Comparisons of grain size-density trajectory during microwave and conventional sintering of titanium nitride

• Fine TiN powder has been sintered using microwave and conventional sintering methods.
• The “relative density/grain size” trajectories have been analyzed for both methods.
• An area for further grain refinement by two-step sintering technique is proposed.
• Microwave sintering resulted in finer grains (170 nm) and higher hardness (20 GPa).

A broad range of sintering temperatures and hold times had been systematically varied to investigate the “relative density/grain size” trajectories for titanium nitride specimens during microwave and conventional sintering. Fully dense materials with a submicron grain size (around 170 nm using microwave sintering and around 240 nm using conventional sintering) are achievable using the simple “ramp & hold” approach. Improvement of the mechanical properties, including increase in hardness (from 18 to 20 GPa), fracture toughness (from 2.9 to 3.4 MPa m1/2), was observed due to grain refinement in case of microwave sintering. The area for the future optimization for the sintering schedule for further grain refinement has been proposed.