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Mechanical Preparation: Grinding
The True Microstructure- a requirement for microscopic investigation of the microstructure- elimination of the deformation layer- protecting the microstructure from induced featuresGrinding
Mechanical preparation is the most usual procedure to prepare samples for microscopic evaluation. The goal of sample preparation is to reveal the true structure of the material. The preparation should be accomplished systematically and according to reproducible methods.
The cutting process results in mechanical deformation below the sample surface. This deformation must be removed by subsequent preparation steps. The first grinding step is generally the planar grinding stage. With manual preparation, the sample should be turned 90 degrees after each stage. This is done until the grinding marks from the previous step are no longer visible. In the case of semi or fully automatic sample preparation, the change of direction results from the relative motion of the platen and the sample holder. When moving to the next step, the selection of the different abrasive size is very important.
As a rule the next step consists of a Silicon Carbide paper that has half the grit size of the proceeding one, e.g. in each case P120 - P320 - P600 - P1200.
After performing these steps correctly, the remaining surface deformation can be removed with a brief step using a fine diamond abrasive on soft plane cloths. With very soft or tough materials grades up to P2500 or P4000 should be used. Alternatively, grinding cloths can be used that utilise fine diamonds to achieve the grinding steps. The abrasion is moderate and the scratch pattern finer than with comparable Silicon Carbide paper.
Grinding usually takes place with Silicon Carbide papers on rotating discs with continuous water flushing. The wet grinding reduces frictional heat, dust formation and washes away abrasion debris. Buehler offers abrasives for all grinding procedures:
Choice of Abrasive
Buehler offers suitable abrasives for all grinding requirements:
The most common abrasive type in use for grinding most materials is Silicon Carbide paper. They are available in diameters of 200, 230, 250, 300 and 350 mm and in the grades of P60 to P4000, with and without adhesive backing. Adhesive sprays and films can be supplied if non-adhesive backed papers are used. PlanarMet planar grinding discs utilise Alumina abrasives, and ZirMet with Zirconia abrasives exhibit a higher hardness and a substantially better abrasion rate than Silicon Carbide paper. They are therefore particularly suitable for the planar grinding stage with semi and fully automatic preparation machines. Their longer life, in comparison to Silicon Carbide abrasive, reduces the number of papers used.
ULTRAPREP diamond discs are used for all materials with high to very high hardness. The long life of the surface allows savings of consumables even if a set of discs has a comparatively high initial price.
Instead of the classical grinding with fixed abrasive papers, grinding can also be performed with hard polishing surfaces (TexMet P or Ultra-cloths) and diamonds of 45 μm to 6 μm. This has the advantage that with semi and fully automatic preparation equipment, abrasives can be continuously dosed onto the cloth.
Grinding usually takes place with Silicon Carbide papers on rotating discs with continuous water flushing. The wet grinding reduces frictional heat, dust formation and washes away abrasion debris. Buehler offers abrasives for all grinding procedures:
Choice of Abrasive
Buehler offers suitable abrasives for all grinding requirements:
The most common abrasive type in use for grinding most materials is Silicon Carbide paper. They are available in diameters of 200, 230, 250, 300 and 350 mm and in the grades of P60 to P4000, with and without adhesive backing. Adhesive sprays and films can be supplied if non-adhesive backed papers are used. PlanarMet planar grinding discs utilise Alumina abrasives, and ZirMet with Zirconia abrasives exhibit a higher hardness and a substantially better abrasion rate than Silicon Carbide paper. They are therefore particularly suitable for the planar grinding stage with semi and fully automatic preparation machines. Their longer life, in comparison to Silicon Carbide abrasive, reduces the number of papers used.
ULTRAPREP diamond discs are used for all materials with high to very high hardness. The long life of the surface allows savings of consumables even if a set of discs has a comparatively high initial price.
Instead of the classical grinding with fixed abrasive papers, grinding can also be performed with hard polishing surfaces (TexMet P or Ultra-cloths) and diamonds of 45 μm to 6 μm. This has the advantage that with semi and fully automatic preparation equipment, abrasives can be continuously dosed onto the cloth.
