New Technical Paper from Remet

Application of Dynamical Mechanical Analysis (DMA) to Probe the Rheological Behavior of Investment Casting Slurries

Dr. Grant Bradly – Remet Corporation

Abstract

Generally accepted practices within the precision investment casting industry for measuring viscosity of slurries include Zhan cups for efflux time and Brookfield torque viscometers for binders. While the Brookfield can be used to measure rheological properties ceramic slurries used in precision investment casting, the abrasive fluids tends to abrade and score the polished surfaces of the spindle which effects the accuracy of measurement and leads to  drifts in calibration. In this paper, the use of Dynamic Mechanical Analysis (DMA) in a shearing mode is explored as a reliable, repeatable method of obtaining rheological information over a range of shear values without damaging the instrument. Various foundry slurries are measured and compared with laboratory and experimental slurry systems. We report on correlation of rheological properties obtained by DMA compared to Brookfield laboratory viscometer. Measurements in shear mode provides PIC foundry customers with advantages not provided by any other rheological instruments. For instance, samples can be run from high to low stiffness without any drastic volume and geometry changes to ensure correct measurements of viscoelastic properties of binder slurry systems. Since DMA works primarily in the linear viscoelastic range it is also more sensitive to differences in structure of polymer based binders.

Download the full paper from the Investment Casting Institute