Microstructure degradation and creep failure study of the dissimilar metal welded joint of heat-resistant steel and Inconel 617 alloy tested at 650 °C and applied stress range of 100-150 MPa

The advanced ultra-supercritical (A-USC) power plant system is anticipated to become India's next-generation base-load power station. To adopt AUSC technology, dissimilar welded joints (DWJs) between heat-resistant steels and the nickel-based alloys, using the nickel-based fillers, will need to be implemented. However, failure of dissimilar welded joints from P92 steel base metal or the heat affected zone (HAZ) has been commonly observed under high-temperature creep conditions. In the present study, the creep rupture behaviours and rupture mechanisms of DWJ between the Ni-based alloy Inconel 617 and heat-resistant P92 steel with Inconel 617 (ERNiCrCoMo-1) filler metal were investigated. Creep tests were conducted at 650 degrees C in the stress range of 100-150 MPa. To examine the creep rupture behaviour of the DWJ samples, optical microscopy (OM), scanning electron microscopy (SEM) and microhardness tests were performed. Cross-sectional images of the fractured creep specimens tested under various operating conditions revealed failures originating from distinct locations, including the P92 base metal and the inter-critical heat affected zone (HAZ). The specimen tested at 650 degrees C/150 MPa exhibited failure originating from the P92 base metal, whereas the specimen tested at 650 degrees C under the stress range of 100-130 MPa showed failure from the inter-critical heat affected zone (ICHAZ). The failure from P92 BM was primarily governed by plastic deformation, with the growth and coalescence of dimples ultimately resulting in trans-granular fracture. The specimens tested at 650 degrees C/100-130 MPa, which failed from the ICHAZ, exhibited a typical Type IV inter-granular failure. This failure mode is primarily attributed to matrix softening in HAZ, weakening of the boundaries, coarsening of the precipitates, and the evolution of intermetallic Laves phases. The specimen that failed in the stress range of 100-130 MPa exhibited a high density of microvoids in the ICHAZ, along with a few microvoids in the FGHAZ. The weld metal showed negligible degradation in microstructure, while the hardness study revealed a significant increase in hardness with an increase in rupture time, i. e., a decrease in applied stress and it was attributed to evolution of the new carbide phases in weld metal. Coarsening of the carbide precipitates was observed in each zone of the HAZ of P92 steel as well as in the base metal. The EDS study of the fracture tip and the FGHAZ/ICHAZ of the specimen that failed under stresses of 100 MPa and 120 MPa confirmed the evolution of intermetallic Laves phases. High magnification SEM images confirmed that triple boundaries are preferential locations for microvoid nucleation. The failed specimen showed the presence of microvoids near the carbide precipitates, with a large density of both coarse and fine precipitates confirmed all around and inside the microvoids. The ICHAZ and FGHAZ confirmed the formation of fine prior austenite grain boundaries (PAGBs) during the welding thermal cycle, which exhibited a lower density of carbide precipitates and this played a major role in Type IV failure

A review on assessment of ionic liquids in extraction of lithium, nickel, and cobalt vis-`a-vis conventional methods

This review discusses the extraction of critical metals (Li, Co, and Ni) using ionic liquids. Here, ionic liquids act as solvents for the separation and extraction of metals. In addition to extraction, they can be used as a lixiviant to leach out metals from spent lithium-ion batteries. Leaching and extraction of metals from the leachate can be performed using a single ionic liquid solvent. Lithium, cobalt, and nickel have been discussed in detail as per their reactivity towards an ionic liquid based on the extraction efficiency and reusability of the ionic liquid. Recycling and reusability of ionic liquids are crucial parameters to be considered while using them as solvents for extracting metals. Moreover, all the other methods such as solvent extraction, ion exchange, ionic liquids, and DES-based separation of metals are compared with respect to their extraction efficiency, cost-effectiveness, and reusability

In situ synthesis of a photocatalyst using TiO2 QDs-immobilized functionalized galactomannan for degradation of organic pollutant

TiO2 based photocatalysts are highly efficient systems in degrading organic contaminants. In the present work, an in-situ approach has been adopted to synthesize TiO2 quantum dots (QDs) with simultaneous grafting of methacrylic acid (MAc) on guar gum (GG), to develop a hybrid composite (GG-g-PMAc-@-TiO2 QDs) for photocatalytic degradation of toxic organic contaminant. The in-situ synthesis and proper dispersion of TiO2 QDs over polymer surface is aided by the stabilization through electrostatic interaction and hydrogen bonding between the acid functionality of the grafted PMAc chains and TiO2 QDs. The structural and morphological properties of GG-g-PMAc-@-TiO2 QDs have been thoroughly investigated by various characterization techniques. The HR-TEM analysis reveals the average particle size of TiO2 QDs is similar to 3.9 nm. The optical properties of the composite have been studied by UV, PL and TCSPC analyses. Moreover, the developed nanohybrid GG-g-PMAc-@-TiO2 QDs photocatalytically degrades ciprofloxacin (CIP) efficiently (similar to 94 % degraded within 3 h). The HR-MS analysis predicts the various degraded CIP fragments that have further been used to establish probable degradation mechanism

Optimisation of process parameters for coal flotation using statistical technique

The ash content present in coal plays an important role in determining the quality or grade of the coal for its utilization in different industries. The maximum ash content allowed for steel grade I is 15%, while steel grade II requires ash content ranging from 15% to 18%. A sample of coking coal analysing 26.32% ash was subjected to froth flotation to reduce its ash content to below 18%. Optimization of flotation process parameters such as collector, frother dosages and airflow rate, was carried out using factorial design of experiments. It was observed that the interaction of collector and frother dosages had the most significant impact on achieving the desired ash rejection, with collector dosage also playing an important role. Optimum process parameters identified are collector dosage of 0.0348 kg/t, 0.005 kg/t frother dosage and 2 lpm airflow rate, wherein the ash content of the sample was reduced to 14.58% from 26.32%

Avenues of resources efficiency enhancement in iron and steel production

Ironmaking- steelmaking is a material and energy intensive process with a resource efficiency of only - 33 %. Resource efficiency enhancement requires recovering the wasted/unutilized material by-products and the energy associated with them in various forms. This review attempts to identify the material leakages and energy losses at each step of steelmaking (from iron ore mining) and explores approaches to plug the energy and material leakage; material efficiency brings in energy savings indirectly. Besides the material loss, accumulation of the by products (slime/tailings, steel slag, etc.), carbon emission, etc., cause environmental and ecological damage. The review discusses the prospects of slimes/tailings beneficiation through physical and physicochemical methods (often after some pre-treatments). The manuscript also discusses the need to recover heat from molten slags (BF slag and BOF slag) to reduce the energy intensity. Further, it discusses the endeavours to overcome the latent hydraulic activity of granulated BF slag and ways to enhance the acceptability of BOF slag in different applications. A brief sum-up of global efforts towards net zero emission (in line with the Paris Declaration) through carbon recycling, low emission intensity processes, alternate fuels, etc., is included. Lastly, the authors list the challenges of the Indian iron & steel industry and the efforts from the government and steel industries towards achieving the projected crude steel production (300 million tons) without crossing the emission intensity thresholds (Paris Declaration). The endeavours strengthen the sustainability of the steel industry

Real-Time In-Process Measurement and Control of Zinc Coating Weight: Assessing Eddy Current Sensor Proficiency in Industrial Applications

The investigation aims at evaluating the proficiency of an eddy current (ECT) sensor potential for in situ, real-time industrial applications. This sensor designed for in-process monitoring and control of zinc coating weight on GI wires, ranging from approximately 50-150 g/m2 expressed as grams per square meter (GSM). It is engineered to operate effectively in challenging industrial environments, providing immediate feedback during production, even at high speeds. In this study, an ECT sensor is configured in an encircling coil arrangement, consisting of three coils of which two transmitter coils are interconnected in a Helmholtz configuration, while the receiver coil is precisely positioned axially and concentrically between the transmitter coils. This design substantially extends the measurement region with a nearly constant magnetic field profile, making it particularly suitable for evaluating the weight of thin zinc coatings on the tested specimens. The superiority of this configuration is established through mathematical modeling, showcasing enhanced measurement accuracy and sensitivity, especially for evaluating the weight of thin zinc coatings on wires. This is further affirmed through validation and optimization via finite element method (FEM) simulations. In situ performance evaluation of the sensor system was conducted at an industrial installation, encompassing essential practical considerations, such as repeatability, reproducibility, and the influence of temperature fluctuations. The findings are in agreement with the chemical analysis (within +/- 5 %) stipulated by international regulations. The ability to consistently measure and record thin coating weight confers significant benefits, contributing to both zinc conservation and optimal quality control

External Electric Field Induced Atomic Charge Migration and Surface Degradation of CsPbI3: A Reactive Molecular Dynamics Simulation based study

Cesium lead iodide, CsPbI3, is a promising material for solar cell manufacturing; nonetheless, it has numerous mechanical stability issues. Furthermore, due to low spatiotemporal resolution in experimental tests, the effect of several types of external loads, such as temperature and electric field-induced stresses, on the degradation mechanism of perovskite materials is poorly known. In this study, the electrical field-induced surface degradation mechanism of α, β, γ-CsPbI3 phases is simulated using advanced reactive molecular dynamics simulation. Our simulation results provide information about the rupture of atomic level unit cells and the subsequent erosion of materials from the surface (surface degradation) under the effect of an external electric field. The surface degradation is caused by electric field-induced stresses on Cs, Pb, and I atoms. The forces acting on the anion I are stronger than those acting on the cation Cs and the Pb atom. Atomic charge migration is strongly impacted by the magnitude of the electric field and the temperature of the system. Prior to surface degradation, charge migration occurs under a modest electric field. We investigated atomic charge migrations across various atoms and their unit cells. We anticipate that our findings will help researchers better understand the stability of perovskite materials under electric field and temperature-induced stress

Relationship between petrological characteristics and gross calorific value of coal

In this work, an attempt has been made to understand the relationship between petrological parameters and the gross calorific value (GCV) of coal. This study aims to enhance the understanding of how compositional parameters govern GCV, providing insights into the broader influence of coal's petrological characteristics on its energy content. In this regard, coal samples of wide variation in ash yields obtained from density fractionation were analyzed for the detailed petrological parameters along with the GCV. The petrological study of the density fractionated coal samples showed the difference in macerals composition, maturity, and maceral-mineral associations that potentially affect GCV. Given the number of parameters, identifying the factors influencing GCV posed challenges such as visualization, dimensionality, multicollinearity, and overfitting. Therefore, principal component analysis (PCA) was performed towards better understanding of the intricate relationships among variables, addressing multicollinearity, and visualizing GCV variability as well as its influencers. The analysis indicated that both reactive macerals (vitrinite and liptinite) and so-called "inert" macerals from the inertinite group contribute to GCV in distinct ways. The analysis also showed that GCV is favored by both vitrinite and semifusinite, with vitrinite's high reactivity and semifusinite's link to coal maturity playing key roles. The findings highlight the need to consider multiple factors, such as maceral type and maturity, in combination for future quantification attempts

Recovery of calcite using eco-friendly bio-collector in the flotation of low-grade limestone

Limestone flotation is a vital process in mineral processing, aimed at selectively separating valuable minerals such as calcite, from its associated gangue in the limestone matrix. The flotation of a low-grade limestone analyzing 41.78% CaO, 5.74% MgO, and 9.87% SiO2 by utilizing a new eco-friendly, plant seed oil processing industry waste-based fatty acid, as an anionic bio-collector for developing a sustainable process, was studied. A flotation concentrate of 59.94% weight recovery and analyzing 2.67% MgO, 49.92% CaO and 2.79% SiO2 could be obtained at 2.4 kg/t bio-collector dosage. The flotation results indicated the selective recovery and enrichment of CaO and reduction of MgO and SiO2 content from the low-grade limestone thereby making it a suitable raw material for cement manufacturing. The study highlights the development and the effective utilization of industrial waste-derived, bio-based calcite collector that aligns with the growing emphasis on the broader industry trend toward more sustainable mineral processing practices

On improved inorganic gas-sensing characteristics of microwave-treated tungsten oxide quantum dots at room temperature

Tungsten oxide (WO3) based metal oxide semiconductor material has been conventionally used for sensing inorganic gases at elevated temperatures. However, in this study, the gas sensing performance of tungsten oxide-based sensors is evaluated at room temperature. In this study, WO3 quantum dots (QDs) are synthesized via the electrochemical method, followed by a microwave treatment to dehydrate them. The newly developed process is relatively less expensive and offers the flexibility to alter the structure in terms of phase, size, shape, and vacancy concentration. It is observed that electrochemical process parameters play an important role in phase evolution and control the oxygen vacancy concentration in the powder, which are essential for enhancing its gas sensing characteristics. Results showed an enhanced gas-sensing ability of WO3 QDs at room temperature toward inorganic gases, such as CO, NO2, NH3, and H2 when subjected to microwave treatment. The enhanced gas-sensing performance of microwave-treated WO3 QDs is attributed to its smaller size and high oxygen vacancy concentration. The minimum limit of detection values for CO, NO2, NH3, and H2 at room temperature using microwave-treated hydrated tungsten oxide QDs were 4.60, 1.5, 0.35, and 10.25 ppm, respectively