induced by brushing in comparison to grinding (≅500MPa against≅400MPa). In turning tests, cutting forces for the ground inserts are approximately 10% higher than for the brushed inserts. However, higher wear values are better related to lower compressive residual stresses in the substrate than to higher cutting forces.

Assessment of Factors Influencing Tool Wear on the Machining of Nimonic C-263 Alloy with PVD Coated Carbide Inserts

Nimonic C-263 alloy is extensively used in the field of like aerospace, power generators and heat exchangers due to its higher thermal properties. In this work, an attempt has been made to investigate the effect of the cutting parameters (cutting speed, feed rate & depth of cut) on tool wear (flank wear) in the machining of this alloy with a PVD coated carbide insert. The experiments were conducted using Taguchi’s experimental design. A second order response surface model has been established between the cutting parameters and flank wear using response surface methodology. The predicted optimal value of flank wear for coated carbide is 0.190mm. The results are confirmed by conducting verification experiments.

Experimental Investigation on Tool Wear when End-Milling Inconel 718 with Coated Carbide Inserts

In this paper, some experiments were conducted to investigate tool wear when end-milling Inconel 718 with the TiAlN-TiN PVD coated carbide inserts. The worn tools were examined thoroughly under scanning electron microscope (SEM) with Energy Dispersive X-ray Spectroscopy and 3D digital microscope to expatiate tool wear morphologies and relevant mechanisms. The flank wear was uniformity in finishing milling process, and the average flank wear were selected as the criterion to study the effects of cutting parameters (cutting speed, feed per tooth, radial depth of cut, and axial depth of cut) on tool wear. Finally, the optimal combination of the cutting parameters for the desired tool life is obtained.

Tool Wear of PVD Coated Carbide Inserts in High Speed Turning Inconel 718

TiAlN/TiN multilayer PVD coated carbide is one of the dominant tool materials for the turning applications of Inconel 718 due to its high hardness, high wear resistance, and high thermal stability. The results of a thorough investigation on TiAlN/TiN multilayer PVD coated carbide inserts were presented for turning Inconel 718. The tool wear of the PVD coated carbide inserts were tested and analyzed at different cutting speeds from 50m/min to 90m/min and different feed rates from 0.1mm/r to 0.4mm/r. The wear patterns and wear mechanisms of PVD coated carbide were analyzed. Results show that the dominant wear patterns are rake face wear, flank wear, micro-chipping, coating delamination, notch wear, built-up edge and breakage. The main wear mechanisms are adhesion, diffusion, abrasive and oxidation.