The Interface Between TiN Coatings and AISI 304 Steel Substrates for Different Deposition Conditions: A Transmission Electron Microscopy Study

The interface between PVD TiN layers and austenitic stainless steel AISI 304 substrates has been studied by means of plan-view and cross-sectional transmission electron microscopy (XTEM). Three types of coating systems classified as follows were studied: Type 1 is the coating system AISI 304 - Ti - TiN, type 2 the coating system AISI 304 - TiN (new way of deposition, with the substrate masked from the plasma during the initial stage of deposition) and, finally type 3 is the system AISI 304 - TiN (conventional way of deposition). The results show that in the tirth system epitaxial growth between TiN and substrate grains occurs; however it does not yield the best adhesion properties. The bad adhesion can be explained by interface defects induced by highly stressed iron nitrides in the top layer of the substrate. The type 2 specimens exhibit better adhesion properties, altough no epitaxial growth is observed, but on the other hand only few interface defects are present.