Dry machining characteristics of coated inserts and multi response optimization through DEAR-Taguchi method

The primary intent of the proposed research work is to investigate the effectiveness of the titanium aluminium nitride/tungsten carbide-carbide coated insert during dry turning structural stainless steel. The aim of the study is to simultaneously optimise machining variables like spindle speed, depth of cut and feed for several responses like flank wear, material removal rate and surface roughness. Titanium aluminium nitride/tungsten carbide-carbide is coated on the surface of carbide tool by cathodic arc evaporation method. The characterization studies have been conducted to ensure the existence of coating material. Micro hardness of coated and pure inserts was tested, which confirms that titanium aluminium nitride/tungsten carbide-carbide coated insert possesses 17.43 % augmented hardness over pure inserts. The machining was performed by adopting Taguchi experimental design. A multi-response optimization approach was applied in this study that included ranking methodology based on data development analysis and Taguchi's design. The performance index for multiple responses was measured and mathematically analysed for their effect on processing parameters. The combination of parameter such as spindle speed: 2000 min⁻¹; cutting depth: 0.45 mm and feed rate: 0.16 mm rev⁻¹ was experimental as optimal machining parameters.     

用立方氮化硼刀具对硬质合金材料进行延性超精密加工

对单相晶体结构和硬质合金的粘合特性的理论分析表明，对其进行延性超精密加工是可行的，并在普通加工中心上通过对切削力的监控，用立方氮化硼刀具实现了对硬质合金材料的延性超精密加工．研究结果显示，在用不同刀具进行的切削中，刀具的磨损都非常小；在对硬质合金的延性超精密加工中获得了纳米级表面粗糙度的平滑表面和层状切屑。     

Characterization and Performance of AlTiN,AlTiCrN, TiN/TiAlN PVD Coated Carbide Tools While Turning SS 304

This study presents the physical, mechanical properties and dry turning performance of AlTiN, AlTiCrN, and TiN/TiAlN coatings produced on K-grade tungsten carbide insert by advanced physical vapor deposition technique. Scanning electron microscopy, microhardness tester, and scratch tester were used to examine surface morphology, coating thickness, microstructure, microhardness, and adhesion of coating. The performance in terms of cutting force and temperature of AlTiN, AlTiCrN, and TiN/TiAlN coated inserts was evaluated while dry turning of SS 304 steel. SS 304 is considered as “difficult-to-cut” material due to its exotic properties. The experiments were conducted at cutting speed of 140, 200, 260, and 320 m/min. Feed and depth of cut were kept constant and their values were 0.20 mm/rev and 1 mm, respectively. Experimental observations depicts that AlTiCrN coated insert demonstrated better performance because of its good adhesion and high oxidation resistance followed by TiN/TiAlN coated insert. TiN/TiAlN coated insert exhibited higher cutting temperature than AlTiCrN and AlTiN coated inserts. The findings of the study should also provide economic machining solution in case of dry turning of SS 304 stainless steel.     

Effect of Machining Parameters on Surface Integrity in High Speed Milling of Super Alloy GH4169/Inconel 718

Control of surface integrity is a vital consideration in the machining of components subjected to fatigue loading, for example, critical components of aerospace engines. In this research, three important aspects of surface integrity of a machined part—surface roughness, micro-hardness, and residual stresses—were analyzed for their variations with the cutting parameters. Finish milling of super alloy GH4169/Inconel 718 was carried out using coated cemented carbide and whisker-reinforced coated ceramic inserts. All of the three machining parameters—cutting speed, feed rate, and depth of cut—were found to have a substantial effect on the surface integrity of the finished part. Although different cutting parameters gave different effects for the two types of cutting inserts, overall better surface integrity was obtained at minimum cutting feed and medium cutting speed and depth of cut value. Moreover, carbide inserts produced better surface integrity of the finished part, whereas ceramic inserts generated very high surface tensile stresses and poor surface finish due to back striking of the adhered metal chips.     

Application of grey relational analysis based on Taguchi method for optimizing machining parameters in hard turning of high chrome cast iron

High chrome white cast iron is particularly preferred in the production of machine parts requiring high wear resistance. Although the amount of chrome in these materials provides high wear and corrosion resistances, it makes their machinability difficult. This study presents an application of the grey relational analysis based on the Taguchi method in order to optimize chrome ratio, cutting speed, feed rate, and cutting depth for the resultant cutting force (F_R) and surface roughness (R_a) when hard turning high chrome cast iron with a cubic boron nitride (CBN) insert. The effect levels of machining parameters on F_R and R_a were examined by an analysis of variance (ANOVA). A grey relational grade (GRG) was calculated to simultaneously minimize F_R and R_a. The ANOVA results based on GRG indicated that the feed rate, followed by the cutting depth, was the main parameter and contributed to responses. Optimal levels of parameters were found when the chrome ratio, cutting speed, feed rate, and cutting depth were 12%, 100 m/min, 0.05 mm/r, and 0.1 mm, respectively, based on the multiresponse optimization results obtained by considering the maximum signal to noise (S/N) ratio of GRG. Confirmation results were verified by calculating the confidence level within the interval width.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0231-z     

Mathematical models to predict surface finish in fine turning of steel. Part II

This paper outlines further experimental development of mathematical models for predicting RMS surface finish in fine turning operation using TiC coated and cemented tungsten carbide throwaway cutting tools. The five independent variables included are: cutting speed, feed, depth of cut, time of cut of tool, nose radius. Using these five variables at different levels an experimental approach, predictive models for tungsten carbide and titanium coated tungsten carbide tools were developed. A sixth variable, 'the type of cutting tool,' was used to develop a single model for both the TiC coated and cemented carbide cutting tools. AIS1 4140 steel was used as workpiece specimen in the experimental work. Stepwise regression analysis was used in developing the models.     

An experimental analysis of effective high speed turning of superalloy Inconel 718

Superalloy, Inconel 718 is widely used in the sophisticated applications due to its unique properties. However, machining of such superior material is difficult and costly due its peculiar characteristics. The present article is an attempt to suggest Taguchi optimization technique to study the machinability of Inconel 718 with respect to cutting force, cutting temperature, and tool life in high speed turning of Inconel 718 using cemented tungsten carbide (K20) cutting tool. Therefore, the objective of this work is divided into two phases: (i) to demonstrate a correlation between cutting speed, feed, and depth of cut with respect to cutting force, cutting temperature, and tool life in a process control of high speed turning of Inconel 718 in order to identify the optimum combination of cutting parameters; (ii) to show the effect of high speed cutting parameters on the tool wear mechanism and chip analysis. These correlations were obtained by multiple linear regressions. The confirmation tests were carried out to make a comparison between the experimental results and mathematical models proposed. The proposed models agree well with the experimental results.     

Machinability study of silicon carbide and cenosphere reinforced Al7075 composite using three different tool materials

This research conducted a machinability study on Al7075 composite reinforced with nano-sized (100 nm) silicon carbide and cenosphere (industrial waste) particulates with 1.8 % weight. These composites were fabricated utilizing an ultrasonically assisted stir-casting setup and scanning electron microscope investigation was conducted to evaluate the dispersion properties of the reinforcement in the matrix phase. During the study, the effect of variation of feed rate, cutting speed and depth of cut on cutting forces and tool tip temperature has been studied. A total of 253 experiments were conducted using three different tool inserts polycrystalline diamond, cermet, and coated carbide under dry cutting conditions. Among the two components of the cutting force, it was noted that the primary cutting force was the largest. A full factorial response surface regression model has been developed and it is found that the regression model can predict cutting force and temperature with fair accuracy.     

Performance evaluation of different carbide inserts in turning of newly developed Al-12Si-0.1Sr alloy

An Al-12Si-0.1Sr alloy ingot was manufactured using a permanent mold casting technique. The microstructure and mechanical properties of this alloy were researched. Effects of different cutting conditions (cutting speed-V: 200 m/min, 300 m/min, and 400 m/min and feed rate-f: 0.05 mm/rev, 0.1 mm/rev, and 0.15 mm/rev) on the cutting force (F) and surface roughness (R_a) during machining using uncoated and physical vapor deposition- titanium aluminum nitride coated carbide inserts were also revealed. Microstructure of the alloys consists of α phase, intermetallic δ and Al₄Sr phases, thin spherical eutectic, and irregular coarse-shaped primary silicon particles. Cutting force and surface roughness decreased with the increased cutting speed during turning with uncoated, and titanium aluminum nitride coated inserts while they increased feed rate. A built-up edge and built-up layer were formed in both cutting inserts. The built-up edge and built-up layer decreased with increasing cutting speed and increased feed rate. The cutting force, surface roughness, built-up edge, and built-up layer were lower in uncoated inserts compared to the titanium aluminum nitride coated inserts.     

Effect of machining parameters on surface roughness and material removal rate in finish turning of ±30° glass fibre reinforced polymer pipes

This paper studies the effect of varying machining parameters in turning on surface roughness and material removal rate (m.r.r.) for ±30° filament wound glass fibre reinforced polymers (GFRP) in turning operations using coated tungsten carbide inserts under dry cutting conditions. The paper describes the development of an empirical model for turning GFRP utilising factorial experiments. Second order predictive model covering speed, feed, depth of cut and tool nose radius has been developed at 95% confidence interval for surface roughness and material removal rate. Contour plots of the surface roughness and m.r.r. for different machining conditions have been generated from the empirical equations. Overlaid contour graph help in obtaining iso-value of roughness for different values of m.r.r.     

An application of goal programming technique in metal cutting

This paper outlines the use of the goal programming technique in selecting levels of machining parameters in a fine turning operation on A1S1 4140 steel using cemented tungsten carbide tools. Goals that are proposed to be achieved are: (i) to finish turning the required depth in one pass, mid (ii) to finish turning within a stipulated time. Constraints used are: R.M.S. surface finish values, cutting horse power of the machine, ranges for cutting speed, feed and depth of cut. A predictive equation to predict the R.M.S. Surface roughness values from the machining variables, cutting speed, feed, depth of cut, and time of cut was used. This mathematical model was developed using stepwise regression analysis on the experimental data for 1/64 in. nose radius cemented tungsten carbide cutting tool. Experiment with the machining variables at different levels were performed to obtain the data. A statistically designed experiment called the rotatable design was used for the experimental design     

Development of ANFIS model and machinability study on dry turning of cryo-treated PH stainless steel with various inserts

This present investigation deals about the machinability comparison of cryogenically treated 15-5 PH stainless steel with various cutting tools such as uncoated tungsten carbide, cryogenic-treated tungsten carbide and wiper geometry inserts. Cryo-treated PH stainless steel is considered as the work material in this investigation and experimental trials were performed under dry turning condition. The machinability aspects considered for evaluation are cutting force (F_z), surface roughness (R_a) and tool wear. The outcomes of experimentation reveal that the tungsten carbide inserts which are cryogenically treated provide improved performance in machining while comparing with conventional and wiper geometry inserts at all machining conditions. The measured cutting force and the observed flank wear were less for the cryo-treated inserts. However, wiper tool produces a better surface finish during machining. An artificial intelligence decision-making tool named Adaptive Neuro Fuzzy Inference System has been evolved to determine the relation among the considered input machining variables and output measures, namely cutting force and surface roughness of the machined surface. An analysis has been performed to compare the results obtained from developed models and experimental results.     

The influence of depth of cut on the machinability of an alloyed austempered ductile iron

The volume fraction of high carbon austenite present in the microstructure of austempered ductile iron (ADI) is one of the important factors that influence the mechanical and physical properties of the alloy. Formation of martensite by TRIP (transformation induced plasticity) mechanism during the machining operation in which a large amount of stress is applied to the microstructure results in a decrease in machinability of austempered ductile iron which has affected the expansion of ADI in industry. In this article, the effect of depth of cut as a machining variable is assessed in an alloyed austempered ductile iron containing Cu, Ni and Mo. The measurements of mechanical properties including impact energy, tensile strength, hardness and microhardness along the cross-section of samples are reported for samples austenitized at 870 °C followed by austempering at 375, 340 and 300 °C. Results indicate that contrary to the behavior of many alloys, in austempered ductile iron, reducing the depth of cut will not improve the machinability. In the case of studied composition, cutting with depths of 0.5 and 0.1 mm had the best and worst results, respectively.     

Optimization of machining variables in turning hard cast irons with PCBN-inserted tools

The paper presents empirical relations between the turning performance characteristics, process variables, technical restrictions, and machining costs. The authors of the paper have performed calculations of cutting conditions and cutting edge geometry for polycrystalline cubic boron nitride inserts, analyzed the influence of cast iron hardness and technical restrictions on the assessment parameters.     

An experimental study on grinding of Zr-based bulk metallic glass

There are limited studies in the literature about machinability of bulk metallic glass(BMG).As a novel and promising structural material,BMG material machining characteristics need to be verified before its utilization.In this paper,the effects of cutting speed,feed rate,depth of cut,abrasive particle size/type on the BMG grinding in dry conditions were experimentally investigated.The experimental evaluations were carried out using cubic boron nitride(CBN) and Al_2O_3 cup wheel grinding tools.The parameters were evaluated along with the results of cutting force,temperature and surface roughness measurements,X-ray,scanning electron microscope(SEM)and surface roughness analyse.The results demonstrated that the grinding forces reduced with the increasing cutting speed as specific grinding energy increased.The effect of feed rate was opposite to the cutting speed effect,and increasing feed rate caused higher grinding forces and substantially lower specific energy.Some voids like cracks parallel to the grinding direction were observed at the edge of the grinding tracks.The present investigations on ground surface and grinding chips morphologies showed that material removal and surface formation of the BMG were mainly due to the ductile chip formation and ploughing as well as brittle fracture of some particles from the edge of the tracks.The roughness values obtained with the CBN wheels were found to be acceptable for the grinding operation of the structural materials and were in the range of 0.34-0.58 μm.This study also demonstrates that conventional Al_2O_3 wheel is not suitable for grinding of the BMG in dry conditions.     

Optimizing feed force for turned parts through the Taguchi technique

The objective of the paper is to obtain an optimal setting of turning process parameters (cutting speed, feed rate and depth of cut) resulting in an optimal value of the feed force when machining EN24 steel with TiC-coated tungsten-carbide inserts. The effects of the selected turning process parameters on feed force and the subsequent optimal settings of the parameters have been accomplished using Taguchi’s parameter design approach. The results indicate that the selected process parameters significantly affect the selected machining characteristics. The results are confirmed by further experiments.     

Cost-effective way of hard turning with newly developed HSN2-coated tool

EN-31 (AISI 52100, hardness 55 HRC) is one of the difficult-to-cut steel alloys and it is commonly used in shafts and bearings. Nowadays, it is becoming a challenge to the cutting tool material for economical machining of extremely tough and hard steels. In general, CBN and PCBN tools are used for machining hardened steel. However, machining cost using these tools becomes higher due to high tool cost. For this purpose, carbide tool using selective coatings is the best substitute having comparable tool life, while its cost is approximately one-tenth of CBN tool. In this work, the newly developed second-generation TiAlxN super nitride (i.e., HSN²) is selected for PVD coating on carbide tool insert and further characterized using thermogravimetric analysis and differential scanning calorimetry for oxidation and thermal stability at high temperature. Later, HSN²-coated carbide inserts are successfully tested for their sustainability to expected tool life for turning of AISI 52100 steel. In the present study, forces, surface finish, and tool wear are used as a measure to appraise the performance of hard turning process. Experimentally, it is found that speed, feed rate, and depth of cut have considerable impact on forces, insert wear, and surface roughness of the machined surface.     

Comparison of tool life and surface characteristics of uncoated,coated carbide and ceramic tools during machining of SiC reinforced ZA43 alloy MMC

Abstract

In the present investigation, machinability issues of zinc–aluminium (ZA43) alloy reinforced with silicon carbide particles (SiC) were evaluated. The fabrication of composite was done through liquid metallurgy technique. Metal matrix composite (MMC) was subjected to turning using conventional lathe with three grades of cutting tools, namely, uncoated carbide tool, coated carbide tool and ceramic tool. Surface roughness and tool wear were measured during the machining process. Results reveal that roughness increases with increase in the reinforcement concentration and particle size. Feed has direct influence on roughness, i.e. surface deteriorates with higher feeds. Depth of cut has very minimum effect on the surface roughness, while inverse effect of cutting speed on the roughness was observed (i.e. increase in the cutting speed leads to better finish on the specimen). Tool wear was studied during the investigation, and it was noticed that MMC with higher reinforcement concentration and particle size cause severe wear on the flank of the cutting tool. Increase in the cutting speed, feed and depth of cut also increases the flank wear on the tool. Out of all the three grades of tools, coated carbide tool outperformed uncoated carbide and ceramic tools.     

Experimental study on the meso-scale milling of tungsten carbide WC-17.5Co with PCD end mills

Tungsten carbide is a material that is very difficult to cut, mainly owing to its extreme wear resistance. Its high value of yield strength, accompanied by extreme brittleness, renders its machinability extremely poor, with most tools failing. Even when cutting with tool materials of the highest quality, its mode of cutting is mainly brittle and marred by material cracking. The ductile mode of cutting is possible only at micro levels of depth of cut and feed rate. This study aims to investigate the possibility of milling the carbide material at a meso-scale using polycrystalline diamond (PCD) end mills. A series of end milling experiments were performed to study the effects of cutting speed, feed per tooth, and axial depth of cut on performance measures such as cutting forces, surface roughness, and tool wear. To characterize the wear of PCD tools, a new approach to measuring the level of damage sustained by the faces of the cutter's teeth is presented. Analyses of the experimental data show that the effects of all the cutting parameters on the three performance measures are significant. The major damage mode of the PCD end mills is found to be the intermittent micro-chipping. The progress of tool damage saw a long, stable, and steady period sandwiched between two short, abrupt, and intermittent periods. Cutting forces and surface roughness are found to rise with increments in the three cutting parameters, although the latter shows signs of reduction during the initial increase in cutting speed only. The results of this study find that an acceptable surface quality (average roughness R_a<0.2 μm) and tool life (cutting length L>600 mm) can be obtained under the conditions of the given cutting parameters. It indicates that milling with PCD tools at a meso-scale is a suitable machining method for tungsten carbides.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00298-y     

Influence of melt treatments and polished CVD diamond coated insert on cutting force and surface integrity in turning of Al-7Si and Al-7Si-2.5Cu cast alloys

The microstructures, machinability and surface characteristics of Al-7Si and Al-7Si-2.5Cu cast alloys were studied after various melt treatments like grain refinement and modification. The results indicate that combined grain refined and modified Al-7Si-2.5Cu cast alloys have microstructures consisting of uniformly distributed α-Al grains, eutectic Al-silicon and fine CuAl₂ particles in the interdendritic region. These alloys exhibited better machinability and surface characteristics in the cast condition compared with the same alloy subjected to only grain refinement or modification. Performances of the turning inserts (uncoated and polished CVD diamond coated) were evaluated in machining Al-7Si and Al-7Si-2.5Cu cast alloys under dry environment using a lathe. The polished CVD diamond coated insert outperformed the uncoated cutting insert which suffered from sizeable edge buildup leading to higher cutting force and poor surface finish. The polished CVD diamond coated insert shows a very small steady wear without flaking of the diamond film during cutting. This paper attempts to investigate the influence of grain refinement, modification and combined action of both on the microstructural changes in the Al-7Si and Al-7Si-2.5Cu cast alloys and their machinability and surface finish when different turning inserts are used.