Affiliation: | a Institute of Materials Engineering, National Chung Hsing University, Taichung 402, Taiwan, Republic of China b Institute of Nuclear Science and Engineering Physics, National Tsing Hua University, Hsinchu 300, Taiwan, Republic of China |
Abstract: | Characterization of TiN coatings on type 304 stainless steel was carried out using a Zeiss EM 902A energy filtering transmission electron microscope equipped with an electron energy loss spectroscopy (EELS) detector. TiN thin films were produced by a hollow cathode discharge ion plating coater. It was found by plan-view transmission electron microscopy that the microstructure of the TiN coatings is thickness dependent. The grain 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 degree of texture, but the subsurface and internal TiN layers are mainly equiaxial and randomly oriented. Chemical analysis by EELS shows that the relative oxygen content increases linearly from the TiN surface to the TiN/steel interface, whereas the relative nitrogen content first decreases slowly 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 the early-deposited TiN is nonstoichiometric. By the periodic cracking method, the ultimate shear stress at the TiN/steel interface and the residual stress in the TiN thin film were estimated to be 2.2 GPa and 12.8 GPa, respectively. |