Mechanical

Mechanical surface treatments involve adding or removing a surface layer by physical means.  This may be dipping the system in plastic or it may be a polishing process.  Kellogg’s Research Labs is able to overlay most readily available plastics onto your nitinol parts and we have several proprietary coatings available.  On the material removal side, both polishing and roughening are available able to achieve surface finishes as smooth as 2Ra.  If heat exchange is a major problem, then roughening the surface will make it such that

Electro-Chemical

 

Electrochemistry is the study of adding or subtracting material from the surface of your parts, using the combination of electricity and acid (referred to as the electrolyte).  Electropolishing removes the rough, outer layer of the nitinol, leaving behind a mirror finish.  This can be used as a final process step or as a precursor to electroplating or growth applications.  Electroplating is the deposition of metal on the surface of the nitinol, usually involving a sacrificial electrode made of the metal being deposited.  Some common metals include: copper, which allows solder to adhere to the nitinol, nickel, which increases the weldability of nitinol, titanium, which improves corrosion resistance, gold, which increases radiopacity, and platinum, which increases corrosion resistance.  A third electrochemical process commonly used on medical nitinol is passivation.  This is a chemical method of building up a layer of oxidation by reacting the nitinol with an electrolyte.  This process is required for most devices seeking FDA (or similar organization) approval.

Laser

Gone are the days of lasers only being useful for grossly cutting material.  While we have lasers that are able to conduct high power processes like welding and cutting, much more sophisticated processes are also available.  Through the use of high frequency, pulsed wave lasers, the surface of the nitinol can be modified to obtain a wide range of beneficial characteristics.  When used in vacuum, the surface can be restructured, allowing for a sophisticated mix of properties at the surface.  When used in atmosphere, the surface can be carefully reacted with the atmosphere, creating a surface layer that controls the interaction with the environment.

Growth

 

Some surface layers aren’t so much deposited as they are grown.  An excellent example of this is graphene.  Graphene can dramatically improve the heat transfer characteristics of nitinol when properly grown on the surface of the nitinol.  Graphene and other surface coatings can be grown in either our vacuum or controlled atmosphere furnaces.  Ask us about growing materials onto the surface of your nitinol parts.