Microstructure and coating properties of ion-plated TiN on type 304 stainless steel

The microstructure and chemistry of TiN coatings on type 304 stainless stee l were characterized by using a Zeiss EM 902A energy filtering transmission electron microscope equipped with an electron energy loss spectroscopy (EE LS) detector. Thin TiN films were produced by a hollow cathode discharge io n plating coater. It was found by plan-view transmission electron microscop y that the microstructure of the TiN coatings is thickness-dependent. The g rain size of TiN ranges from 88 nm at the coating surface down to 9 nm near the TiN-steel interface. In addition, the TiN surface layer shows some deg ree of texture, but the sub-surface and internal TiN layers are mainly equi axial and randomly oriented. Chemical analysis by EELS shows that the relat ive oxygen content increases approximately from the TiN surface to the TiN- steel interface, whereas the relative nitrogen content first decreases slow ly and then drops rapidly near the interface. The presence of a Ti2N phase and the deficiency of nitrogen near the TiN-steel interface suggest that th e early-deposited TiN is non-stoichiometric. By the periodic cracking metho d, the ultimate shear stress at the TiN/steel interface and the residual st ress in the TiN thin film were estimated to be 2.2 and 12.8 GPa, respective ly. (C) 1998 Elsevier Science S.A. All rights reserved.