Papers by Author: M.M. Mahat

Abstract: Alumina (Al₂O₃) cutting tools have been coated with carbon coating using physical vapor deposition (PVD) to improve its wear resistance. The cutting tools were subjected to surface pretreatments namely blasting and acid etching to improve the coating adhesion onto the substrates. The effects of pretreatments on the cutting tools topography prior to deposition were investigated using atomic force microscopy (AFM) while the surface morphology was investigated using scanning electron microscopy (SEM). The adhesion strength of the carbon coating was investigated using microscratch. This study shows that although the coating were deposited evenly on the surface, the cutting tool that was blasted prior to deposition has better adhesion strength when compared to acid etching and no-pretreatment.

Abstract: Hydrofluoric Acid (HF) and sand blasting have been incorporated together with chemical surface pretreatment (HF) for the surface pretreatment of the Al₂O₃ cutting tool. Amorphous graphite was deposited on the substrates by using PVD technique. Morphological observation by Scanning Electron Microscope (SEM), surface roughness and topography of the substrate by using Atomic Force Microscopy (AFM) was done in order to investigate the effect of surface pretreatment on the substrates. Critical load required in scratching the substrate’s surface after coating by different surface pretreatment was evaluated by microscratch testing. As-received micrograph has a continuous 45° direction based on horizontal line when the substrate was put in the chamber at the time the image was taken. Substrate with surface pretreatment shows non-uniform surface with peak and valley image. Coated surface micrograph shows amorphous graphite with cube in shape. Surface roughness and critical load for microscratch of sample was found increased with surface pretreatment both chemically and mechanically.