THE MAIN CHARACTERISTICS OF STAINLESS STEEL

HIGH CORROSION STATIC RESISTANCE

METALLOGRAPHY STEEL STAINLESS METALLOGRAPHY

• Grain size is measured
• Analysis of the structure in general, including the martensite content, ferrite content, perlite content, or austenite content
• Identification of delta ferrite phases and sigma phases
• Distribution and assessment of carbides
• Welding Analysis

Metallography also plays a role in the failure analysis of metals to determine corrosion/oxidation mechanisms.

PREPARE STAINLESS METAL: GRINDING, POLISHING

Austenitic, but not ferritic, stainless steels can be ductile. Both are subject to deformation due to mechanical forces during metallographic processing of stainless.

The steels will become very reflective when they are polished to the final stage. The deformation of the steels may return after etching, if it is not thoroughly prepolished. Martensitic stainless steels can be easily polished due to the hardness of these materials. Carbides should be preserved.

OVERCOMING TROUBLES WHILE GRINDING & PULLING OFF STAINLESS STEEL

It is possible to have carbide and inclusions remain after polishing or grinding. In addition, ferritic and Austenitic Stainless Steels are susceptible to scratching and deformation.

The solution would be to use a diamond polishing process and complete the final polishing by using colloidal or alumina silica.

E-Polishing of STAINLESS Steels

As an alternative for microstructure testing or research, electrolytical cleaning and polishing stainless steel can be done. This method does not result in any mechanical distortion.

For checking stainless steel microstructure, electrolytic polished gives excellent results. The process is able to dissolve certain elements, like small carbides.

Prior to electrolytic Polishing, samples should be ground down to 500# or more on silicon carbide foil/paper. The results of electrolytic polishing are better when the initial surface is as fine as possible.

RECOMMENDATIONS IN GRINDING OR POLISHING STAINLESS-STEEL

• Avoid using high pressures or very coarse paper/foil for soft and ductile steels. Both can result into deep deformation.
• The finest grit is recommended for plane grinding. This should be consistent with both the area to be ground and the surface's roughness.



 
• Polishing
  • This is because any deformation that was not removed from the surface by fine grinding can leave its trace. These traces may be removed via final polishing. This is a lengthy process.
  • Diamond should be used to grind finely on a rigid Disc (MDLargo), on a cloth (MDPlan, or MDSat for certain types of stainless steels), and on a cloth ( MDSat as an alternate).
  • To remove fine scratches, use alumina (OP-A) or a data-cke saved-href="http://https://publications.struers.com/catalogue/consumables/english/?_ga=2.47427749.325532500.1565599163-105746660.1526629307&page=79">OP/a>. OP-S and alumina ( OP-A), to remove any fine scratches. This last step can be lengthy and requires a lot of attention. A good polishing job increases the chances for better contrast.

  • ETCHERING STAINLESS BRONZE

    Etching stainless requires experience and patience. There is an extensive literature available on etchants. To establish a personal stock of solutions suitable for the specific materials prepared regularly in your laboratory, we recommend you try out a range of etchants.
    
    The final oxide polishing will determine the quality of your etching. Discover how etching can be used to better visualize the macrostructure or microstructure of your samples. This is what you should do: .
    
    Following are some etchants proven to work in daily, routine applications.

    CHEMICAL ETCHERING

    Be sure to always adhere to the recommended safety precautions whenever you are working with chemical agents.