Metallographic Analysis (theory)
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The document outlines the steps to prepare a metal specimen for microscopic analysis including cutting, mounting, grinding, polishing, etching, and observation. Specifically, it details how to cut the specimen, mount it in resin, grind it with progressively finer sandpaper, polish it using diamond suspensions, reveal microstructural details by etching, and finally observe the prepared specimen under a microscope. The overall goal is to prepare the metal sample so that its physical structure and components can be viewed and analyzed microscopically.
Metallographic Analysis (theory)
- 1. Khairol Ariffin Yadie Abdullah Wan Muhammad Firdaus Nurul Nurdiyana
- 2. Metallography is the study of the physical structure and components of metals ,typically using microscope.
- 4. Cut the welded specimen into 10 mm width using the band saw.
- 5. Switched on the power supply of the heat mounting machine. Set the air pressure at 6 – 7 atm. Bring up the lower ram by pressing the ram ‘Up’ button. Applied ‘Mould Release Agent’ to the surface of lower ram. Place the specimen on the top of the lower ram. The specimen must be clean, dry and free from dirt. The distance between the specimen and the cylinder wall must be minimum 3 mm to avoid cracks in the resin. Bring down the lower ram by pressing the ram ‘Down’ button. Filled a suitable amount of Bakelite powder (Phenolic powder) into the cylinder by means of the funnel. The powder level should be normally 10 – 12 mm above the specimen. Placed the lock nut and turns clockwise for closing. Do not apply excessive force. Bring up the lower ram. Stop the cycle. Pressed ram ‘Up’ button and open the lock nut and put your specimen. Switch off power supply.
- 7. Placed on the 240 silica paper on the plate of polishing machine. Switched the power supply and ‘On’ button at the back of the machine. Set the speed at 250 – 300 rev/ min only. Adjusted the water outlet. Applied the moulded specimen faced to the moving silica plate. Do not apply excessive force. Then, changed the 240 silica paper with 320, 400, 480, 560, 640, 720 and 800 silica papers for the next session.
- 9. Rinse and dry the sample before transitioning from sandpaper to diamond suspension. Start polishing using the cloth specialize for polishing. Spray about 4-5 sprays of the suspension onto the wheel. Firmly place the sample face down on the polishing wheel, moving your hand in clockwise circles. Check to see that the lines are even buffed out, and the surface appears shinier. This should take about 10 seconds. Rinse and dry the sample. The purpose of the polishing step is to remove the damage produced during cutting and planar grinding.
- 10. Dripped the etcher onto the silica paper (polishing machine). Applied the moulded specimen onto the moving silica paper. Washed the specimen by using water. Dripped the specimen into the ethanol for 15 seconds. Washed the specimen by using water and wiped with dry cloth. Metallographic etching is the process of revealing microstructural details that would otherwise not be evident on the as-polished sample.
- 11. Observe the specimen microstructure under the optical microscope. The example of specimen under the microscope Pearlite Cementite