y -TiAl alloys have been treated in ammonia gas for 100 hours at temperatures between 1000 K and 1200 K to from TiN surface layers The nitrided layers have been characterized by X-ray diffraction and microhardness measurements and by tribological testing using a pin-on-disk apparatus and a WC pin. The coefficient of friction is reduced substantially by the nitridation treatment, and wear rate of the alloy is reduced by two or three oders of magnitude after nitridation in comparison to the untreated material. The effects increase with increasing treatment temperature over the temperature range studied.