Stainless steel parts are often heat treated to anneal (harden) the metal and relieve stress in the parts. While most stainless steels are resistant to oxidation at low temperatures, the various metal in the steel formulation (iron, chromium, molybdenum, etc.) can form oxides at higher temperatures. This oxidation causes the discoloration often seen on steel after heat treatments.
The knife blade picture above was heat treated to create a harder, more durable product. The part on the left shows the telltale blue, green and black discoloration due to elevated temperatures. Prior to further processing such as polishing and sharpening, the blade needs to be restored to it’s original surface finish and coloration.
The part on the right was abrasive blasted with a Medium Glass Bead at 80 psi to result in a satin-like, smooth surface finish. This part is now ready for the next step in the process.