Apurbba Kumar Sharma

Microwave Processing of Materials and Applications in Manufacturing Industries: A Review

The main focused aim of developing new processing and manufacturing technologies are to reduce production or manufacturing costs, processing times, and to enhance manufactured product properties. The developed processing techniques should be widely acceptable for all types of materials including metal matrix composites, ceramics, alloys, and fiber reinforced plastics. Microwave materials processing is emerging as a novel processing technology which is applicable to a wide variety of materials system including processing of MMC, FRP, alloys, ceramics, metals, powder metallurgy, material joining, coatings, and claddings. In comparison to the conventional processes, microwave processing of materials offers better mechanical properties with reduced defects and economical advantages in terms of power and time savings. The present review work focuses mainly on global developments taking place in the field of microwave processing of materials and their relevant industrial applications.

Microwave glazing of alumina–titania ceramic composite coatings

Abstract The application envelop of atmospheric plasma sprayed ceramic composites can be widened considerably by reducing/eliminating inherent surface defects by treating them through techniques like microwave irradiation. In microwave processing, microwave energy is directly applied to the material. High-frequency microwaves (>1 GHz usually) penetrate into the bulk of the material and the volumetric interaction of the electromagnetic fields with the material results in dielectric (volumetric) heating. This leads to higher heating efficiency with faster processing. Ceramics are transparent to microwaves at low temperatures, however, start absorbing microwaves at higher temperatures resulting change in microstructure and material characteristics. This paper presents microwave processing of atmospheric plasma sprayed alumina–titania ceramic composite coatings in conventional microwave heating system and evaluation of the processed materials through XRD, SEM, microhardness survey and surface finish with illustrations. Results indicate microwave irradiation induces densification of the material and possible flow of dominant gamma-alumina phase that leads to glazing of coated surface. Glazed surfaces exhibit enhanced microhardness as well as surface finish.

Behavior of Kevlar/Epoxy Composite Plates Under Ballistic Impact:

This study investigates the ballistic response of laminated composite plates using numerical simulations. Numerical simulations were carried out to determine the ballistic response of thick Kevlar/epoxy composite plates, commonly used in body armor. These plates were impacted at velocities between 100 and 1000 m/s. The numerical parametric study of ballistic impact caused by cylindrical projectile is undertaken to obtain an estimate for the ballistic limit velocity, energy absorbed by the plate, and the contact duration. The effect of mass and diameter of the projectile on ballistic limit velocity was also studied. The results obtained hereby are in good agreement with the experimental data presented by other researchers.

A Review of Research Trends in Microwave Processing of Metal-Based Materials and Opportunities in Microwave Metal Casting

ABSTRACT Microwave processing of materials has emerged as a new method for processing of a variety of materials in the recent years. Microwaves have been used effectively with significant advantages, particularly in food processing and chemical synthesis. They are also found to be efficient for processing polymers, ceramics, polymeric composites, and ceramic composites. The physics of interaction of microwaves with characteristically different materials is not yet explored well; consequently, there are challenges in microwave processing of metal-based materials. Industrial processing of bulk metal is yet to be popular in spite of the fact that the feasibility of metal powder sintering was demonstrated a few decades ago. This article provides a summary of fundamental aspects of microwave processing of metal-based materials and their interaction with metallic materials. The processing challenges have been surveyed; developments in terms of techniques and tooling have been analyzed. Possible effects of microwave processing on metallic materials, in particular metal powders, bulk metals, bulk metal-metal powder systems, and sheet metals have been presented. Future research aspects of microwave processing of metallic materials with reference to metal casting have been identified.

A novel route for joining of austenitic stainless steel (SS-316) using microwave energy

Material processing through microwaves is a challenging area of research. The present work illustrates an application of the developing technology of joining bulk metallic materials through microwave heating. Stainless steel (SS-316) in bulk form was used as candidate material to be joined. Joining of bulk SS-316 was carried out using a multimode microwave applicator at the frequency of 2.45 GHz and power of 900 W. Joining was effected through fusing and metallurgical bonding of a sandwich layer between the bulk pieces. Heating in the sandwich layer was selectively induced by exposing it to controlled microwave radiation for a predetermined period. The joints were characterized through field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and measurement of Vickers microhardness, porosity, and tensile strength. The FE-SEM study showed that the faying surfaces are well fused and get bonded with base material. Examination of the joint microstructure showed cellular-like growth in the entire joint region. The average Vickers microhardness of the core of the joint area was observed to be 290±14 Hv; however, that in the interface zone was found to be significantly higher (∼420±15 Hv). Precipitation of metallic carbides occurred predominantly in the joint interface region. Porosity measurement in the joint area revealed negligible porosity (0.78 per cent). Evaluation of the tensile properties of the joints showed an ultimate tensile strength of the order of 309 MPa with an elongation of 11.50 per cent.

On Friction and Wear Behavior of WC-12Co Microwave Clad

In the present work, the friction and wear behavior of microwave-clad WC-12Co cermet was examined using a pin-on-disk tribometer as per ASTM G99. Microwave clads were tested against an EN-31 countersurface in unlubricated conditions. The WC-12Co clads were developed using an industrial microwave applicator at 2.45 GHz and 1.4 kW. The influence of varying normal load on the tribological characteristics of the microwave-induced clads have been investigated. Responses of the WC-12Co microwave clads and AISI 304 stainless steel substrate were monitored and the resulting wear was subsequently analyzed in terms of wear rate, pressure–velocity–time (p-v-t) characteristics, and friction coefficient. The worn surfaces of the WC-12Co microwave clad and AISI 304 substrate were studied using scanning electron microscope. Wear debris was analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The developed clads exhibit significant resistance to wear attributable to the microwave-induced dense microstructure and material properties. The wear rate and friction coefficient were reduced by 67 and 56%, respectively for WC-12Co microwave clad compared to that of the AISI 304 substrate.

Developments in abrasive flow machining: a review on experimental investigations using abrasive flow machining variants and media

The abrasive flow machining (AFM) technique uses a self-deforming tool, an abrasive laden media that is passed back and forth in the passage geometry of the hollow workpiece with the assistance of two hydraulically operated cylinders placed opposite to each other. The material is removed by abrasion generating finer surfaces in the area where flow is restricted. As the time advances various variants of AFM have been developed by different researchers to increase the productivity and improve the surface finish. Thus a combination of AFM and its process variants were developed to increase material removal rate and surface finish. This article provides a comprehensive review of recent developments in the process variants of AFM and the respective media.

Some aspects of centrifugal force assisted abrasive flow machining of 2014 Al alloy

Abstract Finish machining of precision components constitutes one of the most challenging and expensive stages in a manufacturing process. Abrasive flow machining (AFM) is a non-traditional machining technique that deburrs, polishes, and radiuses surfaces and edges by flowing an abrasive-laden medium over these areas. The process is used in particular for internal shapes that are difficult to process by other non-conventional machining processes. A low material removal rate happens to be one serious limitation of this process. This paper discusses a few of the issues arising when attempting to enhance the capabilities of the conventional AFM process. In this process, a centrifugal force is imparted to the abrasive particles in the medium, making the process a hybrid one. The set-up has been suitably modified for this purpose, and the resulting process is called centrifugal force assisted abrasive flow machining (CFAAFM). The effect of key parameters on the performance of the process has been studied through response surface methodology (RSM). Relationships were developed for material removal and percentage improvement in surface finish of cast Al alloy (2014) cylindrical components. Analysis of variance (ANOVA) has been applied to identify significant parameters. Experimental results indicate the significantly improved performance of CFAAFM over AFM in terms of enhanced surface finish and material removal. It was observed that the combination of a high extrusion pressure and a higher speed of the centrifugal force generating (CFG) rod is more favourable to obtain a higher degree of surface finish, while the combination of a larger grain size and a higher speed of the CFG rod causes higher material removal.

Tool wear studies in fabrication of microchannels in ultrasonic micromachining.

Form accuracy of a machined component is one of the performance indicators of a machining process. Ultrasonic micromachining is one such process in which the form accuracy of the micromachined component significantly depends upon the form stability of tool. Unlike macromachining, a very small amount of tool wear in micromachining could lead to considerable changes in the form accuracy of the machined component. Appropriate selection of tool material is essential to overcome this problem. The present study discusses the effect of tool material, abrasive size and step feed in fabrication of microchannels by ultrasonic machining on borosilicate glass. Development of microchannels using ultrasonic micromachining were rarely reported. It was observed that tungsten carbide tool provided a better form accuracy in comparison to the microchannel machined by stainless steel tool. The tool wear mechanism in both materials is proposed by considering scanning electron micrographs of the tool as evidence. A one factor at a time approach was used to study the effect of various process parameters.

Dry erosion wear performance of Inconel 718 microwave clad

Abstract This paper reports on the dry erosive wear performance of Inconel 718 clads deposited on SS-304 substrates through microwave hybrid heating technique. Clads were deposited using a domestic microwave applicator at 2·45 GHz and 900 W. The microstructural observations of the Inconel 718 clad indicate good metallurgical bonding with the substrate and revealed no visible interfacial cracking. The microhardness of the clads was assessed using a Vicker’s microhardness tester and the average microhardness in the clads was 564±22 HV. Erosive wear performance of the clads was evaluated using an air jet erosion test setup as per ASTM G76 standard. The effect of varying impact angle was studied; the results have been discussed with the help of SEM images of the worn surfaces. It was observed that the improved erosive performance of the Inconel 718 clads was due to presence of strengthening intermetallic phases (Ni3Ti, Ni3Al) in the tough Ni–Fe–Cr matrix.