Pallav Gupta

Synthesis and characterization of Fe–ZrO2 metal matrix composites

This investigation reports the phase, microstructure and hardness of ZrO2-reinforced iron-based metal matrix composites synthesized by powder metallurgy. The process involved the preparation of homogeneous mixture of electrolytic iron powder with different weight percentages (5%, 10%, 20% and 30%) of ZrO2 by milling, compaction in the form of rod and sintering in the temperature range of 900–1100℃ for 1–3 h in argon atmosphere. The sintered samples were subjected to X-ray diffraction for phase analysis and to scanning electron microscopy for microstructure evaluation. The X-ray diffraction and scanning electron microscopy results show the presence of Fe, ZrO2 and Zr6Fe3O phases. This Zr6Fe3O phase is formed due to reactive sintering. From these studies it is concluded that two types of sintering are involved: (a) solid state sintering between Fe particles and (b) reactive sintering with the formation of iron zirconium oxide. Density and hardness of composite specimens were found to depend on fraction of ZrO2, the nature of sintering and the formation of Zr6Fe3O phases.

Effect of sintering on wear characteristics of Fe-Al2O3 metal matrix composites:

This article reports the results of investigation of tribological properties of 5 wt% Al2O3 reinforced iron-based metal matrix composite fabricated using powder metallurgy technique. Composition of the composite by weight was 95% Fe as a matrix material and 5% Al2O3 as reinforcement. Green compacts were sintered in an argon atmosphere in the temperature range of 900–1100  ℃ for 1 to 3 h. Dry sliding wear test were performed on the specimens using pin-on-disc wear and friction testing machine keeping the fixed sliding velocity as 4 m/s and sliding time as 60 min for loads of 0.5, 1.0 and 2.0 kg. Microstructure of weared specimens as studied by scanning electron microscope revealed that adhesive wear is more prominent at lower load where as abrasive wear is more prominent at higher load. Wear rate is also dependent on sintering temperature and time. This is explained in terms of densification, hardness and nature of wear occurring in the specimen.

Sintering and Hardness Behavior of Fe-Al2O3 Metal Matrix Nanocomposites Prepared by Powder Metallurgy

The present paper reports the investigations on sintering and hardness behavior of Fe-Al2O3 Metal Matrix Nanocomposites (MMNCs) prepared by Powder Metallurgy (P/M) route with varying concentration of Al2O3 (5–30 wt%). The MMNC specimens for the present investigations were synthesized by ball milling, followed by compaction and sintering in an inert atmosphere in the temperature range of 900–1100°C for 1–3 hours using Powder Metallurgy route. Phase and microstructures of the specimens were characterized by XRD and SEM. Reactive sintering takes place in these materials. During sintering nano iron aluminate (FeAl2O4) phase forms. Characterization was done by measuring density and hardness. Results have been discussed critically to illustrate the effect of various processing parameters on sintering and mechanical behavior. It is expected that the results of these investigations will be useful in developing Metal Matrix Nanocomposites (MMNCs) for typical industrial applications.

Metal Matrix Nanocomposites and Their Application in Corrosion Control

The present chapter gives an overview of nanocomposites which are novel materials for corrosion control. Nanocomposites comprise of more than one phase where size of each phase is less than 100 nm respectively. There are basically three types of nanocomposites: Ceramic-Matrix Nanocomposites, Metal-Matrix Nanocomposites and Polymer Matrix Nanocomposites. Several synthesis routes have been proposed for the fabrication of MMNCs such as Stir Casting, Powder Metallurgy, CVD, PVD etc. Major applications of metal matrix nanocomposites are in automobile and aerospace industries. Among various properties corrosion is an important property for determining the life expectancy of any nanocomposite material. In the present chapter a brief account of corrosion and its control using nanocomposites has been discussed. It is expected that the present chapter will help the readers to get a glimpse of nanocomposite materials for its wider use in industrial applications.

Design, Development and Application of Nanocoatings

Coatings can be defined as the application of one material on the other material usually known as substrate. They are mainly applied on the material to protect it from any degradation which occurs due to environmental conditions. They act as an interface between the substrate and the environment. Moreover, they are also used for decorative purposes. Nanocoatings are those coatings in which the size of a particle is in the range of 1–1000 nm at least in one dimension. Nanocoatings provide more wear resistance attributed to its higher toughness and hardness to the substrate as compared to other conventional coatings. They also provide antimicrobial, wrinkle resistance, stain resistance, hydrophobic and hydrophilic characteristics, UV protection and antistatic properties affecting the bulk properties of the substrate material. Nanocoatings can be manufactured by mainly two methods: vapour phase method and liquid phase method. Vapour phase method includes chemical vapour deposition, laser ablation, vapour condensation, plasma arc and flame synthesis processes. Liquid phase method includes sol–gel, precipitation, electrolysis, microemulsion and hydrothermal processes. Nanocoatings are used in aircraft (landing gears and engines), industrial rolls, hydraulic shafts, boiler tubes, turbines and pumps to prevent corrosion and erosion problems. They are also used on cars, pens, watches and cosmetics for decorative purposes. Nanocoatings are used on money bills so as to prevent forgery. This chapter discusses in detail about the nanocoatings. Efforts have also been made to summarize the various processing techniques for their fabrication. Effect of nanocoatings on structural, mechanical and corrosion behaviour is also discussed. It is expected that the present chapter will be useful in designing and developing nanocoatings for wide industrial applications.

Synthesis, mechanical and corrosion behaviour of iron–silicon carbide metal matrix nanocomposites

The present paper reports the effect of sintering temperature on the properties of Fe–SiC metal matrix nanocomposites (5 wt% SiC; 95 wt% Fe) prepared by powder metallurgy technique. Samples were synthesized by ball milling followed by compaction and then sintering in the temperature interval of 900 – 1100℃ for 3 h, respectively. X-ray diffraction, microstructure, density, hardness, wear and corrosion of prepared samples have been investigated. X-ray diffraction studies show the presence of iron (Fe) and silicon carbide (SiC) along with the presence of iron silicate (Fe3Si) phase. Iron silicate is formed as a result of reactive sintering between iron and silicon carbide particles. Scanning electron microscopy of the samples shows the dispersion of SiC in the whole Fe matrix. Density, hardness, wear and corrosion characteristics of the samples were investigated which varies for different sintering temperature interval. It is expected that the results of this paper will be helpful in developing metal matrix nanocomposites for various industrial applications.

Structural and mechanical characterization of re-pressed and annealed iron-alumina metal matrix nanocomposites

In this study, structural and mechanical properties of re-pressed and annealed iron (Fe)-alumina (Al2O3) metal matrix nanocomposites (MMNCs) was investigated. Composite composition with 5 wt.% of alumina to iron was fabricated using ball milling technique. Cylindrical sintered specimens were pressed at a load of 10, 12.5, and 15 kN in a die of similar diameter so as to have maximum deformation internally at grain as well as at grain boundary. These specimens were heat treated at 900, 1000, and 1100℃ for 1 h to anneal the stresses as well as to enhance the bonding between grains. Synthesized specimens were characterized for their microstructure, density and hardness respectively. Scanning electron microscopic images of the synthesized specimens revealed the formation of dense phase microstructure along with the presence of nano-dispersion of iron aluminate (FeAl2O4) phase. Secondary processing of metal matrix nanocomposites resulted in an increase in density of prepared specimens from 4.6960 to 5.5035 g/cm3 and the hardness values increased from 63 to 94 HRH.

Wear Behavior of Composites and Nanocomposites: A New Approach

Tribology is a relatively new area and is defined as the science and technology of the interacting surfaces when they are in relative motion with respect to each other. Among various tribological processes wear is an important area of research. It is defined as the removal of material from either one surface or both the surface when they are in sliding, rolling or in impact contact respectively. There are several types of wear such as adhesive, abrasive, corrosive and fatigue respectively which takes place between the two interacting surfaces. Composite is a combination of two or more compounds thus leading to a development of new material which shows improved properties as compared to the base material. Nanocomposite has the size of each phase in the range of 1–1000 nm, frequently it lies between 1–100 nm. There are several types of nanocomposites such as Polymer Matrix Nanocomposites (PMNCs), Metal Matrix Nanocomposites (MMNCs) and Ceramic Matrix Nanocomposites (CMNCs) etc. Among all, MMNCs has gained much importance because it shows high values of mechanical parameters as compared to PMNCs and CMNCs respectively. MMNCs consist of metal as matrix and ceramic as reinforcement. A lot of researcher have studied the wear behavior of various metals, ceramics and polymers however no systematic attempt has been made to study the wear behavior of composite and nanocomposites especially MMNCs. The present chapter focuses on the wear, its mechanism, types of wear and analysis of wear debris. Apart from this a discussion is also done on the composites, nanocomposites, types of nanocomposites. Wear behavior of metals, ceramics and polymers is also described along with a special focus on iron-alumina metal matrix nanocomposites and a mechanism to reduce the overall wear rate in any system.

Tribo-evaluation of iron based metal matrix nanocomposites for heavy duty applications

The present paper reports dry sliding wear behavior of Iron based Metal Matrix Nanocomposites (MMNCs). Specimens were synthesized by ball milling followed by compaction and sintering in an argon atmosphere. Dry sliding wear behavior of undoped and doped Fe-Al2O3 metal matrix nanocomposite system was evaluated respectively. It was found that due to the reactive sintering between iron and alumina particles a nano iron aluminate phase (FeAl2O4) forms as a result of which the various structural and mechanical properties were found to improve. The results so obtained are critically analyzed and discussed to illustrate the interaction of various process parameters involved. It is expected that the results of the present work will be beneficial in developing quality MMNC products for heavy duty applications.

Effect of height to diameter (h/d) ratio on the deformation behaviour of Fe–Al2O3 metal matrix nanocomposites

The present paper reports the effect of height to diameter (h/d) ratio on the deformation behaviour of Fe–Al2O3 metal matrix nanocomposites (MMNCs) during bulk processing. Sintered compacts were machined to the required size with different h/d ratios. Test specimens were subjected to deformation at room temperature under three different interfacial friction conditions such as dry, solid and liquid lubrications. Deformed specimens show a significant improvement in the density and hardness. Results also revealed the formation of a nanosize iron aluminate phase due to reactive sintering, which in turn contributes to grain refinement. Experimental density of the specimens was also verified with the theoretical density using the standard equations. It is expected that the present work will be useful in designing and developing MMNC products with better quality at competitive cost.