EFFECTS OF IONITRIDING ON STRUCTURE OF NITRIDED LAYER AND SUBSTRATE TO Ti AND Ti-6A1-4V ALLOY

The structures of the nitrided layer and the substrate to commercially pure Ti and Ti-6Al-4V alloy after ionitrided at 750—920℃ have been examined by X-ray diffraction, metallography and EPMA. An α'-Ti (Al,N) solid solution phase rich in Al is found between the nitrided layer and the substrate of Ti-6Al-4V alloy as an obstruction of N_2 to diffuse through the substrate, and then the ionitriding behaviour of the alloy will be alterred. It was also observed that the texture of substrate of these two ionitrided metals varied considerably. Their preferred orientation in inverse-pole-figure of normal sheet changes from (0001) to (o110) and (2131), especially concentrated in the centre part of the specimen. This seems to be the particular phenomenon owing to the ionitriding technique.