Titanium surface treatments to avoid fretting and wear

[cavva78]

Hello,

I have to manufacture a part in Ti6Al4V due to stiffness reasons, for a space application. Our customer told us that, due to poor resistance of this material to fretting and wear, we'd better apply a surface treatment. The suggested alternatives are anodic oxidation as per SAE AMS 2488D, hard coating with tungsten carbide or cobalt thermal spray. After a brief investigation with our suppliers I found that they don't know the AMS normative, and a possible solution could be a CrN coating, with a hardness 2500-2700 HV and a thickness of 2-3 micron. What do you think is better to use? This part must be also electrically conductive in 4 small areas: how can I treat these areas so that they are conductive? On aluminium we usually apply anodic oxidation protecting conductive areas, then we treat them with alodine.

Thanks and regards.

Marco

 

[CoryPad]

The thin, ultrahard CrN may not perform that well on Ti because of the large differences in elastic moduli and surface hardness. I would go with anodizing or thermal spray.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[unclesyd]

Here is an anodizing, Tiodize, we use with Ti parts that have potential fretting and wear problems.

http://www.tiodize.com/anodizing.html

 

[cavva78]

Thanks unclesyd, I found Tiodize. The problem is I'm in Italy and the suppliers I contacted don't use the AMS 2488 / Tiodize anodization procedure, so I would like to know if there is any alternative.

Marco

 

[unclesyd]

I would contact Tiodize to see if they have represenetives in Italy. Since they are big in racing they might know about someone in your arena who uses Tiodize and similar process.

 

[TVP]

Marco,

Since this is for a space application, you may not have the luxury of using a local supplier. If you have already contacted more than one company and they are not capable of meeting the requirements of SAE AMS 2488D, then you should either use a qualified North American supplier like Tiodize, General Magnaplate, etc., or you should investigate the thermal spray coating option. Sulzer Metco will be able to perform this in Europe using a Mo-based coating.

 

[cavva78]

Thanks for your replies. Does anyone know if there is a standard to use as reference when performing a passivation (cleaning) of titanium ti6al4v?

Marco