IN THIS ISSUE
Compatiblity:
Coatings
1.
PVDs Tested
3. Adhesion
4.
Hardness
5.
Thickness
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The Holiday
Season
will soon be upon us. Many plants will be shutdown for extended periods
during this time. This provides the perfect time to get your tooling to us for proactive
maintenance. We will remain open for this purpose.
Question:
What special methods for processing should be considered when processing Dievar material?
Our December
issue will address this question.
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We estimate there are between 100,000 and 150,000
existing die casting dies in the field that have been processed with either
MetaLLife and/or
ThermaLLife over the past 20 years. Some customers are
now asking "If I decide to additionally apply a coating to one of these
previously treated surfaces, will the coating be compatible?" In many
instances the current owner or possessor of the die does not know what has
previously been done to a tool that is inherited.
Since this could cause a huge problem, we decided
to do some evaluation to see how well a subsequent coating would adhere to one
of our previously treated surfaces.
We configured some coupon samples of
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pre-hardened Viscount 44 hot work die
material. These were subsequently processed with four different versions
of MetaLLife. On top of each of these MetaLLife treated coupons we
diffused our
ThermaLLife FNC process making sure
that an adequate compound layer was formed during the treatment.
HRc indentations were made in three locations to
each of the specimens. A total of 12 points were marked on each
coupon. Evaluation by photography and X-ray diffraction was done to
determine adhesion characteristics of the applied coatings. Hardness
readings were also taken at each location and charted along with each coating's
thickness.
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Titanium Aluminum Nitride
TiAlN |
Chromium Nitride
CrN |
Titanium Nitride
TiN |
Chromium Carbide
CrC |
| The sample coupons
measure 4" x 1" x .50" |
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With the exception of the CrC, all coatings applied had good
to excellent adhesion and uniform coating thickness. HRc hardness readings
indicate that the 12ea indentations on each coupon penetrated the coating as
well at going partially into the diffusion layer.
The TiAlN coating and CrN coating showed good adhesion with only minor anomolies.
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TiN coating, because of its low oxidation temperature and limited
expansion capability, does not permit this coating to be used on die casting die
inserts or high temperature applications.
CrC not only had poor adhesion characteristics, but also varying thickness from
1.4 to 8.8 microns. |
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Conclusions: Based on our tests using commercially
available treatments from Balzers, all but CrC coating proved a viable
coating to apply over a previously applied
ThermaLLife and/or MetaLLife
surface.
The coating thickness of the TiAlN, CrN,
and TiN were uniform with little to no inclusions or anomolies. The
CrC coating, |
however, since adhesion appeared to be poor with varying
thickness, is not a good choice for a coating to be appled over any of
our processes. In our next issue we will discuss
and examine the properties of the new popular Dievar material and how these
properties relate to proper application of our
ThermaLLife process. |
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