D. R. Peshwe

Deep Subzero Processing of Metals and Alloys: Evolution of Microstructure of AISI T42 Tool Steel

The improvement in the life of tool and alloy steels, when treated at 88 K for 24 hours has been conclusively established. It is however not clear as to what factors of the Deep Subzero process (DSZ) actually contribute towards improved performance of tools. It is also not clear, whether treatment for 24 hours is applicable to all steels or not. In the present investigation, an attempt to study the evolution of microstructure in AISI T42 high speed steel during DSZ treatment is performed. The results indicate clear evidence of changes beginning within the first 8 hours of DSZ. Changes in the morphology of carbides with the phenomenon of dissolution, precipitation, and merging are observed. Scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) were used during the investigation.

Determination of Silica Activity Index and XRD, SEM and EDS Studies of Amorphous SiO2 Extracted from Rice Husk Ash

Rice husk ash (RHA) contains 20% SiO2 in hydrated amorphous form (Si–OH). On thermal treatment, the SiO2 converts to cristobalite, the crystalline form which is not reactive. However under controlled conditions, amorphous SiO2 with high reactivity is produced. Therefore rice husk has been one of the useful bio-mass. The silica activity index was determined to be equal to 97.73 which was used to determine the percentage of amorphous SiO2 in RHA. The values of the soluble fraction and silica activity index were also stated. Comparative study of amorphous and crystalline SiO2 done by X-ray diffraction revealed the total amorphous nature of SiO2. The scanning electron microscopy (SEM) images displayed the comparative morphological features of the rice husk and RHA. The energy dispersive spectroscopy analysis of rice husk was done to determine the presence of SiO2 on the upper portion of rice husk and to determine the percentage of SiO2 in RHA. The SiO2 particles in an agglomerated form was found to be of micron size when observed under SEM.

Effect of Cryogenic Processing on Surface Roughness of Age Hardenable AA6061 Alloy

The aging phenomenon in age hardenable aluminum alloys is complex and well under research. The supersaturated solid solution of these alloys, during aging, undergoes complex precipitation causing increase in strength with time. These alloys have wide range of applications in the aviation and automotive industry. The properties such as electrical conductivity and hardness of these alloys are well related to its precipitation behavior. Cryogenic treatment (CT) has been tried on tool and alloy steels where it has been found that this treatment positively affects the wear resistance and also causes uniformity in structure. The CT has become an important step in the manufacturing of tool steels. This work comprises applying CT at −185°C to AA 6061 aluminum alloy for various time periods. The treatment was sequenced in the conventional solutionizing and artificial aging. This sequence of treatment has not been reported in the literature. The characterization was done using scanning electron microscopy. The behavior of this alloy to the treatment was identified by measuring electrical conductivity and hardness. The surface roughness of this alloy was also found to be highly influenced by this treatment.

Influence of cobalt on the cryogenically treated W-Mo-V high speed steel

The presence of cobalt in high speed steels is of great interest to researchers and the users as well. Although cobalt bearing high speed steels are used on commercial basis, the influence of cobalt in cryogenically treated high speed steels is still under scanner. Some researchers have found the effect of cobalt as negative, as it adversely affects the wear properties and fracture toughness of some high speed steels under certain conditions. This paper takes a review of influence of cobalt in tool steels with the past research and discusses the experimental results of the effect of cryogenic treatment on 10%Co bearing AISI T42 high speed steel. It has been found that this steel has an advantage due to the presence of Cobalt with respect to wear characteristics after the cryogenic treatment. It is also found that the cycle time of cryogenic processing of this super high speed steel shortens due to the presence of cobalt.

Failure Analysis of Bed Coil Tube in an Atmospheric Fluidized Bed Combustion Boiler

The Atmospheric Fluidized Bed Combustion Boilers have advantages as compared to conventional coal fired boilers in respect of heat transfer, SOx, NOx, emissions and efficiency. In the present study, the failure analysis of bed coil tube, used in atmospheric fluidized bed combustor was studied. The failure studies included physical, chemical and metallurgical analysis and the results analyzed reveal that the failure is typically due to caustic gouging. The cause of failure has further been substantiated using scanning electron microscopy with energy dispersive X-ray analysis as well as X-ray diffraction analysis.

Photoluminescence characterisation of Zn1-xCdxAl2O4:Eu nanophosphor for solid state lighting

All the phosphor are prepared as Zn1-x-yCdxAl2O4:Euy by combustion method. The formation of crystalline aluminates was confirmed by X-ray diffraction. The prepared phosphor was characterised by SEM, EDS, particle size analyser and photoluminescence (PL) techniques. The PL emission spectra of Zn1-x-yCdxAl2O4:Euy phosphor shows prominent peaks at 613 nm and 580 nm (excited by 394 nm wavelengths). It is also observed that the Eu ions are incorporated in trivalent form. The Eu ion concentration is kept constant at 0.5 mol% and Cd concentration varies from 0.1 mol% to 1 mol% in the host lattice. The increase in concentration of Cd ions increases the PL emission intensity. So it is clear that the replacement of Zn ion into Cd ions increased the crystallinity, hence, increases the PL intensity. The SEM and particle size analyser results indicate that the prepared phosphor are in nanosize and increase in concentration of Cd ions increases the particle size of phosphor.

Alteration of the electronic structure and the optical properties of graphitic carbon nitride by metal ion doping

The photoluminescence quenching of graphitic carbon nitride (GCN) was systematically investigated with the doping of transition metal ions. The photoluminescence spectra of metal doped and pristine GCN were monitored and the trend of quenching efficiency was found to be Cu2+ > Co2+ > Mn2+. Interestingly, with the increasing doping concentration of different metal ions simultaneous red shift and luminescence quenching was determined in the photoluminescence spectra as well as increased absorption tail in longer wavelength hence enhancement in the bandgap. The change in the optical properties could be mainly due to structural reconstruction and doping induced electronic redistribution is discussed.

Effect of Cryo-Ageing at Liquid Nitrogen Temperature and Subsequent Thermal-Annealing on the Interface of Talc Filled Polypropylene with Different Particle Size

Polypropylene (PP) based materials are widely used because of their low cost, good processability and good balance of properties but its low stiffness and strength greatly hinders its even wider utilization. In order to overcome this, PP is reinforced with different fillers. In composites; the issue of interface between the filler and matrix is of importance. Thus in the present paper, the effect of cryo-ageing and subsequent thermal-annealing on the PP-talc filled composites have been studied to monitor its effect on the interface. The composites with talc of different particle sizes are examined for mechanical and structural properties after treatment. The mechanical properties are evaluated by testing its tensile strength and wear performance, whereas, the study of structural properties by FTIR and SEM reveals some structural changes. These results have further been discussed and evaluated to find out the effect of these treatments on interface of various selected talc filled PP composite.

Effect of Temper Conditions on Abrasive Wear Behavior of AA7010 Alloy

AbstractThe 7xxx series alloys are used mainly in transportation industries for manufacturing vehicles due to their unique properties such as high specific strength and specific stiffness. Wear of the engine component is one of the major problems in vehicle manufacturing industries. This paper investigates wear behavior of AA7010 alloy used in transportation industries. The Al–Zn–Mg–Cu alloy solutionized and aged at various temper conditions was studied for wear using pin-on-disc machine. The characterization of the wornout surface was carried out. To study the wear mechanism, wornout surfaces were examined under scanning electron microscope. From the analysis, it was concluded that change in specific wear rate of AA7010 alloy was associated with change in hardness and microstructural constituents. Specific wear rate of peak aged and retrogression reaged RRA treated alloy were comparable. Maximum hardness in peak aged and retrogression reaged (RRA) treated alloy resulted in minimum specific wear rate as compare to solution treated and overaged alloy.

An assessment of mechanical properties of P92 steel weld joint and simulated heat affected zones by ball indentation technique

ABSTRACT Mechanical properties of P92 steel weld joint fabricated by shielded metal arc welding were evaluated using ball indentation (BI) technique. Microstructure of the P92 weld joint consisted of the weld metal, coarse grain region, fine grain region, intercritical region and base metal. The individual microstructural regions of the heat affected zones (HAZs) were separately prepared by heat treating the steel at particular temperatures. Ball indentation and uniaxial tensile tests were carried out across the weld joint and on the simulated HAZ microstructures at temperatures of 300 K (27 °C) and 623 K (350 °C). The tensile strengths gradually decreased from weld metal to the base metal with trough in the intercritical region (ICR) of the joint and simulated at 1173 K (900 °C) steel. The formation of coarser M23C6 precipitates and sub-grain formation with reduced dislocation density led to soften the ICR/simulated at 1173 K (900 °C) steel than the other regions of the joint. The variation of mechanical properties across the joint was comparable with variation of hardness and microstructural constituents across the joint.