MECHANICAL PROPERTIES OF NbN/Si3N4 MULTILAYER COATINGS DEPOSITED BY REACTIVE SPUTTERING

초록

NbN/Si3N4 multilayer coatings were deposited onto a high speed tool steel substrate by reactive sputtering and their mechanical properties were evaluated in terms of the dependence of hardness and adhesion strength on the sputter deposition process parameters. The hardnesses NbN/Si3N4 multilayer coatings increase up to the flux ratio of 0.4 but nearly do not change after that as the N2/Ar flux ratio in nitride sputter deposition increases. The hardnesses of NbN/Si3N4 multilayer coatings nearly do not change with annealing at low temperatures but decrease owing to oxidation with annealing at a high temperature like 800℃ after depositing the layers by sputtering. Postannealing at low temperatures increases the adhesion strength of the multilayers, but high temperature annealing is not desirable since it decreases the adhesion strength besides the hardness deterioration.