Abstract In the present study, the bi-layer NiCrAlY/Al 2 O 3 -40%TiO 2 coating was deposited on the three substrates (A-1, T-91, & Superfer800H) by utilizing a plasma spray technique. NiCrAlY was used as a bond coat for ensuring a proper mechanical anchorage of the topcoat (Al 2 O 3 -40%TiO 2 ) on to it. The hot corrosion behavior of the coated as well as uncoated substrate was evaluated in an aggressive environment of Na 2 SO 4 -60%V 2 O 5 molten salt at 900 °C for 50 cycles (1 h of heating followed by 20 min of cooling at ambient temperature). Thermogravimetric analysis was done to establish the corrosion kinetics of the coated as well as the uncoated substrate. The surface morphology of the as-sprayed and corroded products was analyzed by using a scanning electron microscope (SEM) system, and various phases formed were analyzed by utilizing an x-ray Diffraction (XRD) apparatus. Iron oxide (Fe 2 O 3 ) is the principal phase formed in the tested uncoated substrate which is non-protective in nature; whereas the presence of Al, and Ti oxides along with some minor oxides of Ni, and Cr were observed in the oxide scale of the tested coated substrate, which are protective and remain stable even at harsh environment condition. The weight gain shown by the coated substrate is less as compared to the uncoated substrate, which indicates the usefulness of the coating.
Metal cutting is the way of processing the workpiece with tool having sharp cutting edges of different materials generating chips of different shapes and sizes. In present era of industry 4.0, metal machining should not be unrated during processing of hard grades metals and superalloys where large amount of cutting forces are generated. Also, the measurement of cutting forces provides the basic of economical machining and hence accurate evaluation in experimental and analytical manner has great importance. The traditional models of metal cutting have disagreement with experimental results due to missing of important mechanics terms. With the development of digital technology, the errors in calculation of cutting force have also been shortened due to consideration of terms absent in conventional models. In present investigation, the cutting forces have been evaluated experimentally using dynamometer and analytically with Astakhov’s methodology during turning of EN-31 steel. The results revealed that 12.9% observations have deviation more than 20%, whereas 16.67 % has zero deviation. Further, the feed rate has more influence on cutting forces as compared to speed and nose radius. In addition, the minimum quantity lubrication (MQL) of vegetable oil has lowered the cutting forces appreciably compared to dry machining.
This research work highlights the benefits of abrasive flow polishing (AFP) applied to tungsten carbide dies compared with conventional hand polishing (HP). An indigenous experimental set-up for AFP was developed. The effect of prominent process parameters viz. extrusion pressure, number of cycles, and abrasive particle concentration on the final surface roughness, percentage improvement in surface roughness, and polishing time was investigated by Taguchi-designed experiments. The multi-objective optimization (MOO) was performed using the Taguchi-TOPSIS-Equal weight approach to find the respective optimized AFP parametric settings. A set of skilled operators performed the conventional HP of dies, and the best hand-polished (HPed) die was selected using the TOPSIS technique. The operational performance of the HPed dies and the abrasive flow polished (AFPed) dies were compared on the three-stage wire drawing operation. The results revealed that AFP's surface resulted in a better-quality surface than hand polishing with a 27.06% improvement in surface roughness. Furthermore, AFP can reduce the dependency on costly and tricky-to-locate skilled operators, with a reasonable amount of time saving (about 87.05%). Overall, the study's findings show that abrasive flow polishing of dies is fast and cost-effective.
Non-traditional machining methods like wire electric discharge machining (WEDM) appear to be an ideal choice for machining high strength super alloys like Inconel 706, because of their capability to generate intricate profiles with high accuracy. However, wire breakages are a common problem in the WEDM process and adversely affect the productivity, accuracy, and surface quality. Therefore, the aim of this work is to investigate and comprehend the phenomenon of wire breakage using Inconel 706 as work material and brass wire, diffused brass wire, and zinc-coated brass wire as electrode materials. Six process parameters—pulse-on time, pulse-off time, peak current, spark gap voltage, wire feed rate, and wire tension—have been varied experimentally to determine their effect on the frequency of wire failure. According to the findings, the zinc-coated brass wire breaks with the lowest frequency when compared to the other two. Additionally, an ideal range of input variables has been proposed for efficient WEDM of Inconel 706 without unexpected wire breakages. This range can also be utilized for further research work related to modeling and optimization in WEDM of Inconel 706.
The advanced class of Al/(RHA+Mg+Cu) hybrid metal matrix nanocomposites (MMNCs) has exhibited superior physical, and mechanical properties with superior wettability and chemical compatibility. This work has also been reported on the machining and multiobjective optimization of process variables for the machining of Al/(RHA+Mg+Cu) hybrid MMNCs on EDM using L 27 Taguchi’s orthogonal array integrated with Grey rational analysis (GRA). The primarily target goal of this study is to produce nanocomposite having better properties with minimal production cost, with the use of reinforcement rice husk ash (RHA). RHA is utilized in the base matrix of Al 6061 at wt.% of 6, 8, and 10. On the other hand, the elements such as Cu and Mg are placed fixed, i.e., 3 wt.% and 1 wt.%, respectively. The hardness, tensile strength, and impact strength of the nanocomposites increased with the maximum increment of 35.11%, 15.76%, and 16.67%, respectively, as compared to neat composite. Further, the purpose of this investigation was to determine the effect of various factors such as the percentage of RHA in the workpiece electrode (W), the discharge current (I), the voltage (V), the duty factor ( τ ), the pulse‐on time (Ton), and the flushing pressure (P) on the material removal rate (MRR), the surface roughness (SR), and the tool wear rate (TWR) during the machining of hybrid nanocomposites using Taguchi’s approach. The results revealed that MRR decreased with increasing the RHA content in the workpiece which can be reasoned to isolating nature of the RHA. It clearly shows that SR has decreased with an addition of RHA content from 6 wt.% to 8 wt.% in workpiece, but it slightly increased by further addition of RHA from 8 wt.% to 10 wt.%. SR has decreased with an increase in duty factor while performing EDM trials with the copper electrode, but it slightly increases with a further increase in duty factor. By the increase in pulse‐on time, spark energy also increases also leading to the formation of craters. Therefore, SR has increased with an increase in pulse‐on time. The TWR has increased with an increase in RHA content in the workpiece, because of the existence of hard reinforcements on the matrix which causes larger wear in the tool. Analysis of SEM micrographs showed the presence of voids, shallow and deep craters, and black voids on the machined surface of the fabricated hybrid nanocomposites. As calculated using the response graph for GRG, confirmation tests for optimal parametric setting show improvement over initial parametric setting of machining parameters. The mean of optimal MRR, SR, and TWR is estimated at the significant level of machining factors at A 1 B 3 C 3 D 2 E 3 F 1 , A 2 B 1 C 1 D 2 E 1 F 3 , and A 1 B 1 C 1 D 1 E 1 F 3 , respectively.
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