EFFECT OF NITROGENATION ON SURFACE HARDNESS AND WEAR RESISTANCE OF TITANIUM MONONICKELIDE.

Kinetics of nitrogenation in ammonia atmosphere, and the phase composition of NiTi, were studied. As the nitrogenation temperature increases the thickness of the underlying diffusion layer increases also, while the thickness of the nitride layer decreases, and the high hardness of the layer is defined mostly by the TiN formed. Nitrogenation increases the NiTi ultimate tensile strength by 15% and its yield point by 42%; at the same time the elongation decreases drastically (up to 3 times) as does the impact toughness (up to 3. 3 times). The wear-resistance tests, showed that nitriding results in an increase of wear resistance by ca. 9 times.