Wear resistant material

[Guibar]

Hi everyone,

We are looking for materials resistant to ash flow. We burn coal in our steam boilers, but the coal in south Brazil is not the best thing, in fact, is one of worst coal in the world. Usually we have 40% of ash. We are facing severe wear of some radial seals in our pre heater (Ljungström).

Regards

 

[arunmrao]

Basalt tiles .

 

[tamal1475]

Choosing appropriate wear resistant material is related to specific conditions as well as cost. The choice should be optimum so that the decision is cost effective. The options could be alloy steel, alloy cast iron, ceramic, composites etc. What is your current material specification?

 

[Guibar]

Nowadays we use the simplest low carbon steel. We haven't tried any new material. Carbon steel was used just because it was cheaper, but the cheaper is costing us too much.
We have 2 kinds of limitations. We have to be able to screw the material on a carbon steel plate and it's preferable that it has a L shape.

 

[tamal1475]

You may use Ni-Hard castings as per ASTM A532 in this area. The hardness would be more than 500 BHN. You may have to design it suitably to fit in place. Plain low Chromium white iron could be a cheaper alternative.

 

[arunmrao]

27% high chrome iron casting offers a very cost effective solution. NiHard castings tend to crack in the high impact zones and are expensive. My previous recommendation of using Basalt is well accepted ,if cost of down time due to replacement ,is considered.

 

[EdStainless]

I have had better luck with NiHard than with straight Cr white iron when it comes to toughness.
The size and shape matters a lot.
Either of them is going to be light years better than mild steel.
They will need to be cast to the shape that you need.

If you want to try something that can be cut and formed you could look at a martensitic stainless steel.
These alloys can be cut, drilled, and bent when they are annealed.
Then they can be quenched and tempered to achieve fairly high hardness.

410 (0.14 %C) (make sure that you don't get the low C version, it won't harden)
420 (0.25 %C)
425 (0.55 %C)
440A (0.62 %C)

http://www.atimetals.com/products/Pages/ati-440a.aspx

Look at the data sheet.

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Plymouth Tube

 

[metengr]

Ceramic lined pipe is what is used for pulverized coal supply piping, and the same concept would be used for handling bottom ash (wet) piping. Nothing else works for coal and ash handling systems. I would look at ceramic seals for the air heater.

 

[tamal1475]

The Regenerative Air Preheater that we make are with only grey cast iron wear plates, which are replaceable and attached to the seal frame. There is no need for abrasion resistant material since fouling by fly ash is very minimum. If you are encountering wear, please investigate the reason and if necessary go for harder grades of cast iron. Since there is no impact in this area, brittleness would not be a problem.

 

[Guibar]

tamal1475, abrasion by fly ash is a problema for us and we have to live with it. As I said before, our coal have a lot of ash. So we do have to look for more resistent materials. Any problem with the variation of temperature for cast iron?

 

[arunmrao]

No variation in temperature or thermal shocks, if you are referring to, should not be an issue.

 

[tamal1475]

In a RAPH the temperature may fluctuate between 400 deg C to 130 deg C and very slowly. So, do not expect any problem.

 

[Guibar]

Hi erveryone. Let me show a picture of the seal I was talking about. You can see the wear in some points.