Dheeraj Gupta

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.

Recent applications of microwaves in materials joining and surface coatings

The conventional methods of manufacturing and materials processing are getting obsolete owing to the higher energy consumptions, large processing times and poor characteristics of processed components. The limitations of conventional processing techniques for processing of large varieties of advanced materials which includes metal matrix composites, ceramics, cermets, metallic alloys, functionally graded materials and fiber-reinforced plastics forced researchers to find alternative and novel methods of manufacturing and material processing, which can overcome the limitations of conventional methods. Hence, it is mandatory to develop a new concept for processing advanced materials, which can provide better mechanical properties, reduced defects and economic advantages in terms of power and time savings. Microwave material processing emerged as one of the novel methods of material processing which can satisfy the present requirements and can yield a better product at reduced costs and processing time. This article discusses some of the novel recent applications of microwaves in the area of manufacturing.

Optimization of process parameters for drilled hole quality characteristics during cortical bone drilling using Taguchi method.

Orthopaedic surgery involves drilling of bones to get them fixed at their original position. The drilling process used in orthopaedic surgery is most likely to the mechanical drilling process and there is all likelihood that it may harm the already damaged bone, the surrounding bone tissue and nerves, and the peril is not limited at that. It is very much feared that the recovery of that part may be impeded so that it may not be able to sustain life long. To achieve sustainable orthopaedic surgery, a surgeon must try to control the drilling damage at the time of bone drilling. The area around the holes decides the life of bone joint and so, the contiguous area of drilled hole must be intact and retain its properties even after drilling. This study mainly focuses on optimization of drilling parameters like rotational speed, feed rate and the type of tool at three levels each used by Taguchi optimization for surface roughness and material removal rate. The confirmation experiments were also carried out and results found with the confidence interval. Scanning electrode microscopy (SEM) images assisted in getting the micro level information of bone damage.

Copper coating on austenitic stainless steel using microwave hybrid heating

Coating of copper on austenitic stainless steel (SS-316) is useful where high thermal conductivity as well as high electrical conductivity along with high strength is desirable. Common applications of these coatings include aerospace systems such as space stations and satellites. Usually, chemical vapour deposition (CVD) and physical vapour deposition (PVD) techniques are employed for developing such coatings. In the present work, copper coatings with an average thickness of 230 micrometers were successfully developed on SS-316 substrates using microwave hybrid heating (MHH) technique. The MHH technique was employed in order to enhance the coupling efficiency of the target material (metallic copper powder) with the incident microwaves at room temperature. Copper powders of average grain size 5 micrometers were melted and deposited on the steel substrates by controlled exposure of microwave radiation of 900 W at 2.54 GHz frequency in a multi-mode applicator. Coatings were analysed through energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and measurement of microhardness. The developed coatings were reasonably uniform, dense, and homogenous, although the presence of micropores was detected. Coatings were formed by necking, followed by agglomeration, and fusing of melted copper particles during microwave irradiation. Microstructure of the developed coatings consists of 3-D chain like arrays of the fused particles. The presence of oxides of copper in the deposits has been confirmed. The coatings so developed had a mean hardness of 270±30 HV.

Comparative study for surface topography of bone drilling using conventional drilling and loose abrasive machining

Drilling through the bone is a complicated process in orthopaedic surgery. It involves human as a part of the work so it needs better perfection and quality which leads to the sustainability. Different studies were carried out on this curious topic and some interesting results were obtained, which help the orthopaedic surgeon on the operation table. Major problems faced during bone drilling were crack initiation, thermal necrosis and burr formation. The surface topography of the bone is an indirect indication for the sustainability of bone joint. In this study, a comparison is made between conventional and a loose abrasive unconventional drilling technique for the surface characterization of the bone. The attempt has been made to show the feasibility of bone drilling with non-conventional technique and its aftereffect on the bone structure. The burr formation during conventional bone drilling was found to be more which leads to problems such as crack initiation and thermal necrosis. Scanning electrode microscope and surface roughness tester were used to characterize the surface of the fine drilled bone specimen and the results testified quite better surface finish and least crack formation while drilling with loose abrasive unconventional technique.

Processing and characterization of composite cladding through microwave heating on martensitic steel

The composite wear resistant cladding of nickel-based powder matrix and 10% SiC powder as reinforced was developed through microwave hybrid heating on martenisitic stainless steel (SS-420) substrate. The development of the clad has been carried out by using a domestic microwave applicator of frequency 2.45 GHz and 900 W power level. The microstructural and mechanical characterizations of the developed clad were carried out by using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and Vicker’s microhardness analysis. Results revealed that clads of approximately 1.25 mm thickness were developed with significantly low porosity (∼1.10%). The scanning electron microscopic results show that the microstructure of clad exhibits typical cellular-like structure. The metallurgical bonding between clad and substrate surface was obtained with partial dilution. The complex carbides of chromium and silicides of chromium, iron, and nickel phases were identified in the clad region by XRD study, which may enhance the Vicker’s microhardness of the clads significantly. The average Vicker’s microhardness of the developed clad was in the range of 652 ± 90 HV.

Microwave melting and processing of metal–ceramic composite castings

Applications of metal–ceramic composites are increasing in advanced materials field; however, efficient utilization of these materials depends on the cost involved in processing and structure–properties correlations. Processing of materials through microwave energy has already been accepted as a well-established route for many materials. In this work, composites of nickel-based metallic powder (matrix) and SiC powder (reinforcement) were successfully casted by microwave heating. The mechanism for the development of composite castings using microwaves is discussed with proper illustrations. The results of microstructure analysis of the developed cast revealed that uniform equiaxed grain growth with uniform dispersion of reinforcement. The results of X-ray diffraction analysis revealed that during microwave heating some metallurgical changes took place, which led to higher microhardness of cast. Micowave processed casting revealed lower defects (~1.75% porosity) and average Vickers microhardness of 920 ± 208 HV. This work reports the successful applications of microwaves in manufacturing, in the form of melting and casting of metallic powders.

On surface modification of austenitic stainless steel using microwave processed Ni/Cr3C2 composite cladding

ABSTRACT In the present work Ni-based + 20% Cr3C2 composite clads were developed on SS-304 austenitic stainless steel through microwave hybrid heating technique. Experimental trials were conducted inside a domestic microwave applicator at 2.45 GHz and 900 W. The developed microwave composite clads were characterised through SEM/EDS, XRD and Vicker’s micro-hardness tests. Further tribological wear behavior of the so developed clad was investigated using pin-on-disc type tribometer under dry sliding wear conditions. Microstructural analysis revealed the uniform dispersion of Cr3C2 particles inside the Ni matrix in the form of cellular-like structure. The presence of FeNi3, NiSi, Cr3Ni2 and chromium carbide (Cr3C2) was confirmed from the XRD analysis, which contributes to the increase in micro-hardness of the composite clad. The average value of micro-hardness of the developed clads was found to be 450 ± 55 HV. The microwave-processed clad exhibits three times more wear resistance than SS-304 substrate.

An approach for functionally graded cladding of composite material on austenitic stainless steel substrate through microwave heating

In the present work, functionally graded clads of Ni-SiC material have been developed on austenitic stainless steel (SS-304) substrate through 2.45 GHZ domestic microwave applicator. The functionally graded clads were processed by the concept of hybrid heating with varying exposed microwave power levels from 180 to 900 W. The optimum exposure time of 900 W microwave power was varied with compositional gradient and it is from 300 s to 420 s. The maximum thickness achieved for functionally graded clads was 2 mm at optimum exposure power and time. The microstructural analysis of developed clads reveals that the partial mutual diffusion between each successive layer took place and it confirms the metallurgical bonding in between. The typical flower like structure of Ni-matrix has been observed in clads where the SiC particles were uniformly dispersed. The maximum functionally graded clads micro-hardness of 1020 ± 30 HV were achieved.

Multi-objective performance investigation of orthopaedic bone drilling using Taguchi membership function:

Orthopaedic bone drilling attacks the surrounded bone cells and tissues in terms of thermal and mechanical in such a way that these cells can get damaged permanently. This damage to the surrounding of drill point upsurges the rehabilitation time of injury and in some cases leads to the failure of the bone screw joint. This study is based on the optimization of multiple response characteristics to minimize the damage during the bone drilling. All real-life problems, including bone drilling, require the multiple response optimization for getting a combined optimization result for all countable response characteristics. The Taguchi optimization technique is observed as a highly recommended tool for single response optimization. This article uses the Taguchi technique with little modification of membership function that will help to convert the multiple response characteristics into single response and further optimize it as a single function of performance. Rotational speed, feed rate of tool at three different levels with three different kinds of drilling tools are the drilling parameters selected for the study. The objective of this study is to minimize the surface roughness and thrust force simultaneously. Analysis of variance helps to find the percentage contribution and significance of each parameter on the performance.