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The corrosion resistance Cr3C2-25%NiCr and Ni-20%Cr coatings were deposited on the alloy A-286 by high-velocity oxy-fuel (HVOF) coating, and the high-temperature corrosion features were evaluated at 700 and 850°C in Na2SO4-5%NaCl-7.5%NaVO3 atmosphere. Deposited coatings are dense and well-adherent to the substrate. A scanning electron microscope (SEM) is used to analyze the structure of the corroded samples. Results showed that Cr3C2-25%NiCr coating provides better resistance to corrosion at 700°C, which is attributed to the protective Cr2O3 development. The coated metal was exposed at 850°C, and a higher corrosion rate was observed compared to 700°C, indicating that the temperature influenced the oxidation rate. The coating failure (crack) was noticed on the Cr3C2-25%NiCr coated surface when exposed at 850°C, and no damages are in the Ni-20%Cr coating. [ABSTRACT FROM AUTHOR]

The present study aims to develop a novel hybrid polymer composite with reduced graphene oxide (rGO) as filler and optimize its Abrasive Water Jet Machining (AWJM) parameters for reduced kerf width. The influence of rGO addition on kerf width is analysed in detail along with Pump pressure (bar), Transverse speed (mm/min) and Standoff distance(mm). The experiments are designed based on Taguchi's orthogonal array techniques in which L27 is adopted for three input parameters at three levels. The influence of each factor is used to identify the significance of selected parameters over kerf width, and it was found that stand of distance has a major effect over kerf width irrespective of rGO %. The addition of rGO filler has a significant effect on kerf width, which decreases with the addition of rGO up to 0.2% and kerf width increases for further addition of rGO.

Defects like crack are common in engineering structures that are either material intrinsic or initiate during fabrication. The theory of fracture mechanics establishes a mechanistic relationship between the maximum allowable loads applied on a structural component to the size and location of an actual or assumed crack in the component. Linear‐elastic or complex elastic‐plastic, i. e., non‐linear models, are used to conduct the fracture analysis. Established studies show that methods of non‐linear fracture mechanics, in comparison to elastic methods, offer more accurate measures of the fracture behaviour in failed structures with high toughness and materials with low strength. In this work, an attempt is made to evaluate stress intensity factor‐KI and J‐integral of 40Ni2Cr1Mo28 alloy (structural application steel) for various crack length‐a to width ratio‐W (a/W = 0.25, 0.375, 0.5, 0.625 and 0.75) against the applied force in the form of load under plane stress condition by elasto‐plastic finite element analysis (compact tension specimen). Non‐linearity is modeled using the inverse Ramberg‐Osgood relation. Compact tension specimen is modeled in ANSYS software and analyzed by using Finite element analysis. It is found that there is a good agreement between both finite element analysis and theoretical value with an error deviation in the range of 0 % to 6 %. [ABSTRACT FROM AUTHOR]

Copper (Cu) matrix composites are developed by reinforcing Cu with Titanium Carbide (TiC) powder using the powder metallurgy (PM) method. Pin-on-disc tribo analysis is conducted to evaluate the tribological performance of the developed composites. Moreover, the influence of different parameters such as, concentration (wt.%) of TiC, applied load, sliding velocity and sliding distance on the wear rate and friction coefficient are studied using Taguchi L16 orthogonal array. The main effect plot reveals that the lowest wear rate is obtained at 12 wt.% of TiC, 10 N applied load, 4 m/s sliding velocity and 1750 m sliding distance. Similarly, the lowest friction coefficient is attained at 12 wt.% of TiC, 10 N applied load, 4 m/s sliding velocity and 750 m sliding distance. Analysis of variance (ANOVA) results shows that the wt.% of TiC powder is a more noteworthy parameter for obtaining the lowest wear rate and friction coefficient with a contribution of 94.54% and 94.17%, respectively. A regression model is also developed to predict the friction coefficient and wear rate for the developed composites. [ABSTRACT FROM AUTHOR]

Supercapacitors are gaining popularity as energy storage devices because of their quick charge/discharge rates, prolonged cycle stability, and high specific power. Low-cost active electrode materials have piqued the interest of researchers in energy storage applications, notably supercapacitor applications. Carbon-based electrode materials have demonstrated excellent performance for electrochemical double-layer capacitors because of outstanding chemical and physical properties, low cost, large expanse, conduction, and extended life at high temperatures. Notably, graphene compound materials performed well for supercapacitors and had a long life of 335 000 cycles. Conducting polymers have exceptional and critical characteristics, such as metal-like conduction and reversible ability between redox states. Recent research interests include the creation of novel materials, namely mixed metal oxides and metal sulfides, for supercapacitors applications. The electrodes of supercapacitors, which are mostly made of metal oxides (Co3O4, MnO2, WO3, NiO, and TiO2), have a high degree of stability and retention (up to 94%). Currently, metal sulfide-based materials, including CoNi2S4 and Ni3S2, have attained specific capacitance values of up to 3296 F/g. When compared to standard capacitors, the supercapacitors outperformed them and employed high power density storage devices. The electrodes of supercapacitors, which are mostly made of metal oxides (Co3O4, MnO2, WO3, NiO, and TiO2), have a high degree of stability and retention (up to 94 percent). Presently, the review focuses on active electrode materials for supercapacitors such as carbon-based materials, conducting polymers, metal oxides, and metal sulfide compounds. The objective of this review is fivefold: (1) to present the fabrication of symmetric and asymmetric supercapacitor cells; (2) to describe the performance of carbon-based materials for electrochemical double-layer capacitor; (3) to describe the performance of conducting polymers for supercapacitors in the aqueous and non-aqueous electrolyte; (4) to describe the high-performance metal oxide and metal sulfide for supercapacitor; (5) to outline the major challenges in the technology development and this technology is far more advanced than batteries and has been utilized in a wide range of sectors, including electronics, industries, medicine, and the military. [ABSTRACT FROM AUTHOR]

The Ti-6Al-2Sn-4Zr-2Mo alloy was machined using the wire electrical discharge machining (WEDM) method in this research. The consequences of input values like pulse on duration, wire tension, and wire feed on metal removal rate (MRR) and surface roughness (SR) have indeed been observed. After conducting 27 experiments using Taguchi's L27 type of research technique, empirical designing and analysis of variance (ANOVA) were performed. For process optimization, the Taguchi technique, which is based on the grey relational analysis approach, is used. The results show that a material removal rate of 0.293 mm3/min was obtained with factors of 10 µs pulse on duration, 7 m/min of wire feed, and 12 g of wire tension (the higher the better), and surface roughness of 2.129 µm was obtained with factors of 6 µs pulse on duration, 3 m/min of wire feed, and 8 g of wire tension (the lower the better). The percentage of errors between results obtained and grey relational analysis (GRA) predicted results varies around 6%. Wire electrical discharge machining with Ti-6242 alloy to optimum conditions resulted in better MRR and surface integrity with good surface finish and integrity as evidenced by a substantial reduction in the crack formation, lumps, and accumulated surfaces. [ABSTRACT FROM AUTHOR]

The residual stresses are responsible for most of the failure of weldments in nuclear industry and the temperature distribution is the key measure to predict these residual stresses. The residual stresses are produced due to the non-uniform heating and cooling of the material and thus generating inhomogeneous plastic deformation in the components during the welding process. The Plasma arc welded 2 mm thick Ti-6Al-4V plate is taken for the study to predict the weld bead geometry, temperature distribution and residual stresses. The temperature distribution is predicted through the transient thermal analysis in ANSYS Parametric Design Language (APDL) using Three-Dimensional Conical Heat Source Model & Dhinakaran's model and the simulated results are validated against the experimental outcomes. The temperature-dependent material properties with the temperature range varying from the room temperature to the melt pool temperature are considered for transient thermal analysis. The radiation heat transfer becomes predominant at high-temperature regimes; hence the radiation effects are imposed into the convective heat transfer coefficient. The weld bead geometry, temperature distribution and the residual stresses are predicted at various regimes of the plate. It is observed that the theoretical values obtained from the FEM Simulation are good in agreement with the experimental values. [ABSTRACT FROM AUTHOR]

In this research work, a new analytical model has been developed to predict the temperature distribution during plasma arc welding of thin Ti-6Al-4V sheets. Dhinakaran’s model based on a three-dimensional parabolic Gaussian heat source is considered as a plasma arc heat source moving on a semi-infinite body to derive the analytical model and the same heat source model is substituted in the three-dimensional Fourier’s law of heat conduction and implemented in the finite element package. Thermo physical properties, such as density, specific heat, and thermal conductivity, are used as temperature-dependent properties in finite element simulation. Numerical simulation is carried out using COMSOL. The new analytical model is expressed as a function of three-dimensional spatial co-ordinates and the time co-ordinate. A computer program has been written to solve the analytical model in order to obtain the distribution of transient temperature at any point of interest. The transient temperature distribution predicted by the analytical model has been compared with both the experimental result and the numerical result. Experimental work is carried out to measure the thermal cycle during welding. The thermal cycle is measured by using an infrared thermometer. Very good correlation has been obtained between the predicted transient temperature by analytical solution and the measured temperature, as well as the finite element simulation result. This provides a reliable alternative for using these analytical solutions in the future to obtain the thermal cycle, distortion, and thermal stress during plasma arc welding. [ABSTRACT FROM AUTHOR]

In this paper, a new volumetric heat source model is developed for predicting the weld bead geometry during plasma arc welding of thin sheets of titanium alloy. Numerical simulations are carried out with the proposed parabolic Gaussian heat source (PGHS) model and already prevailing familiar heat source models namely, conical heat source and modified conical heat source, using finite element package COMSOL. The temperature-dependent material properties for Ti–6Al–4V alloy are considered for performing numerical calculations, which tend to influence the temperature fields while computing. Besides, the effect of trailing gas shielding, latent heat, and radiative and convective heat transfer are taken into account while performing the transient thermal analysis which significantly alters the sensitivity and accuracy of the model. Experimental trials on thin titanium alloy sheets are carried out to enable the validation of the proposed PGHS model. Subsequently, the outcome reveals that the PGHS model is capable and proved its high degree of efficiency in predicting the weld bead geometry more accurately than the existing heat source models. The distribution of heat intensity along the thickness of thin sheet is observed to be parabolic as predicted by the proposed model. The prediction appears to have a good correlation with the experimental result and it is clearly perceptible that the parabolic shape is more reliable and yields greater accuracy of the proposed heat source model. [ABSTRACT FROM AUTHOR]

Numerical and experimental investigations of autogenous plasma arc welding of thin titanium alloy of 2 mm thick and modelling the temperature distribution for predicting the weld bead geometry are presented. The finite element code COMSOL Multiphysics is employed to perform non-linear unsteady heat transfer analysis using parabolic Gaussian heat source. Temperature-dependent material properties such as thermal conductivity, density and specific heat are used to enhance the efficiency of simulation process. A forced convective heat transfer coefficient was used to account for the effect of convection. The experimental trials were conducted by varying the welding speed and current using Fronius plasma arc welding equipment. The simulation results are in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

[Display omitted] • 321 SS thin wall deposited successfully with WAAM. • High-temperature performance of WAAM 321 SS was tested in molten salt and air environment. • Air oxidized specimen has lower mass gain and obeys the parabolic law than the hot corroded specimen. • Fe 2 O 3 is the main scale formed on the specimens during the exposure in both conditions. • The existence of S and V enhanced the corrosion rate, resulting in high mass gain observed in the corroded specimen. The main aim of the present work is to examine the microstructure and high-temperature corrosion performance of wire + arc additive manufactured (WAAM) 321 stainless steel (321 SS) specimens exposed to molten Na 2 SO 4 + 60%V 2 O 5 salt and air atmosphere at 700 °C under cyclic conditions. The as-built specimens presented a typical layered microstructure with δ-ferrite in the austenite matrix along with small fraction of TiC. The corroded specimen exhibits a high weight gain compared to the oxidized sample, which is attributed to the deposited molten salt. The cracks were developed on the corroded sample attributed to the fluxing of oxides by vanadium and sulphur. Due to good adherent of scale to the steel no spallation were noticed till end of study in both the atmosphere suggesting that WAAM produced steel is suitable for the boiler environment up to 700 °C. [ABSTRACT FROM AUTHOR]

• ZnS-Co 3 S 4 Nanoscrubbers developed by hydrothermal method. • Physical and chemical properties were studied. • Electrochemical properties were investigated. • High specific capacitance value 593F/g was achieved. ZnS-Co 3 S 4 Nanoscrubbers were prepared by hydrothermal routes and characterized by advanced techniques. The supercapacitance behavior of crystalline ZnS-Co 3 S 4 nanoscrubber modified electrodes was examined using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques. As-prepared ZnS-Co 3 S 4 nanoscrubbers have a high specific capacitance (Csp) value of 593 F/g at 0.5 A/g. The ZnS-Co 3 S 4 modified electrode was found to be highly stable for 2000 cycles at 0.5A/g. [ABSTRACT FROM AUTHOR]