Effect of Graphene Addition in Cutting Fluids Applied by MQL in End Milling of AISI 1045 Steel

The cutting fluids applied to the machining processes by the MQL process aim to reduce the machining temperatures and tool wear as well as improve the surface and dimensional finishing of the parts. To increase the efficiency of these fluids, graphene lubricating platelets are added. This work investigated the performance of three different cutting fluids with graphene sheets added and applied via MQL, considering the tool life, wear, and wear mechanisms acting on TiAlN-coated cemented carbide cutting tools in the end milling of AISI 1045 steel. We evaluated two vegetable- (MQL15 and LB1000) and one mineral-based (MQL14) neat oils and the same fluids with the addition of 0.05 and 0.1%wt graphene nanoplatelets. Dry cuts were also performed and investigated for comparison. The experiments were conducted under fixed cutting conditions (vc = 250 m/min, fz = 0.14 mm/tooth, ap = 1 mm, and ae = 20 mm). The end-of-tool-life criterion followed the guidelines of ISO 8688-1 (1989). To analyze the results, ANOVA and Tukey’s test were applied. The addition of graphene sheets in the vegetable-based cutting fluids effectively increased the lubricating properties, partially reducing the wear mechanisms acting on the tools. In addition, there was a predominance of thermal fatigue cracks and mechanical cracks as well as adhesive and abrasive wear mechanisms on the tools used in the cutting with the MQL15 and MQL14 fluids, indicating greater cyclical fluctuations in temperature and surface stresses.

Machining Temperature and Accuracy of Magnesium Alloy AZ31 with Deep-Hole Small Drilling

In recent years, magnesium-based materials have become expected to replace conventional engineering plastics as next-generation industrial materials to protect the global environment. However, in the production technology, problems of cracking and unstable accuracy in drilled hole shapes persist in plastic molding and machine tool processing; many studies have been conducted to address these problems. In dry machining ignition can be caused by the material, so wet machining is the prevalent method. However, it is necessary to establish a machining method with improved environmental parameters, considering the impact of oil mist and waste oil treatment on woks. In this study, the relationship between machining temperature and the accuracy of hole shapes in magnesium alloy AZ31 is investigated with four types of drills: high-speed steel, cemented carbide (K-Base), diamond-like carbon (DLC; K-Base), and TiN-coated cemented carbide (K-Base). The drill tip angle is set to 116°, 118°, or 120°. The work material used is the extruded AZ31 magnesium alloy. To evaluate the hole shape accuracy, squares of 80 × 80 mm are used. The cutting temperature is measured over an area of 12 × 30 mm. The work material is drilled using a dry method with a 3-mm-diameter drill having the aspect ratio (L/D) of 10. The tool protrusion length of 50 mm and cutting speed of 20 m/min are fixed, and the tool feed rate and drill step amount are changed. The experiment is repeated 3 times. The burr generated around the loophole on the back surface of the test material after the test is evaluated with a criterion burr height H of 0.02 mm. Furthermore, the average roughness (Ra) of the centerline is measured on the inner surface of the hole with a contact-type roughness meter. The results show that when using the three drill point angles of 116°, 118°, and 120° in the drill step, no burrs form at the exit of the drill hole. Carbide tools form burrs when the feed rate exceeds 30 mm/min and the step amount exceeds 20 mm. TiN tools are highly accurate up to a tip angle of 118°, while DLC tools have lower cutting forces and yield better finished surfaces than the other tools.

Performance Study of Cryo-Treated End Mill Via Wet, Cryogenic, and Hybrid Lubri-Coolant-Milling Induced Surface Integrity of Biocompatible Mg Alloy AZ91D

The excellent biodegradability of the magnesium (Mg) alloys is gradually proving them as the potential substitutes to several biomedical implants such as chemotherapy ports or screws, which are required to be removed via secondary surgeries after a specific period of time. However, an early degradation of these alloys even before the complete healing of the damaged tissue, when exposed to the physiological atmosphere, has been limiting their full-fledged application. Some latest research articles suggest that such challenges can be effectively overcome by improving the surface integrity of Mg alloys using the sustainable manufacturing techniques, such as cryogenic machining. Recent literatures also report the outperformance of the cryogenically treated (cryo-treated) cutting tools for achieving an enhanced surface integrity. In this relation, the present research attempts to improve the surface integrity of one of the most commonly used biocompatible alloys of magnesium, known as AZ91D. For this reason, a TiAlN coated-cemented carbide end mill was used in an untreated and cryo-treated state amid wet, cryogenic, and hybrid-lubri-coolant-milling conditions. The milling and FESEM (field emission scanning electron microscopy) results showed a considerable improvement in the surface integrity in terms of an augmented surface roughness and microhardness at 56.52 m/min cutting speed with the cryo-treated end mill during hybrid-lubri-coolant-milling. At the high cutting speed hybrid-lubri-coolant-milling, the cryo-treated end mill attained 35.71% and 48.07% better surface finish than that of cryo and wet-lubri-coolant-milling, respectively. Although, the highest surface microhardness was achieved by the cryo-treated end mill amid cryo-lubri-coolant-milling, due to the poorest surface quality observed in terms of the maximum number of machining-induced cracks, the hybrid-lubri-coolant-milled surface was preferred over the cryo and wet-lubri-coolant-milled surfaces. Further, the FESEM and EDS (energy-dispersive X-ray spectroscopy) analyses confirmed the oxide layer produced by the cryo-treated end mill amid hybrid-lubri-coolant-milling, to be the thinnest (12.16 µm) and most uniform passivation layer.

OPTIMIZATION OF TURNING PROCESS PARAMETER FOR LATHE MACHINE BY USING TAGUCHI METHOD.

In this project attempts on optimizing the turning process under various machining parameters by Taguchi method to develop or implement the quality of machined product. Taguchi optimization methodology is applied to optimize cutting parameters in turning EN 8, steel with coated cemented carbide tool under dry cutting condition. The center lathe machine is used to conduct experiments based on the Taguchi design of experiments (DOE) with orthogonal L9 array. The orthogonal array, signal to noise ratio (S/N) and were employed to Experiments conducted and subsequently analysis performed by using the Taguchi method. The optimum characteristics for high hardness in turning operation are identified. From the response graph plotted between turning parameters and hardness of EN 8, it is observed that there is increase in hardness as the speed is increased at 850 rpm but when speed is further increased hardness goes decreased. The hardness increases when feed rate is changed from 0.2 mm/rev to 0.3 mm/rev and 0.3 to 0.4 mm/rev, but when depth of cut is 1 mm then hardness increases, but as the depth of cut is further increased then hardness decrease considerably.

Wear and Fatigue Behavior of PVD and MTCVD TiCN Coated Cemented Carbide Inserts in Turning Cast Iron

TiCN coatings of the same chemical compositions were deposited on HW/K05-K20 cemented carbide inserts via physical (PVD) and medium temperature chemical vapor deposition (MTCVD) techniques. Nano-indentations coupled with appropriate FEM simulations were used for characterizing the film and substrate mechanical properties. Furthermore, uncoated cemented carbide substrates were annealed in vacuum at temperatures and durations corresponding to the related ones during the PVD and MTCVD process for recording the effect of the deposition temperature and duration on the substrate strength properties. Perpendicular and inclined impact tests at various loads were performed for checking the coating fatigue endurance and adhesion respectively. These material data were considered in FEM supported calculations for predicting the developed stress fields in the cutting edge during turning cast iron GG30 using the PVD and MTCVD TiCN coated inserts. According to the obtained result, both coatings possess the same stress-strain properties. Hereupon, the MTCVD coatings are characterized comparably to PVD ones by improved fatigue properties and adhesion strength. Although these properties contribute to an increased tool life in finishing turning, the significant reduction of the substrate strength properties, due to the elevated temperature during the MTCVD process, results in a premature coating failure and a consequent intensive wear evolution in roughing.