Stainless steel 316L

80 HRB HB 149 HV 155

Stainless Steel 316L, also referred to as marine grade stainless steel, is a low carbon variation of Stainless Steel 316 that is highly praised for its increased toughness and greater corrosion resistance. Compared to ordinary 316, it has a composition of 16–18% chromium, 10–14% nickel and 2-3% molybdenum, with a carbon level of usually no more than 0.03%. Stainless Steel 316L is widely used in many industries and is vital in applications ranging from chemical processing equipment and architectural elements to medical devices and maritime environments. It is especially important in conditions where corrosive elements are present and endurance is important.

 STEP 1: CUTTING THE WORKPIECE 

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Wet abrasive cutting stands out as the most suitable method for materialographic cutting due to its minimal impact on the specimen in relation to the processing time. This technique involves the use of a cut-off wheel comprising abrasive particles and a binder.

DURING THE PROCEDURE

• The sample should accurately reflect the characteristics of the original piece or component from which it is derived

• The cut-off wheel should experience minimal wear and tear

• The cut-off wheel should not face obstruction during the cutting process

• There should be no occurrence of thermal damage or burning on the surface of the specimen

• The specimen should be cool to the touch upon extraction from the machine

• The presence of burrs should be minimized

• The resulting surface should exhibit a uniform and smooth appearance with consistent scratches

 STEP 2: MOUNTING 

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We recommend you to mount your samples the most convenient way, giving attention to the heat resistance of the sample material, although, if a mounting press is unavailable, cold mounting becomes the sole viable option. Conversely, with access to a mounting press, the selection of mounting material can be refined based on specific attributes.

A crucial factor to consider is the abrasion rate, which denotes the speed at which material is ground or polished away. Ideally, the chosen mounting material should closely match the abrasion rate of the sample material. It is essential to recognize that the abrasion rate differs from the hardness of the sample.

As for the resin needs, we recommend the use of Epoxy resin as Epoxies offer a robust mounting solution with high resistance to chemicals and abrasion. Although they typically require a longer setup time compared to other castable materials, they exhibit superior flow and minimal shrinkage properties. For mounting challenging samples, long-cure epoxies are employed, and they can be introduced into a vacuum environment to eliminate trapped air and address voids.

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If necessary, calibrate the sample with a coarser grit to make sure flat surface is achieved. The workpiece should be perfectly flat.

 STEP 3: PLANAR GRINDING AND LAPPING 

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When working with a flat sample, the grinding procedure for stainless steel 316L begins with 40µm abrasive. If the sample is not flat, you should start with a coarser grit in order to get a level surface. After using 54µm abrasive, the next stage is to use an 40µm abrasive.

It's crucial to remember that the diameter of the sample determines the amount of force that is used during grinding; in this case, the sample is 30 mm in diameter. Furthermore, rotating the sample clockwise is advised to avoid causing undue damage to it.

Pre-polishing is not neccessairy in this step for this material.

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 STEP 4: PRE-POLISHING AND POLISHING 

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The method of polishing stainless steel 316L begins with 9µm abrasive.

After that, a 2µm abrasive is used after the 9µm. The polishing force that is provided depends on the sample's diameter; the sample that is being used has a diameter of 30mm. To remove scratches from coarser grits, it is advised to spin the sample counterclockwise during the 9µm step..

On the other hand, it is recommended to rotate the 2µm in a clockwise direction to avoid causing undue harm to the sample. All of the scratches must line up in the same direction; otherwise, you will need to go back and redo the previous step.

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 STEP 5: FINAL POLISH 

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Finally, a suitable pad with a colloidal silica solution is utilized to clean and execute the last polishing step, providing a mirror-like finish to the stainless steel 316L sample.

Materialography

The term materialography used today is a factual extension of metallography, which include many other groups of materials, such as ceramics, plastics and composite materials that are examined in the same way.​ Materialography is the science of examining a material's microstructure, which is its internal composition at a microscopic level. By polishing and analyzing a material's surface, materialography helps engineers understand properties like strength, corrosion resistance, and potential failure points.