Abrasive Diatomaceous Earth Needs Hard Metal to Mix.

[agent008]

Hello,

I'm working on a project involving Diaomaceous Earth (DE)and water mixing together on a rotor/stator type mixer.(Please see link)

The mixer was used for 2 months only. We found out that the mixing assembly wore out excessively. By the way the mixer is made of SS316. From one site the hardness of DE is 7 out of 9.

Need your help/tips/suggestions on choosing economical:

1. Boronizing. One of our colleague suggested boronizing the mixing head and check them every week. If there is a significant wear, boronize it again.

2. Hard Chrome plating. My concern with this is that since mixer is rotating at high speed. The chrome plate might just be chipped off.

3. Special Alloys. I'm trying to find a special metal that has a high hardness and tough enough not to break.
D2 alloy - one website showed it has a high hardness but low toughness.
S7 - the same website showed it has mid hardness and mid toughness.
Please also suggest any alloy you know.

Thanks!

 

[agent008]

Below is the link:

http://www.mixers.com/options.asp?m...al Stage Rotor Stator Mixers&Image=inline.jpg

It is the fifth photo from top

 

[EdStainless]

complex geometry, many edges, high speed; all of these factors lead me to not think about coatings. How important is toughness, is there any risk of impact or debris?
A tool steel is one option, but you do need some corrosion resistance. Look into 420 or 440C.

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Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net

 

[TVP]

I agree with EdStainless that coatings do not seem to be the best option. Martensitic stainless steels like Type 420 or 440C stainless steel seem like good candidates. You might be able to use Type 316 with a surface treatment like Kolsterising (

http://www.kolsterising.info),

but I don' think this will be as robust as a part with a fully martensitic microstructure.

 

[Robertmet]

If that lasts only two months I don't think 420 will give enough wear resistance. Give 440C a try and if that's not enough

http://www.crucibleservice.com

has some special alloys like S90V or MPL-1. How much of a corrosion problem is DE.Isn't that just Silica ?

 

[EdStainless]

IT isn't the DE that I worried about, it is the abrasion exposing fresh metal to the water.

Crucible might also want to sell you CPM420V, it will out preform 440C by a good margin.

= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net

 

[Compositepro]

Why are you using a high shear mixer? DE is usually easy to disperse into water. It is done all the time with swimming pool pumps. With your mixer you are probably reducing the primary particle size of the DE which makes it a grinding operation. Grinding does indeed result in abrasion. You might consider using an eductor with a clean-water jet for your mixing operation. No moving parts. Also, in some cases rubber will have more abrasion resistance than a hard material.