On Monday, June 18, 2018 at 11:43:26 AM UTC-4, Neon John wrote:
On Thu, 14 Jun 2018 13:18:17 -0700, "Howard Beel"
wrote:
Is it just marketing hype?
http://www.kyoceraprecisiontools.com...ert_Grades.pdf
Higher Hardness.
Not marketing hype. Several years ago a customer (we make induction
heaters) commissioned us to see if our heater could heat cylinders of
carbide to 4500 deg F and hold it there.
I learned a lot about carbides while doing this test. I found that
there are two kinds of carbide - nickel bonded and cobalt bonded.
Nickel is cheapest. Cobalt will withstand higher heat but is more
expensive.
The customer sent me several of each kind of carbide. At 4500 deg F,
the nickel gradually sublimes away. One can see a cloud of nickel
vapor in the argon purge area. When it reached the edge of the inert
gas, it instantly oxidized into a yellow powder. The cobalt-bonded
carbide was much more heat resistant but still sublimed a bit. The
oxide had a multitude of hues.
I recovered some of the carbide particles and looked at them under a
microscope. The nickel-bonded carbide particles had many sizes and
shapes. Most were rounded. I guess the tool relies on being ground
to shape to make the blobs sharp.
The cobalt-bonded carbide had much smaller and sharp edged carbide.
The particle size was very uniform.
I would not draw any sweeping conclusions from this other than
carbide-bonded is probably the better material. particle shape and
distribution strictly depends on the manufacturer. I have no idea who
made these cylinders.
Anyway, the tests were deemed successful. They were developing a 3D
printer that used molten stainless as the "ink". I'm under an NDA so
I can't say any more.
John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address
It's risky to generalize about sintered carbides, but, in general, the common products made from nickel-bonded carbides are industrial seals, bushings, and other wear parts. Cobalt-bonded carbides are used primarily for cutting tools.
That may explain why you saw the different grain shapes. Or maybe not; I've never seen an explanation of this point.
--
Ed Huntress