Powders Expertise - Investment Casting Control

The Challenge

A company employing investment casting to create metal alloy components approached Ceram (now Lucideon) to help with intermittent problems relating to the use of ceramic slurries. These slurries are employed in creating the ceramic cores and shells that respectively form channels and outer surfaces of the final cast metal components.

A range of faults can arise including

  • Pimpling (where unwanted air bubbles in the shell slurry end up close to the cast surface and become impregnated with molten metal. Pimples on top of the cast metal surface arise)
  • Core collapse (catastrophic collapse of the ceramic shell during metal casting)
  • Primary coat lift (a condition whereby the first ceramic coat layer, deposited by dipping the wax model in a ceramic slurry, is disturbed by subsequent dip coatings. A void arises that molten metal ultimately infiltrates into)

What We Delivered

Thanks to our powders expertise, we were able to: 1) Optimize the Particle Size Distribution (PSD) and 2) Maximize the wt% solids loadings (via control of Zeta potential) associated with the ceramic powders in aqueous suspensions. This in turn delivered a good rheology for building up consistent bubble-free core layers as well as minimizing ceramic coating contraction upon drying that can lead to crack formation.

Value to the Client

The client was able to consistently maintain high yields and better surface finish in cast metal items through employing QC tests and protocols stimulated by the Ceram investigation. Spin-off benefits include less waste, reduced pos-casting finishing work and consistent delivery to time-scales agreed with clients.

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