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Need a coating better than Titanium Nitride (TiN)


A discussion started in 1999 and continuing through 2017 . . .

(1999)

Q. I'm searching for a surface treatment for mold knock-out pins made of H-13 that can stand up better than Titanium Nitriding. The pins see temperatures in excess of 500°F and need to be self lubricating. We are molding small parts and the present coating breaks down after a short cycle allowing the pins to scratch. I've tried a few of the higher profile brand name coating processes without much success.

Bob H [last name deleted for privacy by Editor]
- Essex, Connecticut


(1999)

A. Hello, Bob.

Titanium Nitride has taken over some of the applications formerly associated with hard chrome plating and has proven better sometimes, but not always! Have you tried chrome plating -- which offers not only hardness and wear resistance, but lubricity and low coefficient of friction as well?

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(1999)

A. As far as hard coatings go TiN is really the bottom of the barrel. Other coatings that might work better for you include TiAlN, AlTiN, Aluminum oxide. Maybe CrN or CrC. Most all of these are available through the larger coating houses.

If this is for a die casting operation and the pin surface is in contact with the molten aluminum at some point then I would definitely suggest using Titanium boride if you can find a supplier but otherwise use CrC.


John Davis
- Berthoud, Colorado, USA


(1999)

A. Are you sure a coating is necessary? Our research shows that a lot of the galling created in mold knock out pins is created when the retained austenite in the pins transforms to martensite. All heat treaters leave between 9% to 20% retained austenite. The martensitic crystal is larger than the austenitic crystal and the part grows as the austenite is transformed by the heat and vibration of molding. Since there is very little clearance in ko pins, the part seizes.

Cryogenically treat the mold and pins. This will convert the retained austenite to martensite, stabilize the mold metal, and will increase the wear resistance of the moving parts of the mold and the gates and runners. We have achieved excellent results for our customers by just doing this. However, a coating added to the pins before the cryogenics will work synergistically with the cryogenics.

F. Diekman
- Streamwood, Illinois


(2000)

A. The suggestion of using a Titanium diboride or Chromium carbide coating appears to be a sound one. Have you tried electrospark sputter deposition of these coatings? Some of our clients with screw machine collets, where galling is common, have benefited by this process.

Ram K. Iyengar, Ph. D.
- Littleton Massachusetts


(2001)

Have you considered coating with diamond-like carbon (PECVD), then ion-implant using a few hundred KeV nitrogen ions? One ends up with a nitride/carbide layer within the surface which is in compression, not tensile, so is not dependent on the young's modulus of the substrate. Dislocations further into the bulk metal are 'pinned'. The result is a very hard, wear-resistant surface with good release properties. I had this done for a mold to produce microtitre high-density wells in the UK 4 years ago. Should be companies in the USA too.

Bob Sunderland
- Northwood, England


sidebar2 March 28, 2009

? Many many moons back, Bob H of Essex, Connecticut wrote:

"I'm searching for a surface treatment for mold knock-out pins made of H-13 that can stand up better than Titanium Nitriding. The pins see temperatures in excess of 500°F and need to be self lubricating. We are molding small parts and the present coating breaks down after a short cycle allowing the pins to scratch. I've tried a few of the higher profile brand name coating processes without much success."

There were many suggestions including one from me. Bob please tell us did you find a solution?

Or is the website a grave yard of good suggestions?

Ram K. Iyengar, Ph. D.
- Littleton Massachusetts


March 28, 2009

Hi, Dr. Iyengar. Sometimes we readers have a fairly interactive discussion with the original inquirer; sometimes they get back to us months or years later. But over twenty thousand people visit this web site each day; it's no graveyard. Some readers are forbidden by company rules from posting -- but certainly they profit from reading solutions to problems that echo their own.

In a household hints column in a magazine, an inquirer once told Heloise that she spilled red wine on her blouse and asked how to get the stain out. The answer started "If the spot hasn't dried ...", and it strikes us there there is not a chance in a million that the original inquirer's spot had not dried in the many months before publication, but that the answer was actually intended for the readers, not the original inquirer. Rest assured that even though the original inquirer did not respond, your advice was certainly not wasted.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



Mold coating to prevent Polyethersulfone adhesion

November 25, 2016

Q. I'm having problems injecting Polyethersulfone. It presents adhesion to the mold, causing the final product to break on key points. Do I need to apply any kind of counting to the steel, such as Chrome plating or Titanium Nitride?

Marcello Iliescu
- Figueira da Foz, Portugal


November 26, 2016

Hi Marcello
You should ask your supplier of PES for advice. The problem may be in the mold design or molding conditions; temperature,pressure etc. It is unlikely that we can help you on line.

geoff smith
Geoff Smith
Hampshire,
       England



January 1, 2017

A. Hi Marcello,
Can you try silicone spray as a release agent?

blake kneedler
Blake Kneedler
Feather Hollow Eng.
Stockton, California



February 13, 2017

A. Best permanent release coatings are (from fair to excellent):
Plain high phos electroless nickel
TiN
Regular hard chrome (flash)
Thin dense chrome
Electroless nickel composite with Teflon particles.
Also, if you need to paint, glue or weld something on top of your molded parts do not use silicon release agents.
Finally, review you draft, search for deformations, negatives, etc.
Good luck!

guillermo marrufo
"Respectful Mexico/USA dialogue" - Monterrey, mexico


February 2017

thumbs up signThanks cousin Guillermo.

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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