How to handle Nobel CrCo frameworks

[elcdt2]

I/ we have sent out a few frameworks to Nobel (Crco),and we are having a terrible time keeping the porcelain from cracking. When the porcelain fractures, it is down to the framework, and there appears to be a very heavy greenish oxide. This oxide layer looks nothing like any np alloy I have ever seen. I asked the rep to send/ email me the specific handling instructions, and all I got was the sales literature. If anyone here as any ideas, I would greatly appreciate the input.
We are surface finishing, luminous oxide blasting at 2.5 bar, steaming, then degassing the units before opaque.
Thanks in advance.

 

[CatamountRob]

Whats the CTE of the alloy? What porcelain are you using and what CTE range do they recommend for your porcelain. My guess is your answer might be in there.

 

[elcdt2]

I have double checked the CTE, and they are in range. We are using Ivoclar POM system. I'm gonna try blasting the oxide off, even though the manufacturer says nothing about it.

 

[Gru]

We do not fire our milled CrCo to oxidize it before opaque, simply sandblast and ultrasonic clean. This includes InLine POM. However the pressed porc. often will fracture on a sharp line angle or if the porc. is too thick or inadequately supported. Is Nobel your only option or could you test another milling center's CrCo?

 

[Bobby Orr ceramics]

make sure all sharp edges are rounded.... any NP alloy is more sensitive to internal shearing stresses.

green oxide is telling me you're heating up the alloy too much when oxidizing...... green oxide is overheated chromium. Stop steaming....use ultrasonic,

layer the ceramic with proper CTE ceramic...... mix it with water.