To examine the effect of ion implantation into substrates prior to ceramic coating, Ti ions were implanted into the substrates of pure iron, SUS304 and 0.1%C steel, and TiC films were deposited on these pretreated substrates by an activated reaction evaporation method. It was found that in pure Fe and SUS304 an amorphous surface layer was created after a critical dose of 5×1016 Ti ions/cm2. TEM observations and indentation-fracture tests revealed that the frequency of microcracking or exfoliation of TiC films was significantly reduced by Ti ion implantation of the substrates. For 0.1%C steel, however, the Ti ion implanted surface layer still remained crystalline and exhibited no improved adhesion to TiC films. The AES analysis showed that carbon atoms diffused readily into the amorphous surface layers, resulting in the creation of a ductile transition layer of Ti-rich TiC phase at the TiC-substrate interface. Thus, the adhesion improvement of TiC films is thought to result from the amorphous transformation of substrate surfaces and the specific structure relaxation in the amorphous layer may be effective in relieving complex strains, themally or mechanically induced at the TiC/substrate interface.
