Nitinol 60

NiTiNOL 60, or 60 NiTiNOL, is a Nickel Titanium alloy (nominally Ni-40wt% Ti) discovered in the late 1950s by the U. S. Naval Ordnance Laboratory (hence the "NOL" portion of the name NiTiNOL). Depending upon the heat treat history, 60 NiTiNOL has the ability to exhibit either superelastic properties in the hardened state or shape memory characteristics in the softened state.

Producing the material in any meaningful quantities, however, proved quite difficult by conventional methods and the material was largely forgotten.

The composition and processing parameters have recently been revived by Summit Materials, LLC under the trademarked name SM-100. SM-100 maintains 60 NiTiNOL's combination of superb corrosion resistance [NASA terms it "Corrosion Proof"] and equally impressive wear and erosion properties.

In bearing lifing tests conducted by NASA, SM-100 has been shown to have over twice the life of 440C stainless steel and over ten times the life of conventional titanium alloys with a significantly lower coefficient of friction. The superelastic nature of the material gives it the ability to withstand compression loading of well over 350 ksi (2,400 MPa) with no permanent yielding.

Nickel titanium

Nickel titanium, also known as nitinol (part of shape memory alloy), is a metal alloy of nickel and titanium, where the two elements are present in roughly equal atomic percentages e.g. Nitinol 55, Nitinol 60.

Nitinol alloys exhibit two closely related and unique properties: shape memory effect (SME) and superelasticity (SE) (also called pseudoelasticity (PE)). Shape memory is the ability of nitinol to undergo deformation at one temperature, then recover its original, undeformed shape upon heating above its "transformation temperature". Superelasticity occurs at a narrow temperature range just above its transformation temperature; in this case, no heating is necessary to cause the undeformed shape to recover, and the material exhibits enormous elasticity, some 10-30 times that of ordinary metal.

History

The term nitinol is derived from its composition and its place of discovery: (Nickel Titanium-Naval Ordnance Laboratory). William J. Buehler along with Frederick Wang, discovered its properties during research at the Naval Ordnance Laboratory in 1959. William Buehler was attempting to make a better missile nose cone, which could resist fatigue, heat and the force of impact. Having found that a 1:1 alloy of nickel and titanium could do the job, in 1961 he presented a sample at a laboratory management meeting. The sample, folded up like an accordion, was passed around and flexed by the participants. One of them applied heat from his pipe lighter to the sample and, to everyone's surprise, the accordion-shaped strip stretched and took its previous shape.