Hiralal Bhowmick

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.

Tribology of ethylene-air diffusion flame soot under dry and lubricated contact conditions

Soot particles are generated in a flame caused by burning ethylene gas. The particles are collected thermophoretically at different locations of the flame. The particles are used to lubricate a steel/steel ball on flat reciprocating sliding contact, as a dry solid lubricant and also as suspended in hexadecane. Reciprocating contact is shown to establish a protective and low friction tribo-film. The friction correlates with the level of graphitic order of the soot, which is highest in the soot extracted from the mid-flame region and is low in the soot extracted from the flame root and flame tip regions. Micro-Raman spectroscopy of the tribo-film shows that the a priori graphitic order, the molecular carbon content of the soot and the graphitization of the film as brought about by tribology distinguish between the frictions of soot extracted from different regions of the flame, and differentiate the friction associated with dry tribology from that recorded under lubricated tribology.

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.

Tribology of soot suspension in hexadecane as distinguished by the physical structure and chemistry of soot particles

Ethylene gas is burnt to generate soot which is collected thermophoretically from different locations of the flame. Tribological performance of the collected soot in hexadecane suspension is compared with that of carbon black and diesel soot. The soots are analysed to yield a range of mechanical properties, physical structures and chemistry. The paper correlates these property variations with the corresponding variations in friction and wear when the soot suspended in hexadecane is used to lubricate a steel on steel sliding interaction. The particles are dispersed in hexadecane by a non-ionic surfactant, poly-isobutylene succinimide (PIBS), which is mono-functional with no free amine group. The grafting of the surfactant on the soot particles is found to have a profound effect on the dispersion of the soot, in general, while, between the different soot types, the tribology is differentiated by the physical structure and chemistry.

Dry tribology and nanomechanics of gaseous flame soot in comparison with carbon black and diesel soot

Ethylene gas is burnt and the carbon soot particles are thermophoretically collected using a home-built equipment where the fuel air injection and intervention into the 7.5-cm long flame are controlled using three small pneumatic cylinders and computer-driven controllers. The physical and mechanical properties and tribological performance of the collected soot are compared with those of carbon black and diesel soot. The crystalline structures of the nanometric particles generated in the flame, as revealed by high-resolution transmission electron studies, are shown to vary from the flame root to the exhaust. As the particle journeys upwards the flame, through a purely amorphous coagulated phase at the burner nozzle, it leads to a well-defined crystalline phase shell in the mid-flame zone and to a disordered phase consisting of randomly distributed short-range crystalline order at the exhaust. In the mid-flame region, a large shell of radial–columnar order surrounds a dense amorphous core. The hardness and wear resistance as well as friction coefficient of the soot extracted from this zone are low. The mechanical properties characteristics of this zone may be attributed to microcrystalline slip. Moving towards the exhaust, the slip is inhibited and there is an increase in hardness and friction compared to those in the mid-flame zone. This study of the comparison of flame soot to carbon black and diesel soot is further extended to suggest a rationale based on additional physico-chemical study using micro-Raman spectroscopy.

On processing of Ni-WC based functionally graded composite clads through microwave heating

ABSTRACT Present study focuses on the development of four layered functionally graded clads (FGC) of Ni-WC based composite material on AISI 304 substrate through microwave heating route. Experimental trials were conducted inside a microwave applicator of domestic type at frequency range of 2.45 GHz. The optimal exposure time of 900 W microwave power was varied with compositional gradient and it was from 300 to 360 s. The mechanism of FGC formation through microwave heating was explained and developed FGC was subjected to mechanical and microstructure characterizations. The results of micro-structural analysis revealed that the FGC of ∼1.8 mm thickness was produced and was free from any type of interfacial cracks and visible porosity. It was observed that WC particles were randomly dispersed in the nickel matrix. XRD study revealed the formation of inter-metallics, such as NiW4, NiSi, and Cr23C6. Maximum value of microhardness was observed in the top FGC layer and was 880 ± 30 HV.

On Processing of Ni–WC8Co-based Composite Clads on Austenitic Stainless Steel Through Microwave Energy

In the present investigation, composite clads of Ni + 20% WC8Co and Ni + 30% WC8Co were developed on austenitic stainless steel (SS-316) using microwave energy. Experiments trials were carried out inside a domestic microwave oven with a frequency range of 2.45 GHz and variable power level of 180–900 W. The exposure time and power level for developing clads were optimized. The microwave processed clads were further characterized through SEM/EDS, XRD, and measurement of Vicker’s microhardness. Microstructural results revealed that the clads of approximately 0.7 mm thickness were free from any type of interfacial cracks and voids. WC particles were uniformly distributed inside soft Ni matrix. The presence of NiSi, Co3W3C, Fe6W6C, NiW, NiCr, and FeNi3 phases was observed during phase analysis of developed composite clads. Microhardness of the Ni + 20% WC8Co and Ni + 30% WC8Co was found to be 810 ± 75 and 923 ± 65 HV, respectively.

Surface modification of SS-316L steel using microwave processed Ni/WC based composite clads

In the present investigation, the claddings of Ni/WC based composite powder were developed on SS-316L steel through microwave hybrid heating method. The experimental trials were carried out inside a domestic microwave oven working at 2.45 GHz and 900 W. The so developed composite clads were characterized using XRD, Vicker’s microhardness measurement, and SEM/EDS. The presence of different phases like Co3W3C, NiW, FeNi3, NiSi was confirmed by XRD analysis. Microstructural analysis revealed that the clad of approximately 0.6 mm thickness was developed with no interfacial cracks and negligible porosity. The WC particles were uniformly distributed in the form of cellular structure inside Ni matrix. The average Vicker’s microhardness value of the clad section was observed as 925±50 HV, which is three times that of the SS-316L substrate.In the present investigation, the claddings of Ni/WC based composite powder were developed on SS-316L steel through microwave hybrid heating method. The experimental trials were carried out inside a domestic microwave oven working at 2.45 GHz and 900 W. The so developed composite clads were characterized using XRD, Vicker’s microhardness measurement, and SEM/EDS. The presence of different phases like Co3W3C, NiW, FeNi3, NiSi was confirmed by XRD analysis. Microstructural analysis revealed that the clad of approximately 0.6 mm thickness was developed with no interfacial cracks and negligible porosity. The WC particles were uniformly distributed in the form of cellular structure inside Ni matrix. The average Vicker’s microhardness value of the clad section was observed as 925±50 HV, which is three times that of the SS-316L substrate.

An approach for developing nickel–alumina powder-based metal matrix composite cladding on SS-304 substrate through microwave heating:

In the present study, metal matrix composite clads of nickel–alumina powder-based material have been produced on austenitic stainless steel (SS-304) substrate using microwave heating at 2.45 GHz frequency. A concept of hybrid heating was used to process metal matrix composite clads at exposure power level of 900 W. The exposure time for developing metal matrix composite clads was varied from 60 to 300 s. The clads of average thickness 0.6 mm were successfully developed at an optimized exposure time of 300 s. The microstructural analysis of microwave processed clads reveals the uniform dispersion of alumina powder particles inside nickel matrix. The developed clads were free from any type of interfacial cracks and were metallurgically bonded with SS-304 substrate. X-ray diffraction study confirmed the presence of alumina powder, FeNi3 and chromium carbide phases, which contributed to the increase in micro-hardness of developed clad. Clad micro-hardness was found to be four times that of austenitic stainless steel, which makes it suitable for anti-wear applications.