PROCESS OPTIMIZATION DURING ELECTRIC DISCHARGE MACHINING OF NICKEL-CHROME ALLOYPages 61-70
Abstract
The introduction of alloying elements into steel significantly improves their properties. In this study, an attempt has been made to use alloying elements as reinforcements in Aluminium Metal Matrix Composites (AMMCs). For this purpose, aluminium (LM 25) matrix based MMCs have been developed using stir casting. The composition of the SiC (primary reinforcement) was maintained constant (10 wt. %) in all composite castings, whereas the compositions of the alloying elements (as secondary reinforcements) such as nickel (0, 5 and 10 wt. %), molybdenum (0, 2 and 4 wt. %) and chromium (0, 1.5 and 3 wt. %) were varied and composites were synthesized as per L9 orthogonal array. The microhardness, tensile strength, wear behaviour, scratch hardness and porosity levels of the newly developed composites were determined according to ASTM standards to explore the effect of the type and composition of the particulate reinforcements. A metallographic study was performed using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-Ray diffraction analysis (XRD) and Optical Microscopy (OM) analyses. Optimization of the composition of secondary reinforcements (viz. Ni, Mo and Cr elements) was performed with the help of Taguchi approach and Grey Relational Analysis (GRA) and a composite containing an optimum value of each property were identified. The results revealed that the composites containing a mixture of secondary reinforcements, several secondary phases were observed, which had a harmful effect on the composite properties. In addition, the reinforcements were scattered throughout the aluminium matrix. The results of GRA shows that a nickel composition of 5% together with 10% SiC, without using molybdenum and chromium is an optimum composition for secondary reinforcements to develop AMMCs.
Keywords: Aluminium Metal Matrix Composites,
Alloying elements,
Optimization,
Tribological and Mechanical properties,
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Jatinder Kumar, 
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