titanium springs

["Hardwick, Robert C" <Robert.Hardwick@PSS.boeing.com>]

It's important to remember that the preferred titanium alloy for springs
is not the same as for general structure.  The standard structural Ti is
Ti-6Al-4V, for springs use Ti-3Al-8V-6Cr-4Mo-4Zr.  Rolls right off the
tongue...

Anyhow, it really is great stuff: high stress (180-210 ksi heat treat),
superelasticity allows small space, low weight and it's corrosion
resistant, too.  It does share the notchsensitivity of Ti alloys.  So it
must be shot peened.  It's, like the other Ti alloys, also not resistant
to wear.  So the installation should avoid guides or other parts which
could rub.  For coil-over applications, a sacrificial plastic sleeve
over the shock should suffice.

I'm not sure about cost.  For aircraft, the attributes list above are so
overwhelming, and the alternative stainless steels not cheap either,
that we just use it where we can.

cheers, robert hardwick, seattle usa