NiTi Alloy Ball Bearings

For the very first time, NASA Glenn has successfully produced large quantities of high-grade ball bearings that are less than 0.25" in diameter thanks to the development of a new alloy made of 57.6% Ni, 39.2% Ti and 3.2% Hf. Smaller, shockproof balls improve load capability in conventional steel races, aircraft control surface joints, actuator gearboxes, and more. The production of standard NiTi alloy ball bearings that are smaller than 0.375" in diameter has proven challenging for multiple reasons, the primary being that small parts made from NiTi alloys cool excessively before they can be quenched (an important step in attaining high hardness). NiTi-Hf alloy, on the other hand, does not require such high-rate quenching to achieve high hardness. Consequently, the production of small, extremely durable NiTi ball bearings is now a reality. The powder metallurgy process by which these high-quality NiTi-Hf ball bearings are manufactured combines many new techniques with several existing ones. First, a high-purity NiTi-Hf powder is created through an atomization process and transformed into long, cylindrical rods through hot isostatic pressing. The rods are then cut into cylinders and machined into spheres somewhat larger than the desired finished ball size. Finally, the spheres are hardened through heat treatment and polished until the desired finished size diameter and surface finish (typically 1 micro-inch root mean square roughness) is achieved. The result is a non-corrosive, very hard, highly elastic yet remarkably strong ball bearing with unbridled potential. Innovators at NASA's Glenn Research Center have developed a new method for making small diameter, high-grade Nickel Titanium (NiTi) ball bearings that set a new standard for precision performance in the bearing field. Using non-corrosive NiTi alloy instead of steel is an inexpensive way to increase the load capability and reduce the weight of a ball bearing. It has been difficult, however, to produce balls less than 0.375" in diameter using the standard baseline 60NiTi alloy. To address this challenge, Glenn innovators have created a new, more advanced alloy consisting of NiTi and Hafnium (Hf) that can produce high-quality ball bearings of any size, but most notably less than 0.25" in diameter. Glenn's NiTi-Hf ball bearings are superior to any previously used alloy or steel. They are corrosion-resistant, shockproof, and have been rated at a grade 10 or higher on the Annular Bearing Engineering Committee (ABEC) scale (an industry-accepted tolerance standard for bearings). Thanks to their high strength and Rockwell hardness (HRC 58-60), these customizable ball bearings will facilitate new high-speed precision applications in a broad range of industries, including aerospace, automotive, industrial, medical, and more.