What coating for center section?

[wing3r09]

My 7 blade HX-35 center section has seen better days. I am getting a rebuild done, but before I send it out I am going to get it coated. The compressor housing is going to get a black powder, and the turbine housing a ceramic TBE (White lighting) from Swain Tech.

My question is what coating for the center section? Powder or Ceramic?

My thought is that you want the center to be cooler and not hold in heat. What do you guys think?

 

[llxkevinxll]

Not an expert by any means but here are some thoughts.

1. I know some non-water center sections (like the Holset) from Precision have cooling fins cast into the part to increase surface area for cooling. I'd assume they are doing that because they feel there is a need for it to be able to radiate heat away better. Insulting with ceramic coating would make that far less effective, cooling fins or not.

2. Typical applications of ceramic coating are applied to the outside and inside of a part. Applying a coating to the inside of a turbo center section is likely a very bad idea. So you'd have a coating on the outside only. There are a lot discussions around allowing heat into the metal part and then holding it there when a coating is applied to the external face but not the internal. This is mostly applicable to headers but I assume the same principle would apply here. I'm not sure on all science behind this claim but Jet Hot (who I would consider a leader in this field) does not coat the inside of "turbos" (I read that as turbine housings), as stated on their FAQ page.

3. In addition to #2 above, there is a potential for ceramic coating to flake off after many heat cycles. While coating the inside of a turbo would be a bad idea for many other reasons, coating the inside of a part where flaking could cause damage is a risk. This includes manifolds and piping pre-turbine wheel as well.

I'd you'd like to paint it with an engine enamel or similar that would probably be OK. It will not hold the heat in like a coating and would cover up the rust and blemishes. Not sure on the durability though given the extreme environment in which the center section lives.

Again, I am not a material scientist, but those are my thoughts.

 

[wing3r09]

@llxkevinxll I appreciate the input. Same as Jet Hot, Swain Tech does not coat the internal portions of turbo parts (as I read on their site).

As for your points #1 and #2, I agree I do not want to keep heat trapped in something that is trying to cool. Swain Tech also as a BBE coating that they describe as a heat emitting coating. They state the coating is commonly used on intercoolers and brake calipers. Possibly an option for a turbo center section.

 

[JusMX141]

I use a ceramic cast coating on the bearing housings of the turbos I service and it holds up exceptionally. You must take special care not to get anything on any of the sealing flanges or inside the bearing housing...you literally want the exposed part of the bearing housing blasted/coated and that is all.