Carbide inserts in cast wear parts 1

[arunmrao]

I plan to use carbide inserts in cast metal matrix composites. I have in the past used these carbide inserts by brazing or press fit. I now plan to extend by placing them in the mold cavity and pouring liquid metal into it.It is not a novel idea,some use preformed alumina,silicon carbide grains or carbide bits.

Will the carbide soften due to exposure to high temperatures 1400-1650C depending on the alloy? Will the liquid metal wet the carbide or any specific surface treatment is needed.

Thanks in anticipation.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[swall]

What metal are you considering for the matrix?

 

[arunmrao]

It can be a low alloy steel, or high chrome iron . The parts can be crusher hammers, impact hammers ,cone mantles, vsi impellers etc.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[ornerynorsk]

I have seen something like this in drill bits (well drilling) but I am not familiar with the manufacturing process. Might be a lead in the direction you are looking for.

Good luck!

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[jwhit]

The carbides I have seen in well drilling were inserted into the body of the bit. Probably brazed in place but possibly just a press fit. I would suspect that at the temps you are looking at, you could at least be on the verge of damaging the carbides. Your carbide supplier can probably tell you at what point there are detrimental changes.

 

[arunmrao]

Drill bit inserts are fairly simple. These are inserted post machining and heat treatment as a press fit or in some cases brazed. I have had such experience in the past for some wear parts. But now,placing the carbide inserts into the mold cavity and pouring liquid steel,into it,is quite different. I know it is possible,for such products are available in the market.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[EdStainless]

I saw a demonstration where they fused (sintered?) carbide to steel backers.
Then they placed these into molds and cast them in place.
I doubt that you could get reliable adhesion just casting around the carbides.
You would need a lot larger piece of carbide, and that costs more money.

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Plymouth Tube

 

[arunmrao]

Thanks Ed,In the past, I had deposited chromium carbide (hard facing) on mild steel strips and then placed these in the molds. The results were mixed .

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[tomwalz]

Overheated carbide can "popcorn".

It is a pressed and highly compscted material so it can come apart.

These pictures show a piece of carbide that fell off the belt in a brazing oven and spent some time next to an element. The saw tip is pretty close in size to what the orginal part was.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[tomwalz]

If you use Cobalt matrix carbide remember cobalt melts at 1495C. If it works right you will get cobalt migration and an improved wettable surface.

Wetting depends on your surface. In this case I don't think wetting is an issue as the metal will shrink and hold the inserts.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[arunmrao]

Thanks tomwalz for sharing the picture. I have similar concerns, but I know for certain that Sandvik,has used carbide inserts in nodular iron, high chrome iron castings.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[tomwalz]

Sandvik is very, very good.

There are many, many kinds of carbide in the world.

Maybe sandvik can sell you the inserts.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[arunmrao]

No, they will not even discuss about that ,which I appreciate . I shall continue pursuing a solution , with a few academics that I met ,it was just hot air.

Preformed Alumina,is a simpler solution,but the crudest would be to just disperse grains of silicon carbide .

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[EdStainless]

What about a steel bonded carbide? There are a couple around, those might cast in well.

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Plymouth Tube

 

[btrueblood]

Tom,

The insert that showed gross expansion was "cooked" in air, it appears? I see a lot of cobalt blue (oxide). I'd wonder if a sintered carbide would behave like that if sitting in the bottom of a mold.

 

[tomwalz]

Good question. No idea.

I have seen papers suggesting that the heat of cutting can aid in carbide wear.

The L.B. Toney patent talks about a high temperature salt bath improving wettability. One explanation given for this is Cobalt migration to the surface. I believe this was 2200 F though.

Sandy Stewart talks about the effects of heat on carbide but his research was cutting MDF.

Carbide can go though an ordinary building fire without damage.

Carbide does not seem to be adversely effected by brief exposure to 2,000 F.

We deal with carbide brazed to steel for tools. We are very careful not to get the carbide too hot because of the effect on the braze alloy and the steel, etc.

I have only been at this 30 years so I have a lot more questions than answers.

With straight ceramics I would worry about thermal shock due to the extremely low thermal conductivity.

Maybe 20 years ago soembody called about removing coatings form machining inserts. I needed a break so I went back and experimented. I think we did something like putting them into a 1500 F oven for a half hour. The coatings pretty well flaked off which I tended at attribute to thermal expansion. Could have been they oxidized or both.

If this were my project I believe I would buy some material samples and heat them with an oxy / acetylene torch to see what happened. You could probably get some cheap samples as inserts on eBay.

If the inserts held up then melt some steel over them.

It is pretty crude but would provide some information. Undoubtedly better information than my guessing would.

I really like, fast, cheap experiments.

Tom




Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[EdStainless]

How about plating the carbide with a alloy that would help promote bonding to your casting alloy.
Something with very high solubility in steel and little risk of secondary phases.
I don't have my phase diagrams handy but maybe a Fe with some Ni and Cu additions. I don't know how much you could lower the melting point. Adding a lot of Si may help also.

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Plymouth Tube