Iron Based Metal Matrix Composites Research Articles

Recent Developments on Wear and Corrosion Behavior of Iron/Iron–Nickel Metal Matrix Composites Reinforced with Zirconia

This article reports a brief review on the effect of process parameters on mechanical and corrosion properties of Fe-/Fe–Ni-based composites. Particle-reinforced metal matrix composites (MMCs) have gained a special interest in the field of structural, mechanical, aeronautical, and aviation industries. Iron-based MMCs are the one which are in high demand for tribological applications due to the high strength and high abrasion resistance properties. Different techniques have been used by different researchers for enhancing different properties of these composites during the last several years. Optimization of processing parameters, e.g., milling time, milling speed, reinforcement content, sintering time, and temperature are important for the development of composites by powder metallurgy route. Alloying of Ni in Fe–ZrO2 MMCs is found to play an important role in matrix phase formation during sintering. During sintering, the formation of γ phase in the matrix retards reactive sintering between metal and ceramic particles. Effect of some of the processing parameters on phase formation and various properties such as density, hardness, dry sliding wear properties, and corrosion reported in our previous studies have been summarized for particulate reinforced Fe/Fe–Ni metal matrix composites.

Wear Analysis of Charcoal, Unpurified Carbon Nanotubes and Purified Carbon Nanotubes based Metal Matrix Composite

The different materials used to improve the mechanical strengths such as carbon fibers, CNTs, and other alloy’s. The present study focus on the iron based metal matrix composites with charcoal, unpurified and purified CNTs as a reinforcement with the varying percentage of each constituent from 1 to 5 weight %. The wear testing is carried out for five different pin loading varying from 1 to 5 kg. It is observed that as a percentage of the CNTs increase, the material shows more wear resistance characteristics. Experimental results confirmed that CNT based MMC is much tougher than the charcoal based MMC.

CVD Coating of Oxide Particles for the Production of Novel Particle-Reinforced Iron-Based Metal Matrix Composites

This paper focuses on surface metallization of oxide particles by means of titanium nitride (TiN) thin films for the production of highly wear-resistant metal matrix composites (MMC) on Fe-base for wear protection applications. These powder-metallurgically produced materials consist of a metallic matrix with embedded oxide hard-particles such as alumina or zirconia. The poor wettability of these oxides by iron-base melts and the resulting weak bonding between the components lead to porous materials and weak tribomechanical properties, thus limiting the material’s application range. To counteract such problems, this paper describes a processing route in which the oxide particles are pre-metallized by application of a thin TiN coating by means of chemical vapor deposition (CVD). This surface metallization should increase the wettability and bonding behavior between the ionically bonded particles and the iron-base alloy, which should improve the mechanical and tribological properties. Therefore, a CVD device for coating ceramic particles was constructed and is described in this paper. Furthermore, coatings deposited on the ceramic sub-strates were investigated by means of RBS, SEM and XRD. In addition, the feasibility of producing metal matrix composites (MMC) by admixing the TiN-coated oxide particles with a Fe-base alloy and their further densification by supersolidus liquid-phase sintering is demonstrated.

Microstructural evolution of iron based metal–matrix composites submitted to simple shear

New Fe-based metal matrix composites reinforced by around 11vol%. TiB2 ceramic particles have been characterized before and after planar simple shear tests up to 50% plastic shear strain. The morphology and the crystallographic texture of the particles have been studied by SEM-EBSD. Hardening behavior and damage development were compared for fine or coarse matrix grain size. Good ductility of the composite was observed at the macroscopic scale in both cases. Local damage by particle fracture was evidenced and quantified thanks to image processing. Effect of matrix strengthening and of particle size on damage was discussed.

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.

Physico-Mechanical Properties of Sintered Iron-Silica Sand Nanoparticle Composites: A Preliminary Study

The present study aims to develop silica sand nanoparticles using the ball-milling process and to utilize these nanoparticles as reinforcement for iron-based metal matrix composites. Iron-based metal-matrix composites with 5, 10, 15 and 20wt.% of the processed silica sand nanoparticles were developed using powder metallurgy technique and sintered at 900°C, 1000°C and 1100°C. The results showed that the addition of silica sand nanoparticles to iron as reinforcement decreased the green density, albeit with an improvement in sintered densities. It was also observed that the increase in the sintering temperature results in an improvement of microstructure and microhardness of the composites. The maximum hardness of 168HV in iron-based composites was found with the addition of 20wt.% of silica sand nanoparticles at a 1100°C sintering temperature. It is proposed that the mechanism for the occurrence of this observed increment in microhardness is due to diffusion of silica sand nanoparticles into porous sites of the composites, resulting in the formation of FeSi phase.

Development of Aluminium Based Hybrid Metal Matrix Composites for Heavy Duty Applications

The present study deals with the investigation of dry sliding wear behavior of aluminium alloy based composites, reinforced with silicon carbide particles and solid lubricants such as graphite/antimony tri sulphide (Sb2S3). The first one of the composites (binary) consists of Al. with 20% Silicon Carbide particles (SiCp) only. The other composite has SiCp and solid lubricants: Graphite + Sb2S3 (hybrid composite) at solid state. Both composites are fabricated through P/M route using “Hot powder perform forging technology”. The density and hardness are measured by usual methods. The pin-on-disc dry wear tests to measure the tribological properties are conducted for one hour at different parameters namely load: 30, 50 and 80N and speed: 5, 7 and 9m/s. The tested samples are examined using scanning electron microscope (SEM) for the characterization of microstructure and tribolayer on worn surface of composites. The results reveal that wear rate of hybrid composite is lower than that of binary composite. The wear rate decreased with the increasing load and increased with increasing speed. The results of the proposed composites are compared with iron based metal matrix composites (FM01N, FM02) at corresponding values of test parameters. These iron based metal matrix composites are also fabricated by P/M route using ‘Hot powder perform forging technology’. The comparative study reveals that the proposed composites have lower friction coefficient, less temperature rise and low noise level; however they have little higher wear rate. It is concluded that the hybrid composite has acceptable level of tribological characteristics with blacky and smooth worn surface.

Wear behaviour of Fe/M7C3 metal matrix composites with various microstructures during dry sliding

The wear mechanisms of iron based metal matrix composites and the wear behaviours of various microstructures were systematically studied by dry sliding wear testing and SEM examination. The experimental results show that three dominant wear mechanisms appeared in succession with increasing normal load during dry sliding. The transition of the wear mechanisms depended mainly upon the conditions of testing, and additionally it was seen that changes in microstructure of the steel had no marked effect on the transition. In the case of mild wear, no obvious differences in wear volume were found for the various microstructures. However, considerable differences in the wear volumes were observed under conditions of severe wear characterised by adhesion and delamination. The experimental results also indicate that the differences in wear resistance of the various microstructures were caused by differences in microstructural thermal stability, resistance to plastic deformation, resistance to nucleation and propagation of microcracks and especially by differences in energy consumption in these layers during wear.

Self-propagating high-temperature synthesis and liquid-phase sintering of TiC/Fe composites

The present paper addresses a possible route for the manufacturing of iron-based metal–matrix composites (MMCs) with a high level of reinforcement. The ceramic reinforcement studied was titanium carbide (TiC). TiC is one of the hardest materials to be found, which is why a TiC/Fe composite has the potential to be used as armour. Two manufacturing routes have been evaluated experimentally, i.e., liquid-phase sintering (LPS) and self-propagating high-temperature synthesis (SHS). LPS was found to be more effective due to easier process control and due to the process yielding a more homogeneous material. Both LPS and SHS produced a material with a relatively high degree of porosity. The porosity in the LPS experiments could be decreased by varying the process parameters, but this was not possible in the SHS process. Metallographic investigation shows that the TiC/Fe system is feasible and that applications utilising TiC/Fe composites are possible in the future. This is due to the fact that despite the porosity, an improvement of the MMC properties is detected, compared to those of the matrix material.

Abrasive wear of FeCr (M7C3–M23C6) reinforced iron based metal matrix composites

The effects of volume fraction, particle size, and sintered porosity of FeCr (M7C3–M23C6) particulates on the abrasive wear resistance of powder metallurgy (PM) Fe alloy metal matrix composites have been studied under different abrasive conditions. It was seen that the abrasive wear rate of the composites increased with an increase in the FeCr volume fraction in tests performed with 80 grade SiC abrasive paper, but it decreased for tests conducted with 220 grade SiC abrasive paper. Furthermore, the wear rates decreased with an increase in FeCr size for composites containing the same amount of FeCr. Hence it is deduced that Fe alloy composites reinforced with larger size FeCr particles are more effective against abrasive wear than those reinforced with smaller ones. At the same time the results show that the beneficial effects of hard FeCr particulates on wear resistance far outweighed the detrimental effects of sintered porosity in the PM metal matrix composites. In addition, the fabrication of composites containing soft particles such as graphite or copper favours a reduction in the coefficient of friction, and increases the matrix hardness of the composite. For this reason graphite and copper were used in the matrix in different amounts to test their effect on the wear resistance. Increase in graphite and copper volume fraction allowed the formation of additional phases, which had high hardness and wear resistance. It was also found that the wear rate of the composites decreased considerably with graphite and copper addition.

Characterisation of interfacial layer between nitrogen alloyed stainless steel and alumina in a metal matrix composite

Particulate-reinforced metal matrix composites are of interest as increasingly important engineering and structural materials. The majority of the materials have been developed using light alloy matrices for applications based on light weight and improved strength and stiffness over the contemporary light metal alloys. However, other material combinations and applications have also been considered. Iron-based metal matrix composites with alumina as reinforcement have been recently investigated for the use as inexpensive, abrasion resistant materials. One of the crucial microstructural features which affects mechanical performance of composite materials is the interface between a reinforcement and matrix. In this paper the interface between alumina and nitrogen alloyed stainless steel has been investigated.

Observations on the Role of Interfacial Phenomena in Materials Processing.

Examples of the role interfacial phenomena can play in materials processing are highlighted in the description of a number of recent research studies conducted at Imperial College. Interfacial phenomena play critical roles in increasing or retarding the rates of chemical reaction and in promoting or hindering wetting and dispersion of phases in each other.The reduction of ilmentite to iron and titanium carbide or titanium oxycarbide has been studied with the ultimate aim of achieving separation of the titanium and its subsequent conversion to pigment grade titanium dioxide. The need to achieve good separation of iron from other reaction products is then a prime concern. The effects of reducing conditions on the wetting of titanium carbides and oxycarbides by iron alloys has therefore been studied. It seems that associative adsorption of titanium and carbon may be responsible for the observed effects of dissolved titanium and carbon on the wetting of TiC by liquid iron alloys.As a result of this work a further project has been generated involving the identification of conditions for achieving good dispersions of refractory carbides including titanium carbide in iron alloys. The major motivation behind this work was the desire to develop a cheap casting based process for the production of iron based metal matrix composites capable of producing near net shape products. As a result of this work a novel rapid testing technique for the assessment of the wettability and compatibility of potential filler materials with liquid metal matrices has been developed. The technique employs levitation and quenching of liquid metal drops containing added filler materials to permit assessment of alloy composition, filler coatings and temperature on matrix/filler interactions. The levitation technique has been further utilised in a study of the conditions required for dispersion or non dispersion of second phase particles in liquid superalloys. In this case the cleanliness of the superalloys achieved during recycling procedures is determined by the ease with wich inclusions can be removed. Some observations with ternary oxides also indicate the importance of the associative adsorption phenomenon.The importance of interfacial considerations has also been highlighted by our studies on the production of aluminium-titanium-boron grain refining master alloys from fluoride fluxes. Entrapment of the products can result from emulsification occurring during the reduction reactions. A detailed study of this phenomenon has been conducted using a modified sessile drop technique. The results obtained indicate the critical role that interfacial tension plays in determining the ease of metal-flux separations and in determining whether products are dispersed in the metal or slag.The kinetics of metal-salt reactions were also found to be of importance. Fast transfer of Ti and B to the metal results in the build up to TiAl3. TiB2 or AlB12 at the interface. These compounds when present at the interface can be wet by the flux and result in emulsion formation. Inhibition of emulsification can be achieved by the presence of surface active elements such as magnesium and calcium.The role of interfacial phenomena in influencing the kinetics of the reduction of slags has been studied in an investigation of the kinetics of alkali metal oxide release from silicate melts. The kinetics of K2O and Na2O release during heating in graphite crucibles has been studied from binary alkali oxide-silicon dioxide melts and from a wide range of CaO-Al2O3-SiO2 slags. The contribution of the wetting of the graphite by the slag towards influencing reaction kinetics represents a notable feature of the study.