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The present research addresses the machinability of hardened die steel (AISI D3, 61HRC) in hard turning using multilayer (TiCN/Al2O3/TiN) coated carbide tool under nanofluid based minimum quantity lubrication-cooling condition, where no previous data are available. Power consumption, flank wear, chip morphology and surface integrity (microhardness, residual stress, white layer formation, machined surface morphology, and surface roughness) are considered as technological performance characteristics to evaluate the machinability. Combined approach of central composite design - analysis of variance, response surface methodology and desirability function analysis have been employed respectively for experimental investigation, predictive modelling and multi-response optimization. With a motivational philosophy of “Go Green-Think Green-Act Green”, the work also deals with energy saving carbon footprint analysis and sustainability assessment to recognize the green manufacturing in the context of safer and cleaner production. under environmental-friendly nanofluid assisted minimum quantity lubrication condition. The quantitative analysis revealed that the cutting speed influenced the power consumption during hard machining (75.78%) and flank wear of coated carbide tool (45.67%); feed rate impacted the surface finish of the machined part (68.8%) significantly. Saw tooth shapes of chip produced due to cyclic cracking. Due to low percentage contribution of error (5.32% to Ra, 6.64% to VB, and 7.79% to Pc), a higher correlation coefficient (R2) was obtained with the quadratic regression model, which showed values of 0.9, 0.88 and 0.92 for surface roughness, flank wear, and power consumption, respectively. Optimization with the highest desirability (0.9173) resulted the optimum machining conditions under NFMQL at the cutting speed of 57 m/min, depth of cut 0.1 mm, feed of 0.07 mm/rev, and insert’s nose radius of 0.4 mm. As a result, under NFMQL tool life was improved by 30.8% and 22.6% in respect of flank wear and surface roughness respectively than when machining with MQL technique by adapting the optimum machining condition. Therefore, using hard nanoparticles-reinforced cutting fluid under minimum quantity lubrication condition in practical manufacturing becomes very promising to improve sustainability.

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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.

Present investigation is aimed on chemically modified of Sunn Hemp (Crotalaria juncea) fiber for composite fabrication. An increment in cellulose crystallinity with crystallite size is observed from X-ray diffraction study. The signature of impurities removal and an uneven surface are confirmed from Fourier Transmission Infrared Spectroscopy and Field Emission Scanning Electron Microscopy. Afterwards, both raw sunn hemp-reinforced fiber composite and dewaxed sunn hemp fiber-reinforced composite were fabricated using hand lay out method and the mechanical as well as dielectric properties of composite are studied. A better mechanical strength is found in DSHC which may attribute to rough surface and increased cellulose crystallinity through dewaxing process that promoted a fine interfacial bonding between fiber and matrix. Dielectric constants and losses are found to be less in dewaxed sunn hemp fiber-reinforced composite in comparison to raw sunn hemp-reinforced fiber composite due to decrease of water polar groups, which lead to lessening the effect of space charge polarization by treatment. Complex impedance and modulus study revealed the presence of single relaxation process in both systems. Lower ac conductivity value is observed in dewaxed sunn hemp fiber-reinforced composite due to decreasing of conducting polar OH groups. As a whole, the effort is established to correlate the mechanical and dielectric properties with fine structural parameters of the fiber.

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