Surface modification of the Ti-Al alloys at 1000-1200 K

Alloys of Ti-40wt.%Al, Ti-43wt.%Al,Ti-48wt.%Al,Ti-47wt.%Al-2wt.%Nb-2wt.%Cr and Ti-47wt.%Al-2wt.%Nb-2wt.%Mn-0.8wt.%TiB2 were nitrided in ammonia at atm ospheric pressure and at 1000-1200 K for 3.6 x 10(5) s. The hardness and th ickness of the nitride layers on the alloys were measured. It was found tha t the hardness values increased with increasing nitridation temperature and aluminum concentration in the alloys. The depth of nitridation and the mas s gain of the nitrided specimens could be represented by an Arrhenius-type equation and the activation energies were calculated. The x-ray diffraction results were explained and are in agreement with the improvement of the ha rdness. Copyright (C) 2001 John Wiley & Sons, Ltd.