Table of Contents
- 1 What are the importance of doing metallographic specimen for examination by microscope?
- 2 What is the purpose of metallographic sample preparation treatments?
- 3 Why is it important to follow the rules of cleanliness in preparation of micro specimen?
- 4 Why must metallographic samples be washed and carefully dried?
- 5 Why etching is important in sample preparation?
- 6 Why is it necessary to wash the specimen after polishing?
- 7 What is the purpose of grinding and polishing the sample?
- 8 Why is etching important for metallographic samples?
- 9 What are the steps in preparing Metallographic specimens?
- 10 Why is my sample not polishing properly?
- 11 What type of cleaning is required after polishing the surface?
What are the importance of doing metallographic specimen for examination by microscope?
The metallographic examination of specimens allows the metallographer to observe and record the crystalline structures and to interpret from them the history of manufacture and use of the material. Metals and alloys often contain features other than grains.
What is the purpose of metallographic sample preparation treatments?
Proper preparation of metallographic specimens is a key step to determine the accurate microstructure of a material and often requires sectioning, mounting, course grinding, fine grinding, polishing, etching and microscopic examination.
Why are grinding and polishing required before the observation of a metallography?
Grinding is the first step of mechanical material removal. Proper grinding removes damaged or deformed surface material, while limiting the amount of additional surface deformation. The goal is a plane surface with minimal damage that can easily be removed during polishing in the shortest possible time.
Why is it important to follow the rules of cleanliness in preparation of micro specimen?
Cleaning and drying is perhaps the most underrated processing step in specimen preparation. Yet improper cleaning can lead to misleading results. Cleaning is required to remove polishing residue as well as particulates on the surface.
Why must metallographic samples be washed and carefully dried?
To avoid brining large particles to the finer grit or to remove all traces of polishing compound and oil before it is ready for examination with the metallurgical microscope.
Why is it necessary to wash the specimens immediately after etching?
After etching, the specimen should be thoroughly washed in water or alcohol and then dried using a hot air blower. The specimen should be carefully stored and cared for in a desiccator, to prevent oxidation and scratching.
Why etching is important in sample preparation?
Etching. Etching is used to reveal the microstructure of the metal through selective chemical attack. It also removes the thin, highly deformed layer introduced during grinding and polishing.
Why is it necessary to wash the specimen after polishing?
Following each grinding stage, the specimen should be cleaned with soap and running water to prevent carrying coarse abrasive particles to the next specimen. One large abrasive grain can ruin the surface of a finely ground and polished specimen.
What are the important steps metallographic sample preparation?
Proper preparation of metallographic specimens to determine microstructure and content requires that a rigid step-by-step process be followed. In sequence, the steps include sectioning, mounting, course grinding, fine grinding, polishing, etching and microscopic examination.
What is the purpose of grinding and polishing the sample?
GRINDING removes saw marks and levels and cleans the specimen surface. Polishing removes the artifacts of grinding but very little stock. Grinding uses fixed abrasives—the abrasive particles are bonded to the paper or platen—for fast stock removal.
Why is etching important for metallographic samples?
By etching with different chemicals, metallurgists can expose a variety of possible problems in metal samples. Etching can reveal tiny cracks, pores, or inclusions in metal samples. The information provided by etching allows metallurgists to discover why the metal failed.
Why it is necessary to mount the specimen before grinding and polishing?
Mounting of specimens is usually necessary to allow them to be handled easily. It also minimises the amount of damage likely to be caused to the specimen itself. The edges of the mounted specimen should be rounded to minimise the damage to grinding and polishing discs.
What are the steps in preparing Metallographic specimens?
Proper preparation of metallographic specimens to determine microstructure and content requires that a rigid step-by-step process be followed. In sequence, the steps include sectioning, mounting, course grinding, fine grinding, polishing, etching and microscopic examination.
Why is my sample not polishing properly?
Your sample may react w/ whatever abrasives were used to prepare it, or the coolant or water. This could cause the formation of oxidation or passivation layers that could affect polishing and etching characteristics. Samples being mounted in epoxy-like mounts will also benefit because of better adhesion to the material.
What is the best method for polishing metallographic samples?
In general there is no definite method for polishing metallographic samples. It is best to practice or have some basic training. Each sample may require a different approach depending on the material, size, finish required and machinery available.
What type of cleaning is required after polishing the surface?
Cleaning is required to remove polishing residue as well as particulates on the surface. Cleaning can be classified into two categories: Intermediate cleaning is important in order to minimize cross contaminaton of abrasives and swarf material. Intermediate cleaning is best accomplished with rinsing and ultrasonics.