Metallurgical polishing

Sample Polishing

Course grinding is carried out to produce a flat surface in preparation for final grinding, this operation can be carried out using a wet linisher or rotary wet grinder to remove burs and improve the sample surface.

Fine grinding is carried out to remove deformation and damage introduced during the course grinding operation.  Sectioning damaged should be removed at the course grinding stage.  Using the correct sequence of grinding media / abrasive size will reduce and remove the degree and level of deformation to ensure the sample is suitable for first stage polishing.

First stage polishing produces minimal stock removal, so adequate fine grinding should be carried out to ensure the sample is ready for this important stage of preparation.  Proficient first stage polishing is carried out to remove most of the preparation damage prior to the final stage of polishing.

Final polishing is mainly a cosmetic procedure carried out to remove fine scratches left from the previous polishing stage. Any surface effect introduced at this stage should be removed by correct etching.

Deformation

The use of abrasives for sectioning and grinding will introduce a degree of permanent plastic deformation.  The extent of deformation is controlled and reduced by using the correct metallographic techniques. 

Deformation is a result of abrasive forces causing the material to exceed the plastic limit. The depth of deformation can be estimated by evaluation of material hardness and scratch depth being a consequence of the type and size of abrasive used.