Material Preparation - Diamond Polishing Suspensions and Pastes

Each material, application and specific application can require specialized methods for Material preperation prior to analysis. Diamond Polishing Suspension and pastes are routinely used for the preparation of most materials surfaces due to their high removal rates.  Available in a wide range of micron sizes, carriers and diamond type MetaDi™ diamond products are a versatile preparation tool.

Depending on the material, a range of polishing techniques specifically designed to produce the best result can be employed. Typically featuring either a 2 step or a 3 step polish,  progressively polishing to a finer finish.

Polishing Solutions by Material

Table 1. Recommended Polishing Methods by Material

Diamond Polishing Suspensions & Pastes

A range of Diamond polishing suspensions and pastes have been developed to work best with certain materials, offering different micron sizes, carrier solutions and application techniques.

Diamond is routinely used for the preparation of metals, ceramics due to the high removal rates. The cutting rate is even further enhanced when selecting polycrystalline diamond rather than monocrystalline. the increased number of facets on the polycrystalline structure enables efficient cutting and minimal deformation.

When working with water sensitive or soft materials that have a tendency to embed abrasive particles the paste is your best choice. However, if you are interested in a fully automated approach, diamond suspensions are required.

How are Diamond Suspensions used?

MetaDi Diamond Suspensions are the industry standard for routine metallographic, petrographic or meramographic applications due to high removal rates and quick, easy cleaning of specimens. Monocrystalline diamond particles consist of single grains that have sharp edges which ensure clean and efficient cutting action providing high material removal rates.

The Sharp Edges of Monocrystalline diamonds ensure clean and efficient cutting action.

Image 1. The Sharp Edges of Monocrystalline diamonds ensure clean and efficient cutting action.

Polycrystalline diamond particles consist of angular, blocky shaped grains providing numerous cutting facets, resulting in less deformation and a superior surface finish. MetaDi Diamond Products are nontoxic, noncombustible and enviornmentally safe.

Angular, blocky-shaped polycrystalline diamonds provide numerous cutting facets on the particle surface, resulting in less deformation.

Image 2. Angular, blocky-shaped polycrystalline diamonds provide numerous cutting facets on the particle surface, resulting in less deformation.

Pastes are typically applied to a clean cloth by rotating the platen at approximately 50rpm and by placing the syringe tip about 2in [5cm] out from the center of the platen.  Start dispensing the paste onto the cloth, resulting in a spiral pattern, if the bead is raised, too much product has been dispensed.

Polishing Oil & AutoMet Lapping Oil recommended for use with MetaDi Pastes or materials sensitive to water.

MetaDi and MetaDi Supreme Suspensions

  • Contain synthetic diamond graded for particle size as well as shape
  • Diamond particles are uniformly suspended for ease-of-use and consistent application
  • MetaDi suspensions contain sharp, blocky monocrystalline particles that provide clean and efficient cutting action
  • The angular polycrystalline particles of MetaDi Supreme provide additional cutting facets resulting in less subsurface deformation
  • Available in both water-based and oil-based carriers
  • Suspensions are applied using a spray nozzle or with the automated dispensing system such as the Burst Dispensing System
  • All Diamond suspensions are nontoxic, noncombustible and environmentally safe

MetaDi Diamond Pastes

  • Diamond pastes are best suited to materials prone to diamond embedding
  • Available in MetaDi – natural monocrystalline particles, MetaDi II – synthetic monocrystalline particles and MetaDi Ultra – a blend of natural and synthetic polycrystalline particles
  • Paste are typically applied to a clean cloth by rotating the platen at approximately 50rpm and by placing the syringe tip about 2in [5cm] out from the center of the platen.  Start dispensing the paste onto the cloth, resulting, in a spiral pattern
  • Require a lubricant such as MetaDi Fluid for most materials or Polishing Oil or AutoMet™ Lapping Oil for water sensitive materials
  • All Diamond pastes are nontoxic, noncombustible and environmentally safe

There are materials that simply do not respond to diamond polishing, regardless of cloth (Lead, CP Al, Indium). The use of diamond results in a poor surface finish with embedded abrasives. If you are preparing these materials or similar materials, choose an alternative abrasive, primarily Alumina.

Final Polishing Suspensions

Final polish solutions remove the final layer of surface deformation often invisible to the naked eye. Yet the removal of this deformation is essential when evaluating with high magnifications, polarized light, differential interference contrast as well as using EBSD techniques. A variety of application specific suspensions are available to provide superior performance.

Suspensions are typically applied using a dispensing system or directly from the bottle or a small container. New cloths should be charged with enough suspension to wet the cloth, providing enough lubrication during the polishing cycle. Cloths that have been in use previously should be charged with just enough new suspension to provide sufficient lubrication. Cease dispensing suspension the last 10-15 seconds of the polishing cycle, flushing the cloth surface with running water.

All final polishing suspensions are compatible with automated dispensing systems, such as the Burst Dispensing System, and the VibroMet™ 2 Vibratory Polisher.

This information has been sourced, reviewed and adapted from materials provided by Buehler.

For more information on this source, please visit Buehler.

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