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Questions/Topic
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Response
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How sensitive is the compound surface
layer to cleaning? |
Since the compound layer is the
surface offering solder protection, it is recommended that the
ThermaLLife
surface be cleaned so as not to disturb this thin layer. No more than a
20psi glass bead, or Scotch-Britẻ may carefully be used. If more aggressive
cleaning is required, we recommend using utrasonic methods using sodium
hydroxide (NaOH) which can remove solder without disturbing diffusion zones and
coatings.
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Can you weld over the process? |
You may have heard that welding over a nitrided surface is difficult. This is because of the sputtering from the diffused nitrogen in the steel. When heated, the nitrogen expands and "pops". Nitro-carburzing also
has some nitrogen in the surface so sometimes, it can sputter, but welding can be
done without significant problems.
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Can it be done to used tooling? |
Since there is no mechanical
component, once a tool has developed thermal heat checking,
ThermaLLife does not have the ability to close heat checks as does
MetaLLife.
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Is there a need to be concerned about distortion?
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ThermaLLife is performed at a safe temperature that is not only well below the austenitizing temperature of the steel but well below (at least 50 degrees F) the last temper temperature. Consequently, no distortion occurs during heating or quenching, which is also done in a
controlled atmosphere to maintain the size, shape, and tolerance of the original tool.
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What is the difference between the TL** processes?
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Many recipes are possible depending on the tool steel being treated. In addition to time, there are also temperature, velocity, pressures, and gases that enter into each recipe. Basically each of these
ThermaLLife "TL" processes can contain many other criteria besides the time that the tool is in the
controlled atmosphere. Beyond the time factor, we do not disclose the specifics of the
processes, however, each recipe is tailored for the application. Does Mrs. Fields tell you what goes into her cookies?
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What criteria do you use to choose one "TL" process v/s another?
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When deciding on which recipe to use, we consider size, weight, steel composition, application, and configuration of the tooling. As a rule, smaller tooling requires less time to reach saturation, however, the configuration of the tool also must be considered.
Each recipe will generate specific compound layers on the surface and varying
diffusion depths. Thinner diffusion is better suited for solder,
washout, and heat checking resistance.
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Will H-13 w/ TL out perform Anviloy?
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Anvilloy,
because it is a tungsten alloy material, does not contain any iron and will
not solder. It is totally resistant to the intermetallic
attraction of the molten aluminum in die casting. Recent 2002 tests at
Case Western have shown that Anviloy outperformed all of the test steels
without any treatment process applied. One must consider cost,
machining, size limitations, and brittleness of Anviloy steel when deciding on this
material.
ThermaLLife when tested on H-13 material
showed significant improvement over untreated tool steel.
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Does it chip or peel? |
Decarburization or "bluing" such as that which occurs when a tool has been abused during machining or grinding will have a tendency to flake off at the area of decarb. This is due to the total loss of carbon at the surface of the tool by overheating the steel when grinding or machining it. Sharp edges that
have not been properly machined are usually the most likely regions for this to occur.
It is possible to apply
MetaLLife and
ThermaLLife
in combination.
When doing this there are special recipes and sequences that need to be
followed.
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Applying over PVD coatings |
Prior to application of
ThermaLLife previous coatings
must be completely stripped or removed.
Without this it is not possible to have the proper interaction
between the gases and tool steel that provides the diffusion and compound layer characteristics.
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How often do I need to apply? |
Normally the tool is processed once with the
ThermaLLife
process when it is new and after final approval. Some customers apply it
again at the normal half life of the tool with a prior application of
MetaLLife
to attempt to close up very small and minor existing heat checks.
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Applying PVD coatings over
ThermaLLife |
With the exception of CrC, all common commercially available
PVD coatings (including
TiAlN, CrN) showed excellent adhesion characteristics when applied over
either a
ThermaLLife
or
MetaLLife
surface. See our
Balzers test.
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What about Lubricity? |
The
ThermaLLife
surface is extremely hard and smooth. Because of this there is an added
lubricity factor, similar to that obtained when doing standard gas nitriding.
If
MetaLLife
has been performed prior to
ThermaLLife,
the micro pockets formed add an additional means to retain applied lubricant and
help buffer cavitation effect which causes breakout of die material.
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Is there any type of hot work
steel that cannot be treated?
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For
a proper
ThermaLLife
diffusion process, the desired temperature has to be at least 900 degrees F
minimum with a preferred minimum of 1000 or better. Any type of hot work
steel, such as maraging, that does not have a high last temper at this point
would not be a candidate. Maraging is aged at about 950 degrees F or less and
could possibly be put at risk if
ThermaLLife
is done at a higher temperature. We are currently evaluating this
situation and doing some testing on both maraging and maraging weld done to
H-13 material. As the results are available, we will post the information here
and possibly in one of our email newsletters.
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What about doing the process to
Uddeholm's Dievar®
or 2367 material?
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There are some steels for die casting which diffuse more quickly. A special recipe
for
ThermaLLife
has been developed for these steels that will assure a proper compound zone
thickness and diffusion depth. To assure the correct recipe for the steel,
it is important to use the
Steel ID Form and inform us of your steel type
prior to
ThermaLLife.
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What assurance is there at this treatment will perform as
advertised? |
ThermaLLife
is not a panacea for all die soldering or failure problems, however, references
by NADCA in their
Die
Care Maintenance User Guide (E501) and
MetaLLife
in the
Relieving Stresses in Die Casting Dies (#531) support the fact that these are both viable
processes. In addition customer testimonies
continue to show the successes the processes are having in the field.
One major US Japanese die caster has all of their new tooling
ThermaLLife
processed to extend the die life and improve performance of automotive dies.
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If a Stress Temper of the die after
ThermaLLife is performed, what effect does this have on the process? |
The diffusion process is
done at a higher temperature than normal stress tempering (1000 degrees F) so it
does not affect the process. A stress relieve at a higher temperature or a
sustained temperature close to the final temper temperature will emasculate the
diffused layer.
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