Abstract
In this study, the effects of heat affected zone generated by wire electro discharge machining (w-EDM) process on the surface integrity of a K15 grade hard metal before and after TiN coating application via chemical vapour deposition (CVD) was investigated. It was observed that applying dry blasting (DB) on w-EDM'ed surfaces is a very efficient way to remove heat affected zone, namely recast layer. TiN layers deposited on w-EDM'ed surfaces showed a great diversity in their morphologies depending on the w-EDM process parameters and exhibited irregularities whereas the ones coated on dry blasted (DB'ed) surfaces constituted much finer mixture of nodular, star shaped and lenticular crystals. Adhesion of TiN layers on the DB'ed hard metal samples was better compared to the ones deposited directly on w-EDM'ed samples with a thick heat affected zone on their surfaces. Friction and wear properties of the TiN layer formed on DB'ed surface against alumina ball were also superior which were also in good agreement with its higher adhesion strength and distinctive morphology.
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