Definition
NDR^T® is an acronym: Nanograin Damage Resistant. NDR is
a process which comprises a thermal-mechanical treatment
designed to produce nanoscale microstructural refinement.
This refinement is evidenced by a significant increase in
the material's ability to resist damage during high cycle
mechanical loading, as encountered, for example, during
the service of a long-term cardioverter defibrillator lead
implant due to pulsating stresses.

Typical Alloys
The NDR process may be applied to non-precipitation
hardening, non-sensitizing, implant-grade alloys such as
those called out by ASTM F562 alloy (35N LT® wire or
MP35N® wire), ASTM F1058 (FWM 1058® wire) and
ASTM F138 (316LVM).

1 Typical results for 0.18 mm (.007") drawn wire. While these
results are typical, they represent data from a single laboratory
exercise and will not translate directly to each application.
2 Fatigue Strength: stress amplitude in a fully reversed rotary
beam fatigue test at 1x107 cycles calculated using published
moduli for each alloy.

Physical Properties
NDR processing does not change the chemical or atomic
makeup of the parent alloy system. Properties such as
density, electrical resistivity, thermal conductivity and
thermal coefficient of expansion are similar before and after
the application of NDR technology.

High Performance
The performance of NDR wire is attributable to the
underlying microstructure. Conventional microstructure is
show below (left), where the average breadth of each grain
is 2 microns. The next image (right) shows NDR-refined
microstructure where similar features are on the order of
200 nm.

Example Mechanical Properties
The tensile mechanical properties of NDR wire are
similar to conventional wire. Three examples of possible
properties for 35N LT alloy are given below.