Since the 1930s, Diamond abrasives have been an indispensable tool in metallographic sample preparation. Diamond is the hardest known material and can therefore polish the widest range of samples.
Buehler provides a wide range of diamond products to suit customer needs. But which product is right for you?
We provide products with polycrystalline diamond (Metadi® Ultra Diamond Paste and MetaDi® Supreme suspension) and monocrystalline diamond (MetaDi® II Paste and MetaDi® suspension). Which type is best? Polycrystalline diamonds are most often preferred, especially for ductile materials such as most metals. They have more cutting surfaces, resulting in a quicker polish with less deformation and the best surface finish. Monocrystalline diamonds are cheaper, but polish more slowly and with an inferior finish on ductile materials. They are best with very hard materials, although can be an option where wastage is expected or polishing time/quality is less of a concern.
Paste or Suspension
The material in which the diamond is carried is very important to polishing results. We provide diamonds carried in a water based suspension, wax pastes and oil. Water based suspensions such as MetaDi® Supreme Polycrystalline and MetaDi® Monocrystalline suspension are versatile, effective and easy to use. They contain a special formulation to ensure that the diamond stays in suspension, and provide excellent lubrication during polishing. They are used in most applications where embedding and water sensitivity are not a concern. Paste has a high concentration of diamond, and is excellent when used on a new cloth to ensure there is sufficient diamond and lubricity for the cloth to be working at 100% from the first moment. Polishing suspension can be used subsequently to replenish diamond and provide lubrication. If suspension alone is used on a previously unused cloth, extend polishing times by ~1 minute to allow the diamond concentration to build to an effective level.
Problems with embedding and water sensitivity
In very soft materials, Diamond in the water based suspension may become embedded. In these cases, paste is preferred as the wax carrier helps to keep the diamond fixed to the polishing cloth. Pastes should be used with a lubricating fluid – either water-based (Metadi Fluid) or Oil Based (Lapping Oil). Add just enough fluid to keep the polishing cloth damp for best results.
Oil-based suspensions are indispensable for the preparation of water sensitive materials and have great lubricity. Keep in mind that their polishing rates are slower and they make cleaning samples and equipment more difficult, so they are most often used only when necessary.
Many of Buehler’s diamond products are dyed based on abrasive size (e.g. red= 9 micron, green= 3 micron, blue= 1 micron). When used, they also color the cloth. This means that both the product and the cloth are color coded, which can prevent accidental contamination. We do offer dye free products for those who may have analyses that could be effected by the dye.