Experimental characterization of CaCO3 powder for use in compressible gaskets up to ultra-high pressure

High Pressure High Temperature (HPHT) equipment is used for commercially produce synthetic diamond and other polycrystalline products. The common denominator for almost all high-pressure systems is to use capsules where a powder material encloses the core material. In this work, the properties of CaCO3 powder up to ultra-high pressure have been studied using an instrumented Bridgman anvil apparatus. Bismuth phase transformations were used as fix point calibrant. Three different parameters were studied, density, moisture and diametral support dependence on the load–thickness and pressure build-up. The experiments are done such as they can be used as validation and calibration of constitutive models for finite element simulations of the HPHT-process. The results show that increasing the density of the powder compact increases the load needed to reach maximum pressure. In addition, the residual stresses in the compact seem to delay the phase transition on the down-ramp. Moisture content within 0.5%–1.2% does not significantly influence the compaction properties of the discs. Diametral support increases the phase transition load.

The purpose of this study was to investigate the compaction properties for a CaCO3 powder mix up to ultra-high pressure (10 GPa) and how these properties affect the gasket behaviour. Different parameters of the powder are investigated, i.e. initial density and internal moisture. A set-up, supporting the outer diameter of the compact, commonly used for gaskets in the belt apparatus was also investigated. The experimental results are in terms of pressure instrumentation in the Bridgman anvil apparatus together with load–displacement curves of the powder compacts. The instrumentation is done so that it can be used to calibrate constitutive models.Figure optionsDownload as PowerPoint slideHighlights
► A Bridgman anvil provided load-thickness data and pressure data up to 7.7 GPa.
► Compact density/mass affects the pressure transition load and load- thickness behaviour.
► Moisture content did not influence the phase transformation load or the load- thickness.
► Diametral support increases the phase transformation load.