Stainless Steel 630

17-4 PH

Structural Steel

42CrM04 - HB 217 - HR 280 - HV 290

Chromium-molybdenum alloy steel 42CrMo4 (AISI 4140 in the US) is a strong and durable steel that meets European requirements. Additionally, it has good wear resistance and hardness, both of which can be further improved by heat treatment techniques including quenching and tempering. 42CrMo4 steel is widely used in automotive, aerospace, oil and gas, heavy machinery, and power generation industries for manufacturing critical components like gears, shafts, and axles due to its high strength, toughness, and good hardenability.

 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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RECOMMENDED

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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RECOMMENDED

In the grinding steps for Structural Steel 42CrM04, when dealing with a flat sample, the process commences with a 40 µm. In case the sample is not flat, a coarser grit should be initially employed to achieve a flat surface (54 µm).

It's important to note that the applied force during grinding depends on the diameter of the sample, and in this instance, the sample has a diameter of 30mm. Additionally, to prevent excessive damage to the sample, it is recommended to rotate the sample clockwise. 

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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In the polishing steps for Construction Steel 42CrM04, the process initiates with a 9 µm abrasive.

Subsequently, following the 9 µm, a 2 µm abrasive is employed. The applied force during polishing is contingent on the diameter of the sample, with the current sample having a diameter of 30mm. During the 9 µm abrasive phase, it is recommended to rotate the sample in a counter-clockwise direction to eliminate scratches from coarser grits.

Conversely, for the 2 µm abrasive, a clockwise rotation is advised to prevent excessive damage to the sample. It is crucial that all scratches align in the same direction, and if not, repeating the preceding step becomes necessary.

 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 Structural Steel 42CrM04 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.