Corrosion behavior and scratch performance of Al-WC nanocomposites

Abstract

Corrosion behavior and scratch performance of Al-WC nanocomposites with varying wt% of WC are evaluated in this study. Liquid metallurgy-based stir-casting route is used for fabrication of the nanocomposites. Particles are distributed in the matrix as confirmed by EDAX (energy-dispersive X-ray) spectrum and XRD ( X-ray diffraction) analysis. The micro-hardness of nanocomposites increases with the increase of wt% of WC particles. Corrosion behavior is studied under different corrosive environments, viz., neutral, alkaline and acidic solution. Tafel plots and Nyquist plots are obtained under the neutral medium (3.5wt% NaCl aqueous solution), while only Tafel plots are obtained under 0.5M NaOH solution and 0.5M HCl solution. Among all three operating mediums, NaCl solution is the least corrosive for the composite. Corrosion rates under NaOH and HCl medium are high and values are very close to each other. The least amount of reinforcement, 0.5wt% of WC, yields the best corrosion resistance under the neutral solution. The corrosion resistance increases with the amount of reinforcement under alkaline and acidic mediums. From SEM (scanning electron microscope) images of the corroded surfaces, pitting corrosion is observed for Al-0.5%WC composite while exfoliation with deeper cracks is observed for composites with a higher amount of WC. Scratch performance is also evaluated for a load range of 5N to 20N. Scratch resistance increases with increase in wt% of nano-particles. Surfaces after scratching are characterized using optical microscope, SEM, and EDAX spectrum.