Metallography is a process to find out everything about metal structure. Nowadays Materolgraphy is mostly preferred because of the huge number of composite materials that can be evaluated with this process. Metallography deploys its importance and implementation in damage analysis, research & development along with quality control. For metallography, you will need various equipment like cryostat and many more for sectioning purposes.

 

What is the work of metallography?

 

You can ask what is the work of metallography? The answer is – the work of metallography is finding out the material structure by microscopic and macro methods. We know that metals similarly show crystalline structure like the non-metallic crystals like quartz does. So for examining material and then coming to a satisfactory conclusion regarding its quality, polishing & grinding of sample is one of the vital steps to do in metallography. No unwanted fractures or scratches must appear in the material during the preparation process. The preparation usually takes place with only five steps. Look at the steps:

 

1) To cut-Off

 

This step involves sectioning where you need to cut off a section that is to be examined or tested through cut-off machines (Like wet abrasive cutters). The corresponding clamping tools help in clamping at strategic positions. If your specimen is big enough, you can mount and ground/polish it with the help of the holder.

 

2) To Mount

 

On the other hand, samples of small sizes need to be mounted first for improving the handling of edges. It takes place with the help of hot/cold mounting methods.

 

3) Polishing and Grinding

 

For making the crystal structure visible, the sample surface has to be ground initially and then polished. This method takes place by using a single unit. During the complete process, a cooling and lubricating fluid can be used for ensuring that the sample is cooled.

 

4) To etch

 

After finishing the polishing step, you can ascertain the material’s purity via different reflexions. For making the structure more visible, samples can undergo further preparation methods either with an electrolytic etching or manually per immersion. After the etching stage, the sample is washed in alcohol and later dried thoroughly under warm airflow.

 

5)By Using Microscope & evaluation

 

The crystalline structure contrasts accurately in the same manner then the sample can be easily evaluated.

 

Why is sectioning needed in metallography?

 

Among the metallographic procedures, the cutting and sectioning method is the most opted one. It is seen that most of the samples require to be sectioned for hassle-free handling. Ways of sectioning usually depend on the kind of material so that the user can differentiate abrasive cutter (Metals), diamond wafer cutting (For ceramics etc. All these mentioned procedures are used mostly for minimising the damage that can alter the material’s microstructure and also the analysis.

 

Metallographic cutting for precise & low-deformation sectioning

 

The methods for sampling materials for microscopic analysis are:

a) Wet abrasive cutting

b) Microtony (It is common for soft metals and polymers and can be done for thin sectioning)

c) with the help of band saws (It is a low-cost procedure)

 

Most of the industries as well as academia prefer wet abrasive cutting which is a machine-based method. It has very less impact on the structure of the material as compared to the other processes. In the metallographic field sampling, this method means mechanical segmentation of the components needs to be examined. For this process, you will need wheels of different structures, thicknesses & bonds on the cutter. Usually, they contain a rubber bond or phenolic resin where aluminium oxide/ silicon carbide is embedded.

 

Machines for metallographic cutting

 

In most of the metallographic sample preparation, abrasive cut-off machines are used majorly for the sectioning of the workpieces. One thing to remember is that optimum cooling is vital for sectioning results. Some common cooling media contain a mixture of amino acid & boric acid. Correct concentrate should be diluted with the water in a perfect ratio of 1:30. The instructions of the equipment manufacturer must be followed carefully and ensure complete cleanliness as it is the main priority in most metallographic sample preparation. All these can ensure accuracy and offer long-term service.

 

Follow the given guideline while performing sectioning in metallography:

a) The sectioning through wet abrasive cutter must have appropriate cooling as well as rotating disc

b) Optimum cooling must be ensured

c) A fitting rust protection agent has to be added to the coolant otherwise chances of surface oxidation may occur

d) The design & size of the cutter must depend on the size of the sample. It is vital for cutting capacity.

 

So you have to come to know about metallographic sectioning procedures. The metallographic sectioning or cutting mostly marks an important step of the metallographic sample preparation method. Evaluate the microstructure of material through the metallurgical sample preparation process.

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