Cr plating on carburized surface?? 2

[COKA]

Hi,

Can anybody tell me if we can chrome plate a carburized surface? I do not know to what depth the surface was carburized.

Thanks in advance!

Coka

 

[mcguire]

I have used hard chrome plating on high carbon steel piston rings with no problem. I can't see why there would be a problem since you're dealing with martensite in carburized surfaces, not carbides, and the carbon level is normally no greater than in a high carbon steel.

 

[unclesyd]

Hard chrome plate is used on carburized steel everyday in the textile industry. A considerable number of the guides are carburized CS and then hard chrome plated. The depth of carburization doesn't have any effect on the Cr. This is all under the control of the plater.
Carburization is done in this case to have an extremely hard surface so the chrome plate can be thinner, not have to have thickness for effective hardness.

My shop key ring is 3/16" x 2" dia. hard chrome plated carburized 1060 CS.

 

[COKA]

Thank you for a quick answer!


Coka

 

[metengr]

I would presume that the plater would need to perform a post bake operation after dip plating to avoid hydrogen cracking in the carburized zone?

 

[israelkk]

I would use great care due to hydrogen embrittlement. Military and aerospace standard prohibit using a electroplating on ultra high strength steels beyond 240000psi. The carburized surfaces are definitly are above this region.

 

[swall]

Keep in mind that carburized cases tend to be in compression, mitigating the chances of hydrogen embrittlement cracking.

 

[unclesyd]

I don't know what the procedure is now but when I was involved with the guides, 60's, there was no bakeout after plating that I am aware of. The guides as received were sectioned, checked for thickness and quality of the plating, hardness of the plating and case along with the core.

After the guides had a little wear after one about year, as stated in the previous post a lot were made into key rings which required considerable bending to close the gap of the cut ring. Never had any to crack or break.

I'll see if I can get any information if there is any bakeout. We were aware of the problems with H2 as we always baked out 4340 or D2 steel that we had Cr plated.

 

[metengr]

My general statement regarding the post bake after plating was indeed intended for high hardenability alloy steels like 4320, 8620, etc., after they have been plated. The comment made concerning compressive stresses is correct at the surface, but as you progress thru the carburized zone into the transition zone you have a reversal of residual stresses, and this is the location I would be concerned about regarding hydrogen embrittlement in certain alloy steels.

Coka's original post did not indicate the substrate material or intended service.

 

[CdotS]

What is the application? Is the coating meant to resist against sliding or abrasive wear? Is there a better surfce engineeirng technology available, other than doing carburizing + Cr plating?

 

[COKA]

The material is Ni-Hard 1, and its composition is 1.2Cr-3.65Ni-balFe, and the part is a gear.

Coka

 

[metengr]

Coka;
Ni-Hard 1 is a Ni-Cr cast iron that is normally supplied in a very hard (500-600 BHN) and brittle condition. This material is typically used for severe abrasive service environments. I have seen Ni-Hard 1 castings that can be supplied at lower hardness (450 BHN), if specified.

Just curious as to the reason for the chrome plate on an already hard surface? Is it for added corrosion protection in service? I would think that if the Ni-Hard is supplied in the fully hardened condition, all you would need is to have a lubricant to reduce friction and wear from metal to metal contact.

 

[arunmrao]

Coka! correct me if I got it wrong. Your original thread mentions chrome plate a carburized surface. Now how did you carburize a Ni Hard sample which is already high in Carbon 2.5% and above. Also Ni Hards are materials which are hard above 500BHN all through the section. How does it assist in chrome plating? I am just being curious..

Metengr is correct in his comments and pehaps a crazy though why not consider laser hardening the surface? if cost permits?

 

[COKA]

I was told that I have a charburized surface that I have to chrome plate in order to repair (and that is the only acceptable method for this piece). I have never come across a Ni-Hard 1 material before, so I am questioning pretty much everything. I went back to the suplier to confirm that the surface in question is in fact carburized. I should know more withing a couple of days.

...confused...

Coka

 

[Carburize]

Are you saying that you intend to rebuild a damaged gear tooth surface by chromium plating?

 

[COKA]

not a tooth surface, another surface

Coka

 

[Carburize]

OK
Will your client consider any other processes such as HVOF spray coating. There are a number of good coatings offered by companies such as Praxair which might perform better than chromium plating.