I am working with alumina ceramic. During the binder burnout of
injection molded components, blisters appears on the surfaces of the
components. Also hard skin develops on the surface of components which
appears as thin laminates over the sintered body. Kindly help me in
this regard.
Best Regards
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You didn't give a lot of detail about processing conditions, etc, but here is my $0.02:
The blistering sounds like it is related to heating rate. In binder- treated parts, if the temperature rise in the debinder furnace is too fast, i.e. the parts are heated too rapidly, it can cause the binder to outgas at a high rate, creating the blisters. I suggest decreasing the heating rate and seeing if that works.
For the second problem, it may be atmosphere related, specifically, too dry an atmosphere. In my experience, you want a wet atmosphere for successful debinding. The wet atmosphere breaks apart the long-chain binder molecules and flushes them out of the furnace. It sounds like what you are seeing is the binder thermally decomposing in/on the porous part surface, rather than being flushed away from the part surfaces. What is the atmosphere source? I have seen equipment where the atmosphere is bubbled through water to add water vapor to it before it is introduced to the furnace.
Also, make sure you have good atmosphere flow into the furnace. As the binder molecule chains break apart, they need to be continually flushed out and replaced with fresh atmosphere.
Hope that helps some.
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Mister G

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