Sectioning

The most versatile and economical sectioning method is abrasive cutting. A thin, rapidly rotating, consumable abrasive wheel produces high-quality, low-distortion cuts in times ranging from seconds to several minutes, depending on the material and the cross-sectional area. This technique is almost universally applicable. Important parameters in abrasive cutting are wheel composition, coolant condition, and technique. Abrasive wheels consist of abrasive grains (alumina, silicon carbide, boron nitride, diamond) bonded together with either resin or rubber or a rubber-resin combination, or metal. The abrasive grains become rapidly worn out during cutting of hard materials and must be continuously replaced by newly exposed grains. When cutting hard materials, a cutting wheel with a soft binder (soft cutting wheel) is chosen to promote a fast removal of used grains and the continuous exposure of new abrasive grains, thus always maintaining a sharp cutting edge. On the other hand, a cutting wheel with a hard binder (hard cutting wheel), is recommended for soft materials, since a fast exchange of abrasive particles is not necessary. Although soft cutting wheels are more rapidly consumed than hard cutting wheels, they are more suitable for harder materials, since their cutting action is considerably faster because of the renewed exposure of fresh abrasive grains. Other criteria for the selection of suitable abrasive wheels are the grain size and the concentration of the abrasive particles, as well as the thickness of the wheel. The concentration depends on the special cutting task and on the material to be sectioned, the binder, and the abrasive grain size. The abrasive concentration determines the removal rate and the durability of the abrasive wheel. A wheel with a high concentration and coarse abrasive particles is generally recommended for small areas of contact, while a cutting wheel with low concentration is typically used for large areas of contact. Depending on the type of material to be sectioned, cutting wheels of different compositions should be used, and their selection is dictated by hardness and ductility of the material to be cut

 Table A.1  Application of cutting wheels 

Materials Cutting wheel: abrasive/binder
Steel, ferrous materials, hardened steels Al2O3 (corundum)/bakelite
High-alloy steels Cubic boron nitride (CBN)/bakelite
Nonferrous metals, hard metals Silicon carbide (SiC)/bakelite
Hard and tough materials, cermets, ceramics Diamond/bakelite
Hard and brittle materials, ceramics, minerals Diamond/metal
   

lists some common materials and their appropriate cutting-wheel/binder combinations. Cutting wheel machines are available with high or low speed, with or without a feeding device, and even with precisely guided sample holders. The machines must always be equipped with a cooling system to prevent excessive heat that might affect the microstructure of the specimen; the coolant is ordinarily water, to which a corrosion inhibiting agent can be added.  

Our extensive metallographic sectioning consumables consisit of PRO CUT Premium Cut Off Wheels, Abrasive Cut Off Wheels, Precision Cut Off Wheels, Diamond Wafering Blades, Metal Bond - High Concentration, Metal Bond - Low Concentration, Resin Bonded, CBN Wafering Blades, Soluble Oil, Cutting Fluid, Dressing Sticks