Nickel-Titanium Alloys for Oil-Lubricated Bearing and Mechanical Component Applications

Abstract

Nickel-titanium (Ni-Ti) alloys are normally associated with applications that exploit their shape memory characteristics. When properly formulated and processed, however, Ni-Ti is dimensionally stable and offers a unique blend of attributes suitable for tribological applications. This paper demonstrates that Ni-Ti alloys are promising candidate structural materials for oil-lubricated rolling and sliding contact applications such as bearings and gears. Ni-Ti alloys offer a broad combination of physical properties that make it unique among bearing materials. Ni-Ti alloys are hard, electrically conductive, highly corrosion resistant, readily machined prior to final heat treatment, non-galling and non-magnetic. No other bearing alloy, metallic or ceramic encompasses all of these attributes. Spiral orbit tribometer (SOT) tests were conducted using 60NiTi balls loaded between rotating 440C disks, lubricated with synthetic oil and tested in a vacuum. Excellent tribological performance (life and friction) was observed and lubricant degradation normally associated with titanium alloys was absent. It is anticipated that the Ni-Ti family of alloys may form the basis of an entirely new class of bearing and component materials.