Although nickel-based aerospace superalloys such as alloy 625 have superior properties including high-tensile and fatigue strength, corrosion resistance and good weldability, etc., its machinability ...is a difficult task which can be solved with alternative cooling/lubrication strategies. It is also important that these solution methods are sustainable. In order to facilitate the machinability of alloy 625 with sustainable techniques, we investigated the effect of minimum quantity lubrication (MQL), cryogenic cooling with liquid nitrogen (LN2) and hybrid-CryoMQL methods on tool wear behavior, cutting temperature, surface roughness/topography and chip morphology in a turning operation. The experiments were performed at three cutting speeds (50, 75 and 100 m/min), fixed cutting depth (0.5 mm) and feed rate (0.12 mm/rev). As a result, CryoMQL improved surface roughness (1.42 µm) by 24.82% compared to cryogenic cooling. The medium level of cutting speed (75 m/min) can be preferred for the lowest roughness value and lowest peak-to-valley height when turning of alloy 625. Further, tool wear is decreased by 50.67% and 79.60% by the use of MQL and CryoMQL compared with cryogenic machining. An interesting result that MQL is more effective than cryogenic machining in reducing cutting tool wear.
This paper deals with a comparative study of High-pressure jet, cryogenic, minimum quantity lubrication and minimum quantity lubrication with nanofluid cutting environments during machining of ...Inconel 718 superalloy. Inconel 718 has been chosen for this study because of its wide applications in spacecraft, defense, and energy sectors. The important machining process parameters such as speed, feed, and rake angle have been chosen and their different levels have been used based on tool-work combination. Cutting force, flank wear and surface finish have been analyzed. Additionally, surface defects, surface topography, residual stress on the machined surface and chip morphology have been studied. The results show that the cryogenic environment results in better surface integrity and reduced tool wear during machining of Inconel 718.
Overlapping melting trajectories and partially-melted powders result in poor surface morphology and high surface roughness values (Ra = ~13.34 μm) of selective laser melted (SLMed) Ti6Al4V alloy. ...Secondary processing of SLMed components is thus an essential finishing operation to produce functional SLMed parts in precision engineering. This paper investigates the effects of laser scanning strategies (0°, 67.5° and 90° laser scanning schemes) and machining surfaces (top and front surfaces) on the machining performance of SLMed Ti6Al4V alloy in milling, compared with that of annealed ASTM B265 Ti6Al4V alloy. High degree of anisotropy of SLMed Ti6Al4V alloy is reflected in cutting force, surface morphology and surface roughness on different machining surfaces. The machining anisotropy is dominated by the anisotropy of microstructure and mechanical properties of SLMed Ti6Al4V alloy, where the anisotropy weakens following the sequence of 0°, 90° and 67.5° SLMed samples. It is verified that high cutting speed can improve machining anisotropy features of SLMed titanium alloy. The chip shape of SLMed Ti6Al4V alloy is a typical conical spiral chip, and the bending degree and length of chips produced by SLMed Ti6Al4V alloy are larger than those produced by annealed Ti6Al4V alloy.
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•Grain on top surface of SLMed Ti6Al4V is close to {21¯1¯0} while that on front surface is inclined to {101¯0} and {0001}.•Machining anisotropy is dominated by the anisotropy of microstructure and mechanical properties of SLMed Ti6Al4V alloy.•Surface quality on top surfaces of 0° and 90° SLMed Ti6Al4V is significantly better than that on front surfaces.•The bending degree and length of SLMed Ti6Al4V alloy chips are larger than those of annealed Ti6Al4V alloy.
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•A low cost external spray cooling cryogenic machining setup has been developed.•Studied the turning performance characteristics under cryogenic, dry, wet and MQL machining ...environments.•Improved surface integrity characteristics were found in cryogenic machining.
Nowadays, metal cutting industries are looking towards new sustainable manufacturing methods to reach the target set by the environmentally conscious regulations in terms of usage and disposal of chemical contaminant conventional coolants without sacrificing the productivity. Machining with cryogenic coolants is an efficient, emerging sustainable manufacturing process. In the current work, a low cost external spray cooling cryogenic machining setup has been developed to spray the cryogenic coolant at the machining zone. In the current work, cryogenic coolant (liquid nitrogen) was used to machine the 17-4 precipitated hardenable stainless steel (PH SS) at varying depth of cut conditions and the results were compared with a minimum quantity lubrication (MQL), wet and dry machining environments. The investigative parameters considered in the present study were cutting temperature, tool wear (flank and rake), surface integrity (surface roughness and surface topography) and chip morphology. Cryogenic machining has given beneficial results compared to other machining environments. Hence, cryogenic machining is the most promising technique for machining of 17-4 PH SS. From the health and environmental point of view, cryogenic machining is a clean manufacturing technique.
Magnesium and magnesium in-situ composites have significant potential in the application of design and manufacturing for automotive and aerospace industries because of their high specific strength ...and reduced fuel consumption. But there are many challenges for machining of Mg based alloys and composites because of the high tendency of fire and oxidation. These challenges can be minimized through microstructural engineering. In this present study, the machining performances of AZ91 Mg alloy and in-situ hybrid TiC+TiB2 reinforced AZ91 metal matrix composite was investigated. The effect β-Mg17Al12 phases and grain refinement with and without in-situ particles on machinability were studied through microstructural engineering via aging and friction stir processing. The end milling operation was carried out at different cutting speeds ranging from 25 mm/min to 90 mm/min under dry environment by using an AlTiN-coated tungsten carbide tool. The optimum cutting speed for machining was found to be 75 mm/min based on the surface roughness values of all conditioned materials. The base material with dendritic microstructure was found to have poor machinability in terms of inadequate surface finish and edge-burrs formation. The combined effect of in-situ TiC+TiB2 particles addition and grain refinement enhanced the machining performance of the material with superior surface finish, negligible edge-burr formation and better tool wear resistance. The influence of in-situ TiC+TiB2 particles, β-Mg17Al12 phases and grain refinement on machining characteristics are explained based on the tool wear mechanisms, chip behavior and machining induced affected zone.
The poor thermal conductivity of Inconel 718 leads to higher cutting temperatures and, as a consequence, rapid tool degradation is a common phenomenon. As a result, a hybrid lubri-cooling environment ...for turning Inconel 718 alloys is proposed, incorporating the theory of cryogenic cooling and minimum quantity lubrication (Cryo-MQL). For improved lubri-cooling effect, Cryo-MQL integrates the application of a minimum quantity of vegetable oil and liquid nitrogen from two distinct nozzles in the cutting zone. Surface roughness, cutting temperature, tool wear, chip morphology, and micro-structure of the machined surface were evaluated for different lubri-cooling mediums: dry, MQL, Cryogenic, and Cryo-MQL. In comparison to a dry medium, the Cryo-MQL environment decreases surface roughness, cutting temperature, and tool wear by 60.6%, 37%, and 19.5%, respectively. Adhesion and abrasion were patented to be common tool wear types, as per SEM micro-graphs. Eventually, in the Cryo-MQL environment, a spike in micro-hardness value has been reported. However, during processing with Cryo-MQL, the grain structure of the working material is found to be smaller as compared to other mediums.
•Turning of the aerospace alloy under sustainable lubri-cooling mediums were performed.•Wear tribology of the cutting inserts was investigated using FESEM and EDX.•Microstructure and micro-hardness of the machined surfaces were also examined.•Hybrid cryo-MQL provides significant results.
The present work investigates the effectiveness of micro textures in reducing the sliding friction at the contact surfaces and its application on drill tools for the sustainable machining of ...Ti-6Al-4V. Preliminary experimental results from the pin on disc tests substantiated the tribology enhancing phenomenon of micro textured surfaces, with a better performance in case of micro dimpled surfaces recording a friction coefficient of 0.42. Hence for the first time, an attempt has been made to create micro textures on both the flute and margin side of the drill tools with an objective to minimize the cutting forces by reducing the sliding friction at the tool-chip and tool-work piece interfaces. Micro textures in the form of dimples were created on the flute and margin side of drill tool using laser micromachining technique. Drilling experiments were performed on Ti-6Al-4V work material by drilling a through hole of 10 mm depth using non-textured, flute textured and margin textured tools. From the cutting forces recorded during machining, it was observed that even at the higher cutting speed of 60 m/min and feed 0.07 mm/rev, the margin textured tool performed better than all other tool types recording a net reduction of 10.68% in thrust force and 12.33% in torque compared to non-textured tools. The investigations on the chip morphology further revealed less clogging of chips in case of flute textured tool which is a clear indication of a reduction in the chip evacuation force. The experimental results from this research work proved micro texturing of drill tool to be a viable technique for minimizing the energy loss due to reduction in frictional forces at the cutting regime while machining Ti-6Al-4V.
•Surface texturing was performed to minimize the energy loss due to frictional forces at the contact interfaces.•For the first time micro dimples were created at the flute and margin side of the drill tool using laser micro machining.•Margin textured tool performed better than flute textured and non-textured tool while drilling Ti-6Al-4V.•Chip clogging phenomenon found to be minimized in case of flute textured tools, thereby reducing chip evacuation force.•Surface integrity of the tool and machined surface also got improved while using micro textured drill tools.
Martensitic steels are widely used in many areas such as automotive, mining, and agriculture mostly thanks to their thermal loading ability property. On the other hand, these special steels exhibit ...extreme tool wear tendency and low surface quality which can be associated with abrasive resistance. This situation makes this steel hard-to-cut and requires further investigation with several approaches. Sustainable machining environments are highly effective as modern strategies to improve the machinability index. Also, machine learning models have pivotal role on decreasing the total consumption in the way of lean manufacturing. In the light of above-mentioned information, this work focuses on the machining performances and optimization of dry, flood, and MQL conditions during the milling of Hardox 400 martensitic stainless steel. A novel approach was applied with using several cutting environments and machine learning models to enhance machinability of Hardox which is an industrially important material. Results were analyzed with different machine learning models using heat map and decision trees. Seemingly, cutting fluid assistance in the milling of Hardox steel is critical where flood and MQL provided a considerable effect on the tool wear for reducing it under some level. Also, this technology was found useful in determining the best conditions of machinability in terms of surface roughness, chip morphology, energy consumption, and cutting temperatures. Machine learning models provided hopeful results in analyzing the correlations between parameters used in the model. In machine learning, the heat map being close to 1 and the MSE and MAE values being close to 0 indicated that the model was suitable. This study is expected to observe the contributions of different types of cutting environments to the machinability criteria during milling of industrially important materials.
The present paper addresses an ecological machining method in turning Hastelloy C 276 Nickel alloy under different conditions such as dry, oil with least quantity lubrication (LQL), and ...graphene-based nanofluid LQL (NFLQL) by changing the cutting speed (31, 46, and 62 m/min) and feed rate (0.1, 0.15 and 0.2 mm/rev). Four machining responses were studied namely: surface roughness, tool wear, cutting temperature, and chip thickness. The wettability, pH value, and stability of the nanofluids were assessed prior to the machining process. The output revealed that the usage of NFLQL enhanced the machining performance in contrast to the oil LQL and dry conditions. The average reduction in the surface roughness with NFLQL condition is about 66% compared to dry machining. In addition, NFLQL gives the lowest cutting temperature (40 °C), flank wear (0.053 mm), and chip thickness (0.16 mm) respectively. In a nutshell, the effective cooling and lubrication ability of NFLQL has made significant contributions to smoother machining.
•Cutting performance of Hastelloy C276 superalloy was examined.•Dry, LQL, and NFLQL cutting conditions were tested.•Contact angle, pH value, and stability of the prepared nanofluid were investigated.•Surface roughness, cutting temperature, chip morphology, and tool wear were studied.•The graphene-based nanofluid showed the best performance for all output parameters.
The chip formation for a Ti–6Al–4V alloy was studied at high cutting speeds combined with large uncut chip thicknesses (0.1–0.25mm). Orthogonal cutting tests were conducted by using uncoated carbide ...tools on a specific ballistic set-up with cutting speeds from 300m/min to 4400m/min (5–75m/s). A hypothesis on the mechanism of chip generation is proposed for this speed range validated by high-speed imaging system enabled direct observation of cutting process. A transition, from serrated more or less regular with localized shearing and possible presence of cracking, to discontinuous at very high speed is observed.
The inclination of the segment Φseg is shown as resulting from the primary shear angle Φ that can be modified by compression between the tool and the uncut part. A maximum value of 60° for Φseg is reached with increasing speed after which it decreases to 45° at very high speed.
The cutting speed appears as the most important factor when compared with the uncut chip thickness, in determining the formation of chips by affecting the frequency of segmentation, the shear angles and the crack length.
The significant reduction of cutting forces occurring with increases in cutting speed was firstly explained by the conflicting work hardening–thermal softening processes and then depended on whether the deformation phase of the chip segment is occurred.
► The Ti–6Al–4V alloy is machined with a cutting speed from 300m/min to 4400m/min. ► Orthogonal cutting conditions are realised on a specific ballistic device. ► The different chip morphologies are illustrated and studied. ► The high cutting speed effects on the morphology of the segmented chips are analyzed. ► Mechanisms of chip formation are proposed according to the high cutting speed.
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