Metallography, the study of microstructures has been an invaluable tool to the progress of science and industry over the past three centuries. Metallography is one major valuable tool which can be precise for: Quality control for Material processing, Material product and hardware, to determine the reason for failure.
The various steps in Metallurgical sample preparation include sample selection, sectioning of sample, mounting and grinding, polishing and etching.
Sample selection is a very important first step. Grain size measurements are performed on transverse sections and general microstructure evaluations are performed on longitudinal sections. The orientation or the rolling direction of the sample is very important before sample preparation begins.
Cutting of sample is performed carefully to avoid altering or destroying the structure of the material. It is important to keep the sample cool with lubricant or coolant when using an abrasive cutter. Any deformation left on the sample surface must be removed as per subsequent sample preparation steps.
Mounting of sample is performed in plastic or epoxy material to facilitate handling during the grinding and polishing steps. Mounting media must be compatible with sample in terms of hardness and abrasion resistance.
Grinding of sample is done with a water lubricated abrasive wheel. This is required to remove the deformation of surface that occurred during sectioning a flat surface is required. The grinding procedure includes the use of a series of abrasive grits.
Polishing of sample removes the last thin layer of deformed metal for a smooth surface. The sample is ready for examination of the un-etched characteristics, such as any porosity or inclusion content that may exist.
Etching is the final step it could be used to bring out the microstructure of the sample. This step reveals features such as grain boundaries, twins and second phase particles that may not be seen in un-etched samples.