The alloys of Ti-40wt%Al, Ti-43wt%Al and Ti-48wt%Al were nitrided at the temperature of 1000-1300 K for 1000 hours. Hardness and thickness values were determined. It was found that the values increased with the increasing of the nitridation temperature and with the wt% Al in the alloys. Thickness values of the scale nitrided at 1300 K of the three alloys were in the order of 10-20 microns/side. With 1300 K nitridation, Knoop hardness of the nitride-Ti-48wt%Al composites was as high as 285% of the non-nitrided alloy and its mass increase was 0.7318 mg.cm^-2. These showed the consistency between the experimental results of the hardness and thickness values of the alloys.