Graded TiN Coating by Supersonic Free-Jet PVD Combined with Reactive Plasma

Abstract

Ceramic coating is a very popular technology for improving the properties of structural materials. A titanium nitride (TiN) coating is a typical example and has been widely applied to cutting tools, electronic devices and many other fields utilizing its superior physical properties. This paper sought to produce a graded TiN coating on a Ti substrate by combining Supersonic Free-Jet PVD (SFJ-PVD) with a reactive plasma-metal reaction technique. The authors have developed SFJ-PVD as a new coating method in which a coating film is formed by depositing nanoparticles with very high velocity onto a substrate. SFJ-PVD can provide a high deposition rate and thick film coating. Gradually changing the nitrogen flow rate during deposition produces a graded TiN coating, in which composition changes gradually from pure Ti to TiN . A monolithic TiN coating is also produced with SFJ-PVD . XRD analysis of the graded TiN detected peaks for Ti, Ti2N and TiN, while only a TiN peak is observed in the monolithic TiN coating. EPMA analysis of a graded coating reveals a gradual compositional change from pure Ti to TiN . Few pores or cracks are observed in a graded TiN or in a monolithic TiN formed under the optimized conditions of SFJ-PVD.