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The effect of Si content on structural, mechanical and optical behaviour of magnetron sputtered Al–Si–N nanocomposite thin films
No full textMagnetron sputtered Al–Si–N thin films with varying silicon content were developed by Al–Si target with different amount of silicon by weight % (0, 5, 10, 14, 20). The effect of increasing silicon content on structural, mechanical and optical behaviour was investigated. The phase analysis and crystallite size of the films were studied by X-Ray Diffraction. The changes in microstructure of the coatings were studied by scanning electron and transmission electron microscopes (SEM, TEM). Mechanical behaviour such as hardness, elastic modulus and creep were studied by nanoindentation. The optical transmittance spectra of Al–Si–N film system at varying silicon content were acquired by UV–Visible Spectrometer. The correlation between the microstructure, mechanical and optical properties of the coatings at varying silicon content was established
Processing of Waste Copper Converter Slag Using Organic Acids for Extraction of Copper, Nickel, and Cobalt
Get PDFAn innovative, economical, and environmentally sound hydrometallurgical process has been proposed for recovering Cu, Ni, and Co from copper-rich converter slag by organic acids. In the leaching experiments, the eects of organic acid concentrations, pulp density,temperature, and time were investigated. Optimum recovery of 99.1% Cu, 89.2% Ni, 94% Co, and 99.2% Fe was achieved in 9–10 h at 308 K (35 oC) temperature and 15% pulp density with 2 N citric acid using <45 micron particles. Pourbaix diagrams of metal-water-citrate systems were supplemented to examine solubility of ligands at the desired conditions. Furthermore, the leaching mechanism was based on the SEM-EDS (energy-dispersive X-ray spectroscopy) and XRD characterization as well as the leaching results obtained
Low Cycle Fatigue Behavior of a Directionally Solidified Nickel-Based Superalloy: Mechanistic and Microstructural Aspect
No full textIn the present research, efforts were made to understand the mechanistic and microstructural aspects of the low cycle fatigue failure of a directionally solidified (DS) nickel-based superalloy under relevant operating conditions. The differences between the dislocation structures observed during different temperatures and strain amplitudes are clearly shown in the transmission electron (TEM) micrographs and are giving rise to the divergence in associated LCF responses. The deformation mechanism changes as a function of temperature. While shearing of gamma '-precipitates by stacking faults is the dominant deformation mechanism at the lowest temperature (750 degrees C), gamma '-coarsening and dislocation networks are prevalent at the highest temperatures (930 degrees C). Mixed deformation behavior is observed at the intermediate temperature (850 degrees C). Constituent's phases of the alloy also play crucial roles during deformation
Laboratory-Scale Tests for the Utilization of High Ash Non-Coking coal in Coke-Making Process
No full textIndia has vast coal resources all over the country; however, the presence of high ash content makes them invulnerable for industrial usage. To compensate for the rapid depletion of high-quality coking coals and to compensate for the demand for coal in iron and steel sectors, coal cleaning or beneficiation and blending techniques have come into limelight for the usage of low-quality coal. In this paper, laboratory-scale experiments were performed on the utilization of Indian high ash non-coking coal (NCC) and imported semi-coking coal (SCC) for the coke preparation. At first, washability characteristics of Indian high ash coal were investigated by using jigging, spiral concentration, and sink and float density separation methods. The optimum cut-off density NCC and SCC coals were blended and sent for the caking properties analysis. Proximate and ultimate analysis, vitrinite reflectance, crucible swelling number, and caking index or roga index have been taken as the measure for the caking ability of coal blends
Effects of prior austenite grain size on impression creep and microstructure in simulated heat affected zones of boron modified P91 steels
No full textThe induction of this paper was to simplify the exaggeration effects of prior austenite size (PAG) size on microstructure, impression creep, creep-rupture life, creep-damage, and precipitate size in the sub-heat affected zones (sub-HAZs) of boron modified P91 steels. Simulation of sub-HAZs caused the manipulation in PAG size and microstructure. This manipulation reduced precipitate sizes (similar to 50%) in P91B samples that lead to a 20% reduction in the non-homogeneous distribution of size of precipitates. Evaluation of minimum creep-damage rate (MCR) suggested FG (type-IV) and B-CG (type-III) as weakest links having a critical PAG size of 17 mu m. But, creep-performance of B-CG was still better than most of the P91 samples. While PAG hardening limit was observed in CF/B-CF that made them the strongest links. Activation energy (AE) calculation showed that an increase in PAG size for P91 samples motivated MCR, inviting PAG embrittlement. While vice versa observed in P91B samples, inviting PAG hardening. P91B samples exhibited maximum creep-performance by the shrinking span of the creep-damage and increasing creep-rupture life. Mutual dependency between creep-rupture life and creep-damage showed that their relation was independent of microstructural features, thermal history, amount of deformation, and boron modifications. Whereas, limited creep-damage was found for samples having normalized creep-rupture life >= 2. This paper also discussed various diffusion mechanisms for sub-HAZs by simplifying inconsistency between calculated and actual AE that suggested both interstitial and substitutional nature of boron. Small-grained samples (PAG 17 um) had higher AE
Experimental investigation on the separation capabilities and limitation of Falcon semi-batch concentrator
No full textIn the present study, an attempt was made to establish the separation capabilities and limitations of Falcon Semi-batch concentrator. Experiments were performed with quartz-magnetite and quartz-ferrosilicon binary feed system. Three different feed grades of 5, 10, and 15% magnetite by weight was used to understand the sensitivity of separation efficiency against the feed grade. It was found that separation efficiency is higher for lower feed grade material. Experimental results indicate that the falcon concentrator's performance is poor below the concentration criterion ratio of 3. The Separation efficiency of Falcon concentrator was enhanced from 15.3% to 66.1%, only by increasing the concentration ratio from 2.4 to 3
Wear Mechanism of High Chromium White Cast Iron and Its Microstructural Evolutions During the Comminution Process
No full textThe detailed deformation mechanism and its microstructural modifications of white cast iron grinding balls used in comminution have been investigated using transmission electron microscopy (TEM) and XRD. De-shaping is the primary mode of ball consumption, and fracture of balls is a relatively uncommon failure mode. Deshaping is the manifestation of abrasive wear caused during the operation, and abrasive wear is accompanied by microstructural changes. Micro-cutting is the foremost mechanism. The original microstructure of the matrix of unused grinding balls was observed to have twinned martensite with omega phase with an orientation relation of M-(1 (2) over bar1)//T-((1) over bar2 (1) over bar) and {(1) over bar(1) over bar3}M//{11 (3) over bar }T and M-(1 (2) over bar 10)//omega(0 (1) over bar 10) and {(1) over bar(1) over bar3}M// {1 (2) over bar 1 (3) over bar}omega. However, the presence of unstable omega phase, located at the twinning boundary, causes detwinning and forms lath martensite during tempering caused by localized heat during abrasion. Nano-cementite is formed at lath boundaries. Some cracking was observed, but the crack orientation is radial, indicating a response to tangential stresses associated with abrasion as opposed to dynamic stress waves from high-angle impact. Tangential tensile stresses due to surface traction during the abrasion process lead to radial cracks in brittle eutectic carbides, which join up and cause material removal
High-Temperature Simulation of Continuous Casting Mould Phenomena
No full textThe present investigation describes experimental simulation methods to evaluate the performance of mould powder during the continuous casting of peritectic steel. The dip mould simulator method developed in this investigation will take into account the actual mould powder along with the steel to be cast and certain casting parameters (casting speed, oscillation frequency and stroke) to evaluate the suitability of casting steel in the continuous caster. Another experimental technique akin to industrial practice has also been designed and proposed to study the melting behaviour of mould powder. Melting rate determined in this study for peritectic grade flux is in agreement with the theoretical melting rate estimated using a method proposed by K.C. Mills. The cast structure obtained from the dip mould simulator possesses oscillation marks and other features (slag infiltration) akin to the industry practice
Failure Analysis of a Steam Superheater Tube of a Vacuum Distillation Unit (VDU) in a Petrochemical Industry
No full textThe aim of this investigation is to examine the
premature failure of a low-pressure steam superheater tube
used in a vacuum distillation unit of a petrochemical
industry. Failure of the heater tube occurred in the form of
leakages of fluid during the hydrostatic test. Visual observation
of the failed tube revealed several fine cracks on the
outer surface of the tube and localized corrosion pits/cavities
on the inner surface of the tube. Chemical
composition, hardness and tensile properties of the failed
tube conform to the designated standard of ASTM A335
P11 grade of steel. The microstructure of the tube comprises
ferrite–pearlite structure without any remarkable
microstructural degradation. SEM micrographs of the
leaked surface revealed the presence of fatigue cracks
generated because of fluctuating thermal stresses experienced
due to frequent shutdowns during plant operation.
Fatigue cracks were found to originate from the pits/cavities
on the inner surface of the tube. Pits/cavities were
formed because of localized corrosion due to the presence
of excess dissolved oxygen in the water along with S and
Cl
Annual Report 2019-2020
Get PDFIt contains the statement of R&D works undertaken, achievement made and the expenditure by the laboratory during the financial year 2019-2020