porc. bonding.

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Rugardave

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Hey old timers, we've been using a barium/nickal free metal for a long time Lately porc. has been debonding. Opaque and all right down to the metal.. Nothing is sticking to the metal. We cast with a torch and follow the instructions for preparing the metal. Not all the units, but once in awhile. I always had to almost grind off the porc. and opaque to redo the crn. Now this is starting to happen. Obviously there is no bond and I want to know why? Any thoughts?? In my time I've used every thing from high noble to non-p and started before non-p came out and was one of the first to use non-p and I've never seen this. Thx, Dave
 
JMN

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What's the degas/oxide burn layer looking like? Any change at all visibly?

have you checked vac system/lines?

Is it a furnace for degas and one for buildup?

you, personally, are doing these cases or is another handking anything after metal finishing. Not inckuding sandblasting. Sometimes oils fro unaware hands have a way of making things odd.
 
CatamountRob

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Either the oxide layer isn’t forming properly, check everything and make sure you are following the oxidation firing instructions exactly and it wouldn’t hurt to re-calibrate your furnace, or it’s over oxidizing and the oxide layer is coming off. Is there oxide stuck on the opaque on the pieces that come off or are they clean? Some alloys require sandblasting after oxidation. It’s also possible that the alloy is contaminated or overheated which can change the composition, so start over with fresh alloy. If you are steam cleaning the copings try not steam cleaning them to make sure they aren’t getting contaminated from the steam cleaner.
 
sidesh0wb0b

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pics from start to finish. but i concur with the above. something is off in oxidation more than likely.
 
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After firing it's very dark, then sandblasted. As far as debonding the porc. comes off clean. opaque and porc together, with no oxide on the metal or opaque. I'm still reading trying to figure this out. Thanks again for your help. I know it could something simple. I cast new ingots every time and I handle all steps except the porc. I'll check again and keep you posted. Thx
 
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honestly, it could also be something as simple as a nearby thunderstorm wigged out your furnace.

Have you checked it's programs to ensure they are still programmed to be what is supposed to happen?
 
sidesh0wb0b

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After firing it's very dark, then sandblasted. As far as debonding the porc. comes off clean. opaque and porc together, with no oxide on the metal or opaque. I'm still reading trying to figure this out. Thanks again for your help. I know it could something simple. I cast new ingots every time and I handle all steps except the porc. I'll check again and keep you posted. Thx
start with the alloy treatment. verify with the instructions that its supposed to be blasted after degas. reread all instructions and walk through the steps. if its debonding clean off the metal, its for sure an oxide issue. how that issue is being created is the question
 
Contraluz

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After firing it's very dark, then sandblasted.
The oxide is there to provide bond. So, unless your metal manufacturer indicates blasting it off, I would not do so!

Now, there are NP metals that do not need oxide firings, but straight wash application. It will form a 'green' film, which can be streamed off. A thorough opaque application will deal with that. As it does with a 'dark' oxide layer.
 
CatamountRob

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Do the instructions say to sandblast after you oxidize it?
 
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There's only a few things that cause bonding failures, and once you solve this problem I would strongly suggest changing to Talladium Tilite NP which has a light oxide. 1. Check propane setting, to high will lose bond. 2. Don't over heat alloy. 3. Steam cleaning can be your worst enemy. 4. Degassing temp incorrect, to hot. 5. Correct temp for wash/bonding opaque layer is critical. Lastly, with bonding issues I would not use an air gun. Kind of surprised your not having gassing issues which is a good thing and makes this problem easier to solve.
fyi.... haven't used NP since the 80's but bonding problem is pretty simple to solve.
 
TheLabGuy

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There's only a few things that cause bonding failures, and once you solve this problem I would strongly suggest changing to Talladium Tilite NP which has a light oxide. 1. Check propane setting, to high will lose bond. 2. Don't over heat alloy. 3. Steam cleaning can be your worst enemy. 4. Degassing temp incorrect, to hot. 5. Correct temp for wash/bonding opaque layer is critical. Lastly, with bonding issues I would not use an air gun. Kind of surprised your not having gassing issues which is a good thing and makes this problem easier to solve.
fyi.... haven't used NP since the 80's but bonding problem is pretty simple to solve.
#3 would be my first guess...are you steam cleaning your copings after you finish/prep them? Steamers have highly contaminated water in them is why we are suggesting this and results in exactly what you are describing.
 
rkm rdt

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trim the metal, sandblast and opaque. No need to degass. 2th hasn't degassed since he bought beno.
 
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Rugardave

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Hi guys, we don't steam clean. will check all the levels and keep you posted. We're redoing a couple of cases right now.
 
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Rugardave

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So, just so you know, after looking into this issue and talking to both metal and porcelain people we have been using a metal that's not recommended and also didn't know of a bonder. In the old days we used a bonder at times with NP so I guess that explains the debonding. We have some cases to redo, and if anything else comes up I'll keep you posted. Thanks again for your help. Never too old to learn.
 
JMN

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So, just so you know, after looking into this issue and talking to both metal and porcelain people we have been using a metal that's not recommended and also didn't know of a bonder. In the old days we used a bonder at times with NP so I guess that explains the debonding. We have some cases to redo, and if anything else comes up I'll keep you posted. Thanks again for your help. Never too old to learn.
What metal were you using?
 
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What metal were you using?
A barilium and nickel free from a large supplier on the west coast The two materials were not compatible. and the porc mafg. never mentioned anything about a bonder.
 
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A barilium and nickel free from a large supplier on the west coast The two materials were not compatible. and the porc mafg. never mentioned anything about a bonder.
Try Talladium alloy that's matched to your porcelain, no bonder needed plus light oxide. I used it for several years without any nickel problems with patients. This was in an inhouse lab plus working with 5+ outside accounts. Never once had bonding problems, actually a trouble free NP for us.
 
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FASTFNGR

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Hey old timers, we've been using a barium/nickal free metal for a long time Lately porc. has been debonding. Opaque and all right down to the metal.. Nothing is sticking to the metal. We cast with a torch and follow the instructions for preparing the metal. Not all the units, but once in awhile. I always had to almost grind off the porc. and opaque to redo the crn. Now this is starting to happen. Obviously there is no bond and I want to know why? Any thoughts?? In my time I've used every thing from high noble to non-p and started before non-p came out and was one of the first to use non-p and I've never seen this. Thx, Dave
It could be all the above from furnace calibration to not sandblasting after degas or also it could be hand oil contamination and wrong liquid used if opaque is not a paste.
 
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Rugardave

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We've used Talladium metal before and it did work fine but ended up with the metal we use now, I can't remember how. Thanks again.
 

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