Experimental investigations on cryogenic cooling by liquid nitrogen in the end milling of hardened steel

Milling of hardened steel generates excessive heat during the chip formation process, which increases the temperature of cutting tool and accelerates tool wear. Application of conventional cutting fluid in milling process may not effectively control the heat generation also it has inherent health and environmental problems. To minimize health hazard and environmental problems caused by using conventional cutting fluid, a cryogenic cooling set up is developed to cool tool–chip interface using liquid nitrogen (LN₂). This paper presents results on the effect of LN₂ as a coolant on machinability of hardened AISI H13 tool steel for varying cutting speed in the range of 75–125 m/min during end milling with PVD TiAlN coated carbide inserts at a constant feed rate. The results show that machining with LN₂ lowers cutting temperature, tool flank wear, surface roughness and cutting forces as compared with dry and wet machining. With LN₂ cooling, it has been found that the cutting temperature was reduced by 57–60% and 37–42%; the tool flank wear was reduced by 29–34% and 10–12%; the surface roughness was decreased by 33–40% and 25–29% compared to dry and wet machining. The cutting forces also decreased moderately compared to dry and wet machining. This can be attributed to the fact that LN₂ machining provides better cooling and lubrication through substantial reduction in the cutting zone temperature.     

Experimental Study of Surface Roughness and Tool Flank Wear during Hybrid Milling

Two advanced machining methods such as thermally enhanced machining and ultrasonic-assisted machining are recently considered in many studies. In this article, a new hybrid milling process is presented by gathering the characteristics of these two methods. In order to determine the axial depth of cut and engagement in the process, three-dimensional thermal finite-element analysis is applied to determine the dimensions of softened materials. Finite-element modal analysis is used to determine the dimensions and clamping state of the workpiece while cutting area has the highest vibration amplitude. Full factorial experimental design is applied to investigate the effect of hybrid machining parameters on the surface roughness and tool wear. Tool flank wear was investigated under the condition of constant cutting speed during different period of times. Hybrid milling process with an amplitude of 6 µm and a temperature of 900°C creates a surface with 42% lower roughness in comparison to conventional milling in feed 0.08 mm/tooth. In a study of tool flank wear, the results show that application of TEUAM decreases flank wear at least 16% in comparison to all other processes.     

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.     

Comparison of tool life and surface characteristics of uncoated,coated carbide and ceramic tools during machining of SiC reinforced ZA43 alloy MMC

Abstract

In the present investigation, machinability issues of zinc–aluminium (ZA43) alloy reinforced with silicon carbide particles (SiC) were evaluated. The fabrication of composite was done through liquid metallurgy technique. Metal matrix composite (MMC) was subjected to turning using conventional lathe with three grades of cutting tools, namely, uncoated carbide tool, coated carbide tool and ceramic tool. Surface roughness and tool wear were measured during the machining process. Results reveal that roughness increases with increase in the reinforcement concentration and particle size. Feed has direct influence on roughness, i.e. surface deteriorates with higher feeds. Depth of cut has very minimum effect on the surface roughness, while inverse effect of cutting speed on the roughness was observed (i.e. increase in the cutting speed leads to better finish on the specimen). Tool wear was studied during the investigation, and it was noticed that MMC with higher reinforcement concentration and particle size cause severe wear on the flank of the cutting tool. Increase in the cutting speed, feed and depth of cut also increases the flank wear on the tool. Out of all the three grades of tools, coated carbide tool outperformed uncoated carbide and ceramic tools.     

Experimental Study on Hybrid Cryogenic and Plasma-Enhanced Turning of 17-4PH Stainless Steel

This article presents machinability of 17-4PH stainless steel using a hybrid technique composed of plasma-enhanced turning and cryogenic turning. First of all, using some primary experimental tests and nonlinear regression, a mathematical model was developed for surface temperature of uncut chip as a function of plasma current and cutting parameters. Then, the influence of cutting speed (V_c), feed (f), and surface temperature of uncut chip (T_sm) was studied on surface roughness (R_a), cutting force (F_z), and tool flank wear (V_B). The results show that hybrid turning (HYT) is able to lower the main cutting force and tool flank wear in comparison with conventional turning. In addition, surface roughness was improved except for high level of surface temperature of uncut chip. However, hardness measurement of machined workpiece showed that HYT does not change the hardness of machined surface.     

Environment Friendly Machining of Ni–Cr–Co Based Super Alloy using Different Sustainable Techniques

In order to eradicate the use of mineral based cutting fluid, the machining of Ni–Cr–Co based Nimonic 90 alloy was conducted using environment friendly sustainable techniques. In this work, uncoated tungsten carbide inserts were employed for the machining under dry (untreated and cryogenically treated), MQL, and cryogenic cutting modes. The influence of all these techniques was examined by considering tool wear, surface finish, chip contact length, chip thickness, and chip morphology. It was found that the cryogenically treated tools outperformed the untreated tools at 40 m/min. At cutting speed of 80 m/min, MQL and direct cooling with liquid nitrogen brought down the flank wear by 50% in comparison to dry machining. Similarly at higher cutting speed, MQL and cryogenic cooling techniques provided the significant improvement in terms of nose wear, crater wear area, and chip thickness value. However, both dry and MQL modes outperformed the cryogenic cooling machining in terms of surface roughness value at all the cutting speeds. Overall cryotreated tools was able to provide satisfactory results at lower speed (40 m/min). Whereas both MQL and cryogenic cooling methods provided the significantly improved results at higher cutting speeds (60 and 80 m/min) over dry machining.     

Magnetorheological fluid-based nanotexturing of tool inserts for turning of duplex stainless steel

This paper deals with the study of the nanotexturing process of the cutting tool inserts with the influence of a magnetorheological fluid-based texturing method. The rake and flank surface of the cutting tool inserts were finished with a silicon carbide abrasive mixture of a magnetorheological fluid. Experimentation is conducted with input variables such as voltage, gap width, and polishing time to achieve the desired value of % reduction of surface roughness, polishing rate, andpolishing time. The surface roughness is found to be less than 40?nm for textured and 120?nm for non-textured inserts with a lesser polishing time. A higher polishing rate of the cutting tool inserts is achieved at a working voltage of 36?V and a gap width of 0.75?mm. The machinability characteristics of the nanotextured inserts are based on the cutting force; tool wear is studied for the turning operation of Duplex stainless steel. The tool flank wear is observed to be 0.63?mm, after 13th pass when turned with an unpolished insert and 0.612?mm after the 19th pass with a polished insert. From the results, it is found that the nanotextured inserts could achieve a tool life of 60% higher than the un-textured inserts in machining the duplex stainless steel.     

Effect of machining parameters on turning of VAT32® superalloy with ceramic tool

The objective of this research was to study the machining of superalloy VAT32® using alumina-based ceramic tool without cutting fluid, applying different machining parameters to evaluate the surface finish of parts, vibration and main wear of tools. For this, a turning process with a linear trajectory of 30 mm was performed, in which were collected data vibration and surface roughness of the stretch, as well as wear and damage in the tools. The turning tests were performed utilizing cutting speeds of 270, 280 and 300 m/min, a feed of 0.10, 0.18 and 0.25 m/rev and a cutting depth of 0.50 mm. With results, it was identified that the feed influenced significantly both the vibration and the system, since the cutting speed influenced only the vibration. Being that the best results happened for the smaller feed and greater cutting speed. It concludes that the machining of superalloy VAT32® with ceramic tool introduced herself promising.     

Effects of vegetable-based cutting fluids on the wear in drilling

This study focuses on both formulation of vegetable-based cutting fluids (VBCFs) and machining with these cutting fluids. For this purpose, characterizations of chemical and physical analyses of these formulated cutting fluids are carried out. In this study, performances of three VBCFs developed from crude sunflower oil, refined sunflower oil, refined canola oil and commercial semi-synthetic cutting fluid are compared in terms of tool wear, thrust force and surface roughness during drilling of AISI 304 austenitic stainless steel with HSSE tool. Experimental results show that canola-based cutting fluid gives the best performance due to its higher lubricant properties with respect to other cutting fluids at the constant cutting conditions (spindle speed of 750 rpm and feed rate of 0.1 mm/rev).     

Tribological property and drilling application of Ti-C:H and Cr-C:H coatings on high-speed steel substrates

This study investigates the tribological properties and cutting performance of Ti-DLC and Cr-DLC doped metal coatings. The tribological properties of the coatings are evaluated by testing coated disks against an AISI 1045 steel counterbody under dry conditions using an oscillating friction wear tester, and then measuring the subsequent wear depth on the coated disk, the wear width on the steel counterbody, and the friction coefficient. The cutting performance of the coatings is evaluated by using coated high-speed drills to machine stainless steel workpieces, and then measuring the resulting flank wear and hole surface roughness. The results of the wear tests show that the Ti-C:H and Ti-C:H/TiC/TiCN/TiN coatings possess excellent tribological properties, including low coefficients of friction, low wear depths, and low wear widths. Regarding the machining tests, the Ti-C:H/TiC/TiCN/TiN coating has the lowest flank wear and yields the highest hole surface quality under both dry and cutting fluid drilling conditions. The single Ti-C:H coating has excellent tribological properties, but demonstrates a relatively poorer performance in the drilling of stainless steel. Finally, the Cr-DLC coatings all exhibit a poor cutting performance under dry cutting conditions.     

Fuzzy Modeling and Analysis of Machining Parameters in Machining Titanium Alloy

Titanium alloys are utilized in many engineering fields such as chemical, industrial, marine, and aerospace due to their unique properties. Machining of these materials causes severe problems. At high temperatures, they become chemically active and tend to react with tool materials. In the present study, fuzzy logic (a tool in artificial intelligence) is used for the prediction of cutting parameters in turning titanium alloy (Ti-6Al-4V). The parameters considered in this study are cutting speed, feed, and the depth of cut. Fuzzy rule-based modeling is employed for prediction of tool flank wear, surface roughness, and specific cutting pressure in machining of titanium alloy. These models can be effectively used to predict the tool flank wear, surface roughness, and specific cutting pressure in machining of titanium alloys. Analysis of the influences of the individual important machining parameters on the responses have been carried out and presented in this study.     

Cryogenic turning of the Ti–6Al–4V alloy with modified cutting tool inserts

Productivity in the machining of titanium alloys is adversely affected by rapid tool wear as a consequence of high cutting zone temperature. Conventional cutting fluids are ineffective in controlling the cutting temperature in the cutting zone. In this research work, an attempt has been made to investigate the effect of liquid nitrogen when it is applied to the rake surface, and the main and auxiliary flank surfaces through holes made in the cutting tool insert during the turning of the Ti–6Al–4V alloy. The cryogenic results of the cutting temperature, cutting forces, surface roughness and tool wear of the modified cutting tool insert have been compared with those of wet machining. It has been observed that in the cryogenic cooling method, the cutting temperature was reduced by 61–66% and the surface roughness was reduced to a maximum of 36% over wet machining. The cutting force was decreased by 35–42% and the flank wear was reduced by 27–39% in cryogenic cooling over that of wet machining. Cryogenic cooling enabled a substantial reduction in the geometry of tool wear through the control of the tool wear mechanisms. The application of liquid nitrogen to the heat generation zones through holes made in the cutting tool insert was considered to be more effective over conventional machining.     

Investigation on tool wear process of milling wave-transmitting Si3N4 ceramics

Due to the low fracture toughness of wave-transmitting Si₃N₄ ceramics, the special material removal mechanism causes the tool wear to be different. The paper presents the tool wear forms and mechanism under different milling depth. The effect of tool wear on cutting force and machined surface morphology is discussed. Tests have been performed under typical conditions of cutting depth of 0.3 mm (in plastic-domain processing) and 0.4 mm (in brittle-domain processing). The results show that the abrasive wear caused by the chips is the main mechanism of the cutting edge wear and the flank wear, the increase of the side edge rear angle with tool wear is the main cause of the chipping phenomenon. The cutting depth is a significant influence parameter to the wear characteristics, and two types have been distinguished. As the material removal volume ascending, the cutting edge wear and the flank face wear has a stable period, and the root-mean-square deviation of processing surface increases to 1.6 μm, while that increase with the material removal volume continuously, and the processing surface decreases to 1.4 μm. It has been proved that the cutting force tends to increase first and then decrease as the material removal volume is about 4320 mm³.     

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.     

Influence of cryogenic coolant on turning performance characteristics: A comparison with wet machining

Machining of 17-4 Precipitation Hardenable Stainless Steel (PH SS) is one of the difficult tasks because of its high cutting temperatures. Conventional cutting fluids are used to overcome the high cutting temperatures, but these are not acceptable from the health and environmental sustainable points of view. Cryogenic cooling is one of the potential techniques to overcome such problems. In the current work, comparison is made of cryogenic turning results, such as tool flank wear, cutting forces (feed force, main cutting force), cutting temperature, chip morphology and surface integrity characteristics with wet machining during machining of heat-treated 17-4 PH SS. The result showed that in cryogenic machining, a maximum of 53%, 78%, 35% and 16% reductions was observed in tool flank wear, cutting temperature, surface roughness and cutting force, respectively, when compared with wet machining. It was also evident from the experimental results that cryogenic machining significantly improved the machining performance and product quality even at high feed rates.     

不同冷却润滑方式对切削SiCP/Al复合材料刀具磨损的影响

为探究不同冷却润滑方式对切削SiC_P/Al复合材料刀具磨损的影响,进行了干切削（Dry）、微量润滑（MQL）、液氮（LN₂）、切削油（Oil）和乳化液（Emulsion）共五种冷却润滑条件下的车削实验,分析了冷却润滑方式对刀具边界磨损、刀具破损和后刀面磨损的影响。结果表明:MQL和LN₂有更佳的流体冲刷效果,可以将脱落的SiC颗粒及时带离切削区,减少边界磨损; Oil和Emulsion冲刷效果较差,会加剧边界磨损。LN₂的使用会增加刀具受到的热应力和机械冲击,积屑瘤发生完全脱落,造成切削过程不平稳,当切削距离达到1 100 m时,刀具发生破损; Oil切削时,严重的边界磨损导致刀尖部位尺寸减小,强度降低,当切削距离达到825 m时发生了刀具破损。MQL良好的润滑渗透性和LN₂有效的冷却效果可以减少后刀面磨损。因此,MQL兼具冷却、润滑和流体冲刷效果,更加适合作为切削SiC_P/Al复合材料的冷却润滑方式。      

Machinability of Metal Matrix Composites Reinforced by 3-D Network Structure

Metal matrix composites reinforced by three-dimensional (3-D) continuous network structure reinforcement (3DCNRMMC) are difficult to machine due to serious tool wear and poor surface roughness caused by the brittle and hard reinforcement which interpenetrate into ductile matrix. In order to achieve the approach of low cost of 3DCNRMMC, the machinability of it needs to be understood. The influences of three cutting parameters and volume fraction of reinforcement on cutting force were analyzed in detail. The results indicate that: (1) Due to the brittle phase(s) introduced into ductile matrix of composites, there is a large fluctuation of cutting force causing deterioration of machinability. The fluctuation ranges of cutting forces, initially increase rapidly with the increase of volume fraction of reinforcement and then decrease finally, are largest at the range of the volume fraction of 55–65%; (2) The influence of cutting parameters on cutting force is obvious. With the increases of cutting speed, cutting force decreases gradually unless cutting speed exceeds the value of 209 m/min. Cutting forces increase with increasing feed rate and depth of cut; (3) Owing to the large fluctuation of cutting force, there were some cratered surfaces caused by Si₃N₄ reinforcement pulling-out and flaking-off. Some brittle phase protruding from the machined surface caused the deterioration of machined surface.     

Investigation on Some Machinability Aspects of Inconel 825 During Dry Turning

In the current study, attempt has been made to investigate the influence of cutting speed (Vc) (51, 84, and 124 m/min) on various machining characteristics like chip morphology, chip thickness ratio, tool wear, surface, and sub-surface integrity during dry turning of Inconel 825. Comparable study was carried out using uncoated and commercially available chemical vapor deposition multilayer coated (TiN/TiCN/Al₂O₃/ZrCN) cemented carbide (ISO P30 grade) insert. Chip morphology consists of chip forms obtained at different cutting conditions. Serrated chips were observed when machining Inconel 825 with both types of tool with more serration in case of uncoated insert. The chip thickness ratio increased as cutting speed was increased. Use of multilayer coated tool also resulted in increase in chip thickness ratio. Rake and flank surfaces were examined with scanning electron microscope and optical microscope. Abrasion, adhesion, and diffusion wears were found to be dominating tool wear mechanism during dry machining of Inconel 825. The beneficial effect of coated tool over its uncoated counterpart was most prominent during machining at high cutting speed (Vc = 124 m/min). The surface and sub-surface integrity obtained with coated tool were superior to that while machining Inconel 825 with uncoated tool.     

Investigations on surface quality of WEDM-manufactured meso bevel and helical gears

This article presents investigations on and analysis of surface finish of meso bevel and helical gears made of stainless steel (SS 304) manufactured by wire electric discharge machining (WEDM) process using thin soft plain brass wire of 0.25?mm diameter. Effects of eight WEDM process parameters, namely, peak current, pulse-on time, pulse-off time, wire feed rate, wire tension, servo-gap voltage, dielectric pressure, and cutting speed on average and maximum surface roughness of the meso bevel and helical gears have been studied by conducting 31 experiments using one-factor-at-a-time approach to identify their optimum ranges/values for further experiments. Tooth profile, microstructure, microhardness, and topography of tooth flank surface have been studied for the best quality meso gears. Average and maximum surface roughness of tooth flank surfaces of meso bevel and helical gears increase with increase in peak current, servo-gap voltage, pulse-on time, wire feed rate, wire tension and cutting speed, and decrease with increase in pulse-off time while dielectric pressure does not significantly influence surface roughness. This work establishes that WEDM process can be an economic and sustainable manufacturing alternative for net-shaped meso-sized bevel and helical gears having better surface finish which will eliminate need of any subsequent finishing processes.