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Today, energy consumption and environmental issues are important topics in all industries around the globe. However, quality is in direct proportion with energy consumption, since better surface finish means more energy consumption. The main objective of this work is minimizing both surface roughness and power consumption by estimating the optimum machining parameters. In this study, turning tests were carried out on three different hardened AISI 1040 steels (10, 15, 20 HRC) at three different depths of cuts (1.2, 2.4, 3.6 mm), feed rates (0.15, 0.25, 0.35 mm × rev−1) and cutting speeds (120, 140, 160 m × min−1) without coolant. The effects of cutting parameters and workpieces hardness on surface roughness, sound level and power consumption were examined. These analyses were conducted using a full factorial experimental design method. The response surface methodology and analysis of variance were also used to determine the effects of input parameters on the response variables. Experimental results showed that an increase in the feed rate value causes an increase in the surface roughness, the sound level, and the power consumption values. The results of the presented work show that feed rate is the most effective machining parameter that affects surface roughness and power consumption. Following feed rate, depth of cut and cutting speed also have an important impact. Thus, decreasing the value of feed rate and depth of cut will reduce the amount of power consumption.

Recently, hard turning became an interesting method to the manufacturers as an alternative to the grinding process due to its superior features such as good surface quality, good productivity, lower production costs, lower power consumption, and shorter processing time. Despite its considerable benefits, hard turning is a difficult process that needs advanced cutting inserts such as ceramics and cubic boron nitride. However, these cutting inserts are costly and should be used properly by choosing appropriate machining parameters.In the presented work, the hard turning process was performed to investigate the machinability of AISI S1 cold work tool steel using a cubic boron nitride insert. The relation between machining parameters namely, depth of cut, cutting speed, and feed rate on the responses such as power consumption, surface roughness, and machining sound was found using a full factorial orthogonal array of response surface methodology.In addition, analysis of variance was used to identify the most important machining parameters that influence output parameters. Based on the results, surface roughness was dominantly affected by feed rate, whereas, sound and power consumption were influenced by all machining parameters especially cutting speed and feed rate. A good agreement between the experimental and the predicted values were observed.

AISI D6 (hardness 65 HRC) is one of the hard-to-cut steel alloys and commonly used in mould and die making industries. In general, CBN and PCBN tools are used for machining hardened steel but its higher cost makes the use for limited applications. However, the usefulness of carbide tool with selective coatings is the best substitute having comparable tool life, and in terms of cost is approximately one-tenth of CBN tool. The present study highlights a detailed analysis on machinability investigation of hardened AISI D6 alloy die steel using newly developed SPPP-AlTiSiN coated carbide tools in finish dry turning operation. In addition, a comparative assessment has been performed based on the effectiveness of cutting tool performance of nanocomposite coating of AlTiN deposited by hyperlox PVD technique and a coating of AlTiSiN deposited by scalable pulsed power plasma (SPPP) technique. The required number of machining trials under varied cutting conditions (speed, depth of cut, feed) were based on L16 orthogonal array design which investigated the crater wear, flank wear, surface roughness, chip morphology, and cutting force in hard turning. Out of the two cutting tools, newly-developed nanocomposite (SPPP-AlTiSiN) coated carbide tool promises an improved surface finish, minimum cutting force, longer tool life due to lower value of crater & flank wears, and considerable improvement in tool life (i.e., by 47.83%). At higher cutting speeds, the crater wear length and flank wear increases whereas the surface roughness, crater wear width and cutting force decreases. Chip morphology confirmed the formation of serrated type saw tooth chips.

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