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topic 10642

High temperature coatings for titanium


(2001)

I am looking for a coating that will protect titanium used in high temperature applications. I have tried Plasma sprayed zirconia (8Y) with no success (too porous I think). Is anyone aware of any coatings/processes that will protect titanium at temperatures up to 850 °C?

Simon Trevor
- Melbourne, Australia


First of two simultaneous responses (2001)

There are several coatings which may suffice your needs. the first one that I would recommend is a Tungsten-Carbide coating either applied by Plasma or Detonation Gun. This process has been used for years in the "Hot section" of jet engines. Other applications include the addition of Cobalt to the matrix and the use of HVOF and Super D-Gun technologies.

Good Luck.

Ira Donovan, M.S.F.
Kansas City, Missouri


Second of two simultaneous responses (2001)

What are you trying to protect titanium from?

jim treglio portrait
Jim Treglio
- Vista, California


(2001)

Ira, thanks for your response. My understanding of sprayed tungsten carbide coatings is rather limited but I have read that it is only oxidation resistant up to around 300-400 °C? Do you have any results, literature or websites that you could mention or point me to in regards to this?

Jim, we are wanting to protect the titanium from oxidation in air at 850 °C . The situation is continuous operation under a small static load.

Also, if you know of any oxidation resistant metal(up to 850C) that has a similar thermal expansion coefficient to Ti, then I would love to hear from you!

Thanks for your help,

Simon Trevor
- Melbourne, Australia


(2001)

Simon,

I have worked with these coatings in several different applications. I have worked with this coating up to 700 F without a problem. I would like to direct you to ASM International. There are several pieces of literature there that can help you in specifying particular coatings for your application.

Thanks,

Ira Donovan, M.S.F.
Kansas City, Missouri

(2001)

You should look into ion plated platinum. It will stand the oxidation but may need a diffusion barrier to prevent diffusion into the titanium. Carburizing the Ti should provide such a barrier.

Donald M. Mattox
Society of Vacuum Coaters
Albuquerque, New Mexico

Ed. note:
            Mr. Mattox is
            the author of -->



(2001)

Some years ago there were tests of cerium ion implantation to reduce high temperature oxidation of both titanium and chromium. The temperatures are in the range that you seek. The results were quite dramatic.

jim treglio portrait
Jim Treglio
- Vista, California

(2001)

Before trying all the exotic methods, how about plating 1 mil nickel followed by 100 microinch gold. Wouldn't that work? By the way, is it a continuous high temp operation or intermittant?

Mandar Sunthankar
- Fort Collins, Colorado


(2001)

Thanks for the suggestions. I am not very familiar with ion implantation, but it is something I will look into. Unfortunately I don't know of anyone who does this locally so it could turn out to be a rather expensive exercise!

Mandar, operation will be almost continuous but must be able to cycle to room temperature a number of times. Nickel and gold are completely soluble in each other at this temperature so they would not be a good combination.

Regards,

Simon Trevor
- Melbourne, Australia


(2001)

Dear Simon Trevor,

I am afraid that it might be very difficult if not impossible to shield titanium from the gaseous corrosion at such high temperatures. The coating should be without pores and has a similar coefficient of thermal expantion. I would advice you to try to apply a Pt-coating or use Pt base alloy as a material of your article. Judge for yourself: we use platina crusibles while melting some optical parts. I am dealing with titanium and coatings for 20 years.

Sincerely yours,

Andrey Igolkin
- St.Petersburg, Russia


(2004)

I need suitable coatings for plastic welding, ultrasonic horns. The material is 64AL V. The coating should be ductile enough to withstand the elongation of 100 microns.

Bhupesh Chavan
- Mumbai, MH, India



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