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.     

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.     

Effect of physical vapor deposited bilayer (AlCrN + TiAlN) coating on high-speed steel single point cutting tool

This paper presents the investigation of hardness, tool weight loss percentage, surface roughness, surface morphology and tool worn-out morphology of high-speed steel (HSS) single point cutting tool and aluminum chromium nitride and titanium aluminum nitride (AlCrN +TiAlN) bilayer coated HSS tool. The two tools with predetermined geometries were analyzed in the same machining conditions at the same center lathe. The results identified that the weight loss percentage of the bilayer coated tool was less when compared with the uncoated tool. Additionally, the hardness of the bilayer coated tool was greater than the uncoated tool. Surface roughness of the bilayer coated tool was lower than the uncoated tool and tool wear was less for the bilayer coated tool when compared to the uncoated tool.     

Study on the influential process parameters in machining the austempered ductile iron

Since the machinability data on grade 3 austempered ductile iron is scarce, this experimental work mainly focuses on the impact of machining parameters on cutting force and surface roughness while turning the above work material with cubic boron nitride and tungsten carbide inserts. Parameters like depth of cut, cutting speed and feed were considered in this study when analyzing the machinability of austempered ductile iron. Austempered ductile iron was turned with CBN and coated WC inserts. The response surface methodology was utilized to design the experiments and optimize the cutting parameters for the work material by each of the above inserts. The cubic boron nitride insert performs well as compared to the coated tungsten carbide for turning the austempered ductile iron and it has been concluded by taking lower force and higher surface finish in to consideration. The optimum parameters for turning austempered ductile iron with the cubic boron nitride insert is as follows: 174 meter/minute cutting speed, 0.102 millimeter/revolution feed and depth of cut of 0.5 millimeter.     

Machining Parameters Optimization of Titanium Alloy using Response Surface Methodology and Particle Swarm Optimization under Minimum-Quantity Lubrication Environment

The present paper depicts an application of response surface methodology (RSM) and particle swarm optimization (PSO) technique for optimizing the machining factors in turning of titanium (Grade-II) alloy using cubic boron nitride insert tool under minimum quantity lubricant (MQL) environment. The three machining factors, i.e., cutting speed (V_c), feed rate (f) and side cutting edge angle (approach angle π), are designed as three factors by using RSM design, which is withal subject to several constraints including tangential force (F_c), tool wear (V_Bmax), surface roughness (R_a) and tool-chip contact length (L). The multiple regression technique was used to establish the interaction between input parameters and given responses. Moreover, the results have been presented and optimized process parameters are acquired through multi-response optimization via desirability function as well as the PSO technique. The lower values of V_c (200 m/min), f (0.10 mm/rev) and higher values of ? (90°) are the optimum machining factors for minimizing the aforementioned responses. It was also observed that the selected responses predicated on PSO are much closer as that of the values acquired in view of the desirability function approach. Henceforth, PSO has the potential to cull appropriate machining factors while turning titanium (Grade-II) alloys under MQL conditions.     

Mechanical micro-drilling of nimonic 80A superalloy using uncoated and TiAlN-coated micro-drills

Micro-drilling is a complex mechanical machining process. Micro-drilling experiences an early tool damage which is a major drawback for nickel-based superalloy. This paper examines the wear condition on the micro-tool cutting edge, surface roughness of machined holes, and hole diameter analysis in micro-drilling of Nimonic 80A, using two types of micro-drills (uncoated and TiAlN coated) with 0.79?mm diameter. Micro-drilling tests, using cutting speed (V_c), feed rate (f_z), and the micro-drill diameter as experimental parameters were carried out to bring out the best optimized machining conditions in micro-drilling of Nimonic 80A. Wear on the tool cutting edge and burr height occurring at the entrance of drilled holes were measured at constant period to give the lastingness of micro-drill. Quality of holes were analyzed in terms of surface roughness inside the hole and the hole diameter after every five drilled holes. The result obtained from the above analysis showed that TiAlN-coated micro-drill performs way better than the uncoated micro-drill in terms of wear, surface roughness, hole quality, and burr. Thus, the above performed study gives the knowledge to select micro-tool for machining of Nimonic 80A which could be useful in the aerospace industry.     

Effect of cryogenic CO2 and LN2 coolants in milling of aluminum alloy

The research work was carried out on the end milling of Al 6082-T6 alloy with cryogenic CO₂, LN₂ and wet conditions. The highest axial force (F_z), normal force (F_y) and feed force (F_x) values were recorded on cryogenic LN₂ machining. Use of cryogenic LN₂ helped to reduce the cutting temperatures up to 38.29% and 32.8% when compared with wet and cryogenic CO₂ conditions, respectively. The conventional fluid coolant offered a better surface roughness value (R_a) over cryogenic coolants at a feed rate of 0.015 and 0.02 mm/tooth and cutting speed of 100 m/min. The workpiece surface quality degraded in cryogenic machining conditions during the slot end milling operation of aluminum alloy under the given machining parameters.     

High-feed turning of AISI D2 tool steel using multi-radii tool inserts: Tool life,material removed,and workpiece surface integrity evaluation

Multi-radii tool inserts offer novel configuration that comprises of multiple radii at tool nose. A review of the available literature indicates that there exists a need for experimental investigation on certain key machining characteristics of such tools. This paper reports on tool wear/life, material removed, and workpiece surface roughness when multi-radii mixed alumina TiN coated tool inserts are employed for turning D2 steel. Inserts of three different nose radii (0.40, 0.80, 1.20?mm) at six levels of feed rates (ranging from 0.157 to 0.562?mm/rev) are used. Results show that flank wear is the dominant wear mode with catastrophic tool failure occurring at highest nose radius (1.20?mm) and feed rate (0.562?mm/rev) combination. Also, there is ～59% reduction in tool life accompanied by ～62% increase in quantity of material removed as the feed rate increases from 0.157 to 0.562?mm/rev at maximum nose radius (1.20?mm). Feed rate is found to be statistically significant factor for all three responses considered herein at 95% confidence level. Surface integrity assessment at maximum feed rate reveals presence of a strain hardened layer extending to the depth of 150?µm below the machined surface without any observance of white layer for all the tool conditions and nose radius.     

Effect of cutting speed on the performance of Al2O3 based ceramic tools in turning nodular cast iron

This paper presents the results of an experimental investigation on the effect of cutting speed in turning nodular cast iron with alumina (Al₂O₃) based ceramic tools. Three different alumina based ceramic cutting tools were used, namely TiN coated Al₂O₃ + TiCN mixed ceramic, SiC whisker reinforced Al₂O₃ and uncoated Al₂O₃ + TiCN mixed ceramic tool. Turning experiments were carried out at four different cutting speeds, which were 300, 450, 600 and 750 m/min. Depth of cut and feed rate were kept constant at 1 mm and 0.1 mm/rev, respectively, throughout the experiments. Tool performance was evaluated with respect to tool wear, surface finish produced and cutting forces generated during turning. Uncoated Al₂O₃ + TiCN mixed ceramic was the worst performing tool with respect to tool wear and was the best with respect to surface finish. SiC whisker reinforced Al₂O₃ exhibited the worst performance with respect to cutting forces. If tool wear, surface finish and cutting force results are considered together, among the three tools studied, TiN coated Al₂O₃ + TiCN mixed ceramic tool is the most suitable one for turning nodular cast iron, especially at high cutting speeds (V_c > 600 m/min).     

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.     

In Vivo and In Vitro investigation of titanium oxide layers coated on LTI-carbon by IBED

A layer of titanium oxide layer was coated on low temperature isotropic pyrolytic carbon (LTI-carbon), a prevailing material used for artificial heart valves' fabrication, by ion beam enhanced deposition (IBED). Glancing angle x-ray diffraction (GAXRD), X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and transmission electronic microscopy (TEM) were used to characterize the deposited titanium oxide layer. The results show that the layer is polycrystalline with TiO, Ti₂O₃ and TiO₂ coexisting and the root-mean-square (RMS) roughness of the surface is measured to be 8.7 nm. Platelet adhesion experiments show that the adherent platelet on titanium oxide layer is about four times less than that on LTI-carbon. In vivo investigation was performed by implanting LTI-carbon and a titanium oxide layer coated LTI-carbon into the femoral artery of a dog for 4 weeks. By means of scan electron microscopy, coagulation, fibrin, deformed blood red cells and aggregation of adherent platelet were found on the surface of the uncoated LTI-carbon, whereas, nothing but a few normal-shaped blood red cells were found on the titanium oxide coated LTI-carbon. It can be concluded that titanium oxide coated LTI-carbon has a much better blood compatibility than that of the LTI-carbon.     

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 (V_c). The depth of the drilling was constant. Cutting temperature (T), thrust force (F_t), surface roughness (R_a), 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 (R_a) values were higher for LN₂ coolants. Hole quality is not favorable in LN₂ coolant supply.     

Ranges of application of free-cutting steels and recommended tool materials

Abstract

Four low carbonfree-cutting steels (0·11% carbon resulphurised, 0·11% carbon leaded–resulphurised, 0·08% carbon resulphurised, and 0·15% carbon leaded) were turned, dry, with a series of six types of cutting tool in which rake angle, tool material, and coating were varied (5° rake, high speed steel, TiN coated and uncoated; 15° rake, high speed steel, TiN coated and uncoated; 5° rake, cemented carbide, TiN coated and uncoated) in order to determine the optimum tool–workpiece combination for three cutting speed ranges: a low speed range in which the built-up edge (BUE) was forming or about to form; a speed range covering the BUE regime; and a higher speed range in which the BUE became a built-up layer (BUL). Tool–workpiece interaction was assessed by measurement of cutting forces, chip form, surface finish, tool temperature, and wear. It is suggested by the results that the best combination in the low speed range is that of leaded–resulphurised steel and uncoated high speed steel. In the BUE range, the combination of leaded steels and uncoated tools should be avoided; at higher speeds, coated tools are preferred, with non-resulphurised leaded steel giving the lowest tool temperatures and highest cutting speeds before ultimate failure. These recommendations should be treated with caution and used only as guidelines.

MST/867     

Development of diamond coated tool and its performance in machining Al-11% Si alloy

An attempt has been made to deposit CVD diamond coating on conventional carbide tool using hot filament CVD process. ISO grade K10 turning inserts with SPGN 120308 geometry were used to deposit diamond coating. This diamond coating well covering the rake surface, cutting edges and flank surfaces could be successfully deposited. The coatings were characterized by SEM, XRD and Raman spectroscopy for coating quality, morphology etc. Performance of diamond coated tool relative to that of uncoated carbide tool was evaluated in turning Al-11% Si alloy under dry environment. The diamond coated tool outperformed the uncoated carbide tool which severely suffered from sizeable built-up edge formation leading not only to escalation of cutting forces but also poorer surface finish. In contrast, the diamond coated tool, owing to chemical inertness of diamond coating towards the work material, did not show any trace of edge built-up even in dry environment and could maintain low level of cutting forces and remarkably improved surface finish. It has been further revealed that success of the diamond coated tool depends primarily on adhesion of the diamond coating with the carbide substrate and this is strongly influenced by the pre-treatment of the carbide substrate surface before coating.     

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.     

Investigation of the influential parameters of machining of AISI 304 stainless steel

Austenitic stainless steels are hard materials to machine, due to their high strength, high ductility and low thermal conductivity. The last characteristic results in heat concentration at the tool cutting edge. This paper aims to optimize turning parameters of AISI 304 stainless steel. Turning tests have been performed in three different feed rates (0.2, 0.3, 0.4 mm/rev) at the cutting speeds of 100, 125, 150, 175 and 200 m/min with and without cutting fluid. A design of experiments (DOE) and an analysis of variance (ANOVA) have been made to determine the effects of each parameter on the tool wear and the surface roughness. It is being inferred that cutting speed has the main influence on the flank wear and as it increases to 175 m/min, the flank wear decreases. The feed rate has the most important influence on the surface roughness and as it decreases, the surface roughness also decreases. Also, the application of cutting fluid results in longer tool life and better surface finish.     

Soft tissue attachment on sol–gel-treated titanium implants in vivo

This study was designed to examine the attachment and reactions of soft tissues to sol–gel-derived TiO₂ coatings. In the first experiment, TiO₂ coated and uncoated titanium cylinders were placed subcutaneously into the backs of rats for 3, 11 and 90 days. Tissue response and implant surfaces were characterized with routine light microscopy and scanning electron microscopic (SEM) analysis. In the second experiment, TiO₂-coated and uncoated discs were implanted subcutaneously into the backs of rats for 14 and 21 days. The discs were pulled out from the implantation sites with a mechanical testing device using a constant speed of 5 mm/min. Rupture force was registered, after which the discs were assigned for SEM and transmission electron microscopic (TEM) analysis. All the coated implants showed immediate contact with the surrounding soft tissues without a clear connective tissue capsule. Significantly better soft tissue response was measured for all the coated compared to the uncoated cylinders (p < 0.01). Higher rupture forces were measured for all coated discs, although the differences were not statistically significant. An immediate and tight connection between connective tissue fibroblasts and coatings was noticed in TEM analysis. Our study indicates that TiO₂ coatings improve soft tissue attachment on a titanium surface.     

Study of growth rate and failure mode of chemically vapour deposited TiN,TiCxNy and TiC on cemented tungsten carbide

The effects of deposition temperature and mole ratio of CH₄ to TiCl₄ on the growth rate of titanium compound coatings were investigated. Activation energies of TiN, TiC _x N _y and TiC deposition reactions of 4.8×10⁴, 1.9×10⁵ and 2.8×10⁵ J mol^–1, respectively, were obtained experimentally. The carbon content of TiC _x N _y deposit was increased as the CH₄ flow rate and deposition temperature increased. It was found that TiC _x N _y grain size was finer than TiC and TiN.The cutting temperatures of TiN-coated and TiC-coated tools were 10% (TiN) and 20% (TiC) lower than that of uncoated tools. Feed force and reaction force of coated tools were 30% and 18% less than those of uncoated tools, respectively. The dominant failure mode of coated tools was due to the microchipping of the cutting edge.     

On Applicability of Multilayer Coated Tool in Dry Machining of Aerospace Grade Stainless Steel

The present research work has been undertaken with a view to investigate the influence of CVD multilayer coated (TiN/TiCN/Al₂O₃/ZrCN) and cutting speed on various machining characteristics such as chip morphology, tool wear, cutting temperature, and machined surface roughness during dry turning of 17-4 PH stainless steel. In order to understand the effectiveness of CVD multilayer coated tool a comparison has been carried out with that of uncoated carbide insert. The surface roughness and cutting temperature obtained during machining with chemical vapor deposition (CVD) multilayer coated tool was higher than that of uncoated carbide insert at all cutting velocity. However, the results clearly indicated that CVD multilayer coated tool played a significant role in restricting various modes of tool failure and reducing chip deformation compared to its uncoated counterpart. Adhesion and abrasion were found to be dominating wear mechanism with flank wear, plastic deformation, and catastrophic failure being major tool wear modes.     

Preparation,characterization and wear behaviour of TiNx-coated cermets obtained by plasma-enhanced chemical vapour deposition

Commercial cermet inserts were coated with titanium nitride by plasma-enhanced chemical vapour deposition (PECVD) using a pulsed direct current (d.c.) glow discharge. The influence of the coating parameters on the deposition rate, on the layer composition, on the layer-substrate interface, on the structure and on the microhardness of the layers was investigated for deposition temperatures in the range 500–700 °C. The adhesive strengths, and some mechanical properties, of the coated cermets were characterized by scratch tests, by friction wear investigations and by measurement of the transverse rupture strength. The wear behaviour was examined in the cutting tests. It was found that TiN _x -coatings deposited with a sufficiently high deposition rate and plasma power density have a low oxygen and chlorine content and that they are nearly stoichiometric. The layers usually have a columnar structure with a 200 texture. A granular, equiaxed structure was observed within a small range of deposition conditions. In interrupted and continuous turning tests with steel and grey cast iron, a high cutting performance of the coated inserts, which depended on the coating thickness and on the deposition temperature, was achieved.