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Purpose of
Test:
Badger Metal in conjunction with
Balzers wanted to ascertain the viability of applying a coating to a
TherMaLLifeÒ treated surface. Many tools in existence today have been
previously MetaLL ifeÒ and/or TherMaLLifeÒ processed (ferritic
nitro carburized). Both of these processes
provide superior die failure and soldering protection even without subsequent
application of a coating.
The importance of
a coating's substrate preparation is now being investigated by NADCA's Die Materials
Committee Coating Taskforce. Since coatings are thin, by nature, it is important
to have a properly prepared substrate to support the coating. Some
customers have asked if it is possible to directly apply a PVD coating over our
processes if so desired. PVD (physical vapor deposition) coatings are
applied at a lower temperature than CVD (chemical vapor deposition) coatings.
With one exception, our tests confirmed adhesion is good to excellent in all
cases.
Substrate
Preparation:
Four rectangular pieces of
Viscount 44 (prehardened H-13) were first processed
with MetaLL ifeÒ using four different processes (T-10, T-21, T-41, T-61). The
lower the number the smoother the resulting surface finish. Subsequent to
this our TherMaLLifeÒ (ferritic
nitro carburizing) process was applied using
our standard H-13 recipe. The T-10 finish is an extremely smooth surface but rougher than a TherMaLLifeÒ
surface which has no changed topography.
Applied Coatings:
The four coatings applied, using
Balzers as the source, were common commercially
available types which included the ones shown below. Three
HRC (hardness reading) indentations were used
to check the adhesion of the coating to each specific area on each coupon.
There were a total of 12 measurements on each coupon. Since coatings are
extremely thin, the hardness readings penetrated the coating and in most cases,
reflected the Viscount 44 plus some of the diffused surface hardness. A micro photo was taken of one indentation
in each section exhibiting the most variation. In addition,
coating
thickness measurements were performed using X-Ray diffraction.
Click here or on the corresponding coupons below
to see micro photos.
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