English: The most fragile part of a producing oil well, this high cobalt alloy was coated with ta-C on the right side to test the amount of increased resistance to the chemically aggressive and abrasive environment in which it would operate. Ball is 30 mm dia. Darker ring of DLC containing more graphitic phases bounds the area of the coating.
{{BotMoveToCommons|en.wikipedia|year={{subst:CURRENTYEAR}}|month={{subst:CURRENTMONTHNAME}}|day={{subst:CURRENTDAY}}}} {{Information |Description={{en|The most fragile part of a producing oil well, this high cobalt alloy was coated with ''ta-C'' on the r