The Nivarox alloy
As a trade name Nivarox is a German acronym for "Nicht Variable Oxydfest" or "Non-Variable Non-Oxidizing.". The Nivarox alloy is a metallic alloy used mainly in the watch industry, but also in other micro-machine industries and in certain medical equipment and surgical instruments. There are several variations of the Nivarox alloy depending upon the intended application. These alloys are stainless steel alloys with high concentrations of Cobalt (42-48%), Nickel (15-25%) and Chromium (16-22%). There are also small amounts of titanium and beryllium. Hairsprings made of this alloy are wear-resistant; they are practically non-magnetic, non-rusting and possess a low coefficient of thermal expansion.
When used for critical watch components the alloy reduces errors due to temperature variation. Along with the earlier alloy Elinvar, this alloy made obsolete the expensive compensation balance. Nivarox springs are now used by most watchmakers worldwide. The alloys also see limited use for specific components of sensitive scientific instruments.
Nivaflex NM, NO, NE, 45/5 and 45/18 are various alloys used for the mainsprings of watches. The NO, NM, NE, 45/5 and 45/18, are generally the same alloy (e.g. 45% Cobalt + 21% Nickel + 18% Chromium + 5% Iron + 4% Tungsten + 4% Molybdenum + 1% Titanium) except that the Nivaflex 45/5 has an additional 0.2% Beryllium.