Satpal Sharma

Production and some properties of Si3N4 reinforced aluminium alloy composites

Abstract The present research work focuses on the production of aluminium (AA6082-T6) matrix composites reinforced with various weight percentage of silicon nitride particles by conventional stir casting route. The percentage of reinforcement is varied from 0 wt.% to 12 wt.% in a stage of 3%. The microstructures and mechanical properties of the fabricated aluminium matrix composites are investigated. The scanning electron microstructure images reveal the presence of Si3N4 particles in the aluminium matrix. The distribution of Si3N4 particles has also been recognized with X-ray diffraction technique. The mechanical properties such as ultimate tensile strength and hardness have improved at the cost of reduction in ductility with increase in weight percentage of silicon nitride particulates in the aluminium metal matrix. The density and porosity of the composites also show an increasing trend with increase in volume fraction of Si3N4 particles in the aluminium matrix.

A study on microstructure of aluminium matrix composites

Abstract This work focuses on the effect of graphite particles addition on the microstructure of Al6082 metal matrix composites manufactured by conventional stir casting process. The reinforcement content was varied from 0% to 12% in a step of 3%. The microstructures of the manufactured composites were analyzed by scanning electron micrographic test. Elemental mapping of the Al6082 + 12% Gr reinforced composite was carried out to see the different elements present with their amount. Different elements present in the manufactured composites were verified by X-ray diffraction technique to justify the elemental map analysis. The result of this microstructural investigation revealed that a non-uniform distribution of graphite particles takes place at all weight percentages of graphite reinforcement.

Tribological and mechanical behavior of particulate aluminum matrix composites

Aluminum and its alloy are light in weight, ductile, strong and long lasting, having high corrosion resistance, good conductor of heat and electricity and are 100% recyclable. Despite all these good qualities, it has low wear resistance. But some applications entail high hardness and tensile strength, high modulus of elasticity than the conventional aluminum alloy with good tribological properties. Keeping in view the enhancement of mechanical as well as tribological properties with reduction in weight, the aluminum alloy is reinforced with a second phase which is hard and brittle, and the newly formed material has better mechanical and tribological properties. The paper reviews the various manufacturing processes of aluminum matrix composites, and it was found that the mechanical and tribological properties of the single reinforcement composites are better as compared to pure aluminum and its alloys irrespective of the aluminum matrix composites manufacturing process. Further, it was found that most of the hybrid composites exhibit better mechanical and tribological properties as compared to single reinforcement composites.

On the Use of Ball Milling for the Production of Ceramic Powders

In the present research work, the mixture of boron carbide and graphite ceramic powders with a theoretical composition of 50% each by weight were mechanically alloyed in a laboratory ball mill with different milling times of 12.5, 25, 50, 75, and 100 h. The investigation was carried out on the morphologies and densities of ball-milled powders. Morphology results revealed that ball milling is a very dominant and dynamic practice for preparation of two different powders into single entity powder having appropriate and consistent morphology. The results of density measurement showed that with milling times, density increased initially and then reduced with further increase in milling times. The density is reduced by 1.68% as the milling time increased from 0 to 100 h.

Effect of graphite reinforcement on physical and mechanical properties of aluminum metal matrix composites

ABSTRACT This work focuses on the effect of graphite particle addition on the properties of AA6082 metal matrix composites fabricated by conventional stir casting method. The percentage of reinforcement was varied from 0% to 12% in a step of 3%. The results revealed that with the addition of graphite particles, the micro- and macro-hardness decreased by 11.11% and 10.44%, respectively. The ultimate tensile strength also decreased by 5.88% with a reduction in percentage elongation from 8.7 to 6.8. The density decreased by 4.1% with an increase in porosity from 0.37% to 2.27% as the weight percentage of graphite particles increased from 0% to 12%.

Abrasive Wear Study of Rare Earth Modified Coatings by Statistical Method

This paper describes the effect of combined addition of rare earth elements namely CeO2 and La2O3 in Ni-base alloy coatings. The rare earth addition refines microstructure, increases hardness, and abrasive wear resistance of coatings. The abrasive wear behavior of these coatings was investigated using four factors load (L), abrasive size (A), sliding speed (S), and temperature (T) with three levels of each factor using RSM. ANOVA was carried out to determine the significant factors and interactions. Investigation showed that the load, abrasive size, and sliding speed were the main significant factors while load and abrasive size, load and sliding speed, abrasive size and sliding speed were the main significant interactions. Thus, an abrasive wear model was developed in terms of significant factors and their significant interactions. The validity of the model was evaluated by conducting experiments under different conditions. A comparison of modeled and experimental results showed 3-8% error.

Erosive Wear Study of Rare Earth-Modified HVOF-Sprayed Coatings Using Design of Experiment

In the present study, the effect of CeO2 addition in 1006 powder coatings on microstructure, microhardness, and high-temperature erosion resistance were studied. The CeO2 addition refines microstructure, forms new phases, and increases microhardness of HVOF-sprayed coatings. The erosive wear behavior of coatings were investigated by Response Surface Methodology (RSM). To investigate and develop an erosive wear model of unmodified 1006 (without CeO2) and modified 1006 (CeO2 addition) coatings’ four factors: velocity, impact angle, temperature, and feed rate, each factor at three levels were used. ANOVA was carried out to determine the significant factors and interactions. Thus, an erosive wear model was developed in terms of main factors and their significant interactions. A comparison of modeled and experimental results showed 4-7% error. The modified 1006 coating showed high erosive wear resistance as compared with unmodified 1006 coating. This is due to increase in hardness and refined microstructure of the modified 1006 coating.

A comparative study of waste eggshells, CaCO3, and SiC-reinforced AA2014 green metal matrix composites:

The influences of weight percentage of different reinforcement particles such as SiC particles, waste uncarbonized eggshell particles, carbonized eggshell particles, and CaCO3 powder were compared in the processing of aluminium-based metal matrix composite. The results revealed that by the addition of SiC particles up to 10 wt.% and waste eggshell particles up to 12.5 wt.% in AA2014 matrix alloy, the tensile strength, hardness, and fatigue strength increased. Toughness and ductility decreased by the addition of SiC and eggshell particles in AA2014 matrix alloy. Corrosion rate decreased by the addition of SiC particle up to 7.5 wt.% and eggshell particles up to 12.5 wt.%. Results showed that hardness and heat-treatable properties are improved after the addition of SiC reinforcement particles in AA2014 aluminium alloy as compared to eggshell particles. However, porosity and overall cost increased after addition of SiC particles in AA2014 alloy. Corrosion rate increased after the heat treatment for all reinforced metal matrix composite. These results showed that using the carbonized eggshell as reinforcement in the AA2014 alloy gave better physical properties at lower cost as compared to SiC particles. Proper wettability was observed between matrix and reinforcement material for both carbonized eggshell particles and SiC particles. No wettability was observed between AA2014 alloy and CaCO3 reinforcement particles. Poor wettability reduced the mechanical properties of AA2014/CaCO3 metal matrix composite.

RETRACTED: Mechanical and metallurgical characterizations of AA2014/eggshells/SiC hybrid green metal matrix composite produced at optimum reinforcement parameters:

AA2014/carbonized eggshells/SiC hybrid green metal matrix composites are fabricated by electromagnetic stir casting process at optimum parameters (squeeze pressure of 60 MPa, stirring current of 12 A, stirring time of 180 s and matrix pouring temperature of 700 C, respectively). In the range of reinforcement parameters, the result shows that the tensile strength of hybrid metal matrix composite increases with the increase in carbonized eggshell and SiC preheat temperature. Whereas the tensile strength of AA2014/carbonized eggshell/SiC hybrid green metal matrix composite decreases with the addition of SiC beyond 2.5 wt%. The tensile strength of AA2014/carbonized eggshell/SiC hybrid green metal matrix composite increases with the increase in the eggshell weight percent until it reaches the center value (7.5 wt%); the tensile strength then starts to decrease with the increase in eggshell weight percent beyond the center limit (7.5 wt%). The optimum values of weight percent of carbonized eggshell, preheat temperature of carbonized eggshell, preheat temperature of SiC and SiC weight percent were found to be 7.5%, 300 C, 500 C and 2.5%, respectively, to get the maximum tensile strength (predicted: 259.12 MPa). The results reveal that sample of AA2014/7.5% eggshell/ 2.5% SiC shows best result among all the selected samples. The microstructure presents that the reinforcements (7.5 wt% carbonized eggshell and 2.5 wt% SiC particles) are uniformly distributed in the matrix AA2014 alloy. Transmission electron microscopy image shows proper wettability between AA2014 alloy and reinforcements (7.5 wt% carbonized eggshell and 2.5 wt% SiC particles). Density, X-ray diffraction, cost estimation, hardness, toughness, ductility and fatigue strength were also calculated to see the effect of carbonized eggshell and SiC addition in matrix alloy AA2014.

Production and characterization of AA6082-(Si3N4 + Gr) stir cast hybrid composites

ABSTRACT The present research work emphasizes the development of hybrid aluminum (AA6082) matrix composites (HAMCs) reinforced with different weight percentages (wt.%) of ball-milled (silicon nitride (Si3N4) + graphite (Gr)) ceramic particulates by conventional stir casting process. Si3N4 and Gr are ball milled to obtain a definite density of combined powder. The weight percentage of ball-milled ceramic powder is varied from 0 to 12 wt.% in a stage of 3%. The microstructures as well as mechanical properties of the fabricated hybrid composites are analyzed. The scanning electron micrograph reveals the uniform distribution of ball-milled (Si3N4 + Gr) ceramic particulates in the aluminum matrix. The distribution of ball-milled (Si3N4 + Gr) ceramic particulates has also been analyzed with x-ray diffraction (XRD) technique. Both the hardness and ultimate tensile strength have enhanced with a reduction in percentage elongation with increase in weight percentage of ball-milled (Si3N4 + Gr) ceramic particulates in the aluminum matrix.