Investigations of flank wear, cutting force, and surface roughness in the machining of Al-6061�CTiB2 in situ metal matrix composites produced by flux-assisted synthesis

This paper presents the results of an experimental investigation on the machinability of in situ Al-6061?CTiB₂ metal matrix composite (MMC) prepared by flux-assisted synthesis. These composites were characterized by scanning electron microscopy, X-ray diffraction, and micro-hardness analysis. The influence of reinforcement ratio of 0, 3, 6, and 9?wt.% of TiB₂ on machinability was examined. The effect of machinability parameters such as cutting speed, feed rate, and depth of cut on flank wear, cutting force and surface roughness were analyzed during turning operations. From the test results, we observe that higher TiB₂ reinforcement ratio produces higher tool wear, surface roughness and minimizes the cutting forces. When machining the in situ MMC with high speed causes rapid tool wear due to generation of high temperature in the machining interface. The rate of flank wear, cutting force, and surface roughness are high when machining with a higher depth of cut. An increase in feed rate increases the flank wear, cutting force and surface roughness.     

Study on finish-turning of NiCr20TiAl nickel-based alloy using Al2O3/TiN-coated carbide tools

Al₂O₃/TiN-coated tungsten carbide tools were used for finish-turning of NiCr20TiAl nickel-based alloy under various cutting conditions. The cutting forces, surface integrity, and tool wear were investigated, and their formation mechanisms were discussed. The inter-diffusing and transferring of elements between Al₂O₃/TiN-coated tungsten carbide tool and NiCr20TiAl nickel-based alloy were studied during machining. The plastic flow of NiCr20TiAl alloy was present on the machined surface by the lower cutting forces. The flaking of coating and matrix of tools and the heavier plucking and cavities of the machined surface were induced by the higher cutting forces at higher cutting parameters. The tensile residual stress was engendered on the machined surface and increased with the cutting parameters. In view of surface quality and tool wear, the cutting speed of 60?min and feed of 0.15?mm/r are recommended, and depth of cut should not exceed 0.4?mm when Al₂O₃/TiN-coated carbide tools are used for the finish-turning of the NiCr20TiAl alloy.     

Machining of Titanium Alloy (Ti-6Al-4V)—Theory to Application

This article correlates laboratory-based understanding in machining of titanium alloys with the industry based outputs and finds possible solutions to improve machining efficiency of titanium alloy Ti-6Al-4V. The machining outputs are explained based on different aspects of chip formation mechanism and practical issues faced by industries during titanium machining. This study also analyzed and linked the methods that effectively improve the machinability of titanium alloys. It is found that the deformation mechanism during machining of titanium alloys is complex and causes basic challenges, such as sawtooth chips, high temperature, high stress on cutting tool, high tool wear and undercut parts. These challenges are correlated and affected by each other. Sawtooth chips cause variation in cutting forces which results in high cyclic stress on cutting tools. On the other hand, low thermal conductivity of titanium alloy causes high temperature. These cause a favorable environment for high tool wear. Thus, improvements in machining titanium alloy depend mainly on overcoming the complexities associated with the inherent properties of this alloy. Vibration analysis kit, high pressure coolant, cryogenic cooling, thermally enhanced machining, hybrid machining and, use of high conductive cutting tool and tool holders improve the machinability of titanium alloy.     

Effect of Chilled Air on Machining Performance in End Milling

Flood coolant is customarily used to increase tool life and to improve workpiece surface finish in machining. It is also responsible for some adverse effects on the environment and users’ health, and hence the interest in chilled air assisted machining as an alternative to flood coolant. The effect of chilled air on machining performance was carried out using an end-milling operation on ASSAB 718HH mould steel using uncoated tungsten carbide inserts at different depths of cut, feedrates and cutting speeds under three different lubrication modes, i.e. chilled air, conventional coolant, and dry cutting. The relative performance of these modes is evaluated in terms of tool wear, surface finish, cutting force, and quality of the chips. Lower tool wear was observed using chilled air compared to that for the conventional flood coolant at a lower depth of cut, lower feedrate and lower cutting speed. The surface roughness was found to reduce at higher depths of cut, higher feedrates and higher cutting speeds for chilled air as compared to dry cutting and flood coolant. It is also observed that the cutting force experienced with chilled air is comparable and, in many cases, lower than that when using flood coolant. Stress lines on the chip surfaces show that the chips experienced the highest shear stress in dry cutting, followed by cutting with chilled air and lastly, with flood coolant.     

Performance studies of multilayer hard surface coatings (TiN/TiCN/Al2O3/TiN) of indexable carbide inserts in hard machining: Part-I (An experimental approach)

In recent years, hard machining using CBN and ceramic inserts became an emerging technology than traditional grinding and widely used manufacturing processes. However the relatively high cost factors associated with such tools has left a space to look for relatively low cost cutting tool materials to perform in an acceptable range. Multilayer coated carbide insert is the proposed alternative in the present study due to its low cost. Thus, an attempt has been made to have an extensive study on the machinability aspects such as flank wear, chip morphology, surface roughness in finish hard turning of AISI 4340 steel (HRC 47 ± 1) using multilayer coated carbide (TiN/TiCN/Al₂O₃/TiN) insert under dry environment. Parametric influences on turning forces are also analyzed. From the machinability study, abrasion and chipping are found to be the dominant wear mechanism in hard turning. Multilayer TiN coated carbide inserts produced better surface quality and within recommendable range of 1.6 μm i.e. comparable with cylindrical grinding. At extreme parametric conditions, the growth of tool wear was observed to be rapid thus surface quality affected adversely. The chip morphology study reveals a more favorable machining environment in dry machining using TiN coated carbide inserts. The cutting speed and feed are found to have the significant effect on the tool wear and surface roughness from ANOVA study. It is evident that, thrust force (Fy) is the largest component followed by tangential force (Fz) and the feed force (Fx) in finish hard turning. The observations yield the machining ability of multilayer TiN coated carbide inserts in hard turning of AISI 4340 steel even at higher cutting speeds.     

Modeling and analyzing the effects of air-cooled turning on the machinability of Ti–6Al–4V titanium alloy using the cold air gun coolant system

This study provides the mathematical models for modeling and analyzing the effects of air-cooling on the machinability of Ti–6Al–4V titanium alloy in the hard turning process. A cold air gun coolant system was used in the experiments and produced a jet of compressed cold air for cooling the cutting process. The air-cooling process seems to be a good environment friendly option for the hard turning. In this experimental investigation, the cutting speed, feed rate and cutting depth were chosen as the numerical factor; the cooling method was regarded as the categorical factor. An experimental plan of a four-factor (three numerical plus one categorical) D-optimal design based on the response surface methodology (RSM) was employed to carry out the experimental study. The mathematical models based on the RSM were proposed for modeling and analyzing the cutting temperature and surface roughness in the hard turning process under the dry cutting process and air-cooling process. Tool wear and chip formation during the cutting process were also studied. The compressed cooling air in the gas form presents better penetration of the lubricant to the cutting zone than any conventional coolants in the cutting process do. Results show that the air-cooling significantly provides lower cutting temperature, reduces the tool wear, and produces the best machined surface. The machinability performance of hard turning Ti–6Al–4V titanium alloy on the application of air-cooling is better than the application of dry cutting process. This air-cooling cutting process easily produces the wrinkled and breaking chips. Consequently, the air-cooled cutting process offers the attractive alternative of the dry cutting in the hard turning process.     

Evaluation on Effectiveness of CVD and PVD Coated Tools during Dry Machining of Incoloy 825

With wide applications of nickel-based superalloys in strategic fields, it has become increasingly necessary to evaluate the performance of different advanced cutting tools for machining such alloys. With a view to recommend a suitable cutting tool, the present work investigated various machinability characteristics of Incoloy 825 using an uncoated tool, chemical vapor deposition (CVD) of a bilayer of TiCN/Al₂O₃, and physical vapor deposition (PVD) of alternate layers of TiAlN/TiN-coated tools under varying machining conditions. The influence of cutting speed (51, 84, and 124 m/min) as well as feed (0.08, 0.14, and 0.2 mm/rev) was comparatively evaluated on surface roughness, cutting temperature, cutting force, coefficient of friction, chip thickness, and tool wear using different cutting tools. Although the CVD-coated tool was not useful in decreasing surface roughness and temperature, a significant reduction in cutting force and tool wear could be achieved with the same coated tool under a high cutting speed of 124 m/min. On the other hand, the PVD-coated tool outperformed the other tools in terms of machinability characteristics. This might be attributed to the excellent antifriction and antisticking property of TiN and good toughness due to the multilayer configuration in combination with a thermally resistant TiAlN phase. Adhesion, abrasion, edge chipping, and nose wear were the prominent wear mechanisms of the uncoated tool, followed by the CVD-coated tool. However, remarkable resistance to such wear was evident with the PVD TiAlN/TiN multilayer-coated tool.     

Some studies on hard turning of AISI 4340 steel using multilayer coated carbide tool

Hard turning with multilayer coated carbide tool has several benefits over grinding process such as, reduction of processing costs, increased productivities and improved material properties. The objective was to establish a correlation between cutting parameters such as cutting speed, feed rate and depth of cut with machining force, power, specific cutting force, tool wear and surface roughness on work piece. In the present study, performance of multilayer hard coatings (TiC/TiCN/Al₂O₃) on cemented carbide substrate using chemical vapor deposition (CVD) for machining of hardened AISI 4340 steel was evaluated. An attempt has been made to analyze the effects of process parameters on machinability aspects using Taguchi technique. Response surface plots are generated for the study of interaction effects of cutting conditions on machinability factors. The correlations were established by multiple linear regression models. The linear regression models were validated using confirmation tests. The analysis of the result revealed that, the optimal combination of low feed rate and low depth of cut with high cutting speed is beneficial for reducing machining force. Higher values of feed rates are necessary to minimize the specific cutting force. The machining power and cutting tool wear increases almost linearly with increase in cutting speed and feed rate. The combination of low feed rate and high cutting speed is necessary for minimizing the surface roughness. Abrasion was the principle wear mechanism observed at all the cutting conditions.     

Wear and Tribological Performance of Different Ceramic Tools in Dry High Speed Machining of Ni-Co-Cr Precipitation Hardenable Aerospace Superalloy

Tool wear is an important machinability criterion. To reduce total machining costs, this study demonstrates the wear and tribological performance of four ceramic tools in dry high-speed turning of Ni-Co-Cr precipitation hardenable superalloy (Inconel 100). Wear of the tool materials and the structural and phase transformations at the tool–chip interface were investigated. Results obtained reveal that SiAlON ceramic outperformed other ceramic tool materials at different cutting speeds due to the formation of a large amount of mullite tribofilms on the tool face, which serve as a thermal barrier layer. Alumina ceramic with the addition of ZrO₂ can be recommended for machining Inconel 100 at speeds above 150 m/min due to its ability to form thermal barrier ZrO₂ tribofilms, which decrease the coefficient of friction at the tool–chip interface. Mixed alumina and an alumina matrix reinforced with SiC_w were found to be unsuitable for machining age-hardened Inconel 100 superalloy.     

Influence of minimum quantity lubrication parameters on tool wear and surface roughness in milling of forged steel

The minimum quantity of lubrication (MQL) technique is becoming increasingly more popular due to the safety of environment.Moreover,MQL technique not only leads to economical benefits by way of saving ...     

Effect of very high cutting speeds on shearing, cutting forces and roughness in dry turning of austenitic stainless steels

Behavior of austenitic stainless steels has been studied at very high cutting speeds. Turning tests were carried out using the AISI 303 austenitic stainless steel. In particular, the influence of cutting speed on tool wear, surface quality, cutting forces and chip geometry has been investigated. These parameters have been compared when performing machining at traditional cutting speeds (lower than 350?m/min) versus high cutting speeds. The analysis of results shows that the material undergoes a significant change in its behavior when machining at cutting speeds above 450?m/min, that favors the machining operation. The main component of cutting forces reaches a minimum value at this cutting speed. The SEM micrographs of the machined surfaces show how at the traditional cutting speeds the machined surfaces contain cavities, metal debris and feed marks with smeared material particles. Surfaces machined at high cutting speeds show evidence of material side flow, which is more evident at cutting speeds above 600?m/min. Tool wear is located at the tool nose radius for lower cutting speeds, whereas it slides toward the secondary edge when cutting speed increases. An analysis of chips indicates also an important decrement in chip thickness for cutting speeds above 450?m/min. This study concludes that there is an unexplored range of cutting speeds very interesting for high-performance machining. In this range, the behavior of stainless steels is very favorable although tool wear rate is also significant. Nevertheless, nowadays the cost of tool inserts can be considered as secondary when comparing to other operation costs, for instance the machine hourly cost for high-end multitasking machines.     

Machinability of Elongated Coarse Grain Fe-Based Superalloys

□ In conventional metal cutting process, materials are assumed to be homogeneous and isotropic structure. However, some materials with a single crystal or coarse elongated polycrystalline demonstrate strong anisotropic behavior in physical and mechanical properties in machining of some superalloy materials. The anisotropic structure always leads to variation at machinability properties of the material. In this study, machinability properties of ferritic superalloy PM2000, which had elongated a few coarse grains, were investigated. These properties were determined by investigation of chip formation, cutting forces and surface roughness. Machinability was assessed by single-point turning on a CNC lathe and turning forces were measured by using a Kistler Lathe Dynamometer. The chip formation mechanisms in machining of PM2000 at various cutting speeds were determined by using a quick-stop device (QSD). Chip roots and machined surfaces were analyzed by means of scanning electron microscopy (SEM). The results indicated that the machinability properties of the PM2000 were changed by orientated coarse grain structure. Three types chip formation mechanism were determined at the same cutting conditions. Also, surface roughness on the machined each grain changed with changing the grain to be cut. Surface roughness and force fluctuations decreased with increasing the cutting speed; however, tool wearing increased.     

Turning titanium metal matrix composites (Ti-MMCs) with carbide and CBN inserts

Despite excellent mechanical and physical features of titanium metal matrix composite (Ti-MMC), hard and abrasive ceramic particles within the matrix structure, as well as high price, may lead to severe difficulties on machining and machinability of Ti-MMCs. Review of literature denotes that only limited studies are available on machining Ti-MMCs with commercial cutting tools under various cutting conditions and cutting tools/inserts. Furthermore, limited studies are available on machinability attributes of Ti-MMC under various cutting conditions used. Therefore, to remedy the lack of knowledge observed, this work intends to report turning Ti-MMCs with carbide, and cubic boron nitride (CBN) inserts under various cutting conditions. The mean values of surface roughness (R_a) and directional cutting forces, as well as flank wear (V_B) were studied as the machinability attributes. The microstructural evaluations were conducted to discover the wear modes. Furthermore, the statistical tools were used to present the factors governing machining attributes studied. Adhesion, abrasion, and oxidation were observed as the principle wear modes on the flank sides of the tested inserts. According to experimental results and statistical analysis, the R_a and V_B could be controlled by cutting parameters only when CBN inserts were used. Despite the inset used, factors governing both responses were not identical. Although average cutting forces were directly affected by cutting parameters used, however, the relatively low correlation of determination (R²) of directional cutting forces can be attributed to effects of cutting speed, elevated temperature in the cutting zone as well as rapid tool wear which are all correlated to others.     

An investigation on wear mechanism of high-speed turning of free-cutting steel AISI 1215 using uncoated and multi-layer coated tools

AISI 1215 is a new kind of green and non-toxic free-cutting steel with minimum environmental pollution and excellent machinability, which receives wide promotion, investigation, and application in manufacturing industries. In machining of AISI 1215 steel, tool wear has a close relation with the presence of manganese sulfide lubricant zone formed on the tool surface. In this work, with the aid of cutting temperature and tool Von Mises stress simulations, tool wear analysis on the uncoated and multi-layer (Al₂O₃/TiCN) coated carbide tools was performed in high-speed turning operation. Wear pattern and wear mechanisms were studied through the experimental results. The main findings showed that the uncoated tool suffered high cutting temperature and severe tool wear and was not conducive to form a manganese sulfide lubricant zone in the turning operation. In contrast, the multi-layer coated tool could form a manganese sulfide lubricant zone on the chip–tool contact area. The beneficial roles of the manganese sulfide lubricant zone formed on the coated tool surface can be summarized as lubrication and diffusion blocking. The main wear mechanisms of the uncoated tool were crater wear, oxidation wear, adhesive wear, and abrasive wear, whereas for the multi-layer coated tool, they were crater wear, adhesive wear, and abrasive wear.     

Experimental investigations on machinability aspects in finish hard turning of AISI 4340 steel using uncoated and multilayer coated carbide inserts

The present work deals with some machinability studies on flank wear, surface roughness, chip morphology and cutting forces in finish hard turning of AISI 4340 steel using uncoated and multilayer TiN and ZrCN coated carbide inserts at higher cutting speed range. The process has also been justified economically for its effective application in hard turning. Experimental results revealed that multilayer TiN/TiCN/Al₂O₃/TiN coated insert performed better than uncoated and TiN/TiCN/Al₂O₃/ZrCN coated carbide insert being steady growth of flank wear and surface roughness. The tool life for TiN and ZrCN coated carbide inserts was found to be approximately 19 min and 8 min at the extreme cutting conditions tested. Uncoated carbide insert used to cut hardened steel fractured prematurely. Abrasion, chipping and catastrophic failure are the principal wear mechanisms observed during machining. The turning forces (cutting force, thrust force and feed force) are observed to be lower using multilayer coated carbide insert in hard turning compared to uncoated carbide insert. From 1st and 2nd order regression model, 2nd order model explains about 98.3% and 86.3% of the variability of responses (flank wear and surface roughness) in predicting new observations compared to 1st order model and indicates the better fitting of the model with the data for multilayer TiN coated carbide insert. For ZrCN coated carbide insert, 2nd order flank wear model fits well compared to surface roughness model as observed from ANOVA study. The savings in machining costs using multilayer TiN coated insert is 93.4% compared to uncoated carbide and 40% to ZrCN coated carbide inserts respectively in hard machining taking flank wear criteria of 0.3 mm. This shows the economical feasibility of utilizing multilayer TiN coated carbide insert in finish hard turning.     

Evaluation of the performance of coated carbide tools in face milling TC6 alloy under dry condition

Titanium and its alloys are well known as the typical different-to-cut materials because of their low thermal conductivity, high chemical reactivity, and low modulus of elasticity. During machining of titanium alloy, advanced high-speed, high-efficiency processing technologies are adopted to improve the production efficiency and reduce the production costs. The main goal of this work is to compare the performance of physical vapor deposition (PVD)-coated (TiN/TiAlN) and chemical vapor deposition (CVD)-coated (TiN/Al₂O₃/TiCN) carbide inserts in face milling TC6 alloy. To this end, the present paper reviewed the main works on the application of PVD- and CVD-coated tools in machining titanium alloys and the material performance of TC6 alloy, especially the machinability in machining process. Several tool life tests and tool wear experiments were carried out on a milling center with a five-axis spindle drive. Cutting forces were measured with a Kistler dynamometer. The failure modes and chip morphology were observed. Surface roughness and tool wear evolution were determined. The wear mechanism was discussed to compare the performance of PVD and CVD-coated tools. The main conclusions of this work were that the cutting tools made with PVD coating (TiN/TiAlN) had the excellent tooling quality and the main wear mechanisms were spalling and adhesion. PVD-TiN/TiAlN insert was more suitable to milling TC6 alloy than CVD-TiN/Al₂O₃/TiCN insert.     

Evaluating the effect of coolant pressure and flow rate on tool wear and tool life in the steel turning operation

High-pressure coolant (HPC) delivery is an emerging technology that delivers a high-pressure fluid to the tool and workpiece in machining processes. High fluid pressure allows for better penetration of the fluid into the cutting zone, enhancing the cooling effect, and decreasing tool wear through lubrication of the contact areas. The main objective of this work is to understand how tool wear mechanisms are influenced by fluid pressure under different cutting speeds in the finish turning of AISI 1045 steel using coated carbide tools. The main finding was that the use of a lower cutting speed (v _c ?=?490 m/min) in dry cutting resulted in tool life close to that obtained with cutting fluid, but when the cutting speed was increased (v _c ?=?570 m/min), the high-pressure coolant was effective in prolonging the life of the cutting tool. It was also concluded that, regardless of the cutting speed and cooling/lubrication system, the wear mechanisms were the same, namely abrasion and attrition.     

WEAR PERFORMANCE OF MULTILAYER-COATED CARBIDE TOOLS

Three multilayer-coated carbides [two trigon-shaped inserts: Ti(C,N)/TiC/Al₂O₃ (T1), Ti(C,N)/ Al₂O₃/TiN (T2) and one 80°-rhomboid shaped insert: TiC/Al₂O₃/TiN (T3)] were used to machine a martensitic stainless steel at various combinations of cutting speed and feed rate without coolant to assess their wear performance. Significant nose wear and chipping/fracture of the cutting edge were the predominant failure modes affecting tool performance at higher speed conditions. Plucking of tool materials was the main rake face wear phenomenon observed on T1 grade insert with alumina as the top-layer coating when machining at the lower speed conditions. Attrition and plastic flow were the main wear mechanisms observed on the ceramic coating layers, with dissolution-diffusion being the probable wear mechanism of the tool grades where tungsten carbide substrate had direct contact with the flowing chip. The fitted statistical wear models revealed T3 grade insert with 80°-rhomboid shape as having the highest speed-feed capability, resulting in the highest material removal rate relative to T1 and T2 grade inserts with trigon shapes.     

The Effect of Argon-Enriched Environment in High-Speed Machining of Titanium Alloy

A major factor hindering the machinability of titanium alloys is their tendency to react with most cutting tool materials, thereby encouraging solution wear during machining. Machining in an inert environment is envisaged to minimize chemical reaction at the tool-chip and tool-workpiece interfaces when machining commercially available titanium alloys at higher cutting conditions. This article presents the results of machining trials carried out with uncoated carbide (ISO K10 grade) tools in an argon-enriched environment at cutting conditions typical of finish turning operations. Comparative trials were carried out at the same cutting conditions under conventional coolant supply. Results of the machining trials show that machining in an argon-enriched environment gave lower tool life relative to conventional coolant supply. Nose wear was the dominant tool-failure mode in all the cutting conditions investigated. Argon is a poor conductor of heat; thus, heat generated during machining tends to concentrate in the cutting region and accelerate tool wear. Argon also has poor lubrication characteristics, leading to increasing friction at the cutting interfaces during machining and an increase in cutting forces required for efficient shearing of the workpiece.     

An experimental study on the ultrasonic machining characteristics of engineering ceramics

Engineering ceramics have many unique characteristics both in mechanical and physical properties such as high temperature hardness, high thermal, chemical and electrical resistance. However, its machinability is very poor in conventional machining due to its high hardness and severe tool wear. In the current experimental study, alumina (Al₂O₃) was ultrasonically machined using SiC abrasives under various machining conditions to investigate the material removal rate and surface quality of the machined samples. Under the applied amplitude of 0.02 mm, 27 kHz frequency, three slurry ratios of 1:1, 1:3 and 1:5 with different tool shapes and applied static pressure levels, the machining was conducted. Using the mesh number of 240 abrasive, slurry ratio of 1:1 and static pressure of 2.5 kg/cm², maximum material removal rate of 18.97 mm³/min was achieved. With mesh number of 600 SiC abrasives and static pressure of 3.0 kg/cm², best surface roughness of 0.76 pm Ra was obtained.