The Magical Material DeMystified
|High Hardness||Hardness from 56 to 62 RC can be achieved|
|Wear-Resistance||Low friction and high hardness result in long life|
|Non-Magnetic||A range of applications require a non-magnetic material|
|Non-Corrosive||Salt spray tests show no signs of corrosion|
|Better Lubrication||Oils without corrosion inhibitors may be used to improve boundary lubrication|
|Lower Friction||The coefficient of friction is substantially reduced|
|Reduced Weight||Parts weigh 15% to 20% less than steel|
|Higher Speeds||Lighter weight reduces centrifugal forces for greater speeds|
|Tighter Tolerances||Super-fine grain structure achieves closer tolerances|
|Greater Efficiency||Lower weight and friction mean reduced power consumption|
The remarkable material known as Nitinol 60 (60% Ni; 40% Ti) was developed by Dr. William Buehler, a Naval Ordnance Laboratory Researcher working on non-corrosive, non-magnetic alloys. During research on these materials, one of the research team members accidentally discovered the memory capability of Nitinol 55 (55% Ni; 45% Ti), a sister alloy. Thereafter, the team devoted efforts toward Nitinol 55 development. Nitinol 60 was effectively abandoned in the late 1950’s, when difficulties in machining and work-hardening were encountered.
A more mysterious history for Nitinol maintains that the material was “discovered” right after a purported UFO crash in Roswell, NM. Development was then initiated by Battelle Memorial Institute in Ohio, whose work was contracted by Wright Patterson AFB- the very base where the alleged crash material was taken. The Abbott Ball Company doesn’t hold to this more exotic theory of Nitinol’s origins, but, the material is certainly extraordinary.
In the more than 50 years since its discovery, there has been very little success in commercializing Nitinol 60. Abbott Ball, with guidance from NASA, has engineered a new, breakthrough material for bearings, gears and other hardware that is hard, wear resistant, non-magnetic, inherently corrosion proof and weighs less than most competing alloys. Abbott took NASA’s microstructure findings and the Nitinol alloy charts to find a way to refine the grain for machining. Most machining occurs before annealing. After proper hardening, parts can be final-machined to extremely tight tolerances and polished to exhibit a mirror-like finish. Such a soughtafter material could revolutionize many aspects of engineering and manufacturing, with products and machines for aerospace, energy production, and medical devices.
The Miracle Material
Corrosion and premature wear of bearings, gears and mechanical components account for a major portion of machine replacements encountered in surface, marine and air transportation systems. Prior to Nitinol 60, there was no known material with the ability to withstand corrosive elements that was sufficiently hard for bearing or gear tooth surfaces. Carbide has both wear and corrosion resistance, but is brittle, difficult to work, and costly to machine. 440C Stainless is widely used for corrosion-resistant gears and bearings, but will rust if not protected from the environment. 52100 steel and M50 have excellent tribological characteristics, but have almost no resistance to corrosion. Titanium and commercially available titanium alloys are not compatible with lubricating oils and do not have the required wear resistance. Performance of gears, ball bearings, and other rotating transmission parts made* from Nitinol 60 offer the following advantages over parts made from 440C, 52100, and M50.
Nitinol 60 Specifications
Tribometer plates for NASA’s test machine
Salt Spray Test per ASTM B117, Hours in Salt Spray until Failure.
|Material||Hours of Exposure|
|440 C SS||4 hours|
|Type 316 SS||400 hours|
|Nitinol 60||No signs of corrosion after 4000 hours|
|Nominal Comparative Properties for Conventional Bearing Alloys, 55NiTi and 60 NiTi|
(Representative thermophysical and mechanical properties of bearing materials)
|Hardness||56 to 62 RC||35 to 40 RC||58 to 62 RC||1300 to 1500 Hv||60 to 65 RC|
|Thermal conductivity W/m-° K||18||9||24||33||36|
|Tensile/flexural strength, MPa||*TBD||-900||1900||600 to 1200|
|Youngs modulus, GPa||~114||~100||200||310||210|
|Fracture toughness||TBD||TBD||22 MPa/√m||5 to 7 MPa/√m||20 to 23 MPa/√m|
|Maximum use temperature, ºC||~400||~400||~400||~1100||~400|
|Electrical resistivity||~80X10 6 Ω-cm||~80X10 6 Ω-cm||~36X10 6 Ω-cm||Insulator||~60X10 6 Ω-cm|
|*TBD means to be determined|
Let’s Work Magic Together
Now that Abbott has discovered how to work with Nitinol 60, we’re eager to work with you: Let us help develop your applications for the 21st century. Our materials and manufacturing engineers welcome the opportunity to discuss the unique parameters of your material design requirements.