Preparing TiC coating on AISI D2 steel using mechanical milling technique

In the present study, ball milling was employed to coat titanium carbide (TiC) powder on AISI D2 steel specimens. During the milling, TiC powder adhered on the surface by a combination of mechanical deposition, wear, cold welding and fracturing processes. Structure of the coatings at various stages was studied by X-ray diffraction and scanning electron microscopy (SEM). Composition of the coatings was analyzed by energy dispersive X-ray spectroscopy. Their hardness was also measured. It was found that structural and morphological characteristics of the coatings were affected by milling time. With increasing the milling time from 5 to 20 h, average thickness of the coatings increased from 10 to 90 μm and, thereafter, it decreased, which indicated that, during the initial stages of milling, cold welding was prominent; but, on further milling, fracturing became the predominant phenomenon. It was also observed that substrate hardening enhanced hardness of the coatings. Scratch test was used to evaluate the coating adhesion in different conditions.