Traditional titanium nitridation techniques increase surface hardness by forming a thin layer of titanium nitrides (Ti2N and TiN) on the substrate surface. Such nitride-forming techniques successfully increase hardness and improve wear resistance, but can result in premature fatigue failure.
A novel method, known as kinetically-controlled titanium nitridation, is
capable of diffusing nitrogen into titanium without the formation of undesirable
nitrides by providing an extremely low nitrogen pressure. Controlled parameters have yielded nitrogen-stabilized α-Ti cases of (10-30) micrometers in thickness with as much as a three-fold improvement in surface hardness.
Nevertheless, diffusion-affecting features such as structural defects and crystallographic orientation play a significant role in non-uniform nitride nucleation – giving way to unwanted nitrides. Numerous experiments combined with surface analysis techniques such as XRD, XPS, SEM, XEDS, EELS, and TEM were utilized to more fully understand such causes of non-uniform nitridation, as well as methods to control them.