SPECIMEN PREPARATION

• Cutting and Rough Grinding
• Cutting and rough grinding is performed to obtain a representative metallographic specimen from the component.
• The orientations are longitudinal and transverse.
• Mounting and Fine Grinding
• Mounting is performed in a mounting press, which encapsulates the specimen with a thermosetting resin under pressure and at an elevated temperature.
• Four-stage manual fine grinding: a successive series of water-lubricated papers (beginning with 240 grit and finishing with 600 grit) is used.
• The mounted specimen is abraded backward and forward without rotation until all grinding marks from the previous coarser abrasive paper have been eliminated.
• The direction of grinding is changed 90 degree with each change of abrasive paper, so that removal of the previous grinding marks is easily observed.
• Rough and Final Polishing
• Rough polishing is performed on a series of rotating wheels covered with a low-nap cloth. Succesively finer grades of polishing powders are applied to each wheel, starting at 45 micron size and then decreasing to 30 micron, 6 micron, and 1 micron. A small amount of lubricant is applied to the cloth to prevent overheating of the mount.
• In final polishing, a 0.3 micron to 0.05 micron alumina slurry in water is applied to a medium-nap cloth.
• The vibratory polishing machine named SYNTRAN is used for final polishing in our case.