Tungsten carbide or silicon carbide? Which is the better option? 2

[Priya]

In a direct impact erosion application which wouild be the better option: tungsten carbide or silicon carbide tiles? The application is in a pulverised coal pipline at a splitter section where we have been experiancing high wear on the nose piece of the splitter. We've got the above two tiles to choose from. which one should we choose ?? or Is there a better solution available?

 

[Ceramicguy]

It will depend upon the impingement angle of the pulverized coal. The closer the angle of attack is to 90 degrees the more desirable is the bonded tungsten carbide. The metallic binder will tend to hold the WC particles in place. At shallow angles of attack the softer metallic binder phase in the WC will tend to be eroded. At intermediate angles the best advice I can give is try it and see what happens. Remember one thing; in sandblasting where the angle of attack is shallow ceramics exhibit exceptional wear properties. At steep angle of attack rubber offers the best performance with ceramics a distant second or third.<br>
Hope this helps. Get back to me if you want more info.

 

[joescan]

lost of info here

http://www.azom.com/details.asp?ArticleID=1203

 

[potter]

Try Omegaslate in the uk,they make precisely the linings you seek,for the purpose you desire.

 

[NADDIR]

Dear priya,
have you tried to plasma spray.
i feel the best result could be obtained by using a nitride bonded SiC powder.
coating can be either with plasma or HVOF although my personal preference is for plasma operated at >mach2 speed.
regards
naddir

 

[tomwalz]

There is a lot of different kinds of WC. It might be worth looking at nickel bonded from sintex.

Tom

 

[Bugman]

Dear Priya,
You may be well advised to check that you are using the correct grade of silicon carbide as there are several different types. While I could write pages on the different types, I think it would be more beneficial to point you to

http://www.azom.com/SearchResults.asp?MatKeyWord=silicon+carbide,

where you can find the relevant information.

 

[warmage]

Dear Pryia:
Long ago in a far off place called Dunbar,West Virginia.
I was employed by a company then known as
Delta Services.
WE worked on Bird centrafuge type filters and
we had a similar problem with the discharge
ploughs,they were made of cast stellite. They
lasted about 2 weeks. We worked with some good
people from what was then called Combustion
Engineerings Ceramics Div; I have no idea what
they are called now. We used tiles of Alpha
Silicon Carbide to armor ploughs of stainless
steel....life went up to about 6 weeks.
Which is just about the best you can do
considering how blasted erosive a coal slurry is.
Try that.
Warmage

 

[ceramicmike]

An engineering grade reaction bonded silicon carbide should have a hardness of 3000 to 3500 Vickers, whereas Sintered tungsten carbide might have a hardness of 1500 Vickers.

An engineering grade reaction bonded silicon carbide would be more wear resistant than Tungsten carbide in puverised fuel blowing applications in which silica grits are present, as long as the conveying velocity is less than 80 metres per second.

 

[tomwalz]

True, of course.

However Sandy Stewart at Mississippi State has done a nice job separating 'wear' into four mechanisms. His work is in wood and I am not sure how it relates to coal but it does give food for thought.

Mississippi State University Forest Products Laboratory
P.O. Box FP
Mississippi State MS 39762


Tom

 

[ceramicmike]

Wood, particularly in the form of pneumatically conveyed saw dust, can be extremely abrasive. An engineering grade RBSiC can offer 200 times the wear life of cast iron.

 

[tomwalz]

Dear ceramicmike,
Did you get info on the ASM symposium on hardmetals and related materials past, present & future? Pittsburgh, October 2003. There is a call for papers out now. I am on the committee would really like to see papers explaining industrial applications or predicting industrial applications. SiC in wood would be fascinating.

tom

 

[ceramicmike]

Hi Tom,

No, I haven't received info on the ASM symposium on hardmetals and related materials past, present and future. I've not much experience of SiC in wood wear applications; alumina ceramics seem to do the job quite well, at the moment. Using RBSiC's, like RESILIDE, in wood applications, unless it is for high temperature/corrosion applications, would be like using a sledgehammer to crack a nut. RESILIDE is an expensive, but top of the range ceramic.

 

[JimMetalsCeramics]

It is a more complicated question than that. Are you sure that the tungsten carbide is not cemented with cobalt?

For direct impact, erosion resitance will be a function of both hardness and fracture toughness. High-grade SiC is harder than WC. Cemeted WC is tougher than SiC.

 

[tsapa]

From what I've seen out there, WC is available only in thermal spray form (0.008&quot; to 0.01&quot; thickness), whereas SiC can be made to suit (up to 1&quot; thick or more). Therefore the best option would be to epoxy sintered SiC tiles onto the wear area rather than thermally-spraying WC. The extra thickness will offer you much more life.

 

[tomwalz]

WC comes in lot of sizes as solid parts. I recall seeing something about the size and shape of a small beer keg that was going to be used as a roller in a steel mill.

Also there are other binders than just cobalt and there are new technologies such as reinforced WC, binderless WC and similar.

Tom