Development of Advanced Nickel-Titanium-Hafnium alloys for Tribology Applications

High hardness, compressive and torsional elastic strength and corrosion resistance of binary Ni-Ti alloys makes it an optimum candidate for specialized bearings.  However, when compared with high performance steel bearings, intermetallic materials are more prone to rolling contact fatigue degradation.  Under rapid quenching processes, binary Ni-Ti alloy as been known to experience high residual stress.  Failure due to cracking and machining distortion is a possibility.  Not quenching leads to low hardness.  This dissertation is designed to elucidate the effect of hafnium ternary alloying on and bearing raceway performances.  Multimodal studies on Ni54Ti45Hf1 will include rolling contact fatigue testing as a basis for mechanical testing.  Electron microscopy and time/temperature/transformation study of Ni54Ti45Hf1 alloy will provide a better understanding for the ternary system.  Future work includes characterizing failure mechanisms, performances (hardness, strength, life) versus residual stresses, and map of alloy design space to allow optimization of the NiTiHf system for tribology applications.