The authoritative public forum
  for Metal Finishing since 1989
-----

Inclusions and polishing defects

2003

Hello,

There are many black points ,which are like inclusions, on the surface of my steel samples after grinding and polishing (but I am sure they aren't inclusion);this makes inclusions evaluation difficult. Why have they been generated and how can I prevent this phenomenon?

Thanks,

Megh Dar
Rayaneh - Pir, Isf, Iran

Hello Megh Dar!

What material are you polishing? If it is one that is full of second phase particles, such as a bearing grade steel; or one that is full of porosity, such as a P/M bronze, then there is an obvious reason for the black points. It could also be that you are polishing a very soft material, such as a lead alloy, and the black points are small bits of polishing compound that have been imbedded in the sample. That is often dealt with by another polishing step, using finer polish, and less time / pressure.

Good luck!

Lee Gearhart
metallurgist - E. Aurora, New York
2003