Uncoated Inserts Research Articles

Influence of the injection molding thermal boundary conditions on the filling flow of PET

During the filling phase of the injection molding process, the polymer in contact with the wall solidifies, developing the so-called skin layer. Although the no-flow temperature is often exploited in numerical simulations to model the skin layer formation mechanism, there is still an incomplete understanding of what happens for semi-crystalline PET. In fact, for this polymer, the high shear stresses near the cavity wall combined with the thermal gradient at the polymer-mold interface can cause the so-called flow-induced crystallization. This work aims to experimentally investigate the skin layer formation at different injection molding processing conditions. A full-factorial experimental plan was performed using a commercial PET injected into an open-cavity mold. The thermal and mechanical boundary conditions at the polymer-wall interface were varied using insulating coatings and different flow rates, respectively. The mold coatings were applied to different steel substrates to consider the substrate thermal conductivity contribution. Different flow rates were imposed, varying the cavity thickness and the injection speed. The in-line acquisition of the cavity pressure allows for assessing the contributions of the modified boundary conditions to the solidified skin layer formation. The results show that the insulating mold coating changes the thermal boundary conditions, leading to a maximum pressure decrease of 14 %. The cavity pressure vs. filling time curves for the uncoated inserts show an evident derivative discontinuity, suggesting the onset of flow-induced crystallization.

FEM and statistical-based assessment of AISI-4140 dry hard turning using micro-textured insert

AISI-4140 is a hardenable cold work tool steel widely used in metal cutting operations due to its superior strength and heat treatment capacity. During the dry hard turning of AISI-4140 steel, high cutting temperatures are generated in the tool-chip interface due to friction. Micro-textured tools are thought to improve cutting performances in dry hard turning. The motivation is that the more reducing the chip-tool interface area, the more decreasing the friction there. Therefore, the micro-textured tools can be helpful in all metal cutting applications. This study compared the effects of micro-grooved textures at different sections on either coated or uncoated inserts according to the cutting forces and interface temperatures using FEM and Grey Relation Analysis. Experimentally calibrated FEM simulations and a statistical approach have been built. Besides the general positive sense of the micro-textured tools' effects on machining performances, this study revealed a different unexpected nuance for dry hard turning of AISI-4140 with textured tools according to the design of simulations. Where textures grooved on rake face or flank face below nose radius textures, texture sections, or relationship with coatings was found to be independent for the dry hard turning of AISI-4140 in consideration of cutting temperature and resultant cutting force. It was found that the textured tools were not statistically significant contrary to expectation. The textured tools may not be the exact solution for all machining conditions.

Comparative performance evaluation between uncoated and TiAlN + AlCrN coated carbide tools in hard turning of AISI H11 steel

Cutting tools, such as ceramic, cubic boron nitride, and polycrystalline diamond, are normally preferred to machine hardened hot work steel materials which are exclusively demanded in mould and die-making industries. However, such tool materials are very costly. If carbide tools with proper coatings will be used within a particular machining range, comparative tool life can be achieved with lesser cost in hard machining. The present experimental work is based on the comparative assessment among new generation TiAlN + AlCrN coated and traditional uncoated carbide tools concerning tool life, tool flank wear, cutting temperature, cutting force, and surface integrity in dry hard turning of AISI H11 steel. The experiments with 16 trials are performed according to the L16orthogonal array by considering various machining parameters that include cutting speed, depth of cut, and feed. At last, with the measured tool life and as per Gilbert's economic approach, distinctive cost analysis has been implemented to demonstrate the cost-effectiveness of coated carbide tools in hard turning. From the experimental results, a promising machining performance is noticed for TiAlN + AlCrN coated carbide inserts in terms of all machining attributes compared to uncoated carbide inserts due to superior wear resistance, and surface hardness as well as strength of coating material. In summary, the multilayer TiAlN + AlCrN coated carbide tool offers significant cost savings (Rs. 12.82 in Indian currency), with a 9% reduction in production costs in comparison with hard turning via. uncoated insert (Rs. 14).

High-speed face milling of AZ91 Mg alloy: Surface integrity investigations

Magnesium (Mg) alloys are popular in the aerospace and automotive sector owing to their light-weight aspects. Amongst various Mg alloys, AZ91 alloy behaviour under machining has been trending and needs to be completely explored. The selection of optimal machining parameters is an important decision making process to achieve highest quality along with reduced cost and time. In this regard, this article describes experimental investigations to evaluate the performance of face milling operations on the surface characteristics of AZ91 magnesium alloy. The experiments were carried out with uncoated and PVD (Physical Vapour Deposition) coated carbide inserts at three levels of cutting speed (500, 700 and 900 m/min), feed rate (0.1, 0.2 and 0.3 mm/teeth) and depth of cut (0.5, 1.0 and 1.5 mm) under dry machining conditions. Major surface integrity indicators, such as roughness, hardness, residual stresses and microstructure are analysed. Chip morphology is also analysed and the correlation between chips and machined surface roughness is established. Face milling operation significantly improved surface roughness and microhardness of this alloy. Roughness improvement up to 85% (0.067 μm) and hardness improvement up to 33% (91.8 HV) is observed from the use of uncoated carbide inserts. Whereas, from PVD coated inserts, roughness improvement up to 81% (0.083 μm) and hardness improvement up to 60% (111.2 HV) is achieved. A similarity in behaviour between the two types of insert conditions are observed with increase in roughness from feed increase and decrease in hardness from cutting speed increase. Microstructural analysis showed PVD coated insert conditions producing surface with no defects, when compared to the crack observed in the surface from the use of uncoated carbide inserts. Marginally higher compressive residual stresses are detected at the surfaces from use of the uncoated inserts. Overall, due to no surface defect and the significant improvement in hardness and roughness from the PVD coated inserts, they are recommended for use in face milling operation for the cutting conditions investigated in this study.

Super-Hard DLC Coatings as an Alternative to Polycrystalline Diamond for Cutting Tools: Predictive Analysis of Aluminium Alloy Surface Quality

The use of lightweight materials, such as ultra-high-strength aluminium alloys, is in high demand in the automotive and aerospace industries where weight savings are critical. The tool materials used for high-speed cutting of these aluminium alloys are subjected to severe conditions that promote premature failure of cutting tools. The application of polycrystalline diamond (PCD) coatings provides cutting tools with increased mechanical and thermal fatigue resistance and improved tribological performance. Despite these good properties, their high cost remains a major limitation in this sector. Super-hard Diamond-Like Carbon (DLC) coatings offer a technologically and economically feasible alternative to PCD-coated tools for cutting and machining non-ferrous materials. In this paper, the machining performance of coated and un-coated hard metal inserts in the turning of 7075 aluminium alloy has been explored. The surface quality of machined parts, the cutting tool wear resistance and the vibrations generated during turning of un-coated, PCD and super-hard thin DLC coatings on tungsten carbide inserts were compared. The results obtained demonstrate that DLC coatings are a potentially interesting alternative to PCD coatings for machining ultra-high-strength aluminium alloys, where surface component finish is a key factor.

Studying the Effect of un Coated and Multilayer Coated Tools on Cutting Temperature in Turning Operation

The present work studies three variables (cutting velocity, feed rate, and cut depth) on hard turning cutting temperature of uncoated and multilayer-coated carbide (TiN, TiN/TiCN, TiN /Al2O3/ TiCN) inserts are used in AISI 1045 alloy steel. The tool's temperature was measured simultaneously, measuring the temperature of the tool-chip interface using infrared radiation (IR) pyrometer in this investigation. This study investigated the performance of four distinct coated and uncoated PVD and CVD tools during turning operations. Four cutting speeds (56, 88, 112, 141) m/min, four feed rates (0.065, 0.08, 0.16, 0.228) mm/rev., in the experiments, a constant cutting depth of (1) mm was used. The results also show that Coarse cutting tools have a lower tool temperature than uncoated ones. In comparison to uncoated and other coated tools, the three-layer (TiN/ Al2O3/ TiCN) coating is especially effective in a range of (32% to 39%) than uncoated inserts at various cutting velocity and constant feed rates, with varying feed rates and consistent cutting velocity and lower by approximately( 34% to 40%) than uncoated inserts.

Characterizing and Analyzing the Tribological Behaviour of Diamond Coated Tungsten Carbide (WC)

In this research work, the deposition of diamond coating was done on the tungsten carbide (WC) substrate utilizing the the thermal Chemical Vapour Deposition (CVD) technique. The carbon precursor used for growing the diamond on the tungsten carbide (WC) substrate material was sugarcane bagasse. The tribological properties of deposited diamond coating were studied examined in this paper. For characterization of the developed coating, Field Emission Scanning Electron Microscope (FESEM), Raman spectroscopy and X-ray diffraction (XRD), were used to characterize the developed diamond coating on the substrate material. These processes were used to confirm the presence of diamond coating on the substrate. For inspecting the hardness of the developed diamond coated and un coated samples, the tests of micro-hardness were also executed. The values of the Vickers hardness for the un-coated and the diamond coated substrates were found to be 964.95 HV to 1457.48 HV respectively. This depicted a rise of 51% in the hardness of the un-coated WC inserts. As per ASTM G-99 standards tribological behaviour of the developed coated substrate was also the scope of this work using a pin-on-disc tribometer. The tribological tests showed improvement in the wear resistance of the diamond coated WC inserts as there was a decrease in the value of wear by 57.84 %. The value of the coefficient of friction (COF) also found to be decreased by 51.48%. This paper presents a combined study of using tribological tests and morphologic study showing the advantages of coating diamond on the tungsten carbide (WC) substrate.

Tool Wear Effect on Surface Integrity in AISI 1045 Steel Dry Turning

In the present work, the surface integrity and flank wear of uncoated cermet inserts in dry turning of AISI 1045 steel were evaluated. Three-dimensional techniques were used to assess the surface roughness. Previously, finite element analysis was carried out to predict the cutting forces and heat distribution in the chip formation region. Cutting speed and feed were the parameters varied in the experiments. Feed is decisive in the final quality of the turned surface and cutting speed had little influence on this aspect. The surface was significantly damaged with the progression of the insert flank wear. Considering an average flank wear VBB of 0.1 mm, a tool life of 35 min was achieved using a cutting speed of 175 m/min, and of 23 min for a cutting speed of 275 m/min. Abrasive wear was predominant during the experiments. No microstructure defects were observed, as well as crack propagation or accentuated deformations near the machined surface region. Therefore, the dry turning of 1045 steel with cermet inserts route has proven extremely viable from the standpoints of tool life, surface integrity, chip formation, and sustainability.

The Effect of Coatings on Cutting Force in Turning of C45 Steel.

This article focuses on the development of a mathematical model of a cutting force that is applicable for coated and uncoated cutting tool inserts and aims to enable more accurate calculation of the cutting force. Two common PVD coatings, AlTiN and TiAlCrN, were used. Firstly, a mathematical model of the cutting force based on the specific cutting force and cutting area is proposed. This mathematical model considers the cutting speed and coating correction factor as well as the real cutting edge geometry, i.e., it includes both the straight and rounded parts of the cutting edge. For this proposed model, material constants for C45 steel, which was machined with uncoated inserts, were obtained. Before determining an equation for a coating correction factor and implementing it into the model, experimental cutting force data for coated and uncoated inserts were compared using a paired t-test. The result was that the difference between them was statistically significant. Their percentage difference was found to be up to 4%. The correction factor equation that was obtained and implemented into the mathematical model was applied to compare the calculated and experimental data of the coated inserts, also using a paired t-test. The result was that the difference between them was insignificant. Moreover, their percentage difference was found to be up to 0.6%.

Innovative comparison on performance of PCBN tool and uncoated tool in CNC green turning of LDX2101 duplex stainless steel to minimize surface roughness

The goal of this research is to minimize the surface roughness (SR) by comparing Polycrystalline Cubic Boron Nitride (PCBN) tool and uncoated (cemented carbide) tool during CNC turning of LDX 2101 duplex stainless steel. PCBN inserts were used as the experimental group, whereas uncoated inserts were used as the control group in this research. The selected machining factors were speed of cutting, rate of feed and cut depth. The total number of groups were two and the sample size was 27 samples for each group were used for conducting experiments. The obtained mean SR value for PCBN insert is 3.826559 µm and for uncoated insert is 4.066111 µm. The significant difference between the two inserts is 0.01 (p < 0.05). Within the confines of this research, when LDX2101 duplex stainless steel is machined with PCBN insert it gives lower SR and when the same specimen is machined with uncoated insert it gives higher SR.

An investigation on machinability of nitronic 50 in dry environment using uncoated WC-Co tool inserts

A variety of nitrogen strengthened austenitic stainless steels namely Nitronic 50 is a very useful alloy for marine industry finding its application in the form of drive shafts, pump shafts, valve fittings, pressure vessels, fasteners, sucker rods for oil rigs etc. Studies regarding machinability of this alloy is almost nil and hence it demands a proper investigation of the machining characteristics of this alloy. In the current work, turning has been performed on Nitronic 50 under dry environmental condition using uncoated tungsten carbide inserts and responses in the form of magnitude of tool-tip temperature, surface roughness, cutting force and tool wear were studied. Results showed that employment of higher cutting speed (170 m/min) resulted in enhanced cutting forces, rapid tool wear and BUE development while lower cutting speed promoted higher surface roughness. Use of cutting speed at the intermediate level of 130 m/min showed lesser tool wear, acceptable surface roughness and maintained an overall productivity.

Proposal of a combined experimental-simulation methodology for the evaluation of machining temperature in turning processes

Although it is essential to know the cutting temperature in turning operations, it is very complex to measure it by direct procedures because of the contact tool-workpiece is not accessible. In this research, a methodology consisting of a natural thermocouple, built from the contact tool-workpiece, has been validated. For that, it was necessary to measure the temperature of a reference point on the tool rake face and to probe the results by FEM. Three different materials were experimented getting to a good agreement between the real values of the temperature and those obtained by simulation. Particularly, the range of measurement was defined for the Ti-aluminides machining by uncoated WC inserts. In addition, taking into consideration the correlations obtained between the temperatures of the flank contact tool-workpiece and of the tool rake face and the wearing in the flank, the evolution of this last variable would be known.

RETRACTED: Development of multi sensor fusion based DAQ for in-process TCMS: Experimental and empirical analysis

In order to manufacture low-cost, high-quality goods, in-process tool condition monitoring is an essential responsibility in the manufacturing industry. In this study, a multisensor fusion technique was used to build and execute an effective and reliable TCM system in turning operations with coated and uncoated tungsten carbide inserts. In dry turning, an attempt has been made to optimize the turning process parameter and monitor the tool's condition. Acoustic optic emission based sensor i.e., Laser Doppler Vibrometer and FLIR E60 infrared thermal camera are strategically placed near the machining zone. Thermal images and vibration signals are recorded using an appropriate charge amplifier. To extract characteristics from numerous sensor data, a National Instruments data acquisition (NI-DAQ) system is constructed utilizing LabVIEW software. Thermal images are used to gather temperatures from tool-work piece locations. Vibration signals are translated into vibration parameters. These characteristics serve as the foundation for establishing in-process TCMS. Tool wear, vibrational displacements (Disp), and cutting temperature are investigated as a result of varied tool insert materials and process conditions (CT). Utilizing ISO 10816-3, ISO 3685, and ISO-18434-2008 standards, the cutting tool condition was assessed using extracted features from multi sensor fusion techniques. For Ti-6Al-4 V, the displacement of uncoated and coated tools increased by 65.28% and 44.71%, respectively. For AISI 316L flank wear, the uncoated insert effected 41% and the coated insert impacted 24.14%, respectively. While machining Al7075, the relationship of depth of cut and feed rate on flank wear maintains an identical trend. It is discovered that both temperature and displacement have a significant role in the evolution of flank wear, which is examined in depth. This paper recognizes the use of multi-sensor data in tool condition monitoring when rotating with various cutting tool inserts.

PERFORMANCE EVALUATION OF (ALCRN) PVD COATED CBN INSERTS ON MACHINING OF INCONEL 718

This research work focuses on the experimental investigations conducted using uncoated cBN tool and (AlCrN) PVD Coated cBN tool for turning Inconel 718. Two different sets of experiments – one with uncoated cBN and another with coated cBN inserts were conducted considering three different levels of cutting speeds, feed rates and depth of cuts. The performance of the coated cBN over the uncoated inserts were evaluated and it was found that the AlCrN coated cBN inserts can produce 10-12% drop in the cutting force, 15% reduction in the flank wear and 10% reduction in the surface roughness.

Optimizing the Machining performance of CNC tools inserts coated with Diamond like Carbon Coatings under the dry cutting environment

In this research work we have coated WC (tungsten carbide) tool inserts with diamond like carbon coatings. The deposition was done using the thermal Chemical Vapour Deposition (CVD) method. We have used bagasse of sugarcane which is an agriculture waste as a carbon precursor for developing the diamond like carbon coatings. Surface finish, cutting temperature and cutting forces of as-developed diamond like carbon coatings on the WC inserts were examined and analyzed in this research work. For confirming the presence of diamond like carbon coatings on the surface of coated tungsten carbide (WC) tool inserts substrate we have used Raman spectroscopy, X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (Fe-SEM). The increase in the hardness on the developed coated samples were inspected by performing the hardness test on the coated substrates. The average evaluated Vickers Hardness number were found to be 1455.24 HV and 950.65 HV for both coated as well as un-coated samples respectively. This shows 53% rise in the hardness of the un-coated WC inserts.

Comparison between the machinability of different titanium alloys (Ti–6Al–4V and Ti–6Al–7Nb) employing the multi-objective optimization

Titanium and its alloys are amongst the most important metallic materials used by many industries, such as those pertaining to the aerospace, automotive, and biomedical sectors. This is due to the reliability and functionality of titanium components, in addition to their high strength-to-weight ratio and corrosion resistance. Thus, titanium and its alloys are of great importance to the challenging operations of these sectors. The manufacturing of titanium requires great accuracy to ensure that resulting products meet quality requirements, due to its difficult machinability. In this study, the cutting forces and surface roughness of the turning were analysed to compare different titanium alloys, Ti–6Al–4V and Ti–6Al–7Nb, with CVD-coated and uncoated inserts. The effect of control factors on the response variables was measured using ANOVA. Response surface methodology was applied to the creation of a model of responses and to a bi-objective optimization process via the normalized normal constraint method. The Pareto-optimal sets of both alloys were achieved, which may be applied to practical situations to achieve optimal results for these responses. The models and optimization results confirmed the similarity of machinability values between the Ti–6Al–4 V and Ti–6Al–7Nb alloys. The uncoated inserts yielded the best surface roughness and cutting force results when used with both titanium alloys.

Experimental investigations into the influence of AlSi-10Mg soft tool coating on the machinability of Ti6Al4V

ABSTRACT Machinability of Grade 5 titanium alloy, despite its extensive usage in fields of aerospace and biomedical applications, is extremely challenging as a result of various features like its poor thermal conductivity, chemical reactivity, work hardening nature, etc. Although various methodologies and coating techniques have developed over the years, a significant improvement in its machinability characteristics is yet to be achieved. This study is an effort to analyze the effect of AlSi-10 Mg soft coating developed by pre-conditioning technique on tool life and surface integrity characteristics and to compare the observed results with that of the uncoated insert in the dry cutting process. It was seen that AlSi-10 Mg coating developed over the cutting edges helped in minimizing the effects of adhesion and diffusion wear along the tool faces due to its self-lubricating properties and cushioning effect that it provided at the cutting interface, thereby contributing to encouraging results in tool life improvement in contrast to the unprotected uncoated insert. Moreover, favorable chip morphology and better surface finish were generated when machined using AlSi-10 Mg soft coated inserts.

Multi-Response Optimization of cutting parameters in MQL assisted Turning of Haynes 25 alloy with Taguchi based Grey Relational Analysis

Haynes 25 is a cobalt based superalloy gaining its importance in aerospace, heat treatment applications, chemical handling equipment, commercial gas turbine engines, bearing material, etc. This alloy is featured with low thermal conductivity, wear and corrosion resistance, strength with good resistance to oxidation at high temperatures. In the present study, optimization of process parameters in turning Haynes 25 alloy with uncoated and coated carbide tools under the minimum quantity lubrication (MQL) using Taguchi based grey relational analysis (GRA) method is attempted. The influence of cutting parameters and nano-particle concentration on surface roughness, tool wear, cutting and thrust forces are analyzed to improve the alloy machinability. The work also compares the responses obtained with uncoated and coated tool inserts and analyzes the effect of nano-particle concentration. Further, the experimental cutting and thrust forces are computed and validated using FE based DEFORM 3D software. The results obtained through simulation are in good accordance with experimental data within an average relative error of about 12 %.

Effects of dry turning parameters of Incoloy 800H superalloy using Taguchi-based Grey relational analysis and modeling by response surface methodology

Incoloy 800H is an austenitic Fe-Ni-Cr based superalloy and used in many applications due to their high corrosion resistance and creep-strength. However, this alloy is difficult to machine or cut material because of their eminent characteristics such as rapid-work hardening, lesser thermal conductivity and easy to tool-material attraction. Hence, the necessary experimental investigation is required to study and optimize the turning parameters of this alloy. This work presents the investigation of turning parameter effects on the Incoloy 800H superalloy with cryogenically treated cutting tool. The dry turning experiments were conducted based on Taguchi L9 Orthogonal array (OA) with the input parameters of cutting speed, feed rate and depth of cut. The outputs such as material removal rate, surface roughness, cutting force and tool-tip temperature were considered as the responses. The measured output responses were optimized and modeled using Taguchi-based Grey relational analysis (GRA) and response surface methodology (RSM), respectively. The tool flank wear and tool life were examined on coated insert with cryogenically treated, coated insert (without cryogenic treatment) and uncoated insert for comparison. The results revealed that greater amount of tool-wear reduction was observed in the case of coated tool with-cryogenically treated about 47.88%, coated tool without-cryogenically treated about 27.51% when compared with an uncoated tool. Besides, analysis of variance (ANOVA) was performed to find the most significant parameter over the obtained responses. The obtained mathematical model through RSM was agreed with the experimental result. Further, the machined surface topography was examined using White Light Interferometer (WLI).

On the improvement in process performance of ceramic inserts during hard turning in MQL environment

ABSTRACT Hard turning process, frequently used to finish the rotational surfaces of hard steel components, has some major issues like a high tool wear rate coupled with the degradation of surface finish and generation of brittle white layer. Due to this, the process productivity also remains low. In an attempt to improve the cutting tool productivity while machining hardened EN31 steel, uncoated ceramic inserts were used with the Minimum Quantity Lubrication (MQL) environment, which resulted in significant wear reduction on the ceramic inserts along with a better surface finish than that produced with a dry cutting. The most suitable process parameters, to produce an efficient cut, i.e., high process performance on both wear and surface finish fronts, were proposed. The surface integrity produced within the process parameter window identified was compared for both dry and MQL environments. It was confirmed that application of MQL brought about a significant reduction in formation of subsurface white layer both at lower and higher feeds (around 40% and 16.5% respectively) when compared to dry mode cutting. MQL condition enhanced the overall productivity of ceramic inserts with lower flank wear and better surface characteristics even at higher feeds, while at the same time, producing a thinner white layer.