Experimental investigation on flank wear and tool life, cost analysis and mathematical model in turning hardened steel using coated carbide inserts

Turning hardened component with PCBN and ceramic inserts have been extensively used recently and replaces traditional grinding operation. The use of inexpensive multilayer coated carbide insert in hard turning is lacking and hence there is a need to investigate the potential and applicability of such tools in turning hardened steels. An attempt has been made in this paper to have a study on turning hardened AISI 4340 steel (47 ± 1 HRC) using coated carbide inserts (TiN/TiCN/Al2O3/ZrCN) under dry environment. The aim is to assess the tool life of inserts and evolution of flank wear with successive machining time. From experimental investigations, the gradual growth of flank wear for multilayer coated insert indicates steady machining without any premature tool failure by chipping or fracturing. Abrasion is found to be the dominant wear mechanisms in hard turning. Tool life of multilayer coated carbide inserts has been found to be 31 minute and machining cost per part is Rs.3.64 only under parametric conditions chosen i.e. v = 90 m/min, f = 0.05 mm/rev and d = 0.5 mm. The mathematical model shows high determination coefficient, R2 (99%) and fits the actual data well. The predicted flank wear has been found to lie very close to the experimental value at 95% confidence level. This shows the potential and effectiveness of multilayer coated carbide insert used in hard turning applications

Surface defect machining : a new approach for hard turning

Hard turning is emerging as a key technology to substitute conventional grinding processes, mainly on account of lower equipment cost, short setup time, and a reduced number of process steps. This is, however, being impeded by a number of challenges required to be resolved, including attainable surface roughness, surface deteriorations, surface residual stresses and metallurgical transformations on the machined steel surface (white layer). In this thesis, a novel approach named Surface Defect Machining (SDM) is proposed as a viable solution to resolve a large number of these issues and to improve surface finish and surface integrity. SDM is defined as a process of machining, where a workpiece is first subjected to surface defects creation at a depth less than the uncut chip thickness; either through mechanical and/or thermal means; then followed by a normal machining operation so as to reduce the cutting resistance. A comprehensive understanding of SDM is established theoretically using finite element method (FEM). Also, an experimental study has been carried out for extensive understanding of the new technique. A good agreement between theoretical and experimental investigations has been achieved. The results show very interesting salient features of SDM, providing favourable machining outcomes. These include: reduced shear plane angle, reduced machining forces, lower residual stresses on the machined surface, reduced tool-chip interface contact length and increased chip flow velocity, as well as reductions in overall temperature in the cutting zone and changing the mechanism of chip morphology from jagged to discontinuous. However, the most prominent outcome is the improved attainable surface roughness. Furthermore, SDM shows the ability to exceed the critical feed rate and achieve an optical surface finish upto 30 nm. A scientific explanation of the improved surface roughness suggests that during SDM, a combination of both the cutting action and the rough polishing action help to improve the machined surface. Based on these findings, it is anticipated that a component machined using the SDM method should exhibit improved quality of the machined surface, which is expected to provide tremendous commercial advantages in the time to come

Hard turning of martensitic AISI 440B stainless steel

Hard turning has been in use for some time to achieve close dimensional tolerances to eliminate time consuming and costly grinding operations. The most widely used cutting tools for finish machining of hardened steels under dry cutting conditions are the ceramics and PcBN cutting tools. The purpose of this study was to investigate the machinability of hardened martensitic AISI 440 B stainless steel (HRC 42-44) using commercially available cutting tools: alumina based ceramic and PcBN, by hard turning under different machining conditions, by providing an in-depth understanding of wear mechanisms of these cutting tools. The study also developed a serrated chip formation mechanism of the workpiece and provided a deep understanding of the chemical interaction between workpiece and cBN cutting tools, through microstructural analysis of the adhered layer on the worn cutting tool. Experimental studies on the effects of cutting parameters on the tool wear mechanism, cutting forces; surface roughness, dimensional accuracy, and chip formation mechanism were investigated. The characterization of the workpiece, cutting tools, chips and wear scars on the cutting tools was performed using an X-ray diffractometer, and optical, scanning and transmission electron microscopes, as well as an energy dispersive spectroscope (EDS). The cutting speeds selected for testing the cutting tools were in the range of 100 m/min and 600 m/min, depending on the type of parameter investigated. Two depths of cut, 0.1and 0.2 mm, and three feed rates, 0.05, 0.1 and 0.15 rev/min, were selected for the experiments. Experimental results showed that the flank wear in the PcBN cutting tool is lower than that of the mixed alumina, with PcBN showing better wear resistance at all cutting conditions (about five times longer in some instances). Apart from the cutting speed, the feed rate was found as a parameter that directly influences the flank wear rate of the cutting tool. The wear mechanism for the ceramic cutting tool is predominantly abrasive wear, and for PcBN tools it was adhesive wear and abrasive wear. The abrasive wear was caused by hard carbide particles in the workpiece material resulting in grooves formed on the flank face. There was formation of a transferred layer followed by plastic deformation of the workpiece material on the rake face of the PcBN tool when cutting at low cutting speed and feed rate. At much higher cutting speeds, some form of chemical wear preceded by adhesion and abrasion was the main tool wear resulting from the chemical affinity between the PcBN tool and the workpiece. Better surface finish (Ra) was recorded for mixed ceramics but with deteriorating surface topography. The increase in the cutting speed results for improvement in the surface finish produced by both cutting tools was investigated. The final part, using the PcBN cutting tool, produced better dimensional accuracy resulting from its better wear resistance at the flank face. The results also show that good dimensional accuracy can be achieved with cBN tools using a CNC machine with high static and dimensional stiffness coupled with high precision hard turning. The influence of cutting conditions on the chip formation showed production of continuous chip at a cutting speed of 100 m/min and segmented chip at higher cutting speeds above 200 m/min by both cutting tools. The increasing cutting speed affects the formation of shear localised chips with rapid increase in shear strain rate and degree of segmentation at cutting speeds higher than 200 m/min. The microstructure of the chip produced shows the distinct carbide grain in the martensite of the work material with intense shear localisation in the primary deformation zone of the cutting tool and formation of white layer in the secondary deformation zone. The microstructure of the crater of the worn PcBN cutting tool at cutting speeds of 100 m/min and 600 m/min were studied in detail. A situ lift-out technique, in a Focused Ion Beam/SEM instrument, was used to produce thin foil specimens, which were taken out of the crater face of the PcBN tool and observed using SEM and TEM. The SEM and TEM study showed evidence of chemical interaction between the work material and the PcBN tool. Fe from the work material was found in the vicinity of TiC and AlB grains of the PcBN tool, with TiC having greater affinity for Fe. Oxidation of the elements was common in all Fe-rich areas. The microstructure of the worn PcBN cutting tool at the cutting speed of 600 m/min showed deeper penetration of Cr and Fe into the cBN tool, which was not easily detected by SEM at the cutting speed of 100 m/min. The hard turning operations using the PcBN cutting tool for substituting traditional machining operations was successfully performed in the industrial environment. The overall surface finish and dimensional accuracy generated during the application of CBN-100 for machining within the industrial environment on specified mass produced shape showed a component acceptable tolerance range with good surface finish similar to that of the grinding operation

Modelling of hard turning process

In the present work, the workpiece material taken is chrome-moly alloy steel. This is a hard material having hardness 48 HRC. This alloy steel bears high temperature and high pressure and its tensile strength is high. It is very resistive to corrosion and temperature. For these useful properties it is used in power generation industry and petrochemical industry. Also it is used to make pressure vessels. For machining of workpiece the insert chosen is Tic coated carbide insert. Three factors speed, feed and depth of cut were taken at three levels low, medium and high. By the L27 orthogonal design twenty seven runs of experiments were performed. For each run of experiment the time of cut was 2 minutes. The output responses measured were surface roughness, power consumption, chip reduction co-efficient and tool wear (flank wear). All the output responses were analyzed by SN ratio, analysis of variance, and response table. The criteria chosen here is smaller the better and the method applied is Taguchi method

Optimization of hard turning process parameters with PCBN tool based on the Taguchi method

U ovom radu, primijenjena je Taguchijeva metoda za pronalaženje optimalne razine parametara procesa tvrdog tokarenja čelika AISI 4142 koristeći PCBN alatne pločice. Ortogonalni plan (L9 (3^4)), omjer signal - šum (S/N) i analiza varijance (ANOVA) primijenjeni su u istraživanju utjecaja parametara obrade (brzine rezanja, posmaka i dubine rezanja) na hrapavost obrađene površine. Utvrdilo se signifikantne faktore koji utječu na hrapavost obrađene površine, i definiralo optimalne razine parametara obrade pronalaženjem najniže hrapavosti obrađene površine (odziva) i najpogodnijeg omjera signal – šum. Koristeći višestruku regresiju dobiveni su eksponencijalni model, linearni polinomski model prvog reda i polinomski model drugog reda da bi se utvrdila korelacija između hrapavosti obrađene površine i nezavisnih varijabli. Na kraju, test provjere je potvrdio da je Taguchijev plan uspješan u optimiziranju parametara tokarenja s obzirom na hrapavost obrađene površine.In this paper, the Taguchi method is applied to find optimum process parameters for hard turning of hardened steel AISI 4142 using PCBN tool. Orthogonal design (L9 (3^4)), signal-to-noise ratio (S/N) and analysis of variance (ANOVA) are applied to study performance characteristics of cutting parameters (cutting speed, feed and depth of cut) with consideration of surface roughness. Significant factors affecting surface roughness were identified, and the optimal cutting combination was determined by seeking the best surface roughness (response) and signal-to-noise ratio. Using multiple regression the exponential, first order linear and second order prediction models were obtained to find the correlation between surface roughness and independent variables. Finally, confirmation tests verified that the Taguchi design was successful in optimizing turning parameters for surface roughness

Experimental Analysis on Surface Roughness of En-24 Hardened Steel

In this thesis, it is about the machining of the EN-24 hardened steel that involves turning operation of the EN-24 with the help of coated carbide insert of ISO designation CNMG 120408. Analysis of the surface roughness is done experimentally with specific input values of feed, depth of cut and speed and gradually the optimal condition is found out. A relation between the inputs and the output is determined and thereafter, the analysis is done how the inputs affected the output. First using the full factorial composite design a layout of the experiment is made after which it is conducted. The profilometer is used to measure the surface roughness. Here the L27 Taguchi method is used for the determination of the change in surface roughness with respect to the speed, feed and depth of cut. This can be analysed with help of the contour plots, 3-D surface plots and different graphs produced by the MINTAB 16 software. We can easily determine the effects by visualizing the main effect plots and interaction plots also. With the help of ANOVA (Analysis of Variance), the most effective or the optimal parameters for the output are determined. The regression equations are also obtained. All the parameters are found to be significant in determination of the surface roughness and possible conclusions are made at the end

Otimização multiobjetivo por estimadores robustos multivariados

As organizações focam em determinar condições ideais de operação com o intuito de garantir a qualidade de seus processos e serviços, uma vez que os processos industriais podem exibir um elevado grau de variabilidade. Neste contexto, o uso de estimadores robustos torna-se uma alternativa adequada para modelar os dados experimentais; sendo que o termo robusto descreve a capacidade que um estimador tem em superar as influências exercidas pelos valores discrepantes. Encontrar uma combinação de estimadores de centralidade e dispersão que seja capaz de modelar dados suscetíveis à variabilidade é um desafio a ser explorado. Desse modo, este presente trabalho, com o auxílio da Análise de Componentes Principais (ACP), visa à obtenção de respostas transformadas em escores de componentes que explicarão a estrutura de variância-covariância a partir de combinações lineares das varáveis originais. Em consequência, o objetivo geral é o de validar um algoritmo de otimização multiobjetivo baseado no agrupamento de respostas correlacionadas e modeladas por estimadores robustos. Com o auxílio do método da Interseção Normal à Fronteira, é proposta uma otimização multiobjetivo para funções obtidas pelo Erro Quadrático Médio Multivariado (EQMM) que combina técnicas da Metodologia de Superfície de Resposta com a ACP, visando obter soluções Pareto-ótimas. O objeto de estudo definido para a aplicação desta proposta é o processo de torneamento do aço de corte fácil ABNT/SAE 12L14 composto por um arranjo cruzando onde 12 condições de ruído são consideradas para a obtenção da variável de resposta que é a rugosidade superficial (Ra). O resultado ótimo é definido pelo tomador de decisão fuzzy e para provar a eficiência da resposta encontrada, experimentos de confirmação foram realizados. Em um nível de confiança de 95%, o valor ótimo pertence aos intervalos de confiança multivariados apenas para o Modelo B, no qual a mediana e o MAD são considerados e, confirmando assim, qual par de estimadores atinge a solução em um cenário de projeto robusto de parâmetro. Através da pesquisa proposta, o modelo desenvolvido pode ser utilizado em indústrias para determinação de parâmetros de usinagem para obtenção de alta qualidade com consumo mínimo de energia e, consequentemente, máxima produtividade

Selective cytotoxic activity of methyl-3,4,5-trihydroxybenzoate isolated from Kernel of Bambangan (Mangifera pajang)

Bambangan (Mangifera pajang) has been shown to exhibit anticancer activity. One of the major bioactive compounds present in the methanol extract of kernel of M. pajang is methyl 3,4,5-trihydroxybenzoate (methyl gallate). The present study was conducted to evaluate the cytotoxic activity of this compound against selected cancer cell lines such as hormone dependent breast cancer (MCF-7), nonhormone dependent breast cancer (MDA-MB-231), prostate cancer (PC-3), pancreatic cancer cell (CP-2) and colon cancer (HCT-116) cell lines. Methyl gallate was isolated from methanol extract by using column chromatography and the compound was further confirmed by using NMR, GC-MS analysis and comparison of spectral data of the isolated data with published report. The cytotoxicity of the compound was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay at concentrationsranging from 0 to 100 µM. The results showed that the compound only induced cytotoxicity in MCF-7 and PC-3 cell lines with IC50 values of 54.7 ± 4.73 and 97.6 ± 4.04 µM, respectively. Furthermore, Capan 2, MDA-MB-231 and HCT-116 showed no inhibition towards the cell proliferation after the treatment with compound (IC50 values more than100 µM). Thus, the compound isolated from kernel of M. pajang exhibited selective cytotoxic activity against selected cancer cell lines

Comparison of Flank Super Abrasive Machining vs. Flank Milling on Inconel® 718 Surfaces

Thermoresistant superalloys present many challenges in terms of machinability, which leads to finding new alternatives to conventional manufacturing processes. In order to face this issue, super abrasive machining (SAM) is presented as a solution due to the fact that it combines the advantages of the use of grinding tools with milling feed rates. This technique is commonly used for finishing operations. Nevertheless, this work analyses the feasibility of this technique for roughing operations. In order to verify the adequacy of this new technique as an alternative to conventional process for roughing operations, five slots were performed in Inconel (R) 718 using flank SAM and flank milling. The results showed that flank SAM implies a suitable and controllable process to improve the manufacture of high added value components made by nickel-based superalloys in terms of roughness, microhardness, white layer, and residual stresses.The authors wish to acknowledge the financial support received from the Spanish Ministry of Economy and Competitiveness with the project TURBO (DPI2013-46164-C2-1-R), grant number [BES-2014-068874], to HAZITEK program from the Department of Economic Development and Infrastructures of the Basque Government and from FEDER funds, related to the HEMATEX project and Vice-chancellor of Innovation, Social Compromise and Cultural Action from UPV/EHU (the Bizialab program from the Basque Government). Finally, thanks are also addressed to Spanish Project MINECO DPI2016-74845-R and RTC-2014-1861-4